Equity-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 March 31,
	2023		2022
	(In thousands)
Research and development	$	16,931	$	10,274
General and administrative		10,324		8,217
Total	$	27,255	$	18,491

Summary of Restricted Stock Activity

The following table summarizes the Company’s RSU activity for the three months ended March 31, 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		2,482,686			42.78
Vested		(342,025	)		77.89
Cancelled		(27,553	)		59.57
Unvested restricted stock units as of March 31, 2023		4,054,487		$	53.07

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 March 31,
	2023	2022
Risk-free interest rate	4.4%	1.6%
Expected life of options	6.0 years	6.0 years
Expected volatility of underlying stock	78.7%	75.9%
Expected dividend yield	0.0%	0.0%

Summary of Stock Option Activity

The following is a summary of stock option activity for the three months ended March 31, 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		513,605			40.75
Exercised		(48,353	)		15.61
Forfeited		(31,838	)		100.62
Outstanding at March 31, 2023		5,905,089		$	49.08		7.37	$	59,380
Exercisable at March 31, 2023		3,533,700		$	39.25		6.70	$	48,649

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 March 31,
	2023	2022
Risk-free interest rate	4.70%	0.22%
Expected term (in years)	0.5 years	0.5 years
Expected volatility of underlying stock	69.2%	63.6%
Expected dividend yield	0.0%	0.0%