Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2018

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 March 31,
	2018		2017
Research and development	$	435	$	323
Selling, general and administrative	1,545		1,346
Total	$	1,980	$	1,669

Schedule of stock-based compensation expense by security types

The following table presents total stock-based compensation expense by security types included in the unaudited condensed consolidated statements of operations for the three months ended March 31, 2018 and 2017 (in thousands):

	Three Months Ended March 31,
	2018		2017
Stock options	$	472	$	334
RSUs and RSAs	452		459
PSUs	409		641
PBOs	647		235
Total	$	1,980	$	1,669

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 March 31,
	2018			2017
Expected term (in years)	5.6			5.3
Volatility	60		%	62		%
Risk-free interest rate	2.70		%	2.00		%
Dividend yield	—			—		%
Weighted-average estimated fair value of stock options granted	$	5.02		$	2.52