Stock-based Compensation Expense

6 Months Ended

Jun. 30, 2025

Stock-based Compensation Expense [Abstract]

9. Stock-based Compensation Expense

The following table summarizes stock-based compensation expense for the three and six months ended June 30, 2025 and 2024 (in thousands):


	Three Months Ended				Six Months Ended
	June 30,				June 30,
		2025		2024		2025		2024
Cost of sales	$	610	$	246	$	710	$	450
Research, development and patent expense		19,542		22,766		39,840		44,991
Selling, general and administrative expense		9,538		7,716		18,858		16,627
Stock-based compensation expense, net of amounts capitalized		29,690		30,728		59,408		62,068
Capitalized stock-based compensation expense		509		-		1,000		-
Total stock-based compensation expense	$	30,199	$	30,728	$	60,408	$	62,068

As of June 30, 2025, total unrecognized estimated stock-based compensation expense related to non-vested stock options, RSUs and PRSUs was $42.3 million, $98.7 million and $15.4 million, respectively. Our actual expenses will likely differ from these estimates because we will adjust our unrecognized stock-based compensation expense for future forfeitures, including any PRSUs that do not vest. We expect to recognize the cost of stock-based compensation expense related to our non-vested stock options, RSUs and PRSUs over a weighted average amortization period of 1.3 years, 1.6 years and 1.7 years, respectively.

Refer to Part IV, Item 15, Note 1, Organization and Significant Accounting Policies, of our audited financial statements included in our Annual Report on Form 10-K for the year ended December 31, 2024 for further details on how we determine the fair value of stock options granted, RSUs, PRSUs and stock purchase rights under the ESPP.

For the six months ended June 30, 2025 and 2024, we used the following weighted-average assumptions in our Black-Scholes calculations:

Employee Stock Options:


	Six Months Ended
	June 30,
		2025		2024
Risk-free interest rate		4.5	%	4.1	%
Dividend yield		0.0	%	0.0	%
Volatility		42.0	%	43.9	%
Expected life		6.3 years		6.3 years

ESPP:


	Six Months Ended
	June 30,
		2025		2024
Risk-free interest rate		4.3	%	5.3	%
Dividend yield		0.0	%	0.0	%
Volatility		41.3	%	38.4	%
Expected life		6 months		6 months

RSUs:

The weighted-average grant date fair value of RSUs granted to employees for the six months ended June 30, 2025 and 2024 was $32.97 and $52.60 per share, respectively.

PRSUs:

Under the terms of the PRSUs we granted in 2025 and 2024, the PRSUs may vest at the end of the three-year performance period based on our relative total shareholder return, or TSR, as compared to a peer group of companies and as measured at the end of the performance period. Under the terms of the grants, no number of PRSUs is guaranteed to vest and the actual number of PRSUs that will vest at the end of each performance period may be anywhere from zero to 200 percent of the target number depending on our relative TSR.

The weighted-average grant date fair value of PRSUs we granted to our executive officers for the six months ended June 30, 2025 and 2024 was $48.81 and $78.41 per share, respectively.