Stock Option Plan (Tables)

9 Months Ended

Sep. 30, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Activity under the Company’s stock option plan is set forth below:

							Options Outstanding
	Options Available for Grant			Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (years)		Aggregate Intrinsic Value (in thousands)
Balances at December 31, 2015		331,938			2,685,913		$	4.81		7.63
Options granted		(102,462	)		102,462			10.31
Options exercised		—			(44,702	)		1.88
Options forfeited		11,135			(11,135	)		6.38
Balances at September 30, 2016		240,611			2,732,538		$	5.05		7.11	$	21,880
Options exercisable – September 30, 2016					1,794,651		$	4.17		6.35	$	15,951
Options vested and expected to vest – September 30, 2016					2,680,533		$	5.01		7.08	$	21,568

Schedule of Fair Value of Employee and Director Stock Options Estimated Using Weighted Average Assumptions

The fair value of employee and director stock options was estimated at the date of grant using a Black-Scholes option valuation model with the weighted average assumptions below.

	Three Months Ended September 30						Nine Months Ended September 30,
	2016			2015			2016			2015
Expected term (in years)		6.1			6.1			6.1			6.1
Expected volatility		60.0	%		60.0	%		60.0	%		60.0	%
Risk-free interest rate		1.28	%		1.87	%		1.45	%		1.73	%
Dividend yield		0.0	%		0.0	%		0.0	%		0.0	%

Summary of Total Stock-Based Compensation Expense Included in Statements of Operations and Comprehensive Loss

The following table summarizes the total stock-based compensation expense included in the statements of operations and comprehensive loss for all periods presented (in thousands):

	Three Months Ended September 30				Nine Months Ended September 30,
	2016		2015		2016		2015
Cost of revenue	$	3	$	2	$	8	$	14
Research and development		34		17		103		137
Selling, general and administrative		364		299		1,140		884
Total stock-based compensation expense	$	401	$	318	$	1,251	$	1,035