Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

Summary of Restricted Stock Units (RSU)

The Company has granted restricted stock unit (RSU) awards under the 2020 Equity Incentive Award Plan that vest over a period of four years. The following table summarizes the RSU activity for the six months ended June 30, 2024:

	Number of Shares
Unvested balance at December 31, 2023		181,181
Issued		129,650
Vested		(21,963	)
Canceled/Forfeited		(30,751	)
Unvested balance at June 30, 2024		258,117

Summary of Stock Options Activity

The following table summarizes the stock options activity for the six months ended June 30, 2024:

	Number of Shares Underlying Outstanding Options
Balances at December 31, 2023		8,240,154
Options granted		434,500
Options exercised		(296,183	)
Options expired		(8,837	)
Options forfeited		(177,461	)
Balances at June 30, 2024		8,192,173
Options exercisable at June 30, 2024		3,726,662
Options vested and expected to vest at June 30, 2024		8,192,173

Summary of Assumptions Used in Black-Scholes Valuation Model to Estimate Fair Value of Stock Options

The Company estimates the fair value of stock options using the Black-Scholes option pricing model. The fair value of employee and nonemployee options is recognized on a straight-line basis over the requisite service period of the awards. The fair value of the Company’s stock options was estimated using the following assumptions for the three and six months ended June 30, 2024 and 2023:

	Three Months Ended June 30,		Six Months Ended June 30,
	2024	2023	2024	2023
Expected term	6.0 - 6.1 years	6.0 - 6.1 years	6.0 - 6.1 years	6.0 - 6.1 years
Expected volatility	84.9% - 85.4%	81.1% - 82.2%	81.4% - 85.4%	80.9% - 84.4%
Risk-free interest rate	4.4% - 4.5%	3.5% - 4.0%	3.9% - 4.5%	3.5% - 4.0%
Expected dividend yield	—%	—%	—%	—%

Summary of Stock-based Compensation Expense for Employees and Nonemployees by Function

The following table is a summary of stock-based compensation expense incurred for employees and nonemployees by function (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	3,196	$	2,678	$	6,231	$	5,148
General and administrative		2,877		2,291		5,817		4,042
Total stock-based compensation expense	$	6,073	$	4,969	$	12,048	$	9,190