0000950170-24-122247 | 10-Q | XBRL Viewer

Available-for-Sale Securities

9 Months Ended

Sep. 30, 2024

Investments, Debt and Equity Securities [Abstract]

5. Available-for-Sale Securities

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


	September 30, 2024
Description	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Treasury bills maturing in one year or less	$	63,580	$	55	$	—	$	63,635
Government bonds maturing in one year or less		43,028		60		—	$	43,088
Total available-for-sale securities	$	106,608	$	115	$	—	$	106,723


	December 31, 2023
Description	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 September 30, 2024 and December 31, 2023, respectively.

Available-for-Sale Securities (Tables)

9 Months Ended

Sep. 30, 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:


	September 30, 2024
Description	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Fair Value
Treasury bills maturing in one year or less	$	63,580	$	55	$	—	$	63,635
Government bonds maturing in one year or less		43,028		60		—	$	43,088
Total available-for-sale securities	$	106,608	$	115	$	—	$	106,723


	December 31, 2023
Description	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).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-9

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 5: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 6: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (aaa)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-2

Reference 9: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 10: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 11: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

Reference 12: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481800/320-10-50-3

+ Details

Condensed 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
Vesting of restricted stock, units			16,400
Unrealized gain (loss) on available-for-sale securities	73						73
Equity-based compensation	2,118				2,118
Net loss	(30,070)							(30,070)
Ending balance at Mar. 31, 2023	183,787		$ 20		776,570		5	(592,808)
Ending balance, units at Mar. 31, 2023			19,573,132
Beginning balance at Dec. 31, 2022	211,666		$ 20		774,452		(68)	(562,738)
Beginning balance, units at Dec. 31, 2022			19,556,732
Unrealized gain (loss) on available-for-sale securities	70
Net loss	(75,679)
Ending balance at Sep. 30, 2023	144,361		$ 20		782,756		2	(638,417)
Ending balance, units at Sep. 30, 2023			20,061,751
Beginning balance at Mar. 31, 2023	183,787		$ 20		776,570		5	(592,808)
Beginning balance, units at Mar. 31, 2023			19,573,132
Issuance of common stock, net of issuance costs	2,539				2,539
Issuance of common stock, net of issuance costs, units			420,000
Vesting of restricted stock, units			36,321
Issuance of common stock under employee stock purchase plan	78				78
Issuance of common stock under employee stock purchase plan, units			14,936
Unrealized gain (loss) on available-for-sale securities	9						9
Equity-based compensation	1,944				1,944
Net loss	(24,629)							(24,629)
Ending balance at Jun. 30, 2023	163,728		$ 20		781,131		14	(617,437)
Ending balance, units at Jun. 30, 2023			20,044,389
Vesting of restricted stock, units			17,362
Unrealized gain (loss) on available-for-sale securities	(12)						(12)
Equity-based compensation	1,625				1,625
Net loss	(20,980)							(20,980)
Ending balance at Sep. 30, 2023	144,361		$ 20		782,756		2	(638,417)
Ending balance, units at Sep. 30, 2023			20,061,751
Beginning balance at Dec. 31, 2023	126,481		$ 20		785,199		15	(658,753)
Beginning balance, units at Dec. 31, 2023			20,386,606
Issuance of common stock, net of issuance costs	3,056	$ 89,454	$ 1	$ 17	3,055	$ 89,437
Issuance of common stock, net of issuance costs, units			350,664	16,973,103
Issuance of pre-funded warrants in private placement	14,293				14,293
Vesting of restricted stock, units			98,677
Exercises of common stock options	151				151
Exercises of common stock options, units			24,639
Unrealized gain (loss) on available-for-sale securities	(19)						(19)
Equity-based compensation	1,611				1,611
Net loss	(24,303)							(24,303)
Ending balance at Mar. 31, 2024	210,724		$ 38		893,746		(4)	(683,056)
Ending balance, units at Mar. 31, 2024			37,833,689
Beginning balance at Dec. 31, 2023	$ 126,481		$ 20		785,199		15	(658,753)
Beginning balance, units at Dec. 31, 2023			20,386,606
Exercises of common stock options, units	67,942
Unrealized gain (loss) on available-for-sale securities	$ 101
Net loss	(82,100)
Ending balance at Sep. 30, 2024	167,022		$ 39		907,720		116	(740,853)
Ending balance, units at Sep. 30, 2024			38,930,203
Beginning balance at Mar. 31, 2024	210,724		$ 38		893,746		(4)	(683,056)
Beginning balance, units at Mar. 31, 2024			37,833,689
Issuance of common stock, net of issuance costs	5,357		$ 1		5,356
Issuance of common stock, net of issuance costs, units			526,953
Vesting of restricted stock, units			131,859
Exercises of common stock options	10				10
Exercises of common stock options, units			1,703
Issuance of common stock under employee stock purchase plan	145				145
Issuance of common stock under employee stock purchase plan, units			56,855
Unrealized gain (loss) on available-for-sale securities	(11)						(11)
Equity-based compensation	2,092				2,092
Net loss	(25,072)							(25,072)
Ending balance at Jun. 30, 2024	193,245		$ 39		901,349		(15)	(708,128)
Ending balance, units at Jun. 30, 2024			38,551,059
Issuance of common stock, net of issuance costs	3,099				3,099
Issuance of common stock, net of issuance costs, units			330,670
Vesting of restricted stock, units			6,874
Exercises of common stock options	277				277
Exercises of common stock options, units			41,600
Unrealized gain (loss) on available-for-sale securities	131						131
Equity-based compensation	2,995				2,995
Net loss	(32,725)							(32,725)
Ending balance at Sep. 30, 2024	$ 167,022		$ 39		$ 907,720		$ 116	$ (740,853)
Ending balance, units at Sep. 30, 2024			38,930,203

Net Loss per Share

9 Months Ended

Sep. 30, 2024

Earnings Per Share [Abstract]

Net Loss per Share

11. Net Loss per Share

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


	Three Months Ended September 30,						Nine Months Ended September 30,
	2024			2023			2024			2023
Numerator:
Net loss	$	(32,725	)	$	(20,980	)	$	(82,100	)	$	(75,679	)
Denominator:
Shares used to compute net loss per share, basic and diluted
Weighted average shares of common stock outstanding		38,730,839			20,059,641			37,568,821			19,767,174
Weighted average shares of pre-funded warrants to purchase common stock		2,712,478			—			2,613,482			—
Weighted average shares of common stock outstanding used to compute basic and diluted net loss per share		41,443,317			20,059,641			40,182,303			19,767,174
Net loss per share, basic and diluted	$	(0.79	)	$	(1.05	)	$	(2.04	)	$	(3.83	)

Included within weighted average shares of common stock outstanding for the three and nine months ended September 30, 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 three and nine months ended September 30, 2023.

