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Warrants | 3 Months Ended
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Mar. 31, 2019
Warrants and Rights Note Disclosure [Abstract] |
Warrants | 7. WARRANTS The Company has warrants to purchase its common stock outstanding as of March 31, 2019, as follows:
Issued |  | Classification |  |  | Warrants Outstanding |  |  | Exercise Price |  |  | Expiration |
September 2016 |  |  | Liability |  |  |  | 508,714 |  |  | $ | 2.25 |  |  |  | November 2021 |
March 2015 |  |  | Equity |  |  |  | 3,699 |  |  |  | 9.75 |  |  |  | March 2025 |
July 2014 |  |  | Equity |  |  |  | 6,566 |  |  |  | 7.99 |  |  |  | July 2024 |
July 2012 |  |  | Equity |  |  |  | 52,046 |  |  |  | 0.01 |  |  |  | July 2022 |

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