Stock-Based Compensation

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Stock-Based Compensation

11. Stock-Based Compensation

Stock Incentive Plans

On March 12, 2018, the Company’s Board of Directors (the “Board”) adopted the 2018 Equity Incentive Plan (the “2018 Plan”). The 2018 Plan became effective on April 20, 2018 upon approval by the stockholders of the Company with the outstanding options and shares available for future grant under any prior plans being assumed by the 2018 Plan. The initial total number of shares available under the 2018 Plan for awards to employees, non-employee directors and other key personnel was 125,000 shares.

Stock options granted have a ten-year contractual life and, upon termination of service, vested options are generally exercisable between one and three months following the termination date, while unvested options are forfeited immediately.

Summary of Stock Option Activity

Transactions during the year ended December 31, 2022 related to stock options granted to employees and directors were as follows:

	Shares			Weighted average exercise price per Share		Weighted average remaining contractual life (years)		Aggregate intrinsic value (in thousands)
Options outstanding as of December 31, 2021		222,611		$	209.60		7.23	$	254
Granted		86,112			17.88
Exercised		-			-
Forfeited		(59,320	)		367.39
Options outstanding as of December 31, 2022		249,403		$	105.87		8.12	$	3
Options exercisable at December 31, 2022		81,809		$	214.06		6.39	$	3

As of December 31, 2022, the unrecognized compensation cost related to the outstanding options was $5.3 million and is expected to be recognized over a weighted-average period of 2.43 years.

The weighted average grant date fair values of stock options granted during the years ended December 31, 2022 and 2021 were $12.20 and $62.40, respectively.

The following table presents the assumptions used to estimate the fair values of stock options granted in the periods presented:

	Year ended December 31,
	2022	2021
Dividend yield	0%	0%
Volatility	78%-82%	76%-77%
Risk-free interest rate	1.84%-3.96%	0.87%-1.33%
Expected term (years)	5.5-6.0		6.0
Contractual term (years)	10	10

Summary of Restricted Stock Unit Activity

Transactions during the year ended December 31, 2022 related to RSUs granted to employees were as follows:

	Shares			Weighted average grant date fair value per share
Unvested at December 31, 2021		157		$	600.80
Vested		(157	)		600.80
Unvested at December 31, 2022		-		$	-

As of December 31, 2022, there was no remaining unrecognized compensation costs related to the RSUs.

Stock-based Compensation Expense

Stock-based compensation expense relates to stock options granted to employees, non-employee directors and consultants, time-based restricted stock units granted to employees and performance-based stock options and restricted stock units granted to an employee. The total equity-based compensation expense related to all of the Company’s equity-based awards was recognized as follows (in thousands):

	Year ended December 31,
	2022		2021
Research and development	$	1,319	$	1,336
General and administrative		1,702		7,831
Total stock-based compensation expense	$	3,021	$	9,167