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.


	Three and Nine Months Ended September 30,
	2024		2023
Options to purchase common stock		2,941,043		2,189,102
Nonvested restricted stock units		1,519,192		946,182
Nonvested performance stock units		2,165,325		—
Shares subject to employee stock purchase plan		244,302		—
Warrants		9,230		—
Total		6,879,092		3,135,284

Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liabilities at fair value	$ 3,400,000	$ 3,400,000
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
Fair value, liabilities, transfers into level 3, amount		0	0
Fair value, liabilities, transfers out of level 3, amount		0	0
Fair value, liabilities, transfers into level 2, amount		0	0
Fair value, liabilities, transfers out of level 2, amount		0	0
Fair value, liabilities, transfers into level 1, amount		0	0
Fair value, liabilities, transfers out of level 1, amount		0	$ 0
Level 3 [Member]
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Derivative liabilities at fair value	3,400,000	3,400,000
Gain or loss recorded for a change in fair value	$ 0	$ 0

Equity-Based Compensation

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

Equity-Based Compensation

8. Equity-Based Compensation

Equity-based compensation expense

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


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development	$	934	$	677	$	2,314	$	2,285
General and administrative		2,061		948		4,384		3,402
Total	$	2,995	$	1,625	$	6,698	$	5,687

Equity incentive plans

As of September 30, 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 2021 Employee Stock Purchase Plan; 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 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 September 30, 2024, there were 2,007,144 stock options outstanding, 1,007,794 RSUs outstanding, 2,165,325 performance stock units outstanding, and 171,622 shares remained available for future issuance under the 2020 Plan.

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 September 30, 2024, there were 100,000 stock options outstanding, 227,141 RSUs outstanding, and 672,859 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 nine months ended September 30, 2024:


	Number of Options			Weighted Average Exercise Price		Remaining Contractual Life (in years)
Outstanding at January 1, 2024		2,259,672		$	21.93
Granted		1,219,522		$	7.81
Exercised		(67,942	)	$	6.44
Expired		(41,659	)	$	24.77
Forfeitures		(428,550	)	$	8.95
Outstanding at September 30, 2024		2,941,043		$	18.29		8.26
Vested and expected to vest as of September 30, 2024		2,941,043		$	18.29		8.26
Exercisable at September 30, 2024		1,029,832		$	38.16		6.88

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


	Three Months Ended September 30,		Nine Months Ended September 30,
	2024	2023	2024	2023
Common stock price	$8.64	$3.62-$4.13	$5.76-$8.64	$3.62-$7.33
Expected volatility	119.7%	121.8%-121.9%	119.7%-128.7%	121.8%-129.6%
Expected dividends	0.0%	0.0%	0.0%	0.0%
Expected term (in years)	6.08	6.25	5.31-6.25	5.31-6.25
Risk-free rate	3.7%	4.2%-4.3%	3.7%-4.4%	3.5%-4.3%

The weighted average grant date fair values of stock options granted during the three months ended September 30, 2024 and 2023 were $7.56 and $3.28, and the weighted average grant date fair values of stock options granted during the nine months ended September 30, 2024 and 2023 were $6.96 and $5.04, respectively.

The Company recognized $1.6 million and $0.9 million of equity-based compensation expense in connection with stock options during the three months ended September 30, 2024 and 2023, respectively. During the nine months ended September 30, 2024 and 2023, the Company recognized equity-based compensation expense in connection with stock options of $3.6 million and $4.0 million, respectively. As of September 30, 2024, there was $10.5 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 2.56 years.

Restricted stock units

The following table summarizes activity with respect to RSUs during the nine months ended September 30, 2024:


	Units			Weighted- Average Grant Date Fair Value
Nonvested RSUs at January 1, 2024		877,181		$	6.37
Granted		1,124,028		$	8.03
Vested		(237,315	)	$	6.69
Forfeitures		(244,607	)	$	6.88
Nonvested RSUs at September 30, 2024		1,519,287		$	7.47

The Company recognized $0.8 million and $0.7 million of equity-based compensation expense in connection with RSUs during the three months ended September 30, 2024 and 2023, respectively. During the nine months ended September 30, 2024 and 2023, the Company recognized equity-based compensation expense in connection with RSUs of $2.2 million and $1.6 million, respectively. As of September 30, 2024, there was $9.4 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 3.08 years.

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 nine months ended September 30, 2024 with a weighted average grant date fair value of $7.51 per unit. There were no PSUs granted during the three months ended September 30, 2024. During the three and nine months ended September 30, 2024, the Company recognized $0.6 million and $0.7 million in expense for these grants, respectively.

As of September 30, 2024, there was $3.3 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 2.13 years.

Equity Based Compensation - Summary Of Stock Option Activity (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award, Options, Outstanding [Roll Forward]
Outstanding at January 1, 2024	2,259,672
Granted	1,219,522
Exercised	(67,942)
Expired	(41,659)
Forfeitures	(428,550)
Outstanding at September 30, 2024	2,941,043
Vested and expected to vest as of September 30, 2024	2,941,043
Exercisable at September 30, 2024	1,029,832
Weighted Average Exercise Price
Outstanding at January 1, 2024	$ 21.93
Granted	7.81
Exercised	6.44
Expired	24.77
Forfeitures	8.95
Outstanding at September 30, 2024	18.29
Vested and expected to vest as of September 30, 2024	18.29
Exercisable at September 30, 2024	$ 38.16
Remaining Contractual Life (in years)
Outstanding	8 years 3 months 3 days
Vested and expected to vest as of September 30, 2024	8 years 3 months 3 days
Exercisable at September 30, 2024	6 years 10 months 17 days

Fair Value Measurements

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Fair Value Measurements

4. Fair Value Measurements

Fair value is an exit price, representing the amount that would be received from the sale of an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. Valuation techniques used to measure fair value are performed in a manner to maximize the use of observable inputs and minimize the use of unobservable inputs. As a basis for considering such assumptions, the accounting literature establishes a three-tier value hierarchy which prioritizes the inputs used in measuring fair value as follows:

