Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Summary of Activity under Stock Option Plans and Related Information

The following table summarizes activity under the Company’s stock option plans and related information (in thousands, except share and per share amounts):

	Number of Options Outstanding			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2023		13,110,717		$	2.60		7.1	$	118
Options granted		3,541,000		$	0.90
Options cancelled/forfeited		(1,395,135	)	$	2.84
Outstanding as of June 30, 2024		15,256,582		$	2.18		7.2	$	—
Vested and exercisable as of June 30, 2024		8,334,868		$	2.58		5.7	$	—

Summary of RSU Activity

	Number of RSUs Outstanding			Weighted Average Grant-Date Fair Price
Outstanding as of December 31, 2023		219,609		$	9.20
RSUs vested		(22,282	)	$	9.63
RSUs forfeited		(11,911	)	$	9.26
Outstanding as of June 30, 2024		185,416		$	9.14

Stock-Based Compensation Expense Recognized

Total stock-based compensation expense recognized by function was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	915	$	2,013	$	1,971	$	4,281
General and administrative		2,170		2,007		4,548		4,002
Total stock-based compensation expense	$	3,085	$	4,020	$	6,519	$	8,283

Fair Value of Employee Stock Options Granted is Calculated Using Black Scholes Option Pricing Model with Range of Assumptions

The fair value of the stock options granted is calculated using the Black-Scholes option-pricing model with the following range of assumptions:

	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Expected term (years)	5.5 - 6.1		5.5 - 6.1		5.5 - 6.1		5.5 - 6.1
Expected volatility	86.8 - 87.7	%	88.0 - 88.3	%	86.8 - 87.9	%	87.8 - 88.3	%
Risk-free interest rate	4.3 - 4.6	%	3.5 - 3.9	%	4.0 - 4.6	%	3.5 - 4.3	%
Expected dividend yield	—		—		—		—