The Company adopted the 2016 Equity Incentive Plan, as amended (the “2016 Plan”) on March 31, 2016. The 2016 Plan provided for the granting of stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock awards to employees, directors and non-employees. All option awards were granted with an exercise price equal to or greater than the market price of the Company’s stock at the date of grant. Option awards generally vest over three to four years. Certain option awards provide for accelerated vesting if there is a change in control as defined in the 2016 Plan. The provisions of the 2016 Plan allow for early exercises for options that have not yet vested. Early exercises have historically been for a de minimis number of shares.

On September 23, 2020, the Company adopted the 2020 Equity Incentive Plan (the “2020 Plan”), which became effective on October 1, 2020 and serves as the successor to the 2016 Plan. The 2020 Plan authorizes the award of stock options, restricted stock awards, stock appreciation rights, restricted stock units, cash awards, performance awards and stock bonus awards. The number of shares reserved for issuance under the 2020 Plan increases automatically on January 1 of each fiscal year, through and including January 1, 2030, by the number of shares equal to 5% of the aggregate number of outstanding shares of common stock as of the immediately preceding December 31, or a lesser number of shares as may be determined by the board of directors (or an authorized committee thereof). On January 1, 2023, the number of shares reserved for issuance under the 2020 Plan increased by 1,298,656 shares of common stock.

At March 31, 2023, there were 2,512,467 shares of common stock available for issuance under the 2020 Plan.

On September 23, 2020, the Company adopted the 2020 Employee Stock Purchase Plan (the "ESPP"), which became effective on October 1, 2020. The Company initially reserved 280,000 shares of common stock for sale under the ESPP. The aggregate number of shares reserved for sale under the ESPP increases automatically on January 1st of each fiscal year through and including January 1, 2030, by the number of shares equal to the lesser of (a) 1% of the total number of shares of common stock outstanding on the last day of the fiscal year prior to the date of such automatic increase and (b) 560,000 shares, provided that prior to the date of any such increase, the board of directors may determine a lesser number of shares for such increase. On January 1, 2023, the the number of shares reserved for issuance under the ESPP increased by 259,731 shares of common stock. The ESPP provides for six-month offering periods commencing on January 1 and ending on June 30 and commencing on July 1 and ending on December 31 of each calendar year. The Company began its first offering period on January 1, 2022, and issued 89,112 shares of common stock on June 30, 2022 at the end of the first offering period. The Company commenced its second offering period on July 1, 2022, and issued 122,228 shares of common stock on December 31, 2022 at the end of the second offering period. The Company commenced an offering period on January 1, 2023 that is scheduled to end on June 30, 2023.

Total stock-based compensation was classified as follows on the unaudited interim condensed consolidated statements of operations (in thousands):


	THREE MONTHS ENDED MARCH 31,
	2023		2022

General and administrative	$	901	$	1,262
Research and development		566		718
Total stock-based compensation	$	1,467	$	1,980

In December 2020, the Company granted an employee an option to purchase 113,000 shares of the Company’s common stock with an exercise price per share equal to the fair value of the Company’s common stock on the date of grant. This grant is included in the outstanding options in the summary table below. The option grant includes three separate tranches (each tranche representing one-third of the total grant) that will each vest four years from the date of grant. This option grant and its tranches are subject to accelerated vesting in the event that the Company achieves certain defined milestones related to the Company’s manufacturing efforts. The Company recognized stock-based compensation expense of $0.2 million related to this grant in the three months ended March 31, 2023.

A summary of option activity for the three months ended March 31, 2023 is presented below:


	SHARES			WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED- AVERAGE REMAINING CONTRACTUAL TERM (YEARS)		AGGREGATE INTRINSIC VALUE (IN THOUSANDS)
Outstanding at December 31, 2022		4,391,207		$	7.57
Granted		347,609		$	0.39
Exercised		—			—
Canceled, expired or forfeited		(179,828	)	$	6.53
Outstanding at March 31, 2023		4,558,988		$	7.07		7.85	$	—
Vested and expected to vest at March 31, 2023		4,558,988		$	7.07		7.80	$	—
Exercisable at March 31, 2023		2,225,663		$	7.55		6.88	$	—

The weighted average grant date fair value per share of options granted to employees, directors and non-employee consultants during the three months ended March 31, 2023 and 2022 was $0.39 and $1.54, respectively. There were no options exercised during the three months ended March 31, 2023. The total intrinsic value of options exercised was $0.0 million for the three months ended March 31, 2023. Total unrecognized stock-based compensation expense related to options was $9.2 million at March 31, 2023, and is expected to be recognized over a weighted-average period of 2.4 years.