Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2016

Stock-Based Compensation Expense

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

	Years ended December 31,
	2016		2015		2014
Cost of product revenue	$	341	$	213	$	128
Research and development		537		336		185
Selling, general and administrative		3,717		3,049		1,453
Total	$	4,595	$	3,598	$	1,766

Estimated Weighted Average Assumptions

The fair value of share-based awards granted during the years ended December 31, 2016, 2015 and 2014 were calculated using the following estimated assumptions:

	2016	2015	2014
Expected term (years)	6.7 – 7.1	6.6 – 7.2	6.5
Volatility	50.85 – 51.01%	50.09 – 51.89%	51.00 – 51.71%
Risk-free interest rate	1.51 – 2.37%	1.67 – 2.03%	1.88 – 2.11%
Expected dividend yield	—	—	—

Summary of Option Activity

Information regarding option activity for the year ended December 31, 2016 under the Plans is summarized below:

	Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		(in thousands) Aggregate Intrinsic Value
Options outstanding at December 31, 2015		1,054,584		$	12.28
Granted		183,619			27.12
Exercised		(266,863	)		7.72
Forfeited/cancelled		(88,592	)		10.97
Options outstanding at December 31, 2016		882,748		$	16.88		6.75	$	12,733
Options exercisable at December 31, 2016		427,310		$	11.11		5.23	$	8,617
Vested and expected to vest at December 31, 2016(1)		837,660		$	16.82		6.70	$	12,140

(1) Represents the number of vested options as of December 31, 2016 plus the number of unvested options expected to vest as of December 31, 2016 based on the unvested outstanding options at December 31, 2016 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 restricted stock unit activity for the year ended December 31, 2016 under the Plans is summarized below:

	Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Term (in years)		(in thousands) Aggregate Intrinsic Value
Restricted stock units outstanding at December 31, 2015		186,351		$	—
Granted		251,384			—
Exercised		(63,017	)		—
Forfeited/cancelled		(20,880	)		—
Restricted stock units outstanding at December 31, 2016		353,838		$	—		9.01	$	10,905
Restricted stock units exercisable at December 31, 2016		—		$	—		—	$	—
Vested and expected to vest at December 31, 2016(1)		309,229		$	—		9.01	$	9,530

(1) Represents the number of vested restricted stock units as of December 31, 2016 plus the number of unvested restricted stock units expected to vest as of December 31, 2016 based on the unvested outstanding restricted stock units at December 31, 2016 adjusted for estimated forfeiture rates of 8% for awards granted to non-executive level employees and 3% for awards granted to executive level employees.