Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2024

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following:

	September 30, 2024
Common stock warrants including pre-funded warrants		2,700,150
Stock options and restricted stock units outstanding		8,957,196
Shares available for issuance under the 2019 Incentive Plan		1,356,384
Shares available for issuance under the ESPP Plan		1,177,618
Balance at September 30, 2024		14,191,348

Summary of Weighted-Average Assumptions Used to Estimate Fair Value of Stock Options Granted and ESPP Awards

The weighted-average assumptions used to estimate the fair value of ESPP awards using the Black-Scholes option valuation model were as follows:

	Nine Months Ended September 30,
	2024	2023
Assumptions:
Expected term (in years)	0.49	0.49
Expected volatility	105.23%	69.73%
Risk free interest rate	5.19%	5.03%
Dividend yield	—	—

Summary of Stock Option Activity

A summary of the Company’s stock option activity and related information is as follows:

	Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term		Aggregate Intrinsic Value (in thousands)
Balance at January 1, 2024		4,550,081		$	11.75		7.50	$	3,379
Options granted		2,242,400			8.11
Options exercised		(30,235	)		10.01
Options cancelled		(313,412	)		13.72
Balance at September 30, 2024		6,448,834		$	10.40		7.52	$	51,605
Options exercisable as of September 30, 2024		2,975,481		$	11.91		5.93	$	20,402
Vested and expected to vest as of September 30, 2024		6,448,834		$	10.40		7.52	$	51,605

Summary of Weighted-Average Assumptions Used to Estimate Fair Value of Stock Options

The weighted-average assumptions used to estimate the fair value of stock options using the Black-Scholes option valuation model were as follows:

	Nine Months Ended September 30,
	2024	2023
Assumptions:
Expected term (in years)	6.04	6.03
Expected volatility	74.67%	64.10%
Risk free interest rate	4.14%	3.50%
Dividend yield	—	—

Summary of Stock-Based Compensation Expense

Stock-based compensation expense recognized for all equity awards, including founder stock, has been reported in the statements of operations and comprehensive loss as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Research and development expense	$	1,296	$	1,397	$	3,876	$	4,977
Selling, general and administrative expense		4,339		4,743		13,484		15,464
Total	$	5,635	$	6,140	$	17,360	$	20,441

Restricted Stock Units (RSUs)

Summary of Unvested Shares

The following table summarizes RSU activity under the 2019 Plan during the nine months ended September 30, 2024:

	Number of Stock Units			Weighted- Average Grant Date Fair Value Per Share
Unvested balance at January 1, 2024		2,653,892		$	11.91
Granted		901,737			8.48
Vested		(869,037	)		13.18
Forfeited		(178,230	)		11.73
Unvested balance at September 30, 2024		2,508,362		$	10.25