•

Level 1—Observable inputs, such as 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 following tables present information about the Company’s financial assets and liabilities that are measured at fair value on a recurring basis:


	September 30, 2024
	Level 1		Level 2		Level 3		Total
Financial assets
Cash equivalents:
Money market funds	$	—	$	19,622	$	—	$	19,622
Treasury bills		—		4,991		—		4,991
Government bonds		—		1,298		—		1,298
Total cash equivalents		—		25,911		—		25,911
Available-for-sale securities (Note 5):
Treasury bills		—		63,635		—		63,635
Government bonds		—		43,088		—		43,088
Total available-for-sale securities		—		106,723		—		106,723
Total financial assets	$	—	$	132,634	$	—	$	132,634

Financial liabilities
Derivative liabilities	$	—	$	—	$	3,400	$	3,400
Total financial liabilities	$	—	$	—	$	3,400	$	3,400


	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 September 30, 2024 and December 31, 2023, the fair values of the Company’s cash equivalents and available-for-sale securities were determined using Level 2 inputs.

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 are as follows:


Derivative Liabilities	Fair Values at September 30, 2024	Valuation Technique	Unobservable Input	Range	Average
Development Milestones	$3,400	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

As of the acquisition date, see Note 2 - FA212 Asset Acquisition, the derivative liabilities were recorded at a fair value of $3.4 million and there has been no gain or loss recorded for a change in fair value for the three and nine months ended September 30, 2024.

As of September 30, 2024, the fair values of the Company’s derivative liabilities were determined using Level 3 inputs. During the nine months ended September 30, 2024 and the year ended December 31, 2023, there were no transfers between Level 1, Level 2, and Level 3.

As of September 30, 2024 and December 31, 2023, 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.

FA212 Asset Acquisition - Additional Information (Detail) - USD ($)	Sep. 19, 2024	Sep. 30, 2024
Asset Acquisition [Line Items]
Derivative liabilities at fair value		$ 3,400,000
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
Aggregate acquisition cost	5,100,000
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

Equity-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2024

Share-Based Payment Arrangement [Abstract]

Summary of Stock Option Activity

The table below summarizes the activity with respect to stock options for the nine months ended September 30, 2024:


	Number of Options			Weighted Average Exercise Price		Remaining Contractual Life (in years)
Outstanding at January 1, 2024		2,259,672		$	21.93
Granted		1,219,522		$	7.81
Exercised		(67,942	)	$	6.44
Expired		(41,659	)	$	24.77
Forfeitures		(428,550	)	$	8.95
Outstanding at September 30, 2024		2,941,043		$	18.29		8.26
Vested and expected to vest as of September 30, 2024		2,941,043		$	18.29		8.26
Exercisable at September 30, 2024		1,029,832		$	38.16		6.88

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:


	Three Months Ended September 30,		Nine Months Ended September 30,
	2024	2023	2024	2023
Common stock price	$8.64	$3.62-$4.13	$5.76-$8.64	$3.62-$7.33
Expected volatility	119.7%	121.8%-121.9%	119.7%-128.7%	121.8%-129.6%
Expected dividends	0.0%	0.0%	0.0%	0.0%
Expected term (in years)	6.08	6.25	5.31-6.25	5.31-6.25
Risk-free rate	3.7%	4.2%-4.3%	3.7%-4.4%	3.5%-4.3%

Schedule of Equity-based Compensation Expense

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


	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development	$	934	$	677	$	2,314	$	2,285
General and administrative		2,061		948		4,384		3,402
Total	$	2,995	$	1,625	$	6,698	$	5,687

Summary of Restricted Stock Unit Activity

The following table summarizes activity with respect to RSUs during the nine months ended September 30, 2024:


	Units			Weighted- Average Grant Date Fair Value
Nonvested RSUs at January 1, 2024		877,181		$	6.37
Granted		1,124,028		$	8.03
Vested		(237,315	)	$	6.69
Forfeitures		(244,607	)	$	6.88
Nonvested RSUs at September 30, 2024		1,519,287		$	7.47

Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Dec. 31, 2022
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 64,394	$ 74,015	$ 49,037
Restricted cash, non-current	1,931	1,833	1,833
Total cash and cash equivalents, and restricted cash, as reported in the condensed consolidated statements of cash flows	$ 66,325	$ 75,848	$ 50,870	$ 157,217

Leases - Additional Information (Detail) $ in Millions	3 Months Ended		9 Months Ended
Leases - Additional Information (Detail) $ in Millions	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	May 10, 2024 ft²	Dec. 22, 2022 ft²
Commitment And Contingencies [Line Items]
Sublease income \| $	$ 0.2	$ 0.3	$ 0.8	$ 0.8
Arkea Bio Corp [Member]
Commitment And Contingencies [Line Items]
Area of subleased agreement					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 subleased agreement						49,869

Available-for-Sale Securities - Schedule of Available-for-Sale Securities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 106,608	$ 49,610
Gross Unrealized Gain	115	15
Fair Value	106,723	49,625
Treasury Bills Maturing in One Year or Less [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	63,580	49,610
Gross Unrealized Gain	55	15
Fair Value	63,635	$ 49,625
Government Bonds Maturing in One Year or Less [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	43,028
Gross Unrealized Gain	60
Fair Value	$ 43,088

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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Reference 8: http://www.xbrl.org/2009/role/commonPracticeRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 45
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479130/326-30-45-1

+ Details

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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+ Details

Equity-Based Compensation - Summary of Assumptions Used in Black-Scholes Option-Pricing Model for Stock Options Granted (Detail) - $ / shares	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock price	$ 8.64
Expected volatility	119.70%
Expected volatility, Minimum		121.80%	119.70%	121.80%
Expected volatility, Maximum		121.90%	128.70%	129.60%
Expected dividends	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	6 years 29 days	6 years 3 months
Risk-free rate	3.70%
Risk-free rate, Minimum		4.20%	3.70%	3.50%
Risk-free rate, Maximum		4.30%	4.40%	4.30%
Minimum [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Common stock price		$ 3.62	$ 5.76	$ 3.62
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		$ 4.13	$ 8.64	$ 7.33
Expected term (in years)			6 years 3 months	6 years 3 months

Net Loss per Share (Tables)

