STOCKHOLDERS’ EQUITY

Authorized Stock

On December 13, 2010, we filed the Certificate of Designation of Rights, Preferences and Privileges of Series B Junior Participating Preferred Stock with the Delaware Secretary of State which authorized 1.5 million shares to be designated as Series B Junior Participating Preferred Stock. On June 13, 2011, our stockholders approved an amendment to our Certificate of Incorporation to increase the authorized number of shares of our common stock from 100 million shares to 175 million shares. The amendment was filed with the Delaware Secretary of State on June 24, 2011. As of December 31, 2017, we also had five million shares of preferred stock authorized, of which 1.5 million shares were designated as Series B Junior Participating Preferred Stock and 2,000 shares were designated as Series E Convertible Voting Preferred Stock.

Stockholder Rights Agreement

On November 29, 2010, our Board of Directors approved a stockholder rights agreement (the "Stockholder Rights Agreement"), effective December 13, 2010. A stockholder rights agreement is designed to deter coercive, unfair, or inadequate takeovers and other abusive tactics that might be used in an attempt to gain control of our company. A stockholder rights agreement will not prevent takeovers at a full and fair price, but rather is designed to deter coercive takeover tactics and to encourage anyone attempting to acquire our company to first negotiate with our Board of Directors.

Under the terms of the Stockholder Rights Agreement, and subject to the exception noted below, the rights to purchase units of our Senior B Junior Participating Preferred Stock become exercisable upon the earlier of 10 days after a person or group of affiliated or associated persons has acquired 15% (or 20% in the case of a designated holder) or more of the outstanding shares of our common stock or 10 business days after a tender offer has commenced that would result in a person or group beneficially owning 15% (or 20% in the case of a designated holder) or more of our outstanding common stock. Five days after the rights become exercisable, each right, other than rights held by the person or group of affiliated persons whose acquisition of more than 15% of our outstanding common stock caused the rights to become exercisable (subject to the exception noted below), will entitle its holder to buy, in lieu of shares of Series B Junior Participating Preferred Stock, a number of shares of our common stock having a market value of two times the exercise price of the rights. After the rights become exercisable, if we are a party to certain merger or business combination transactions or transfers 50% or more of our assets or earnings power (as defined in the Stockholder Rights Agreement), each right will entitle its holder to buy a number of shares of common stock of the acquiring or surviving entity having a market value of twice the exercise price of the right. These rights could delay or discourage someone from acquiring our company, even if doing so would potentially benefit our stockholders.

In October 2017, we amended the Stockholder Rights Agreement to treat BlackRock Inc. and its affiliates as a "designated holder" and to our knowledge we currently have no stockholders who own 15% or more of the outstanding shares of our common stock other than BlackRock Inc. who reported beneficial ownership of approximately 15.9% as of December 31, 2017.

The Stockholder Rights Agreement expires by its terms on December 13, 2020.

Series E Preferred Stock

In September 2003, we received gross cash proceeds of $20 million in exchange for the issuance of 2,000 shares of our Series E Convertible Voting Preferred Stock, convertible into four million shares of common stock. As of December 31, 2017 and 2016, no shares of Series E Preferred Stock were outstanding.

In June 2016, our then 20 outstanding shares of Series E convertible voting preferred stock were converted (at the election of the preferred stockholders) into an aggregate of 40,000 common shares and a $6 thousand dividend in arrears was paid upon this conversion.

Common Stock Issuable

As of December 31, 2017, 15.9 million shares of our common stock were issuable upon conversion, or exercise of rights granted (regardless of whether in or out-of-the-money), as summarized below:



2018 Convertible Notes	3,854,959
Exercise of vested employee stock options (unvested of 2,241,699 - see Note 6)	11,615,514
Exercise of vested warrants	445,000
Total common shares issuable	15,915,473

Warrant Activity

We typically issue warrants to purchase shares of our common stock to investors as part of a financing transaction or in connection with services rendered by placement agents or consultants. Our outstanding warrants expire on varying dates through December 2020. A summary of warrant activity is as follows:



	Number of Shares	Weighted Average Exercise Price
Outstanding — December 31, 2014	445,000	$	6.39
Granted	—	—
Outstanding — December 31, 2015	445,000	$	6.78
Granted	—	—
Outstanding — December 31, 2016	445,000	$	6.78
Granted	—	—
Outstanding — December 31, 2017	445,000	$	6.78
Exercisable — December 31, 2017	445,000	$	6.78

Sale of Common Stock Under ATM Agreements

In December 2015, we entered into a collective at-market-issuance sales agreement with FBR Capital Markets & Co., MLV & Co. LLC, and H.C. Wainwright & Co., LLC. (“December 2015 ATM Agreement”). The December 2015 ATM Agreement allowed us to raise gross proceeds of up to $100 million from the sale of our common stock through these brokers under our shelf registration statement on Form S-3 (declared effective by the SEC on February 3, 2016; File No. 333-208760) (the "Registration Statement"). As of July 31, 2017, we fully utilized this ATM facility.

In August 2017, we entered into a collective at-market-issuance sales agreement with H.C. Wainwright & Co., LLC., FBR Capital Markets & Co., and MLV & Co. LLC (the "August 2017 ATM Agreement"). The August 2017 ATM Agreement allows us to raise gross proceeds of up to $150 million from the sale of our common stock through these brokers under the Registration Statement. As of December 31, 2017, approximately $43.9 million remained available for sale under this ATM facility.

We sold and issued shares of our common stock under both the December 2015 and August 2017 ATM Agreements, summarized as follows:



	No. of Common Shares Issued	Proceeds Received (Net of Broker Commissions and Fees )
Common shares issued pursuant to the December 2015 ATM Agreement during the year ended December 31, 2016	10,890,915	$	73,869
Common shares issued pursuant to the December 2015 ATM Agreement between July 1, 2017 and July 31, 2017	3,243,882	$	23,745
Common shares issued pursuant to the August 2017 ATM Agreement between August 1, 2017 and December 31, 2017	10,314,250	$	104,527