0001193125-26-349173 | 10-Q | XBRL Viewer | 4D Molecular Therapeutics INC

Print Document

Fair Value Measurements and Marketable Securities - Additional Information (Details) - USD ($)	6 Months Ended
	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-Sale [Line Items]
Assets, Level 1 and Level 2 transfers	$ 0	$ 0
Liabilities, Level 1 and Level 2 transfers	0	0
Realized gains or losses on marketable securities	0
Maximum unrealized loss at individual instrument level	41,000
Other impairment charges related to marketable securities	0
Aggregate unrealized loss	516,000
Allowance for credit loss	0
Level 1
Debt Securities, Available-for-Sale [Line Items]
Liabilities	0	0
Level 2
Debt Securities, Available-for-Sale [Line Items]
Liabilities	0	0
Level 3
Debt Securities, Available-for-Sale [Line Items]
Assets	$ 0	$ 0
Maximum
Debt Securities, Available-for-Sale [Line Items]
Maturity period of marketable securities	2 years

Property and Equipment, Net (Tables)

6 Months Ended

Jun. 30, 2026

Property, Plant and Equipment [Abstract]

Schedule of Property and Equipment, Net

Property and equipment, net, consisted of the following (in thousands):


	June 30, 2026			December 31, 2025
Machinery and equipment	$	14,154		$	14,538
Leasehold improvements		18,467			18,467
Furniture and fixtures		1,067			1,086
Office equipment		301			324
Computer equipment and software		1,739			1,685
Transportation equipment		46			46
Construction in progress		49			—
Total property and equipment		35,823			36,146
Less: Accumulated depreciation and amortization		(23,444	)		(21,279	)
Property and equipment, net	$	12,379		$	14,867

Segment Information (Tables)

6 Months Ended

Jun. 30, 2026

Segment Reporting [Abstract]

Schedule Of Disaggregated Amounts That Comprise Research and Development Expenses

the following table provides disaggregated amounts that comprise research and development expenses (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Direct research and development expenses for 4D-150	$	43,557	$	19,134	$	86,280	$	31,907
Unallocated personnel costs (including stock-based compensation)		15,996		17,871		30,526		35,099
All other costs		8,729		10,946		16,456		21,644
Total research and development expenses	$	68,282	$	47,951	$	133,262	$	88,650

California Institute for Regenerative Medicine Award - Additional Information (Details) - California Institute for Regenerative Medicine - Alpha-1 Antitrypsin (AAT) Deficiency - USD ($) $ in Millions		3 Months Ended	6 Months Ended
	Apr. 12, 2026	Jun. 30, 2026	Jun. 30, 2026
Award From Regenerative Medicine Institute [Line Items]
Grant awarded	$ 5.9
Government grants cofunding commitment amount	1.4
Government grant reimbursement income		$ 3.1
Initial payment received from CIRM	$ 1.0
Deferred grant reimbursement income		4.0	$ 4.0
Research and Development
Award From Regenerative Medicine Institute [Line Items]
Government grant reimbursement income		$ 0.1	$ 0.1

Commitments and Contingencies - Summary of Maturities of Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
2026 (remaining six months)	$ 2,725
2027	5,350
2028	5,510
2029	5,675
2030	5,455
Total future minimum lease payments	24,715
Less: Amount representing interest	(5,085)
Present value of future minimum lease payments	19,630
Less: Current portion of operating lease liabilities	(5,374)	$ (5,592)
Long-term portion of operating lease liabilities	$ 14,256	$ 15,821

Related Party Transactions - Additional Information (Details) - Reignite Agreement $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2024 USD ($) Product	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)
Related Party Transaction [Line Items]
Research and development expenses		$ 300	$ 400	$ 700	$ 500
Option exercise fee		0		0
Option exercise fees per selected capsid	$ 1,000
Unpaid research and development expense		$ 100		$ 100
Maximum
Related Party Transaction [Line Items]
Related party expenses	1,500
Equipment costs	$ 60
Number of capsids \| Product	3
Option exercise fee	$ 3,000

Stock-based Compensation - Additional Information (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2026 shares	Jun. 30, 2025	Jun. 30, 2026 Period shares	Jun. 30, 2025	Mar. 18, 2026 shares	Jan. 01, 2026 shares	Dec. 31, 2025 shares	Feb. 28, 2025 shares	Feb. 03, 2025 shares	Dec. 31, 2020 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance	33,517,749		33,517,749				23,212,452
Number of options outstanding	11,737,148		11,737,148				9,412,808
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
2025 Employment Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance						1,000,000			500,000
Number of shares available for future grants	872,350		872,350
2020 Equity Incentive Award Plan \| Restricted Stock Units (RSU)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period			4 years
2020 Incentive Award Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance										2,606,546
Percentage of common stock outstanding increased annually for future issuance			5.00%
Number of shares available for future grants	1,735,472		1,735,472
Number of additional shares available for grant					2,880,394			2,289,625
2020 Incentive Award Plan \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options exercisable period			10 years
Number of shares authorized	18,000,000		18,000,000
2015 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock options exercisable period			10 years
Number of additional shares available for grant	0		0
Number of options outstanding	1,112,990		1,112,990
2020 ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares reserved for issuance	390,372		390,372				182,775			252,337
Increase in shares available for issuance percentage			1.00%
Number of additional shares available for grant					576,079			150,000
Employee purchase price of common stock as percentage of fair market value			85.00%
Common stock overlapping offering period			24 months
Number of duration purchase period \| Period			4
Percentage of maximum contributions of employee's eligible compensation	15.00%		15.00%
2020 ESPP \| Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares authorized	15,000,000		15,000,000

Accrued and Other Current Liabilities - Summary of Accrued and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Payables and Accruals [Abstract]
Payroll and related expenses	$ 7,818	$ 13,806
Accrued clinical and preclinical study costs	14,014	10,273
Consulting and outside services	3,475	2,666
Other accrued expenses	124	129
Total accrued and other current liabilities	$ 25,431	$ 26,874

Research and Collaboration Arrangements - Additional Information (Details) - Otsuka Pharmaceutical Co., Ltd - Collaboration and License Agreements - USD ($) $ in Millions	1 Months Ended	3 Months Ended	6 Months Ended	12 Months Ended
	Oct. 31, 2025	Jun. 30, 2026	Jun. 30, 2026	Dec. 31, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront cash payment	$ 85.0			$ 85.0
Eligible potential milestone payments	$ 335.5
Upfront payments received				$ 85.0
Unsatisfied or partially unsatisfied performance obligations		$ 33.4	$ 33.4
Revenue from clinical trials and other studies performance obligations		3.7	6.6
Estimated cost sharing and reimbursement amount due		$ 4.6	$ 4.6

Net Loss Per Share, Basic and Diluted - Outstanding Potentially Dilutive Securities Excluded From Computation of Diluted Net Loss Per Share (Details) - shares	6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	13,887,079	11,750,245
Stock Options Issued and Outstanding
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	11,737,148	10,445,483
Restricted Stock Units Subject to Future Vesting
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	1,816,742	725,101
2020 ESPP
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	303,189	549,661
Common Stock Warrants
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Antidilutive securities	30,000	30,000

Common Stock Warrants - Additional Information (Details) - USD ($)	1 Months Ended		3 Months Ended		6 Months Ended
	Dec. 31, 2020	May 31, 2018	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Equity [Abstract]
Number of warrant shares issued	30,000	23,669
Exercise price	$ 18	$ 3.19
Warrant expiration year	2027
Fair value of warrant shares			$ 0	$ 0	$ 0	$ 0
Warrant vesting period	4 years

Fair Value Measurements and Marketable Securities

6 Months Ended

Jun. 30, 2026

Fair Value Measurements and Marketable Securities [Abstract]

Fair Value Measurements and Marketable Securities

3. Fair Value Measurements and Marketable Securities

The following tables represent the Company’s fair value hierarchy for financial assets and financial liabilities measured at fair value on a recurring basis (in thousands):


	Amortized Cost Basis		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value as of June 30, 2026		Cash and Cash Equivalents		Current Marketable Securities		Non-Current Marketable Securities
Assets
Cash	$	29,718	$	—	$	—		$	29,718	$	29,718	$	—	$	—
Level 1:
Money market funds		34,659		—		—			34,659		34,659		—		—
Level 2:
Certificates of deposit		20,892		4		(9	)		20,887		—		20,887		—
Commercial paper		54,813		5		(52	)		54,766		5,995		48,771		—
U.S. Treasuries		92,469		10		(216	)		92,263		—		67,884		24,379
Corporate bonds		198,524		51		(239	)		198,336		—		153,420		44,916
Subtotal		366,698		70		(516	)		366,252		5,995		290,962		69,295
Total	$	431,075	$	70	$	(516	)	$	430,629	$	70,372	$	290,962	$	69,295


	Amortized Cost Basis		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value as of December 31, 2025		Cash and Cash Equivalents		Current Marketable Securities		Non-Current Marketable Securities
Assets
Cash	$	10,696	$	—	$	—		$	10,696	$	10,696	$	—	$	—
Level 1:
Money market funds		39,570		—		—			39,570		39,570		—		—
Level 2:
Certificates of deposit		35,986		37		—			36,023		—		36,023		—
Commercial paper		63,875		48		—			63,923		5,479		58,444		—
U.S. Treasuries		76,920		153		—			77,073		—		63,589		13,484
Corporate bonds		286,260		492		(3	)		286,749		4,496		184,358		97,895
Subtotal		463,041		730		(3	)		463,768		9,975		342,414		111,379
Total	$	513,307	$	730	$	(3	)	$	514,034	$	60,241	$	342,414	$	111,379

There are no Level 3 assets and no Level 1 or 2 liabilities.

Level 3 Inputs

The fair value of the derivative liability is based on significant inputs not observable in the market, which represent a Level 3 measurement within the fair value hierarchy. The fair value of the derivative liability was determined using a present value analysis with multiple scenarios. In determining the fair value of the derivative liability, the inputs impacting fair value include the change of control payment to the Cystic Fibrosis Foundation, the probability of a change of control event, the product status at time of a change of control event and the discount rate. See Note 6, Research and Collaboration Arrangements, and Note 16, Derivative Liability, for further discussion on the embedded derivative.

There were no transfers between Level 1, 2 and 3 for assets or liabilities during the periods presented.

The following table sets forth a summary of the changes in the fair value of the Company's Level 3 financial instrument (in thousands):


	Derivative Liability
Balance as of December 31, 2025	$	358
Change in fair value		26
Balance as of June 30, 2026	$	384

The change in fair value above is included in other income (expense), net, in the Company's condensed statements of operations.

All marketable securities held as of June 30, 2026 had contractual maturities of less than two years. There have been no material realized gains or losses on marketable securities for the periods presented.

Aggregate fair values of marketable securities with unrealized losses and gains were as follows as of June 30, 2026 and December 31, 2025 (in thousands):


	June 30, 2026		December 31, 2025
Aggregate fair value of marketable securities in a continuous loss position for less than twelve months	$	260,917	$	15,449
Aggregate fair value of marketable securities in a continuous loss position for more than twelve months		—		1,951
Aggregate fair value of marketable securities in unrealized gain position		105,335		446,368
Total marketable securities	$	366,252	$	463,768

The Company manages credit risk associated with its investment portfolio through its investment policy, which limits purchases to high-quality issuers and also limits the amount of its portfolio that can be invested in a single issuer. The Company did not record an allowance for credit losses or other impairment charges related to its marketable securities for any period presented. The Company has determined that (i) it does not have the intent to sell any of these investments, and (ii) it is not more likely than not that it will be required to sell any of these investments before recovery of the entire amortized cost basis. The Company further considered the maximum unrealized loss amounts both at the individual instrument level, $41 thousand, as well as in aggregate, $516 thousand, as of June 30, 2026, as immaterial. These unrealized losses were not attributed to credit risk and were associated with changes in market conditions. The Company periodically reviews its marketable securities for indications of credit losses. The Company anticipates that it will recover the entire amortized cost basis of such securities, and therefore, no credit loss existed as of June 30, 2026.

Condensed Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	ATM Offering Program	Common Stock	Common Stock ATM Offering Program	Additional Paid-in Capital	Additional Paid-in Capital ATM Offering Program	Accumulated Other Comprehensive Gain (Loss)	Accumulated Deficit
Stockholders' Equity, beginning balances at Dec. 31, 2024	$ 510,606		$ 5		$ 1,086,567		$ 229	$ (576,195)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2024			45,793,942
Issuance of common stock upon exercise of stock options and vesting of RSUs (in shares)			22,235
Issuance of common stock upon exercise of equity warrants (in shares)			508,465
Stock-based compensation expense	6,986				6,986
Net unrealized gain (loss) on marketable securities	103						103
Net loss	(47,972)							(47,972)
Stockholders' Equity, ending balances at Mar. 31, 2025	469,723		$ 5		1,093,553		332	(624,167)
Stockholders' Equity, ending balances (in shares) at Mar. 31, 2025			46,324,642
Stockholders' Equity, beginning balances at Dec. 31, 2024	510,606		$ 5		1,086,567		229	(576,195)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2024			45,793,942
Net unrealized gain (loss) on marketable securities	108
Net loss	(102,630)
Stockholders' Equity, ending balances at Jun. 30, 2025	420,890		$ 5		1,099,373		337	(678,825)
Stockholders' Equity, ending balances (in shares) at Jun. 30, 2025			46,700,242
Stockholders' Equity, beginning balances at Dec. 31, 2024	510,606		$ 5		1,086,567		229	(576,195)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2024			45,793,942
Stockholders' Equity, ending balances at Dec. 31, 2025	505,664		$ 6		1,221,235		727	(716,304)
Stockholders' Equity, ending balances (in shares) at Dec. 31, 2025			57,607,874
Stockholders' Equity, beginning balances at Mar. 31, 2025	469,723		$ 5		1,093,553		332	(624,167)
Stockholders' Equity, beginning balances (in shares) at Mar. 31, 2025			46,324,642
Issuance of common stock upon exercise of stock options and vesting of RSUs	2				2
Issuance of common stock upon exercise of stock options and vesting of RSUs (in shares)			49,791
Issuance of common stock - 2020 ESPP	860				860
Issuance of common stock - 2020 ESPP (in shares)			323,290
Issuance of common stock upon exercise of equity warrants (in shares)			2,519
Stock-based compensation expense	4,958				4,958
Net unrealized gain (loss) on marketable securities	5						5
Net loss	(54,658)							(54,658)
Stockholders' Equity, ending balances at Jun. 30, 2025	420,890		$ 5		1,099,373		337	(678,825)
Stockholders' Equity, ending balances (in shares) at Jun. 30, 2025			46,700,242
Stockholders' Equity, beginning balances at Dec. 31, 2025	505,664		$ 6		1,221,235		727	(716,304)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2025			57,607,874
Issuance of common stock upon exercise of stock options and vesting of RSUs	1,674				1,674
Issuance of common stock upon exercise of stock options and vesting of RSUs (in shares)			251,629
Issuance of common stock upon ATM offering, net of issuance costs		$ 9,712				$ 9,712
Issuance of common stock upon ATM offering, net of issuance costs (in shares)				1,012,145
Exchange of common stock for pre-funded warrants			$ (1)		1
Exchange of common stock for pre-funded warrants (in shares)			(6,600,000)
Stock-based compensation expense	4,453				4,453
Net unrealized gain (loss) on marketable securities	(907)						(907)
Net loss	(68,760)							(68,760)
Stockholders' Equity, ending balances at Mar. 31, 2026	451,836		$ 5		1,237,075		(180)	(785,064)
Stockholders' Equity, ending balances (in shares) at Mar. 31, 2026			52,271,648
Stockholders' Equity, beginning balances at Dec. 31, 2025	505,664		$ 6		1,221,235		727	(716,304)
Stockholders' Equity, beginning balances (in shares) at Dec. 31, 2025			57,607,874
Net unrealized gain (loss) on marketable securities	(1,173)
Net loss	(141,696)
Stockholders' Equity, ending balances at Jun. 30, 2026	407,659		$ 6		1,266,099		(446)	(858,000)
Stockholders' Equity, ending balances (in shares) at Jun. 30, 2026			55,214,097
Stockholders' Equity, beginning balances at Mar. 31, 2026	451,836		$ 5		1,237,075		(180)	(785,064)
Stockholders' Equity, beginning balances (in shares) at Mar. 31, 2026			52,271,648
Issuance of common stock upon exercise of stock options and vesting of RSUs	111				111
Issuance of common stock upon exercise of stock options and vesting of RSUs (in shares)			67,640
Issuance of common stock - 2020 ESPP	1,125				1,125
Issuance of common stock - 2020 ESPP (in shares)			368,482
Issuance of common stock upon ATM offering, net of issuance costs		$ 21,905		$ 1		$ 21,904
Issuance of common stock upon ATM offering, net of issuance costs (in shares)				2,506,327
Stock-based compensation expense	5,884				5,884
Net unrealized gain (loss) on marketable securities	(266)						(266)
Net loss	(72,936)							(72,936)
Stockholders' Equity, ending balances at Jun. 30, 2026	$ 407,659		$ 6		$ 1,266,099		$ (446)	$ (858,000)
Stockholders' Equity, ending balances (in shares) at Jun. 30, 2026			55,214,097

