The Company recorded stock-based compensation expense within its condensed consolidated statements of operations and comprehensive loss as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development expenses	$	7,322	$	2,693	$	13,985	$	5,206
General and administrative expenses		7,803		3,155		14,997		6,013
	$	15,125	$	5,848	$	28,982	$	11,219

As of June 30, 2024, total unrecognized compensation cost related to equity-based awards was $150.9 million, which is expected to be recognized over a weighted average period of 2.7 years.

In July 2021, the Company adopted the 2021 Stock Option and Incentive Plan (the “2021 Plan”). The 2021 Plan provides for the grant of incentive stock options, non-qualified stock options, stock appreciation rights, restricted stock awards, restricted stock units (“RSUs”), unrestricted stock awards, cash-based awards and dividend equivalent rights. Stock awards granted under the 2021 Plan with service-based vesting conditions generally vest over three- or four-year service periods, and stock options expire after ten years. As of June 30, 2024, 7,068,809 shares of Class A common stock remained available for future issuance under the 2021 Plan.

In July 2021, the Company adopted the 2021 Employee Stock Purchase Plan, as amended and restated (the “ESPP”). The ESPP permits eligible employees to purchase shares of Class A common stock at a discount in accordance with the terms of the offering and consists of consecutive, overlapping 12-month offering periods, each consisting of two six-month purchase periods beginning in December and June of each year. During the three and six months ended June 30, 2024, 5,237 shares were sold under the ESPP. As of June 30, 2024, 1,873,832 shares of Class A common stock remained available for issuance under the ESPP.

The following table summarizes the Company’s option activity since December 31, 2023:


						Weighted
						Average
				Weighted		Remaining		Aggregate
				Average		Contractual		Intrinsic
	Number			Exercise		Term		Value
	of Shares			Price		(in years)		(in thousands)
Outstanding as of December 31, 2023		8,034,755		$	17.66		8.06	$	449,403
Granted		1,198,801		$	75.18
Exercised		(649,595	)	$	16.09
Cancelled or forfeited		(22,717	)	$	34.87
Outstanding as of June 30, 2024		8,561,244		$	25.78		7.85	$	430,979
Exercisable as of June 30, 2024		4,113,020		$	13.42		7.18	$	256,837

The aggregate intrinsic value of stock options exercised during the three months ended June 30, 2024 and 2023 was $12.2 million and $6.3 million, respectively. The aggregate intrinsic value of stock options exercised during the six months ended June 30, 2024 and 2023 was $40.2 million and $8.1 million, respectively. The aggregate intrinsic value of stock options is calculated as the difference between the exercise price of the stock options and the fair value of the Company’s common stock for those stock options that had exercise prices lower than the fair value of the Company’s common stock on the date of exercise.

The weighted average grant-date fair value of stock options granted during the three months ended June 30, 2024 and 2023 was $50.35 per share and $28.89 per share, respectively. The weighted average grant-date fair value of stock options granted during the six months ended June 30, 2024 and 2023 was $51.79 per share and $20.68 per share, respectively.

The following table summarizes the Company’s RSU activity since December 31, 2023:


	Number of Shares			Weighted Average Grant-Date Fair Value
Outstanding as of December 31, 2023		—		$	—
Granted		652,281		$	73.93
Vested		—		$	—
Forfeited		(2,000	)	$	72.35
Outstanding as of June 30, 2024		650,281		$	73.94