Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense related to the Company’s equity incentive plans and 2016 ESPP was as follows (in thousands):

	Three Months Ended				Nine Months Ended
	September 30,				September 30,
	2017		2016		2017		2016
Research and development	$	277	$	190	$	672	$	400
General and administrative		451		244		1,122		563
Total stock-based compensation expense	$	728	$	434	$	1,794	$	963

Schedule of Estimated Fair Value of Stock Options Granted

The following table summarizes the weighted-average Black-Scholes option pricing model assumptions used to estimate the fair value of stock options granted under the equity incentive plans and the shares purchasable under the 2016 ESPP during the periods presented:

	Three Months Ended						Nine Months Ended
	September 30,						September 30,
	2017			2016			2017			2016
Equity Incentive Plans
Expected term		5.82			6.07			5.91			5.99
Expected volatility		85	%		81	%		86	%		87	%
Risk-free interest		1.88	%		1.16	%		1.99	%		1.28	%
Dividend yield		0	%		0	%		0	%		0	%
2016 ESPP
Expected term		0.50			0.50			0.50			0.45
Expected volatility		79	%		81	%		79	%		82	%
Risk-free interest		1.23	%		0.57	%		0.90	%		0.49	%
Dividend yield		0	%		0	%		0	%		0	%