The 2021 Stock Option and Incentive Plan (the 2021 Stock Plan) was adopted by the board of directors in December 2020 and the stockholders approved the plan in January 2021, prior to the completion of the Company’s IPO. The 2021 Stock Plan became effective on the day immediately prior to the effectiveness of the Company’s registration statement. The 2020 Unit Option and Grant Plan was terminated once the 2021 Stock Plan was effective. The Company initially reserved 12,546,386 shares of common stock for issuance of awards under the 2021 Stock Plan, which included (x) split-adjusted 320,228 shares of restricted stock issued under the 2021 Stock Plan in connection with the Reorganization and (y) split-adjusted equity awards comprised of (i) 4,616,187 shares of common stock issuable upon the exercise of stock options at a weighted average exercise price of $4.30; and (ii) an aggregate of 1,753,316 shares of common stock issuable upon the exercise of the stock options, with an exercise price equal to the IPO price per share, which were granted to certain executive officers, employees, and affiliates.

The 2021 Stock Plan provides that the number of shares reserved and available for issuance under the 2021 Stock Plan will automatically increase each January 1, beginning on January 1, 2022, by 5% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31 or such lesser number of shares as determined by the Company’s compensation committee. This number is subject to adjustment in the event of a stock split, stock dividend or other change in capitalization.

The Company recorded equity-based compensation in the following expense categories in the consolidated statements of operations and comprehensive income (loss):

	Three Months Ended March 31,
	2020		2021
	(in thousands)
Research and development	$	—	$	1,569
General and administrative		—		1,939
Total equity-based compensation	$	—	$	3,508

The 2021 Employee Stock Purchase Plan (the ESPP) was adopted by our board of directors in December 2020 and the stockholders approved the plan in January 2021, prior to the completion of the Company’s IPO. The ESPP became effective on the day immediately prior to the effectiveness of the Company’s IPO. The Company has initially reserved 416,665 shares of common stock for issuance to participating employees.

The ESPP provides that the number of shares reserved and available for issuance under the ESPP will automatically increase each January 1, beginning on January 1, 2022, by the lesser of 833,330 shares of our common stock, 1% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. This number is subject to adjustment in the event of a stock split, stock dividend or other change in capitalization.

For the Company recorded less than $0.1 million of compensation expense relating to the ESPP for the three months ended March 31, 2021.