0000950170-25-034644 | 10-K | XBRL Viewer

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License Agreements - Additional Information (Detail)		1 Months Ended				3 Months Ended	12 Months Ended
License Agreements - Additional Information (Detail)	Jun. 29, 2023 EUR (€)	Dec. 31, 2024 USD ($)	Feb. 28, 2022 USD ($)	Feb. 28, 2021 USD ($)	Oct. 31, 2020 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2015 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research and development expense							$ 96,431,000	$ 76,563,000
License agreement termination expiration term for licensed product											10 years
License agreement termination expiration term											5 years
Maugeri License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront license fee \| €	€ 1,500,000
Agreement Termination Notice Period	60 days
Maugeri License Agreement [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cumulative developmental, regulatory, and commercial milestone payments \| €	€ 15,000,000
Cumulative sales milestone payments \| €	€ 15,000,000
Other Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment upon achievement of certain milestones		$ 18,100,000				$ 18,100,000	18,100,000
Mayo [Member] \| Mayo Clinic Collaboration and License Agreement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
One-time upfront payment in cash						600,000
One-time upfront payment in shares						2,000,000
Cumulative developmental milestones		5,000,000
Cumulative regulatory milestones		2,000,000
Annual know-how access fee		600,000
Mayo [Member] \| Mayo Clinic Collaboration and License Agreement [Member] \| Maximum [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Cumulative sales milestone payments		18,000,000
University of Washington [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum milestone payment to be made												$ 1,000,000
Milestone payment upon achievement of certain milestones					$ 3,400,000
Amount payable in connection with execution of collaboration agreement					$ 400,000
Research and development expense							100,000	0
University of Missouri [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum milestone payment to be made												$ 1,000,000
Milestone payment upon achievement of certain milestones		1,900,000				1,900,000	1,900,000
Research and development expense							$ 100,000	100,000
Milestone payment			$ 1,300,000	$ 800,000
University of Missouri [Member] \| Ultragenyx [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Amount payable in connection with execution of collaboration agreement									$ 1,300,000	$ 800,000
University of Florida License Agreements [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Maximum milestone payment to be made											$ 2,900,000
License agreements termination description							Each of the agreements terminates on a licensed product-by-licensed product basis on the later of: (i) expiration of the patent rights covering such licensed product or (ii) ten years from the first commercial sale of such licensed product.
Maximum milestone payment upon achievement of specified commercial milestone events		$ 27,000,000				$ 27,000,000	$ 27,000,000	$ 8,500,000
University of Florida License Agreements [Member] \| AavantiBio, Inc [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment											$ 100,000

FA212 Asset Acquisition - Additional Information (Detail) - USD ($)		12 Months Ended
	Sep. 19, 2024	Dec. 31, 2024
Asset Acquisition [Line Items]
Derivative liabilities at fair value	$ 3,400,000	$ 3,150,000
FA212 LLC [Member]
Asset Acquisition [Line Items]
Agreement date	Sep. 19, 2024
Upfront payment	$ 1,000,000
Derivative liabilities at fair value	3,400,000	3,200,000
Aggregate acquisition cost		5,100,000
Transaction costs		700,000
Development milestone payable		5,000,000
Milestone liability payment		$ 5,000,000
FA212 LLC [Member] \| Maximum [Member]
Asset Acquisition [Line Items]
Development milestone payments	34,000,000
Cumulative sales milestone payments	21,000,000
Assumed contingent development milestone payments	4,200,000
Assumed regulatory milestone payments	13,000,000
Assumed cumulative sales milestone payments	$ 27,500,000

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Significant Accounting Policies [Line Items]
Restricted cash noncurrent	$ 1,952,000	$ 1,833,000
Income tax expense (benefit)	$ 0	$ 0
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Expected dividend yield	$ 0
Laboratory Equipment [Member]
Significant Accounting Policies [Line Items]
Useful life of asset	5 years
Computer Equipment [Member]
Significant Accounting Policies [Line Items]
Useful life of asset	3 years
Computer Software [Member]
Significant Accounting Policies [Line Items]
Useful life of asset	2 years
Furniture and Office Equipment [Member]
Significant Accounting Policies [Line Items]
Useful life of asset	5 years
Leasehold Improvements [Member]
Significant Accounting Policies [Line Items]
Property, Plant, and Equipment, Useful Life, Term, Description [Extensible Enumeration]	us-gaap:UsefulLifeTermOfLeaseMember

Insider Trading Policies and Procedures	12 Months Ended
Insider Trading Policies and Procedures	Dec. 31, 2024
Insider Trading Policies and Procedures [Line Items]
Insider Trading Policies and Procedures Adopted	true

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
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	$ 0.001	$ 0.001
Common stock, shares authorized	120,000,000	60,000,000
Common stock, shares issued	40,468,141	20,386,606
Common stock, shares outstanding	40,468,141	20,386,606

Consolidated Statements of Changes In Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Statement of Stockholders' Equity [Abstract]
Issuance costs	$ 4,407	$ 76
Pre-funded warrants issuance costs	704
Sales commissions	$ 471

Subsequent Events

12 Months Ended

Dec. 31, 2024

Subsequent Events [Abstract]

Subsequent Events

18. Subsequent Events

On February 19, 2025, the Company issued and sold 35,739,810 shares of its common stock at a price of $4.03 per share, and, to certain investors in lieu of shares of common stock, pre-funded warrants to purchase 13,888,340 shares of its common stock at a price of $4.029 per pre-funded warrant, in the February 2025 Offering. The Company received approximately $187.5 million of aggregate net proceeds from the February 2025 Offering, after deducting underwriting discounts and commissions and estimated offering costs.

Following the FDA's clearance of the Company's IND application for SGT-212 for the treatment of FA, a $5.0 million development milestone became payable to FA212. On February 28, 2025, the Company made the first milestone payment in the form of 975,496 shares of its common stock.

Income Taxes - Schedule of Net Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Tax loss carryforwards	$ 37,183	$ 16,622
Tax credit carryforwards	15,324	7,537
Deferred expenses	6,067	6,755
Accrued expenses	1,536	1,506
Stock compensation	9,986	8,496
Intangible assets	2,535	203
Capitalized R&D	63,087	57,133
Depreciation	0	672
Derivative liabilities	833
Other	53	80
Total deferred tax assets	136,604	99,004
Valuation allowance	(130,690)	(91,705)	$ (163,566)
Deferred tax liabilities:
Right-of-use asset	(5,570)	(7,299)
Depreciation	(344)
Total deferred tax liabilities	$ (5,914)	$ (7,299)

Property and Equipment

12 Months Ended

Dec. 31, 2024

Property, Plant and Equipment [Abstract]

Property and Equipment

7. Property and Equipment

Property and equipment consisted of the following:


	December 31,
	2024			2023
Furniture and fixtures	$	936		$	936
Laboratory equipment		14,404			16,137
Leasehold improvements		470			481
Computer equipment		764			842
Computer software		320			553
Construction in process		879			410
		17,773			19,359
Less accumulated depreciation		(13,026	)		(12,735	)
Total	$	4,747		$	6,624

Depreciation and amortization expense was $2.5 million and $2.6 million for the years ended December 31, 2024 and 2023, respectively. The Company recognized an impairment loss $0.4 million for the year ended December 31, 2023. No impairment loss was recognized during the year ended December 31, 2024.

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	$ 19,852	$ 10,161
Accrued Research and Development Expense [Member]
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	7,268	2,614
Accrued Compensation [Member]
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	6,221	5,948
Accrued Milestone Payment [Member]
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	5,000
Accrued Other and Other Current Liabilities [Member]
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	$ 1,363	$ 1,599

Segment Reporting

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

Segment Reporting

17. Segment Reporting

The Company has one reportable and one operating segment and manages its business activities primarily in North America and on a consolidated basis. The Company’s singular focus is on developing treatments through gene therapy and other means for patients with neuromuscular and cardiac diseases. All of the Company’s tangible assets are held in the United States.

The accounting policies of the Company are the same as those described in the summary of significant accounting policies.

The Company’s chief operating decision maker ("CODM") is its chief executive officer. The CODM assesses performance for the Company and decides how to allocate resources based on net loss as reported on the consolidated statements of operations. The annual budgeting process is the primary mechanism used to make these decisions. The financial information also helps in making performance assessments using budgeted versus actual results.

The following table presents segment expenses, other segment items, and segment net loss for the periods presented:


	Year Ended December 31,
	2024			2023
Segment Expenses:
SGT-003		15,197			20,856
SGT-501		17,223			3,200
External R&D other		10,580			7,907
Internal R&D expense(1)		21,705			21,798
External G&A expense		20,122			19,635
Internal G&A expense(1)		12,223			10,911
Other segment items(2)		32,678			19,945
Other income, net		(5,031	)		(8,237	)
Consolidated net loss		(124,697	)		(96,015	)


(1)	Internal expenses consisted primarily of payroll and related costs, temporary services, and travel and entertainment.
(2)	Other segment items primarily included equity-based compensation expense, other program costs, and depreciation and amortization expense

The measure of segment assets is reported on the balance sheet as total consolidated assets.

- 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.

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+ Details

Segment Reporting - Schedule of Segment Expenses, Other Segment Items, and Segment Net Loss (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Research and development expense		$ 96,431	$ 76,563
General and administrative expense		33,297	27,752
Equity-based compensation expense		10,519	7,625
Change in fair value of derivative liabilities	$ 4,750	(4,750)	0
Non-cash acquired in-process research and development		3,400	0
Depreciation and amortization expense		2,455	2,581
Interest income		(9,469)	(7,582)
Interest expense		340	440
Other income, net		652	1,095
Consolidated net loss		(124,697)	(96,015)
Operating segment [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Other segment items		32,678	19,945
Other income, net		(5,031)	(8,237)
Consolidated net loss		(124,697)	(96,015)
Operating segment [Member] \| SGT-003 [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Research and development expense		15,197	20,856
Operating segment [Member] \| SGT-501 [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Research and development expense		17,223	3,200
Operating segment [Member] \| External Research and Development Other [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Research and development expense, other		10,580	7,907
Operating segment [Member] \| Internal Research and Development Expense [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Research and development expense		21,705	21,798
Operating segment [Member] \| External General and Administrative Expense [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Research and development expense		20,122	19,635
Operating segment [Member] \| Internal General and Administrative Expense [Member]
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
General and administrative expense		$ 12,223	$ 10,911

Defined Contribution Plan - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Retirement Benefits [Abstract]
Company's contribution to the plan	$ 0.6	$ 0.6

Fair Value of Financial Assets and Liabilities - Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Sep. 19, 2024	Dec. 31, 2023
Financial assets
Total cash equivalents	$ 35,522		$ 62,398
Total available-for-sale securities	68,685		49,625
Total financial assets	104,207		112,023
Financial liabilities
Derivative liabilities	3,150	$ 3,400
Total financial liabilities	3,150
Money Market Funds [Member]
Financial assets
Total cash equivalents	18,088		62,141
Certificates of Deposit [Member]
Financial assets
Total cash equivalents			257
Treasury Bills [Member]
Financial assets
Total cash equivalents	17,434
Total available-for-sale securities	27,895		49,625
Government Bonds [Member]
Financial assets
Total available-for-sale securities	40,790
Level 2 [Member]
Financial assets
Total cash equivalents	35,522		62,398
Total available-for-sale securities	68,685		49,625
Total financial assets	104,207		112,023
Level 2 [Member] \| Money Market Funds [Member]
Financial assets
Total cash equivalents	18,088		62,141
Level 2 [Member] \| Certificates of Deposit [Member]
Financial assets
Total cash equivalents			257
Level 2 [Member] \| Treasury Bills [Member]
Financial assets
Total cash equivalents	17,434
Total available-for-sale securities	27,895		$ 49,625
Level 2 [Member] \| Government Bonds [Member]
Financial assets
Total available-for-sale securities	40,790
Level 3 [Member]
Financial liabilities
Derivative liabilities	3,150
Total financial liabilities	$ 3,150

Net Loss per Share - Additional Information (Details)	12 Months Ended
Net Loss per Share - Additional Information (Details)	Dec. 31, 2024 shares
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Common stock issuable upon exercise of pre-funded warrants	2,712,478
Pre-Funded Warrants [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Warrants Issued	0

Equity-Based Compensation - Summary of Restricted Stock Unit Activity (Detail) - 'Restricted Stock Units (RSUs) [Member]	12 Months Ended
	Dec. 31, 2024 $ / shares shares
Units
Nonvested RSUs at January 1, 2024 \| shares	877,181
Granted \| shares	1,196,954
Vested \| shares	(335,981)
Forfeitures \| shares	(257,882)
Nonvested RSUs at December 31, 2024 \| shares	1,480,272
Weighted-Average Grant Date Fair Value
Nonvested RSUs at January 1, 2024 \| $ / shares	$ 6.37
Granted \| $ / shares	7.94
Vested \| $ / shares	6.55
Forfeitures \| $ / shares	6.91
Nonvested RSUs at December 31, 2024 \| $ / shares	$ 7.5

Property and Equipment - Summary of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 17,773	$ 19,359
Less accumulated depreciation	(13,026)	(12,735)
Property and equipment, net	4,747	6,624
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	936	936
Laboratory Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	14,404	16,137
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	470	481
Computer Equipment [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	764	842
Computer Software [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	320	553
Construction in Progress [Member]
Property, Plant and Equipment [Line Items]
Property and equipment, gross	$ 879	$ 410

Equity-Based Compensation - Summary of Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Number of Options
Outstanding at January 1, 2024	2,259,672
Granted	1,219,522
Exercised	(71,562)
Expired	(44,521)
Forfeitures	(435,174)
Outstanding at December 31, 2024	2,927,937
Vested and expected to vest as of December 31, 2024	2,927,937
Exercisable at December 31, 2024	1,117,768
Weighted Average Exercise Price
Outstanding at January 1, 2024	$ 21.93
Granted	7.81
Exercised	6.39
Expired	31.11
Forfeitures	8.93
Outstanding at December 31, 2024	18.22
Vested and expected to vest as of December 31, 2024	18.22
Exercisable at December 31, 2024	$ 35.27
Remaining Contractual Life (in years)
Outstanding	8 years 3 days
Vested and expected to vest as of December 31, 2024	8 years 3 days
Exercisable at December 31, 2024	6 years 9 months 14 days
Outstanding, Aggregate Intrinsic Value	$ 193	$ 863
Vested and expected to vest, Aggregate Intrinsic Value	193
Exercisable, Aggregate Intrinsic Value	$ 541

Award Timing Disclosure	12 Months Ended
Award Timing Disclosure	Dec. 31, 2024
Award Timing Disclosures [Line Items]
Award Timing MNPI Disclosure	We grant equity awards, including stock options and/or restricted stock units, to our employees on an annual basis. We grant stock options to our directors on an annual basis. We may also grant stock options and/or restricted stock units to individuals upon hire or promotion or for retention purposes. We currently do not grant stock appreciation rights or similar option-like instruments. During the year ended December 31, 2024, neither the Board of Directors nor the compensation committee took material nonpublic information into account when determining the timing or terms of equity awards, nor did we time the disclosure of material nonpublic information for the purpose of affecting the value of executive compensation. While we do not have any policy or obligation that requires us to grant equity awards on specified dates, annual stock option and/or restricted stock unit grants to employees are typically approved in January or February of each year. During the year ended December 31, 2024, new hire equity grants were made by our Chief Executive Officer on the first business day of the month following such employee’s hire pursuant to delegated authority under our 2024 Inducement Stock Incentive Plan. Our Chief Executive Officer does not take into account material nonpublic information when determining the timing or terms of such equity grants. Under our non-employee director compensation program, our annual stock option grants to directors are granted on the date of our annual meeting of stockholders. During the year ended December 31, 2024, we did not grant stock options to any named executive officer during any period beginning four business days before and ending one business day after the filing of any Form 10-Q or Form 10-K, or the filing or furnishing of a Form 8-K that discloses material nonpublic information.
Award Timing Predetermined	false
Award Timing MNPI Considered	true
Award Timing, How MNPI Considered	During the year ended December 31, 2024, neither the Board of Directors nor the compensation committee took material nonpublic information into account when determining the timing or terms of equity awards, nor did we time the disclosure of material nonpublic information for the purpose of affecting the value of executive compensation.