Condensed Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended		12 Months Ended
Condensed Statements of Cash Flows - USD ($) $ in Thousands	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Cash flows from operating activities
Net loss	$ (141,696)	$ (102,630)
Adjustments to reconcile net loss to net cash used in operating activities
Stock-based compensation expense	10,337	11,944
Change in fair value of derivative liability	26	(76)
Depreciation and amortization	2,549	2,217
Loss on disposal of property and equipment	43	0
Amortization of right-of-use assets	1,595	1,425
Net accretion of discount on marketable securities	(2,124)	(2,433)
Changes in operating assets and liabilities
Prepaid expenses and other current assets	(10,525)	(7)
Other non-current assets	(652)	(5,129)
Accounts payable	(525)	4,314
Accrued and other liabilities	2,421	798
Deferred revenue	2,210	(29)
Operating lease liabilities	(1,783)	(1,529)
Net cash used in operating activities	(138,124)	(91,135)
Cash flows from investing activities
Purchase of marketable securities	(95,555)	(249,480)
Maturities of marketable securities	190,042	268,273
Acquisition of property and equipment	(55)	(697)
Net cash provided by investing activities	94,432	18,096
Cash flows from financing activities
Issuance of common stock upon exercise of stock options	1,785	2
Issuance of common stock - 2020 ESPP	1,125	860
Proceeds from long-term debt, net of discount and issuance costs	19,259	0
Net cash provided by financing activities	53,823	862
Net increase (decrease) in cash and cash equivalents	10,131	(72,177)
Cash and cash equivalents, beginning of period	60,241	149,336	$ 149,336
Cash and cash equivalents, end of period	70,372	77,159	$ 60,241
Supplemental disclosures of noncash investing and financing information
Purchases of property and equipment in accrued and other current liabilities	49	0
Unpaid debt offering costs in accounts payable	1,888	0
Unpaid costs from ATM offering program in accrued and other current liabilities	37	0
ATM offering program
Cash flows from financing activities
Issuance of common stock under the ATM offering program, net of issuance costs	$ 31,654	$ 0

Summary of Significant Accounting Policies - Schedule of Concentration of Risk (Details) - Revenue - Customer Concentration Risk	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	98.00%	0.00%	97.00%	0.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage		100.00%		100.00%
Customer
Concentration Risk [Line Items]
Concentration risk, percentage	98.00%	100.00%	97.00%	100.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-20

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 18
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-18

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482836/275-10-55-18

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 20
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-20

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 954
-SubTopic 310
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478785/954-310-50-2

+ Details

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References + Details

The Company - Additional Information (Details) - USD ($)	1 Months Ended
	Nov. 30, 2025	Jun. 30, 2026	Dec. 31, 2025
Organization And Nature Of Business [Line Items]
Accumulated deficit		$ 858,000,000	$ 716,304,000
Common Stock \| 2025 Offering
Organization And Nature Of Business [Line Items]
Number of shares sold and issued	8,385,809
Stock sold and issued price per share	$ 10.51
Aggregate net proceeds, after deducting underwriting discounts and commissions and offering costs	$ 93,300,000
Common Stock \| 2025 Offering \| Pre-funded Warrants
Organization And Nature Of Business [Line Items]
Warrants to purchase shares of common stock	1,128,949
Common stock offering price	$ 10.5099
Maximum \| Hercules Loan Facility \| Hercules Capital, Inc
Organization And Nature Of Business [Line Items]
Aggregate principal amount of debt		$ 200,000,000

Related Party Transactions

6 Months Ended

Jun. 30, 2026

Related Party Transactions

18. Related Party Transactions

In March 2024, the Company entered into a research and option agreement (the “Reignite Agreement”) with Reignite Therapeutics Inc. (“Reignite”), which was founded by David Kirn, M.D., Chief Executive Officer of the Company. Reignite has the expertise to develop high-capacity, helper-dependent adenovirus capsids which the Company plans to utilize as it expands its therapeutic capsid evolution platform. Reignite and the Company plan to collaborate on a program to develop these high capacity, helper-dependent adenovirus capsids. Under the Reignite Agreement, the Company shall have the final authority to amend and make updates to the plan and budget of the program. Further, the Company is responsible for the funding of the related research which includes the budgeted full-time employees and CRO costs, equipment costs not to exceed $60 thousand and all other costs, in total not to exceed $1.5 million in any year of the program. The Company will have an option to acquire up to three capsids resulting from the program. The Company shall pay to Reignite an option exercise fee of $1.0 million per selected capsid for which the Company has exercised its option. The maximum total amount payable is $3.0 million.

During the three and six months ended June 30, 2026, the Company paid Reignite $0.3 million and $0.7 million, respectively, for research and development expenses. During the three and six months ended June 30, 2025, the Company paid Reignite $0.4 million and $0.5 million, respectively, for research and development expenses. As of June 30, 2026, the Company owes $0.1 million to Reignite for unpaid research and development expense. No option exercise fees were incurred during the three and six months ended June 30, 2026.

- Definition

The entire disclosure for related party transactions. Examples of related party transactions include transactions between (a) a parent company and its subsidiary; (b) subsidiaries of a common parent; (c) and entity and its principal owners; and (d) affiliates.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-5

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 235
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477968/946-235-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(e))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/850/tableOfContent

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-6

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

+ Details

Pre-funded Warrants

6 Months Ended

Jun. 30, 2026

Equity [Abstract]

Pre-funded Warrants

14. Pre-funded Warrants

In February 2024, the Company completed an underwritten public follow-on offering which included the sale of pre-funded warrants to purchase 3,583,476 shares of the Company’s common stock at an offering price of $29.4999 (the "February 2024 Warrants"). The Company valued the February 2024 Warrants at issuance and recorded net proceeds of $99.4 million, after deducting underwriters' fees, during the year ended December 31, 2024 related to the sale of the February 2024 Warrants. In February 2025, two holders of the February 2024 Warrants gave notice of exercise to purchase an aggregate of 508,476 shares of the Company’s common stock in a cashless exchange under the terms of the February 2024 Warrants.

In November and December 2024, the Company entered into exchange agreements (the “2024 Exchange Agreements”) with each of Biotechnology Value Fund, L.P. and certain of its affiliates (collectively, “BVF”) and RA Capital Healthcare Fund, L.P. (“RA Capital”), respectively. Pursuant to the 2024 Exchange Agreements, BVF and RA Capital exchanged 5,775,000 and 535,000 shares, respectively, of the Company’s common stock for pre-funded warrants to acquire the same respective number of shares of the Company’s common stock (the "2024 Exchange Warrants"). The fair value of the common stock exchanged approximated the fair value of the pre-funded warrants issued as of the transaction dates and no net proceeds were recorded in connection with the transactions. On December 22, 2025, BVF gave notice of exercise to purchase an aggregate of 178,280 shares of the Company’s common stock in a cashless exchange under the terms of the 2024 Exchange Warrants.

In November 2025, the Company completed the 2025 Offering which included the sale of pre-funded warrants to purchase 1,128,949 shares of the Company's common stock at an offering price of $10.5099 per underlying share (the "November 2025 Warrants"). The Company valued the November 2025 Warrants at issuance and recorded net proceeds of $11.2 million, after deducting underwriters fees, during the year ended December 31, 2025.

On January 22, 2026, the Company entered into exchange agreements with RA Capital and BVF, pursuant to which RA Capital and BVF exchanged 4,850,000 and 1,750,000 shares, respectively, of the Company’s common stock for pre-funded warrants to acquire the same respective number of shares of the Company’s common stock (together with the February 2024 Warrants, the 2024 Exchange Warrants, the November 2025 Warrants, collectively, the "Pre-funded Warrants"). The fair value of the common stock exchanged approximated the fair value of the pre-funded warrants issued as of the transaction dates and no net proceeds were recorded in connection with the transactions.

The Pre-funded Warrants each have an exercise price of $0.0001 per underlying share of common stock, are exercisable at any time until they are fully exercised and will not expire until they are fully exercised. The Pre-funded Warrants are classified as a component of stockholders’ equity within additional paid-in-capital. The number of shares of the Company’s common stock issuable upon exercise of each Pre-funded Warrant is subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting shares of the Company’s common stock, as well as upon any distribution of assets, including cash, stock or other property, to the Company’s stockholders.

Long Term Debt - Summary of Future Principal Payments due under Hercules Loan Facility (Details) - Hercules Loan Facility - Hercules Capital, Inc $ in Thousands	Jun. 30, 2026 USD ($)
Debt Instrument [Line Items]
Remainder of 2026	$ 0
2027	0
2028	594
2029	7,523
2030	8,230
Thereafter	4,953
Total	$ 21,300

Summary of Significant Accounting Policies - Schedule of Concentration of Risk (Details) (Parenthetical) - Revenue - Customer Concentration Risk [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Customer A
Concentration Risk [Line Items]
Concentration risk, percentage	98.00%	0.00%	97.00%	0.00%
Customer B
Concentration Risk [Line Items]
Concentration risk, percentage		100.00%		100.00%
Customer B \| Maximum
Concentration Risk [Line Items]
Concentration risk, percentage			10.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

- Definition

+ References + Details

Research and Collaboration Arrangements (Tables)

6 Months Ended

Jun. 30, 2026

Research And Collaboration Arrangements [Abstract]

Summary of Collaboration and License Revenue and Deferred Revenue

Collaboration and license revenue for each period was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Otsuka Pharmaceutical Co., Ltd.	$	3,691	$	—	$	6,648	$	—
Cystic Fibrosis Foundation		90		15		180		29
Total revenue	$	3,781	$	15	$	6,828	$	29

Deferred revenue is summarized as follows (in thousands):


	June 30, 2026		December 31, 2025
Otsuka Pharmaceutical Co., Ltd.	$	2,390	$	—
Cystic Fibrosis Foundation		925		1,105
Total deferred revenue	$	3,315	$	1,105

Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2026 USD ($) Financial_Institution Segment	Dec. 31, 2025
Summary Of Significant Accounting Policies [Line Items]
Number of reportable segments	1
Number of operating segments	1
Number of financial institutions cash is held \| Financial_Institution	2
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true
Change in Accounting Principle, Accounting Standards Update, Early Adoption [true false]	true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 01, 2026
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true
Accounting Standards Update [Extensible Enumeration]	Accounting Standards Update 2025-10 [Member]
Otsuka Pharmaceutical Co., Ltd \| Collaboration and License Agreements
Summary Of Significant Accounting Policies [Line Items]
Estimated cost sharing and reimbursement amount due \| $	$ 4.6
Accounts Receivable \| Credit Concentration Risk \| Customer
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage	0.00%	0.00%

Long Term Debt (Tables)

6 Months Ended

Jun. 30, 2026

Debt Disclosure [Abstract]

Summary of Future Principal Payments due under Hercules Loan Facility

The future principal payments due under the Loan and Security Agreement as of June 30, 2026 were as follows (in thousands):


Remainder of 2026	$	—
2027		—
2028		594
2029		7,523
2030		8,230
Thereafter		4,953
Total	$	21,300

Summary of Carrying Value of Hercules Loan Facility

As of June 30, 2026, the carrying value of the Loan and Security Agreement was as follows (in thousands):


Principal outstanding	$	20,000
Less: unamortized discount and debt issuance costs		(413	)
Long-term debt, net	$	19,587

Fair Value Measurements and Marketable Securities - Summary of Aggregate fair values of marketable securities with unrealized losses and gains (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Debt Securities, Available-for-Sale [Line Items]
Aggregate fair value of marketable securities in a continuous loss position for less than twelve months	$ 260,917	$ 15,449
Aggregate fair value of marketable securities in a continuous loss position for more than twelve months	0	1,951
Aggregate fair value of marketable securities in unrealized gain position	105,335	446,368
Total marketable securities	$ 366,252	$ 463,768

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

License Arrangements - Additional Information (Details) - USD ($)		1 Months Ended
	Apr. 21, 2023	Jan. 31, 2019	Jan. 31, 2016	Jun. 30, 2026	Dec. 31, 2018
Aevitas Therapeutics, Inc. Agreement
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential cash payment for development milestones	$ 7,200,000
Potential cash payment for regulatory milestones	68,000,000
Potential cash payment for sales milestones	68,900,000
Upfront consideration payment	0
Liability related to contingent consideration				$ 0
Aevitas Therapeutics, Inc. Agreement \| Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential cash payment upon achievement of certain late-stage milestones	144,100,000
License Agreement for sCFH with University of Pennsylvania
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential cash payment for development milestones	1,900,000
Potential cash payment for regulatory milestones	21,500,000
Potential cash payment for sales milestones	18,200,000
License Agreement for sCFH with University of Pennsylvania \| Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Potential cash payment upon achievement of certain late-stage milestones	$ 41,600,000
UC Agreements
Research And Development Arrangement Contract To Perform For Others [Line Items]
Liability related to contingent consideration				$ 0
Non-refundable license fee payable upon execution					$ 5,000
Non-refundable license fee payable upon execution every year thereafter until sales of a licensed product and payment of royalties					5,000
Amount obligated to pay upon closing first qualified financing at option of UC Regents					$ 50,000
Percentage of equity interest upon closing of first qualified financing at option of UC Regents					3.00%
Percentage of equity interests issued as common stock			6.00%
Amount paid non-refundable license fee		$ 50,000
Non-refundable license fee payable annually		5,000
UC Agreements \| Maximum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Contingent payments development milestones		3,100,000
UC Agreements \| Minimum
Research And Development Arrangement Contract To Perform For Others [Line Items]
Annual royalty		$ 100,000

Property and Equipment, Net

6 Months Ended

Jun. 30, 2026

Property, Plant and Equipment [Abstract]

Property and Equipment, Net

4. Property and Equipment, Net

Property and equipment, net, consisted of the following (in thousands):


	June 30, 2026			December 31, 2025
Machinery and equipment	$	14,154		$	14,538
Leasehold improvements		18,467			18,467
Furniture and fixtures		1,067			1,086
Office equipment		301			324
Computer equipment and software		1,739			1,685
Transportation equipment		46			46
Construction in progress		49			—
Total property and equipment		35,823			36,146
Less: Accumulated depreciation and amortization		(23,444	)		(21,279	)
Property and equipment, net	$	12,379		$	14,867

All property and equipment are maintained in the United States. Depreciation expense was $1.3 million for each of the three months ended June 30, 2026 and 2025, and $2.5 million and $2.6 million for the six months ended June 30, 2026 and 2025, respectively.

Commitments and Contingencies - Summary of Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Commitments and Contingencies Disclosure [Abstract]
Operating lease cost	$ 1,344	$ 1,344	$ 2,688	$ 2,688
Variable lease cost	678	648	1,355	1,422
Total	$ 2,022	$ 1,992	$ 4,043	$ 4,110

Property and Equipment, Net - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Property, Plant and Equipment [Abstract]
Depreciation expense	$ 1.3	$ 1.3	$ 2.5	$ 2.6

Common Stock Warrants

6 Months Ended

Jun. 30, 2026

Equity [Abstract]

Common Stock Warrants

13. Common Stock Warrants

In May 2018, the Company issued a warrant for 23,669 shares of the Company’s common stock to a service provider with an exercise price of $3.19 per share. The fair value of the warrant was determined at the issuance date using the Black-Scholes option pricing model. The warrant was fully vested upon issuance and was exercised in May 2025 through a cashless exchange under the terms of the original agreement.

