Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

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 2021:

	2017 Plan			2019 Inducement Plan			Total Number of Stock Options
Outstanding as of December 31, 2020		3,137,233			545,000			3,682,233
Granted		1,161,309			547,400			1,708,709
Exercised		(140,537	)		(20,137	)		(160,674	)
Forfeited or cancelled		(264,400	)		(75,152	)		(339,552	)
Outstanding as of December 31, 2021		3,893,605			997,111			4,890,716

The following table summarizes details regarding stock options granted under our equity incentive plans for the year ended December 31, 2021:

	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
						(in years)		(in thousands)
Outstanding as of December 31, 2020		3,682,233		$	9.10		7.84	$	37,881
Granted		1,708,709			17.62		—		—
Exercised		(160,674	)		9.02		—		—
Forfeited or cancelled		(339,552	)		13.81		—		—
Outstanding as of December 31, 2021		4,890,716		$	11.75		7.62	$	24,263
Outstanding as of December 31, 2021 - vested and expected to vest		4,890,716		$	11.75		7.62	$	24,263
Exercisable at December 31, 2021		2,524,419		$	8.54		6.44	$	18,904

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,
	2021			2020
Risk-free interest rate		0.8	%		1.1	%
Expected term (in years)		6.2			6.2
Expected volatility		92.6	%		82.7	%
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,
	2021		2020
Research and development expenses	$	4,163	$	2,229
General and administrative expenses		5,267		2,659
Total	$	9,430	$	4,888

Performance-based Vesting Criteria [Member]

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

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

The following table summarizes the activity of options and RSUs under the 2017 Plan containing performance-based vesting criteria during the year ended December 31, 2021:

	Number of Performance Based Option Shares			Number of Performance Based RSU Shares
Outstanding as of December 31, 2020		63,107			30,561
Granted		—			—
Exercised		—			—
Forfeited or cancelled		(63,107	)		(30,561	)
Outstanding as of December 31, 2021		—			—