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CONVERTIBLE NOTES - 2020 Convertible Notes (Details) - USD ($) $ in Thousands | 1 Months Ended | 3 Months Ended | 12 Months Ended
--- | --- | --- | ---
Jan. 31, 2020 | Mar. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Debt Instrument [Line Items] |  |  |  |
Recognition of beneficial conversion feature related to convertible notes |  | $ 1,126 | $ 1,629 |
Exchange Transaction |  |  |  |
Deemed dividend to preferred stockholders |  |  | $ 9,484 | $ 5,353
Convertible promissory notes |  |  |  |
Exchange Transaction |  |  |  |
Fair value of convertible debt | $ 15,400 |  |  |
Redemption price as percentage price of qualified financing |  |  | 85.00% |
Convertible promissory notes | January 2020 Preferred Stock Warrants |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Warrants issued |  |  | 9,338,642 |
Warrant liabilities |  |  | $ 2,000 |
Convertible promissory notes | Q4 2020 Preferred Stock Warrants |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Warrants issued |  |  | 4,620,018 |
Convertible promissory notes | January 2020 Convertible Notes |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Proceeds from loan | 14,300 |  |  |
Proceeds from related parties | 13,700 |  |  |
Debt issuance costs | $ 200 |  |  |
Expected life of notes |  |  | 6 months |
Maturity date, extension period |  |  | 6 months |
Exchange Transaction |  |  |  |
Fair value of convertible debt |  |  | $ 15,400 |
Fair value of warrants |  |  | 2,000 |
Fair value of preferred stock |  |  | 29,800 |
Cash paid in exchange transaction |  |  | 14,100 |
Carrying value of preferred and common equity exchange |  |  | 40,400 |
Effect of exchange transaction |  |  | 7,300 |
Deemed dividend to preferred stockholders |  |  | 9,500 | 5,400
Derivative liability |  |  | 2,700 | $ 400
Convertible promissory notes | Q4 2020 Convertible Notes |  |  |  |
Debt Instrument [Line Items] |  |  |  |
Proceeds from loan |  |  | 19,000 |
Proceeds from related parties |  |  | 7,900 |
Warrant liabilities |  |  | 1,600 |
Recognition of beneficial conversion feature related to convertible notes |  |  | $ 1,600 |

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