Stock-Based Compensation Expense (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Summary of Restricted Stock Unit Activity

A summary of the restricted stock unit activity under the Plans for the six months ended June 30, 2024 was as follows:

	Shares			Weighted- Average Grant Date Fair Value
Restricted stock units outstanding as of December 31, 2023		105,048		$	3.20
Granted		984,929		$	5.49
Vested		(27,869	)	$	3.29
Forfeited		(194,636	)	$	4.28
Restricted stock units outstanding as of June 30, 2024		867,472		$	5.56

Summary of Stock Option Activity Under Plans

A summary of the stock option activity under the Plans for the six months ended June 30, 2024 was as follows:

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2023		5,709,980		$	5.68		8.0	$	6,334
Granted		2,605,002			4.89
Exercised		(1,002	)		3.96
Cancelled		(1,268,147	)		4.56
Outstanding at June 30, 2024		7,045,833		$	5.59		8.0	$	—

Schedule of Fair Value of Stock Option Estimated on Date of Grant Using Black-Scholes Option-Pricing Model or Monte Carlo Simulation in Case of Certain Options Granted to Executive Officers

The fair value of each stock option granted to employees, directors and non-employees was estimated on the date of grant using the Black-Scholes option-pricing model, or a Monte Carlo simulation in the case of certain options granted to executive officers, with the following weighted-average assumptions for the three and six months ended June 30, 2024 and 2023:

	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Risk-free interest rate		4.4	%		3.8	%		4.2	%		3.7	%
Expected dividend yield		—	%		—	%		—	%		—	%
Expected term (in years)		5.7			6.1			6.0			6.0
Expected volatility		111.5	%		82.0	%		80.5	%		82.9	%

The weighted-average fair value of options granted to employees, directors and non-employees during the three months ended June 30, 2024 and 2023 was $1.19 and $2.24, respectively.

Schedule of Stock-Based Compensation Expense

Stock-based compensation expense included in the Company’s consolidated statements of operations and comprehensive loss was as follows (in thousands):

	Three Months Ended June 30,					Six Months Ended June 30,
	2024			2023		2024		2023
Research and development	$	(290	)	$	287	$	413	$	571
General and administrative		1,414			1,067		2,873		2,393
Total	$	1,124		$	1,354	$	3,286	$	2,964