Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Summary of Restricted Common Stock Activity

The following table summarizes restricted common stock activity for the year ended December 31, 2021:

	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2021		3,410,979		$	3.55
Granted		1,192,513			33.61
Forfeited		(127,104	)		25.91
Vested		(1,609,479	)		2.87
Unvested at December 31, 2021		2,866,909		$	15.45

Summary of Stock Option Activity

The following table summarizes stock option activity (in thousands, except share and per share data):

	Shares			Weighted Average Exercise Price		Weighted Average Contractual Life		Aggregate Intrinsic Value
Options outstanding at January 1, 2021		3,972,909		$	17.84	9.6		$	81,822
Granted		2,478,888			32.41				—
Exercised		(25,152	)		9.25				274
Forfeited		(271,590	)		25.31				1,047
Options outstanding at December 31, 2021		6,155,055		$	23.42		8.8	$	480
Options vested and exercisable at December 31, 2021		1,310,019		$	17.87		8.6	$	294

Schedule of Estimated Fair Value Weighted-Average Assumptions Using Black-Scholes Option-Pricing Model

The fair value was estimated on the date of grant using the Black-Scholes option-pricing model, with the following weighted-average assumptions:

	Years Ended December 31,
	2021			2020
Expected term (in years)		6.06			6.08
Expected volatility		95	%		95	%
Risk-free interest rate		0.87	%		0.36	%
Expected dividend yield		—			—
Fair value of common stock	$	32.41		$	18.08

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:

	Years Ended December 31,
(in thousands)	2021		2020
Research and development	$	20,632	$	3,571
General and administrative		23,343		5,858
Total stock-based compensation expense	$	43,975	$	9,429