Equity-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2023

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Schedule of Equity-Based Compensation Expense

Equity-based compensation expense is classified in the condensed consolidated statements of operations and comprehensive loss as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2023		2022		2023		2022
	(In thousands)
Research and development	$	22,351	$	14,079	$	39,282	$	24,353
General and administrative		14,049		8,989		24,373		17,206
Total	$	36,400	$	23,068	$	63,655	$	41,559

Summary of Restricted Stock Activity

The following table summarizes the Company’s RSU activity for the six months ended June 30, 2023:

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock units as of December 31, 2022		1,941,379		$	70.70
Granted		2,701,197			42.45
Vested		(493,878	)		70.91
Cancelled		(61,694	)		55.91
Unvested restricted stock units as of June 30, 2023		4,087,004		$	52.23

Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted

Weighted average assumptions used to apply this pricing model were as follows:

	Three Months Ended June 30,		Six Months Ended June 30,
	2023	2022	2023	2022
Risk-free interest rate	4.1%	3.4%	4.4%	1.9%
Expected life of options	5.6 years	5.6 years	6.0 years	5.9 years
Expected volatility of underlying stock	78.8%	77.9%	78.7%	76.2%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%

Summary of Stock Option Activity

The following is a summary of stock option activity for the six months ended June 30, 2023:

	Number of Options			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)		(In thousands)
Outstanding at December 31, 2022		5,471,675		$	49.86
Granted		569,821			41.00
Exercised		(78,724	)		15.51
Forfeited		(61,755	)		95.52
Outstanding at June 30, 2023		5,901,017		$	48.99		6.89	$	68,634
Exercisable at June 30, 2023		3,848,672		$	40.24		6.19	$	59,876

2016 Employee Stock Purchase Plan [Member]

Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]

Summary of Weighted Average Assumptions Used to Compute Fair Value of Option Granted

The fair value of the awards issued to employees under the 2016 Plan was estimated at the beginning of the offering period using a Black-Scholes option-pricing model with the following assumptions:

	Three Months Ended June 30,		Six Months Ended June 30,
	2023	2022	2023	2022
Risk-free interest rate	4.70%	0.22%	4.70%	0.22%
Expected term (in years)	0.5 years	0.5 years	0.5 years	0.5 years
Expected volatility of underlying stock	69.2%	63.6%	69.2%	63.6%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%