Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2014

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Total stock-based compensation expense related to all of the Company’s share-based awards to employees, directors and consultants recognized during the years ended December 31, 2014, 2013 and 2012, was comprised of the following:


	Years Ended December 31,
	2014		2013		2012
Research and development	$	1,842,828	$	132,543	$	111,206
General and administrative		2,001,050		258,850		183,900

Total share-based compensation expense	$	3,843,878	$	391,393	$	295,106

Weighted-Average Assumptions Used for Calculating Value of Options Granted

The following table describes the weighted-average assumptions used for calculating the value of options granted during the years ended December 31, 2014, 2013 and 2012:


	2014			2013			2012
Dividend yield		0	%		0	%		0	%
Expected volatility		80.0	%		80.0	%		79.7	%
Weighted-average risk-free interest rate		2.0	%		2.2	%		1.2	%
Expected term (in years)		6.3			6.2			6.3

Stock Option Activity

Information regarding the stock options activity including with respect to grants to employees, directors and consultants as of December 31, 2014, and changes during the period then ended, are summarized as follows:


	Number of Shares			Weighted- Average Exercise Price		Aggregate Intrinsic Value		Weighted- Average Contractual Life
Outstanding at December 31, 2013 (audited)		1,400,125		$	1.98	$	—		5.3 years
Options granted		1,108,000		$	16.50	$	—		9.5 years
Options exercised		(247,165	)	$	0.66	$	—		0.5 year
Options canceled or expired		(27,500	)	$	12.34	$	—		6.9 year

Outstanding at December 31, 2014		2,233,460		$	9.20	$	18,867,087		7.3 years

Vested or expected to vest at December 31, 2014		2,233,460		$	9.20	$	—

Exercisable at December 31, 2014		1,324,552		$	5.10	$	16,625,120		5.9 years