In December 2020, the Company issued a warrant for 30,000 shares of the Company’s common stock to a service provider with an exercise price of $18.00 per share. This warrant vests over a period of four years and expires in 2027. The fair value of the warrant was determined at the issuance date using the Black-Scholes option pricing model.

The Company recognized no expense related to the above warrant shares during the three and six months ended June 30, 2026 and 2025.

The Company

6 Months Ended

Jun. 30, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The Company

1. The Company

4D Molecular Therapeutics, Inc. (the “Company”) was formed as a limited liability company in September 2013 under the name 4D Molecular Therapeutics, LLC. The Company changed its name and converted into a corporation which was incorporated in the state of Delaware in March 2015. The Company is a late-stage biotechnology company advancing durable and disease-targeted therapeutics with potential to transform treatment paradigms and provide benefits to patients.

2025 Offering

In November 2025, the Company completed an underwritten offering (the “2025 Offering”) in which 8,385,809 shares of the Company’s common stock were sold at an offering price of $10.51 per share, as well as pre-funded warrants to purchase 1,128,949 shares of the Company’s common stock at an offering price of $10.5099 per underlying share pursuant to an effective Registration Statement on Form S-3. The net proceeds from the 2025 Offering were approximately $93.3 million, after deducting the underwriting discounts and commissions and other offering expenses.

Liquidity

The Company has incurred significant losses and negative cash flows from operations and had an accumulated deficit of $858.0 million as of June 30, 2026. The Company believes that its cash, cash equivalents and marketable securities as of June 30, 2026 are sufficient for the Company to fund planned operations for at least one year from the issuance date of these condensed financial statements. The Company has funded its operations primarily through the sale and issuance of equity securities, including primary follow-on offerings and use of the Company's "at-the-market" offering program, from borrowings under the Company’s $200.0 million loan facility (the “Loan and Security Agreement”) with Hercules Capital, Inc. (“Hercules”) (see Note 9, Long-Term Debt) and, to a lesser extent, from cash received pursuant to its collaboration and license agreements. To date, none of the Company’s product candidates have been approved for sale, and therefore, the Company has not generated any revenue from product sales. Management expects operating losses and negative cash flows from operations to continue for the foreseeable future. The Company plans to raise additional funding as required based on the status of its clinical trials and projected cash flows. There can be no assurance that, in the event the Company requires additional financing, such financing will be available on terms acceptable to the Company, if at all. Failure to generate sufficient cash flows from operations, raise additional capital and reduce discretionary spending should additional capital not become available could have a material adverse effect on the Company’s ability to achieve its business objectives.

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Jun. 30, 2026
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Income Taxes

6 Months Ended

Jun. 30, 2026

Income Tax Disclosure [Abstract]

Income Taxes

10. Income Taxes

For the three and six months ended June 30, 2026 and 2025, the Company did not record a federal or state income tax provision due to its recurring net losses. In addition, the Company has taken a full valuation allowance against its net deferred tax assets as the Company believes it is not more likely than not that the benefit will be realized.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477617/942-740-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 740
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478822/944-740-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12C

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.5.Q1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480990/946-20-50-13

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/740/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-14

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-21

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 17
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-17

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482603/740-30-50-2

+ Details

Net Loss Per Share, Basic and Diluted

6 Months Ended

Jun. 30, 2026

Earnings Per Share [Abstract]

Net Loss Per Share, Basic and Diluted

15. Net Loss Per Share, Basic and Diluted

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data):


	Three Months Ended June 30,						Six Months Ended June 30,
	2026			2025			2026			2025
Numerator
Net loss	$	(72,936	)	$	(54,658	)	$	(141,696	)	$	(102,630	)
Denominator
Weighted-average shares outstanding used in computing net loss per share, basic and diluted		70,272,018			55,927,091			69,175,213			55,836,075
Net loss per share, basic and diluted	$	(1.04	)	$	(0.98	)	$	(2.05	)	$	(1.84	)

The Company has issued and sold Pre-funded Warrants to purchase shares of common stock at a nominal exercise price of $0.0001 (see Note 14, Pre-funded Warrants). The Pre-funded Warrants have an exercise price of $0.0001 per underlying share of common stock of the Company. The shares of common stock into which the Pre-funded Warrants may be exercised are considered outstanding for the purposes of computing earnings per share, because the shares may be issued for little or no consideration, they are fully vested and the Pre-funded Warrants are immediately exercisable upon their issuance date.

The following outstanding shares of potentially dilutive securities were excluded from the computation of diluted net loss per share for the periods presented because including them would have been antidilutive:


	June 30,
	2026		2025
Stock options issued and outstanding		11,737,148		10,445,483
Restricted stock units subject to future vesting		1,816,742		725,101
2020 ESPP		303,189		549,661
Common stock warrants		30,000		30,000
Total		13,887,079		11,750,245

Property and Equipment, Net - Schedule of Property and Equipment, Net (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Property Plant And Equipment [Line Items]
Total property and equipment	$ 35,823	$ 36,146
Less: Accumulated depreciation and amortization	(23,444)	(21,279)
Property and equipment, net	12,379	14,867
Machinery and Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	14,154	14,538
Leasehold Improvements
Property Plant And Equipment [Line Items]
Total property and equipment	18,467	18,467
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Total property and equipment	1,067	1,086
Office Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	301	324
Computer Equipment and Software
Property Plant And Equipment [Line Items]
Total property and equipment	1,739	1,685
Transportation Equipment
Property Plant And Equipment [Line Items]
Total property and equipment	46	46
Construction in Progress
Property Plant And Equipment [Line Items]
Total property and equipment	$ 49	$ 0

Summary of Significant Accounting Policies

6 Months Ended

Jun. 30, 2026

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The accompanying condensed financial statements have been prepared in accordance with United States Generally Accepted Accounting Principles (“U.S. GAAP”) and the rules and regulations of the United States Securities and Exchange Commission (“SEC”) for interim reporting.

Certain information and note disclosures normally included in annual financial statements prepared in accordance with U.S. GAAP have been condensed or omitted. Accordingly, the condensed financial statements should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025, filed with the SEC.

The accompanying financial information for the three and six months ended June 30, 2026 and 2025 is unaudited. The condensed financial statements have been prepared on the same basis as the annual audited financial statements and, in the opinion of management, reflect all adjustments, consisting of only normal recurring adjustments, necessary for a fair statement of the Company’s financial position as of June 30, 2026, and its results of operations and cash flows for the three and six months ended June 30, 2026 and 2025. The condensed balance sheet at December 31, 2025 was derived from audited annual financial statements but does not contain all of the footnote disclosures from the annual financial statements. The results for interim periods are not necessarily indicative of the results expected for the full fiscal year or any other periods.

Use of Estimates and Judgments

The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the reported amounts of assets, liabilities, revenue and expenses; and disclosure of contingent assets and liabilities as of the date of the financial statements. Such estimates include the determination of useful lives for property and equipment, the contract term, transaction price and costs of collaboration agreements, stock options, the derivative instrument, long-term debt and income tax uncertainties. Actual results could differ from those estimates.

Due to the war in Ukraine, conflicts in the Middle East, any expansion of these conflicts, rising interest rates, tariffs and inflation, natural disasters and health crises, such as pandemics, there has been uncertainty and disruption in the global economy and financial markets. The Company is not aware of any specific event or circumstance that would require an update to its estimates or judgments or a revision of the carrying value of its assets or liabilities as of June 30, 2026. While there was not a material impact to the Company’s condensed financial statements as of June 30, 2026, these estimates may change, as new events occur and additional information is obtained, as well as other factors that could result in material impacts to the condensed financial statements in future reporting periods.

Long-Term Debt

Long-term debt is recognized at cost and presented net of the original issue discount or premium and debt issuance costs on the condensed balance sheets. Amortization of debt discount and debt issuance costs is recognized as interest expense over the period of the debt, using the effective interest rate method. See Note 9, Long-Term Debt, for further discussion on the long-term debt.

Segment Information

The Company manages its business as one segment which includes all activities related to the discovery, development, and commercialization of medicines for specific diseases. See Note 20, Segment Information, for financial information related to the Company's one segment.

Concentration of Credit Risk

Financial instruments that potentially subject the Company to a concentration of credit risk consist of cash and cash equivalents, marketable securities and accounts receivable. The Company’s cash is held at two financial institutions in the United States of America. The Company’s cash equivalents are invested in money market funds. The Company also invests in U.S. Treasuries, U.S. government sponsored agencies, commercial paper, corporate bonds and certificates of deposit. The Company has not experienced any losses on its deposits of cash and cash equivalents. Such deposits may, at times, exceed federally insured limits.

The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total revenue are as follows:


	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2026	2025	2026	2025
Customer A	98%	0%	97%	0%
Customer B	*	100%	*	100%
Total	98%	100%	97%	100%

______________

* Less than 10%

As of June 30, 2026, the Company had $4.6 million due from Otsuka Pharmaceutical Co., Ltd. (“Otsuka”) related to the estimated cost sharing and reimbursement. The Company did not have accounts receivable from its other partner in collaboration and license agreements as of June 30, 2026 and December 31, 2025.

The Company’s total revenues by geographic region, based on the location of the customer, are as follows (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2026		2025		2026		2025
Japan	$	3,691	$	—	$	6,648	$	—
United States		90		15		180		29
Total revenue	$	3,781	$	15	$	6,828	$	29

Other Risks and Uncertainties

The Company is subject to risks and uncertainties common to late clinical-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, protection of proprietary technology, dependence on key personnel, suppliers for key raw materials, contract development and manufacturing organizations (“CDMOs”) and contract research organizations (“CROs”), compliance with government regulations and the need to obtain additional financing to fund operations. Product candidates currently under development will require significant additional research and development efforts, including extensive preclinical studies, clinical trials and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel and infrastructure and extensive compliance and reporting.

There can be no assurance that the Company’s research and development will be successfully completed, that adequate protection for the Company’s intellectual property will be obtained or maintained, that any products developed will obtain necessary government regulatory approval or that any approved products will be commercially viable. Even if the Company’s product development efforts are successful, it is uncertain when, if ever, the Company will generate significant revenue from product sales. The Company operates in an environment of rapid change in technology and substantial competition from other pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees, consultants and other third parties (including for clinical trials and some aspects of research and preclinical testing).

Recently Issued Accounting Pronouncements Not Yet Adopted

In November 2024, the Financial Accounting Standards Board issued Accounting Standards Update ("ASU") No. 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Topic 220) - Disaggregation of Income Statement Expenses. ASU 2024-03 requires public business entities to disclose, on an annual and interim basis, disaggregated information about certain income statement expense line items in the notes to the financial statements. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026 (fiscal 2027) and interim periods within fiscal years beginning after December 15, 2027 (fiscal 2028). The ASU must be applied prospectively and may be applied retrospectively if elected. The Company is currently evaluating the effect of adopting this new accounting guidance.

Recently Issued Accounting Pronouncements Adopted

In December 2025, the FASB issued ASU 2025-10, Government Grants (Topic 832): Accounting for Government Grants Received by Business Entities, which establishes authoritative guidance on the recognition, measurement, presentation and disclosure of government grants received by business entities. The guidance applies to grants related to assets and grants related to income and requires recognition when it is probable that the Company will comply with the conditions attached to the grant and the grant will be received. The guidance also permits either modified prospective, modified retrospective or retrospective transition and is effective for annual and interim periods beginning after December 15, 2028, with early adoption permitted. The Company early adopted ASU 2025-10 as of the beginning of the current fiscal year using the modified prospective approach. The adoption did not have an impact on the Company’s condensed financial statements or related disclosures.

Condensed Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2026	Dec. 31, 2025
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.0001	$ 0.0001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares, issued	55,214,097	57,607,874
Common stock, shares, outstanding	55,214,097	57,607,874

Commitments and Contingencies - Additional Information (Details)		1 Months Ended	6 Months Ended
	Jan. 01, 2024 ft²	Jul. 31, 2024 USD ($) ft²	Jun. 30, 2026 USD ($)	Jun. 30, 2025 USD ($)	Dec. 31, 2025 USD ($)	Oct. 31, 2018 ft²
Commitment And Contingencies [Line Items]
Operating lease right-of-use ("ROU") assets			$ 16,548,000		$ 18,143,000
Operating lease liability			19,630,000
Increase in lease liability			(1,783,000)	$ (1,529,000)
Cash used in operating activities			2,900,000	$ 2,800,000
Non-cancellable purchase obligations			$ 4,900,000		4,000,000
5980 Horton Street Building Lease
Commitment And Contingencies [Line Items]
Amended lease expiry date			August 2026
Operating lease right-of-use ("ROU") assets			$ 100,000		300,000
Operating lease liability			100,000		400,000
5858 Horton Street Lease and 2018 Expansion
Commitment And Contingencies [Line Items]
Lease renewal term		12 months
Lease extended term date		Dec. 31, 2030
Incremental borrowing rate		10.75%
Increase in lease liability		$ 800,000
Increase in right-of-use asset		800,000
Gain or loss on increase in carrying value of right of use asset		$ 0
5858 Horton Lease
Commitment And Contingencies [Line Items]
Operating lease right-of-use ("ROU") assets			8,100,000		8,800,000
Operating lease liability			10,400,000		11,200,000
5858 Horton Street Lease
Commitment And Contingencies [Line Items]
Area of office and warehouse space \| ft²						40,802
5858 Horton Street Lease and 2024 Expansion
Commitment And Contingencies [Line Items]
Operating lease right-of-use ("ROU") assets			7,200,000		7,800,000
Operating lease liability			8,000,000		8,600,000
Area of office and warehouse space \| ft²		32,038
Lease extended term date		Dec. 31, 2030
Lease commencement date		Sep. 01, 2024
Operating lease, discount rate		11.02%
Warehouse Lease Agreement
Commitment And Contingencies [Line Items]
Operating lease right-of-use ("ROU") assets			1,100,000		1,200,000
Operating lease liability			$ 1,100,000		$ 1,200,000
Area of office and warehouse space \| ft²	7,800
Lease extended term date	Dec. 31, 2029
Lease commencement date	Aug. 01, 2024
Operating lease, discount rate	10.69%

Research and Collaboration Arrangements - CFF - Additional Information (Details) - CFF Agreement - Cystic Fibrosis Foundation	1 Months Ended		3 Months Ended	6 Months Ended	12 Months Ended
	Aug. 31, 2023 USD ($)	Sep. 30, 2016 USD ($) Installment	Jun. 30, 2026 USD ($)	Jun. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaborative arrangement total amount of award	$ 6,300,000	$ 3,500,000
Collaborative arrangement achieved cumulative milestones				$ 1,800,000	$ 1,800,000
Expected payments multiples to equal actual award received		6
Number of installments to pay actual award \| Installment		3
Actual award payment period upon first commercial sale of product		4 years
Continuous period where the Company ceases to develop or commercialize any product		180 days
Collaborative arrangements special term		If at any time prior to the first commercial sale of a product developed as a result of the CFF Agreement, the Company ceases to use commercially reasonable efforts to develop or commercialize any product under the CFF Agreement for a continuous period of 180 consecutive days and fails to present a reasonable plan to resume commercially reasonable efforts, the Company will grant to CFF an irrevocable, exclusive worldwide interruption license under all of the Company’s interest in the research plan technology to exploit such product. Any third-party license granted by the Company shall be subject to such interruption license.
Revenue recognized			$ 100,000	200,000
Deferred revenue			900,000	900,000	1,100,000
Accounts receivable			0	0	0
Aggregate amount of transaction price allocated to remaining performance obligation			$ 900,000	$ 900,000	$ 1,100,000
Maximum
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future sales-based milestone payments multiples		3
Royalties multiples on actual award received		6

Commitments and Contingencies

6 Months Ended

Jun. 30, 2026

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

8. Commitments and Contingencies

Operating Lease Commitments

5980 Horton Street Building Lease

In May 2015, the Company executed a lease agreement (the “5980 Horton Lease”) for office and laboratory space in Emeryville, California. The 5980 Horton Lease, as amended, expires in August 2026. As of June 30, 2026, the right-of-use asset and lease liability related to the 5980 Horton Lease were each $0.1 million. As of December 31, 2025, the right-of-use asset and lease liability related to the 5980 Horton Lease were $0.3 million and $0.4 million, respectively.

