Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

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

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

	Year Ended December 31,
	2021			2020
Expected option life (years)		6.06			6.00
Risk-free interest rate		0.80	%		0.76	%
Expected volatility		81.22	%		76.02	%
Expected dividend yield		—	%		—	%

Summary of Stock Option Activity

The following table summarizes the Company’s stock option activity for the year ended December 31, 2021:

	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding as of December 31, 2020		5,559,545		$	14.97		7.65	$	13,511
Granted		4,253,232		$	12.64
Exercised		(226,180	)	$	4.07
Cancelled or forfeited		(2,162,820	)	$	16.55
Outstanding as of December 31, 2021		7,423,777		$	13.54		6.79	$	1,468,969
Exercisable as of December 31, 2021		2,690,230		$	12.87		5.69	$	1,466,939

Summary of Restricted Stock Award and Restricted Stock Unit Activity

The following table summarizes the Company’s restricted stock award and restricted stock unit activity for the year ended December 31, 2021:

	Number of Shares			Weighted- Average Grant Date Fair Value
Issued and unvested as of December 31, 2020		1,198		$	15.65
Granted		771,600		$	9.63
Vested		(575	)	$	15.65
Forfeited, cancelled or expired		(172,373	)	$	9.63
Issued and unvested as of December 31, 2021		599,850		$	9.64

Schedule of Stock-based Compensation Expense

Stock-based compensation expense was allocated as follows:

	Year Ended December 31,
	2021		2020
Research and development	$	6,996	$	8,207
General and administrative		11,583		7,421
Total stock-based compensation expense	$	18,579	$	15,628