Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2023

Summary of Unvested Shares

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

Balance at December 31, 2022	254,437
Share vesting	(222,593	)
Balance at March 31, 2023	31,844

Summary of Common Stock Reserved for Future Issuance

Common stock reserved for future issuance consists of the following:

	March 31, 2023
Common stock warrants		91,228
Stock options and performance-based awards outstanding		9,046,999
Shares available for issuance under the 2019 Incentive Plan		681,762
Shares available for issuance under the ESPP Plan		1,048,370
Balance at December 31, 2023		10,868,359

Summary of PSU Activity Under the 2019 Incentive Award Plan

The following table summarizes PSU activity under the 2019 Incentive Award Plan during the three months ended March 31, 2023.

	Number of Stock Units		Weighted- Average Grant Date Fair Value Per Share
Unvested balance at December 31, 2022		412,300	$	30.97
Granted		597,650		10.89
Vested		—		—
Forfeited		—		—
Unvested balance at March 31, 2023		1,009,950	$	19.09

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:

	Three Months Ended March 31,
	2023			2022
Assumptions:
Expected term (in years)		0.49			0.49
Expected volatility		69.10	%		72.41	%
Risk free interest rate		4.77	%		0.37	%
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, 2022		5,586,470		$	23.40		7.90	$	4,476
Options granted		1,043,660			8.38
Options exercised		—			—
Options cancelled		(25,965	)		34.66
Balance at March 31, 2023		6,604,165		$	20.98		8.00	$	170
Options exercisable as of March 31, 2023		3,019,036			23.99		7.19		138

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:

	Three Months Ended March 31,
	2023			2022
Assumptions:
Expected term (in years)		6.08			6.08
Expected volatility		63.77	%		66.19	%
Risk free interest rate		3.46	%		1.70	%
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 March 31,
	2023		2022
Research and development expense	$	1,776	$	1,139
General and administrative expense		5,272		4,636
Total	$	7,048	$	5,775

Restricted Stock Units (RSUs)

Summary of Unvested Shares

The following table summarizes RSU activity under the 2019 Incentive Award Plan during the three months ended March 31, 2023.

	Number of Stock Units			Weighted- Average Grant Date Fair Value Per Share
Unvested balance at December 31, 2022		877,467		$	11.03
Granted		749,760			8.36
Vested		(191,526	)		11.36
Forfeited		(2,817	)		10.26
Unvested balance at March 31, 2023		1,432,884		$	9.59