Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2024

Stock-Based Compensation

Schedule of stock-based compensation expense

	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development expense	$	384	$	548	$	1,275	$	1,670
General and administrative expense		1,190		1,313		3,643		3,782
Total stock-based compensation expense	$	1,574	$	1,861	$	4,918	$	5,452

Summary of stock option activity

				Weighted
				Average
				Remaining	Aggregate
		Weighted		Contractual	Intrinsic
	Number of	Average		Term	Value (1)
	Stock Options	Exercise Price		(In years)	(In thousands)
Outstanding as of December 31, 2023	7,455,795	$	5.52	8.0	$	—
Granted	2,085,853	$	0.89
Exercised	(7,215)	$	0.55
Cancelled/forfeited	(1,528,062)	$	5.36
Outstanding as of September 30, 2024	8,006,371	$	4.35	8.0	$	99
Exercisable as of September 30, 2024	3,964,796	$	5.92	7.0	$	17

(1) The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock as of the end of the period.

Schedule of assumptions used in determining fair value of options granted

	Nine Months Ended September 30,
	2024			2023
Risk-free interest rate		3.7 - 4.6	%		3.6 - 4.4	%
Expected dividend yield		0	%		0	%
Expected term (in years)		5.5 - 6.1			5.5 - 6.1
Expected volatility		87.7 - 91.4	%		81.7 - 87.3	%

Summary of restricted stock unit activity

	Number	Weighted
	of Shares	Average
	of Restricted	Grant Date
	Stock Units	Fair Value
Unvested as of December 31, 2023	—	$	—
Granted	481,500	$	0.55
Forfeited	(36,000)	$	0.55
Unvested as of September 30, 2024	445,500	$	0.55

Summary of restricted stock activity

	Number	Weighted
	of Shares	Average
	of Restricted	Grant Date
	Common Stock	Fair Value
Unvested as of December 31, 2023	5,617	$	5.51
Vested	(5,617)	$	5.51
Unvested as of September 30, 2024	—	$	—