Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Schedule of Share Based Compensation Available for Grant under Incentive Plans

The number of shares available for grant under the Company’s incentive plans were as follows:

	Existing			New
	Plan			Plan			Total
Available for grant - December 31, 2022		—			1,067,682			1,067,682
Plan adjustments and amendments		(667,828	)		3,828,203			3,160,375
Grants		—			(5,241,357	)		(5,241,357	)
Forfeitures		667,828			2,918,614			3,586,442
Available for grant - September 30, 2023		—			2,573,142			2,573,142

Schedule of Restricted Stock Units Activity

The Company’s RSU activity for the nine months ended September 30, 2023 was as follows:

				Weighted
				Average
				Grant Date
	Number			Fair Value
	of Shares			per Share
Nonvested at December 31, 2022		1,257,844		$	6.52
Restricted units granted		332,532			1.06
Vested		(556,989	)		4.78
Cancelled or forfeited		(658,343	)		5.18
Nonvested at September 30, 2023		375,044		$	6.63

As of September 30, 2023, the total unrecognized compensation related to unvested RSUs granted was $2.0 million which is expected to be amortized on a straight-line basis over a weighted-average period of approximately 0.9 years.

Schedule of Restricted Stock Awards Activity

The Company’s RSA activity for the nine months ended September 30, 2023 was as follows:

				Weighted
				Average
				Grant Date
	Number			Fair Value
	of Shares			per Share
Nonvested at December 31, 2022		85,494		$	5.28
Restricted stock granted		—			—
Vested		(64,120	)		5.28
Cancelled or forfeited		(21,374	)		5.28
Nonvested at September 30, 2023		—		$	—

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

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 for the three and nine months ended September 30, 2023 and 2022 (in thousands):

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development expense	$	705	$	2,001	$	1,524	$	5,894
General and administrative expense		1,335		2,469		4,413		8,046
Total	$	2,040	$	4,470	$	5,937	$	13,940

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 time-based vesting stock options that were granted during the three and nine months ended September 30, 2023 and 2022:

	Three Months Ended September 30,					Nine Months Ended September 30,
	2023			2022		2023			2022
Risk-free interest rate		4.22	%		—		3.61	%		2.16	%
Expected dividend yield		—			—		—			—
Expected term (in years)		5.5			—		5.5			6.1
Expected volatility		81	%		—		81	%		76	%

Schedule of Stock Option Activity

The following table summarizes time-based vesting stock option activity, during the nine months ended September 30, 2023:

						Weighted
				Weighted		Average		Aggregate
				Average		Remaining		Intrinsic
	Stock			Exercise		Contractual		Value
	Options			Price		Life (in years)		(in thousands)
Outstanding at December 31, 2022		6,158,078		$	11.84		8.9	$	62
Options granted		2,520,471			0.90
Options cancelled or forfeited		(2,013,500	)		10.88
Options expired		(857,557	)		22.26
Outstanding at September 30, 2023		5,807,492		$	5.89		8.9	$	6,851
Options exercisable at September 30, 2023		1,036,300		$	18.48		7.5	$	49

Performance Stock Options

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

The following assumptions were used to estimate the fair value of performance and service-based stock options that were granted during the nine months ended September 30, 2023:

	For the nine months ended September 30, 2023
Risk-free interest rate		4.02	%
Expected dividend yield		—
Expected term (in years)		6.0
Expected volatility		81	%