In November 2018, the Company adopted, and its stockholders approved, the 2018 Stock Option and Grant Plan (the “2018 Plan”), which provides for the granting of stock options and other equity-based awards at the discretion of the Board of Directors or any subcommittee of the Board of Directors to the Company’s employees, officers, directors, and independent contractors. No further grants will be made under the 2018 Plan. However, the 2018 Plan will continue to govern outstanding equity awards granted thereunder. To the extent outstanding options granted under the 2018 Plan are cancelled, forfeited or otherwise terminated without being exercised and would otherwise have been returned to the share reserve under the 2018 Plan, the number of shares underlying such awards will be available for future grant under the 2020 Stock Option and Incentive Plan.

In August 2020, the Company and its stockholders approved the 2020 Stock Option and Incentive Plan (the “2020 Plan”), which became effective on August 20, 2020. The 2020 Plan replaced the 2018 Plan as the Company’s Board of Directors has determined not to make additional awards under the 2018 Plan following the closing of the Company’s IPO. The 2020 Plan allows the Company to make equity-based and cash-based incentive awards to its officers, employees, directors and consultants. The Company has initially reserved 4,457,370 shares of its common stock for the issuance of awards under the 2020 Plan, which includes the shares of common stock remaining available for issuance under its 2018 Plan as of the business day immediately prior to the effective date of the registration statement. The 2020 Plan provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter, by 4% of the Company’s outstanding number of shares of common stock on the immediately preceding December 31, or such lesser number of shares as determined by the Company’s compensation committee. These limits are subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. As of September 30, 2023, there were an aggregate of 3,776,080 shares remaining available for future grants.

In August 2020, the Company and its stockholders approved the 2020 Employee Stock Purchase Plan (the “2020 ESPP”), which became effective August 20, 2020. The 2020 ESPP initially reserved and authorized the issuance of up to a total of 445,653 shares of common stock to participating employees. The 2020 ESPP provides that the number of shares reserved and available for issuance will automatically increase on January 1, 2021 and each January 1 thereafter through January 1, 2030, by the lesser of (i) 438,898 shares of common stock, (ii) 1% of the Company’s outstanding number of shares of common stock on the immediately preceding December 31 or (iii) such lesser number of shares of common stock as determined by the administrator of the 2020 ESPP. The number of shares reserved under the 2020 ESPP is subject to adjustment in the event of a stock split, stock dividend or other change in the Company’s capitalization. As of September 30, 2023, there were an aggregate 1,607,727 shares remaining available for future grants.

A summary of stock option activity under the 2020 Plan during the nine months ended September 30, 2023 is as follows (in thousands except share and per share data):


	Number of Options Outstanding			Weighted Average Strike Price per Option		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2022		6,757,289		$	27.60		8.01	$	55,934
Granted		2,525,540			30.41
Exercised		(335,065	)		6.86
Forfeited		(697,825	)		40.11
Outstanding at September 30, 2023		8,249,939		$	28.25		7.90	$	21,333
Exercisable at September 30, 2023		4,574,209		$	24.87		7.15	$	19,715

The intrinsic value of stock options exercised during the three months ended September 30, 2023 and 2022 was $1.1 million and $2.8 million, respectively. The intrinsic value of stock options exercised during the nine months ended September 30, 2023 and 2022 was $7.9 million and $11.5 million, respectively.

The weighted-average fair value of options granted during the three months ended September 30, 2023 and 2022 was $13.35 and $14.18, respectively. The weighted-average fair value of options granted during the nine months ended September 30, 2023 and 2022 was $18.19 and $20.62, respectively.

As of September 30, 2023, the total unrecognized stock-based compensation expense for unvested stock options was $64.9 million, with a weighted average recognition period of 2.2 years.

The following table outlines our equity-based compensation expense for stock options for the three and nine months ended September 30, 2023 and 2022:


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	4,931	$	4,348	$	14,091	$	12,383
General and administrative		5,440		4,052		14,899		12,689
Total equity-based compensation	$	10,371	$	8,400	$	28,990	$	25,072

The weighted-average assumptions that the Company used in the Black-Scholes option pricing model to determine the grant date fair value of stock options granted to employees and non-employees for the three and nine months ended September 30, 2023 and 2022 were as follows:


	Three Months Ended September 30,						Nine Months Ended September 30,
	2023			2022			2023			2022
Expected term (in years)		6.08			6.01			5.86			5.84
Volatility		62	%		63	%		62	%		62	%
Risk-free interest rate		4.14	%		3.01	%		4.06	%		1.95	%
Dividend yield		0.00	%		0.00	%		0.00	%		0.00	%

The Company has granted shares of restricted stock units with service-based and performance-based vesting conditions. A summary of restricted stock activity during the nine months ended September 30, 2023 is as follows:


	Number of Units Outstanding			Grant Date Fair Value per Share
Unvested at December 31, 2022		281,843		$	23.64
Granted		393,556
Vested		(36,371	)
Forfeited		(51,361	)
Unvested at September 30, 2023		587,667		$	25.60

During the nine months ended September 30, 2023 and 2022, the Company granted 393,556 and 283,328 restricted stock units, respectively. As of September 30, 2023, the total unrecognized stock-based compensation expense for unvested restricted stock was $12.3 million with a weighted average recognition period of 2.6 years.

During the three months ended September 30, 2023 the Company recognized approximately $1.1 million of expense for restricted stock of which $0.7 million and $0.4 million was recorded in research and development and general and administrative expense, respectively. During the nine months ended September 30, 2023 the Company recognized approximately $2.6 million of expense for restricted stock of which $1.7 million and $0.9 million was recorded in research and development and general and administrative expense, respectively. During the three months ended September 30, 2022 the Company recognized approximately $0.5 million of expense for restricted stock of which $0.4 million and $0.1 million was recorded in research and development and general and administrative expense, respectively. During the nine months ended September 30, 2022 the Company recognized approximately $0.9 million for restricted stock of which $0.7 million and $0.2 million was recorded in research and development and general and administrative expense, respectively.

Total equity-based compensation expense recorded as research and development and general and administrative expenses for employees, directors, and non-employees during the three and nine months ended September 30, 2023 and 2022 is as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development	$	5,795	$	4,852	$	16,227	$	13,522
General and administrative		5,860		4,224		15,993		13,049
Total equity-based compensation	$	11,655	$	9,076	$	32,220	$	26,571