Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Payments (Tables)

Stock-Based Payments (Tables)

3 Months Ended

Mar. 31, 2018

Summary of status of stock options and changes during the period

A summary of the status of stock options as of December 31, 2017 and March 31, 2018 and changes during the three months ended March 31, 2018 is presented below:


					Aggregate
		Weighted		Remaining	Intrinsic
		Average		Contractual	Value
	Shares	Exercise Price		Life (in years)	(in thousands)
Outstanding at December 31, 2017	2,846,668	$	9.25	8.2	$	5,713
Granted	1,101,550		10.61
Exercised	(74,982)		3.23
Cancelled	(120,211)		10.14
Outstanding at March 31, 2018	3,753,025	$	9.74	8.5	$	12,930
Exercisable at March 31, 2018	1,128,846	$	7.29	7.2	$	6,556

Schedule of weighted-average assumptions used in Black-Scholes option-pricing model

The fair value of each stock option granted was estimated on the date of grant using the Black-Scholes option-pricing model based on the following weighted-average assumptions:


	Three Months Ended March 31,
	2018		2017
Weighted-average risk-free interest rate	2.41	%	2.07	%
Expected dividend yield	-	%	-	%
Expected option term	6.08		6.07
Volatility	90.2%	%	86.14	%

Summary of stock-based compensation expense for stock options granted to employee and non-employees

The following table summarizes the stock-based compensation expense for stock options granted to employees and non-employees recorded in the Company’s statements of operations (in thousands):


	Three Months Ended March 31,
	2018		2017
Research and development	$	565	$	330
General and administrative		1,131		554
Total stock-based compensation expense	$	1,696	$	884