Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Company's Stock Option Activity and Related Information

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 ContractualLife (Years)		Aggregate Intrinsic Value
											(In thousands)
Balance at December 31, 2016		2,168,391			6,127,291		$	2.60		7.3	$	7,800
Additional options authorized		1,743,247			—
Options granted		(2,112,487	)		2,112,487			5.10
Options exercised		—			(230,733	)		0.84
Options cancelled		34,921			(34,921	)		2.71
Balance at June 30, 2017		1,834,072			7,974,124		$	3.31		7.7	$	25,264
Vested and exercisable at June 30, 2017					4,216,526		$	2.11		6.5	$	18,401
Vested and expected to vest at June 30, 2017					7,657,935		$	3.26		7.6	$	24,669

Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Option at Grant Date

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

	Six Months Ended June 30,
	2017		2016
Expected term (in years)		6.0		6.0
Expected volatility%		67.1%		69.7%
Risk-free interest rate%		2.1%		1.3%
Expected dividend yield%		0.0%		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 June 30,				Six Months Ended June 30,
	2017		2016		2017		2016
Research and development	$	216	$	235	$	381	$	356
Selling and marketing		72		14		123		38
General and administrative		725		440		1,278		851
Total stock-based compensation expense	$	1,013	$	689	$	1,782	$	1,245