Leases - Additional Information (Detail) $ in Millions	1 Months Ended	12 Months Ended
Leases - Additional Information (Detail) $ in Millions	Jun. 30, 2021 USD ($) ft²	Dec. 31, 2024 USD ($)	May 10, 2024 ft²	Dec. 22, 2022 ft²
Hood Park LLC [Member] \| Office laboratory [Member]
Commitment And Contingencies [Line Items]
Area of lease agreement \| ft²	49,869
Lease term	10 years
Lease renewal term	5 years
Lease description		The Company relocated its corporate headquarters to the Premises in June 2022. The initial term of the lease commenced in June 2022 when the construction of the lessor assets was substantially completed and continues for a ten-year period, unless earlier terminated
Operating lease, monthly payments \| $	$ 0.3
Operating lease payments annual escalation percentage	3.00%
Construction allowance \| $	$ 10.2
Letter of credit amount \| $		$ 1.8
Arkea Bio Corp [Member]
Commitment And Contingencies [Line Items]
Area of lease agreement \| ft²			13,714	12,461
Subleased description		The Sub‑Lease term originally ended on February 28, 2025. The Sub-Lease was subsequently amended by the Sub-Lease Amendment, by and between Arkea and the Company, dated May 10, 2024, to increase the subleased area to approximately 13,714 square feet and extend the term to February 29, 2028.
Arkea Bio Corp [Member] \| Building Interior [Member]
Commitment And Contingencies [Line Items]
Area of lease agreement \| ft²				49,869

Accrued Expenses and Other Current Liabilities

12 Months Ended

Dec. 31, 2024

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

8. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	December 31,
	2024		2023
Accrued research and development expense	$	7,268	$	2,614
Accrued compensation		6,221		5,948
Accrued milestone payment (Note 3)		5,000		—
Accrued other and other current liabilities		1,363		1,599
Total	$	19,852	$	10,161

Consolidated Statements of Changes In Stockholders' Equity - USD ($) $ in Thousands	Total	Private Placement [Member]	Common Stock [Member]	Common Stock [Member] Private Placement [Member]	Additional Paid in Capital [Member]	Additional Paid in Capital [Member] Private Placement [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Accumulated Deficit [Member]
Beginning balance at Dec. 31, 2022	$ 211,666		$ 20		$ 774,452		$ (68)	$ (562,738)
Beginning balance, units at Dec. 31, 2022			19,556,732
Issuance of common stock, net of issuance costs	2,974				2,974
Issuance of common stock, net of issuance costs, units			602,030
Vesting of restricted stock units, units			183,951
Issuance of common stock under employee stock purchase plan	148				148
Issuance of common stock under employee stock purchase plan, units			43,893
Unrealized gain on available-for-sale securities	83						83
Equity-based compensation	7,625				7,625
Net loss	(96,015)							(96,015)
Ending balance at Dec. 31, 2023	126,481		$ 20		785,199		15	(658,753)
Ending balance, units at Dec. 31, 2023			20,386,606
Issuance of common stock, net of issuance costs	18,369	$ 89,454	$ 2	$ 17	18,367	$ 89,437
Issuance of common stock, net of issuance costs, units			2,212,937	16,973,103
Issuance of pre-funded warrants in private placement	14,293				14,293
Issuance of common stock in private placement for upfront consideration, units			364,990
Issuance of common stock value in private placement for upfront consideration	2,000				2,000
Vesting of restricted stock units	1		$ 1
Vesting of restricted stock units, units			335,981
Issuance of common stock under employee stock purchase plan	337				337
Issuance of common stock under employee stock purchase plan, units			122,962
Exercise of common stock options	$ 457				457
Exercise of common stock options, shares	71,562		71,562
Unrealized gain on available-for-sale securities	$ 32						32
Equity-based compensation	10,519				10,519
Net loss	(124,697)							(124,697)
Ending balance at Dec. 31, 2024	$ 137,246		$ 40		$ 920,609		$ 47	$ (783,450)
Ending balance, units at Dec. 31, 2024			40,468,141

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions				12 Months Ended
	Feb. 28, 2025	Feb. 19, 2025	Jan. 11, 2024	Dec. 31, 2024	Dec. 31, 2023
FA212 LLC [Member]
Subsequent Event [Line Items]
Development milestone payable				$ 5.0
January 2024 Private Placement [Member]
Subsequent Event [Line Items]
Net proceeds from private placement			$ 103.7
Common Stock [Member]
Subsequent Event [Line Items]
Common stock shares issued				2,212,937	602,030
Common Stock [Member] \| January 2024 Private Placement [Member]
Subsequent Event [Line Items]
Common stock shares issued			16,973,103	16,973,103
Common stock issued price per share			$ 5.53
Subsequent Event [Member] \| FA212 LLC [Member]
Subsequent Event [Line Items]
Shares issued for first milestone payment	975,496
Subsequent Event [Member] \| February 2025 Offering [Member]
Subsequent Event [Line Items]
Proceeds from issuance of common stock		$ 187.5
Subsequent Event [Member] \| Common Stock [Member] \| February 2025 Offering [Member]
Subsequent Event [Line Items]
Common stock shares issued		35,739,810
Common stock issued price per share		$ 4.03
Subsequent Event [Member] \| Pre-Funded Warrants [Member] \| February 2025 Offering [Member]
Subsequent Event [Line Items]
Pre-funded warrants to purchase shares of common stock		13,888,340
Common stock warrants price per share		$ 4.029

License Agreements

12 Months Ended

Dec. 31, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

License Agreements

12. License Agreements

University of Washington License Agreement

In 2015, the Company entered into a license agreement with the University of Washington, acting through UW CoMotion, under which the Company obtained an exclusive, royalty-bearing, sublicensable, worldwide license under a patent application owned by the University of Washington relating to novel micro-dystrophins and all patents claiming priority to such patent to develop, manufacture, and commercialize products for use in the treatment of Duchenne and related disease indications caused by a lack of functional dystrophin. The Company has the right to grant sublicenses to third parties contingent upon written approval by the University of Washington prior to executing such sublicense, which approval may not be unreasonably withheld.

In consideration for the rights granted by the agreement, the Company paid a one-time, non-refundable license fee, which was recorded as a research and development expense in 2015. The Company is required to reimburse the University of Washington for costs incurred in applying for, prosecuting and maintaining patents and pay up to an aggregate of approximately $1.0 million upon the achievement of certain milestones. In October 2017, the first milestone was achieved under this agreement. The milestone payment was recorded as a research and development expense in the fourth quarter of 2017. In October 2020, the license agreement was amended such that the Company was required to pay the University of Washington $0.4 million in connection with the execution of the Collaboration Agreement. This payment was recorded as a research and development expense in the fourth quarter of 2020. The license agreement was also amended such that the Company is required to pay an aggregate of approximately $3.4 million upon the achievement of certain milestones. There were no milestones achieved during the years ended December 31, 2024 and 2023. The Company must also pay royalties of a low single digit percentage of future sales by the Company and its sublicensees of products developed under the licensed patent rights. In addition, the Company must pay an annual maintenance fee until certain milestones are achieved, at which time a minimum annual royalty requirement will replace such maintenance fee and will apply to the Company and its sublicensees.

The license agreement remains in effect until the expiration of the last-to-expire patent licensed under the agreement. The Company may terminate the agreement at any time upon providing sixty days’ written notice to the University of Washington. The University of Washington may terminate the agreement upon the Company’s uncured, material breach of the agreement or if the Company enters into an insolvency-related event.

The Company recorded research and development expense in the amount of $0.1 million and $0 for the years ended December 31, 2024 and 2023, respectively, under the agreement.

The University of Missouri License Agreement

In 2015, the Company entered into a license agreement with the Curators of the University of Missouri (the “University of Missouri”), a public corporation of Missouri, under which the Company obtained an exclusive, royalty-bearing, sublicensable, worldwide license under certain patent and patent applications owned by the University of Missouri relating to a novel synthetic microdystrophin gene to make, sell and distribute products for use in the treatment of Duchenne and related disease indications resulting from a lack of functional dystrophin.

Under the agreement, in the event the Company grants a sublicenses to another party, the Company is required to pay the University of Missouri a percentage of the consideration received. The license agreement was amended such that the Company was required to pay the University of Missouri $0.8 million in 2021 and $1.3 million in 2022. These amounts were recorded as a research and development expense in the fourth quarter of 2020. The Company paid $0.8 million in February 2021 and $1.3 million in February 2022. The license agreement was also amended such that the Company is required to pay an aggregate of approximately $1.9 million upon the achievement of certain milestones.

There were no milestones achieved during the years ended December 31, 2024 and 2023. The Company must pay a royalty of a low single digit percentage of future sales or by its sublicensees of products developed using the licensed patents. In addition, the Company must pay an annual maintenance fee until certain milestones are achieved, after which time a minimum annual royalty will replace such maintenance fee.

Under the agreement, the Company granted the University of Missouri a non-exclusive, royalty-free, irrevocable, paid-up license, with the right to grant sublicenses to non-profit, academic, educational or governmental institutions, to practice and use improvements made by the Company using the licensed patent rights, solely for non-commercial research purposes.

The license agreement remains in effect until the expiration of the last-to-expire patent or the abandonment of the last to be abandoned patent application licensed under the agreement. The University of Missouri may terminate the agreement, or render the license granted thereunder non-exclusive, in individual countries if the Company’s sublicensees fail to achieve

certain milestones. The Company may terminate the license agreement at any time upon providing six months’ written notice to the University of Missouri and paying a termination fee. Each of the University of Missouri and the Company may also terminate the agreement for an uncured default or breach of the agreement by the other party. The Company’s ability to cure such breach only applies to the first two notices of such breach provided by the University of Missouri, and thereafter, the University of Missouri may terminate the agreement for the Company’s default or breach of the agreement upon thirty days’ written notice without an opportunity to cure such default or breach.

The Company recorded research and development expense in the amount of $0.1 million and $0.1 million for the years ended December 31, 2024 and 2023, respectively, under the agreement.

University of Florida License Agreements

In 2020, AavantiBio entered into license agreements with the University of Florida Research Foundation, Inc. (“UFRF”). Broadly, the agreements relate to FA. The Company acquired the agreements in connection with the Acquisition. In 2023, the Company entered into an additional license agreement with UFRF. Under each agreement the Company obtained an exclusive, royalty-bearing, sublicensable, world-wide license to certain patents and patent applications and a royalty-bearing non-exclusive license under the know-how, to make, have made, use, see, have sold, import and export licensed products. UFRF retains the right to practice the patent rights and know-how for internal non-commercial research, including research sponsored by commercial entities, and educational purposes.

In consideration for the rights granted under each agreement, AavantiBio paid a one-time non-refundable license fee. In connection with each agreement, the Company is required to pay an annual license maintenance fee until the first commercial sale of a licensed product after which time a minimum annual royalty will replace such maintenance fees. Under each agreement, the Company is required to reimburse UFRF for costs incurred in applying for, prosecuting and maintaining patents, pay up to an aggregate of approximately $2.9 million upon the achievement of certain intellectual property, clinical and regulatory milestones for each licensed product under the agreement, and pay a low, single digit royalty on annual net sales by us and our sublicensees of licensed products on a licensed-product-by-licensed product basis. For any licensed product covered by both of these agreements, the Company is only obligated to make one payment for each milestone achieved and royalty payment due. Prior to the Acquisition, AavantiBio paid a single milestone fee related to the agreements of $0.1 million. Under each agreement, in the event the Company grants a sublicense to another party, the Company is required to pay UFRF a percentage of the consideration received.

Under each agreement, the Company has the right to grant sublicenses to third parties through multiple tiers, to the extent we are in compliance with our diligence obligations under the agreement and that sublicensee is subject to the terms of such agreement.

Under each agreement, the Company is obligated to use commercially reasonable efforts to develop and commercialize products covered by the licensed patent rights or know-how and to achieve certain regulatory and commercialization milestones within estimated time periods. Under the agreements entered in 2023 and 2024, the Company agreed to pay to UFRF cumulative sales milestones of up to $8.5 million and $27.0 million, respectively, upon achievement of specified commercial milestone events and tiered royalties on worldwide net sales in the low-to-mid-single digits.

Under each agreement, UFRF controls the prosecution and maintenance of the licensed patents in consultation with the Company and at the Company's expense. In countries in which the Company has not requested prosecution or maintenance of licensed patents in a particular country or jurisdiction, the license granted to such patent rights will terminate in such country or jurisdiction. The Company has the first right to enforce such licensed patents at our expense.

Each of the agreements terminates on a licensed product-by-licensed product basis on the later of: (i) expiration of the patent rights covering such licensed product or (ii) ten years from the first commercial sale of such licensed product. After five years, the Company may terminate an agreement for any reason giving advance written notice and reason for termination. UFRF may terminate an agreement for our uncured default or breach of the agreement. UFRF may immediately terminate an agreement if we bring or assist others in bringing a patent challenge against of the licensed patent rights. If UFRF sends the Company a written demand to terminate a sublicense agreement due to such sublicensee bringing or assisting a patent challenge, UFRF may terminate such agreement if we do not terminate the license with such sublicensee.

Maugeri License Agreement

On June 29, 2023, the Company entered into a license agreement (the "Maugeri License Agreement"), with ICS Maugeri S.p.A. SB ("Maugeri"), to focus on the development and commercialization of cardiac-related products by the Company based on Maugeri’s inventions. Pursuant to the Maugeri License Agreement, Maugeri granted us an exclusive worldwide sublicensable license in certain Maugeri patent rights, including existing patent rights, and those in any improvements or know-how made in performance of the Maugeri License Agreement, and a non-exclusive worldwide sublicensable license in

certain Maugeri know-how, including existing know-how, and on any improvement thereto, in each case, subject to certain conditions, that is necessary or reasonably useful to develop the licensed products under the terms of the Maugeri License Agreement. The Company will conduct certain activities agreed to by the parties with respect to the research and development of licensed products. A condition precedent to the effectiveness of the Maugeri License Agreement was regulatory review in Italy, which was completed in the third quarter of 2023 and, upon the completion of the condition precedent, the Maugeri License Agreement became effective.

The Company paid Maugeri an upfront license fee of €1.5 million, which was recorded as research and development expense during the second quarter of 2023. Additionally, the Company agreed to cumulative developmental, regulatory, and commercial milestone payments of up to €15.0 million, cumulative sales milestone payments of up to €15.0 million, upon achievement of specified milestone events, and tiered royalties on worldwide net sales in the low-to-mid-single-digits. There were no milestones achieved during the years ended December 31, 2024 and December 31, 2023.

The Maugeri License Agreement continues until the latest expiry of (i) the last valid claim (as defined in the Maugeri License Agreement), (ii) regulatory exclusivity, and (iii) all payment obligations. Either party may terminate the Maugeri License Agreement for the other party’s uncured material breach. The Company may also terminate the Maugeri License Agreement in its sole discretion upon 60 days’ prior written notice to Maugeri and payment of a fee.

Mayo Clinic Collaboration and License Agreement

In December 2024, the Company entered into a collaboration, patent and know-how license agreement with the Mayo Foundation for Medical Education and Research (the “Mayo”) to further advance the Company's research and development efforts in the field of genetic therapies, particularly for rare and debilitating cardiac diseases.

As part of the collaboration, the Company will be providing manufactured viral materials and CMC know-how while the Mayo will be responsible for supporting all preclinical research through IND-enabling studies for six programs. The Company will then be responsible for the clinical development of programs chosen by it to develop. Under the terms of the collaboration, the Company and Mayo agreed to share intellectual property rights arising from the collaboration, with the Company retaining exclusive rights to commercialize any resulting therapies.

In connection with the agreement, the Company paid a one-time upfront payment of $0.6 million in cash and $2.0 million of shares of its common stock to Mayo, which were recorded to research and development expense in the fourth quarter of 2024 having no alternative future use. Additionally, Mayo is eligible for cumulative developmental milestones of $5.0 million, cumulative regulatory milestones of $2.0 million, and cumulative sales milestone payments of up to $18.0 million, upon achievement of specified milestone events, and tiered royalties on worldwide net sales in the low-to-high-single-digits for certain licensed products developed by the Company. The Company also agreed to pay an annual $0.6 million know-how access fee to Mayo. There were no milestones achieved during the year ended December 31, 2024.

