Stockholders' Equity

3 Months Ended

Mar. 31, 2017

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

Stockholders' Equity

Warrants 

As of March 31, 2017 the following warrants for common stock were issued and outstanding:

Issue date	Expiration date	Exercise price		Number of warrants outstanding
January 11, 2017	None	$	0.001	7,258,263
November 21, 2012	November 21, 2017	$	7.86	695,383

Refer to footnote 11 for further detail of the new warrants issued during the first quarter of 2017.

During the three months ended March 31, 2017, no warrants were exercised. During the three months ended March 31, 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.

Stockholders' Equity

Sale of Common Stock

In January 2017, the Company sold 5,002,702 million shares of its common stock at a public offering price of $5.60 per share and sold warrants to purchase up to 7,258,263 shares of its common stock at a public offering price of $5.599 per warrant share. The public offering price for the warrants was equal to the public offering price of the common stock, less the $0.001 per share exercise price of each warrant. After deducting underwriter discounts and offering expenses, the Company received net proceeds from the transaction of $66.8 million. These warrants were recorded as a component of stockholders’ equity within additional paid-in capital. Per their terms, the outstanding warrants to purchase shares of common stock may not be exercised if the holder’s ownership of the Company’s common stock would exceed 19.99 percent following such exercise. Pursuant to the terms of the financing, the Company has an effective resale registration statement on file with the SEC covering shares of common stock sold and shares of common stock issuable upon the exercise of the warrants.

Share-based Compensation

Total share-based compensation expense by operating statement classification is presented below (in thousands):

	Three Months Ended March 31,
	2017		2016
Research and development expense	$	982	$	1,458
General and administrative expense	784		1,580
	$	1,766	$	3,038

During the three months ended March 31, 2017, no shares were issued pursuant to stock option exercises. During the three months ended March 31, 2016, 20,296 shares were issued pursuant to stock option exercises, generating net proceeds of $0.2 million.