Stock based Compensation (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2015

Dec. 31, 2014

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

Summary Stock Option Activity

A summary of the Company’s stock option activity and related information is as follows:

				Options Outstanding
	Shares Available for Grant			Number of Stock Options Outstanding			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
											(In thousands)
Balance at December 31, 2014		295,101			4,248,519		$	0.76		7.7	$	8,343
Additional authorized (unaudited)		4,708,447
Granted (unaudited)		(1,911,137	)		1,911,137			5.04		—		—
Exercised (unaudited)		—			(26,555	)		0.73		—		—
Cancelled (unaudited)		121,941			(121,941	)		1.30		—		—
Balance at September 30, 2015 (unaudited)		3,214,352			6,011,160		$	2.11		7.8	$	18,755
Vested and exercisable at September 30, 2015 (unaudited)					2,911,734		$	0.82		6.5	$	12,702
Vested and expected to vest at September 30, 2015 (unaudited)					4,576,826		$	1.88		7.6	$	15,329

A summary of the Company’s stock option activity and related information is as follows:

				Options Outstanding
	Shares Available for Grant			Number of Stock Options Outstanding			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
											(in thousands)
Balance at January 1, 2013		306,097			1,907,644		$	0.71		6.3	$	28
Additional shares authorized		2,359,662
Granted		(1,190,349	)		1,190,349			0.70
Exercised		—			(1,463	)		0.68
Cancelled		372,957			(372,957	)		0.69
Balance at December 31, 2013		1,848,367			2,723,573			0.71		7.7		138
Granted		(1,642,799	)		1,642,799			0.84
Exercised		—			(28,320	)		0.73
Cancelled		89,533			(89,533	)		0.74
Balance at December 31, 2014		295,101			4,248,519		$	0.76		7.7	$	8,343
Vested and exercisable at December 31, 2013					1,360,757		$	0.71		6.4	$	67
Vested and expected to vest at December 31, 2013					2,333,655		$	0.71		7.4	$	118
Vested and exercisable at December 31, 2014					2,379,076		$	0.72		6.8	$	4,764
Vested and expected to vest at December 31, 2014					3,777,913		$	0.78		7.5	$	7,452

Schedule of Weighted-Average Assumptions Fair Value of Employee Stock Options Estimated Date of Grant Using Black-Scholes Option-Pricing Model

1,911,137 shares were granted during the nine months ended September 30, 2015.

	Nine Months Ended September 30, 2015
	(Unaudited)
Expected term (in years)		6.0
Expected volatility%		68.7	%
Risk-free interest rate%		1.8	%
Expected dividend yield%		0.0	%

The fair value of employee stock options was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted-average assumptions:

	December 31,
	2013			2014
Expected term (in years)		6.2			5.7
Expected volatility		52.4	%		50.7	%
Risk-free interest rate		1.2	%		1.8	%
Expected dividend yield		0	%		0	%

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense recognized in the Company’s condensed consolidated statements of operations is classified as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
	(Unaudited)
Research and development	$	95	$	14	$	143	$	70
Selling and marketing		16		3		26		11
General and administrative		272		41		362		181
Total stock-based compensation expense	$	383	$	58	$	531	$	262

Total stock-based compensation expense recognized in the Company’s statements of operations is classified as follows (in thousands):

	Year Ended December 31,
	2013		2014
Research and development	$	29	$	85
Selling and marketing		9		15
General and administrative		181		218
Total stock-based compensation expense	$	219	$	318