Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2024

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following:

	June 30, 2024
Common stock warrants		91,228
Stock options and restricted stock units outstanding		9,454,109
Shares available for issuance under the 2019 Incentive Plan		1,341,277
Shares available for issuance under the ESPP Plan		1,433,220
Balance at June 30, 2024		12,319,834

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:

	Six Months Ended June 30,
	2024	2023
Assumptions:
Expected term (in years)	0.49	0.49
Expected volatility	119.08%	69.10%
Risk free interest rate	5.16%	4.77%
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		2,224,400			8.07
Options exercised		(2,432	)		8.67
Options cancelled		(227,517	)		12.96
Balance at June 30, 2024		6,544,532		$	10.46		7.74	$	10,790
Options exercisable as of June 30, 2024		2,868,583		$	12.06		6.03	$	3,978
Vested and expected to vest as of June 30, 2024		6,544,532		$	10.46		7.74	$	10,790

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:

	Six Months Ended June 30,
	2024	2023
Assumptions:
Expected term (in years)	6.04	6.03
Expected volatility	74.67%	64.02%
Risk free interest rate	4.14%	3.48%
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 June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development expense	$	1,331	$	1,803	$	2,580	$	3,580
Selling, general and administrative expense		4,768		5,450		9,145		10,721
Total	$	6,099	$	7,253	$	11,725	$	14,301

Restricted Stock Units (RSUs)

Summary of Unvested Shares

The following table summarizes RSU activity under the 2019 Plan during the six months ended June 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		824,312			7.92
Vested		(415,034	)		10.61
Forfeited		(153,593	)		12.12
Unvested balance at June 30, 2024		2,909,577		$	10.95