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. In June 2024, in connection with the Company's 2024 annual shareholder meeting, shareholders approved an amendment to the 2020 stock option plan that redefined the definition of common stock outstanding for the purposes of calculating the annual increase to the shares available for issuance. After the amendment, outstanding equity includes all outstanding common shares as well as outstanding pre-funded warrants. As of June 30, 2024, there were an aggregate of 3,668,601 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 June 30, 2024, there were an aggregate 1,957,168 shares remaining available for future grants.

A summary of stock option activity under the 2020 Plan during the six months ended June 30, 2024 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, 2023		8,113,164		$	28.25		7.69	$	49,622
Granted		2,393,371			42.02
Exercised		(355,339	)		12.84
Forfeited		(248,360	)		34.29
Outstanding at June 30, 2024		9,902,836		$	31.98		7.80	$	57,034
Exercisable at June 30, 2024		5,684,450		$	27.94		6.86	$	53,039

The intrinsic value of stock options exercised during the three months ended June 30, 2024 and 2023 was $1.8 million and $1.4 million, respectively. The intrinsic value of stock options exercised during the six months ended June 30, 2024 and 2023 was $8.6 million and $6.9 million, respectively.

The weighted-average fair value of options granted during the three months ended June 30, 2024 and 2023 was $19.28 and $17.50, respectively. The weighted-average fair value of options granted during the six months ended June 30, 2024 and 2023 was $25.92 and $18.45 respectively.

As of June 30, 2024, the total unrecognized stock-based compensation expense for unvested stock options was $90.9 million, with a weighted average recognition period of 2.3 years.

The following table outlines our equity-based compensation expense for stock options for the three and six months ended June 30, 2024 and 2023:


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	5,935	$	4,976	$	10,975	$	9,160
General and administrative		6,306		5,110		11,628		9,459
Total equity-based compensation	$	12,241	$	10,086	$	22,603	$	18,619

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 six months ended June 30, 2024 and 2023 were as follows:


	Three Months Ended June 30,						Six Months Ended June 30,
	2024			2023			2024			2023
Expected term (in years)		5.71			5.95			5.78			5.85
Volatility		65	%		62	%		65	%		62	%
Risk-free interest rate		4.25	%		3.71	%		4.14	%		4.06	%
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 six months ended June 30, 2024 is as follows:


	Number of Units Outstanding			Grant Date Fair Value per Share
Unvested at December 31, 2023		593,140		$	25.36
Granted		243,984			42.73
Vested		(163,903	)		25.32
Forfeited		(36,636	)		27.24
Unvested at June 30, 2024		636,585		$	31.92

During the three months ended June 30, 2024 and 2023, the Company granted 12,150 and 47,697 restricted stock units, respectively. During the six months ended June 30, 2024 and 2023, the Company granted 243,984 and 263,986 restricted stock units, respectively. As of June 30, 2024, the total unrecognized stock-based compensation expense for unvested restricted stock was $17.4 million with a weighted average recognition period of 2.3 years.

During the three months ended June 30, 2024 the Company recognized approximately $1.9 million of expense for restricted stock of which $1.2 million and $0.7 million was recorded in research and development and general and administrative expense, respectively. During the six months ended June 30, 2024 the Company recognized approximately $3.3 million of expense for restricted stock of which $2.1 million and $1.2 million was recorded in research and development and general and administrative expense, respectively. During the three months ended June 30, 2023 the Company recognized approximately $0.9 million of expense for restricted stock of which $0.6 million and $0.3 million was recorded in research and development and general and administrative expense, respectively. During the six months ended June 30, 2023 the Company recognized approximately $1.5 million of expense for restricted stock of which $1.0 million and $0.5 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 six months ended June 30, 2024 and 2023 is as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	7,257	$	5,704	$	13,340	$	10,432
General and administrative		7,084		5,477		12,969		10,133
Total equity-based compensation	$	14,341	$	11,181	$	26,309	$	20,565