Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense recorded related to awards granted to employees and non-employees was as follows (in thousands):

	Year Ended December 31,
	2023		2022		2021
Research and development	$	10,826	$	6,050	$	3,492
General and administrative		7,663		5,579		4,745
Total stock-based compensation expense	$	18,489	$	11,629	$	8,237

Summary of Activity under Plans

Activity under the Company’s 2015 and 2019 Plans and 2023 Inducement Plan is set forth below:

	Outstanding Options
	Shares			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value (in thousands)
Balance, January 1, 2023		5,097,263		$	12.93		7.84	$	29.58
Options granted		2,694,871		$	18.95
Options exercised		(931,012	)	$	10.27
Options canceled		(591,147	)	$	16.93
Balance, December 31, 2023		6,269,975		$	15.53		7.82	$	128.49
Exercisable as of December 31, 2023		2,612,605		$	12.21		6.39	$	62.22
Vested and expected to vest as of    December 31, 2023		6,269,975		$	15.53		7.82	$	128.49

Assumptions Used to Calculate Fair Values of Options

The fair values of options were calculated using the assumptions set forth below:

	Year Ended December 31,
	2023	2022	2021
Expected term	6.1 years	6.1 years	5.5 - 6.1 years
Expected volatility	81.76% - 86.90%	86.76% - 89.88%	90.0% - 103.6%
Risk-free interest rate	3.56% - 4.83%	1.62% - 4.05%	0.6% - 1.4%
Dividend yield	0%	0%	0%