Annual report pursuant to Section 13 and 15(d)

Stock-Based Payments (Tables)

Stock-Based Payments (Tables)

12 Months Ended

Dec. 31, 2018

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of status of stock options and changes during the period

A summary of the status of stock options as of December 31, 2018 and December 31, 2017 and changes during the year ended December 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		1,548,252			10.37
Exercised		(214,532	)		2.92
Cancelled		(447,745	)		10.96
Outstanding at December 31, 2018		3,732,643		$	9.88		7.9	$	1,694
Exercisable at December 31, 2018		1,366,881		$	8.34		6.9	$	1,569

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:

	Year Ended December 31,
	2018			2017			2016
Weighted-average risk-free interest rate		2.56	%		2.07	%		1.36	%
Expected dividend yield		—	%		—	%		—	%
Expected option term (in years)		6.04			6.05			5.98
Volatility		90.26	%		87.83	%		85.39	%

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 statements of operations:

	Year Ended December 31,
	2018		2017		2016
Research and development	$	2,412	$	1,666	$	2,980
General and administrative		4,198		2,753		1,254
Total stock-based compensation expense	$	6,610	$	4,419	$	4,234