Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

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

Summary of Stock Option Activity

A summary of the Company’s stock option activity under the 2021 Plan and 2018 Plan is as follows (in thousands, except share and per share data and years):

						Weighted-
				Weighted-		average remaining		Aggregate
				average		contractual		intrinsic
	Shares			exercise price		term (years)		value
Outstanding at December 31, 2021		13,818,212		$	3.87		8.82	$	163,264
Granted		5,291,546			10.67
Exercised		(537,229	)		1.55
Canceled		(920,257	)		4.98
Outstanding at June 30, 2022		17,652,272		$	5.69		8.53	$	30,695
Options exercisable at June 30, 2022		5,704,373		$	3.29		7.79	$	16,089

Summary of Restricted Stock Activity

The summary of the Company’s restricted stock activity during the six months ended June 30, 2022 is as follows:

	Number of			Weighted-
	restricted			average
	stock shares			grant date
	outstanding			fair value
Nonvested at December 31, 2021		212,941		$	0.001
Vested		(167,186	)		0.001
Forfeited		(6,945	)		0.001
Nonvested at June 30, 2022		38,810		$	0.001

Schedule of Stock-based Compensation Expense

The allocation of stock-based compensation for all stock awards was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	3,003	$	925	$	5,735	$	1,416
General and administrative		2,052		711		3,762		1,015
Total	$	5,055	$	1,636	$	9,497	$	2,431

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consisted of the following as of June 30, 2022 and December 31, 2021:

	June 30,		December 31,
	2022		2021
Stock options issued and outstanding		17,652,272		13,818,212
Awards available for future grant		16,404,213		14,699,430
Shares available for purchase under the ESPP		1,017,371		1,168,013
Total		35,073,856		29,685,655

Stock Options

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

Assumptions used to Determine Fair Value of Stock Option Grants and Stock to be Purchased under ESPP

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

	Three Months Ended June 30,		Six Months Ended June 30,
	2022	2021	2022	2021
Risk-free interest rate	2.53%-3.23%	1.02%-1.09%	1.46%-3.23%	0.59%-1.09%
Expected volatility	85.51%-87.11%	82.08%-82.54%	85.51%-87.11%	82.08%-83.88%
Expected term (in years)	5.50-6.08	6.08	5.50-6.08	6.08
Expected dividend yield	--%	--%	--%	--%

ESPP

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

Assumptions used to Determine Fair Value of Stock Option Grants and Stock to be Purchased under ESPP

The assumptions used in the Black-Scholes option pricing model to determine the fair value of the stock to be purchased under the ESPP were as follows:

	Three Months Ended June 30,		Six Months Ended June 30,
	2022	2021(1)	2022	2021(1)
Risk-free interest rate	2.24%-3.14%	--%	2.24%-3.14%	--%
Expected volatility	84.74%-87.89%	--%	84.74%-87.89%	--%
Expected term (in years)	0.50-1.99	--	0.50-1.99	--
Expected dividend yield	--%	--%	--%	--%

(1) The ESPP was not in effect until July 2021.