Stock Option Plans (Tables)

9 Months Ended

Sep. 30, 2016

Schedule of Activity under Stock Option Plan

Activity under the Company’s stock option plan is set forth below:


							Options Outstanding
	Options Available for Grant			Options Outstanding			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (years)		Aggregate Intrinsic Value
											(in thousands)
Balances at December 31, 2015		147,219			833,178		$	1.33		8.56
Additional options authorized		1,697,088			—
Options granted		(774,479	)		774,479			5.55
Options exercised		—			(111,501	)		1.28

Balances at September 30, 2016		1,069,828			1,496,156			3.52		8.65	$	26,347

Options exercisable – September 30, 2016					338,784			1.97		7.26	$	6,490

Options vested and expected to vest – September 30, 2016					1,481,620			3.51		8.64	$	26,100

Schedule of Stock-based Compensation Expense for Employees and Non-employees for Stock Options and the 2016 ESPP

Total stock-based compensation expense recognized for both employees and non-employees for stock options and the 2016 ESPP was as follows (in thousands):


	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Research and development	$	285	$	8	$	360	$	24
General and administrative		163		14		250		38

Total stock-based compensation expense	$	448	$	22	$	610	$	62

Employee and Director [Member]

Schedule of Grant-date Fair Value of Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions

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


	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016			2015
Expected term (in years)		4.16 - 5.70			—		4.16 - 5.94			5.89
Expected volatility		62.8	%		—		62.5% - 64.8	%		59.8	%
Risk-free interest rate		1.28	%		—		1.27% - 1.38	%		1.57	%
Dividend yield		—			—		—			—

Non-employees [Member]

Schedule of Grant-date Fair Value of Stock Option Awards Using Black-Scholes Option Pricing Model Assumptions

The fair value of the stock options granted is calculated at each reporting date using the Black-Scholes option-pricing model with the following assumptions:


	Three Months Ended September 30,					Nine Months Ended September 30,
	2016			2015		2016			2015
Expected term (in years)		5.70 - 7.04			—		5.70 - 9.93			—
Expected volatility		62.8	%		—		62.5% - 62.8	%		—
Risk-free interest rate		1.29	%		—		1.29% - 1.36	%		—
Dividend yield		—			—		—			—