Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock-based compensation expense

Stock-based compensation expense is included in the consolidated statements of operations as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Research and development	$	386	$	246	$	1,050	$	688
Selling, general and administrative	1,447		984		4,162		3,173
Total	$	1,833	$	1,230	$	5,212	$	3,861

Schedule of stock-based compensation expense by security types

The following table presents total stock-based compensation expense by security types included in the condensed consolidated statements of operations for the three and nine months ended September 30, 2017 and 2016 (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Stock options	$	393	$	249	$	1,107	$	820
RSUs and RSAs	456		445		1,399		1,580
PSUs	385		536		1,373		1,461
PBOs	599		—		1,333		—
Total	$	1,833	$	1,230	$	5,212	$	3,861

Valuation assumptions

The weighted-average assumptions used to estimate the fair value of employee stock options and PBOs granted were as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2017	2016			2017			2016
	(1)
Expected term (in years)	—	5.2			5.3			5.3
Volatility	—	63		%	62		%	65		%
Risk-free interest rate	—	1.18		%	2.02		%	1.29		%
Dividend yield	—	—		%	—		%	—		%
Weighted-average estimated fair value of stock options granted	—	$	2.25		$	2.52		$	2.51

(1) The Company did not grant employee stock options or PBOs in the three months ended September 30, 2017.