Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Summary of Assumptions that Used to Determine Grant-Date Fair Value of Stock Options Granted to Employees and Members of Board of Directors

The assumptions that the Company used to determine the grant-date fair value of stock options granted to employees and members of the board of directors were as follows, presented on a weighted-average basis:

	Six Months Ended June 30,
	2022			2021
Expected option life (years)		5.96			6.07
Risk-free interest rate		1.80	%		0.76	%
Expected volatility		80.22	%		81.25	%
Expected dividend yield		—	%		—	%

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity for the six months ended June 30, 2022:

	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2021		7,423,777		$	13.54		6.79	$	1,469
Granted		3,455,157		$	1.79
Exercised		—		$	—
Cancelled or forfeited		(1,965,618	)	$	14.09
Outstanding as of June 30, 2022		8,913,316		$	8.86		7.55	$	112
Exercisable as of June 30, 2022		3,097,657		$	12.71		5.92	$	112

Summary of Restricted Common Stock Units

The following table summarizes the Company’s restricted common stock units for the six months ended June 30, 2022:

	Number of Shares			Weighted- Average Grant Date Fair Value
Issued and unvested as of December 31, 2021		599,850		$	9.64
Granted		719,168		$	1.75
Vested		(287	)	$	15.65
Forfeited, cancelled or expired		(425,472	)	$	7.40
Issued and unvested as of June 30, 2022		893,259		$	4.35

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was allocated as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	783	$	1,909	$	1,721	$	4,024
General and administrative		2,451		2,782		4,890		5,302
Total stock-based compensation expense	$	3,234	$	4,691	$	6,611	$	9,326