Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2023

Share-Based Payment Arrangement [Abstract]

Total Stock-Based Compensation Expense

Total share-based compensation expense related to all of the Company’s share-based awards, including stock options and RSUs granted to employees and directors recognized during the years ended December 31, 2023, 2022, and 2021, was comprised of the following (in thousands):

	Years Ended December 31,
	2023		2022		2021
Inventoriable costs	$	1,610	$	1,791	$	1,624
Research and development	15,781		15,387		9,832
Selling, general and administrative	35,441		25,835		22,847
Total share-based compensation expense	$	52,832	$	43,013	$	34,303

Assumptions Used for Calculating Value of Options Granted

The following table describes the assumptions used for calculating the value of options granted during the years ended December 31, 2023, 2022 and 2021:

	Years Ended December 31,
	2023		2022		2021
Dividend yield	0	%	0	%	0	%
Expected volatility	74.8%-78.0%		78.7-88.7%		89.4-94.9%
Weighted-average risk-free interest rate	3.92	%	2.22	%	0.87	%
Expected term (in years)	6.0		5.9		5.9

Stock Option Activity

Information regarding the stock options activity, including with respect to grants to employees, directors and consultants under the Amended 2018 Plan and 2019 Inducement Plan as of December 31, 2023, and changes during the year then ended, are summarized as follows:

	Number of Shares	Weighted- Average Exercise Price		Weighted- Average Contractual Life
Outstanding at December 31, 2022	4,785,972	$	26.27	5.8 years
Options granted 2023	289,084	48.13
Options exercised 2023	(791,795)	22.49
Options canceled 2023	(39,854)	51.05
Options expired 2023	(3,425)	40.94
Outstanding at December 31, 2023	4,239,982	$	28.22	5.2 years
Vested and expected to vest at December 31, 2023	4,239,982	$	28.22
Exercisable at December 31, 2023	3,470,018	$	23.55	4.5 years

The following table details the value of options during the years ended December 31, 2023, 2022 and 2021 (in thousands):

	Years Ended December 31,
	2023		2022		2021
Intrinsic value of options exercised	$	27,187	$	48,267	$	19,688
Intrinsic value of options outstanding	184,027		130,078		172,964
Intrinsic value of options exercisable	166,820		118,340		131,235
Fair value of shares vested	19,120		17,145		10,583

Summary of Information Regarding RSU Activity

Information regarding time based RSU activity, including with respect to grants to employees under the Amended 2018 Plan and 2019 Inducement Plan as of December 31, 2023, and changes during the year then ended, is summarized as follows:

	Number of Shares	Weighted- Average Grant Date Fair Value Per Share		Weighted- Average Contractual Life
Outstanding at December 31, 2022	1,274,664	$	42.76	0.8 years
Time based RSUs granted in 2023	1,109,622	48.58
Time based RSUs vested in 2023	(665,824)	36.65
Time based RSUs cancelled in 2023	(73,332)	48.29
Outstanding at December 31, 2023	1,645,130	$	48.92	1.0 years

The following table details the value of time based RSUs during the years ended December 31, 2023, 2022 and 2021 (in thousands):

	Years Ended December 31,
	2023	2022	2021
Intrinsic value of time based RSUs outstanding	117,824	67,455	80,062
Fair value of RSUs vested	24,400	17,873	12,411