Stock-Based Compensation

9 Months Ended

Sep. 30, 2023

Share-Based Payment Arrangement [Abstract]

Stock Incentive Plan

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 September 30, 2023, the Company had 6,200,500 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 September 30, 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 September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
	(in thousands)				(in thousands)
Research and development	$	2,573	$	1,791	$	7,516	$	5,089
General and administrative		2,287		2,024		6,684		5,356
Total	$	4,860	$	3,815	$	14,200	$	10,445

Stock Option Activity

The following table summarizes the stock option activity for the nine months ended September 30, 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		5,113,352			5.19
Exercised		(246,848	)		2.26
Cancelled		(695,585	)		8.01
Options outstanding as of September 30, 2023		17,095,005		$	6.12		7.83	$	87,902,516
Options exercisable as of September 30, 2023		7,372,207		$	5.65		7.14	$	41,520,355

As of September 30, 2023, total unrecognized compensation expense related to stock options was $39.3 million, which the Company expects to recognize over a remaining weighted-average period of 2.5 years.

Restricted Stock Unit Activity

The following table summarizes the RSU activity for the nine months ended September 30, 2023:


	Number of Stock Units			Weighted Average Grant Date Fair Value Per Share
Unvested and outstanding as of December 31, 2022		—		$	-
Granted		809,738			4.94
Vested		(37,500	)		2.67
Forfeited		(14,591	)		4.60
Unvested and outstanding as of September 30, 2023		757,647		$	5.05

As of September 30, 2023, total unrecognized compensation expense related to RSUs was $3.1 million, which the Company expects to recognize over a remaining weighted-average period of 2.3 years.

2021 Employee Stock Purchase Plan

The 2021 Employee Stock Purchase Plan (the 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 nine months ended September 30, 2023, the Company issued 186,761 shares of common stock under the ESPP.