Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 2019

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
	March 31,
	2019		2018
Research and development	$	402	$	323
General and administrative		679		512
Total stock-based compensation expense	$	1,081	$	835

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 Company’s equity incentive plans, and the shares purchasable under the 2016 ESPP during the periods presented:

	Three Months Ended
	March 31,
	2019			2018
Equity Incentive Plans
Expected term (in years)		6.03			6.01
Expected volatility		82	%		85	%
Risk-free interest		2.57	%		2.72	%
Dividend yield		0	%		0	%
2016 ESPP
Expected term (in years)		0.49			0.49
Expected volatility		66	%		69	%
Risk-free interest		2.55	%		2.00	%
Dividend yield		0	%		0	%