Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2024

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

Schedule of Stock-Based Compensation Expense

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

	Year Ended December 31,
	2024		2023		2022
	(In thousands)
Research and development	$	94,230	$	82,211	$	56,279
General and administrative		60,043		51,839		35,121
Total	$	154,273	$	134,050	$	91,400

Stock Option and Incentive Plans

Summary of Restricted Stock Activity

The following table summarizes the Company’s RSU activity for the year ended December 31, 2024:

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock units as of December 31, 2023		4,041,753		$	50.40
Granted		3,601,376			32.43
Vested		(1,433,669	)		52.08
Cancelled		(661,930	)		43.43
Unvested restricted stock units as of December 31, 2024		5,547,530		$	39.13

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:

	Year Ended December 31,
	2024	2023	2022
Risk-free interest rate	4.2%	4.4%	1.9%
Expected term of options	6.0 years	6.0 years	5.9 years
Expected volatility of underlying stock	76.3%	78.7%	76.2%
Expected dividend yield	0.0%	0.0%	0.0%

Summary of Stock Option Activity

The following is a summary of stock option activity for the year ended December 31, 2024:

	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, 2023		5,458,999		$	50.38		6.65	$	35,922
Granted		918,161			30.72
Exercised		(373,807	)		15.68
Forfeited		(590,567	)		70.25
Outstanding at December 31, 2024		5,412,786		$	47.27		6.18	$	350
Exercisable at December 31, 2024		4,246,614		$	48.40		5.47	$	350

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 shares under the 2016 Plan was estimated at the beginning of the offering period using a Black-Scholes option-pricing model with the following assumptions:

	Year Ended December 31,
	2024	2023	2022
Risk-free interest rate	5.24%-5.37%	4.7%-5.53%	0.22%-2.52%
Expected term (in years)	0.5 years	0.5 years	0.5 years
Expected volatility of underlying stock	56.7%-59.0%	60.4%-69.2%	63.6%-95.3%
Expected dividend yield	0.0%	0.0%	0.0%