5858 Horton Street Lease and Expansion

In October 2018, the Company executed a lease agreement (the “5858 Horton Lease”) for office and laboratory facilities in Emeryville, California. The 5858 Horton Lease, as amended in 2019, 2021 and 2022, consists of approximately 40,802 square feet of space and has a lease term through December 31, 2029. In July 2024, the Company extended the term of the 5858 Horton Lease for a period of twelve months to December 31, 2030. In accordance with ASC Topic 842, Leases, the Company accounted for the extension as a modification and remeasured the lease liability based on the new lease term and an updated, estimated incremental borrowing rate of 10.75%. The modification resulted in an increase to the lease liability of $0.8 million and a corresponding increase to the carrying value of the right-of-use asset. No gain or loss was recognized upon the modification. As of June 30, 2026, the right-of-use asset and lease liability related to the 5858 Horton Lease were $8.1 million and $10.4 million, respectively. As of December 31, 2025, the right-of-use asset and lease liability related to the 5858 Horton Lease were $8.8 million and $11.2 million, respectively.

In July 2024, the Company also entered into a lease agreement for additional office and laboratory space in Emeryville, California (the “5858 Horton Expansion Lease”). The 5858 Horton Expansion Lease consists of approximately 32,038 square feet of space and commenced on September 1, 2024 and has a lease term through December 31, 2030. As of June 30, 2026, the right-of-use asset and lease liability related to the 5858 Horton Expansion Lease were $7.2 million and $8.0 million, respectively. As of December 31, 2025, the right-of-use asset and lease liability related to the 5858 Horton Expansion Lease were $7.8 million and $8.6 million, respectively. The discount rate used to measure the lease liability was 11.02%.

Emeryville Warehouse Lease

In January 2024, the Company entered into a lease agreement for warehouse space in Emeryville, California (the “Warehouse Lease”). The Warehouse Lease commenced on August 1, 2024. The Warehouse Lease consists of approximately 7,800 square feet of warehouse space and has a lease term through December 31, 2029. As of June 30, 2026, the right-of-use asset and lease liability related to the Warehouse Lease were each $1.1 million. As of December 31, 2025, the right-of-use asset and lease liability related to the Warehouse Lease were each $1.2 million. The discount rate used to measure the lease liability related to the Warehouse Lease was 10.69%.

The following table summarizes the components of lease expense, which are included in operating expenses in the Company’s condensed statements of operations (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Operating lease cost	$	1,344	$	1,344	$	2,688	$	2,688
Variable lease cost		678		648		1,355		1,422
Total	$	2,022	$	1,992	$	4,043	$	4,110

Variable lease payments include amounts relating to common area maintenance and are recognized in the condensed statements of operations as incurred.

Cash paid for amounts included in the measurement of the Company’s operating lease liabilities and presented within cash used in operating activities in the condensed statements of cash flows was $2.9 million and $2.8 million for the six months ended June 30, 2026 and 2025, respectively.

The following table summarizes supplemental information related to operating leases:


	June 30, 2026			December 31, 2025
Weighted-average remaining lease term (in years):		4.4			4.8
Weighted-average discount rate:		10.8	%		10.8	%

The following table summarizes the maturities of lease liabilities as of June 30, 2026 (in thousands):


2026 (remaining six months)	$	2,725
2027		5,350
2028		5,510
2029		5,675
2030		5,455
Total future minimum lease payments		24,715
Less: Amount representing interest		(5,085	)
Present value of future minimum lease payments		19,630
Less: Current portion of operating lease liabilities		(5,374	)
Long-term portion of operating lease liabilities	$	14,256

Indemnification Agreements

In the ordinary course of business, the Company enters into agreements that may include indemnification provisions, such as with vendors and other parties. Pursuant to such agreements, the Company may indemnify, hold harmless and defend an indemnified party for losses suffered or incurred by the indemnified party. Some of the provisions will limit losses to those arising from third-party actions. In some cases, the indemnification will continue after the termination of the agreement. The maximum potential amount of future payments the Company could be required to make under these provisions is not determinable. The Company has never incurred material costs to defend lawsuits or settle claims related to these indemnification provisions. The Company has also entered into indemnification agreements with its directors and officers that require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors or officers to the fullest extent permitted by Delaware corporate law. The Company currently maintains directors’ and officers’ liability insurance that would generally enable it to recover a portion of any future amounts paid. The Company believes the estimated fair value of its indemnification agreements in excess of applicable insurance coverage is not material.

Contractual Obligations and Commitments

The Company enters into various agreements in the ordinary course of business, such as those with suppliers, CROs, CDMOs and clinical trial sites. These contracts generally provide for termination on notice or may have a potential termination fee if a purchase order is canceled within a specified time. The total value of non-cancellable obligations under contracts was $4.9 million and $4.0 million as of June 30, 2026 and December 31, 2025, respectively. This presentation of non-cancellable purchase obligations does not include any estimates of potential reduction of such liabilities related to mitigation obligations of the counter-parties in the event of cancellation under the terms of the Company's engagements.

Legal Proceedings

From time to time, the Company may become involved in legal proceedings arising from the ordinary course of its business. If applicable, the Company records a legal liability when it believes that it is probable that a liability has been incurred and the amount of the liability can be reasonably estimated. Significant judgment by the Company is required to determine both probability and the estimated amount. There are no material legal proceedings outstanding at June 30, 2026.

Pre-funded Warrants - Additional Information (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Jan. 22, 2026 $ / shares shares	Dec. 31, 2025 USD ($)	Dec. 31, 2024 USD ($) shares	Jun. 30, 2026 $ / shares	Dec. 22, 2025 shares	Nov. 30, 2025 $ / shares shares	Feb. 28, 2025 Holder shares	Feb. 29, 2024 $ / shares shares	Dec. 31, 2020 $ / shares	May 31, 2018 $ / shares
Class of Warrant or Right [Line Items]
Exercise price \| $ / shares									$ 18	$ 3.19
Number of prefunded warrant holders \| Holder							2
Pre-funded Warrants \| Common Stock
Class of Warrant or Right [Line Items]
Exercise price \| $ / shares	$ 0.0001			$ 0.0001
Warrant shares, exercised							508,476
Pre-funded Warrants \| Common Stock \| 2024 Follow On Public Offering
Class of Warrant or Right [Line Items]
Warrant shares become exercisable								3,583,476
Common stock offering price \| $ / shares								$ 29.4999
Issuance of pre-funded warrants \| $			$ 99.4
Pre-funded Warrants \| Common Stock \| 2025 Offering
Class of Warrant or Right [Line Items]
Warrant shares become exercisable						1,128,949
Common stock offering price \| $ / shares						$ 10.5099
Issuance of pre-funded warrants \| $		$ 11.2
Pre-funded Warrants \| Biotechnology Value Fund, L.P.
Class of Warrant or Right [Line Items]
Warrant shares, exercised					178,280
Pre-funded Warrants \| Biotechnology Value Fund, L.P. \| Exchange Agreement \| Common Stock
Class of Warrant or Right [Line Items]
Number of common shares exchanged for prefunded warrants	1,750,000		5,775,000
Pre-funded Warrants \| RA Capital Healthcare Fund, L.P \| Exchange Agreement \| Common Stock
Class of Warrant or Right [Line Items]
Number of common shares exchanged for prefunded warrants	4,850,000		535,000

Fair Value Measurements and Marketable Securities - Fair Value Hierarchy for Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and Cash Equivalents	$ 70,372	$ 60,241
Current Marketable Securities	290,962	342,414
Non-Current Marketable Securities	69,295	111,379
Fair Value on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Basis	431,075	513,307
Gross Unrealized Gains	70	730
Gross Unrealized Losses	(516)	(3)
Fair Value	430,629	514,034
Cash and Cash Equivalents	70,372	60,241
Current Marketable Securities	290,962	342,414
Non-Current Marketable Securities	69,295	111,379
Fair Value on Recurring Basis \| Cash [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash	29,718	10,696
Cash and Cash Equivalents	29,718	10,696
Fair Value on Recurring Basis \| Level 1 \| Money Market Funds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash	34,659	39,570
Cash and Cash Equivalents	34,659	39,570
Fair Value on Recurring Basis \| Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Basis	366,698	463,041
Gross Unrealized Gains	70	730
Gross Unrealized Losses	(516)	(3)
Fair Value	366,252	463,768
Cash and Cash Equivalents	5,995	9,975
Current Marketable Securities	290,962	342,414
Non-Current Marketable Securities	69,295	111,379
Fair Value on Recurring Basis \| Level 2 \| Certificates of Deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Basis	20,892	35,986
Gross Unrealized Gains	4	37
Gross Unrealized Losses	(9)
Fair Value	20,887	36,023
Current Marketable Securities	20,887	36,023
Fair Value on Recurring Basis \| Level 2 \| Commercial Paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Basis	54,813	63,875
Gross Unrealized Gains	5	48
Gross Unrealized Losses	(52)
Fair Value	54,766	63,923
Cash and Cash Equivalents	5,995	5,479
Current Marketable Securities	48,771	58,444
Fair Value on Recurring Basis \| Level 2 \| U.S. Treasuries
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Basis	92,469	76,920
Gross Unrealized Gains	10	153
Gross Unrealized Losses	(216)
Fair Value	92,263	77,073
Current Marketable Securities	67,884	63,589
Non-Current Marketable Securities	24,379	13,484
Fair Value on Recurring Basis \| Level 2 \| Corporate Bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Amortized Cost Basis	198,524	286,260
Gross Unrealized Gains	51	492
Gross Unrealized Losses	(239)	(3)
Fair Value	198,336	286,749
Cash and Cash Equivalents		4,496
Current Marketable Securities	153,420	184,358
Non-Current Marketable Securities	$ 44,916	$ 97,895

Long Term Debt

6 Months Ended

Jun. 30, 2026

Debt Disclosure [Abstract]

Long Term Debt

9. Long-Term Debt

In June 2026, the Company entered into a Loan and Security Agreement (the “Loan and Security Agreement”) with Hercules Capital, Inc., providing for up to $200.0 million in term loan borrowings. At the closing on June 24, 2026, the Company had access to a $50.0 million tranche, of which it borrowed $20.0 million. The remaining $30.0 million is available, at the Company's option, through June 15, 2027. The Company may draw up to an additional $100.0 million in three separate tranches upon achievement of certain clinical, regulatory, financing and capitalization milestones. As of June 30, 2026, the Company had not met the requirements to access the funds under these tranches, as it had not achieved the related milestone. An additional fifth tranche of $50.0 million may be made available upon the Company's request and at Hercules’ sole discretion and is not contingent upon the Company’s achievement of the milestones applicable to the prior tranches. The Loan and Security Agreement matures on June 1, 2031. The initial borrowing of $20.0 million bears interest at a floating rate equal to the greater of (i) the prime rate plus 2.0% and (ii) 8.75%, and all future borrowings, including the available balance of $30.0 million of the $50.0 million tranche available as of June 24, 2026, bear interest at a floating rate equal to the greater of (i) the prime rate plus 2.5% and (ii) 9.25%. The floating interest rate is capped at 0.75% more than the interest rate at the time of the borrowing. The Company is required to make monthly interest-only payments for borrowings under the initial tranche of $50.0 million for a period of 29 months, which may be extended by up to an additional 30 months upon achievement of certain clinical, regulatory, financing and capitalization milestones.

The Loan and Security Agreement includes an end-of-term charge ranging from 3.70% to 6.50% of the aggregate principal amount, depending on the timing of the repayment. The recognition of the end-of-term charge is reflected as interest expense over the term of the borrowing using the effective interest rate method. The Company may voluntarily prepay outstanding borrowings, subject to prepayment premiums ranging from 1.0% to 3.0% of the principal amount prepaid, depending on the timing of repayment.

In connection with the Loan and Security Agreement, the Company paid a $0.5 million facility fee for the $50.0 million tranche and is subject to a 1.00% facility fee for subsequent borrowings. Because the facility fee relates to the total $50.0 million initial tranche, the Company allocated the costs among the two initial borrowing tranches based on the relative borrowing capacity available under each tranche. In addition to the initial facility fee, the Company incurred approximately $2.1 million of debt issuance costs, consisting primarily of lender fees and third-party legal and other transaction costs. Because the debt issuance costs relate to the $150.0 million for the first four tranches of the Loan and Security Agreement, the Company allocated the costs among the various borrowing tranches based on the relative borrowing capacity available under each tranche. Facility fees and debt issuance costs attributable to funded borrowings were recorded as a reduction to the carrying value of the debt and are being amortized to interest expense using the effective interest method over the expected term of the borrowing. Facility fees and debt issuance costs attributable to unfunded borrowing commitments were capitalized to prepaid and other current assets or other non-current assets according to the access period or classification of the underlying debt, as appropriate, and are being amortized to interest expense over the applicable commitment periods or will be reclassified as debt upon funding of the related borrowings.

The Loan and Security Agreement contains financial covenants, including minimum cash and performance-based covenants, that are not yet subject to testing or effective as of June 30, 2026. Upon the occurrence of certain events and beginning no earlier than January 1, 2028, the Company may become subject to minimum cash and performance-based financial covenants. The Loan and Security Agreement contains customary events of default, including failure to make required payments or maintain compliance with covenants, breach, default, insolvency, attachment or judgment events and any circumstance which could reasonably be expected to have a material adverse effect on the Company. The Loan and Security Agreement also contains customary affirmative and restrictive covenants, representations and warranties associated with a secured loan facility, including certain limitations on indebtedness, liens, investments, distributions, mergers or acquisitions and corporate changes.

As of June 30, 2026, the outstanding principal under the Loan and Security Agreement was $20.0 million, bearing interest at a rate of 8.75% per annum, with an effective interest rate of 10.64%.

The future principal payments due under the Loan and Security Agreement as of June 30, 2026 were as follows (in thousands):


Remainder of 2026	$	—
2027		—
2028		594
2029		7,523
2030		8,230
Thereafter		4,953
Total	$	21,300

As of June 30, 2026, the carrying value of the Loan and Security Agreement was as follows (in thousands):


Principal outstanding	$	20,000
Less: unamortized discount and debt issuance costs		(413	)
Long-term debt, net	$	19,587

As of June 30, 2026, debt issuance costs and debt discount of approximately $2.2 million were included in prepaid expenses and other current assets and in other non-current assets on the condensed balance sheet, as appropriate. As of June 30, 2026, approximately $1.9 million of unpaid debt issuance costs were included in accounts payable on the condensed balance sheet. For the three and six months ended June 30, 2026, the Company recognized an immaterial amount of interest expense for borrowings under the Loan and Security Agreement. The Loan and Security Agreement is secured by a first-priority security interest in substantially all of the Company’s assets, including intellectual property, subject to customary exclusions.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 405
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477092/405-40-50-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 470
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/470/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1C

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1C

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1C
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1C

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1I

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1I

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1I

+ Details

Stock-based Compensation - Summary of Restricted Stock Units (RSU) (Details) - Restricted Stock Units (RSU)	6 Months Ended
	Jun. 30, 2026 shares
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of Shares, Unvested Beginning Balance	744,770
Awarded	1,290,476
Vested	(100,241)
Canceled/Forfeited	(118,263)
Number of Shares, Unvested Ending Balance	1,816,742

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (l)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 1D
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-1D

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 35
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480483/718-10-35-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(04)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(02)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(03)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Research and Collaboration Arrangements - CFF - Additional Information (Details 1)	Jun. 30, 2026
CFF Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue, estimated performance period	4 years

Segment Information

6 Months Ended

Jun. 30, 2026

Segment Reporting [Abstract]

Segment Information

20. Segment Information

The Company operates in a single operating and reportable segment, which includes all activities related to discovery, development and commercialization of durable and disease-targeted therapeutics. The determination of a single business segment is consistent with the financial information regularly provided to the Company's chief operating decision maker (the "CODM") who manages the business activities on a consolidated basis. The Company's CODM is its Chief Executive Officer who assesses performance for the business and decides how to allocate resources based on net loss that also is reported on the statements of operations. In making this assessment, the CODM reviews and evaluates net loss to monitor budget versus actual results and to analyze cash flows for purposes of allocating resources and assessing financial performance.