9 Months Ended

Sep. 30, 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:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2024			2023			2024			2023
Numerator:
Net loss	$	(32,725	)	$	(20,980	)	$	(82,100	)	$	(75,679	)
Denominator:
Shares used to compute net loss per share, basic and diluted
Weighted average shares of common stock outstanding		38,730,839			20,059,641			37,568,821			19,767,174
Weighted average shares of pre-funded warrants to purchase common stock		2,712,478			—			2,613,482			—
Weighted average shares of common stock outstanding used to compute basic and diluted net loss per share		41,443,317			20,059,641			40,182,303			19,767,174
Net loss per share, basic and diluted	$	(0.79	)	$	(1.05	)	$	(2.04	)	$	(3.83	)

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


	Three and Nine Months Ended September 30,
	2024		2023
Options to purchase common stock		2,941,043		2,189,102
Nonvested restricted stock units		1,519,192		946,182
Nonvested performance stock units		2,165,325		—
Shares subject to employee stock purchase plan		244,302		—
Warrants		9,230		—
Total		6,879,092		3,135,284

FA212 Asset Acquisition

9 Months Ended

Sep. 30, 2024

Asset Acquisition [Abstract]

FA212 Asset Acquisition

2. 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, 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 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 with the University of Pennsylvania, who is the IP owner.

Certain development milestone payments to FA212 are payable in either cash, equity, or a combination of both at the companies 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 Measurements, which is included in the aggregate acquisition cost below.

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 condensed consolidated statement of operations. The acquisition did not qualify as a business combination as the acquisition did not include both an input and substantive processes, including an assembled workforce, that together contribute to the ability to create outputs.

License and Research Agreements - Additional Information (Detail) - Maugeri License Agreement [Member]	Jun. 29, 2023 EUR (€)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Agreement termination notice period	60 days
Upfront license fee	€ 1,500,000
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

Net Loss per Share - Schedule of Antidilutive Securities Excluded from Calculation of Net Loss per Share (Detail) - shares	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from calculation of diluted net loss per share	6,879,092	3,135,284	6,879,092	3,135,284
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	2,941,043	2,189,102	2,941,043	2,189,102
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	1,519,192	946,182	1,519,192	946,182
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		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	244,302		244,302
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		9,230

Nature of the Business and Basis of Presentation (Policies)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
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. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions and options granted to non-employees, the expected term of the Company's stock options 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. Expected dividend yield is 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. 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 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 statement 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.
Asset acquisition	Asset acquisition Acquisitions of assets or a group of assets that do not meet the definition of a business are accounted 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 in-process research and development ("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.
Derivative liabilities	Derivative liabilities 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 other expense in the condensed consolidated statements of operations.
Recently issued accounting pronouncements	Recently issued accounting pronouncements In November 2023, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires public entities, including those with a single reportable segment to: (i) provide disclosures of significant segment expenses and other segment items if they are regularly provided to the chief operating decision maker (the CODM) and included in each reported measure of segment profit or loss; (ii) provide all annual disclosures about a reportable segment’s profit or loss and assets currently required by Accounting Standards Codification 280, Segment Reporting, in interim periods; and (iii) disclose the CODM’s title and position, as well as an explanation of how the CODM uses the reported measures and other disclosures. ASU 2023-07 does not change how a public entity identifies its operating segments, aggregates those operating segments or applies the quantitative thresholds to determine its reportable segments. ASU 2023-07 is required to be applied retrospectively and is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. We expect to include additional disclosures as a result of the implementation ASU 2023-07, however, these changes are not expected to have a material effect on our consolidated financial statements. In December 2023, the FASB issued ASU 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 2024-03, Disaggregation of Income Statement Expenses (Topic 220) requiring that public business entities disclose additional information about specific expense categories in the notes to financial statements at interim and annual reporting periods. The amendments in this ASU are effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. The requirements in this ASC may be applied either prospectively to financial statements issued for reporting periods after the effective date or retrospectively to any or all prior periods presented in the financial statements. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and disclosures.

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 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	38,930,203	20,386,606
Common stock, shares outstanding	38,930,203	20,386,606

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Operating expenses:
Research and development	$ 27,327	$ 16,702	$ 65,661	$ 61,110
General and administrative	7,855	6,412	24,171	20,940
Restructuring charges				(63)
Total operating expenses	35,182	23,114	89,832	81,987
Loss from operations	(35,182)	(23,114)	(89,832)	(81,987)
Other income, net:
Interest income	2,328	1,962	7,544	5,822
Interest expense	(82)	(106)	(265)	(339)
Other income, net	211	278	453	825
Total other income, net	2,457	2,134	7,732	6,308
Net loss	$ (32,725)	$ (20,980)	$ (82,100)	$ (75,679)
Net loss per share, basic	$ (0.79)	$ (1.05)	$ (2.04)	$ (3.83)
Net loss per share, diluted	$ (0.79)	$ (1.05)	$ (2.04)	$ (3.83)
Weighted average shares of common stock outstanding, basic	41,443,317	20,059,641	40,182,303	19,767,174
Weighted average shares of common stock outstanding, diluted	41,443,317	20,059,641	40,182,303	19,767,174

Net Loss per Share - Additional Information (Detail) - shares	3 Months Ended	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Sep. 30, 2023
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	2,712,478
Pre-Funded Warrants [Member]
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Warrants issued			0
Warrants outstanding			0

Fair Value Measurements - Summary of Financial Assets and Liabilities that are Measured at Fair Value on a Recurring Basis (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Financial assets
Total cash equivalents	$ 25,911	$ 62,398
Total available-for-sale securities	106,723	49,625
Total financial assets	132,634	112,023
Financial liabilities
Derivative liabilities	3,400
Total financial liabilities	3,400
Treasury Bills [Member]
Financial assets
Total cash equivalents	4,991
Total available-for-sale securities	63,635	49,625
Government Bonds [Member]
Financial assets
Total cash equivalents	1,298
Total available-for-sale securities	43,088
Money Market Funds [Member]
Financial assets
Total cash equivalents	19,622	62,141
Certificates of Deposit [Member]
Financial assets
Total cash equivalents		257
Level 2 [Member]
Financial assets
Total cash equivalents	25,911	62,398
Total available-for-sale securities	106,723	49,625
Total financial assets	132,634	112,023
Level 2 [Member] \| Treasury Bills [Member]
Financial assets
Total cash equivalents	4,991
Total available-for-sale securities	63,635	49,625
Level 2 [Member] \| Government Bonds [Member]
Financial assets
Total cash equivalents	1,298
Total available-for-sale securities	43,088
Level 2 [Member] \| Money Market Funds [Member]
Financial assets
Total cash equivalents	19,622	62,141
Level 2 [Member] \| Certificates of Deposit [Member]
Financial assets
Total cash equivalents		$ 257
Level 3 [Member]
Financial liabilities
Derivative liabilities	3,400
Total financial liabilities	$ 3,400

Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development expenses	$ 6,768	$ 3,980
Prepaid other and other current assets	1,609	2,114
Prepaid expenses and other current assets	$ 8,377	$ 6,094

Document and Entity Information - shares	9 Months Ended
Document and Entity Information - shares	Sep. 30, 2024	Nov. 01, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Trading Symbol	SLDB
Entity Registrant Name	Solid Biosciences Inc.
Entity Current Reporting Status	Yes
Entity Central Index Key	0001707502
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		39,954,607
Entity File Number	001-38360
Entity Tax Identification Number	90-0943402
Entity Address, Address Line One	500 Rutherford Avenue
Entity Address, City or Town	Third FloorCharlestown
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02129
City Area Code	617
Local Phone Number	337-4680
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.001 par value per share
Security Exchange Name	NASDAQ
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false

Commitments and Contingencies

9 Months Ended

Sep. 30, 2024

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

10. Commitments and Contingencies

Letter of credit

The Company had an outstanding letter of credit in the amount of $1.9 million and $1.8 million at September 30, 2024 and December 31, 2023, respectively, which is required as a condition of the Company’s office and laboratory lease.

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 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 of the Company. 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 condensed consolidated financial statements as of September 30, 2024 and December 31, 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 September 30, 2024.

Prepaid Expenses and Other Current Assets

9 Months Ended

Sep. 30, 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 consist of the following:


	September 30, 2024		December 31, 2023
Prepaid research and development expenses	$	6,768	$	3,980
Prepaid other and other current assets		1,609		2,114
Total	$	8,377	$	6,094

Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2024

Fair Value Disclosures [Abstract]

Summary of Financial Assets and Liabilities that are Measured at Fair Value on a Recurring Basis

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


	September 30, 2024
	Level 1		Level 2		Level 3		Total
Financial assets
Cash equivalents:
Money market funds	$	—	$	19,622	$	—	$	19,622
Treasury bills		—		4,991		—		4,991
Government bonds		—		1,298		—		1,298
Total cash equivalents		—		25,911		—		25,911
Available-for-sale securities (Note 5):
Treasury bills		—		63,635		—		63,635
Government bonds		—		43,088		—		43,088
Total available-for-sale securities		—		106,723		—		106,723
Total financial assets	$	—	$	132,634	$	—	$	132,634

Financial liabilities
Derivative liabilities	$	—	$	—	$	3,400	$	3,400
Total financial liabilities	$	—	$	—	$	3,400	$	3,400


	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 are as follows:


Derivative Liabilities	Fair Values at September 30, 2024	Valuation Technique	Unobservable Input	Range	Average
Development Milestones	$3,400	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

Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - USD ($) $ in Thousands	3 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023
Statement of Stockholders' Equity [Abstract]
Issuance costs			$ 4,407
Pre-funded warrants issuance costs			704
Sales commissions	$ 79	$ 138	$ 78	$ 65

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Office and Laboratory Lease [Member]
Commitment And Contingencies [Line Items]
Letter of credit outstanding amount	$ 1.9	$ 1.8

Available-for-Sale Securities - Additional Information (Detail)	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities average maturity period	6 months	4 months 24 days

Fair Value Measurements - Summary of Significant Unobservable Inputs for Derivative Liabilities (Detail) $ in Thousands	Sep. 30, 2024 USD ($) yr
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Fair Value \| $	$ 3,400
Level 3 [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Fair Value \| $	$ 3,400
Level 3 [Member] \| Probability of Achieving Certain Development Milestones [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.02
Level 3 [Member] \| Probability of Achieving Certain Development Milestones [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.80
Level 3 [Member] \| Probability of Achieving Certain Development Milestones [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.024
Level 3 [Member] \| Volatility [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	1.14
Level 3 [Member] \| Volatility [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	1.14
Level 3 [Member] \| Discount Rate [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.035
Level 3 [Member] \| Discount Rate [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.048
Level 3 [Member] \| Discount Rate [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.038
Level 3 [Member] \| Timing of Achieving Certain Development Milestones [Member] \| Minimum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	0.3
Level 3 [Member] \| Timing of Achieving Certain Development Milestones [Member] \| Maximum [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	5.5
Level 3 [Member] \| Timing of Achieving Certain Development Milestones [Member] \| Average [Member]
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Derivative Liabilities, Unobservable Input	28.6

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current assets:
Cash and cash equivalents	$ 64,394	$ 74,015
Available-for-sale securities	106,723	49,625
Prepaid expenses and other current assets	8,377	6,094
Total current assets	179,494	129,734
Non-current assets:
Operating lease, right-of-use assets	24,859	26,539
Property and equipment, net	5,067	6,624
Other non-current assets	475	209
Restricted cash	1,931	1,833
Total non-current assets	32,332	35,205
Total assets	211,826	164,939
Current liabilities:
Accounts payable	3,458	2,032
Accrued expenses and other current liabilities	13,227	10,161
Operating lease liabilities	1,718	1,855
Finance lease liabilities	1,051	469
Derivative liabilities	3,400	0
Total current liabilities	22,854	14,517
Non-current liabilities:
Operating lease liabilities, excluding current portion	21,643	22,707
Finance lease liabilities, excluding current portion	307	1,234
Total non-current liabilities	21,950	23,941
Total liabilities	44,804	38,458
Commitments and contingencies (Note 10)
Preferred stock, $0.001 par value - 10,000,000 shares authorized; no shares issued and outstanding at September 30, 2024 and December 31, 2023
Common stock, $0.001 par value - 120,000,000 and 60,000,000 shares authorized; at September 30, 2024 and December 31, 2023, respectively; 38,930,203 and 20,386,606 shares issued and outstanding at September 30, 2024 and December 31, 2023, respectively	39	20
Additional paid-in capital	907,720	785,199
Accumulated other comprehensive income	116	15
Accumulated deficit	(740,853)	(658,753)
Total stockholders’ equity	167,022	126,481
Total liabilities and stockholders’ equity	$ 211,826	$ 164,939

