On January 16, 2024, the Company commenced an offer to certain eligible employees and consultants to exchange certain outstanding eligible options to purchase shares of the Company’s common stock for a lesser number of restricted stock unit (RSU) awards pursuant to an option exchange program (the Option Exchange). The Option Exchange expired on February 12, 2024. Pursuant to the Option Exchange, eligible option holders elected to exchange, and the Company accepted for cancellation, eligible options to purchase an aggregate of 5,059,129 shares of the Company’s common stock, representing approximately 98% of the total shares of common stock underlying the eligible options. On February 13, 2024, immediately following the expiration of the Option Exchange, the Company granted 2,129,594 shares of Replacement RSU Awards, pursuant to the terms of the Option Exchange. The Replacement RSU Awards will vest based on continued service with the Company over a period of either 1, 2 or 3 years, depending on the grant date of the exchanged options.

The exchange of stock options was treated as a modification for accounting purposes, which requires an incremental expense of $8.6 million to be recognized for the Replacement RSU Awards over their new service periods (1 - 3 years). In addition, any unamortized expense remaining on the exchanged options as of the modification will be recognized over their original remaining service period.

The following summarizes option activity:


	Number of Options	Weighted- Average Exercise Price		Remaining Contractual Term (Years)	Aggregate Intrinsic Value ($, in thousands)
Balance—December 31, 2024	5,342,909	$	6.69	8.01	$	43,120
Granted	2,223,719	13.69
Exercised	(129,217)	3.59
Forfeited	(512,105)	9.61
Expired	(2,865)	26.87
Balance—June 30, 2025	6,922,441	$	8.77	7.99	$	40,747
Exercisable—June 30, 2025	2,805,705	$	8.26	6.40	$	20,359

The aggregate intrinsic value is calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock as of June 30, 2025. The intrinsic value of options exercised for the six months ended June 30, 2025 and 2024 was $1.4 million and $0.8 million, respectively.

The total grant-date fair value of the options vested during the six months ended June 30, 2025 and 2024 was $4.6 million and $2.2 million, respectively. The weighted-average grant-date fair value of options granted during the six months ended June 30, 2025 and 2024 was $9.69 and $3.59, respectively.


	Number of Units	Weighted-Average Grant Date Fair Value
Balance—December 31, 2024	6,055,087	$	8.04
Granted	2,783,897	13.70
Vested	(1,703,742)	8.64
Forfeited	(552,782)	10.06
Unvested Balance—June 30, 2025	6,582,460	$	10.11

The grant date fair value of an RSU equals the closing price of the Company's common stock on the grant date. RSUs generally vest equally over four years, except for those issued in connection with the Option Exchange as previously described.

Stock-based compensation expense included in the condensed consolidated statements of operations and comprehensive loss was as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2025		2024		2025		2024
Research and development	$	3,208	$	3,799	$	6,228	$	7,456
Selling, general and administrative	7,281		8,724		14,039		15,097
Total stock-based compensation expense	$	10,489	$	12,523	$	20,267	$	22,553

As of June 30, 2025, there was $32.3 million of total unrecognized compensation cost related to unvested options that are expected to vest, which is expected to be recognized over a weighted-average period of 2.8 years. As of June 30, 2025, there was $56.9 million of total unrecognized compensation cost related to RSUs that are expected to vest, which is expected to be recognized over a weighted-average period of 3.0 years.