The agreement also includes provisions for the potential sublicensing of certain intellectual property rights. The Company will also be responsible for reimbursing Mayo for costs incurred in the prosecution and maintenance of any patents resulting from the collaboration.

The collaboration remains in effect for the duration of the intellectual property rights associated with any therapies developed under the agreement. Either party may terminate the agreement with proper notice should specific terms be breached or should an insolvency-related event occur.

Other Agreements

The Company has committed to make potential future milestone payments and pay legal fees to third parties as part of licensing and development programs. The agreements generally required an upfront license fee and, under each agreement, the Company may be required to pay annual maintenance fees, royalties, milestone payments and sublicensing fees. Each license agreement is generally cancelable by the Company, given appropriate prior written notice. At December 31, 2024, potential future milestone payments under these agreements totaled an aggregate of $18.1 million. None of these milestones were assessed to be probable as of December 31, 2024.

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Statement of Comprehensive Income [Abstract]
Net loss	$ (124,697)	$ (96,015)
Other comprehensive income:
Unrealized gain on available-for-sale securities	32	83
Comprehensive loss	$ (124,665)	$ (95,932)

- Definition

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

+ References + Details

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

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+ Details

Fair Value of Financial Assets and Liabilities

12 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

Fair Value of Financial Assets and Liabilities

4. Fair Value of Financial Assets and Liabilities

The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis:


	December 31, 2024
	Level 1		Level 2		Level 3		Total
Financial assets
Cash equivalents:
Money market funds	$	—	$	18,088	$	—	$	18,088
Treasury bills		—		17,434		—		17,434
Total cash equivalents		—		35,522		—		35,522
Available-for-sale securities (Note 5):
Treasury bills		—		27,895		—		27,895
Government bonds		—		40,790		—		40,790
Total available-for-sale securities		—		68,685		—		68,685
Total financial assets	$	—	$	104,207	$	—	$	104,207

Financial liabilities
Derivative liabilities	$	—	$	—	$	3,150	$	3,150
Total financial liabilities	$	—	$	—	$	3,150	$	3,150


	December 31, 2023
	Level 1		Level 2		Level 3		Total
Financial assets
Cash equivalents:
Money market funds	$	—	$	62,141	$	—	$	62,141
Certificates of deposit		—		257		—		257
Total cash equivalents		—		62,398		—		62,398
Available-for-sale securities (Note 5):
Treasury bills		—		49,625		—		49,625
Total available-for-sale securities		—		49,625		—		49,625
Total financial assets	$	—	$	112,023	$	—	$	112,023

As of December 31, 2024 and 2023, the fair values of the Company’s cash equivalents and available-for-sale securities were determined using Level 2 inputs.

The Company’s accounts payable, accrued expenses, and other current liabilities approximated their estimated fair values due to the short-term nature of these financial instruments.

The Company estimated the fair value of the derivative liabilities by using a Monte Carlo simulation forecasting the timing and likelihood of certain development milestone events being achieved and discounting the probability adjusted payments using an appropriate discount rate based on market interest rates. The main assumptions when determining the fair value of the derivative liabilities are the timing of and probability of achieving certain milestones, the estimated volatility of the Company’s common stock, and the discount rate. The estimated fair value presented is not necessarily indicative of an amount that could be realized in a current market exchange. The use of alternative inputs and estimation methodologies could have a material effect on these estimates of fair value.

Significant unobservable inputs for the derivative liabilities as of December 31, 2024 are as follows:


Derivative Liabilities	Valuation Technique	Unobservable Input	Range	Average
Development Milestones	Monte Carlo Simulation	Probability of achieving certain development milestones	28.0% - 70.0%	49.0%
		Volatility	85.0%	85.0%
		Discount Rate	4.2% - 4.3%	4.3%
		Timing of achieving certain development milestones	1.0 - 3.7 years	2.3 years

Significant unobservable inputs for the derivative liabilities as of September 19, 2024 (the date of entry into the agreement with FA212) are as follows:


Derivative Liabilities	Valuation Technique	Unobservable Input	Range	Average
Development Milestones	Monte Carlo Simulation	Probability of achieving certain development milestones	2.0% - 80.0%	28.6%
		Volatility	114.0%	114.0%
		Discount Rate	3.5% - 4.8%	3.8%
		Timing of achieving certain development milestones	0.3 to 5.5 years	2.4 years

The following table reflects the fair value of the Company's Level 3 derivative liabilities for the year ended December 31, 2024:


Fair value of derivative liabilities as of December 31, 2023	$	—
Fair value of derivative liabilities as of September 19, 2024		3,400
Change in fair value of derivative liabilities		4,750
Reclassification of accrued milestone payment to accrued expenses and other current liabilities		(5,000	)
Fair value of derivative liabilities as of December 31, 2024	$	3,150

During the years ended December 31, 2024 and 2023, there were no transfers between Level 1, Level 2 and Level 3.

Equity-Based Compensation - Schedule of Equity-based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 10,519	$ 7,625
Research and Development Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	3,537	3,094
General and Administrative Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 6,982	$ 4,531

Leases - Future Minimum Payments for Operating and Finance Leases (Detail) $ in Thousands	Dec. 31, 2024 USD ($)
Finance Leases
2025	$ 651
2026	0
Total future minimum lease payments	651
Less: Imputed Interest	(580)
Total Lease Liabilities	1,231
Operating Leases
2025	4,176
2026	4,284
2027	4,280
2028	4,364
Thereafter	17,118
Total future minimum lease payments	34,222
Less: Imputed Interest	11,276
Lease liability	$ 22,946

Segment Reporting (Tables)

12 Months Ended

Dec. 31, 2024

Segment Reporting [Abstract]

Schedule of Segment Expenses, Other Segment Items, and Segment Net Loss

The following table presents segment expenses, other segment items, and segment net loss for the periods presented:


	Year Ended December 31,
	2024			2023
Segment Expenses:
SGT-003		15,197			20,856
SGT-501		17,223			3,200
External R&D other		10,580			7,907
Internal R&D expense(1)		21,705			21,798
External G&A expense		20,122			19,635
Internal G&A expense(1)		12,223			10,911
Other segment items(2)		32,678			19,945
Other income, net		(5,031	)		(8,237	)
Consolidated net loss		(124,697	)		(96,015	)


(1)	Internal expenses consisted primarily of payroll and related costs, temporary services, and travel and entertainment.
(2)	Other segment items primarily included equity-based compensation expense, other program costs, and depreciation and amortization expense

Leases - Summary of Weighted Average Remaining Lease Term and Discount Rate (Detail)	Dec. 31, 2024	Dec. 31, 2023
Weighted-average remaining lease term (in years)
Operating lease	7 years 7 months 6 days	8 years 6 months
Finance lease	9 months 18 days	1 year 9 months 18 days
Weighted-average discount rate
Operating lease	10.80%	10.70%
Finance lease	22.80%	22.80%

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Feb. 19, 2025	Jan. 11, 2024	Dec. 31, 2024	Dec. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants exercised			0
Net losses			$ 124,697	$ 96,015
Accumulated deficit			783,450	658,753
Net cash used in operating activities			100,012	$ 94,180
Cash, cash equivalents and available-for-sale securities			148,900
Restricted cash			$ 2,000
Private Placement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net proceeds from private placement		$ 103,700
At-the-Market Offering Sales Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock shares issued			2,212,937
Proceeds from issuance of common stock			$ 18,400
February 2025 Offering [Member] \| Subsequent Event [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net proceeds from offering	$ 187,500
Proceeds from issuance of common stock	$ 187,500
Common Stock [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock shares issued			2,212,937	602,030
Common Stock [Member] \| Private Placement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock shares issued		16,973,103	16,973,103
Common stock issued price per share		$ 5.53
Common Stock [Member] \| February 2025 Offering [Member] \| Subsequent Event [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock shares issued	35,739,810
Common stock issued price per share	$ 4.03
Pre-Funded Warrants [Member] \| Private Placement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Pre-funded warrants to purchase shares of common stock		2,712,478
Common stock warrants price per share		$ 5.529
Pre-Funded Warrants [Member] \| February 2025 Offering [Member] \| Subsequent Event [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Pre-funded warrants to purchase shares of common stock	13,888,340
Common stock warrants price per share	$ 4.029

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2024	Mar. 03, 2025	Jun. 28, 2024
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	FY
Trading Symbol	SLDB
Title of 12(b) Security	Common Stock $0.001 par value per share
Security Exchange Name	NASDAQ
Entity Registrant Name	Solid Biosciences Inc.
Entity Central Index Key	0001707502
Current Fiscal Year End Date	--12-31
Entity File Number	001-38360
Entity Tax Identification Number	90-0943402
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	500 Rutherford Avenue, Third Floor
Entity Address, City or Town	Charlestown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02129
City Area Code	617
Local Phone Number	337-4680
Document Annual Report	true
Document Transition Report	false
Entity Filer Category	Non-accelerated Filer
Entity Small Business	true
Document Financial Statement Error Correction [Flag]	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		77,492,959
Entity Public Float			$ 130.3
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
ICFR Auditor Attestation Flag	false
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Boston, Massachusetts
Auditor Opinion [Text Block]	Opinion on the Financial Statements We have audited the accompanying consolidated balance sheets of Solid Biosciences, Inc. and its subsidiaries (the “Company”) as of December 31, 2024 and 2023, and the related consolidated statements of operations, of comprehensive loss, of changes in stockholders’ equity and of cash flows for the years then ended, including the related notes (collectively referred to as the “consolidated financial statements”). In our opinion, the consolidated financial statements present fairly, in all material respects, the financial position of the Company as of December 31, 2024 and 2023, and the results of its operations and its cash flows for the years then ended in conformity with accounting principles generally accepted in the United States of America.

Commitments and Contingencies

12 Months Ended

Dec. 31, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

11. Commitments and Contingencies

Letter of Credit

The Company had an outstanding letter of credit in the amount of $2.0 million and $1.8 million at December 31, 2024 and 2023, respectively, which was required as a condition of the Company’s office and laboratory leases.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters, including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with its executive officers and members of its Board of Directors that require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as executive officers or directors. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnification arrangements.

The Company does not believe that the outcome of any claims under indemnification arrangements will have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of December 31, 2024 and 2023.

Legal Proceedings

The Company may periodically become subject to legal proceedings and claims arising in connection with ongoing business activities, including claims or disputes related to patents that have been issued or that are pending in the field of research on which the Company is focused. The Company is not aware of any material legal proceedings or claims as of December 31, 2024.

Leases (Tables)

12 Months Ended

Dec. 31, 2024

Leases [Abstract]

Future Minimum Payments for Operating and Finance Leases

As of December 31, 2024, minimum future lease payments for these operating and finance leases were as follows:


	Finance Leases			Operating Leases
2025	$	651		$	4,176
2026		—			4,284
2027		—			4,280
2028		—			4,364
Thereafter		—			17,118
Total		651			34,222
Less: Imputed Interest		(580	)		11,276
Total Lease Liabilities	$	1,231		$	22,946

Summary of Components of Lease Costs

The following table shows the components of lease costs:


	Year Ended December 31,
Lease cost	2024			2023
Operating lease cost	$	4,961		$	5,250
Finance lease cost:
Amortization of right-of-use assets		441			476
Interest on lease liabilities		340			440
Sub-lease income		(963	)		(1,094	)
Total lease cost	$	4,779		$	5,072

Summary of Weighted Average Remaining Lease Term and Discount Rate

The following table shows the weighted average remaining lease term and weighted average discount rate of the Company’s leases are as follows:


	Year Ended December 31,
	2024			2023
Weighted-average remaining lease term (in years)
Operating lease		7.6			8.5
Finance lease		0.8			1.8
Weighted-average discount rate
Operating lease		10.8	%		10.7	%
Finance lease		22.8	%		22.8	%

Equity-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands				1 Months Ended	12 Months Ended
	Jun. 11, 2024	Nov. 12, 2023	Jun. 05, 2023	Jun. 30, 2024	Dec. 31, 2024	Dec. 31, 2023	Mar. 31, 2024	Jun. 06, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding					2,927,937	2,259,672
Weighted average grant date fair value of stock options granted					$ 6.96	$ 4.76
Equity-based compensation expense					$ 10,519	$ 7,625
Intrinsic value of stock options exercised					457
Stock-based compensation expense					10,519	7,625
'Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense					3,000	2,200
Unrecognized equity-based compensation					$ 9,000
Unrecognized equity-based compensation cost, weighted average period					2 years 10 months 24 days
Aggregate grant date fair value of RSUs vested					$ 2,200	1,400
Granted					1,196,954
Weighted average grant date fair value					$ 7.94
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized equity-based compensation					$ 5,900
Unrecognized equity-based compensation cost, weighted average period					1 year 10 months 24 days
Description of vesting rights					Each PSU represents the contingent right to receive one share of the Company’s common stock.
Percentage of vesting				25.00%
Granted					2,165,325
Weighted average grant date fair value					$ 7.51
Stock-based compensation expense					$ 2,200
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense					5,100	5,300
Unvested Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized equity-based compensation					$ 9,000
Unrecognized equity-based compensation cost, weighted average period					2 years 3 months 18 days
Intrinsic value of stock options exercised					$ 300	$ 0
Amended and Restated 2020 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized for common stock for equity awards	2,000,000
2020 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding					2,000,796
Number of shares available for future issuance					185,519
2020 Equity Incentive Plan [Member] \| 'Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units outstanding					981,849
2020 Equity Incentive Plan [Member] \| Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units outstanding					2,165,325
Amendment and Restatement of ESPP [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized for common stock for equity awards			73,525
Number of share reserved for future issuance								473,525
Percentage of number of shares outstanding					1.00%
Offering period		24 months
Amendment and Restatement of ESPP [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized for common stock for equity awards					293,597
Amended and Restated 2021 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for future issuance					478,450
Number of shares authorized for common stock for equity awards								677,391
2024 Inducement Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding					100,000
Stock units outstanding					300,067
Number of shares available for future issuance					599,933
Number of shares authorized for common stock for equity awards							1,000,000

Fair Value of Financial Assets and Liabilities - Summary of Significant Unobservable Inputs for Derivative Liabilities (Detail) - Level 3 [Member]	Dec. 31, 2024 yr	Sep. 19, 2024 yr
Probability of Achieving Certain Development Milestones [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.28	0.02
Probability of Achieving Certain Development Milestones [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.70	0.80
Probability of Achieving Certain Development Milestones [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.49	0.286
Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.85	1.14
Volatility [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.85	1.14
Discount Rate [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.042	0.035
Discount Rate [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.043	0.048
Discount Rate [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.043	0.038
Timing of Achieving Certain Development Milestones [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	1	0.3
Timing of Achieving Certain Development Milestones [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	3.7	5.5
Timing of Achieving Certain Development Milestones [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	2.3	2.4

Restructuring

12 Months Ended

Dec. 31, 2024

Restructuring and Related Activities [Abstract]

Restructuring

16. Restructuring

In November 2022, the Company’s Board of Directors approved a plan to reduce the Company’s workforce by approximately 18 percent. These reductions were completed by December 5, 2022. This plan was designed to streamline the Company’s operating structure following the Acquisition. The Company recorded a restructuring charge in the fourth quarter of 2022 of $5.7 million related to the reduction in force, consisting of severance and other employee termination benefits. The Company paid the remaining $0.3 million of this amount during the year ended December 31, 2024.

