Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2023		2022		2023		2022
Research and development	$	3,514	$	3,892	$	6,937	$	7,232
General and administrative		6,774		7,059		13,380		14,186
Total stock-based compensation expense	$	10,288	$	10,951	$	20,317	$	21,418

Summary of Restricted Common Stock Activity

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

	Shares			Weighted Average Grant Date Fair Value
Unvested at January 1, 2023		2,239,106		$	13.75
Granted		2,074,444			6.31
Forfeited		(296,252	)		11.78
Vested		(513,839	)		12.67
Unvested at June 30, 2023		3,503,459		$	9.67

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		3,400,892			6.60		—		—
Exercised		—			—		—		—
Forfeited		(1,019,286	)		15.83		—		—
Options outstanding at June 30, 2023		10,304,403		$	14.31		8.39	$	19
Options vested and exercisable at June 30, 2023		3,751,655		$	19.66		7.60	$	19

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 June 30, 2023			Six Months Ended June 30, 2023
Expected term (in years)		6.09			6.11
Expected volatility		93.95	%		94.49	%
Risk-free interest rate		3.61	%		3.46	%
Expected dividend yield		—		—
Fair value of common stock	$	3.76		$	6.60