Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2023

Share-Based Payment Arrangement [Abstract]

Summary of common stock reserved for future issuance

As of June 30, 2023, the Company had reserved shares of its common stock for future issuance as follows:

	Shares Reserved
Common stock options outstanding		6,001,185
Unvested restricted stock units		364,500
Available for future grants under the 2021 Equity Incentive Plan		1,543,869
Available for future grants under the 2021 Employee Stock Purchase Plan		546,341
Total shares of common stock reserved		8,455,895

Summary of the Company's stock option activity

A summary of the Company’s stock option activity and related information during the six months ended June 30, 2023 is as follows:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2022		5,877,745		$	4.47		8.2	$	907
Granted		382,915		$	6.83
Exercised		(77,812	)	$	1.97
Forfeited/Expired		(181,663	)	$	5.60
Outstanding at June 30, 2023		6,001,185		$	4.62		8.0	$	14,005
Vested at June 30, 2023		2,692,861		$	4.93		7.1	$	5,566
Exercisable at June 30, 2023		3,263,418		$	4.92		7.2	$	6,509

Summary of weighted-average assumptions to determine the fair value of the employee stock option

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows:

	Three Months Ended June 30,						Six Months Ended June 30,
	2023			2022			2023			2022
Risk-free interest rate		3.8	%		3.0	%		3.8	%		2.3	%
Expected volatility		88.4	%		84.4	%		87.2	%		84.9	%
Expected term (in years)		5.8			5.8			5.9			5.9
Expected dividend yield		—	%		—	%		—	%		—	%

Summary of RSU activity

RSUs consist of performance-based units (PSUs) and market-based units (MSUs). The following table summarizes RSU activity during the six months ended June 30, 2023:

	Number of RSUs			Weighted-Average Grant Date Fair Value
Unvested at December 31, 2022		329,500		$	5.70
Granted		40,000		$	3.63
Cancelled		(5,000	)	$	2.14
Unvested at June 30, 2023		364,500		$	5.52

Summary of Non-cash stock-based compensation expense recorded

The following table summarizes stock-based compensation expense, including expense associated with award modifications for unvested options, reflected in the consolidated statements of operations and comprehensive loss (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
Research and development	$	494	$	386	$	967	$	773
General and administrative		713		620		1,397		1,340
Total	$	1,207	$	1,006	$	2,364	$	2,113