Equity-Based Compensation - Summary of Restricted Stock Unit Activity (Detail) - Restricted Stock Units [Member]	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Nonvested RSUs at January 1, 2024 \| shares	877,181
Granted \| shares	1,124,028
Vested \| shares	(237,315)
Forfeitures \| shares	(244,607)
Nonvested RSUs at September 30, 2024 \| shares	1,519,287
Share-Based Compensation Arrangement by Share-Based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Nonvested RSUs at January 1, 2024 \| $ / shares	$ 6.37
Granted \| $ / shares	8.03
Vested \| $ / shares	6.69
Forfeitures \| $ / shares	6.88
Nonvested RSUs at September 30, 2024 \| $ / shares	$ 7.47

Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	$ 13,227	$ 10,161
Accrued Research and Development Expense [Member]
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	6,643	2,614
Accrued Compensation [Member]
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	5,117	5,948
Accrued Other and Other Current Liabilities [Member]
Accrued Expenses And Other Current Liabilities [Line Items]
Accrued expenses and other current liabilities	$ 1,467	$ 1,599

Net Loss per Share - Schedule Computation of Basic and Diluted Net Loss per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share Basic [Line Items]
Net loss	$ (32,725)	$ (25,072)	$ (24,303)	$ (20,980)	$ (24,629)	$ (30,070)	$ (82,100)	$ (75,679)
Weighted average shares of common stock outstanding, basic	41,443,317			20,059,641			40,182,303	19,767,174
Weighted average shares of common stock outstanding, diluted	41,443,317			20,059,641			40,182,303	19,767,174
Net loss per share, basic	$ (0.79)			$ (1.05)			$ (2.04)	$ (3.83)
Net loss per share, diluted	$ (0.79)			$ (1.05)			$ (2.04)	$ (3.83)
Common Stock [Member]
Earnings Per Share Basic [Line Items]
Weighted average shares of common stock outstanding, basic	38,730,839			20,059,641			37,568,821	19,767,174
Weighted average shares of common stock outstanding, diluted	38,730,839			20,059,641			37,568,821	19,767,174
Pre-Funded Warrants [Member]
Earnings Per Share Basic [Line Items]
Weighted average shares of common stock outstanding, basic	2,712,478						2,613,482
Weighted average shares of common stock outstanding, diluted	2,712,478						2,613,482

- 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

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-SubTopic 10
-Name Accounting Standards Codification
-Section 55
-Paragraph 4J
-Publisher FASB
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-Name Accounting Standards Codification
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-Subparagraph (a)
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-Topic 810
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+ Details

License and Research Agreements

9 Months Ended

Sep. 30, 2024

Organization, Consolidation and Presentation of Financial Statements [Abstract]

License and Research Agreements

3. License and Research Agreements

On June 29, 2023, the Company entered into a license agreement (the “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 Agreement, Maugeri granted the Company an exclusive worldwide sublicensable license for certain Maugeri patent rights, including existing patent rights, and those in any improvements or know-how made in performance of the 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 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 Agreement was regulatory review in Italy, which was completed in the third quarter of 2023 and, upon the completion of the condition precedent, the 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.

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

Accrued Expenses and Other Current Liabilities (Tables)

9 Months Ended

Sep. 30, 2024

Payables and Accruals [Abstract]

Summary of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:


	September 30, 2024		December 31, 2023
Accrued research and development expense	$	6,643	$	2,614
Accrued compensation		5,117		5,948
Accrued other and other current liabilities		1,467		1,599
Total	$	13,227	$	10,161

Equity-Based Compensation - Schedule of Equity-based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,995	$ 1,625	$ 6,698	$ 5,687
Research and Development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	934	677	2,314	2,285
General and Administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,061	$ 948	$ 4,384	$ 3,402

Equity-Based Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 11, 2024	Jun. 30, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Mar. 31, 2024	Dec. 31, 2023
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding			2,941,043		2,941,043			2,259,672
Common stock purchased					1,219,522
Weighted average grant date fair value of stock options granted			$ 7.56	$ 3.28	$ 6.96	$ 5.04
Stock-based compensation expense			$ 2,995	$ 1,625	$ 6,698	$ 5,687
Equity-based compensation expense					$ 6,698	5,687
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted					1,124,028
Weighted average grant date fair value					$ 8.03
Unrecognized equity-based compensation			9,400		$ 9,400
Unrecognized equity-based compensation cost, weighted average period					3 years 29 days
Equity-based compensation expense			$ 800	700	$ 2,200	1,600
Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted			0		2,165,325
Weighted average grant date fair value			$ 7.51		$ 7.51
Unrecognized equity-based compensation			$ 3,300		$ 3,300
Unrecognized equity-based compensation cost, weighted average period					2 years 1 month 17 days
Percentage of vesting		25.00%
Stock-based compensation expense			600		$ 700
Description of vesting rights					Each PSU represents the contingent right to receive one share of the Company’s common stock.
Unvested Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized equity-based compensation			10,500		$ 10,500
Unrecognized equity-based compensation cost, weighted average period					2 years 6 months 21 days
Employee Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity-based compensation expense			$ 1,600	$ 900	$ 3,600	$ 4,000
2020 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options outstanding			2,007,144		2,007,144
Number of shares available for future issuance			171,622		171,622
2020 Equity Incentive Plan [Member] \| Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units outstanding			1,007,794		1,007,794
2020 Equity Incentive Plan [Member] \| Performance Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock units outstanding			2,165,325		2,165,325
Amended and Restated 2020 Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock reserved for issuance	2,000,000
2024 Inducement Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for common stock for equity awards							1,000,000
Stock options outstanding			100,000		100,000
Stock units outstanding			227,141		227,141
Number of shares available for future issuance			672,859		672,859

