Stock-based Compensation

6 Months Ended

Jun. 30, 2024

Share-Based Payment Arrangement [Abstract]

9. Stock-based Compensation

During the three and six months ended June 30, 2024 and 2023, the Company recognized the following stock-based compensation expense (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2024		2023		2024		2023
Research and development	$	13,411	$	13,322	$	24,593	$	24,998
General and administrative		10,261		8,443		18,484		17,642
Total	$	23,672	$	21,765	$	43,077	$	42,640

Stock option activity

The following table summarizes stock option activity for the six months ended June 30, 2024:


	Shares			Weighted- average exercise price per share
Outstanding at December 31, 2023		7,204,372		$	55.05
Granted		1,056,224			68.76
Exercised		(677,561	)		37.92
Cancelled or forfeited		(278,612	)		72.96
Outstanding at June 30, 2024		7,304,423		$	57.94
Exercisable at June 30, 2024		4,714,519		$	56.50
Vested and expected to vest at June 30, 2024		7,304,423		$	57.94

As of June 30, 2024, total unrecognized compensation expense related to stock options was $95.1 million, which the Company expects to recognize over a remaining weighted-average period of 2.7 years.

Restricted stock activity

The following table summarizes restricted stock activity for the six months ended June 30, 2024:


	Shares			Weighted- Average Grant Date Fair Value
Unvested balance at December 31, 2023		1,781,415		$	61.00
Granted		706,844			70.50
Vested		(377,926	)		71.41
Cancelled or forfeited		(120,319	)		54.48
Unvested balance at June 30, 2024		1,990,014		$	62.79

As of June 30, 2024, total unrecognized compensation expense related to unvested restricted common shares was $96.2 million, which the Company expects to recognize over a remaining weighted-average vesting period of 2.8 years.