In addition to the significant expense categories included within net loss presented in the Company's condensed statements of operations, the following table provides disaggregated amounts that comprise research and development expenses (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Direct research and development expenses for 4D-150	$	43,557	$	19,134	$	86,280	$	31,907
Unallocated personnel costs (including stock-based compensation)		15,996		17,871		30,526		35,099
All other costs		8,729		10,946		16,456		21,644
Total research and development expenses	$	68,282	$	47,951	$	133,262	$	88,650

Effective in the first quarter of 2026, the Company updated the presentation of segment operating expenses provided to the CODM. This change in the presentation reflects how segment information is currently reviewed by the CODM. Prior period segment information has been recast to conform to the current period presentation.

The measure of segment assets is reported on the balance sheets as total assets. As of and for the six months ended June 30, 2026 and 2025, all of the Company’s long-lived assets were located in the United States. The Company's revenues by geographic region, based on the location of the customer, are disclosed in Note 2, Summary of Significant Accounting Policies.

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 31
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-15

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 11: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 12: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 14: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 16: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 17: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 34
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-34

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26C

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26B

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/280/tableOfContent

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 26
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-26

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

+ Details

Accrued and Other Current Liabilities

6 Months Ended

Jun. 30, 2026

Payables and Accruals [Abstract]

Accrued and Other Current Liabilities

5. Accrued and Other Current Liabilities

Accrued and other current liabilities consisted of the following (in thousands):


	June 30, 2026		December 31, 2025
Payroll and related expenses	$	7,818	$	13,806
Accrued clinical and preclinical study costs		14,014		10,273
Consulting and outside services		3,475		2,666
Other accrued expenses		124		129
Total accrued and other current liabilities	$	25,431	$	26,874

California Institute for Regenerative Medicine Award

6 Months Ended

Jun. 30, 2026

Award From California Institute For Regenerative Medicine [Abstract]

California Institute for Regenerative Medicine Award

17. California Institute for Regenerative Medicine Award

On April 12, 2026, the Company received a Notice of Award (the "Notice of Award") from the California Institute for Regenerative Medicine (“CIRM”) for a grant of approximately $5.9 million (the “CIRM Grant”), to support the early stage development of the proprietary adeno-associated virus (AAV) gene therapy candidate for the treatment of Alpha-1 Antitrypsin (AAT) Deficiency. The CIRM Grant is payable to the Company upon achievement of certain early stage developmental milestones. CIRM could permanently cease disbursements if milestones are not met within four months of the scheduled completion date. Additionally, if CIRM determines, in its sole discretion, that the Company has not complied with the terms and conditions of the CIRM Grant, CIRM may suspend or permanently cease disbursements. Funds received under the CIRM Grant may only be used for allowable project costs specifically identified with the CIRM-funded project. Project costs can include, but are not limited to, salary for personnel, supplies, consultants and clinical study costs. The Company will co-fund the research project in the amount of $1.4 million for such project costs under the terms of the CIRM Grant. Any unused funds must be returned to CIRM upon completion or termination of the project. The Company received an initial payment of $1.0 million from CIRM upon receipt of the Notice of Award.

Proceeds from the CIRM Grant are recognized over the period necessary to match the related research and development expense when it is probable that the Company has complied with the CIRM Grant conditions and will receive the proceeds pursuant to the milestones defined in the Notice of Award as reimbursement of those expenditures. The CIRM Grant proceeds, if any, received in advance of having incurred the related research and development expense are recorded in deferred grant reimbursements and recognized as an offset against research and development expense on the Company’s condensed statements of operations when the related research and development expenses are incurred.

During the three months ended June 30, 2026, the Company achieved the first developmental milestone and became entitled to a reimbursement of $3.1 million and recognized a grant receivable in prepaid and other current assets on its condensed balance sheet as of June 30, 2026. As of June 30, 2026, the Company recognized a deferred grant reimbursement of $4.0 million related to the CIRM grant on its condensed balance sheet, as the grant reimbursement exceeds the amount of grant reimbursement income recognized during the three and six months ended June 30, 2026. During the three and six months ended June 30, 2026, the Company recognized $0.1 million of grant reimbursements as a reduction of research and development expense related to the CIRM Grant on its condensed statement of operations.

Derivative Liability - Additional Information (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2026	Dec. 31, 2025
Derivative [Line Items]
Change in control discount rate	15.00%	15.00%
Estimated fair value of derivative liability	$ 0.4	$ 0.4
Minimum
Derivative [Line Items]
Change of control payment	$ 0.0	$ 0.0
Change in control event percentage	5.00%	5.00%
Maximum
Derivative [Line Items]
Change of control payment	$ 18.9	$ 18.9
Change in control event percentage	50.00%	50.00%
Product Achieving Development or Commercial Status \| Minimum
Derivative [Line Items]
Change in control event percentage	4.80%	4.80%
Product Achieving Development or Commercial Status \| Maximum
Derivative [Line Items]
Change in control event percentage	17.20%	17.20%

- Definition

Fair value, before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

+ References + Details

Disclosure - Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2026

Accounting Policies [Abstract]

Schedule of Concentration of Risk

The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total revenue are as follows:


	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2026	2025	2026	2025
Customer A	98%	0%	97%	0%
Customer B	*	100%	*	100%
Total	98%	100%	97%	100%

______________

* Less than 10%

Schedule of Revenues by Geographic Region

The Company’s total revenues by geographic region, based on the location of the customer, are as follows (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2026		2025		2026		2025
Japan	$	3,691	$	—	$	6,648	$	—
United States		90		15		180		29
Total revenue	$	3,781	$	15	$	6,828	$	29

Stock-based Compensation - Schedule of Assumptions Used in Black-Scholes Valuation Model to Estimate Fair Value of Stock Options (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term		5 years 10 months 24 days
Expected volatility, minimum	85.90%	86.50%	85.90%	84.90%
Expected volatility, maximum	87.30%	88.90%	89.00%	88.90%
Risk-free interest rate		4.10%
Risk-free interest rate, minimum	4.00%		3.80%	4.10%
Risk-free interest rate, maximum	4.30%		4.30%	4.60%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	5 years 10 months 24 days		5 years 10 months 24 days	5 years 10 months 24 days
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term	6 years 1 month 6 days		6 years 1 month 6 days	6 years 1 month 6 days

Stock-based Compensation

6 Months Ended

Jun. 30, 2026

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

12. Stock-based Compensation

2025 Employment Inducement Award Plan

On February 3, 2025, the Company’s board of directors adopted the 2025 Employment Inducement Plan (the “Inducement Plan”) pursuant to which the Company reserved 500,000 shares of its common stock to be used exclusively for grants of awards to individuals who were not previously employees or directors, as an inducement material to the individual’s entry into employment with the Company within the meaning of Rule 5635(c)(4) of the Marketplace Rules of the Nasdaq Stock Market. The Inducement Plan provides for the grant of stock options, restricted stock units, and other stock-based awards. In January 2026, the Company's board of directors adopted an amendment to the Inducement Plan to reserve an additional 1,000,000 shares of common stock under the Inducement Plan. As of June 30, 2026, there were 872,350 shares available for future grants under the Inducement Plan.

2020 Incentive Award Plan

In December 2020, the Company adopted the 2020 Incentive Award Plan (“2020 Plan”), which became effective on December 10, 2020. The 2020 Plan initially reserved 2,606,546 shares of common stock for the issuance of stock options, stock appreciation rights, restricted stock awards, restricted stock units, performance bonus awards, performance stock units, dividend equivalents or other stock or cash based award granted to employees, directors and consultants of the Company. The number of shares reserved for future issuance under the 2020 Plan will increase annually on the first day of each fiscal year beginning in 2021 and ending in 2030 by the lesser of (i) 5% of the shares of common stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (ii) such number of shares of common stock as determined by the Company's board of directors, provided, however, no more than 18,000,000 shares of the Company’s common stock may be issued upon the exercise of incentive stock options. As a result of the operation of the automatic annual increase provision of the 2020 Plan, an additional 2,289,625 shares of common stock became available for issuance on February 28, 2025 and an additional 2,880,394 shares of common stock became available for issuance on March 18, 2026 under the 2020 Plan. All stock options are exercisable over a period not to exceed the contractual term of ten years from the date the stock options were issued. As of June 30, 2026, there were 1,735,472 shares available for grant under the 2020 Plan.

Following the effectiveness of the 2020 Plan, the Company will not make any further grants under the 2015 Equity Incentive Plan (the “2015 Plan”). However, the 2015 Plan continues to govern the terms of stock options that remain outstanding under the 2015 Plan.

2015 Equity Incentive Plan

The 2015 Plan provided for grants of stock options, stock appreciation rights, restricted stock and restricted stock unit awards to employees, directors and consultants of the Company. As of June 30, 2026, stock options to purchase 1,112,990 shares of common stock were outstanding under the 2015 Plan. All stock options are exercisable over a period not to exceed the contractual term of ten years from the date the stock options were issued and are granted at prices not less than the estimated fair market value of the Company’s common stock on the grant date as determined by the board of directors.

No additional grants will be made under the 2015 Plan, and all outstanding grants under the 2015 Plan that are repurchased, forfeited, expire or are cancelled are returned to the 2015 Plan and are not available for grant under the 2020 Plan.

Employee Stock Purchase Plan

In December 2020, the Company adopted the 2020 Employee Stock Purchase Plan (the “2020 ESPP”). Under the 2020 ESPP, 252,337 shares of the Company’s common stock were initially reserved for employee purchases of the Company’s common stock under terms and provisions established by the Company’s board of directors and approved by the Company’s stockholders. The number of shares reserved for future issuance under the 2020 ESPP will increase annually on the first day of each fiscal year beginning in 2021 and ending in 2030 by the lesser of (i) 1% of the shares of common stock outstanding (on an as converted basis) on the last day of the immediately preceding fiscal year and (ii) such number of shares of common stock as determined by the Company’s board of directors, provided, however, no more than 15,000,000 shares of the Company’s common stock may be issued under the 2020 ESPP. As a result of the operation of this annual increase provision of the 2020 ESPP, an additional 150,000 shares of common stock became available on February 28, 2025 and an additional 576,079 shares of common stock became available for issuance on March 18, 2026 under the 2020 ESPP.

Under the 2020 ESPP, the Company’s employees may purchase common stock through payroll deductions at a price equal to 85% of the lower of the fair market value of the stock at the beginning of the offering period or at the end of each applicable purchase period. The 2020 ESPP provides for a series of overlapping 24-month offering periods comprising four six-month purchase periods. Contributions under the 2020 ESPP are limited to a maximum of 15% of an employee’s eligible compensation.

Restricted Stock Units

The Company has granted restricted stock unit (RSU) awards under the 2020 Incentive Award Plan that vest over a period of four years. The following table summarizes the RSU activity:


	Number of Shares
Unvested balance at December 31, 2025		744,770
Awarded		1,290,476
Vested		(100,241	)
Canceled/Forfeited		(118,263	)
Unvested balance at June 30, 2026		1,816,742

Stock Options

The following table summarizes the stock options activity:


	Number of Shares Underlying Outstanding Options
Balances at December 31, 2025		9,412,808
Options granted		3,176,795
Options exercised		(217,393	)
Options expired		(341,964	)
Options forfeited		(293,098	)
Balances at June 30, 2026		11,737,148
Options exercisable at June 30, 2026		6,081,392
Options vested and expected to vest at June 30, 2026		11,737,148

The Company estimates the fair value of stock options using the Black-Scholes option pricing model. The fair value of employee and nonemployee stock options is recognized on a straight-line basis over the requisite service period of the awards. The fair value of the Company’s stock options was estimated using the following assumptions:


	Three Months Ended June 30,		Six Months Ended June 30,
	2026	2025	2026	2025
Expected term	5.9 - 6.1 years	5.9 years	5.9 - 6.1 years	5.9 - 6.1 years
Expected volatility	85.9% - 87.3%	86.5% - 88.9%	85.9% - 89.0%	84.9% - 88.9%
Risk-free interest rate	4.0% - 4.3%	4.1%	3.8% - 4.3%	4.1% - 4.6%
Expected dividend yield	—%	—%	—%	—%

Expected Term. The expected term for employee stock options is calculated using the simplified method as the Company does not have sufficient historical information to provide a basis for this estimate. The simplified method is based on the average of the vesting tranches and the contractual life of each grant. The expected term for nonemployee stock options is the contractual term of the stock options.

Expected Volatility. The expected volatility is based on a mix of the Company’s historical volatility and the historical volatility of comparable companies with similar attributes to the Company, including industry, stage of life cycle, size and financial leverage. For each grant, the Company measured historical volatility over a period equivalent to the expected term.

Risk-free Interest Rate. The risk-free interest rate is based on the yield available on U.S. Treasury zero-coupon issues whose term is similar in duration to the expected term of the respective stock option.

Expected Dividend Yield. The Company has not paid and does not anticipate paying any dividends on its common stock in the future. Accordingly, the Company has estimated the dividend yield to be zero percent.

Stock-Based Compensation Expense

The following table is a summary of stock-based compensation expense incurred for employees and nonemployees by function (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Research and development	$	2,720	$	2,498	$	4,652	$	6,479
General and administrative		3,164		2,460		5,685		5,465
Total stock-based compensation expense	$	5,884	$	4,958	$	10,337	$	11,944

Research and Collaboration Arrangements

6 Months Ended

Jun. 30, 2026

Research And Collaboration Arrangements [Abstract]

Research and Collaboration Arrangements

6. Research and Collaboration Arrangements

Collaboration and license revenue for each period was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Otsuka Pharmaceutical Co., Ltd.	$	3,691	$	—	$	6,648	$	—
Cystic Fibrosis Foundation		90		15		180		29
Total revenue	$	3,781	$	15	$	6,828	$	29

Deferred revenue is summarized as follows (in thousands):


	June 30, 2026		December 31, 2025
Otsuka Pharmaceutical Co., Ltd.	$	2,390	$	—
Cystic Fibrosis Foundation		925		1,105
Total deferred revenue	$	3,315	$	1,105

An immaterial amount of revenue was recorded during the six months ended June 30, 2026 and 2025 which was included in deferred revenue at January 1, 2026 and 2025, respectively, for Cystic Fibrosis Foundation.

Cystic Fibrosis Foundation (“CFF”)

In September 2016, the Company entered into an award agreement for the Optimized Adeno-Associated Virus for Lung Epithelia Gene Delivery Development Program with CFF, a non-profit organization dedicated to finding a cure for cystic fibrosis, an inherited disorder that causes disease in the pulmonary airways leading to morbidity and mortality. Under this agreement, CFF contributes funding to help advance the Company’s cystic fibrosis research program. The September 2016 grant award agreement was incorporated into a new grant award agreement with CFF in September 2017 with the same objectives, which was subsequently amended in August 2018 and February 2021. In August 2023, the Company executed a third amendment to the agreement (the “August 2023 Amendment”), which modified the research plan, increased the aggregate milestone payments from $3.5 million to $6.3 million and extended the estimated project completion date. The aforementioned September 2017 agreement and three amendments are collectively referred to as the “CFF Agreement”. The August 2023 Amendment represents a contract modification to an existing contract under ASC Topic 606, given the amendment did not include any additional goods or services, and the remaining research activities are not distinct from those previously provided. The August 2023 Amendment did not impact the transaction price, given the increased award amount relates to variable consideration for future milestones that are fully constrained. Accordingly, the contract modification did not result in a revenue adjustment. As of June 30, 2026 and December 31, 2025, the Company had achieved cumulative milestones totaling $1.8 million under the CFF Agreement. The remaining award amount will be paid by CFF based on achievement of certain development milestones by the Company.

The Company expects to make payments to CFF equal to six times the actual award received by the Company in three installments within the first four years of the first commercial sale of a product developed under this agreement. The Company also has agreed to make future sales-based milestone payments to CFF of up to three times the actual award received upon achieving specified commercialization milestones with respect to the first of any product developed utilizing any compound covered under the CFF Agreement. The CFF Agreement also requires the Company to pay to CFF royalties of a mid-single digit percentage, up to six times the actual award received, on any amounts received by the Company from the sale, license or transfer to a third-party of rights in the technology developed as a result of this collaboration. Any such royalty payments shall be credited against the payments owed by the Company upon first commercial sale. In the event of a change of control of the Company, CFF will receive certain payments, depending on the timing of the change of control and the size of the transaction.

