Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:

	Years Ended December 31,
(in thousands)	2022		2021
Research and development	$	14,014	$	20,632
General and administrative		27,301		23,343
Total stock-based compensation expense	$	41,315	$	43,975

Summary of Restricted Common Stock Activity

The following table summarizes restricted common stock activity for the year ended December 31, 2022:

	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2022		2,866,909		$	15.45
Granted		1,632,996			7.70
Forfeited		(348,589	)		17.74
Vested		(1,912,210	)		10.40
Unvested at December 31, 2022		2,239,106		$	13.75

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, 2022		6,155,055		$	23.42	8.8		$	480
Granted		3,051,906			7.48		—		—
Exercised		—			—		—		—
Forfeited		(1,284,164	)		20.13		—		—
Options outstanding at December 31, 2022		7,922,797		$	17.81		8.3	$	786
Options vested and exercisable at December 31, 2022		2,945,832		$	22.10		7.8	$	88

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,
	2022			2021
Expected term (in years)		6.07			6.06
Expected volatility		90	%		95	%
Risk-free interest rate		2.00	%		0.87	%
Expected dividend yield		—			—
Fair value of common stock	$	7.48		$	32.41