Warrants

9 Months Ended

Sep. 30, 2016

Equity [Abstract]

Warrants

Warrants 

As of September 30, 2016 the following warrants for common stock were issued and outstanding:

Issue date	Expiration date	Exercise price		Number of warrants outstanding
November 21, 2012	November 21, 2017	$	7.86	695,383

During the three months ended September 30, 2016, no warrants were exercised. During the nine months ended September 30, 2016, warrants for 419,244 shares of the Company's common stock were exercised via cashless exercises and 313,756 shares were exercised for cash generating proceeds of $2.1 million. The Company issued a total of 603,545 shares of common stock for the same period. During the three and nine months endedSeptember 30, 2015, warrants for 844,760 and 1,037,330 shares of the Company's common stock were exercised via cashless exercises and the Company issued a total of 660,680 and 809,498 shares of common stock, respectively.

Stockholders' Equity

Share-based Compensation

Total share-based compensation expense by condensed consolidated statements of operations classification is presented below (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Research and development expense	$	1,361	$	959	$	4,297	$	2,698
General and administrative expense	1,399		1,845		3,789		5,214
	$	2,760	$	2,804	$	8,086	$	7,912

During the three months ended September 30, 2016, no shares were issued pursuant to stock option exercises. During the three months ended September 30, 2015, 7,294 shares were issued pursuant to stock option exercises, generating net proceeds of $0.2 million. During the nine months endedSeptember 30, 2016 and 2015, 22,132 and 34,210 shares were issued pursuant to stock option exercises generating net proceeds of $0.2 million and $0.5 million, respectively.