To date, the Company has not developed a commercial product in connection with the CFF Agreement, and it has not licensed, sold or otherwise transferred to another party the product developed under the CFF Agreement or the underlying technology.

If at any time prior to the first commercial sale of a product developed as a result of the CFF Agreement, the Company ceases to use commercially reasonable efforts to develop or commercialize any product under the CFF Agreement for a continuous period of 180 consecutive days and fails to present a reasonable plan to resume commercially reasonable efforts, the Company will grant to CFF an irrevocable, exclusive worldwide interruption license under all of the Company’s interest in the research plan technology to exploit such product. Any third-party license granted by the Company shall be subject to such interruption license.

The Company identified one performance obligation within the CFF Agreement for research activities. The CFF Agreement does not include a significant financing component.

The Company concluded that the transaction price should not include the variable consideration related to future research milestones as they were considered to be constrained as it is probable that the inclusion of such variable consideration could result in a significant reversal of cumulative revenue in the future. The Company re-evaluates the transaction price and estimated period of performance at each reporting period.

Revenue recognized during the three and six months ended June 30, 2026 was $0.1 million and $0.2 million, respectively, while revenue recognized during the three and six months ended June 30, 2025 was immaterial. As of June 30, 2026 and December 31, 2025, deferred revenue relating to the CFF Agreement was $0.9 million and $1.1 million, respectively. There were no accounts receivable from CFF under the CFF Agreement as of June 30, 2026 and December 31, 2025. As of June 30, 2026 and December 31, 2025, the aggregate amount of the transaction price allocated to the remaining performance obligation was $0.9 million and $1.1 million, respectively. Based on current timelines, the deferred revenue is expected to be recognized as revenue over the next four years as the Company performs research services through the completion of IND-enabling studies.

The obligation to make payments to CFF upon a change of control meets the definition of an embedded derivative that is required to be bifurcated and separately accounted for as a derivative liability. See Note 3, Fair Value Measurements and Marketable Securities, and Note 16, Derivative Liability, for further discussion of the embedded derivative.

Otsuka Pharmaceutical Co., Ltd.

On October 31, 2025, the Company entered into a Collaboration and License Agreement (the "Otsuka Agreement") with Otsuka. Pursuant to the Otsuka Agreement, the Company granted Otsuka an exclusive royalty-bearing sublicensable license to its intellectual property to develop, manufacture and commercialize 4D-150, its lead product candidate for ophthalmological diseases, in Japan, Korea, China, Australia, and certain other Asia-Pacific markets ("Otsuka Territory"). The Company retains full development and commercialization rights for 4D-150 outside the Otsuka Territory, including the United States, Latin America, and Europe.

Otsuka will lead all regulatory and commercialization activities in the Otsuka Territory. The Company will lead all Phase 3 clinical activity globally, including within the Otsuka Territory. In aggregate, the Company is currently responsible for separate global phase 3 trials for wet age-related macular degeneration ("wet AMD") and diabetic macular edema (“DME”), local clinical trials in the Otsuka Territory as required by local regulatory authorities, and several other studies, including the related regulatory activities and long-term follow up studies. The Company and Otsuka will coordinate and review the development and other activities through a joint steering committee.

The Company also will manufacture and supply 4D-150 to Otsuka for clinical and commercial use at a supply price derived from the Company's manufacturing costs plus a margin.

The Company has received a nonrefundable upfront cash payment of $85.0 million and is eligible to receive quarterly clinical trial cost sharing and reimbursement amounts. In addition, the Company is eligible for up to $335.5 million in potential regulatory and commercial milestone payments and tiered double-digit royalties on net sales in the Otsuka Territory, and subject to royalty reductions under certain circumstances.

The Otsuka Agreement will remain in effect, unless earlier terminated, on a country-by-country basis, until the date that Otsuka is no longer developing or commercializing 4D-150 in such country within the Otsuka Territory. Otsuka may terminate the Otsuka Agreement for convenience, on a country-by-country basis, upon sufficient prior written notice as per the Otsuka Agreement, or due to safety reasons or the failure of certain of the Company’s related clinical trials to achieve their primary endpoints. The Company may terminate the Otsuka Agreement upon notice if Otsuka ceases all development activities and commercialization of 4D-150 in Japan for an agreed upon period as per the Otsuka Agreement and does not resume such activities or commercialization within a specified notice period. Upon termination, any license granted by the Company to Otsuka will terminate.

The Company concluded that Otsuka is a customer and that the arrangement represents a contract with a customer under the scope of ASC 606. The Company identified the following promised goods and services that represent performance obligations:

•

the exclusive license to its intellectual property to develop, manufacture and commercialize 4D-150 in the Otsuka Territory,

•

performance of separate global phase 3 trials for wet AMD and DME, local clinical trials in the Otsuka Territory as required by the local regulatory authorities, and several other studies, including the associated regulatory and joint steering committee activities. Separate performance obligations were identified for each individual trial or study.

The license was considered functional intellectual property as of the inception of the Otsuka Agreement and distinct from other promises under the contract, as Otsuka can benefit from the license on its own or together with other readily available resources. Each of the clinical trial and other study services were considered distinct as the customer can benefit from these services together with the license transferred at the inception of the Otsuka Agreement. The clinical trial and other study services will not modify or customize the initial intellectual property transferred at contract inception due to the late stage of development of the intellectual property.

The Company concluded manufacturing and supply of 4D-150 for clinical and commercial use does not represent a performance obligation, as these activities are at Otsuka’s option. Product supply is priced at standalone selling prices, and therefore does not provide Otsuka with material rights.

To the extent Otsuka requests the Company to supply 4D-150, such supply will be considered a separate contract with the customer.

The initial transaction price includes the upfront cash payment and variable consideration for clinical trials and other studies performance obligations, some of which have started and others that have not yet started as of June 30, 2026. The upfront cash payment is $85 million and was received during the year ended December 31, 2025. The variable consideration in the form of the estimated cost sharing and reimbursement of approximately $33.4 million represents the amount allocated to unsatisfied or partially unsatisfied performance obligations, that have already started as of June 30, 2026, and was allocated entirely to the clinical trials and other studies performance obligations using the variable consideration allocation exception.

The regulatory milestone amounts are not currently probable and have not been included in the transaction price as the amounts are fully constrained. The sales-based commercial milestones and royalties relate to the granted intellectual property license and will be recognized when the related sales occur.

At the end of each reporting period, the Company will re-evaluate the estimated variable consideration and if necessary, adjust the transaction price.

To determine the standalone selling prices of each performance obligation, the Company used significant estimates and assumptions that include but are not limited to, expected market opportunity and pricing, expected future costs of clinical trials and other studies, and timelines and likelihood of success of clinical and regulatory activities. For the standalone selling price of the license, the Company used a discounted cash flow analysis of projected cash flows and potential revenues from the commercial sales of 4D-150 in the Otsuka Territory. To determine the standalone selling prices of the Company’s obligations to conduct clinical trials and other studies, the expected cost plus margin approach was used.

Variable consideration to which the Company is entitled to is allocated directly to the associated performance obligations, as it is triggered by the Company’s performance or represents specific outcomes from such performance, and the resulting allocation meets the allocation objective.

The upfront amount of $85.0 million was allocated entirely to the license performance obligation and was recognized at a point in time upon the transfer of control during the year ended December 31, 2025.

Revenue attributable to the remaining performance obligations to conduct clinical trials and other studies will be recognized over time as the underlying services are performed, over the period through the completion of program development activities. Progress is measured using an input method based on cumulative cost incurred relative to the total estimated cost of the performance obligation. Estimated progress and the underlying costs will be reviewed and adjusted as necessary at every reporting date. Revenue from clinical trials and other studies performance obligations was approximately $3.7 million and $6.6 million during the three and six months ended June 30, 2026, respectively.

The transaction price amount allocated to unsatisfied or partially unsatisfied performance obligations as of June 30, 2026 was approximately $33.4 million, expected to be recognized during 2026 through 2032 as clinical trials and other studies continue. Certain performance obligations have not started as of June 30, 2026 and the related amounts are not included above.

The amount due from Otsuka was $4.6 million as of June 30, 2026, for the estimated cost sharing and reimbursement and is presented as collaboration receivable on the Company's condensed balance sheets.

Stock-based Compensation - Summary of Stock-based Compensation Expense for Employees and Nonemployees by Function (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 5,884	$ 4,958	$ 10,337	$ 11,944
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	2,720	2,498	4,652	6,479
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Total stock-based compensation expense	$ 3,164	$ 2,460	$ 5,685	$ 5,465

Net Loss Per Share, Basic and Diluted - Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Numerator
Net loss	$ (72,936)	$ (54,658)	$ (141,696)	$ (102,630)
Denominator
Weighted-average shares outstanding used in computing net loss per share, basic	70,272,018	55,927,091	69,175,213	55,836,075
Weighted-average shares outstanding used in computing net loss per share, diluted	70,272,018	55,927,091	69,175,213	55,836,075
Net loss per share, basic	$ (1.04)	$ (0.98)	$ (2.05)	$ (1.84)
Net loss per share, diluted	$ (1.04)	$ (0.98)	$ (2.05)	$ (1.84)

- Definition

The amount of net income (loss) for the period per each share of common stock or unit outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-52

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-15

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-7

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-10

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-7

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

+ Details

- Definition

The amount of net income (loss) for the period available to each share of common stock or common unit outstanding during the reporting period and to each share or unit that would have been outstanding assuming the issuance of common shares or units for all dilutive potential common shares or units outstanding during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482662/260-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 52
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-52

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 15
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482635/260-10-55-15

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (e)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-7

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-2

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(25))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(27))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(23))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-7

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

+ Details

- Definition

Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

+ References

+ Details

Income Taxes - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Income Tax Disclosure [Abstract]
Provision for income tax	$ 0	$ 0	$ 0	$ 0

- Definition

Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-4

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-21

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-14

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 231
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SAB Topic 6.I.7)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479360/740-10-S99-1

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-10

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Subparagraph (a)
-SubTopic 20
-Topic 740
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482659/740-20-45-2

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h))
-SubTopic 10
-Topic 235
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

+ Details

401(K) Plan - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
2014 401(k) Plan
Defined Contribution Plan Disclosure [Line Items]
Employer contribution	$ 0.6	$ 0.5	$ 1.2	$ 1.1

- Definition

Amount of contribution received by defined benefit plan from employer which increases plan assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (c)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-5

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-5

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (c)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-5

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (c)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-5

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 17
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480482/715-20-55-17

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 18
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480482/715-20-55-18

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-6

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

+ Details

Segment Information - Schedule Of Disaggregated Amounts That Comprise Research and Development Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Segment Reporting Information [Line Items]
Total research and development expenses	$ 68,282	$ 47,951	$ 133,262	$ 88,650
Direct Research and Development Expenses \| 4D-150
Segment Reporting Information [Line Items]
Total research and development expenses	43,557	19,134	86,280	31,907
Unallocated Personnel Costs (Including Stock-based Compensation)
Segment Reporting Information [Line Items]
Total research and development expenses	15,996	17,871	30,526	35,099
All Other Costs
Segment Reporting Information [Line Items]
Total research and development expenses	$ 8,729	$ 10,946	$ 16,456	$ 21,644

Derivative Liability

6 Months Ended

Jun. 30, 2026

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Derivative Liability

16. Derivative Liability

The Company identified an embedded derivative resulting from the change of control provision in the CFF Agreement. Embedded derivatives that are required to be bifurcated from the underlying host instrument are accounted for and valued as separate financial instruments. At the inception of the derivative in 2017, the Company recognized this derivative as a liability and revenue was reduced by the initial fair value of the derivative liability. The Company remeasures the derivative liability to fair value at each reporting period and records the change in fair value of the derivative liability as other income (expense), net. The Company uses a present value analysis with multiple scenarios, which incorporates assumptions and estimates to value the derivative instrument. The Company assesses these assumptions and estimates on a periodic basis as additional information impacting the assumptions is obtained. Estimates and assumptions impacting the fair value measurement include the change of control payment to CFF (range of zero to $18.9 million at June 30, 2026 and December 31, 2025), the probability of a change of control event (range of 5.0% to 50.0% at June 30, 2026 and December 31, 2025), the probability of the product achieving development or commercial status at time of change of control (range of 4.8% to 17.2% at June 30, 2026 and December 31, 2025) and the discount rate (15% at June 30, 2026 and December 31, 2025). The Company determined the estimated fair value of this liability as of the inception date of the CFF Agreement and concluded that the amount was immaterial. The Company determined the fair value of this derivative liability was $0.4 million as of each of June 30, 2026 and December 31, 2025. See Note 3, Fair Value Measurements and Marketable Securities, and Note 6, Research and Collaboration Arrangements for further discussion of the fair value of the embedded derivative.

- Definition

The entire disclosure for derivative instruments and hedging activities including, but not limited to, risk management strategies, non-hedging derivative instruments, assets, liabilities, revenue and expenses, and methodologies and assumptions used in determining the amounts.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 182
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-182

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 185
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-185

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 184
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-184

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 181
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-181

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (a)(5)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (a)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4H
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4H

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4H
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4H

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 15
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480960/815-15-50-3

Reference 13: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 183
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480401/815-10-55-183

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (a)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4K
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4K

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4I
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4I

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4F
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4F

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-2

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-2

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-2

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)(1)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-2

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1B

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-1A

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/815/tableOfContent

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480237/815-40-50-5

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5C
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-5C

+ Details

Document and Entity Information - shares	6 Months Ended
Document and Entity Information - shares	Jun. 30, 2026	Aug. 10, 2026
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2026
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q2
Document Quarterly Report	true
Document Transition Report	false
Entity Registrant Name	4D Molecular Therapeutics, Inc.
Entity Central Index Key	0001650648
Entity Current Reporting Status	Yes
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Interactive Data Current	Yes
Entity File Number	001-39782
Entity Tax Identification Number	47-3506994
Entity Address, Address Line One	5858 Horton Street #455
Entity Address, City or Town	Emeryville
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94608
City Area Code	(510)
Local Phone Number	505-2680
Entity Incorporation, State or Country Code	DE
Title of 12(b) Security	Common Stock, par value $0.0001 per share
Trading Symbol	FDMT
Security Exchange Name	NASDAQ
Common Stock [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		55,244,211
Pre-funded Warrants [Member]
Document Information [Line Items]
Entity Common Stock, Shares Outstanding		16,935,665

License Arrangements

6 Months Ended

Jun. 30, 2026

License Arrangements [Abstract]

License Arrangements

7. License Arrangements

Aevitas Therapeutics, Inc. and The Trustees of the University of Pennsylvania

On April 21, 2023, the Company entered into an agreement (the “Aevitas Agreement”) with Aevitas Therapeutics, Inc. (“Aevitas”), pursuant to which the Company acquired all of Aevitas’ worldwide rights to short-form human complement factor H (sCFH), which the Company plans to use for its 4D-175 product candidate research program. The asset purchase was accounted for as an asset acquisition. As consideration for the Aevitas Agreement, the Company shall pay Aevitas up to approximately $144.1 million in cash upon certain late-stage milestones being achieved, including $7.2 million for development milestones, $68.0 million for regulatory milestones and $68.9 million for sales milestones plus royalties in the low single digits range on sales of 4D-175. In addition, as part of the Aevitas Agreement, the Company was assigned a License Agreement for sCFH with the Trustees of the University of Pennsylvania, under which the Company shall pay the University of Pennsylvania up to approximately $41.6 million in cash upon certain late-stage milestones being achieved, including $1.9 million development, $21.5 million regulatory and $18.2 million sales milestones plus royalties in the low single digits range on sales of 4D-175. No upfront consideration was paid under the Aevitas Agreement.

As of June 30, 2026, the Company has not recorded a liability related to contingent consideration for future milestone and royalty payments to either Aevitas or the University of Pennsylvania, as the achievement of such milestones has not occurred and was not deemed probable and product sales have not commenced.

