In March 2017, the Company's stockholders approved the 2017 Stock Option and Grant Plan, pursuant to which stock options, restricted stock awards, unrestricted stock awards, restricted stock units (RSUs), or any combination of the forgoing could be issued to eligible employees, officers, directors, consultants, or other key persons who provide services to the Company.

The 2021 Stock Option and Incentive Plan (the 2021 Plan) became effective upon the closing of the Business Combination and replaced the 2017 Stock Option and Grant Plan. The 2021 Plan allows the Company to issue stock options, stock appreciation awards, restricted stock awards, unrestricted stock awards, restricted stock units (RSUs) and cash-based awards, or any combination of the forgoing to eligible employees, officers, directors, or consultants. As of March 31, 2023, the Company had 6,662,594 shares available for future issuance under the 2021 Plan.

The 2023 Inducement Plan (the Inducement Plan) became effective upon approval of the Company's board of directors in February 2023. The Inducement Plan allows the Company to make equity and equity-based incentive awards to individuals who were not previously employees or directors of the Company. As of March 31, 2023, the Company had 2,256,250 shares available for future issuance under the Inducement Plan.

The Company recorded stock-based compensation expense in the following expense categories in its accompanying condensed consolidated statements of operations:


	Three Months Ended March 31,
	2023		2022
	(in thousands)
Research and development	$	2,135	$	1,642
General and administrative		2,084		1,563
Total	$	4,219	$	3,205

The following table summarizes the stock option activity for the three months ended March 31, 2023:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Contractual Term		Aggregate Intrinsic Value
	(in years)
Options outstanding as of December 31, 2022		12,924,086		$	6.50		8.13	$	24,267,448
Granted		4,257,952			5.37
Exercised		(30,590	)		2.37
Cancelled		(133,208	)		9.65
Options outstanding as of March 31, 2023		17,018,240		$	6.20		8.37	$	6,441,051
Options exercisable as of March 31, 2023		6,042,026		$	5.32		7.26	$	5,253,390

As of March 31, 2023, total unrecognized compensation expense related to stock options was $48.0 million, which the Company expects to recognize over a remaining weighted-average period of 2.9 years.

The following table summarizes the RSU activity for the three months ended March 31, 2023:


	Number of Stock Units			Weighted Average Grant Date Fair Value Per Share
Unvested and outstanding as of December 31, 2022		—		$	-
Granted		637,138			5.20
Vested		—			—
Forfeited		(3,512	)		5.20
Unvested and outstanding as of March 31, 2023		633,626		$	5.20

As of March 31, 2023, total unrecognized compensation expense related to RSUs was $3.2 million, which the Company expects to recognize over a remaining weighted-average period of 2.8 years.

The 2021 Employee Stock Purchase Plan (the 2021 ESPP) was adopted and approved by the Company’s board of directors and by the Company’s stockholders and became effective upon the closing of the Business Combination. During the three months ended March 31, 2023, the Company issued zero shares of common stock under the 2021 ESPP.