The following table shows the balance of accrued restructuring charges and the changes in the accrued amounts in connection with the associated restructuring plans for the years ended December 31, 2024 and 2023:


One-Time Employee Termination Benefits	November 2022
Accrued restructuring charges as of December 31, 2022	$	3,921
Accrual recorded as a result of restructuring charges		—
Amounts paid during the period		(3,669	)
Accrued restructuring charges as of December 31, 2023	$	252
Accrual recorded as a result of restructuring charges		—
Amounts paid during the period		(252	)
Accrued restructuring charges as of December 31, 2024	$	—

Prepaid Expenses and Other Current Assets (Tables)

12 Months Ended

Dec. 31, 2024

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following:


	December 31,
	2024		2023
Prepaid research and development expenses	$	6,731	$	3,980
Prepaid other and other current assets		1,651		2,114
Total	$	8,382	$	6,094

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Operating activities:
Net loss	$ (124,697)	$ (96,015)
Adjustments to reconcile net loss to net cash used in operating activities:
Net amortization of (discount)/premium on available-for-sale securities	(3,592)	(2,408)
Equity-based compensation expense	10,519	7,625
Depreciation and amortization expense	2,455	2,581
Non-cash lease expense	2,391	2,531
Non-cash acquired in-process research and development	3,400	0
Common stock issued as up-front payment for collaboration and license agreement	2,000	0
Change in fair value of derivative liabilities	4,750	0
Other	(88)	374
Changes in operating assets and liabilities:
Prepaid expenses and other current and non-current assets	(2,445)	598
Accounts payable	2,205	(764)
Change in operating lease liability	(1,676)	(1,735)
Accrued expenses and other current and non-current liabilities	4,766	(6,967)
Net cash used in operating activities	(100,012)	(94,180)
Investing activities:
Purchases of property and equipment	(654)	(1,515)
Proceeds from sale of property and equipment	5	0
Proceeds from sales and maturities of available-for-sale securities	188,900	128,632
Purchases of available-for-sale securities	(204,337)	(117,428)
Net cash (used in) provided by investing activities	(16,086)	9,689
Financing activities:
Proceeds from issuance of common stock and pre-funded warrants in private placement	108,858	0
Payments of common stock and pre-funded warrants issuance costs in private placement	(5,111)	0
Proceeds from issuance of common stock in public offering, net of sales commissions	18,369	2,974
Proceeds from exercise of stock options	457	0
Employee stock purchase plan purchases	337	148
Payments of principal portion of finance lease obligations	(473)
Net cash provided by financing activities	122,437	3,122
Net increase (decrease) in cash, cash equivalents and restricted cash	6,339	(81,369)
Cash, cash equivalents, and restricted cash at beginning of period	75,848	157,217
Cash, cash equivalents, and restricted cash at end of period	82,187	75,848
Supplemental disclosure of cash flow information:
Operating cash flows for operating leases	4,264	4,501
Operating cash flows for finance leases	469	375
Financing cash flows for finance leases, cash paid for interest	340	435
Supplemental disclosure of non-cash investing and financing activities:
Right-of-use assets obtained in exchange for operating lease liabilities	407	121
Decrease in right-of-use asset and lease liability due to lease termination	(261)	(252)
Decrease in property, plant and equipment due to asset exchange	0	(950)
Property and equipment purchases included in accounts payable and accruals	$ 0	$ 76

Fair Value of Financial Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2024

Fair Value Disclosures [Abstract]

Summary of Assets and Liabilities Measured at Fair Value on Recurring Basis

The following tables present information about the Company’s assets and liabilities that are measured at fair value on a recurring basis:


	December 31, 2024
	Level 1		Level 2		Level 3		Total
Financial assets
Cash equivalents:
Money market funds	$	—	$	18,088	$	—	$	18,088
Treasury bills		—		17,434		—		17,434
Total cash equivalents		—		35,522		—		35,522
Available-for-sale securities (Note 5):
Treasury bills		—		27,895		—		27,895
Government bonds		—		40,790		—		40,790
Total available-for-sale securities		—		68,685		—		68,685
Total financial assets	$	—	$	104,207	$	—	$	104,207

Financial liabilities
Derivative liabilities	$	—	$	—	$	3,150	$	3,150
Total financial liabilities	$	—	$	—	$	3,150	$	3,150


	December 31, 2023
	Level 1		Level 2		Level 3		Total
Financial assets
Cash equivalents:
Money market funds	$	—	$	62,141	$	—	$	62,141
Certificates of deposit		—		257		—		257
Total cash equivalents		—		62,398		—		62,398
Available-for-sale securities (Note 5):
Treasury bills		—		49,625		—		49,625
Total available-for-sale securities		—		49,625		—		49,625
Total financial assets	$	—	$	112,023	$	—	$	112,023

Summary of Significant Unobservable Inputs for Derivative Liabilities

Significant unobservable inputs for the derivative liabilities as of December 31, 2024 are as follows:


Derivative Liabilities	Valuation Technique	Unobservable Input	Range	Average
Development Milestones	Monte Carlo Simulation	Probability of achieving certain development milestones	28.0% - 70.0%	49.0%
		Volatility	85.0%	85.0%
		Discount Rate	4.2% - 4.3%	4.3%
		Timing of achieving certain development milestones	1.0 - 3.7 years	2.3 years

Significant unobservable inputs for the derivative liabilities as of September 19, 2024 (the date of entry into the agreement with FA212) are as follows:


Derivative Liabilities	Valuation Technique	Unobservable Input	Range	Average
Development Milestones	Monte Carlo Simulation	Probability of achieving certain development milestones	2.0% - 80.0%	28.6%
		Volatility	114.0%	114.0%
		Discount Rate	3.5% - 4.8%	3.8%
		Timing of achieving certain development milestones	0.3 to 5.5 years	2.4 years

Summary of Fair Value of Derivative Liabilities

The following table reflects the fair value of the Company's Level 3 derivative liabilities for the year ended December 31, 2024:


Fair value of derivative liabilities as of December 31, 2023	$	—
Fair value of derivative liabilities as of September 19, 2024		3,400
Change in fair value of derivative liabilities		4,750
Reclassification of accrued milestone payment to accrued expenses and other current liabilities		(5,000	)
Fair value of derivative liabilities as of December 31, 2024	$	3,150

During the years ended December 31, 2024 and 2023, there were no transfers between Level 1, Level 2 and Level 3.

Available-for-Sale Securities

12 Months Ended

Dec. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Available-for-Sale Securities

5. Available-for-Sale Securities

A summary of the Company’s available-for-sale securities is presented below:


	December 31, 2024
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Treasury bills maturing in one year or less	$	27,879	$	16	$	—	$	27,895
Government bonds maturing in one year or less		40,759		31		—	$	40,790
Total available-for-sale securities	$	68,638	$	47	$	—	$	68,685


	December 31, 2023
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Treasury bills maturing in one year or less	$	49,610	$	15	$	—	$	49,625
Total available-for-sale securities	$	49,610	$	15	$	—	$	49,625

The weighted average contractual maturity of the Company’s available-for-sale securities was approximately 0.5 years and 0.4 years as of December 31, 2024 and 2023, respectively.

Prepaid Expenses and Other Current Assets

12 Months Ended

Dec. 31, 2024

Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]

Prepaid Expenses and Other Current Assets

6. Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following:


	December 31,
	2024		2023
Prepaid research and development expenses	$	6,731	$	3,980
Prepaid other and other current assets		1,651		2,114
Total	$	8,382	$	6,094

Income Taxes - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Income Taxes [Line Items]
Income tax expense (benefit)	$ 0	$ 0
Unrecognized tax benefits	0	0
Tax interest and penalties	0	$ 0
Domestic Tax Authority [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	133,300,000
Tax credits carryforwards	$ 13,100,000
Tax credit carryforwards, expiration period	2037
Percentage of annual deduction equal to annual taxable income	80.00%
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Net operating loss carryforwards	$ 146,500,000
Operating loss carryforwards, expiration	$ 143,300,000
Operating loss carryforwards, expiration period	2032
Unlimited carryforward amount	$ 3,200,000
Tax credits carryforwards	$ 2,800,000
Tax credit carryforwards, expiration period	2037

Net Loss per Share - Schedule Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Earnings Per Share Basic [Line Items]
Net loss	$ (124,697)	$ (96,015)
Weighted average shares of common stock outstanding, basic	40,816,694	19,884,007
Weighted average shares of common stock outstanding, diluted	40,816,694	19,884,007
Net loss per share, basic	$ (3.06)	$ (4.83)
Net loss per share, diluted	$ (3.06)	$ (4.83)
Common Stock [Member]
Earnings Per Share Basic [Line Items]
Weighted average shares of common stock outstanding, basic	38,178,327	19,884,007
Weighted average shares of common stock outstanding, diluted	38,178,327	19,884,007
Pre-Funded Warrants [Member]
Earnings Per Share Basic [Line Items]
Weighted average shares of common stock outstanding, basic	2,638,367
Weighted average shares of common stock outstanding, diluted	2,638,367

- Definition

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

+ References

+ 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

+ Details

- Definition

The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest.

+ References

+ Details

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Calculation of Net Loss per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share	6,864,404	3,136,853
Options to Purchase Common Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share	2,927,937	2,259,672
Nonvested Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share	1,480,272	877,181
Nonvested Performance Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share	2,165,325
Shares Subject to Employee Stock Purchase Plan [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share	281,640
Warrants [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share	9,230

Equity-Based Compensation

12 Months Ended

Dec. 31, 2024

Share-Based Payment Arrangement [Abstract]

Equity-Based Compensation

9. Equity-Based Compensation

Equity-Based Compensation Expense

The Company has classified equity-based compensation in its consolidated statements of operations as follows:


	Year Ended December 31,
	2024		2023
Research and development expenses	$	3,537	$	3,094
General and administrative expenses		6,982		4,531
Total	$	10,519	$	7,625

Equity Incentive Plans

As of December 31, 2024, the Company’s approved equity incentive plans include: the 2018 Omnibus Incentive Plan (the “2018 Plan”); Amended and Restated 2020 Equity Incentive Plan (the “2020 Plan”); the Amended and Restated 2021 Employee Stock Purchase Plan (the "ESPP"); and the 2024 Inducement Stock Incentive Plan (the "2024 Inducement Plan"). These plans are administered by the Board of Directors (the "Board") and permit the granting of stock options, stock appreciation rights, restricted stock, restricted stock units ("RSUs"), performance awards, and/or other stock‑based or cash-based awards. Upon the adoption of the 2020 Plan, the Company no longer grants new equity awards under its 2018 Plan.

Amended and Restated 2020 Equity Incentive Plan

On June 11, 2024, the Company's stockholders approved an amendment to the 2020 Plan to increase the number of shares of common stock reserved for issuance under the plan by 2,000,000 shares. As of December 31, 2024, there were 2,000,796 stock options outstanding, 981,849 RSUs outstanding, 2,165,325 performance stock units outstanding, and 185,519 shares remained available for future issuance under the 2020 Plan.

Amended and Restated 2021 Employee Stock Purchase Plan

The ESPP was adopted by the Company's Board of Directors on April 14, 2021, approved by the stockholders on June 16, 2021, and became effective on June 16, 2021. The first offering period under the ESPP commenced on September 1, 2021.

On June 6, 2023, the Company's stockholders approved an amendment and restatement of the ESPP to (i) increase the number of shares of common stock reserved for issuance under the ESPP from 73,525 to 473,525 and (ii) provide for an annual increase to be added on the first day of each fiscal year, beginning with the fiscal year ending December 31, 2024 and ending with the fiscal year ending December 31, 2033, equal to the least of (a) 293,597 shares of common stock, (b) one percent (1%) of the outstanding shares of common stock on such date and (c) the number of shares of common stock determined by the Board of Directors. The Company's Board of Directors amended and restated the ESPP on November 12, 2023 to provide for 24-month offering periods.

The number of shares of the Company’s common stock reserved for issuance under the ESPP is 677,391 shares. At December 31, 2024, 478,450 shares remained available for future issuance under the ESPP.

2024 Inducement Stock Incentive Plan

In March 2024, the Board approved the 2024 Inducement Plan, which provides for the reservation of 1,000,000 shares of common stock for equity granted as an inducement material to the individual’s entering into employment with the Company and in accordance with the requirements of Nasdaq Stock Market Rule 5635(c)(4). As of December 31, 2024, there were 100,000 stock options outstanding, 300,067 RSUs outstanding, and 599,933 shares remained available for future issuance under the 2024 Inducement Plan.

Stock Options

The table below summarizes the activity with respect to stock options for the year ended December 31, 2024:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at January 1, 2024		2,259,672		$	21.93			$	863
Granted		1,219,522			7.81
Exercised		(71,562	)		6.39
Expired		(44,521	)		31.11
Forfeitures		(435,174	)		8.93
Outstanding at December 31, 2024		2,927,937		$	18.22		8.01	$	193
Vested and expected to vest as of December 31, 2024		2,927,937		$	18.22		8.01	$	193
Exercisable at December 31, 2024		1,117,768		$	35.27		6.79	$	541

The assumptions used in the Black-Scholes option-pricing model for all stock options granted during each period presented are as follows:


	Year Ended December 31,
	2024	2023
Common stock price	$5.76-$8.64	$2.15-$7.33
Expected volatility	119.7% - 128.7%	121.8% - 129.60%
Expected dividends	0.0%	0.0%
Expected term (in years)	5.31 - 6.25	5.31 - 6.25
Risk-free rate	3.7% - 4.4%	3.5% - 4.9%

The weighted average grant date fair values of stock options granted during the years ended December 31, 2024 and 2023 were $6.96 and $4.76, respectively.

The Company recognized $5.1 million and $5.3 million of equity-based compensation expense in connection with stock options during the years ended December 31, 2024 and 2023, respectively. As of December 31, 2024, there was $9.0 million of total unrecognized equity-based compensation cost related to unvested stock options. This cost is expected to be recognized over a weighted average period of 2.3 years. The intrinsic value of stock options exercised during the years ended December 31, 2024 and 2023 was $0.3 million and $0, respectively.

Restricted Stock Units

The following table summarizes activity with respect to RSUs during the year ended December 31, 2024:


	Units			Weighted- Average Grant Date Fair Value
Nonvested RSUs at January 1, 2024		877,181		$	6.37
Granted		1,196,954		$	7.94
Vested		(335,981	)	$	6.55
Forfeitures		(257,882	)	$	6.91
Nonvested RSUs at December 31, 2024		1,480,272		$	7.50

The Company recognized $3.0 million and $2.2 million of equity-based compensation expense in connection with RSUs during the years ended December 31, 2024 and 2023, respectively. As of December 31, 2024, there was $9.0 million of total unrecognized equity-based compensation cost related to nonvested RSUs. This cost is expected to be recognized over a weighted average period of 2.9 years. The aggregate grant date fair value of RSUs vested during the years ended December 31, 2024 and 2023 was $2.2 million and $1.4 million, respectively.

Performance Stock Units

In June 2024, the Board approved a grant of performance-based restricted stock unit awards (“PSUs" or “Performance Awards”) to the Company’s executive team. Each PSU represents the contingent right to receive one share of the Company’s common stock. These Performance Awards provide for the vesting of 25% of the target number of underlying RSUs granted upon the achievement of each of four independent performance milestones predetermined by the Board (“Performance Milestones”), subject to the grantee’s continued service with the Company (the “Approval Conditions”).

The Performance Milestones are tied to the achievement of certain business objectives and are non-market and non-financial in nature. The Board will determine that all Approval Conditions have been satisfied and the number of units that will ultimately vest on the 2026 Evaluation Date, which will occur in the first quarter of 2026, and the 2027 Evaluation Date, which will occur in the first quarter of 2027. A maximum of 25% of the target number of RSUs may vest at the 2026 Evaluation Date and the percentage of the target number of RSUs allocable to any Performance Milestone that has not been achieved on or prior to the 2027 Evaluation Date shall be cancelled.

The Company granted 2,165,325 PSUs during the year ended December 31, 2024 with a weighted average grant date fair value of $7.51 per unit. During the year ended December 31, 2024, the Company recognized $2.2 million in expense for these grants.

As of December 31, 2024, there was $5.9 million of unrecognized equity-based compensation cost related to nonvested PSUs based on the achievement of all Performance Milestones. The Company expects to recognize this cost over a weighted average period of 1.9 years.