Regents of the University of California

The Company has exclusive, worldwide license agreements (the “UC Agreements”) with the Regents of the University of California (the “UC Regents”) relating to the use of certain patents and intellectual property surrounding its core technologies, including Therapeutic Vector Evolution. Pursuant to each of the UC Agreements executed prior to January 2019, the Company was obligated to pay a (i) non-refundable license fee of $5,000 upon execution, (ii) a non-refundable license fee of $5,000 each year thereafter, until sales of a licensed product are made and royalties are paid to the UC Regents, (iii) reimbursement of domestic and foreign patent filing, prosecution and maintenance fees, and (iv) either $50,000 or issuance of a 3% equity interest in the Company upon the closing of the first qualified financing at the option of the UC Regents. The Company’s first qualified financing occurred in 2015 and at the election of the UC Regents, the Company issued the UC Regents in January 2016 an amount of common stock equal to 6% of the equity interests in the Company pursuant to the applicable clause in each of the UC Agreements.

Pursuant to an agreement with the UC Regents executed in January 2019 the Company paid a non-refundable license fee of $50,000 to the UC Regents upon execution of the agreement. The Company is obligated to pay a non-refundable license fee of $5,000 on the one-year anniversary of the contract effective date and each year thereafter, until sales of a licensed product are made and royalties are paid to the UC Regents.

In addition, the Company is obligated to make certain contingent payments including (i) development milestones up to $3.1 million, (ii) low single digit royalties on the net sales of its developed products that consist of a minimum annual royalty of up to $0.1 million per year for the term of the agreement beginning in the first calendar year after the year in which net sales first occurred, and (iii) sublicense consideration in the mid-teens to the mid-twenties-range on any future sublicensing arrangements the Company may enter into with third-party licensees.

As of June 30, 2026, the Company has not recorded a liability related to contingent consideration for future milestone and royalty payments to UC Regents, as the achievement of such milestones has not occurred and was not deemed probable and product sales have not commenced.

Long Term Debt - Summary of Carrying Value of Hercules Loan Facility (Details) - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Debt Instrument [Line Items]
Long-term debt, net	$ 19,587	$ 0
Hercules Loan Facility \| Hercules Capital, Inc
Debt Instrument [Line Items]
Principal outstanding	20,000
Less: unamortized discount and debt issuance costs	(413)
Long-term debt, net	$ 19,587

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-2

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-4

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-04(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-3

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 55
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482949/835-30-55-8

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69B

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69C
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69C

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69E
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69E

Reference 12: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 55
-Paragraph 69F
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481568/470-20-55-69F

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 15: http://www.xbrl.org/2003/role/exampleRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1B
-Subparagraph (h)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1B

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1D
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1D

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1E
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1E

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1F
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1F

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1I
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481139/470-20-50-1I

Reference 30: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

Reference 31: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 835
-SubTopic 30
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482900/835-30-50-1

+ Details

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References + Details

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Jun. 30, 2026	Mar. 31, 2026	Jun. 30, 2025	Mar. 31, 2025	Jun. 30, 2026	Jun. 30, 2025
Pay vs Performance Disclosure
Net Income (Loss)	$ (72,936)	$ (68,760)	$ (54,658)	$ (47,972)	$ (141,696)	$ (102,630)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 946
-SubTopic 830
-Name Accounting Standards Codification
-Section 55
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479168/946-830-55-10

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-4

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 21
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-21

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 220
-SubTopic 40
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476153/220-40-55-14

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-4

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479857/480-10-S50-3

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S45
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479887/480-10-S45-3

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 480
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 3A
-Subparagraph (24)(d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480244/480-10-S99-3A

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 105
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 9
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479343/105-10-65-9

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 65
-Paragraph 17
-Subparagraph (d)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480336/718-10-65-17

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-6

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-9

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 805
-SubTopic 60
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147476176/805-60-65-1

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-SubTopic 323
-Name Accounting Standards Codification
-Section 65
-Paragraph 2
-Subparagraph (g)(3)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478666/740-323-65-2

Reference 19: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482765/220-10-50-6

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-3

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-1

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 40
-Name Accounting Standards Codification
-Section 65
-Paragraph 1
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480175/815-40-65-1

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-8

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 250
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 11
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483443/250-10-50-11

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section 45
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479105/946-220-45-7

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(9))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 3
-Subparagraph (SX 210.6-09(1)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-3

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 34: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 36: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 37: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 38: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 39: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 40: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 41: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 42: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 43: http://www.xbrl.org/2003/role/disclosureRef
-Topic 260
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 60B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482689/260-10-45-60B

Reference 44: http://www.xbrl.org/2003/role/disclosureRef
-Topic 205
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-7

Reference 45: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 28
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-28

Reference 46: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1A
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1A

Reference 47: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 1B
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482790/220-10-45-1B

Reference 48: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 20
-Name Accounting Standards Codification
-Section 65
-Paragraph 4
-Subparagraph (f)(4)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481538/470-20-65-4

Reference 49: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478524/942-220-S99-1

+ Details

Stock-based Compensation - Summary of Stock Options Activity (Details)	6 Months Ended
	Jun. 30, 2026 shares
Share-Based Payment Arrangement [Abstract]
Number of Shares Underlying Outstanding Options, Balances at December 31, 2025	9,412,808
Number of Shares Underlying Outstanding Options, granted	3,176,795
Number of Shares Underlying Outstanding Options, exercised	(217,393)
Number of Shares Underlying Outstanding Options, expired	(341,964)
Number of Shares Underlying Outstanding Options, forfeited	(293,098)
Number of Shares Underlying Outstanding Options, Balances at June 30, 2026	11,737,148
Number of Shares Underlying Outstanding Options, Options exercisable at June 30, 2026	6,081,392
Number of Shares Underlying Outstanding Options, Options vested and expected to vest at June 30, 2026	11,737,148

Long Term Debt - Additional Information (Details) - Hercules Capital, Inc - Hercules Loan Facility - USD ($)		1 Months Ended	6 Months Ended
	Jun. 24, 2026	Jun. 30, 2026	Jun. 30, 2026
Debt Instrument [Line Items]
Principal outstanding		$ 20,000,000	$ 20,000,000
Percentage of facility fee for subsequent borrowings		1.00%
Debt instrument, maturity date		Jun. 01, 2031
Debt instrument, capped interest rate		0.75%
Debt interest rate per annum		8.75%	8.75%
Initial facility fee		$ 500,000
Payment of debt issuance costs		$ 2,100,000
Term Loans Aggregate Principal Amount Tranches Initial
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000
Term Loans Aggregate Principal Amount Tranches Through June 15, 2027
Debt Instrument [Line Items]
Maximum borrowing capacity	50,000,000
Current borrowing capacity	20,000,000
Remaining borrowing capacity	$ 30,000,000
Debt instrument term	29 months
Debt instrument extended term	30 months
Debt instrument, basis spread on variable rate	2.00%	2.50%
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	us-gaap:PrimeRateMember	us-gaap:PrimeRateMember
Debt interest rate per annum	8.75%	9.25%	9.25%
Debt instrument, frequency of periodic payment			The Company is required to make monthly interest-only payments for borrowings under the initial tranche of $50.0 million for a period of 29 months, which may be extended by up to an additional 30 months upon achievement of certain clinical, regulatory, financing and capitalization milestones.
Term Loans Aggregate Principal Amount Tranches Five
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 50,000,000	$ 50,000,000
Maximum
Debt Instrument [Line Items]
Aggregate principal amount of debt		$ 200,000,000	200,000,000
Percentage of end-of-term charge		6.50%
Percentage of prepayment premium		3.00%
Maximum \| Term Loans Aggregate Principal Amount Tranches Three
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 100,000,000	100,000,000
Maximum \| Term Loans First Four Tranches
Debt Instrument [Line Items]
Aggregate principal amount of debt		$ 150,000,000	150,000,000
Minimum
Debt Instrument [Line Items]
Percentage of end-of-term charge		3.70%
Percentage of prepayment premium		1.00%
Prepaid and Other Current Assets
Debt Instrument [Line Items]
Debt issuance costs		$ 2,200,000	2,200,000
Other Assets
Debt Instrument [Line Items]
Debt issuance costs		2,200,000	2,200,000
Accounts Payable
Debt Instrument [Line Items]
Unpaid debt issuance costs		$ 1,900,000	$ 1,900,000

Net Loss Per Share, Basic and Diluted (Tables)

6 Months Ended

Jun. 30, 2026

Earnings Per Share [Abstract]

Computation of Basic and Diluted Net Loss Per Share

The following table sets forth the computation of basic and diluted net loss per share (in thousands, except share and per share data):


	Three Months Ended June 30,						Six Months Ended June 30,
	2026			2025			2026			2025
Numerator
Net loss	$	(72,936	)	$	(54,658	)	$	(141,696	)	$	(102,630	)
Denominator
Weighted-average shares outstanding used in computing net loss per share, basic and diluted		70,272,018			55,927,091			69,175,213			55,836,075
Net loss per share, basic and diluted	$	(1.04	)	$	(0.98	)	$	(2.05	)	$	(1.84	)

Outstanding Shares of Potentially Dilutive Securities Excluded from Computation of Diluted Net Loss Per Share


	June 30,
	2026		2025
Stock options issued and outstanding		11,737,148		10,445,483
Restricted stock units subject to future vesting		1,816,742		725,101
2020 ESPP		303,189		549,661
Common stock warrants		30,000		30,000
Total		13,887,079		11,750,245

Summary of Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2026

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates and Judgments

Long Term Debt

Long-Term Debt

Segment Information

Concentration of Credit Risk

The Company’s partners in collaboration and license agreements who represent 10% or more of the Company’s total revenue are as follows:


	Three Months Ended		Six Months Ended
	June 30,		June 30,
	2026	2025	2026	2025
Customer A	98%	0%	97%	0%
Customer B	*	100%	*	100%
Total	98%	100%	97%	100%

______________

* Less than 10%

The Company’s total revenues by geographic region, based on the location of the customer, are as follows (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2026		2025		2026		2025
Japan	$	3,691	$	—	$	6,648	$	—
United States		90		15		180		29
Total revenue	$	3,781	$	15	$	6,828	$	29

Other Risks and Uncertainties

Recently Issued Accounting Pronouncements Not Yet Adopted

Recently Issued Accounting Pronouncements Adopted

- Definition

Disclosure of accounting policy for segment reporting.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (bb)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 54
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-54

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 36
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-36

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 47
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-47

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 29
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-29

+ Details

- Definition

Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478671/942-235-S50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-12

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-9

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482836/275-10-55-6

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-4

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (b)
-SubTopic 10
-Topic 275
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-SubTopic 10
-Topic 275
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-1

+ Details

Condensed Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Condensed Statements of Operations - USD ($) $ in Thousands	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Revenue:
Collaboration and license revenue	$ 3,781	$ 15	$ 6,828	$ 29
Operating expenses:
Research and development	68,282	47,951	133,262	88,650
General and administrative	12,524	11,520	24,212	24,456
Total operating expenses	80,806	59,471	157,474	113,106
Loss from operations	(77,025)	(59,456)	(150,646)	(113,077)
Other income (expense):
Interest income	4,255	4,859	9,119	10,441
Other income (expense), net	(166)	(61)	(169)	6
Total other income, net	4,089	4,798	8,950	10,447
Net loss	$ (72,936)	$ (54,658)	$ (141,696)	$ (102,630)
Net loss per share, basic	$ (1.04)	$ (0.98)	$ (2.05)	$ (1.84)
Net loss per share, diluted	$ (1.04)	$ (0.98)	$ (2.05)	$ (1.84)
Weighted-average shares outstanding used in computing net loss per share, basic	70,272,018	55,927,091	69,175,213	55,836,075
Weighted-average shares outstanding used in computing net loss per share, diluted	70,272,018	55,927,091	69,175,213	55,836,075

Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2026

Share-Based Payment Arrangement [Abstract]

Summary of Restricted Stock Units (RSU)

The following table summarizes the RSU activity:


	Number of Shares
Unvested balance at December 31, 2025		744,770
Awarded		1,290,476
Vested		(100,241	)
Canceled/Forfeited		(118,263	)
Unvested balance at June 30, 2026		1,816,742

Summary of Stock Options Activity

The following table summarizes the stock options activity:


	Number of Shares Underlying Outstanding Options
Balances at December 31, 2025		9,412,808
Options granted		3,176,795
Options exercised		(217,393	)
Options expired		(341,964	)
Options forfeited		(293,098	)
Balances at June 30, 2026		11,737,148
Options exercisable at June 30, 2026		6,081,392
Options vested and expected to vest at June 30, 2026		11,737,148

Summary of Assumptions Used in Black-Scholes Valuation Model to Estimate Fair Value of Stock Options

The fair value of the Company’s stock options was estimated using the following assumptions:


	Three Months Ended June 30,		Six Months Ended June 30,
	2026	2025	2026	2025
Expected term	5.9 - 6.1 years	5.9 years	5.9 - 6.1 years	5.9 - 6.1 years
Expected volatility	85.9% - 87.3%	86.5% - 88.9%	85.9% - 89.0%	84.9% - 88.9%
Risk-free interest rate	4.0% - 4.3%	4.1%	3.8% - 4.3%	4.1% - 4.6%
Expected dividend yield	—%	—%	—%	—%

Summary of Stock-based Compensation Expense for Employees and Nonemployees by Function

The following table is a summary of stock-based compensation expense incurred for employees and nonemployees by function (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Research and development	$	2,720	$	2,498	$	4,652	$	6,479
General and administrative		3,164		2,460		5,685		5,465
Total stock-based compensation expense	$	5,884	$	4,958	$	10,337	$	11,944

Fair Value Measurements and Marketable Securities - Summary of Changes in Fair Value of Level 3 Financial Instruments (Details) - Derivative Liability $ in Thousands	6 Months Ended
	Jun. 30, 2026 USD ($)
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 358
Change in fair value	$ 26
Fair Value, Recurring Basis, Unobservable Input Reconciliation, Liability, Gain (Loss), Statement of Income [Extensible List]	Other income (expense), net
Ending Balance	$ 384

Commitments and Contingencies - Summary of Supplemental Information Related to Operating Leases (Details)	Jun. 30, 2026	Dec. 31, 2025
Commitments and Contingencies Disclosure [Abstract]
Weighted-average remaining lease term (in years)	4 years 4 months 24 days	4 years 9 months 18 days
Weighted-average discount rate	10.80%	10.80%

Segment Information - Additional Information (Details)	6 Months Ended
Segment Information - Additional Information (Details)	Jun. 30, 2026 Segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description	The Company's CODM is its Chief Executive Officer who assesses performance for the business and decides how to allocate resources based on net loss that also is reported on the statements of operations. In making this assessment, the CODM reviews and evaluates net loss to monitor budget versus actual results and to analyze cash flows for purposes of allocating resources and assessing financial performance.

