Stock-based Compensation Expense (Tables)

9 Months Ended

Sep. 30, 2024

Stock-based Compensation Expense [Abstract]

Stock-Based Compensation Expense

The following table summarizes stock-based compensation expense for the three and nine months ended September 30, 2024 and 2023 (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2024		2023		2024		2023
Cost of sales	$	159	$	118	$	609	$	355
Research, development and patent expense		22,120		18,727		67,111		57,543
Selling, general and administrative expense		9,705		7,119		26,332		21,575
Stock-based compensation expense, net of amounts capitalized	$	31,984	$	25,964	$	94,052	$	79,473
Capitalized stock-based compensation expense		506		—		506		—
Total stock-based compensation expense	$	32,490	$	25,964	$	94,558	$	79,473

Weighted-Average Assumptions for Stock Options

Employee Stock Options:

	Nine Months Ended September 30,
	2024			2023
Risk-free interest rate		4.1	%		3.7	%
Dividend yield		0.0	%		0.0	%
Volatility		43.8	%		47.1	%
Expected life	6.3 years			6.3 years

Board of Director Stock Options:

	Nine Months Ended September 30,
	2024			2023
Risk-free interest rate		4.5	%		3.8	%
Dividend yield		0.0	%		0.0	%
Volatility		49.8	%		53.0	%
Expected life	7.5 years			7.7 years

Weighted-Average Assumptions for ESPP

ESPP:

	Nine Months Ended September 30,
	2024			2023
Risk-free interest rate		5.2	%		5.3	%
Dividend yield		0.0	%		0.0	%
Volatility		37.8	%		36.0	%
Expected life	6 months			6 months