Stock Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2023

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Options Valuation Assumptions Using a Black-Scholes Option Pricing Model

The assumptions used in the Black-Scholes option pricing model are as follows:

	Three months ended March 31,
	2023	2022
Expected volatility	69.6% - 69.7%	68.7% - 69.5%
Weighted-average risk-free interest rate	4.06% - 4.22%	1.46% - 1.89%
Expected dividend yield	— %	— %
Expected term (in years)	6.25	6.00 - 6.25
Underlying common stock fair value	$1.58-$1.60	$2.71-$4.17

Summary of Option Activity under Plans

The following table summarizes the Company’s stock option activity for the three months ended March 31, 2023:

	Number of Options			Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value
								(in thousands)
Outstanding at January 1, 2023		9,865,734		$	10.96		7.2	$	493
Granted		2,843,950		$	1.60
Exercised		—		$	—
Cancelled/Forfeited		(105,393	)	$	7.19
Outstanding at March 31, 2023		12,604,291		$	8.88		7.6	$	346
Vested and expected to vest at    March 31, 2023		12,604,291		$	8.88		7.6	$	346
Exercisable at March 31, 2023		6,645,290		$	12.82		6.2	$	346

Summary of Company's RSU Activity

The following table summarizes the Company's RSU activity for the three months ended March 31, 2023:

	Number of Restricted Stock Units			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2023		543,179		$	6.12
Granted		483,850		$	1.60
Vested		(194,525	)	$	7.25
Forfeited		(9,958	)	$	5.52
Outstanding at March 31, 2023		822,546		$	3.20

Schedule of Stock-Based Compensation Expense

The Company recorded stock-based compensation expense related to stock options, shares purchased under the 2018 ESPP and restricted stock units as follows:

	Three months ended March 31,
	2023		2022
	(in thousands)
Research and development	$	649	$	2,166
General and administrative		1,720		1,885
	$	2,369	$	4,051