Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2020

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,
	2020		2019
Research and development	$	532	$	402
General and administrative		816		679
Total stock-based compensation expense	$	1,348	$	1,081

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,
	2020			2019
Equity Incentive Plans
Expected term (in years)		6.02			6.03
Expected volatility		74	%		82	%
Risk-free interest		1.45	%		2.57	%
Dividend yield		0	%		0	%
2016 ESPP
Expected term (in years)		0.50			0.49
Expected volatility		53	%		66	%
Risk-free interest		1.49	%		2.55	%
Dividend yield		0	%		0	%