Stock Incentive Plans (Tables)

12 Months Ended

Dec. 31, 2021

Stock Incentive Plans

Summary of stock option activity

				Weighted
				Average
		Weighted-		Remaining	Aggregate
		Average Exercise		Contractual	Intrinsic Value
	Shares	Price		Term (years)	(in thousands)
Outstanding at December 31, 2020	227,846	$	68.25	8.13	$	—
Granted	1,156,646	$	15.91
Assumed in Quellis Acquisition	55,414	$	1.73
Exercised	(10,470)	$	2.10
Cancelled or forfeited	(81,196)	$	48.13
Expired	(1,507)	$	100.85
Outstanding at December 31, 2021	1,346,733	$	22.25	9.02	$	168,181
Vested and exercisable at December 31, 2021	135,412	$	72.76	7.19	$	77,798

Schedule of assumptions made based on the Black-Scholes option pricing model

	Year Ended December 31,
	2021	2020
Weighted-average expected volatility	69.28-71.32%	75.51-82.08%
Expected term (in years)	5-6.25	5.50-6.25
Risk-free interest rate	0.42-1.36%	0.37-1.51%
Expected dividend yield	0%	0%