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net loss	$ (82,100)	$ (75,679)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of discount on available-for-sale securities	(2,789)	(1,257)
Equity-based compensation expense	6,698	5,687
Depreciation, impairment, and amortization expense	1,967	2,368
Non-cash lease expense	1,826	1,881
Non-cash acquired in-process research and development	3,400	0
Other	(90)	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(2,549)	1,124
Accounts payable	1,390	(898)
Operating lease liabilities	(1,262)	(1,261)
Accrued expenses and other liabilities	3,142	(5,322)
Net cash used in operating activities	(70,367)	(73,357)
Cash flows from investing activities:
Purchases of property and equipment	(450)	(1,425)
Proceeds from maturities of available-for-sale securities	134,800	68,632
Purchases of available-for-sale securities	(189,008)	(102,814)
Other	5	0
Net cash used in investing activities	(54,653)	(35,607)
Cash flows from 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	11,512	2,539
Proceeds from exercises of common stock options	438	0
Employee stock purchase plan purchases	145	78
Payments of principal portion of finance lease obligations	(345)	0
Net cash provided by financing activities	115,497	2,617
Net decrease in cash, cash equivalents, and restricted cash	(9,523)	(106,347)
Cash, cash equivalents, and restricted cash at beginning of period	75,848	157,217
Cash, cash equivalents, and restricted cash at end of period	66,325	50,870
Supplemental disclosure of cash flow information:
Cash paid for interest	(265)	0
Supplemental disclosure of non-cash investing and operating activities:
Right-of-use assets acquired through operating leases	407	121
Decrease in right-of-use assets 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 accrued expenses	$ 36	$ 0

Prepaid Expenses and Other Current Assets (Tables)

9 Months Ended

Sep. 30, 2024

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

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist of the following:


	September 30, 2024		December 31, 2023
Prepaid research and development expenses	$	6,768	$	3,980
Prepaid other and other current assets		1,609		2,114
Total	$	8,377	$	6,094

Leases

9 Months Ended

Sep. 30, 2024

Leases [Abstract]

Leases

9. Leases

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.

During the three and nine months ended September 30, 2024, the Company recorded sublease income of $0.2 million and $0.8 million, respectively, within other income, net. During the three and nine months ended September 30, 2023, the Company recorded sublease income of $0.3 million and $0.8 million, respectively.

Nature of the Business and Basis of Presentation - Additional Information (Detail) - USD ($)		3 Months Ended						9 Months Ended
	Jan. 11, 2024	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net loss		$ 32,725,000	$ 25,072,000	$ 24,303,000	$ 20,980,000	$ 24,629,000	$ 30,070,000	$ 82,100,000	$ 75,679,000
Accumulated deficit		740,853,000						740,853,000		$ 658,753,000
Net cash used in operating activities								70,367,000	$ 73,357,000
Cash, cash equivalents and available-for-sale securities		$ 171,100,000						171,100,000
Goodwill recognized in asset acquisition								$ 0
Common stock, shares authorized		120,000,000						120,000,000		60,000,000
Restricted cash		$ 1,900,000						$ 1,900,000
Warrants exercised								0
At-the-Market Offering Sales Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock shares issued		330,670						1,208,287
Proceeds from issuance of common stock		$ 3,100,000						$ 11,500,000
Private Placement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Net proceeds from private placement	$ 103,700,000
Common Stock [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock shares issued		330,670	526,953	350,664		420,000
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
Pre Funded Warrants [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants outstanding					0				0
Pre Funded Warrants [Member] \| Private Placement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrants outstanding	2,712,478
Common stock warrants price per share	$ 5.529

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net loss	$ (32,725)	$ (20,980)	$ (82,100)	$ (75,679)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities	131	(12)	101	70
Comprehensive loss	$ (32,594)	$ (20,992)	$ (81,999)	$ (75,609)

- 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

+ Details

Insider Trading Arrangements

3 Months Ended

Sep. 30, 2024

Trading Arrangements, by Individual

Material Terms of Trading Arrangement

The following table describes, for the third quarter of 2024, each trading arrangement for the sale or purchase of Company securities adopted or terminated by our directors and officers that is either (1) a contract, instruction or written plan intended to satisfy the

affirmative defense conditions of Rule 10b5-1(c) (a “Rule 10b5-1 trading arrangement”) or (2) a “non-Rule 10b5-1 trading arrangement” (as defined in Item 408(c) of Regulation S-K):


Name (Title)	Action Taken (Date of Action)	Type of Trading Arrangement	Nature of Trading Arrangement	Duration of Trading Arrangement	Aggregate Number of Securities
Gabriel Brooks, M.D. (Chief Medical Officer)	Adoption (August 15, 2024)	Durable Rule 10b5-1 trading arrangement for sell-to-cover transactions relating to all equity awards that have or may be granted	Sale	Until final settlement of any covered Restricted Stock Unit (“RSU”)	Indeterminable(1)
Alexander Cumbo (President, Chief Executive Officer and Director)	Adoption (August 18, 2024)	Durable Rule 10b5-1 trading arrangement for sell-to-cover transactions relating to all equity awards that have or may be granted	Sale	Until final settlement of any covered RSU	Indeterminable(1)
Jessie Hanrahan Ph. D. (Chief Regulatory Officer)	Adoption (August 16, 2024)	Durable Rule 10b5-1 trading arrangement for sell-to-cover transactions relating to all equity awards that have or may be granted	Sale	Until final settlement of any covered RSU	Indeterminable(1)
Paul Herzich (Chief Technology Officer)	Adoption (August 16, 2024)	Durable Rule 10b5-1 trading arrangement for sell-to-cover transactions relating to all equity awards that have or may be granted	Sale	Until final settlement of any covered RSU	Indeterminable(1)
Kevin Tan (Chief Financial Officer and Treasurer)	Adoption (August 15, 2024)	Durable Rule 10b5-1 trading arrangement for sell-to-cover transactions relating to all equity awards that have or may be granted	Sale	Until final settlement of any covered RSU	Indeterminable(1)

(1) The number of shares subject to covered RSUs that will be sold to satisfy applicable tax withholding obligations upon vesting is unknown as the number will vary based on the extent to which vesting conditions are satisfied, the market price of the Company’s common stock at the time of settlement and the potential future grant of additional RSUs subject to this arrangement. This trading arrangement, which applies to RSUs whether vesting is based on the passage of time and/or the achievement of performance goals, provides for the automatic sale of shares that would otherwise be issuable on each settlement date of a covered RSU in an amount sufficient to satisfy the applicable withholding obligation, with the proceeds of the sale delivered to the Company in satisfaction of the applicable withholding obligation.

Non-Rule 10b5-1 Arrangement Adopted

false

Non-Rule 10b5-1 Arrangement Terminated

false

Sale [Member] | Gabriel Brooks, M.D [Member]

Trading Arrangements, by Individual

Name

Gabriel Brooks, M.D.

