| Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block] |
The following table summarizes information with regard to outstanding warrants to purchase common stock as of December 31, 2013.
| Offering | | Number of Shares
Issuable Upon
Exercise of
Outstanding
Warrants | | Exercise
Price | | Expiration Date | | | | | | | | | | | | | February 2013 Public Offering (1) | | 11,000,000 | | $ | 0.50 | | February 20, 2018 | | | February 2013 Public Offering (1) (2) | | 5,500,000 | | $ | 0.50 | | February 20, 2014 | | | February 2013 Public Offering – Placement Agents | | 770,000 | | $ | 0.625 | | February 4, 2018 | | | November 2012 Private Placement | | 1,000,000 | | $ | 1.25 | | November 2, 2017 | | | June 2012 Public Offering | | 2,981,440 | | $ | 1.25 | | June 13, 2017 | | | December 2011 Underwritten Offering | | 9,248,334 | | $ | 0.60 | | December 6, 2016 | | | April 2011 Private Placement | | 6,058,811 | | $ | 0.75 | | March 31, 2016 | | | Legacy warrants (1) | | 27,310 | | $ | 0.50 | | July 27, 2015 | | | Legacy warrants | | 105,040 | | $ | 16.065 | | July 27, 2015 | | | Legacy warrants | | 91,524 | | $ | 99.45-100.98 | | December 31, 2015 | | | | | | | | | | | | | Total | | 36,782,459 | | | | | | |
| (1) | The exercise prices of these warrants are subject to adjustment for “down-rounds” and the warrants have been accounted for as derivative instruments as described in Note 3. | | (2) | On February 20, 2014, warrants to purchase 5,500,000 shares of common stock expired unexercised (see Note 17). |
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| Reserved For Future Issuance Upon Exercise Of Stock Options And Warrants Or Conversion Of Debt [Table Text Block] |
The following shares were reserved for future issuance upon exercise of stock options and warrants:
| | | December 31, | | | | | 2013 | | 2012 | | | | | | | | | | Warrants | | 36,782,459 | | 21,512,459 | | | Stock options | | 12,693,166 | | 6,439,188 | | | | | | | | | | Total number of shares reserved for future issuance | | 49,475,625 | | 27,951,647 | |
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