Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2021

Stock-Based Compensation Expense

The following table presents stock-based compensation expense in the Company’s consolidated statements of comprehensive income:

	For the Years Ended December 31,
	2021		2020		2019
	(Amounts in thousands)
Cost of product revenue	$	2,021	$	1,929	$	1,368
Research and development		2,856		1,534		1,373
Selling, general and administrative		22,623		13,544		10,106
Total stock-based compensation	$	27,500	$	17,007	$	12,847

Estimated Weighted Average Assumptions

The fair value of stock option awards granted during the years ended December 31, 2021, 2020 and 2019 were calculated using the following estimated assumptions:

	For the Years Ended December 31,
	2021	2020	2019
Expected term (in years)	5.5-6.5	5.5-6.5	5.5-6.5
Expected volatility (range)	44.57-45.27%	45.14-50.87%	45.14-50.87%
Risk-free interest rate	0.77-1.07%	0.34-1.15%	1.55-2.56%
Expected dividend yield	0%	0%	0%

Summary of Option Activity

Information regarding option activity for the year ended December 31, 2021 under the Plans is summarized below:

	Shares			Weighted average exercise price		Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Options outstanding at December 31, 2020		696,711		$	43.88		6.90	$	102,958
Granted		38,824		$	202.88
Exercised		(98,428	)	$	39.36
Forfeited/expired/cancelled		(12,000	)	$	60.95
Options outstanding at December 31, 2021		625,107		$	54.15		6.29	$	131,707
Options exercisable at December 31, 2021		326,416		$	37.41		5.61	$	74,238
Vested and expected to vest at December 31, 2021(1)		606,465					6.28	$	127,889

(1)Represents the number of vested options as of December 31, 2021 plus the number of unvested options expected to vest as of December 31, 2021 based on the unvested outstanding options at December 31, 2021 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.

Summary of Restricted Stock Unit Activity

Information regarding stock unit activity, which includes

activity for restricted stock units and performance stock units, for the year ended December 31, 2021 under the Plans is summarized below:

	Shares			Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Unvested at December 31, 2020		665,540			3.32	$	127,904
Awarded		187,588
Vested		(212,329	)
Forfeited/expired/cancelled		(34,114	)
Unvested at December 31, 2021		606,685			3.07	$	160,674
Vested and expected to vest at December 31, 2021(1)		613,606			2.48	$	162,507

(1)Represents the number of vested stock units as of December 31, 2021 plus the number of unvested stock units expected to vest as of December 31, 2021 based on the unvested outstanding stock units at December 31, 2021 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.