Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2021

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:

	For the Year Ended December 31,
	2021	2020
Expected volatility	64.6% - 71.7%	63.2% — 66.3%
Weighted-average risk-free interest rate	0.50% - 1.33%	0.31% — 1.73%
Expected dividend yield	— %	— %
Expected term (in years)	5.5 - 6.25	5.5 - 6.25
Underlying common stock fair value	$4.85 - $13.91	$9.82 - $21.75

Summary of Option Activity under Plans

A summary of option activity under the Plans during the year ended December 31, 2021 is as follows:

	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, 2021		5,840,824		$	15.18		7.8	$	12,278
Granted		2,202,325		$	11.97
Exercised		(59,465	)	$	2.29
Cancelled/Forfeited		(359,378	)	$	17.50
Outstanding at December 31, 2021		7,624,306		$	14.25		7.5	$	2,069
Vested and expected to vest at    December 31, 2021		7,624,306		$	14.25		7.5	$	2,069
Exercisable at December 31, 2021		4,434,630		$	13.66		6.7	$	2,069

Summary of Unvested Common Stock from Early Exercises Subject to Repurchase

A summary of the Company’s unvested common stock from early exercises that is subject to repurchase by the Company is as follows:

	Shares
Unvested shares—January 1, 2021		3,091
Vested		(3,091	)
Unvested shares—December 31, 2021		—

Summary of Company's RSU Activity

The following table summarizes the Company's RSU activity for the year ended December 31, 2021:

	Number of			Weighted-
	Restricted			Average Grant
	Stock Units			Date Fair Value
Outstanding at January 1, 2021		—		$	—
Granted		321,300		$	12.79
Vested		—		$	—
Forfeited		(13,700	)	$	13.63
Outstanding at December 31, 2021		307,600		$	12.75

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:

	For the Year Ended December 31,
	2021		2020
	(in thousands)
Research and development	$	8,795	$	6,390
General and administrative		8,450		6,858
	$	17,245	$	13,248