Stock-Based Compensation Expense (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

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):

	Year Ended December 31,
	2023		2022
Research and development	$	1,176	$	850
General and administrative		4,711		4,597
Total	$	5,887	$	5,447

Summary of Restricted Stock Unit Activity

A summary of the restricted stock unit activity under the Plans for the year ended December 31, 2023 was as follows:

	Shares			Weighted- Average Grant Date Fair Value
Restricted stock units outstanding as of December 31, 2022		28,212		$	4.78
Granted		115,790		$	2.85
Vested		(7,041	)	$	4.78
Forfeited		(31,913	)	$	2.97
Restricted stock units outstanding as of December 31, 2023		105,048		$	3.20

Schedule of Unrecognized Stock-Based Compensation

The following table summarizes the Company’s unrecognized stock-based compensation as of December 31, 2023:

	Year Ended December 31,
	Unrecognized Expense (in thousands)		Period of Recognition (years)
Restricted stock units	$	254		2.9
Stock options		7,107		2.3
Total	$	7,361

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 Options Granted to Certain 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 the options granted to certain executive officers with performance grants, with the following weighted-average assumptions:

	Year Ended December 31,
	2023			2022
Risk-free interest rate		3.9	%		2.7	%
Expected dividend yield		—	%		—	%
Expected term (in years)		6.1			6.0
Expected volatility		82.7	%		81.3	%

Summary of Stock Option Activity Under Plans

A summary of the stock option activity under the Plans for the year ended December 31, 2023 was as follows:

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding December 31, 2022		4,311,333		$	7.07		8.2	$	378
Granted		1,860,647			2.93
Exercised		(57,377	)		1.75
Cancelled		(404,623	)		8.44
Outstanding at December 31, 2023		5,709,980		$	5.68		8.0	$	6,334
Exercisable at December 31, 2023		1,775,214		$	8.75		6.6	$	1,579
Vested and expected to vest at December 31, 2023		5,709,980		$	5.68		8.0	$	6,334