Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2022

Share-based Payment Arrangement [Abstract]

Summary of Restricted Common Stock Activity

The following table summarizes restricted common stock activity for the three months ended March 31, 2022:

	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2022		2,866,909		$	15.45
Granted		809,877			9.20
Forfeited		(53,291	)		29.96
Vested		(698,241	)		12.83
Unvested at March 31, 2022		2,925,254		$	14.08

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 (in years)		Aggregate Intrinsic Value
Options outstanding at January 1, 2022		6,155,055		$	23.42		8.80	$	480
Granted		1,764,190			9.19		—		—
Exercised		—			—		—		—
Forfeited		(411,939	)		25.10		—		—
Options outstanding at March 31, 2022		7,507,306		$	19.98		8.88	$	181
Options vested and exercisable at March 31, 2022		1,709,930		$	21.44		8.41	$	122

Schedule of Estimated Fair Value 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:

	Three Months Ended March 31, 2022
Expected term (in years)		6.11
Expected volatility		90.53	%
Risk-free interest rate		1.73	%
Expected dividend yield		—
Fair value of common stock	$	9.19

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:

	Three Months Ended March 31,
(in thousands)	2022		2021
Research and development	$	3,341	$	3,311
General and administrative		7,126		4,792
Total stock-based compensation expense	$	10,467	$	8,103