Summary of Significant Accounting Policies	12 Months Ended
Summary of Significant Accounting Policies	Dec. 31, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make estimates, judgments and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, estimates related to recognition of research and development expenses, equity-based compensation and derivative liabilities. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from the Company’s estimates. Cash Equivalents The Company considers all short-term, highly liquid investments with original maturities of 90 days or less at acquisition date to be cash equivalents. Available-for-Sale Securities Available-for-sale securities consist of investments with original maturities greater than 90 days at acquisition date. The Company has classified its investments with maturities beyond one year as short term, based on their highly liquid nature and because such available-for-sale securities represent the investment of cash that is available for current operations. The Company classifies all of its investments as available-for-sale securities. The Company’s investments are measured and reported at fair value using quoted prices in active markets for similar securities. Unrealized gains and losses on available-for-sale debt securities are reported as a separate component of stockholders’ equity. The cost of debt securities sold is determined on a specific identification basis, and realized gains and losses are included in other income, net within the consolidated statement of operations. Impairment of available-for-sale securities is evaluated considering numerous factors, and their relative significance varies depending on the situation. Factors considered include whether a decline in fair value below the amortized cost basis is due to credit-related factors or non-credit-related factors, the financial condition and near-term prospects of the issuer, and our intent and ability to hold the investment to allow for an anticipated recovery in fair value. A credit-related impairment is recognized as an allowance on the balance sheet with a corresponding adjustment to earnings. Any impairment that is not credit-related is recognized in other comprehensive income. No such adjustments were necessary during the periods presented. Concentration of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and available-for-sale securities. Periodically, the Company maintains deposits in accredited financial institutions in excess of federally insured limits. The Company maintains each of its cash, cash equivalents and available-for-sale securities balances with high-quality and accredited financial institutions and accordingly, such funds are not exposed to significant credit risk. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company is dependent on third-party manufacturers to supply products for research and development activities of its programs, including clinical and preclinical testing. These programs could be adversely affected by a significant interruption in the supply of such drug substance products. Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents and available-for-sale securities are carried at fair value, determined according to the fair value hierarchy described above. Derivative liabilities are recorded at fair value based on the probability weighted present value of the estimated cash flows pursuant to the contractual terms of each agreement. The derivative liabilities are remeasured quarterly with changes in fair value recorded in change in fair value of derivative liabilities in the consolidated statements of operations. See Note 4, Fair Value of Financial Assets and Liabilities, for additional information. The carrying values of the Company’s accounts payable and accrued expenses and other current liabilities approximate their fair value due to the short-term nature of these liabilities. Leases At the inception of a contract, the Company determines if a contract meets the definition of a lease. A lease is a contract, or part of a contract, that conveys the right to control the use of identified property, plant, or equipment (an identified asset) for a period of time in exchange for consideration. The Company determines if the contract conveys the right to control the use of an identified asset for a period of time. The Company assesses throughout the period of use whether the Company has both of the following: (1) the right to obtain substantially all of the economic benefits from use of the identified asset and (2) the right to direct the use of the identified asset. This determination is reassessed if the terms of the contract are changed. Leases are classified as operating or finance leases based on the terms of the lease agreement and certain characteristics of the identified asset. Right-of-use assets and lease liabilities are recognized at the lease commencement date based on the present value of the minimum future lease payments. Adjustments to the right-of-use asset may be required for items such as lease prepayments or incentives received. The Company’s policy is to not record leases with an original term of twelve months or less on the consolidated balance sheets. The Company recognizes lease expense for these short-term leases on a straight-line basis over the lease term. Certain lease agreements include rental payments that are adjusted periodically for inflation or other variables. In addition to rent, the leases may require the Company to pay additional amounts for taxes, insurance, maintenance and other expenses, which are generally referred to as non-lease components. Such adjustments to rental payments and variable non-lease components are treated as variable lease payments and recognized in the period in which the obligation for these payments was incurred. Variable lease components and variable non-lease components are not measured as part of the right-of-use asset and liability. Only when lease components and their associated non-lease components are fixed are they accounted for as a single lease component and recognized as part of a right-of-use asset and liability. Total contract consideration is allocated to the combined fixed lease and non-lease components. Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset. Laboratory equipment is depreciated over five years. Computer equipment is depreciated over three years. Computer software is depreciated over two years. Furniture and office equipment are depreciated over five years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Expenditures for repairs and maintenance of assets are charged to expense as incurred. Upon retirement or sale, the net book value is written off and any resulting gain or loss is included in the consolidated statements of operations. Equipment under a finance lease is stated at fair value at the inception of the lease less accumulated depreciation and is depreciated over the remaining lease term or the estimated useful life of the equipment. Impairment of Long-Lived Assets Long-lived assets, comprised of property and equipment, to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows. Exclusive Licenses If a license granted in an arrangement is determined to be distinct from the other promises or performance obligations identified in the arrangement, which generally include research and development services, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license In assessing whether a license is distinct from the other promises, the Company considers relevant facts and circumstances of each arrangement, including the research and development capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from the license for its intended purpose without the receipt of the remaining promise, whether the value of the license is dependent on the unsatisfied promise, whether there are other vendors that could provide the remaining promise, and whether it is separately identifiable from the remaining promise. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The measure of progress, and thereby periods over which revenue should be recognized, are subject to estimates by management and may change over the course of the arrangement. Research and Development Services The promises under the Company’s collaboration and license agreements generally include research and development services to be performed by the Company on behalf of the collaboration partner. For performance obligations that include research and development services, the Company generally recognizes revenue allocated to such performance obligations based on an appropriate measure of progress. The Company utilizes judgment to determine the appropriate method of measuring progress for purposes of recognizing revenue, which is generally an input measure, such as costs incurred. Milestone Payments At the inception of each arrangement that includes milestone payments based on certain events, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company, such as regulatory approvals, are not considered probable of being achieved until those approvals are received or the specified event occurs. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. If a milestone or other variable consideration relates specifically to the Company’s efforts to satisfy a single performance obligation or to a specific outcome from satisfying the performance obligation, the Company generally allocates the milestone amount entirely to that performance obligation once it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. Royalties For arrangements that include sales-based royalties, including milestone payments based on a level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements. Collaboration Revenue The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For collaboration arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of ASC 808 and those that are more reflective of a vendor-customer relationship and therefore within the scope of ASC 606, Revenue from Contracts with Customers (“ASC 606”). For elements of collaboration arrangements that are accounted for pursuant to ASC 808, an appropriate recognition method is determined and applied consistently, generally by analogy to ASC 606. Costs Associated with License and Collaborative Arrangements All costs associated with license and collaborative arrangements are expensed as incurred and recorded in research and development expense in the consolidated statements of operations. Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses include salaries, equity-based compensation and benefits of employees, third-party license fees and other operational costs related to the Company’s research and development activities, including allocated facility-related expenses and external costs of outside vendors engaged to conduct both preclinical studies and clinical trials. Non-refundable pre-payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are recognized as expense as the goods or services are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered. The Company may in-license the rights to develop and commercialize product candidates. For each in-license transaction the Company evaluates whether it has acquired processes or activities along with inputs that would be sufficient to constitute a “business” as defined under GAAP. A “business” as defined under GAAP consists of inputs and processes applied to those inputs that have the ability to create outputs. Although businesses usually have outputs, outputs are not required for an integrated set of activities to qualify as a business. When the Company determines that it has not acquired sufficient processes or activities to constitute a business, any upfront payments, as well as milestone payments, are immediately expensed as acquired research and development in the period in which they are incurred. Research Contract Costs and Accruals The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Estimates based on available information are made in determining the accrual balances at the end of any reporting period. Actual results could differ from the Company's estimates; however, the Company's historical accrual estimates have not been materially different from the actual costs. Patent Costs All patent-related costs incurred for filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses. Equity-Based Compensation The Company measures all stock options and other stock-based awards granted to employees, directors and non-employees based on the fair value on the date of the grant and recognizes compensation expense of those awards, over the requisite service period, which is generally the vesting period of the respective award. Forfeitures are accounted for as they occur. The Company applies the straight-line method of expense recognition to all awards with only service-based vesting conditions. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. In the first quarter of 2024, the Company determined that it has adequate historical stock price data to utilize solely its own stock for historical volatility purposes. The expected term of stock options with service-based vesting conditions and options granted to non-employees has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The Company utilized a 0% expected dividend yield in its determination of grant fair value based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future, if ever. The fair values of restricted stock units and performance-based restricted stock units are measured at the grant date based on the closing price of the Company’s common stock on the date of grant. For restricted stock units, the fair value of the award is recognized on a straight-line basis over the requisite service periods. For performance-based restricted stock unit awards, which are subject to the achievement of performance milestones, the fair value is recognized as expense over the requisite service periods when the achievement of such performance milestones is determined to be probable. If a performance milestone is not determined to be probable or is not met, no equity-based compensation expense is recognized, and any previously recognized expense is reversed. Forfeitures are recognized as a reduction of equity-based compensation expense as they occur. The Company classifies stock-based compensation expense in its consolidated statements of operations in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified. The Company does not currently hold any treasury shares. Upon the exercise of stock options and the vesting of restricted stock units and performance stock units, the Company issues new shares of common stock and delivers them to the participant. Income Taxes Income taxes are accounted for under the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company records valuation allowances to reduce deferred income tax assets to the amount that is more likely than not to be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, no amount of benefit attributable to the position is recognized. The tax benefit to be recognized of any tax position that meets the more likely than not recognition threshold is calculated as the largest amount that is more than 50% likely of being realized upon resolution of the contingency. Prior to January 25, 2018, the Company had not been subject to U.S. federal income taxes as the Company was organized as a limited liability company. As such, the taxable income or loss was passed through to and included in the tax returns of the members. Since January 25, 2018, the Company’s income has since been subject to U.S. federal, state, local, and foreign income taxes and taxed at the prevailing corporate tax rates. Segment Data The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on developing treatments through gene therapy and other means for patients with neuromuscular and cardiac diseases. All of the Company’s tangible assets are held in the United States. Please refer to Note 17, Segment Reporting for further information. Comprehensive Loss Comprehensive loss includes net loss, as well as other changes in stockholders’ equity that result from transactions and economic events other than those with members. The Company’s only element of other comprehensive income in all periods presented was unrealized gains from available-for-sale securities. Net Loss per Share The Company follows the two-class method when computing net loss per share, as the Company has issued shares that meet the definition of participating securities. The two-class method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and pre-funded warrants outstanding for the period. Diluted net loss is computed by adjusting net loss to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share is computed by dividing the diluted net loss by the weighted average number of shares of common stock and pre-funded warrants outstanding for the period, including potential dilutive shares of common stock assuming the dilutive effect of common stock equivalents. Any preferred stock that the Company may issue in the future could entitle the holders of such shares to participate in dividends and not require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss, diluted net loss per share is the same as basic net loss per share, since dilutive shares of common stock are not assumed to have been issued if their effect is anti-dilutive. As of December 31, 2024 and 2023, there was no preferred stock issued or outstanding with any contractual rights. Contingencies Loss contingency provisions are recorded if the potential loss from any claim, asserted or unasserted, or legal proceeding, is considered probable and the amount can be reasonably estimated, or a range of loss can be determined. These accruals represent the Company’s best estimate of probable loss. Disclosure also is provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. The Company reviews the status of each significant matter and assesses its potential financial exposure. Significant judgment is required in both the determination of probability and the determination as to whether an exposure is reasonably estimable. Because of uncertainties related to these matters, accruals are based only on the best information available at the time. As additional information becomes available, the Company reassesses the potential liability related to pending claims and may change its estimates. These changes in the estimates of the potential liabilities could have a material impact on the Company’s consolidated results of operations and financial position. Business Combinations The Company's consolidated financial statements include the operations of acquired businesses after the completion of the acquisitions. The Company accounts for acquired businesses using the acquisition method of accounting. Application of this method of accounting requires that (i) identifiable assets acquired (including identifiable intangible assets) and liabilities assumed be measured and recognized at fair value as of the acquisition date, and (ii) the excess of the purchase price over the net fair value of identifiable assets acquired and liabilities assumed be recorded as goodwill. Acquired in-process research and development (“IPR&D”) is recognized at fair value and initially characterized as an indefinite-lived intangible asset, irrespective of whether the acquired IPR&D has an alternative future use. Transaction costs are expensed as incurred. Amounts assigned to goodwill and other identifiable intangible assets are based on independent appraisals or internal estimates. Asset Acquisitions Acquisitions of assets or a group of assets that do not meet the definition of a business are accounted for as asset acquisitions using the cost accumulation method, whereby the cost of the acquisition, including certain transaction costs, is allocated to the assets acquired on the basis of relative fair values. No goodwill is recognized in an asset acquisition. Intangible assets that are acquired in an asset acquisition for use in research and development activities which have an alternative future use are capitalized as IPR&D. Acquired IPR&D which has no alternative future use is recognized as research and development expense at acquisition. Contingent milestone payments associated with asset acquisitions are recognized when probable and estimable. These amounts are expensed to research and development if there is no alternative future use associated with the asset or capitalized as an intangible asset if an alternative future use of the asset exists. Recently Issued Accounting Pronouncements In December 2023, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("ASU") No. 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” This ASU updates income tax disclosure requirements primarily by requiring specific categories and greater disaggregation within the rate reconciliation and disaggregation of income taxes paid by jurisdiction. This ASU is effective for annual periods beginning after December 15, 2024 and is applicable to the Company’s fiscal year beginning January 1, 2025, with early application permitted. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and disclosures. In November 2024, the FASB issued ASU No. 2024-03, "Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Sub-Topic 220-40): Disaggregation of Income Statement Expenses," which requires additional disclosure of the nature of expenses included in the income statement. The standard requires disclosures about specific types of expenses included in the expense captions presented in the income statement. This ASU is effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. The requirements should be applied on a prospective basis while retrospective application is permitted. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and disclosures. Recently Adopted Accounting Pronouncements On November 27, 2023, the FASB issued ASU No. 2023-07, "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures." Among other new disclosure requirements, ASU 2023-07 requires companies to disclose significant segment expenses that are regularly provided to the chief operating decision maker. We adopted the standard effective December 31, 2024 and applied the disclosure requirements retrospectively to all prior periods presented in the financial statements. Adoption of ASU 2023-07 did not have an impact on the Company’s consolidated financial position, results of operations, or cash flows.

Fair Value of Financial Assets and Liabilities - Summary of Fair Value of Derivative Liabilities (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2024	Dec. 31, 2023
Financial Liabilities Fair Value Disclosure [Abstract]
Fair value of derivative liabilities as of September 19, 2024	$ 3,400
Change in fair value of derivative liabilities	4,750	$ (4,750)	$ 0
Reclassification of accrued milestone payment to accrued expenses and other current liabilities	(5,000)
Fair value of derivative liabilities as of December 31, 2024	$ 3,150	$ 3,150

- Definition

Fair value, after the 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 not subject to a master netting arrangement and not elected to be offset.

+ References

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+ Details

Restructuring - Schedule of Balance of Accrued Restructuring Charges and Changes in Accrued Amounts in Connection with Associated Restructuring Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Restructuring Cost and Reserve [Line Items]
Accrual recorded as a result of restructuring charges		$ (63)
One-Time Employee Termination Benefits [Member] \| November 2022 Workforce Reduction Plan [Member]
Restructuring Cost and Reserve [Line Items]
Accrued restructuring charges, beginning balance	$ 252	3,921
Amounts paid during the period	$ (252)	(3,669)
Accrued restructuring charges, ending balance		$ 252

- 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

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development expenses	$ 6,731	$ 3,980
Prepaid other and other current assets	1,651	2,114
Prepaid expenses and other current assets	$ 8,382	$ 6,094

Nature of the Business and Basis of Presentation

12 Months Ended

Dec. 31, 2024

Accounting Policies [Abstract]

Nature of the Business and Basis of Presentation

1. Nature of the Business and Basis of Presentation

Nature of Business

Solid Biosciences Inc. was organized in March 2013 under the name SOLID Ventures Management, LLC and operated as a Delaware limited liability company until immediately prior to the effectiveness of its registration statement on Form S-1 on January 25, 2018, at which time it completed a statutory corporate conversion into a Delaware corporation and changed its name to Solid Biosciences Inc. (the “Company”). On December 2, 2022, the Company completed its acquisition of AavantiBio, Inc. (“AavantiBio”), a privately held gene therapy company focused on transforming the lives of patients with Friedreich’s ataxia (“FA”) and rare cardiomyopathies (the “Acquisition”). Upon the consummation of the Acquisition, the Company acquired AavantiBio’s gene therapy programs, AVB‑202‑TT for FA and AVB‑401 for BAG3 mediated dilated cardiomyopathy, as well as additional assets for the treatment of other cardiac diseases, platform technologies and know-how related thereto. AavantiBio is a wholly owned subsidiary of the Company.

The Company is a life sciences company focused on advancing a portfolio of current and future gene therapy candidates (collectively, “Candidates”), including SGT-003 for the treatment of Duchenne muscular dystrophy (“Duchenne”), SGT-212 for the treatment of FA, SGT-501 for the treatment of catecholaminergic polymorphic ventricular tachycardia, SGT-601 for the treatment of TNNT2-mediated dilated cardiomyopathy, and additional assets for the treatment of genetic cardiac and other diseases, at different stages of development with varying levels of investment. The Company is advancing its diverse pipeline across rare neuromuscular and cardiac diseases, bringing together experts in science, technology, disease management and care. Patient-focused and founded by those directly impacted by Duchenne, the Company’s mission is to improve the daily lives of patients living with these devastating diseases.

