Warrants (Tables)
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12 Months Ended |
Dec. 31, 2015 |
Warrants and Rights Note Disclosure [Abstract] |
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Schedule of Warrant Activity |
The following is a summary of warrant activity for the years ended December 31, 2015 and 2014 (in thousands): | | | | | | | | | | | | | | | | | | | | | | | March 2015 Warrants | | September 2013 Warrants | | December 2012 Warrants | | April 2011 Warrants | | Other Warrant Issuances | | Consultant and Oxford Warrants | | Total | Outstanding, January 1, 2014 | — |
| | 6,442 |
| | 4,917 |
| | 1,158 |
| | 1,444 |
| | 889 |
| | 14,850 |
| Granted | — |
| | — |
| | — |
| | — |
| | — |
| | 300 |
| | 300 |
| Exercised | — |
| | (2,469 | ) | | (1,886 | ) | | (543 | ) | | (327 | ) | | (469 | ) | | (5,694 | ) | Expired | — |
| | — |
| | — |
| | — |
| | (916 | ) | | — |
| | (916 | ) | Outstanding, December 31, 2014 | — |
| | 3,973 |
| | 3,031 |
| | 615 |
| | 201 |
| | 720 |
| | 8,540 |
| Granted | 14,006 |
| | — |
| | — |
| | — |
| | — |
| | — |
| | 14,006 |
| Expired | — |
| | — |
| | — |
| | — |
| | — |
| | (238 | ) | | (238 | ) | Outstanding, December 31, 2015 | 14,006 |
| | 3,973 |
| | 3,031 |
| | 615 |
| | 201 |
| | 482 |
| | 22,308 |
| Expiration | March 2020 | | September 2018 | | December 2017 | | April 2017 | | Varies 2014-2016 | | Varies 2014-2020 | | |
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Fair Value of Warrants is Estimated Using Black-Scholes Option Pricing Model |
The fair value of the warrants is estimated using an appropriate pricing model with the following inputs: | | | | | | | | | | | | | | | | | | | | | | | | | | As of December 31, 2015 | | March 2015 Warrants | | September 2013 Warrants | | December 2012 Warrants | | April 2011 Warrants | | March 2011 Warrants | | March 2010 Warrants | Strike price | $ | 2.08 |
| | $ | 2.50 |
| | $ | 1.83 |
| | $ | 0.65 |
| | $ | 0.65 |
| | $ | 2.02 |
| Expected term (years) | 4.22 |
| | 2.72 |
| | 1.98 |
| | 1.31 |
| | 0.18 |
| | 0.24 |
| Volatility % | 75.85 | % | | 74.70 | % | | 76.37 | % | | 65.60 | % | | 47.98 | % | | 71.41 | % | Risk-free rate % | 1.58 | % | | 1.24 | % | | 1.05 | % | | 0.77 | % | | — | % | | — | % |
| | | | | | | | | | | | | | | | | | | | | | As of December 31, 2014 | | September 2013 Warrants | | December 2012 Warrants | | April 2011 Warrants | | March 2011 Warrants | | March 2010 Warrants | Strike price | $ | 2.50 |
| | $ | 1.90 |
| | $ | 0.65 |
| | $ | 0.65 |
| | $ | 2.15 |
| Expected term (years) | 3.72 |
| | 2.98 |
| | 2.31 |
| | 1.18 |
| | 1.24 |
| Volatility % | 75.60 | % | | 76.85 | % | | 78.24 | % | | 77.38 | % | | 77.12 | % | Risk-free rate % | 1.30 | % | | 1.09 | % | | 0.80 | % | | 0.32 | % | | 0.35 | % |
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Changes in Fair Value of Warrant Liability |
The changes in fair value of the warrant liability for the years ended December 31, 2015 and 2014 were as follows (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | March 2015 Warrants | | September 2013 Warrants | | December 2012 Warrants | | April 2011 Warrants | | Other Warrant Issuances | | Total | Warrant liability, January 1, 2014 | $ | — |
| | $ | 22,950 |
| | $ | 18,060 |
| | $ | 5,069 |
| | $ | 2,886 |
| | $ | 48,965 |
| Fair value of warrants granted | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| Fair value of warrants exercised | — |
| | (12,713 | ) | | (10,086 | ) | | (2,906 | ) | | (1,321 | ) | | (27,026 | ) | Change in fair value of warrants | — |
| | (7,677 | ) | | (5,947 | ) | | (1,538 | ) | | (1,394 | ) | | (16,556 | ) | Warrant liability, December 31, 2014 | — |
| | 2,560 |
| | 2,027 |
| | 625 |
| | 171 |
| | 5,383 |
| Fair value of warrants granted | 10,296 |
| | — |
| | — |
| | — |
| | — |
| | 10,296 |
| Fair value of warrants exercised | — |
| | — |
| | — |
| | — |
| | — |
| | — |
| Change in fair value of warrants | 41 |
| | (627 | ) | | (462 | ) | | (88 | ) | | (25 | ) | | (1,161 | ) | Warrant liability, December 31, 2015 | $ | 10,337 |
| | $ | 1,933 |
| | $ | 1,565 |
| | $ | 537 |
| | $ | 146 |
| | $ | 14,518 |
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