Common Stock - Schedule of Common Share Reserved for Future Issuance (Details) - shares	Jun. 30, 2026	Dec. 31, 2025	Dec. 31, 2020
Class Of Stock [Line Items]
Common stock reserved	33,517,749	23,212,452
2020 Equity Incentive Award Plan and 2025 Employment Inducement Award Plan
Class Of Stock [Line Items]
Common stock reserved	2,607,822	2,506,434
2020 Employee Stock Purchase Plan
Class Of Stock [Line Items]
Common stock reserved	390,372	182,775	252,337
Exercise of Stock Options Issued and Outstanding and Future Vesting of Restricted Stock Units
Class Of Stock [Line Items]
Common stock reserved	13,553,890	10,157,578
Pre-funded Warrants
Class Of Stock [Line Items]
Common stock reserved	16,935,665	10,335,665
Common Stock Warrants
Class Of Stock [Line Items]
Common stock reserved	30,000	30,000

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Summary of Significant Accounting Policies - Schedule of Revenues by Geographic Region (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Disaggregation of Revenue [Line Items]
Revenues	$ 3,781	$ 15	$ 6,828	$ 29
Japan
Disaggregation of Revenue [Line Items]
Revenues	3,691	0	6,648	0
United States
Disaggregation of Revenue [Line Items]
Revenues	$ 90	$ 15	$ 180	$ 29

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 7
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-7

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479806/606-10-50-5

Reference 3: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 6: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (e)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 8: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 606
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 91
-Subparagraph (g)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479777/606-10-55-91

+ Details

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4A
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-4A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478671/942-235-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 41
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-41

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 42
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-42

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 825
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 28
-Subparagraph (f)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482907/825-10-50-28

Reference 9: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 14
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-14

Reference 10: http://www.xbrl.org/2003/role/exampleRef
-Topic 944
-SubTopic 605
-Name Accounting Standards Codification
-Section 55
-Paragraph 11
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477548/944-605-55-11

Reference 11: http://www.xbrl.org/2003/role/exampleRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 48
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482785/280-10-55-48

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Topic 270
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482964/270-10-50-1

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (ee)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 14: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 15: http://fasb.org/us-gaap/role/ref/otherTransitionRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 32
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-32

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 17: http://www.xbrl.org/2003/role/disclosureRef
-Topic 323
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481687/323-10-50-3

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 19: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1A

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 25: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480097/470-10-S99-1B

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 30
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-30

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 40
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-40

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 22
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-22

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

+ Details

Research and Collaboration Arrangements - Summary of Collaboration and License Revenue and Deferred revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	$ 3,781	$ 15	$ 6,828	$ 29
Collaboration and License Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	3,781	15	6,828	29
Collaboration and License Revenue \| Otsuka Pharmaceutical Co., Ltd
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	3,691	0	6,648	0
Collaboration and License Revenue \| Cystic Fibrosis Foundation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue	90	$ 15	180	$ 29
Deferred Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	3,315		3,315		$ 1,105
Deferred Revenue \| Otsuka Pharmaceutical Co., Ltd
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	2,390		2,390		0
Deferred Revenue \| Cystic Fibrosis Foundation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 925		$ 925		$ 1,105

- Definition

+ References

+ Details

Net Loss Per Share, Basic and Diluted - Additional Information (Details) - $ / shares	Jun. 30, 2026	Jan. 22, 2026	Dec. 31, 2020	May 31, 2018
Class of Warrant or Right [Line Items]
Exercise price			$ 18	$ 3.19
Common Stock \| Pre-funded Warrants
Class of Warrant or Right [Line Items]
Nominal exercise price	$ 0.0001
Exercise price	$ 0.0001	$ 0.0001

Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025
Statement of Comprehensive Income [Abstract]
Net loss	$ (72,936)	$ (54,658)	$ (141,696)	$ (102,630)
Other comprehensive loss:
Net unrealized gain (loss) on marketable securities	(266)	5	(1,173)	108
Total comprehensive loss	$ (73,202)	$ (54,653)	$ (142,869)	$ (102,522)

- Definition

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

+ References + Details

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Common Stock - Additional Information (Details) - USD ($)	1 Months Ended				6 Months Ended	12 Months Ended
	Oct. 31, 2025	Jun. 30, 2024	Oct. 31, 2021	Apr. 30, 2020	Jun. 30, 2026	Dec. 31, 2025
Class of Stock [Line Items]
Common stock, shares authorized					300,000,000	300,000,000
Common stock, par value					$ 0.0001	$ 0.0001
Common stock voting rights					one vote per share
Common stock dividend					$ 0
Stock Purchase Agreement \| CFF \| Common Stock
Class of Stock [Line Items]
Number of shares sold and issued	776,398
Issuance of common stock for the offering program, net of issuance costs	$ 7,500,000
Additional investment amount subject to specific clinical milestone and at option of company	$ 3,600,000
Funding Agreement \| CFF
Class of Stock [Line Items]
Additional funding upon acceptance of investigational New Drug application			$ 4,000,000	$ 4,000,000
Additional investment in cash			$ 4,000,000
Funding Agreement \| CFF \| Common Stock
Class of Stock [Line Items]
Number of shares sold and issued			125,715
Funding Agreement \| CFF \| Series C Redeemable Convertible Preferred Stock
Class of Stock [Line Items]
Investment in redeemable convertible preferred stock financing				$ 10,000,000
Sales Agreement \| Leerink Partners LLC
Class of Stock [Line Items]
Number of shares sold and issued					3,518,472	1,175,000
Aggregate net proceeds, after deducting underwriting discounts and commissions and offering costs					$ 31,600,000	$ 9,600,000
Maximum \| Sales Agreement \| Leerink Partners LLC
Class of Stock [Line Items]
Aggregate gross sales proceeds from common stock		$ 250,000,000

Fair Value Measurements and Marketable Securities (Tables)

6 Months Ended

Jun. 30, 2026

Fair Value Measurements and Marketable Securities [Abstract]

Fair Value Hierarchy for Financial Assets and Financial Liabilities Measured at Fair Value on Recurring Basis

The following tables represent the Company’s fair value hierarchy for financial assets and financial liabilities measured at fair value on a recurring basis (in thousands):


	Amortized Cost Basis		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value as of June 30, 2026		Cash and Cash Equivalents		Current Marketable Securities		Non-Current Marketable Securities
Assets
Cash	$	29,718	$	—	$	—		$	29,718	$	29,718	$	—	$	—
Level 1:
Money market funds		34,659		—		—			34,659		34,659		—		—
Level 2:
Certificates of deposit		20,892		4		(9	)		20,887		—		20,887		—
Commercial paper		54,813		5		(52	)		54,766		5,995		48,771		—
U.S. Treasuries		92,469		10		(216	)		92,263		—		67,884		24,379
Corporate bonds		198,524		51		(239	)		198,336		—		153,420		44,916
Subtotal		366,698		70		(516	)		366,252		5,995		290,962		69,295
Total	$	431,075	$	70	$	(516	)	$	430,629	$	70,372	$	290,962	$	69,295


	Amortized Cost Basis		Gross Unrealized Gains		Gross Unrealized Losses			Fair Value as of December 31, 2025		Cash and Cash Equivalents		Current Marketable Securities		Non-Current Marketable Securities
Assets
Cash	$	10,696	$	—	$	—		$	10,696	$	10,696	$	—	$	—
Level 1:
Money market funds		39,570		—		—			39,570		39,570		—		—
Level 2:
Certificates of deposit		35,986		37		—			36,023		—		36,023		—
Commercial paper		63,875		48		—			63,923		5,479		58,444		—
U.S. Treasuries		76,920		153		—			77,073		—		63,589		13,484
Corporate bonds		286,260		492		(3	)		286,749		4,496		184,358		97,895
Subtotal		463,041		730		(3	)		463,768		9,975		342,414		111,379
Total	$	513,307	$	730	$	(3	)	$	514,034	$	60,241	$	342,414	$	111,379

Summary of Changes in Fair Value of Level 3 Financial Instruments

The following table sets forth a summary of the changes in the fair value of the Company's Level 3 financial instrument (in thousands):


	Derivative Liability
Balance as of December 31, 2025	$	358
Change in fair value		26
Balance as of June 30, 2026	$	384

The change in fair value above is included in other income (expense), net, in the Company's condensed statements of operations.

Summary of Aggregate Fair Values of Marketable Securities with Unrealized Losses and Gains

Aggregate fair values of marketable securities with unrealized losses and gains were as follows as of June 30, 2026 and December 31, 2025 (in thousands):


	June 30, 2026		December 31, 2025
Aggregate fair value of marketable securities in a continuous loss position for less than twelve months	$	260,917	$	15,449
Aggregate fair value of marketable securities in a continuous loss position for more than twelve months		—		1,951
Aggregate fair value of marketable securities in unrealized gain position		105,335		446,368
Total marketable securities	$	366,252	$	463,768

Common Stock

6 Months Ended

Jun. 30, 2026

Equity [Abstract]

Common Stock

11. Common Stock

As of June 30, 2026 and December 31, 2025, the Company’s certificate of incorporation authorized the Company to issue 300,000,000 shares of common stock, at the par value of $0.0001 per share. The holder of each share of common stock is entitled to one vote per share.

Common stockholders are entitled to dividends, if and when declared by the board of directors. To date, no dividends on common stock have been declared by the board of directors.

The Company has reserved common stock, on an as-converted basis, for future issuance as follows:


	June 30, 2026		December 31, 2025
Issuance of common stock under the 2020 Equity Incentive Award Plan and 2025 Employment Inducement Award Plan		2,607,822		2,506,434
Issuance of common stock under the 2020 Employee Stock Purchase Plan		390,372		182,775
Exercise of stock options issued and outstanding and future vesting of restricted stock units		13,553,890		10,157,578
Exercise of pre-funded warrants		16,935,665		10,335,665
Exercise of common stock warrants		30,000		30,000
Total common stock reserved for future issuance		33,517,749		23,212,452

Funding Agreement with CFF — In April 2020, CFF made a $10.0 million investment in the Company’s Series C redeemable convertible preferred stock financing. In return for the investment, CFF received shares of Series C redeemable convertible preferred stock, and the Company and CFF entered into a Funding Agreement (the “Funding Agreement”). Pursuant to the terms of the Funding Agreement, except in the event of a technical failure, the $10.0 million received from CFF will be used to advance the development program for 4D-710, the Company’s lead product candidate in cystic fibrosis, or any other therapeutic approved by the Program Advisory Group (“PAG”) to alleviate pulmonary complications of cystic fibrosis (the “Funding Agreement Product”).

CFF committed to provide an additional $4.0 million of funding upon acceptance of an IND application or its equivalent to allow for human testing of the Funding Agreement Product (“Acceptance”).

In October 2021, the IND was cleared by the U.S. Food and Drug Administration and CFF made the additional investment of $4.0 million in cash for the issuance of 125,715 shares of the Company’s common stock to CFF.

The Company was committed to providing an amount equal to the funding provided by CFF to be used solely to advance the Funding Agreement Product. As of June 30, 2026, the funding commitment has been fulfilled. Under the terms of the Funding Agreement, neither the $10.0 million investment in the Series C redeemable convertible preferred stock, which converted to common stock as of December 31, 2020, nor the $4.0 million of funding upon Acceptance are restricted as to withdrawal or usage.

CFF purchased 776,398 shares of the Company's common stock for $7.5 million in October 2025. The Company will use the proceeds of this investment to support continued development of 4D-710. The Company also agreed with CFF to form a Joint Steering Committee, with senior clinical development and regulatory expertise to enhance strategic planning, guidance, and coordination of 4D-710’s development. This agreement between CFF and the Company entered into in October 2025 also provides that CFF will invest an additional $3.6 million in exchange for shares of the Company’s common stock subject to achievement of specific clinical milestones and at the option of the Company. This agreement between the Company and CFF entered into in October 2025 does not modify the prior agreements with CFF.

Sales Agreement with Leerink Partners LLC (“Leerink”) — In June 2024, the Company entered into a Sales Agreement (the “Leerink Sales Agreement”) with Leerink as sales agent to sell shares of the Company's common stock, from time to time, with aggregate gross sales proceeds of up to $250.0 million pursuant to a Registration Statement on Form S-3 that the Company filed with the SEC in February 2024, and subsequently amended in February 2025, as an “at-the-market” offering under the Securities Act. For the year ended December 31, 2025, 1,175,000 shares of the Company's common stock were sold pursuant to the Leerink Sales Agreement for net proceeds to the Company of $9.6 million, after deducting issuance costs. For the six months ended June 30, 2026, 3,518,472 shares were sold pursuant to the Leerink Sales Agreement for net proceeds to the Company of $31.6 million, after deducting issuance costs.

- Definition

The entire disclosure for equity.

+ References

+ Details

401(K) Plan

6 Months Ended

Jun. 30, 2026

Retirement Benefits [Abstract]

401(K) Plan

19. 401(k) Plan

In 2014, the Company adopted a 401(k) plan for all employees who have met certain eligibility requirements. The 401(k) plan allows employees to make pre-tax and post-tax contributions up to the maximum allowable amount set by the Internal Revenue Service. The Company made contributions to the 401(k) plan for all eligible participants and recorded contribution expenses of $0.6 million and $1.2 million for the three and six months ended June 30, 2026, respectively, and $0.5 million and $1.1 million for the three and six months ended June 30, 2025, respectively.

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 70,372	$ 60,241
Marketable securities	290,962	342,414
Collaboration receivable	4,611	0
Prepaid expenses and other current assets	17,012	10,479
Total current assets	382,957	413,134
Marketable securities, long-term	69,295	111,379
Property and equipment, net	12,379	14,867
Operating lease right-of-use assets, net	16,548	18,143
Other non-current assets	11,436	9,188
Total assets	492,615	566,711
Current liabilities
Accounts payable	12,522	11,159
Accrued and other current liabilities	25,431	26,874
Deferred revenue	360	360
Deferred grant reimbursements	3,986	0
Operating lease liabilities, current portion	5,374	5,592
Total current liabilities	47,673	43,985
Deferred revenue, net of current portion	2,955	745
Derivative liability	384	358
Operating lease liabilities, long-term portion	14,256	15,821
Long-term debt, net	19,587	0
Other liabilities	101	138
Total liabilities	84,956	61,047
Commitments and contingencies (Note 8)
Stockholders’ equity
Preferred stock, $0.0001 par value, 10,000,000 shares authorized at June 30, 2026 and December 31, 2025; no shares issued and outstanding at June 30, 2026 and December 31, 2025	0	0
Common stock, $0.0001 par value, 300,000,000 shares authorized at June 30, 2026 and December 31, 2025; 55,214,097 and 57,607,874 shares issued and outstanding at June 30, 2026 and December 31, 2025, respectively	6	6
Additional paid-in-capital	1,266,099	1,221,235
Accumulated other comprehensive gain (loss)	(446)	727
Accumulated deficit	(858,000)	(716,304)
Total stockholders’ equity	407,659	505,664
Total liabilities and stockholders’ equity	$ 492,615	$ 566,711

Common Stock (Tables)

6 Months Ended

Jun. 30, 2026

Equity [Abstract]

Schedule of Common Shares Reserved for Future Issuance

The Company has reserved common stock, on an as-converted basis, for future issuance as follows:


	June 30, 2026		December 31, 2025
Issuance of common stock under the 2020 Equity Incentive Award Plan and 2025 Employment Inducement Award Plan		2,607,822		2,506,434
Issuance of common stock under the 2020 Employee Stock Purchase Plan		390,372		182,775
Exercise of stock options issued and outstanding and future vesting of restricted stock units		13,553,890		10,157,578
Exercise of pre-funded warrants		16,935,665		10,335,665
Exercise of common stock warrants		30,000		30,000
Total common stock reserved for future issuance		33,517,749		23,212,452

Accrued and Other Current Liabilities (Tables)

6 Months Ended

Jun. 30, 2026

Payables and Accruals [Abstract]

Summary of Accrued and Other Current Liabilities

Accrued and other current liabilities consisted of the following (in thousands):


	June 30, 2026		December 31, 2025
Payroll and related expenses	$	7,818	$	13,806
Accrued clinical and preclinical study costs		14,014		10,273
Consulting and outside services		3,475		2,666
Other accrued expenses		124		129
Total accrued and other current liabilities	$	25,431	$	26,874

Commitments and Contingencies (Tables)

6 Months Ended

Jun. 30, 2026

Commitments and Contingencies Disclosure [Abstract]

Summary of Components of Lease Expense

The following table summarizes the components of lease expense, which are included in operating expenses in the Company’s condensed statements of operations (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Operating lease cost	$	1,344	$	1,344	$	2,688	$	2,688
Variable lease cost		678		648		1,355		1,422
Total	$	2,022	$	1,992	$	4,043	$	4,110

Summary of Supplemental Information Related to Operating Leases

The following table summarizes supplemental information related to operating leases:


	June 30, 2026			December 31, 2025
Weighted-average remaining lease term (in years):		4.4			4.8
Weighted-average discount rate:		10.8	%		10.8	%

Summary of Maturities of Lease Liabilities

The following table summarizes the maturities of lease liabilities as of June 30, 2026 (in thousands):


2026 (remaining six months)	$	2,725
2027		5,350
2028		5,510
2029		5,675
2030		5,455
Total future minimum lease payments		24,715
Less: Amount representing interest		(5,085	)
Present value of future minimum lease payments		19,630
Less: Current portion of operating lease liabilities		(5,374	)
Long-term portion of operating lease liabilities	$	14,256