Quarterly report pursuant to Section 13 or 15(d)

Stock-Based Payments (Tables)

Stock-Based Payments (Tables)

6 Months Ended

Jun. 30, 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 June 30, 2018 and changes during the six months ended June 30, 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	1,282,952		10.88
Exercised	(103,057)		4.73
Cancelled	(168,417)		10.46
Outstanding at June 30, 2018	3,858,146	$	9.86	8.2	$	5,718
Exercisable at June 30, 2018	1,254,628	$	7.75	6.8	$	4,299

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 June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Weighted-average risk-free interest rate	2.79	%	1.86	%	2.47	%	2.03	%
Expected dividend yield	-	%	-	%	-	%	-	%
Expected option term (in years)	5.74		5.72		6.03		6.00
Volatility	91.16	%	91.42	%	90.37%	%	87.05	%

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 and restricted common stock granted to employees and non-employees recorded in the Company’s condensed consolidated statements of operations:


	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Research and development	$	670	$	448	$	1,235	$	778
General and administrative		1,074		708		2,205		1,262
Total stock-based compensation expense	$	1,744	$	1,156	$	3,440	$	2,040