Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2022

Schedule of Restricted Stock Units Activity

The Company’s RSU activity for the nine months ended September 30, 2022 was as follows:

				Weighted
				Average
				Grant Date
	Number			Fair Value
	of Shares			per Share
Nonvested at December 31, 2021		1,886,765		$	6.52
Restricted units granted		—			—
Vested		(628,921	)		6.52
Cancelled or forfeited		—			—
Nonvested at September 30, 2022		1,257,844		$	6.52

Schedule of Restricted Stock Awards Activity

The Company’s RSA activity for the nine months ended September 30, 2022 was as follows:

				Weighted
				Average
				Grant Date
	Number			Fair Value
	of Shares			per Share
Nonvested at December 31, 2021		341,975		$	5.28
Restricted stock granted		—			—
Vested		(192,361	)		5.28
Nonvested at September 30, 2022		149,614		$	5.28

Schedule of Total Stock-Based Compensation Expense for Stock Options, ESPP, RSAs and RSUs

During the nine months ended September 30, 2022, $0.2 million of stock-based compensation expense was capitalized as part of construction in process (see Note 3). The following table summarizes the total stock-based compensation expense for the stock options, ESPP, RSAs and RSUs recorded in the condensed consolidated statements of operations, net of the amounts capitalized, for the three and nine months ended September 30, 2022 and 2021 (in thousands):

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development expense	$	2,001	$	2,305	$	5,894	$	6,098
General and administrative expense		2,469		2,781		8,046		7,131
Total	$	4,470	$	5,086	$	13,940	$	13,229

Stock Options

Schedule of Assumptions Used to Estimate Fair Value of Stock Options and Cancelled Options

The following weighted-average assumptions were used to estimate the fair value of stock options that were granted during the three and nine months ended September 30, 2022 and 2021:

	Three Months Ended September 30,					Nine Months Ended September 30,
	2022		2021			2022			2021
Risk-free interest rate		—		1.02	%		2.16	%		0.83	%
Expected dividend yield		—		—			—			—
Expected term in years		—		6.1			6.1			6.0
Expected volatility		—		75	%		76	%		75	%

Schedule of Stock Option Activity

The following table summarizes stock option activity, during the nine months ended September 30, 2022:

						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Stock			Exercise		Contractual		Value
	Options			Price		Life (in years)		(in thousands)
Outstanding at December 31, 2021		3,649,962		$	24.13		9.2	$	—
Options granted		2,679,952			6.24		—	$	—
Options cancelled or forfeited		(1,684,140	)		15.38		—	$	—
Options expired		(98,041	)		24.72		—	$	—
Outstanding at September 30, 2022		4,547,733		$	16.82		8.6	$	—
Vested and expected to vest at September 30, 2022		4,547,733		$	16.82		8.6	$	—
Options exercisable at September 30, 2022		1,199,900		$	24.86		7.5	$	—