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STOCKHOLDERS' EQUITY (Common Stock, 2018 Purchase Agreement and LP Purchase Agreement) (Details) - USD ($) |  |  |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Jun. 26, 2020 | Apr. 08, 2020 | Mar. 26, 2020 | Sep. 07, 2018 | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 20, 2018 | Dec. 19, 2018
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Common stock, shares authorized (in shares) |  |  |  |  | 150,000,000 | 150,000,000 | 250,000,000 | 150,000,000
Proceeds from exercise of warrants |  |  |  |  | $ 400,000 |  |  |
Proceeds upon issuance of common stock from exercise of stock options |  |  |  |  | 3,000 |  |  |
Issuance of common stock in connection with at the market offering, net of issuance costs |  |  |  |  | $ 14,947,000 |  |  |
Shares issued (in shares) |  |  |  |  | 22,708,442 | 17,576,916 |  |
Common stock, shares outstanding (in shares) |  |  |  |  | 22,708,442 | 17,576,916 |  |
Issuance of common stock, net of issuance costs |  |  |  |  | $ 16,207,000 | $ 8,929,000 |  |
Issuance of common stock for consulting services |  |  |  |  | $ 150,000 |  |  |
Conversion of debt into stock |  |  |  |  |  | $ 2,176,000 |  |
Common Stock [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Proceeds upon issuance of common stock from exercise of warrants (in shares) |  |  |  |  | 74,000 |  |  |
Proceeds upon issuance of common stock from exercise of stock options |  |  |  |  | $ 3,000 |  |  |
Proceeds upon issuance of common stock from exercise of stock options (in shares) |  |  |  |  | 1,379 |  |  |
Common stock issued in connection with the conversion of convertible notes |  |  |  |  |  | 3,980,145 |  |
Issuance of common stock in connection with at the market offering, net of issuance costs |  |  |  |  | $ 45,000 |  |  |
Shares issued (in shares) |  |  |  |  | 4,501,000 |  |  |
Issuance of common stock for consulting services (in shares) |  |  |  |  | 55,147 |  |  |
Issuance of common stock for consulting services |  |  |  |  | $ 200,000 |  |  |
Number of shares converted from debt instrument (in shares) |  |  |  |  |  | 3,908,145 |  |
Common Stock [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Common stock issued for exercise of warrants |  |  |  |  | 74,000 |  |  |
Warrant exercises in period |  |  |  |  | 74,000 |  |  |
Proceeds from exercise of warrants |  |  |  |  | $ 400,000 |  |  |
Proceeds upon issuance of common stock from exercise of stock options (in shares) |  |  |  |  | 1,379 |  |  |
Conversion of debt into stock |  |  |  |  |  | $ 2,200,000 |  |
Preferred Class B |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Conversion price (in dollars per share) |  |  |  |  | $ 0.40 |  |  |
Lincoln Park [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Issuance of common stock in connection with at the market offering, net of issuance costs |  |  |  | $ 10,000,000 |  |  |  |
Shares issued (in shares) | 4,500,000 |  |  |  |  |  |  |
Shares issued (in shares) |  |  |  |  | 500,000 | 2,960,000 |  |
Shares sold in offering (in shares) |  |  |  |  |  | 1,040,654 |  |
Issuance of common stock, net of issuance costs |  |  |  |  |  | $ 1,400,000 |  |
LP 2020 Purchase Agreement [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Issuance of common stock, net of issuance costs |  |  |  |  | $ 8,800,000 |  |  |
LP 2020 Purchase Agreement [Member] | Lincoln Park [Member] |  |  |  |  |  |  |  |
Class of Stock [Line Items] |  |  |  |  |  |  |  |
Issuance of common stock in connection with at the market offering, net of issuance costs |  |  | $ 10,000,000 |  |  |  |  |
Shares issued (in shares) |  | 1,770,000 | 250,000 |  |  |  |  |
Shares sold in offering (in shares) |  |  |  |  | 500,000 | 4,480,000 |  |
Issuance of common stock, net of issuance costs |  |  |  |  | $ 1,300,000 | $ 7,500,000 |  |

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