Stock-Based Compensation Expense (Tables)

6 Months Ended

Jun. 30, 2023

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, 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		270,716		$	2.85
Vested		(7,041	)	$	4.78
Forfeited		(48,184	)	$	2.93
Restricted stock units outstanding as of June 30, 2023		243,703		$	3.00

Summary of Stock Option Activity Under Plans

A summary of the stock option activity under the Plans for the six months ended June 30, 2023 was as follows:

	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022		4,311,333		$	7.07		8.2	$	378
Granted		1,976,180			2.85
Exercised		(57,377	)		1.75
Cancelled		(358,323	)		8.13
Outstanding at June 30, 2023		5,871,813		$	5.63		8.5	$	3,090

Schedule of Fair Value of Stock Option Estimated on Date of Grant Using Black-Scholes Option-Pricing Model in Case of 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 in the case of the options granted to executive officers, with the following weighted-average assumptions for the three and six months ended June 30, 2023 and 2022:

	Three Months Ended June 30,						Six Months Ended June 30,
	2023			2022			2023			2022
Risk-free interest rate		3.8	%		3.2	%		3.7	%		2.5	%
Expected dividend yield		—	%		—	%		—	%		—	%
Expected term (in years)		6.1			2.1			6.0			3.3
Expected volatility		82.0	%		80.6	%		82.9	%		80.7	%

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,
	2023		2022		2023		2022
Research and development	$	287	$	209	$	571	$	436
General and administrative		1,067		898		2,393		1,515
Total	$	1,354	$	1,107	$	2,964	$	1,951