Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2023

Stock-Based Compensation

Schedule of stock-based compensation expense attributable to share-based payments made to employees and directors and included in operating expenses

	Three Months Ended
	March 31,
(in thousands)	2023		2022
Stock-based compensation:
Research and development
Employee Stock Purchase Plan	$	—	$	6
Equity Incentive Plans		500		89
	$	500	$	95
General and administrative
Employee Stock Purchase Plan	$	—	$	2
Equity Incentive Plans		731		448
	$	731	$	450
Total stock-based compensation expense	$	1,231	$	545

Schedule of weighted average assumptions applied to options

	2023		2022
Average risk-free interest rate		3.9%		1.3%
Expected dividend yield		—		—
Expected lives (years)		3.1		3.8
Expected volatility		106%		105%
Weighted average exercise price (per share)	$	5.21	$	10.20

Schedule of information related to outstanding and exercisable options

	Common Stock Options
($ in thousands, except per share data)	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2022	406,174	$	83.00	6.1	$	102
Granted	321,900		5.21
Conversion of preferred stock options to common stock options	994,399		6.91
Exercised	(3,458)		2.21
Forfeited	(43,565)		7.94
Expired	(17,397)		2.21
Outstanding at March 31, 2023 (1)	1,658,053	$	25.26	8.2	$	20
Exercisable at March 31, 2023	593,192	$	57.65	6.5	$	10

	Preferred Stock Options
($ in thousands, except per share data)	Number of Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2022	17,522	$	397.02	9.1	$	1,073
Exercised	(617)		130.00
Conversion of preferred stock options to common stock options	(16,905)		406.76
Outstanding at March 31, 2023 (1)	—	$	—	—	$	—
Exercisable at March 31, 2023	—	$	—	—	$	—

(1) Includes both vested stock options as well as unvested stock options for which the requisite service period has not been rendered but that are expected to vest based on achievement of a service condition.

Schedule of information related to restricted stock activity

	Time-based Awards			Market/Performance-based Awards
	Number of Shares	Weighted-Average Grant Date Fair Value		Number of Shares	Weighted-Average Grant Date Fair Value
Nonvested shares at December 31, 2022	19,096	$	10.73	29,814	$	26.14
Granted	—		—	—		—
Cancelled	(294)		—	(6,030)		—
Vested	(1,601)		—	(14,538)		—
Nonvested shares at March 31, 2023	17,201	$	7.54	9,246	$	26.14

Schedule of summary of restricted stock activity

	Number of Shares
	Common Stock	Series Z
Nonvested shares at December 31, 2022	15,432	2,756
Granted	—	—
Conversion of preferred stock RSAs to common stock RSAs	75,471	(1,283)
Cancelled	(7,962)	(1,426)
Vested	(6,386)	(47)
Nonvested shares at March 31, 2023	76,555	—