Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share Based Compensation Arrangement By Share Based Payment Award [Line Items]

Summary of Stock Option Activity

The following table summarizes stock option activity for all of our plans during 2022:

	2017 Plan			2019 Inducement Plan			Total Number of Stock Options
Outstanding as of December 31, 2021		3,893,605			997,111			4,890,716
Granted		956,604			—			956,604
Exercised		(56,120	)		—			(56,120	)
Forfeited or cancelled		(1,161,257	)		(650,844	)		(1,812,101	)
Outstanding as of December 31, 2022		3,632,832			346,267			3,979,099

The following table summarizes details regarding stock options granted under our equity incentive plans for the year ended December 31, 2022:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2021		4,890,716		$	11.75		7.62	$	24,263
Granted		956,604			11.12
Exercised		(56,120	)		7.48
Forfeited or cancelled		(1,812,101	)		13.21
Outstanding as of December 31, 2022		3,979,099		$	10.99		5.27	$	1
Outstanding as of December 31, 2022 - vested and expected to vest		3,979,099		$	10.99		5.27	$	1
Exercisable at December 31, 2022		2,688,861		$	9.76		4.58	$	—

Summary of Activity of Options and RSUs of Performance-Based Options

The following table summarizes RSU activity under all equity plans (excluding performance-based RSUs) during the year months ended December 31, 2022:

	Number of RSU Shares			Weighted Average Grant Date Fair Value
Outstanding as of December 31, 2021		513,690		$	17.08
Granted		1,420,750			5.88
Vested and released		(226,043	)		7.00
Forfeited or cancelled		(408,000	)		14.16
Outstanding as of December 31, 2022		1,300,397		$	7.51

Summary of Assumptions Used to Determine Fair Value of Stock Option Awards Granted to Employees and Directors

The assumptions that the Company used in the Black-Scholes option-pricing model to determine the fair value of stock option awards granted to employees and directors were as follows, presented on a weighted average basis:

	Year Ended December 31,
	2022			2021
Risk-free interest rate		1.7	%		0.8	%
Expected term (in years)		6.2			6.2
Expected volatility		82.7	%		92.6	%
Expected dividend yield		0.0	%		0.0	%

Summary of Share-Based Compensation Expense

The Company recorded share-based compensation expense, for both RSUs and stock options in the following expense categories of its consolidated statements of operations and comprehensive loss (in thousands):

	Year Ended December 31,
	2022		2021
Research and development expenses	$	3,678	$	4,163
General and administrative expenses		5,445		5,267
Total	$	9,123	$	9,430