STOCKHOLDERS' EQUITY (Tables)

12 Months Ended

Dec. 31, 2024

Stockholders' Equity Note [Abstract]

Schedule of aggregate stock option and award activity

Aggregate stock option and award activity for the 2011 Plan, 2018 Plan, Inducement Plan and Directors Market Plan is as follows:

				Outstanding Stock Options
										Weighted Average
	Shares							Weighted Average		Remaining		Aggregate
	Available			Number of				Exercise Price		Contractual Life		Intrinsic
	For Grant			Shares				Per Share		(In years)		Value
Balance at December 31, 2023		58,750,670			72,984,351			$	2.16
Stock options granted		(29,603,740	)		29,603,740			$	2.86
Awards granted		(8,351	)		—			$	—
Stock options exercised		—			(17,907,649	)		$	1.77
Stock options cancelled/forfeited/expired		5,171,390			(8,713,075	)		$	3.24
Balance at December 31, 2024		34,309,969			75,967,367		(1)	$	2.40		7.35	$	94,204,849
Stock options exercisable at   December 31, 2024					37,943,520			$	2.06		5.84	$	57,488,305
Stock options fully vested and expected     to vest at December 31, 2024					74,159,549			$	2.39		7.30	$	92,613,420

(1)Includes 300,000 performance-based stock options granted that have not achieved the specified performance milestone.

Summary of allocation of stock-based compensation expense related to share-based payment awards

The following table summarizes the stock‑based compensation expense related to service-based stock options and employee stock purchases for the years ended December 31, 2024, 2023 and 2022, which was allocated as follows:

	Year Ended December 31,
(In thousands)	2024		2023		2022
Research and development	$	10,280	$	7,426	$	3,720
General and administrative		21,647		11,099		4,281
Total Stock-based compensation expense	$	31,927	$	18,525	$	8,001

Schedule of assumptions used to estimate the fair value of stock options granted

The fair value of stock options granted in 2024, 2023, and 2022 has been estimated at the date of grant using the Black-Scholes option‑pricing model with the following assumptions:

	Year Ended December 31,
	2024	2023	2022
Dividend yield	0%	0%	0%
Expected volatility range	0.72 to 0.87	0.82 to 0.83	0.77 to 0.82
Risk-free interest rate range	3.5% to 4.6%	3.42% to 4.94%	1.69% to 4.57%
Expected term range	6.0 yrs	6.0 yrs	5.5 yrs

Schedule of assumptions used to estimate the fair value of employee stock purchases under the purchase plan

The fair value of employee stock purchases in 2024, 2023, and 2022 has been estimated using the Black-Scholes option‑pricing model with the following assumptions:

	Year Ended December 31,
	2024	2023	2022
Dividend yield	0%	0%	0%
Expected volatility range	0.72. to 1.19	0.79 to 0.83	0.61 to 0.87
Risk-free interest rate range	4.8% to 5.4%	4.73% to 5.4%	0.40% to 2.79%
Expected term range	6 - 12 mos	6 - 12 mos	6 - 12 mos

Schedule of common stock reserved for future issuance

Common stock reserved for future issuance as of December 31, 2024 is as follows:

Outstanding stock options	75,967,367
Stock options and awards available for grant	34,309,969
Employee stock purchase plan	258,366
Warrants outstanding	60,835,667
Total	171,371,369