Title

Chief Medical Officer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

August 15, 2024

Rule 10b5-1 Arrangement Terminated

false

Sale [Member] | Alexander Cumbo [Member]

Trading Arrangements, by Individual

Name

Alexander Cumbo

Title

President, Chief Executive Officer and Director

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

August 18, 2024

Rule 10b5-1 Arrangement Terminated

false

Sale [Member] | Jessie Hanrahan Ph. D. [Member]

Trading Arrangements, by Individual

Name

Jessie Hanrahan Ph. D.

Title

Chief Regulatory Officer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

August 16, 2024

Rule 10b5-1 Arrangement Terminated

false

Sale [Member] | Paul Herzich [Member]

Trading Arrangements, by Individual

Name

Paul Herzich

Title

Chief Technology Officer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

August 16, 2024

Rule 10b5-1 Arrangement Terminated

false

Sale [Member] | Kevin Tan [Member]

Trading Arrangements, by Individual

Name

Kevin Tan

Title

Chief Financial Officer and Treasurer

Rule 10b5-1 Arrangement Adopted

true

Adoption Date

August 15, 2024

Rule 10b5-1 Arrangement Terminated

false

Accrued Expenses and Other Current Liabilities

9 Months Ended

Sep. 30, 2024

Payables and Accruals [Abstract]

Accrued Expenses and Other Current Liabilities

7. Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities consist of the following:


	September 30, 2024		December 31, 2023
Accrued research and development expense	$	6,643	$	2,614
Accrued compensation		5,117		5,948
Accrued other and other current liabilities		1,467		1,599
Total	$	13,227	$	10,161

Nature of the Business and Basis of Presentation

9 Months Ended

Sep. 30, 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-501 for the treatment of catecholaminergic polymorphic ventricular tachycardia, and additional assets for the treatment of 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 condensed 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 September 30, 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, 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 nine months ended September 30, 2024.

During the three and nine months ended September 30, 2024, the Company issued and sold 330,670 and 1,208,287 shares of its common stock, respectively, pursuant to the Company's “at-the-market-offering” sales agreement (the “ATM Sales Agreement”), between the Company and Jefferies LLC. During the three and nine months ended September 30, 2024, the Company received net proceeds of $3.1 million and $11.5 million, respectively, from sales pursuant to the ATM Sales Agreement.

The Company has evaluated whether there are conditions and events that, considered in the aggregate, 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

September 30, 2024, the Company had an accumulated deficit of $740.9 million. During the three and nine months ended September 30, 2024, the Company incurred a net loss of $32.7 million and $82.1 million, respectively, and used $70.4 million of cash in operations for the nine months ended September 30, 2024. The Company expects to continue to generate operating losses for the foreseeable future. Based upon its current operating plan, the Company expects that its cash, cash equivalents and available-for-sale securities of $171.1 million excluding restricted cash of $1.9 million, as of September 30, 2024, will be sufficient to fund its operating expenses and capital expenditure requirements for at least twelve months from the date of issuance of these condensed consolidated 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 partnerships and 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.

Basis of presentation

These condensed consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) along with the rules and regulations of the Securities and Exchange Commission for interim financial information and include the accounts of the Company and its wholly owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. The year-end condensed consolidated balance sheet data presented for comparative purposes was derived from the Company’s audited financial statements but does not include all disclosures required by GAAP to constitute a complete set of financial statements. These condensed consolidated financial statements have been prepared on the same basis as the Company’s annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments necessary for a fair statement of the Company’s financial position at September 30, 2024 and its results of operations, changes in stockholders’ equity, and cash flows for the interim periods ended September 30, 2024 and 2023.

These unaudited condensed consolidated interim financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2023. The results of operations for the three and nine months ended September 30, 2024 are not necessarily indicative of the operating results to be expected for the year ending December 31, 2024, for any other interim period, or for any other future year.

Reclassifications

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

Significant judgments and estimates

The preparation of the Company’s condensed 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 condensed consolidated financial statements and the reported amounts of expenses during the reporting periods. Significant estimates and assumptions reflected in these condensed consolidated financial statements include, but are not limited to, estimates related to the 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 materially from the Company’s estimates.

Summary of significant accounting policies

Except as otherwise noted below, there have been no changes to the significant accounting policies disclosed in the Company's most recent Annual Report on Form 10-K.

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. The Company historically has been a private company and lacks company-specific historical and implied volatility information. Therefore, it estimates its expected stock volatility based on the historical volatility of a publicly traded set of peer companies and expects to continue to do so until such time as it has adequate historical data regarding the volatility of its own traded stock price. For options with service-based vesting conditions and options granted to non-employees, the expected term of the Company's stock options 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. Expected dividend yield is 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.

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 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 statement 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.

Asset acquisition

Acquisitions of assets or a group of assets that do not meet the definition of a business are accounted 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 in-process research and development ("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.

Derivative liabilities

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 other expense in the condensed consolidated statements of operations.

Recently issued accounting pronouncements

In November 2023, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures, which requires public entities, including those with a single reportable segment to: (i) provide disclosures of significant segment expenses and other segment items if they are regularly provided to the chief operating decision maker (the CODM) and included in each reported measure of segment profit or loss; (ii) provide all annual disclosures about a reportable segment’s profit or loss and assets currently required by Accounting Standards Codification 280, Segment Reporting, in interim periods; and (iii) disclose the CODM’s title and position, as well as an explanation of how the CODM uses the reported measures and other disclosures. ASU 2023-07 does not change how a public entity identifies its operating segments, aggregates those operating segments or applies the quantitative thresholds to determine its reportable segments. ASU 2023-07 is required to be applied retrospectively and is effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, with early adoption permitted. We expect to include additional disclosures as a result of the implementation ASU 2023-07, however, these changes are not expected to have a material effect on our consolidated financial statements.

In December 2023, the FASB issued ASU 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 2024-03, Disaggregation of Income Statement Expenses (Topic 220) requiring that public business entities disclose additional information about specific expense categories in the notes to financial statements at interim and annual reporting periods. The amendments in this ASU are effective for annual reporting periods beginning after December 15, 2026, and interim reporting periods beginning after December 15, 2027. The requirements in this ASC may be applied either prospectively to financial statements issued for reporting periods after the effective date or retrospectively to any or all prior periods presented in the financial statements. The Company is currently evaluating the impact of adopting this ASU on its consolidated financial statements and disclosures.