Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Stock-based Compensation Expense Recognized

Stock‑based compensation expense recognized was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	971	$	285	$	1,756	$	545
General and administrative		2,124		824		4,070		1,538
Total stock-based compensation expense	$	3,095	$	1,109	$	5,826	$	2,083

Weighted-Average Assumptions used in Estimating Fair Value of each Stock Options using Black-Scholes Option-Pricing Model

The fair value of each stock option was estimated using the Black‑Scholes option‑pricing model with the following weighted-average assumptions:

	Six Months Ended June 30,
	2022			2021
Risk-free interest rate		2.00	%		0.80	%
Expected volatility		92.78	%		89.34	%
Expected term (in years)		6.01			6.10
Expected dividend yield		—			—

Summary of Option Activity Changes in Shares Available for Grant under the 2020 Plan

Changes in shares available for grant under the 2020 Plan during the six months ended June 30, 2022 were as follows:

	Shares Available for Grant
Shares available for grant at December 31, 2021		4,442,315
2020 Plan reserve increase on January 1, 2022		1,868,953
Options and restricted stock units granted		(1,998,047	)
Options and restricted stock units forfeited,    cancelled, or expired		143,233
Shares available for grant at June 30, 2022		4,456,454

Summary of Option Activity under the 2020 Plan

A summary of stock option activity under the 2020 Plan for the six months ended June 30, 2022 was as follows:

	Shares			Weighted- Average Exercise price per Share		Weighted- Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance at December 31, 2021		2,270,896		$	12.76	7.22		$	8,306
Granted		1,985,797			10.43
Exercised		(288,457	)		1.02
Forfeited/expired		(129,233	)		17.26
Balance at June 30, 2022		3,839,003		$	12.28		8.82	$	793
Expected to vest		2,957,147		$	12.54		9.20	$	204
Options exercisable		881,856		$	11.42		7.57	$	589

Summary of Stock Options Outstanding and Exercisable under the 2020 Plan

Stock options outstanding and exercisable under the 2020 Plan consisted of the following at June 30, 2022:

Exercise Price ($)	Shares Outstanding		Shares Exercisable
0.16 to 1.35		399,762		279,963
8.93 to 19.94		3,061,320		499,390
20.55 to 29.41		377,921		102,503
Total		3,839,003		881,856

Restricted Stock Units (RSUs)

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Summary of Restricted Stock Activity

A summary of RSU activity for the six months ended June 30, 2022 is as follows:

	Share Equivalent			Weighted- Average Grant Date Fair Value
Non-vested at December 31, 2021		361,500		$	15.32
Granted		12,250			10.54
Cancelled		(14,000	)		15.34
Vested		(119,911	)		15.15
Non-vested at June 30, 2022		239,839		$	15.15