Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2022

Equity [Abstract]

Summary of Stock Option Activity

Stock option activity in 2022 for employee and non-employee awards and related information is as follows (in thousands, except per share and contractual term data):

	Shares Available for Grant	Number of Outstanding Options	Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)	Aggregate Intrinsic Value
Balance at December 31, 2021	2,575	5,778	$	14.49
Additional shares authorized under 2020 Plan	2,387	—
Shares authorized under Inducement Plan	1,500	—
Granted	(4,450)	4,450	15.42
Exercised	—	(351)	1.34
Forfeited/expired	525	(525)	17.05
Balance at December 31, 2022	2,537	9,352	$	15.28	8.34	$	72,280
Vested and expected to vest at December 31, 2022		9,352	$	15.28	8.34	$	72,280
Exercisable at December 31, 2022		3,659	$	13.42	7.64	$	36,120

The following summarizes additional information regarding stock options (in thousands, except per share data):

	Year Ended December 31,
	2022		2021		2020
Cash received from options exercised	$	470	$	930	$	53
Intrinsic value of options exercised	$	6,724	$	3,436	$	516
Weighted-average grant date fair value per share	$	11.11	$	16.78	$	11.63

Schedule of Share-Based Payment Award, Stock Options, Valuation Assumptions

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:

	Options			ESPP
	Year Ended December 31,			Year Ended December 31,
	2022	2021	2020	2022	2021	2020
Risk-free interest rate	1.5% - 4.2%	0.5% - 1.3%	0.3% - 1.5%	2.2% - 4.7%	0.1%	0.1% - 0.2%
Expected volatility	85%	86% - 88%	88% - 92%	78% - 79%	69% - 75%	75% - 96%
Expected term (in years)	5.5 - 6.1	5.5 - 6.1	5.4 - 6.1	0.5	0.5	0.5
Expected dividend yield	—%	—%	—%	—%	—%	—%

Schedule of Share-Based Payment Award, Employee Stock Purchase Plan, Valuation Assumptions

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:

	Options			ESPP
	Year Ended December 31,			Year Ended December 31,
	2022	2021	2020	2022	2021	2020
Risk-free interest rate	1.5% - 4.2%	0.5% - 1.3%	0.3% - 1.5%	2.2% - 4.7%	0.1%	0.1% - 0.2%
Expected volatility	85%	86% - 88%	88% - 92%	78% - 79%	69% - 75%	75% - 96%
Expected term (in years)	5.5 - 6.1	5.5 - 6.1	5.4 - 6.1	0.5	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):

	Year Ended December 31,
	2022		2021		2020
Research and development expense	$	15,222	$	9,228	$	1,895
General and administrative expense	11,917		7,828		2,415
Total stock-based compensation expense	$	27,139	$	17,056	$	4,310