The Company is subject to risks and uncertainties common to early-stage companies in the biotechnology industry, including, but not limited to, development by competitors of new technological innovations, dependence on licenses, protection of proprietary technology, dependence on key personnel, compliance with government regulations and the need to obtain additional financing to fund operations. Candidates currently under development will require significant additional research and development efforts, including extensive preclinical studies and clinical trials and regulatory approval, prior to commercialization. These efforts require significant amounts of additional capital, adequate personnel infrastructure and extensive compliance and reporting capabilities.

The Company’s Candidates are in development. 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, 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, among others, other pharmaceutical and biotechnology companies. In addition, the Company is dependent upon the services of its employees, partners, and consultants.

Liquidity

The accompanying consolidated financial statements have been prepared on a basis that assumes the Company will continue as a going concern and which contemplates the realization of assets and satisfaction of liabilities and commitments in the ordinary course of business. Through December 31, 2024, the Company has funded its operations primarily with the proceeds from the sale of redeemable preferred units and member units as well as the sale of common stock and pre-funded warrants to purchase shares of its common stock in private placements and the sale of common stock in its initial public offering and follow-on public offering in March 2021 and under its at-the-market sales agreement.

On January 11, 2024, the Company issued and sold in a private placement 16,973,103 shares of the Company’s common stock at a price per share of $5.53 and, to one investor in lieu of shares of common stock, pre-funded warrants to purchase 2,712,478 shares of common stock at a price of $5.529 per pre-funded warrant (the “January 2024 Private Placement”). The Company received $103.7 million of net proceeds from the January 2024 Private Placement after deducting offering costs. No warrants were exercised during the year ended December 31, 2024.

During the year ended December 31, 2024, the Company issued 2,212,937 shares of its common stock, pursuant to the Company's “at-the-market offering” sales agreement, between the Company and Jefferies LLC (the “ATM Sales Agreement”) for net proceeds of $18.4 million.

On February 19, 2025, the Company issued and sold 35,739,810 shares of its common stock at a price per share of $4.03 and, to certain investors in lieu of shares of common stock, pre-funded warrants to purchase 13,888,340 shares of common stock at a price of $4.029 per pre-funded warrant (the “February 2025 Offering"). The Company received approximately $187.5 million of net proceeds from the February 2025 Offering after deducting underwriting discounts and commissions and estimated offering costs.

In accordance with Accounting Standards Codification (“ASC”) 205-40, Going Concern, the Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. As of December 31, 2024, the Company had an accumulated deficit of $783.5 million. During the years ended December 31, 2024 and 2023, the Company incurred net losses of $124.7 million and $96.0 million, respectively. The Company used $100.0 million of cash in operations for the year ended December 31, 2024. The Company expects to continue to generate operating losses in the foreseeable future. Based upon its current operating plan, the Company expects that its cash, cash equivalents and available-for-sale securities of $148.9 million, excluding restricted cash of $2.0 million, as of December 31, 2024, together with the net proceeds from the February 2025 Offering, will be sufficient to fund its operating expenses and capital expenditure requirements for at least twelve months from the date of issuance of these financial statements. However, the Company has based this estimate on assumptions that may prove to be wrong, and its operating plan may change as a result of many factors currently unknown to it. As a result, the Company could deplete its capital resources sooner than it currently expects. The Company expects to finance its future cash needs through a combination of equity offerings, debt financings, collaborations, strategic alliances or licensing arrangements. If the Company is unable to obtain funding, the Company would be forced to delay, reduce or eliminate some or all of its research and development programs, preclinical and clinical testing or commercialization efforts, which could adversely affect its business prospects.

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying consolidated financial statements include the accounts of the Company and its wholly owned or controlled subsidiaries. All intercompany accounts and transactions have been eliminated.

Reclassifications

Certain prior period amounts within cash flows from operating activities in the consolidated statement of cash flows have been reclassified to conform to the current period presentation. These reclassifications are not material and had no effect on the previously reported net cash used in operating activities.

Leases - Summary of Components of Lease Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Lease, Cost [Abstract]
Operating lease cost	$ 4,961	$ 5,250
Finance lease cost:
Amortization of right-of-use assets	441	476
Interest on lease liabilities	340	440
Sub-lease income	(963)	(1,094)
Total lease cost	$ 4,779	$ 5,072

Net Loss per Share

12 Months Ended

Dec. 31, 2024

Earnings Per Share [Abstract]

Net Loss per Share

13. Net Loss per Share

The following table sets forth the computation of the Company's basic and diluted net loss per share:


	Year Ended December 31,
	2024			2023
Numerator:
Net loss	$	(124,697	)	$	(96,015	)
Denominator:
Shares used to compute net loss per share, basic and diluted
Weighted average shares of common stock outstanding		38,178,327			19,884,007
Weighted average pre-funded warrants to purchase shares of common stock		2,638,367			—
Weighted average shares of common stock used to compute basic and diluted net loss per share		40,816,694			19,884,007
Net loss per share, basic and diluted	$	(3.06	)	$	(4.83	)

Included within weighted average shares of common stock outstanding for the year ended December 31, 2024 are 2,712,478 shares of common stock issuable upon the exercise of the pre-funded warrants as the pre-funded warrants are exercisable at any time for nominal consideration, and as such, the shares are considered outstanding for the purpose of calculating basic and diluted net loss per share. There were no pre-funded warrants issued and outstanding during the year ended December 31, 2024.

The outstanding securities presented below were excluded from the calculation of net loss per share because the inclusion of such securities would have been anti-dilutive due to the Company’s net loss per share during the periods presented.


	Year Ended December 31,
	2024		2023
Options to purchase common stock		2,927,937		2,259,672
Nonvested restricted stock units		1,480,272		877,181
Nonvested performance stock units		2,165,325		—
Shares subject to employee stock purchase plan		281,640		—
Warrants		9,230		—
Total		6,864,404		3,136,853

Segment Reporting - Additional Information (Detail)	12 Months Ended
Segment Reporting - Additional Information (Detail)	Dec. 31, 2024 Segment
Segment Reporting [Abstract]
Number of reportable segment	1
Number of operating segment	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 CODM assesses performance for the Company and decides how to allocate resources based on net loss as reported on the consolidated statements of operations. The annual budgeting process is the primary mechanism used to make these decisions.

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2024	Dec. 31, 2023
Office and Laboratory Lease [Member]
Commitment And Contingencies [Line Items]
Letter of credit outstanding amount	$ 2.0	$ 1.8

Income Taxes

12 Months Ended

Dec. 31, 2024

Income Tax Disclosure [Abstract]

Income Taxes

14. Income Taxes

The Company recorded no tax benefit for the years ended December 31, 2024 and 2023 for the net operating losses incurred due to its uncertainty of realizing a benefit from those items.

A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations as of December 31, 2024 and 2023 is as follows:


	December 31,
	2024			2023
Income tax computed at federal statutory tax rate		21.0	%		21.0	%
State taxes, net of federal benefit		6.6	%		6.6	%
Permanent differences		(0.1	)%		(0.5	)%
Tax credits		6.3	%		7.0	%
Change in deferred tax rate		(2.5	)%		0.2	%
Stock compensation cancelations		(0.2	)%		(1.0	)%
Impact of ownership change		—			(108.5	)%
Other items		0.2	%		0.4	%
Valuation allowance		(31.3	)%		74.8	%
Total		—			—

The Company established deferred tax assets and liabilities on identified book to tax temporary differences as of the date of conversion to a C-corporation. Deferred income taxes reflect the net tax effects of these temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. Significant components of the Company’s net deferred tax assets as of December 31, 2024 and 2023 are as follows:


	December 31,
	2024			2023
Deferred tax assets:
Tax loss carryforwards	$	37,183		$	16,622
Tax credit carryforwards		15,324			7,537
Deferred expenses		6,067			6,755
Accrued expenses		1,536			1,506
Stock compensation		9,986			8,496
Intangible assets		2,535			203
Capitalized R&D		63,087			57,133
Depreciation		—			672
Derivative liabilities		833			—
Other		53			80
Total deferred tax assets		136,604			99,004
Valuation allowance		(130,690	)		(91,705	)
Deferred tax liabilities:
Right-of-use asset		(5,570	)		(7,299	)
Depreciation		(344	)		—
Total deferred tax liabilities		(5,914	)		(7,299	)
Net deferred taxes	$	—		$	—

As of December 31, 2024, the Company had federal net operating loss carryforwards of $133.3 million which may be available to offset future taxable income and do not expire but are limited in their usage to an annual deduction equal to 80% of annual taxable income. In addition, as of December 31, 2024, the Company had state net operating loss carryforwards of approximately $146.5 million which may be available to offset future taxable income, of which $143.3 million begins to expire in 2032 and $3.2 million has unlimited carryforward. The Company also had federal and state tax credits of $13.1 million and $2.8 million, respectively, which may be used to offset future tax liability and each of which begin to expire in 2037.

The Company’s ability to utilize these federal and state carryforwards may be limited in the future if the Company experiences an ownership change pursuant to Section 382 of the Internal Revenue Code of 1986, as amended (the "Internal Revenue Code"). Ownership changes, as defined in the Internal Revenue Code, including those resulting from the issuance of common stock in connection with the Company’s public offerings, may limit the amount of net operating loss and tax credit carryforwards that can be utilized to offset future taxable income or tax liability. The Company completed a study in 2023 to assess whether a change of control had occurred under Section 382, and it was determined that all net operating loss carryforwards and credits generated before December 2, 2022 are limited. As a result, the carryforwards before the ownership change date of December 2, 2022 are not available for utilization and have been written off. The carryforwards as of December 31, 2024 were generated after the ownership change of December 2, 2022.

A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. The Company has evaluated the positive and negative evidence bearing upon the realizability of the deferred tax assets. The Company concluded, in accordance with the applicable accounting standards, that it is more likely than not that the Company will be unable to realize the benefit of its deferred tax assets. Accordingly, the Company has recorded a full valuation allowance against its deferred tax assets.

The following table presents the changes in the balance of the Company’s deferred income tax asset valuation allowance:


	December 31,
	2024		2023
Valuation allowance at beginning of year	$	91,705	$	163,566
Increases (decreases) recorded to income tax provision		38,985		(71,861	)
Valuation allowance at end of year	$	130,690	$	91,705

The Company files tax returns as prescribed by the tax laws of the jurisdictions in which it operates. In the normal course of business, the Company is subject to examination by federal and state jurisdictions, where applicable. There are currently no pending income tax examinations. The Company’s C-Corporation tax years beginning with the year ended December 31, 2020 are open under statute. Any tax credit or net operating loss carryforward can be adjusted in future periods after the respective year of generation’s statute of limitation has closed.

As of December 31, 2024 and 2023, the Company did not have unrecognized tax benefits. The Company recognizes interest and penalties related to income taxes as a component of income tax expense. As of December 31, 2024 and 2023, no interest and penalties have been recorded.

- Definition

The entire disclosure for income tax.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Topic 740
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-Name Accounting Standards Codification
-Section 55
-Paragraph 231
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-URI https://asc.fasb.org/1943274/2147482663/740-10-55-231

Reference 3: 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 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
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-Name Accounting Standards Codification
-Section 50
-Paragraph 12B
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482685/740-10-50-12B

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 270
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477891/740-270-50-1

Reference 6: 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 7: 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 8: 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 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 740
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org/740/tableOfContent

Reference 10: 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 11: 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 12: 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 13: 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 14: 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

Restructuring (Tables)

12 Months Ended

Dec. 31, 2024

Restructuring and Related Activities [Abstract]

Schedule of Balance of Accrued Restructuring Charges and Changes in Accrued Amounts in Connection with Associated Restructuring Plans


One-Time Employee Termination Benefits	November 2022
Accrued restructuring charges as of December 31, 2022	$	3,921
Accrual recorded as a result of restructuring charges		—
Amounts paid during the period		(3,669	)
Accrued restructuring charges as of December 31, 2023	$	252
Accrual recorded as a result of restructuring charges		—
Amounts paid during the period		(252	)
Accrued restructuring charges as of December 31, 2024	$	—

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2024

Income Tax Disclosure [Abstract]

Schedule of Reconciliation of Income Taxes Computed by U.S. Federal Statutory Rate

A reconciliation of income taxes computed using the U.S. federal statutory rate to that reflected in operations as of December 31, 2024 and 2023 is as follows:


	December 31,
	2024			2023
Income tax computed at federal statutory tax rate		21.0	%		21.0	%
State taxes, net of federal benefit		6.6	%		6.6	%
Permanent differences		(0.1	)%		(0.5	)%
Tax credits		6.3	%		7.0	%
Change in deferred tax rate		(2.5	)%		0.2	%
Stock compensation cancelations		(0.2	)%		(1.0	)%
Impact of ownership change		—			(108.5	)%
Other items		0.2	%		0.4	%
Valuation allowance		(31.3	)%		74.8	%
Total		—			—

Schedule of Net Deferred Tax Assets

Significant components of the Company’s net deferred tax assets as of December 31, 2024 and 2023 are as follows:


	December 31,
	2024			2023
Deferred tax assets:
Tax loss carryforwards	$	37,183		$	16,622
Tax credit carryforwards		15,324			7,537
Deferred expenses		6,067			6,755
Accrued expenses		1,536			1,506
Stock compensation		9,986			8,496
Intangible assets		2,535			203
Capitalized R&D		63,087			57,133
Depreciation		—			672
Derivative liabilities		833			—
Other		53			80
Total deferred tax assets		136,604			99,004
Valuation allowance		(130,690	)		(91,705	)
Deferred tax liabilities:
Right-of-use asset		(5,570	)		(7,299	)
Depreciation		(344	)		—
Total deferred tax liabilities		(5,914	)		(7,299	)
Net deferred taxes	$	—		$	—

Schedule of Deferred Income Tax Asset Valuation Allowance

The following table presents the changes in the balance of the Company’s deferred income tax asset valuation allowance:


	December 31,
	2024		2023
Valuation allowance at beginning of year	$	91,705	$	163,566
Increases (decreases) recorded to income tax provision		38,985		(71,861	)
Valuation allowance at end of year	$	130,690	$	91,705

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 80,235	$ 74,015
Available-for-sale securities	68,685	49,625
Prepaid expenses and other current assets	8,382	6,094
Total current assets	157,302	129,734
Non-current assets:
Operating lease, right-of-use asset	24,295	26,539
Property and equipment, net	4,747	6,624
Other non-current assets	366	209
Restricted cash	1,952	1,833
Total non-current assets	31,360	35,205
Total assets	188,662	164,939
Current liabilities:
Accounts payable	4,237	2,032
Accrued expenses and other current liabilities	19,852	10,161
Operating lease liabilities	1,787	1,855
Finance lease liabilities	1,231	469
Derivative liabilities	3,150	0
Total current liabilities	30,257	14,517
Non-current liabilities:
Operating lease liabilities, net of current portion	21,159	22,707
Finance lease obligations, net of current portion	0	1,234
Total non-current liabilities	21,159	23,941
Total liabilities	51,416	38,458
Commitments and Contingencies (Note 11)
Stockholders’ Equity:
Preferred stock, $0.001 par value; 10,000,000 shares authorized at December 31, 2024 and 2023; no shares issued and outstanding at December 31, 2024 and 2023
Common stock, $0.001 par value; 120,000,000 and 60,000,000 shares authorized at December 31, 2024 and 2023, respectively; 40,468,141 and 20,386,606 shares issued and outstanding at December 31, 2024 and 2023, respectively	40	20
Additional paid-in capital	920,609	785,199
Accumulated other comprehensive income	47	15
Accumulated deficit	(783,450)	(658,753)
Total stockholders' equity	137,246	126,481
Total liabilities and stockholders' equity	$ 188,662	$ 164,939

Property and Equipment - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Depreciation and amortization expense	$ 2,500,000	$ 2,600,000
Impairment loss	$ 0	$ 400,000
Impairment, Long-Lived Asset, Held-for-Use, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)

Income Taxes - Schedule of Reconciliation of Income Taxes Computed by U.S. Federal Statutory Rate (Detail)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Income tax computed at federal statutory tax rate	21.00%	21.00%
State taxes, net of federal benefit	6.60%	6.60%
Permanent differences	(0.10%)	(0.50%)
Tax credits	6.30%	7.00%
Change in deferred tax rate	(2.50%)	0.20%
Stock compensation cancelations	(0.20%)	(1.00%)
Impact of ownership change	0.00%	(108.50%)
Other items	0.20%	0.40%
Valuation allowance	(31.30%)	74.80%
Total	0.00%	0.00%

Defined Contribution Plan

12 Months Ended

Dec. 31, 2024

Retirement Benefits [Abstract]

Defined Contribution Plan

15. Defined Contribution Plan

The Company has a defined contribution savings plan under Section 401(k) of the Internal Revenue Code. The plan covers substantially all employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pretax basis. Company contributions to the plan may be made at the discretion of the Company’s Board of Directors. The Company made $0.6 million of contributions during each of the years ended December 31, 2024 and 2023.

