Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2022

Summary of Assumptions Used in Black-Scholes Option Pricing Model

	Three Months Ended		Nine Months Ended
	September 30,		September 30,
	2022	2021	2022	2021
Risk-free interest rate	2.65% - 4.09%	0.92% - 1.01%	1.70% - 4.09%	0.66% - 1.23%
Expected volatility	77.7% - 78.2%	83.0% - 83.4%	77.7% - 81.9%	71.6% - 83.5%
Expected dividend yield	0%	0%	0%	0%
Expected life of employee and Board options (in years)	6.25	6.25	6.25	6.25

Summary of Compensation Expense Relating to Stock Options

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2022		2021		2022		2021
Research and development	$	1,719	$	1,833	$	5,380	$	5,228
General and administrative		1,149		1,205		5,137		3,444
Total stock option expense	$	2,868	$	3,038	$	10,517	$	8,672

Summary of Stock Option Activity

		Weighted
	Number of	Average Exercise
	Shares	Price
Outstanding, December 31, 2021	6,512,280	$	15.58
Granted	1,739,919		10.28
Exercised	(46,277)		6.26
Forfeited	(356,819)		14.50
Expired	(194,580)		16.21
Outstanding, September 30, 2022	7,654,523	$	14.47
Options exercisable, September 30, 2022	4,764,271

Employees And Non-Employee Members Of Board Of Directors [Member]

Summary of Restricted Stock Unit Activity

		Weighted
	Number of	Average Grant
	Units	Date Fair Value
Outstanding, December 31, 2021	576,544	$	17.50
Awarded	466,926		10.11
Vested and released	(206,518)		16.74
Forfeited	(196,002)		17.06
Outstanding, September 30, 2022	640,950	$	12.50
Restricted stock units exercisable (vested and deferred), September 30, 2022	—