Stockholders' Equity (Tables)

9 Months Ended

Sep. 30, 2020

Stock-Based Compensation Expense

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

	Three Months Ended September 30,				Nine Months Ended September 30,
	2020		2019		2020		2019
			(Amounts in thousands)
Cost of product revenue	$	563	$	375	$	1,421	$	992
Research and development		326		351		1,092		992
Selling, general and administrative		3,336		2,449		9,979		7,475
Total stock-based compensation	$	4,225	$	3,175	$	12,492	$	9,459

Summary of Option Activity

Information regarding option activity for the nine months ended September 30, 2020 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, 2019		957,559		$	30.81
Granted		69,698		$	104.61
Exercised		(303,343	)	$	23.37
Forfeited/expired/cancelled		—		$	—
Options outstanding at September 30, 2020		723,914		$	41.03		7.02	$	77,102
Options exercisable at September 30, 2020		339,191		$	31.00		6.05	$	39,528
Vested and expected to vest at September 30, 2020(1)		693,689					6.98	$	74,178

(1) Represents the number of vested options as of September 30, 2020 plus the number of unvested options expected to vest as of September 30, 2020 based on the unvested outstanding options at September 30, 2020 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

The fair value of stock units is calculated using the closing price of the Company’s common stock on the date of grant. Information regarding stock unit activity, which includes activity for restricted stock units and performance stock units, for the nine months ended September 30, 2020 under the Plans is summarized below:

	Shares			Weighted- Average Remaining Contractual Term (in Years)		Aggregate Intrinsic Value (in Thousands)
Unvested at December 31, 2019		734,984
Awarded		187,942
Vested		(225,204	)
Forfeited/expired/cancelled		(22,155	)
Unvested at September 30, 2020		675,567			3.39	$	99,673
Vested and expected to vest at September 30, 2020(1)		650,436			3.20	$	95,965

(1) Represents the number of vested stock units as of September 30, 2020 plus the number of unvested stock units expected to vest as of September 30, 2020 based on the unvested outstanding stock units at September 30, 2020 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.