FA212 Asset Acquisition

12 Months Ended

Dec. 31, 2024

Asset Acquisition [Abstract]

FA212 Asset Acquisition

3. FA212 Asset Acquisition

On September 19, 2024, the Company entered into an asset purchase agreement with FA212 LLC ("FA212") for the purchase of certain intellectual property, including patents and assigned licenses related to a pre-clinical drug candidate, which the Company now refers to as SGT-212, assigned manufacturing contracts as well as research and development materials such as manufactured materials and samples.

The Company paid FA212 an upfront payment of $1.0 million. Additionally, the Company agreed to pay FA212 development milestone payments of up to $34.0 million, cumulative sales milestone payments of up to $21.0 million, and

tiered royalties on net sales in the low-single-digits. The Company also assumed from FA212 contingent development milestone payments of up to $4.2 million, regulatory milestone payments of up to $13.0 million, cumulative sales milestone payments of up to $27.5 million, and tiered royalties on worldwide net sales in the mid-single digits payable to the University of Pennsylvania.

Certain development milestone payments to FA212 are payable in either cash, equity, or a combination of both, at the Company's discretion. Such contingent payments were determined to be derivative liabilities and were initially recorded at their fair value of $3.4 million, see Note 4, Fair Value of Financial Assets and Liabilities.

The Company determined that the FA212 agreement represented an asset acquisition of IPR&D assets with no alternative future use and recognized the aggregate acquisition cost of $5.1 million as research and development expense in the consolidated statement of operations for the year ended December 31, 2024, which included the upfront payment, initial recognition of the derivative liability and $0.7 million in transaction costs.

The Company submitted an investigational new drug application ("IND") for SGT-212 for the treatment of FA to the U.S. Food and Drug Administration ("FDA"), which was cleared in December 2024. Upon clearance of the IND, a $5.0 million development milestone became payable to FA212. The $5.0 million milestone liability payment is included in Accrued expenses and other current liabilities in the accompanying consolidated balance sheet as of December 31, 2024. The derivative liabilities for the remaining contingent payments were recorded at a fair value of $3.2 million as of December 31, 2024.

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2024
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

Leases

12 Months Ended

Dec. 31, 2024

Leases [Abstract]

Leases

10. Leases

The Company has operating leases for laboratory and office space in Massachusetts and North Carolina.

In June 2021, the Company entered into a lease with Hood Park LLC (“Landlord”), pursuant to which the Company leases approximately 49,869 square feet of office, laboratory, research and development and manufacturing space located in Charlestown, Massachusetts (“Premises”). The Company relocated its corporate headquarters to the Premises in June 2022. The initial term of the lease commenced in June 2022 when the construction of the lessor assets was substantially completed and continues for a ten-year period, unless earlier terminated. The lease provides the Company with an option to extend the lease for an additional five-year term. The Company and the Landlord were each obligated to undertake certain improvements prior to the commencement of the lease, and significant improvements were completed as of June 2022. The monthly lease payment is approximately $0.3 million with annual escalation of approximately 3%. The lease includes a $10.2 million construction allowance which is considered a lease incentive and included within the right-of-use asset. The Company was required to post a customary letter of credit in the amount of $1.8 million, subject to decrease on a set schedule, as a security deposit pursuant to the lease.

On December 22, 2022, the Company entered into a sub-lease agreement (the "Sub-Lease") with Arkea Bio Corp ("Arkea"). The Sub-Lease permits use by Arkea of a portion of the space leased by the Company at 500 Rutherford Avenue in Charlestown, Massachusetts. The Company subleased approximately 12,461 square feet of the 49,869 square foot building interior space. The Sub‑Lease term originally ended on February 28, 2025. The Sub-Lease was subsequently amended by the Sub-Lease Amendment, by and between Arkea and the Company, dated May 10, 2024, to increase the subleased area to approximately 13,714 square feet and extend the term to February 29, 2028.

As of December 31, 2024, minimum future lease payments for these operating and finance leases were as follows:


	Finance Leases			Operating Leases
2025	$	651		$	4,176
2026		—			4,284
2027		—			4,280
2028		—			4,364
Thereafter		—			17,118
Total		651			34,222
Less: Imputed Interest		(580	)		11,276
Total Lease Liabilities	$	1,231		$	22,946

The following table shows the components of lease costs:


	Year Ended December 31,
Lease cost	2024			2023
Operating lease cost	$	4,961		$	5,250
Finance lease cost:
Amortization of right-of-use assets		441			476
Interest on lease liabilities		340			440
Sub-lease income		(963	)		(1,094	)
Total lease cost	$	4,779		$	5,072

Short-term lease and variable lease costs were not material for the years ended December 31, 2024 and 2023.

The following table shows the weighted average remaining lease term and weighted average discount rate of the Company’s leases are as follows:


	Year Ended December 31,
	2024			2023
Weighted-average remaining lease term (in years)
Operating lease		7.6			8.5
Finance lease		0.8			1.8
Weighted-average discount rate
Operating lease		10.8	%		10.7	%
Finance lease		22.8	%		22.8	%

Available-for-Sale Securities (Tables)

12 Months Ended

Dec. 31, 2024

Investments, Debt and Equity Securities [Abstract]

Schedule of Available-for-Sale Securities

A summary of the Company’s available-for-sale securities is presented below:


	December 31, 2024
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Treasury bills maturing in one year or less	$	27,879	$	16	$	—	$	27,895
Government bonds maturing in one year or less		40,759		31		—	$	40,790
Total available-for-sale securities	$	68,638	$	47	$	—	$	68,685


	December 31, 2023
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Treasury bills maturing in one year or less	$	49,610	$	15	$	—	$	49,625
Total available-for-sale securities	$	49,610	$	15	$	—	$	49,625

- Definition

Tabular disclosure of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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+ Details

Equity-Based Compensation - Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility, Minimum	119.70%	121.80%
Expected volatility, Maximum	128.70%	129.60%
Expected dividends	0.00%	0.00%
Risk-free rate, Minimum	3.70%	3.50%
Risk-free rate, Maximum	4.40%	4.90%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock price	$ 5.76	$ 2.15
Expected term (in years)	5 years 3 months 21 days	5 years 3 months 21 days
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock price	$ 8.64	$ 7.33
Expected term (in years)	6 years 3 months	6 years 3 months

Available-for-Sale Securities - Schedule of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 68,638	$ 49,610
Gross Unrealized Gain	47	15
Fair Value	68,685	49,625
Treasury Bills Maturing in One Year or Less [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	27,879	49,610
Gross Unrealized Gain	16	15
Fair Value	27,895	$ 49,625
Government Bonds Maturing in One Year or Less [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	40,759
Gross Unrealized Gain	31
Fair Value	$ 40,790

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- 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.

