Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2022

Share-based Payment Arrangement [Abstract]

Stock-based Compensation Expense Recognized

Total stock-based compensation expense recognized in the condensed consolidated statements of operations for the three months ended March 31, 2022 and 2021 was as follows (in thousands):

	Three Months Ended March 31,
	2022		2021
Research and development	$	781	$	140
General and administrative	964		399
Total stock-based compensation	$	1,745	$	539

Restricted Stock Awards Activity

The following table summarizes restricted stock award activity during the three months ended March 31, 2022 (in thousands, except per share amounts):

	Shares/Units	Weighted-Average Grant Date Fair Value Per Share
Unvested at December 31, 2021	295	$	1.35
Granted	—	$	—
Vested	(61)	$	1.33
Forfeited	—	$	—
Unvested at March 31, 2022	234	$	1.36

Weighted -average Valuation Assumptions

The fair value of stock options granted during the three months ended March 31, 2022 and 2021 was calculated on the date of grant using the following weighted-average assumptions:

	Three Months Ended March 31,
	2022		2021
Risk-free interest rate	1.6	%	0.8	%
Expected term (in years)	6.0		6.0
Dividend yield	—	%	—	%
Expected volatility	76.0	%	79.8	%

Summary of Stock Option Activity

The following table summarizes stock option activity during the three months ended March 31, 2022 (in thousands, except per share amounts): 

	Options Outstanding
	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)
Outstanding at December 31, 2021	3,266	$	8.24	9.02
Granted	928	$	11.34
Exercised	(46)	$	2.83
Cancelled	(15)	$	7.69
Outstanding at March 31, 2022	4,133	$	9.00	9.00
Exercisable at March 31, 2022	818	$	5.73	8.65