Shareholders’ Equity (Tables)

6 Months Ended

Jun. 30, 2015

Summary of Share-based Compensation Expense

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



	Three Months Ended June 30,				Six Months Ended June 30,
	2015		2014		2015		2014
Research and development:
Stock options	$	413	$	36	$	972	$	44
Restricted stock	735		146		1,213		505
Warrants	14		—		25		—
Research and development share-based compensation expense	1,162		182		2,210		549
General and administrative:
Stock options	918		266		1,507		289
Restricted stock	1,596		1,706		3,174		4,014
Warrants	204		—		391		—
General and administrative share-based compensation expense	2,718		1,972		5,072		4,303
Total share-based compensation expense included in expenses	$	3,880	$	2,154	$	7,282	$	4,852

Summary of Stock Option Activity and Related Data

The Company’s stock option and 2013 Equity Plan restricted stock award activity for the six months ended June 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	674,535		$19.40
Exercised	(7,500	)	$7.63
Forfeited	(7,500	)	$7.63
Outstanding at June 30, 2015	1,278,435		$14.76	9.29 years	$	12,460,770
Vested and expected to vest at June 30, 2015	1,278,435		$14.76	9.29 years	$	12,460,770
Exercisable at June 30, 2015	156,607		$10.68	8.82 years	$	2,165,911

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:



	Six Months Ended June 30,
	2015		2014
Volatility	173	%	187	%
Expected life (years)	6.70 years		6.78 years
Risk-free interest rate	1.7	%	2.2	%
Dividend yield	—	%	—	%

Summary of restricted stock activity

The Company’s RSA activity for the six months ended June 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	(170,726	)	$	12.57
Unvested at June 30, 2015	1,108,281		$	12.90