Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2022

Equity [Abstract]

Summary of Stock Option Activity

Stock option activity for employee and nonemployee awards and related information is as follows (in thousands, except per share data):

	Number of Options			Weighted- Average Exercise Price Per Share
Outstanding at December 31, 2021		5,778		$	14.49
Granted		4,040			15.42
Exercised		(282	)		1.12
Forfeited/expired		(443	)		16.60
Outstanding at September 30, 2022		9,093		$	15.22

Schedule of Assumptions Used in Black-Scholes Model Pricing Model to to Determine Fair Value of Stock Option and Shares Purchasable Under ESPP

The assumptions used in the Black-Scholes model to determine the fair value of stock option grants and shares purchasable under the ESPP were as follows:

	Nine Months Ended September 30,
Stock Option Grants	2022	2021
Risk-free interest rate	1.5% - 3.4%	0.5% - 1.2%
Expected volatility	85%	87%-88%
Expected term (in years)	5.5 - 6.1	5.5 - 6.1
Expected dividend yield	—%	—%

	Nine Months Ended September 30,
ESPP	2022	2021
Risk-free interest rate	2.2%	0.1%
Expected volatility	79%	75%
Expected term (in years)	0.5	0.5
Expected dividend yield	—%	—%

Schedule of Allocated Stock-based Compensation Expense

The allocation of stock-based compensation expense was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development expense	$	4,151	$	2,433	$	10,948	$	6,930
General and administrative expense		2,935		2,117		8,884		5,610
Total stock-based compensation expense	$	7,086	$	4,550	$	19,832	$	12,540