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                2015 Warrants exercise price per share 
               
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             |  |  |  |  |  |  |  |  | $ | 41.25 |  |  | 
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                Net tangible book value (deficit) per share of as March 31, 2020 
               
             | 
             |  |  | $ | 0.86 |  |  |  |  |  |  |  |  | 
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                Increase in net tangible book value per share attributable to exercise of 2015 Warrants 
               
             | 
             |  |  | $ | 0.73 |  |  |  |  |  |  |  |  | 
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                As adjusted, net tangible book value (deficit) per share as of March 31, 2020, after giving 
                 
            effect to exercise of 2015 Warrants  | 
             |  |  |  |  |  |  |  |  | $ | 1.59 |  |  | 
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                Dilution per share to new investors purchasing our common stock, after giving effect to exercise of 2015 Warrants 
               
             | 
             |  |  |  |  |  |  |  |  | $ | 39.66 |  |  | 
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                May 2019 Warrants exercise price per share 
               
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             |  |  |  |  |  |  |  |  | $ | 3.52 |  |  | 
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                Net tangible book value (deficit) per share of as March 31, 2020 
               
             | 
             |  |  | $ | 0.86 |  |  |  |  |  |  |  |  | 
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                Increase in net tangible book value per share attributable to exercise of May 2019 Warrants 
               
             | 
             |  |  | $ | 0.17 |  |  |  |  |  |  |  |  | 
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                As adjusted, net tangible book value (deficit) per share as of March 31, 2020, after giving effect to exercise of May 2019 Warrants 
               
             | 
             |  |  |  |  |  |  |  |  | $ | 1.03 |  |  | 
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                Dilution per share to new investors purchasing our common stock, after giving effect to exercise of May 2019 Warrants 
               
             | 
             |  |  |  |  |  |  |  |  | $ | 2.49 |  |  | 
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                December 2019 Warrants exercise price per share 
               
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             |  |  |  |  |  |  |  |  | $ | 8.10 |  |  | 
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                Net tangible book value (deficit) per share of as March 31, 2020 
               
             | 
             |  |  | $ | 0.86 |  |  |  |  |  |  |  |  | 
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                Increase in net tangible book value per share attributable to exercise of December 2019 Warrants 
               
             | 
             |  |  | $ | 0.63 |  |  |  |  |  |  |  |  | 
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                As adjusted, net tangible book value (deficit) per share as of March 31, 2020, after giving effect to exercise of December 2019 Warrants 
               
             | 
             |  |  |  |  |  |  |  |  | $ | 1.49 |  |  | 
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                Dilution per share to new investors purchasing our common stock, after giving effect to exercise of December 2019 Warrants 
               
             | 
             |  |  |  |  |  |  |  |  | $ | 6.61 |  |  | 
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                December 2019 Placement Agent Warrants exercise price per share 
               
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             |  |  |  |  |  |  |  |  | $ | 8.44 |  |  | 
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                Net tangible book value (deficit) per share of as March 31, 2020 
               
             | 
             |  |  | $ | 0.86 |  |  |  |  |  |  |  |  | 
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                Increase in net tangible book value per share attributable to exercise of December 2019 Placement Agent Warrants 
               
             | 
             |  |  | $ | 0.07 |  |  |  |  |  |  |  |  | 
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                As adjusted, net tangible book value (deficit) per share as of March 31, 2020, after giving effect to exercise of December 2019 Placement Agent Warrants 
               
             | 
             |  |  |  |  |  |  |  |  | $ | 0.93 |  |  | 
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                Dilution per share to new investors purchasing our common stock, after giving effect to exercise of December 2019 Placement Agent Warrants 
               
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             |  |  |  |  |  |  |  |  | $ | 7.51 |  |  | 
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                Weighted-average exercise price per share 
               
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             |  |  |  |  |  |  |  |  | $ | 9.65 |  |  | 
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                Net tangible book value (deficit) per share of as March 31, 2020 
               
             | 
             |  |  | $ | 0.86 |  |  |  |  |  |  |  |  | 
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                Increase in net tangible book value per share attributable to exercise of all Registered Warrants 
               
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             |  |  | $ | 1.41 |  |  |  |  |  |  |  |  | 
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                As adjusted, net tangible book value (deficit) per share as of March 31, 2020, after giving effect to exercise of all Registered Warrants 
               
             | 
             |  |  |  |  |  |  |  |  | $ | 2.27 |  |  | 
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                Dilution per share (on a weighted-average basis) to new investors purchasing our common 
                 
            stock, after giving effect to exercise of all Registered Warrants  | 
             |  |  |  |  |  |  |  |  | $ | 7.38 |  |  | 
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