Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2022

Summary of Unvested Shares

A summary of the Company’s unvested shares is as follows:

Balance at December 31, 2021	1,144,809
Share vesting	(890,372	)
Balance at December 31, 2022	254,437

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following:

	December 31, 2022
Common stock warrants		91,228
Stock options and performance-based awards outstanding		6,876,237
Shares available for issuance under the 2019 Incentive Plan		957,885
Shares available for issuance under the ESPP Plan		752,938
Balance at December 31, 2022		8,678,288

Summary of PSU Activity Under the 2019 Incentive Award Plan

The following table summarizes PSU activity under the 2019 Incentive Award Plan during the year ended December 31, 2022.

	Number of Stock Units			Weighted- Average Grant Date Fair Value Per Share
Unvested balance at December 31, 2021		394,300		$	32.23
Granted		37,500			20.06
Vested		—			—
Forfeited		(19,500	)		35.39
Unvested balance at December 31, 2022		412,300		$	30.97

Summary of Weighted-Average Assumptions Used to Estimate Fair Value of 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:

	Years Ended December 31,
	2022			2021
Assumptions:
Expected term (in years)		0.50			0.69
Expected volatility		68.59	%		76.25	%
Risk free interest rate		2.04	%		0.09	%
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 December 31, 2021		4,186,729		$	27.53		7.91	$	13,973
Options granted		1,741,931			14.62
Options exercised		—			—
Options cancelled		(342,190	)		29.32
Balance at December 31, 2022		5,586,470		$	23.40		7.90	$	4,476
Options exercisable as of December 31, 2022		2,455,735			25.00		7.18		2,867

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:

	Years Ended December 31,
	2022			2021
Assumptions:
Expected term (in years)		5.88			5.93
Expected volatility		66.00	%		67.46	%
Risk free interest rate		2.06	%		0.68	%
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 as follows (in thousands):

	Years Ended December 31,
	2022		2021
Research and development expense	$	5,534	$	3,838
General and administrative expense		18,599		12,974
Total	$	24,133	$	16,812

Restricted Stock Units (RSUs)

Summary of Unvested Shares

During 2022, the Company granted 1,010,437 RSUs with vesting over time. The following table summarizes RSU activity under the 2019 Incentive Award Plan during the year ended December 31, 2022.

	Number of Stock Units			Weighted- Average Grant Date Fair Value Per Share
Unvested balance at December 31, 2021		-		$	-
Granted		1,010,437			10.79
Vested		(102,453	)		8.51
Forfeited		(30,517	)		12.14
Unvested balance at December 31, 2022		877,467		$	11.03