In September 2018, the Company’s board of directors adopted, and the Company’s stockholders approved, the 2018 Equity Incentive Plan (the “2018 Plan”) which provided for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, performance-based stock awards and other forms of equity compensation to the Company’s employees, directors and consultants. Stock options granted under the 2018 Plan generally vest one-fourth on the first anniversary of the vesting commencement date with the balance vesting monthly over the remaining three years. Restricted stock units granted under the 2018 Plan generally vest one third on the first anniversary of the vesting commencement date and one sixth every six months thereafter such that the award will be fully vested on the third anniversary of the vesting commencement date. As of December 31, 2022, 8,552 shares of common stock were reserved for future issuance pursuant to the 2018 Plan. The number of shares available for issuance under the 2018 Plan also includes an annual increase on the first day of each fiscal year equal to the lesser of (1) 1,305 shares; (2) 5% of the outstanding shares of our common stock as of the last day of the immediately preceding fiscal year; or 3) such other amount as the Company’s board of directors may determine.

In March 2020, the Company adopted the 2020 Inducement Equity Incentive Plan (the “2020 Plan”) for the purpose of attracting, retaining and incentivizing employees in furtherance of the Company’s success. The 2020 Plan was adopted without stockholder approval pursuant to Rule 303A.08 of the New York Stock Exchange. The 2020 Plan is used to offer equity awards as material inducements for new employees to join the Company. Upon adoption of the 2020 Plan, 640 shares of common stock were reserved for the granting of inducement stock options, restricted stock awards, restricted stock units and other forms of equity awards. As of December 31, 2022, 181 shares of common stock were reserved for future issuance under the 2020 Plan.

The following is a summary of stock option activity for the year ended December 31, 2022:

	Stock Options			Weighted Average Exercise Price		Weighted Average Remaining Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2021		2,094		$	17,138
Canceled/forfeited		(1,104	)	$	22,279
Outstanding at December 31, 2022		990		$	11,405		4.14	$	—
Vested and expected to vest at December 31, 2022		990		$	11,405		4.14	$	—
Exercisable at December 31, 2022		849		$	13,077		3.92	$	—

The Company did not grant any stock options during the years ended December 31, 2022 and 2021.

The following is a summary of the restricted stock unit activity for the 2018 Plan for employees of continuing operations and discontinued operations for the year ended December 31, 2022:

	Restricted Stock Units			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2021		1,402		$	258.48
Vested		(117	)	$	892.00
Canceled/forfeited		(1,224	)	$	188.35
Outstanding at December 31, 2022		61		$	450.46

A summary of the restricted stock award activity for the year ended December 31, 2022 is presented below:

	Restricted Stock Awards			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2021		3,586		$	235.03
Vested		(1,660	)	$	241.38
Canceled/forfeited		(978	)	$	211.24
Outstanding at December 31, 2022		948		$	248.48

In September 2018, the Company’s board of directors adopted the 2018 Employee Stock Purchase Plan (the “ESPP”) which permitted eligible employees to purchase the Company’s common stock at a discount through payroll deductions during defined offering periods. Eligible employees could elect to withhold up to 15% of their base earnings to purchase shares of the Company’s common stock at a price equal to 85% of the fair market value on the first day of the offering period or the purchase date, whichever was lower. The number of shares of common stock reserved for issuance under the ESPP automatically increased on January 1 of each fiscal year by the lesser of (1) 237 shares, (2) 1.25% of the total number of shares outstanding on December 31 of the preceding fiscal year, or (3) such other amount as the Company’s board of directors may determine.

For the years ended December 31, 2022 and 2021, cash received from the exercise of purchase rights under the ESPP was approximately $5,000 and $0.1 million, respectively. The Company paused the ESPP in May 2022.

As of December 31, 2022, the Company had issued 950 shares of common stock since inception of the ESPP, and no shares were reserved for future issuance.

Stock-based compensation expense recorded in operating expenses was as follows (in thousands):

	Year Ended December 31,
	2022		2021
Selling, general and administrative	$	387	$	1,750
Research and development		60		304
Stock-based compensation in operating expenses	$	447	$	2,054

Stock-based compensation of approximately $5,000 and $0.1 million was capitalized to property and equipment and inventory during the years ended December 31, 2022 and 2021, respectively.

Total unrecognized estimated stock-based compensation expense by award type and the remaining weighted average recognition period over which such expense is expected to be recognized at December 31, 2022 was as follows:

	December 31, 2022
	Unrecognized Expense (in thousands)		Remaining Weighted Average Recognition Period (in years)
Stock options	$	93		1.2
Restricted stock awards	$	186		1.0
Restricted stock units	$	14		1.0