Shareholders’ Equity (Tables)

9 Months Ended

Sep. 30, 2015

Summary of Stock Option Activity and Related Data

The Company’s stock option and 2013 Equity Plan restricted stock award activity for the nine months ended September 30, 2015 and the year ended December 31, 2014 was comprised of the following:



	Outstanding Stock Options and 2013 Equity Plan Restricted Stock Awards
	Shares Underlying Stock Options and Restricted Stock Awards		Weighted-Average Exercise Price per Share	Weighted- Average Remaining Contractual Term	Aggregate Intrinsic Value
Outstanding at December 31, 2013	54,000		$6.00
Granted	567,876		$9.88
Restricted stock awards vested	(2,976	)	$0.00
Outstanding at December 31, 2014	618,900		$9.54
Granted	942,285		$23.83
Exercised	(42,535	)	$9.74
Forfeited	(24,465	)	$10.19
Outstanding at September 30, 2015	1,494,185		$18.54	9.21 years	$	15,765,631
Vested and expected to vest at September 30, 2015	1,494,185		$18.54	9.21 years	$	15,765,631
Exercisable at September 30, 2015	211,408		$10.60	8.67 years	$	3,643,505

Stock Options, Valuation Assumptions

The Company estimated the fair value of each stock option grant on the grant date using the Black-Scholes model with the following weighted-average assumptions:



	Nine Months Ended September 30,
	2015		2014
Volatility	147	%	188	%
Expected life (years)	4.91 years		6.73 years
Risk-free interest rate	1.4	%	2.2	%
Dividend yield	—	%	—	%

Summary of restricted stock activity

The Company’s RSA activity for the nine months ended September 30, 2015 and the year ended December 31, 2014 was comprised of the following:



	Number of Shares		Weighted-Average Grant Date Fair Market Value
Unvested at December 31, 2013	1,746,853		$	11.80
Granted	2,976		$	8.40
Vested	(423,693	)	$	9.18
Forfeited	(47,129	)	$	4.41
Unvested at December 31, 2014	1,279,007		$	12.86
Vested	(188,414	)	$	12.30
Unvested at September 30, 2015	1,090,593		$	12.95

Summary of Share-based Compensation Expense

Total share-based compensation expense related to all share-based awards for the three and nine months ended September 30, 2015 and 2014 was comprised of the following (in thousands):



	Three Months Ended September 30,				Nine Months Ended September 30,
	2015		2014		2015		2014
Research and development:
Stock options	$	636	$	98	$	1,609	$	142
Restricted stock	240		147		1,452		652
Warrants	15		—		40		—
Research and development share-based compensation expense	891		245		3,101		794
General and administrative:
Stock options	1,443		286		2,950		575
Restricted stock	545		1,212		3,719		5,226
Warrants	182		—		573		—
General and administrative share-based compensation expense	2,170		1,498		7,242		5,801
Total share-based compensation expense included in expenses	$	3,061	$	1,743	$	10,343	$	6,595