STOCKHOLDERS’ DEFICIT - Reserve Shares of Common Stock (Details) - shares |
Dec. 31, 2019 |
Dec. 31, 2018 |
|---|---|---|
| Class of Stock [Line Items] | ||
| Total common shares reserved for future issuance (in shares) | 25,141,814 | 12,981,599 |
| Outstanding stock options | ||
| Class of Stock [Line Items] | ||
| Total common shares reserved for future issuance (in shares) | 8,781,615 | 7,117,002 |
| Warrants to purchase common stock | ||
| Class of Stock [Line Items] | ||
| Total common shares reserved for future issuance (in shares) | 14,040,452 | 1,914,316 |
| Shares issuable upon conversion of convertible debt | ||
| Class of Stock [Line Items] | ||
| Total common shares reserved for future issuance (in shares) | 1,217,008 | 1,720,224 |
| For possible future issuance under the Omnibus Plan | ||
| Class of Stock [Line Items] | ||
| Total common shares reserved for future issuance (in shares) | 1,102,739 | 2,230,057 |