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+ Details

Summary of Significant Accounting Policies (Policies)	12 Months Ended
Summary of Significant Accounting Policies (Policies)	Dec. 31, 2024
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make estimates, judgments and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, estimates related to recognition of research and development expenses, equity-based compensation and derivative liabilities. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from the Company’s estimates.
Cash Equivalents	Cash Equivalents The Company considers all short-term, highly liquid investments with original maturities of 90 days or less at acquisition date to be cash equivalents.
Available-for-Sale Securities	Available-for-Sale Securities Available-for-sale securities consist of investments with original maturities greater than 90 days at acquisition date. The Company has classified its investments with maturities beyond one year as short term, based on their highly liquid nature and because such available-for-sale securities represent the investment of cash that is available for current operations. The Company classifies all of its investments as available-for-sale securities. The Company’s investments are measured and reported at fair value using quoted prices in active markets for similar securities. Unrealized gains and losses on available-for-sale debt securities are reported as a separate component of stockholders’ equity. The cost of debt securities sold is determined on a specific identification basis, and realized gains and losses are included in other income, net within the consolidated statement of operations. Impairment of available-for-sale securities is evaluated considering numerous factors, and their relative significance varies depending on the situation. Factors considered include whether a decline in fair value below the amortized cost basis is due to credit-related factors or non-credit-related factors, the financial condition and near-term prospects of the issuer, and our intent and ability to hold the investment to allow for an anticipated recovery in fair value. A credit-related impairment is recognized as an allowance on the balance sheet with a corresponding adjustment to earnings. Any impairment that is not credit-related is recognized in other comprehensive income. No such adjustments were necessary during the periods presented.
Concentration of Credit Risk and of Significant Suppliers	Concentration of Credit Risk and of Significant Suppliers Financial instruments that potentially expose the Company to concentrations of credit risk consist primarily of cash, cash equivalents and available-for-sale securities. Periodically, the Company maintains deposits in accredited financial institutions in excess of federally insured limits. The Company maintains each of its cash, cash equivalents and available-for-sale securities balances with high-quality and accredited financial institutions and accordingly, such funds are not exposed to significant credit risk. The Company does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships. The Company is dependent on third-party manufacturers to supply products for research and development activities of its programs, including clinical and preclinical testing. These programs could be adversely affected by a significant interruption in the supply of such drug substance products.
Fair Value Measurements	Fair Value Measurements Certain assets and liabilities are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable: • Level 1—Quoted prices in active markets for identical assets or liabilities. • Level 2—Observable inputs (other than Level 1 quoted prices), such as quoted prices in active markets for similar assets or liabilities, quoted prices in markets that are not active for identical or similar assets or liabilities or other inputs that are observable or can be corroborated by observable market data. • Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to determining the fair value of the assets or liabilities, including pricing models, discounted cash flow methodologies and similar techniques. The Company’s cash equivalents and available-for-sale securities are carried at fair value, determined according to the fair value hierarchy described above. Derivative liabilities are recorded at fair value based on the probability weighted present value of the estimated cash flows pursuant to the contractual terms of each agreement. The derivative liabilities are remeasured quarterly with changes in fair value recorded in change in fair value of derivative liabilities in the consolidated statements of operations. See Note 4, Fair Value of Financial Assets and Liabilities, for additional information. The carrying values of the Company’s accounts payable and accrued expenses and other current liabilities approximate their fair value due to the short-term nature of these liabilities.
Leases	Leases At the inception of a contract, the Company determines if a contract meets the definition of a lease. A lease is a contract, or part of a contract, that conveys the right to control the use of identified property, plant, or equipment (an identified asset) for a period of time in exchange for consideration. The Company determines if the contract conveys the right to control the use of an identified asset for a period of time. The Company assesses throughout the period of use whether the Company has both of the following: (1) the right to obtain substantially all of the economic benefits from use of the identified asset and (2) the right to direct the use of the identified asset. This determination is reassessed if the terms of the contract are changed. Leases are classified as operating or finance leases based on the terms of the lease agreement and certain characteristics of the identified asset. Right-of-use assets and lease liabilities are recognized at the lease commencement date based on the present value of the minimum future lease payments. Adjustments to the right-of-use asset may be required for items such as lease prepayments or incentives received. The Company’s policy is to not record leases with an original term of twelve months or less on the consolidated balance sheets. The Company recognizes lease expense for these short-term leases on a straight-line basis over the lease term. Certain lease agreements include rental payments that are adjusted periodically for inflation or other variables. In addition to rent, the leases may require the Company to pay additional amounts for taxes, insurance, maintenance and other expenses, which are generally referred to as non-lease components. Such adjustments to rental payments and variable non-lease components are treated as variable lease payments and recognized in the period in which the obligation for these payments was incurred. Variable lease components and variable non-lease components are not measured as part of the right-of-use asset and liability. Only when lease components and their associated non-lease components are fixed are they accounted for as a single lease component and recognized as part of a right-of-use asset and liability. Total contract consideration is allocated to the combined fixed lease and non-lease components.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation. Depreciation expense is recognized using the straight-line method over the useful life of the asset. Laboratory equipment is depreciated over five years. Computer equipment is depreciated over three years. Computer software is depreciated over two years. Furniture and office equipment are depreciated over five years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful life of the related asset. Expenditures for repairs and maintenance of assets are charged to expense as incurred. Upon retirement or sale, the net book value is written off and any resulting gain or loss is included in the consolidated statements of operations. Equipment under a finance lease is stated at fair value at the inception of the lease less accumulated depreciation and is depreciated over the remaining lease term or the estimated useful life of the equipment.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets, comprised of property and equipment, to be held and used are tested for recoverability whenever events or changes in business circumstances indicate that the carrying amount of the assets may not be fully recoverable. Factors that the Company considers in deciding when to perform an impairment review include significant underperformance of the business in relation to expectations, significant negative industry or economic trends and significant changes or planned changes in the use of the assets. If an impairment review is performed to evaluate a long-lived asset for recoverability, the Company compares forecasts of undiscounted cash flows expected to result from the use and eventual disposition of the long-lived asset to its carrying value. An impairment loss would be recognized when estimated undiscounted future cash flows expected to result from the use of an asset are less than its carrying amount. The impairment loss would be based on the excess of the carrying value of the impaired asset over its fair value, determined based on discounted cash flows.
Exclusive Licenses	Exclusive Licenses If a license granted in an arrangement is determined to be distinct from the other promises or performance obligations identified in the arrangement, which generally include research and development services, the Company recognizes revenue from non-refundable, upfront fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license In assessing whether a license is distinct from the other promises, the Company considers relevant facts and circumstances of each arrangement, including the research and development capabilities of the collaboration partner and the availability of the associated expertise in the general marketplace. In addition, the Company considers whether the collaboration partner can benefit from the license for its intended purpose without the receipt of the remaining promise, whether the value of the license is dependent on the unsatisfied promise, whether there are other vendors that could provide the remaining promise, and whether it is separately identifiable from the remaining promise. For licenses that are combined with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue. The Company evaluates the measure of progress each reporting period and, if necessary, adjusts the measure of performance and related revenue recognition. The measure of progress, and thereby periods over which revenue should be recognized, are subject to estimates by management and may change over the course of the arrangement. Research and Development Services The promises under the Company’s collaboration and license agreements generally include research and development services to be performed by the Company on behalf of the collaboration partner. For performance obligations that include research and development services, the Company generally recognizes revenue allocated to such performance obligations based on an appropriate measure of progress. The Company utilizes judgment to determine the appropriate method of measuring progress for purposes of recognizing revenue, which is generally an input measure, such as costs incurred. Milestone Payments At the inception of each arrangement that includes milestone payments based on certain events, the Company evaluates whether the milestones are considered probable of being achieved and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company, such as regulatory approvals, are not considered probable of being achieved until those approvals are received or the specified event occurs. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to achieve the particular milestone in making this assessment. There is considerable judgment involved in determining whether it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. At the end of each subsequent reporting period, the Company reevaluates the probability of achievement of all milestones subject to constraint and, if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect revenues and earnings in the period of adjustment. If a milestone or other variable consideration relates specifically to the Company’s efforts to satisfy a single performance obligation or to a specific outcome from satisfying the performance obligation, the Company generally allocates the milestone amount entirely to that performance obligation once it is probable that a significant reversal in the amount of cumulative revenue recognized would not occur. Royalties For arrangements that include sales-based royalties, including milestone payments based on a level of sales, and the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). To date, the Company has not recognized any royalty revenue resulting from any of its licensing arrangements. Collaboration Revenue The Company analyzes its collaboration arrangements to assess whether they are within the scope of ASC 808, Collaborative Arrangements (“ASC 808”) to determine whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities. This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For collaboration arrangements within the scope of ASC 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of ASC 808 and those that are more reflective of a vendor-customer relationship and therefore within the scope of ASC 606, Revenue from Contracts with Customers (“ASC 606”). For elements of collaboration arrangements that are accounted for pursuant to ASC 808, an appropriate recognition method is determined and applied consistently, generally by analogy to ASC 606. Costs Associated with License and Collaborative Arrangements All costs associated with license and collaborative arrangements are expensed as incurred and recorded in research and development expense in the consolidated statements of operations.
Research and Development Costs	Research and Development Costs Research and development costs are expensed as incurred. Research and development expenses include salaries, equity-based compensation and benefits of employees, third-party license fees and other operational costs related to the Company’s research and development activities, including allocated facility-related expenses and external costs of outside vendors engaged to conduct both preclinical studies and clinical trials. Non-refundable pre-payments for goods or services that will be used or rendered for future research and development activities are deferred and capitalized. Such amounts are recognized as expense as the goods or services are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered or the services rendered. The Company may in-license the rights to develop and commercialize product candidates. For each in-license transaction the Company evaluates whether it has acquired processes or activities along with inputs that would be sufficient to constitute a “business” as defined under GAAP. A “business” as defined under GAAP consists of inputs and processes applied to those inputs that have the ability to create outputs. Although businesses usually have outputs, outputs are not required for an integrated set of activities to qualify as a business. When the Company determines that it has not acquired sufficient processes or activities to constitute a business, any upfront payments, as well as milestone payments, are immediately expensed as acquired research and development in the period in which they are incurred.
Research Contract Costs and Accruals	Research Contract Costs and Accruals The Company has entered into various research and development contracts with research institutions and other companies. These agreements are generally cancelable, and related payments are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research costs. When evaluating the adequacy of the accrued liabilities, the Company analyzes progress of the studies, including the phase or completion of events, invoices received and contracted costs. Estimates based on available information are made in determining the accrual balances at the end of any reporting period. Actual results could differ from the Company's estimates; however, the Company's historical accrual estimates have not been materially different from the actual costs.
Patent Costs	Patent Costs All patent-related costs incurred for filing and prosecuting patent applications are expensed as incurred due to the uncertainty about the recovery of the expenditure. Amounts incurred are classified as general and administrative expenses.
Equity-Based Compensation	Equity-Based Compensation The Company measures all stock options and other stock-based awards granted to employees, directors and non-employees based on the fair value on the date of the grant and recognizes compensation expense of those awards, over the requisite service period, which is generally the vesting period of the respective award. Forfeitures are accounted for as they occur. The Company applies the straight-line method of expense recognition to all awards with only service-based vesting conditions. The fair value of each stock option grant is estimated on the date of grant using the Black-Scholes option-pricing model. In the first quarter of 2024, the Company determined that it has adequate historical stock price data to utilize solely its own stock for historical volatility purposes. The expected term of stock options with service-based vesting conditions and options granted to non-employees has been determined utilizing the “simplified” method for awards that qualify as “plain-vanilla” options. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. The Company utilized a 0% expected dividend yield in its determination of grant fair value based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future, if ever. The fair values of restricted stock units and performance-based restricted stock units are measured at the grant date based on the closing price of the Company’s common stock on the date of grant. For restricted stock units, the fair value of the award is recognized on a straight-line basis over the requisite service periods. For performance-based restricted stock unit awards, which are subject to the achievement of performance milestones, the fair value is recognized as expense over the requisite service periods when the achievement of such performance milestones is determined to be probable. If a performance milestone is not determined to be probable or is not met, no equity-based compensation expense is recognized, and any previously recognized expense is reversed. Forfeitures are recognized as a reduction of equity-based compensation expense as they occur. The Company classifies stock-based compensation expense in its consolidated statements of operations in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified. The Company does not currently hold any treasury shares. Upon the exercise of stock options and the vesting of restricted stock units and performance stock units, the Company issues new shares of common stock and delivers them to the participant.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. The Company records valuation allowances to reduce deferred income tax assets to the amount that is more likely than not to be realized. The Company determines whether it is more likely than not that a tax position will be sustained upon examination. If it is not more likely than not that a position will be sustained, no amount of benefit attributable to the position is recognized. The tax benefit to be recognized of any tax position that meets the more likely than not recognition threshold is calculated as the largest amount that is more than 50% likely of being realized upon resolution of the contingency. Prior to January 25, 2018, the Company had not been subject to U.S. federal income taxes as the Company was organized as a limited liability company. As such, the taxable income or loss was passed through to and included in the tax returns of the members. Since January 25, 2018, the Company’s income has since been subject to U.S. federal, state, local, and foreign income taxes and taxed at the prevailing corporate tax rates.
Segment Data	Segment Data The Company manages its operations as a single segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on developing treatments through gene therapy and other means for patients with neuromuscular and cardiac diseases. All of the Company’s tangible assets are held in the United States. Please refer to Note 17, Segment Reporting for further information.
Comprehensive Loss	Comprehensive Loss Comprehensive loss includes net loss, as well as other changes in stockholders’ equity that result from transactions and economic events other than those with members. The Company’s only element of other comprehensive income in all periods presented was unrealized gains from available-for-sale securities.
Net Loss per Share	Net Loss per Share The Company follows the two-class method when computing net loss per share, as the Company has issued shares that meet the definition of participating securities. The two-class method determines net loss per share for each class of common and participating securities according to dividends declared or accumulated and participation rights in undistributed earnings. The two-class method requires income available to common stockholders for the period to be allocated between common and participating securities based upon their respective rights to receive dividends as if all income for the period had been distributed. Basic net loss per share is computed by dividing the net loss by the weighted average number of shares of common stock and pre-funded warrants outstanding for the period. Diluted net loss is computed by adjusting net loss to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net loss per share is computed by dividing the diluted net loss by the weighted average number of shares of common stock and pre-funded warrants outstanding for the period, including potential dilutive shares of common stock assuming the dilutive effect of common stock equivalents. Any preferred stock that the Company may issue in the future could entitle the holders of such shares to participate in dividends and not require the holders of such shares to participate in losses of the Company. Accordingly, in periods in which the Company reports a net loss, such losses are not allocated to such participating securities. In periods in which the Company reports a net loss, diluted net loss per share is the same as basic net loss per share, since dilutive shares of common stock are not assumed to have been issued if their effect is anti-dilutive. As of December 31, 2024 and 2023, there was no preferred stock issued or outstanding with any contractual rights.
Contingencies	Contingencies Loss contingency provisions are recorded if the potential loss from any claim, asserted or unasserted, or legal proceeding, is considered probable and the amount can be reasonably estimated, or a range of loss can be determined. These accruals represent the Company’s best estimate of probable loss. Disclosure also is provided when it is reasonably possible that a loss will be incurred or when it is reasonably possible that the amount of a loss will exceed the recorded provision. The Company reviews the status of each significant matter and assesses its potential financial exposure. Significant judgment is required in both the determination of probability and the determination as to whether an exposure is reasonably estimable. Because of uncertainties related to these matters, accruals are based only on the best information available at the time. As additional information becomes available, the Company reassesses the potential liability related to pending claims and may change its estimates. These changes in the estimates of the potential liabilities could have a material impact on the Company’s consolidated results of operations and financial position.
Business Combinations	Business Combinations The Company's consolidated financial statements include the operations of acquired businesses after the completion of the acquisitions. The Company accounts for acquired businesses using the acquisition method of accounting. Application of this method of accounting requires that (i) identifiable assets acquired (including identifiable intangible assets) and liabilities assumed be measured and recognized at fair value as of the acquisition date, and (ii) the excess of the purchase price over the net fair value of identifiable assets acquired and liabilities assumed be recorded as goodwill. Acquired in-process research and development (“IPR&D”) is recognized at fair value and initially characterized as an indefinite-lived intangible asset, irrespective of whether the acquired IPR&D has an alternative future use. Transaction costs are expensed as incurred. Amounts assigned to goodwill and other identifiable intangible assets are based on independent appraisals or internal estimates.
Asset Acquisitions	Asset Acquisitions Acquisitions of assets or a group of assets that do not meet the definition of a business are accounted for as asset acquisitions using the cost accumulation method, whereby the cost of the acquisition, including certain transaction costs, is allocated to the assets acquired on the basis of relative fair values. No goodwill is recognized in an asset acquisition. Intangible assets that are acquired in an asset acquisition for use in research and development activities which have an alternative future use are capitalized as IPR&D. Acquired IPR&D which has no alternative future use is recognized as research and development expense at acquisition. Contingent milestone payments associated with asset acquisitions are recognized when probable and estimable. These amounts are expensed to research and development if there is no alternative future use associated with the asset or capitalized as an intangible asset if an alternative future use of the asset exists.
Recently Issued Accounting Pronouncements	Recently Issued Accounting Pronouncements In December 2023, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("ASU") No. 2023-09, “Income Taxes (Topic 740): Improvements to Income Tax Disclosures.” This ASU updates income tax disclosure requirements primarily by requiring specific categories and greater disaggregation within the rate reconciliation and disaggregation of income taxes paid by jurisdiction. This ASU is effective for annual periods beginning after December 15, 2024 and is applicable to the Company’s fiscal year beginning January 1, 2025, with early application permitted. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and disclosures. In November 2024, the FASB issued ASU No. 2024-03, "Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Sub-Topic 220-40): Disaggregation of Income Statement Expenses," which requires additional disclosure of the nature of expenses included in the income statement. The standard requires disclosures about specific types of expenses included in the expense captions presented in the income statement. This ASU is effective for fiscal years beginning after December 15, 2026, and interim periods beginning after December 15, 2027, with early adoption permitted. The requirements should be applied on a prospective basis while retrospective application is permitted. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and disclosures.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements On November 27, 2023, the FASB issued ASU No. 2023-07, "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures." Among other new disclosure requirements, ASU 2023-07 requires companies to disclose significant segment expenses that are regularly provided to the chief operating decision maker. We adopted the standard effective December 31, 2024 and applied the disclosure requirements retrospectively to all prior periods presented in the financial statements. Adoption of ASU 2023-07 did not have an impact on the Company’s consolidated financial position, results of operations, or cash flows.

Restructuring- Additional Information (Detail) - November 2022 Plan [Member] - USD ($) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Nov. 30, 2022	Dec. 31, 2022	Dec. 31, 2024
Restructuring Cost and Reserve [Line Items]
Number of headcount reduced, percentage	18.00%
Restructuring charges related to severance payment and other employee-related costs		$ 5.7
Restructuring charges paid			$ 0.3

- 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

Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 80,235	$ 74,015
Restricted cash, non-current	1,952	1,833
Total cash and cash equivalents, and restricted cash, as reported in the condensed consolidated statements of cash flows	$ 82,187	$ 75,848	$ 157,217

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Operating expenses:
Research and development	$ 96,431	$ 76,563
General and administrative	33,297	27,752
Restructuring expense		(63)
Total operating expenses	129,728	104,252
Loss from operations	(129,728)	(104,252)
Other income, net:
Interest income	9,469	7,582
Interest expense	(340)	(440)
Change in fair value of derivative liabilities	(4,750)
Other income, net	652	1,095
Total other income, net	5,031	8,237
Net loss	$ (124,697)	$ (96,015)
Net loss per share, basic	$ (3.06)	$ (4.83)
Net loss per share, diluted	$ (3.06)	$ (4.83)
Weighted average shares of common stock outstanding used to compute basic net loss per share	40,816,694	19,884,007
Weighted average shares of common stock outstanding, used to compute diluted net loss per share	40,816,694	19,884,007

Net Loss per Share (Tables)

12 Months Ended

Dec. 31, 2024

Earnings Per Share [Abstract]

Schedule of Computation of Basic and Diluted Net Loss per Share

The following table sets forth the computation of the Company's basic and diluted net loss per share:


	Year Ended December 31,
	2024			2023
Numerator:
Net loss	$	(124,697	)	$	(96,015	)
Denominator:
Shares used to compute net loss per share, basic and diluted
Weighted average shares of common stock outstanding		38,178,327			19,884,007
Weighted average pre-funded warrants to purchase shares of common stock		2,638,367			—
Weighted average shares of common stock used to compute basic and diluted net loss per share		40,816,694			19,884,007
Net loss per share, basic and diluted	$	(3.06	)	$	(4.83	)

Schedule of Antidilutive Securities Excluded from Calculation of Net Loss per Share


	Year Ended December 31,
	2024		2023
Options to purchase common stock		2,927,937		2,259,672
Nonvested restricted stock units		1,480,272		877,181
Nonvested performance stock units		2,165,325		—
Shares subject to employee stock purchase plan		281,640		—
Warrants		9,230		—
Total		6,864,404		3,136,853

Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2024

Share-Based Payment Arrangement [Abstract]

Schedule of Equity-based Compensation Expense

The Company has classified equity-based compensation in its consolidated statements of operations as follows:


	Year Ended December 31,
	2024		2023
Research and development expenses	$	3,537	$	3,094
General and administrative expenses		6,982		4,531
Total	$	10,519	$	7,625

Summary of Stock Option Activity

The table below summarizes the activity with respect to stock options for the year ended December 31, 2024:


	Number of Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at January 1, 2024		2,259,672		$	21.93			$	863
Granted		1,219,522			7.81
Exercised		(71,562	)		6.39
Expired		(44,521	)		31.11
Forfeitures		(435,174	)		8.93
Outstanding at December 31, 2024		2,927,937		$	18.22		8.01	$	193
Vested and expected to vest as of December 31, 2024		2,927,937		$	18.22		8.01	$	193
Exercisable at December 31, 2024		1,117,768		$	35.27		6.79	$	541

Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted

The assumptions used in the Black-Scholes option-pricing model for all stock options granted during each period presented are as follows:


	Year Ended December 31,
	2024	2023
Common stock price	$5.76-$8.64	$2.15-$7.33
Expected volatility	119.7% - 128.7%	121.8% - 129.60%
Expected dividends	0.0%	0.0%
Expected term (in years)	5.31 - 6.25	5.31 - 6.25
Risk-free rate	3.7% - 4.4%	3.5% - 4.9%

Summary of Restricted Stock Unit Activity

The following table summarizes activity with respect to RSUs during the year ended December 31, 2024:


	Units			Weighted- Average Grant Date Fair Value
Nonvested RSUs at January 1, 2024		877,181		$	6.37
Granted		1,196,954		$	7.94
Vested		(335,981	)	$	6.55
Forfeitures		(257,882	)	$	6.91
Nonvested RSUs at December 31, 2024		1,480,272		$	7.50

Fair Value of Financial Assets and Liabilities - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Fair Value Disclosures [Abstract]
Fair value, assets, transfers into level 3, amount	$ 0	$ 0
Fair value, assets, transfers out of level 3, amount	0	0
Fair value, assets, transfers into level 2, amount	0	0
Fair value, assets, transfers out of level 2, amount	0	0
Fair value, assets, transfers into level 1, amount	0	0
Fair value, assets, transfers out of level 1, amount	$ 0	$ 0

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2024

Property, Plant and Equipment [Abstract]

Summary of Property and Equipment

Property and equipment consisted of the following:


	December 31,
	2024			2023
Furniture and fixtures	$	936		$	936
Laboratory equipment		14,404			16,137
Leasehold improvements		470			481
Computer equipment		764			842
Computer software		320			553
Construction in process		879			410
		17,773			19,359
Less accumulated depreciation		(13,026	)		(12,735	)
Total	$	4,747		$	6,624

Income Taxes - Schedule of Deferred Income Tax Asset Valuation Allowance (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Income Tax Disclosure [Abstract]
Valuation allowance at beginning of year	$ 91,705	$ 163,566
Increases (decreases) recorded to income tax provision	38,985	(71,861)
Valuation allowance at end of year	$ 130,690	$ 91,705

Accrued Expenses and Other Current Liabilities (Tables)

12 Months Ended

Dec. 31, 2023

Payables and Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consisted of the following:


	December 31,
	2024		2023
Accrued research and development expense	$	7,268	$	2,614
Accrued compensation		6,221		5,948
Accrued milestone payment (Note 3)		5,000		—
Accrued other and other current liabilities		1,363		1,599
Total	$	19,852	$	10,161

Available-for-Sale Securities - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities weighted average contractual maturity period	6 months	4 months 24 days