Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2025

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 condensed consolidated statements of operations and comprehensive loss as follows:

	Three Months Ended June 30,				Six Months Ended June 30,
	2025		2024		2025		2024
	(In thousands)
Research and development	$	14,059	$	25,439	$	26,685	$	45,600
General and administrative		7,977		15,422		17,191		29,437
Total	$	22,036	$	40,861	$	43,876	$	75,037

Summary of Restricted Stock Activity

The following table summarizes the Company’s RSU activity for the six months ended June 30, 2025:

	Number of Shares			Weighted Average Grant Date Fair Value per Share
Unvested restricted stock units as of December 31, 2024		5,547,530		$	39.13
Granted		2,407,807			10.49
Vested		(1,686,670	)		42.66
Cancelled		(987,049	)		39.70
Unvested restricted stock units as of June 30, 2025		5,281,618		$	24.84

The weighted-average grant date fair value of all RSUs granted during the three and six months ended June 30, 2025 was $8.10 and $10.49, respectively. The total fair value of RSUs vested (measured on the date of vesting) for the three and six months ended June 30, 2025 was $1.4 million and $18.9 million, respectively. The weighted-average grant date fair value of all RSUs granted during the three and six months ended June 30, 2024 was $25.16 and $34.20, respectively. The total fair value of RSUs vested (measured on the date of vesting) for the three and six months ended June 30, 2024 was $4.6 million and $35.5 million, respectively.

As of June 30, 2025 there was $69.4 million of unrecognized stock-based compensation expense related to all RSUs that are expected to vest. These costs are expected to be recognized over a weighted average remaining vesting period of 1.55 years.

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,
	2025	2024	2025	2024
Risk-free interest rate	4.1%	4.3%	4.1%	4.2%
Expected term	5.5 years	5.6 years	5.9 years	6.0 years
Expected volatility of underlying stock	79.4%	76.3%	75.8%	76.4%
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, 2025:

	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, 2024		5,412,786		$	47.27		6.18	$	350
Granted		720,901			9.90
Forfeited		(692,170	)		68.50
Outstanding at June 30, 2025		5,441,517		$	39.62		6.08	$	255
Exercisable at June 30, 2025		4,176,532		$	45.36		5.14	$	174

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:

	Three Months Ended June 30,		Six Months Ended June 30,
	2025	2024	2025	2024
Risk-free interest rate	4.24%	5.24%	4.24%	5.24%
Expected term	0.5 years	0.5 years	0.5 years	0.5 years
Expected volatility of underlying stock	66.2%	56.7%	66.2%	56.7%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%