Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
(in thousands)	2023		2022		2023		2022
Research and development	$	3,254	$	3,890	$	10,191	$	11,122
General and administrative		7,214		6,965		20,594		21,151
Total stock-based compensation expense	$	10,468	$	10,855	$	30,785	$	32,273

Summary of Restricted Common Stock Activity

The following table summarizes restricted common stock activity for the nine months ended September 30, 2023:

	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2023		2,239,106		$	13.75
Granted		2,254,094			6.06
Forfeited		(318,394	)		11.36
Vested		(764,415	)		12.59
Unvested at September 30, 2023		3,410,391		$	9.16

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, 2023		7,922,797		$	17.81		8.30	$	786
Granted		3,731,242			6.30		—		—
Exercised		—			—		—		—
Forfeited		(1,208,727	)		16.38		—		—
Options outstanding at September 30, 2023		10,445,312		$	13.86		8.19	$	—
Options vested and exercisable at September 30, 2023		4,114,133		$	18.99		7.40	$	—

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:

	Three Months Ended September 30, 2023			Nine Months Ended September 30, 2023
Expected term (in years)		6.09			6.11
Expected volatility		94.36	%		94.48	%
Risk-free interest rate		4.01	%		3.51	%
Expected dividend yield		—		—
Fair value of common stock	$	3.24		$	6.30