Stock-based Compensation

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Stock-based Compensation

9. Stock-based Compensation

During the three and six months ended June 30, 2022 and 2021, the Company recognized the following stock-based compensation expense (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development	$	13,829	$	16,195	$	28,419	$	29,040
General and administrative		11,023		12,136		22,178	$	21,383
Total	$	24,852	$	28,331	$	50,597	$	50,423

Stock option activity

The following table summarizes stock option activity for the six months ended June 30, 2022:

	Shares			Weighted- average exercise price per share
Outstanding at December 31, 2021		7,812,982		$	58.07
Granted		1,110,439			59.67
Exercised		(652,333	)		31.92
Cancelled or forfeited		(469,439	)		76.85
Outstanding at June 30, 2022		7,801,649		$	59.36
Exercisable at June 30, 2022		4,746,997		$	47.11
Vested and expected to vest at June 30, 2022		7,801,649		$	59.36

As of June 30, 2022, total unrecognized compensation expense related to stock options was $142.7 million, which the Company expects to recognize over a remaining weighted-average period of 2.6 years.

Restricted stock activity

The following table summarizes restricted stock activity for the six months ended June 30, 2022:

	Restricted Stock			Weighted- Average Grant Date Fair Value
Unvested balance as of December 31, 2021		934,175		$	100.14
Granted		419,726			58.38
Vested		(138,269	)		85.19
Cancelled or forfeited		(129,763	)		92.71
Unvested balance as of June 30, 2022		1,085,869		$	86.79

As of June 30, 2022, total unrecognized compensation expense related to unvested restricted common shares was $69.9 million, which the Company expects to recognize over a remaining weighted-average vesting period of 2.6 years.