Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Summary of Share-based Compensation Expense

Share-based compensation expense was as follows for the years ended December 31, (in thousands):

	2022		2021
Research and development	$	3,650	$	9,001
General and administrative		2,603		2,855
Total share-based compensation expense	$	6,253	$	11,856

Summary of Options Granted by the Company's Board of Directors

The following tables summarizes option activity for the periods presented:

	Total Options			Weighted- Average Exercise Price		Aggregate Intrinsic Value (in thousands)		Weighted-Average Remaining Contractual Life (in years)
Outstanding as of December 31, 2021		34,200,976		$	1.43	$	912	8.1
Granted		17,058,623		$	0.45
Canceled		(12,143,425	)	$	1.08
Outstanding as of December 31, 2022		39,116,174		$	1.11	$	1,088	5.4
Vested and exercisable as of    December 31, 2022		22,083,111		$	1.34	$	—	4.6

Employee Stock Option | Employee Share Purchase Plan [Member]

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Summary Of Share Based Payment Award Stock Options Valuation Assumptions

The weighted-average fair value of options and ESPP (as defined below) awards issued was estimated at the date of grant using the BSM with the following weighted-average assumptions for the years ended December 31:

	Options						ESPP
	2022			2021			2022			2021
Expected term (in years)		6.0			6.0			1.2			1.3
Risk-free interest rate		2.9	%		1.0	%		2.8	%		0.2	%
Expected volatility		82.0	%		80.5	%		79.2	%		74.6	%
Dividend yield		—			—			—			—
Weighted-average grant date fair value	$	0.31		$	1.20		$	0.22		$	0.78