SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details)
 3 Months Ended 6 Months Ended
Jun. 30, 2020
USD ($)
$ / shares
shares
May 04, 2020
USD ($)
$ / shares
shares
Apr. 29, 2020
USD ($)
$ / shares
shares
Feb. 06, 2020
$ / shares
Dec. 26, 2019
shares
Dec. 19, 2019
shares
Apr. 29, 2019
USD ($)
$ / shares
shares
Apr. 25, 2019
$ / shares
shares
Mar. 18, 2019
USD ($)
$ / shares
shares
Jul. 13, 2018
USD ($)
shares
Jun. 30, 2020
USD ($)
$ / shares
shares
Jun. 30, 2019
USD ($)
shares
Mar. 31, 2019
shares
Jun. 30, 2020
USD ($)
$ / shares
segment
shares
Jun. 30, 2019
USD ($)
shares
Jul. 22, 2020
USD ($)
Feb. 12, 2020
$ / shares
Dec. 31, 2019
$ / shares
Significant Accounting Policies Disclosure [Line Items]                                    
Sale of stock, shelf registration maximum equity offering price | $                   $ 175,000,000                
Sale of stock, stockholders aggregate shares available-for-sale (in shares)                   13,990,403                
Sale of stock, shares issuable upon exercise of warrant (in shares)                   2,051,771                
Number of shares issued in transaction (in shares)             4,318,272   4,181,068                  
Number of securities called by each warrant (in shares)               3,897,010                    
Shares issued, price per share (in usd per share) | $ / shares             $ 2.025   $ 2.33                  
Proceeds from issuance of common stock | $             $ 7,900,000   $ 9,700,000                  
Warrant term               5 years                    
Exercise price of warrants or rights (in usd per share) | $ / shares     $ 0.10         $ 2.13                    
Common stock, par or stated value per share (in dollars per share) | $ / shares $ 0.0001     $ 0.0001             $ 0.0001     $ 0.0001       $ 0.0001
Restriction period               45 days                    
Purchase price of each additional warrant (in dollars per share) | $ / shares               $ 0.125                    
Exercise commencement period               6 months                    
Proceeds from issuance of common stock and warrants | $     $ 1,200,000                     $ 0 $ 20,706,919      
Issuance of common stock and warrants (in shares)     12,230,418                              
Number of shares issued per warrant (in shares)           1.2                        
Preferred stock, par or stated value per share (in dollars per share) | $ / shares $ 0.0001   $ 0.0001               $ 0.0001     $ 0.0001       $ 0.0001
Proceeds from issuance of preferred stock and warrants | $   $ 22,600,000                       $ 22,560,994 0      
Proceeds from issuance of preferred stock and warrants, net. | $   $ 19,200,000                                
Exercise of warrants (in shares)         3,593,714.4           1,847,309     1,847,309        
Warrants, accumulated gross unrealized gain | $ $ 1,729,200                   $ 1,729,200     $ 1,729,200        
Change in fair value of warrant liabilities | $                     1,058,700 $ 1,812,800   2,637,500 2,669,800      
Warrant inducement expense | $                     6,467,048 0   7,157,887 0      
General and administrative expense | $                     5,659,721 3,049,711   $ 7,329,528 $ 6,164,206      
Antidilutive securities excluded from computation of earnings per share (in shares)                           53,955,496 24,542,552      
Number of operating segments | segment                           1        
Patent Costs                                    
Significant Accounting Policies Disclosure [Line Items]                                    
General and administrative expense | $                     $ 108,000 $ 126,000   $ 193,000 $ 287,000      
Short-term Warrants                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Number of securities called by each warrant (in shares)                 4,181,068                  
Warrant term                 1 year                  
Exercise price of warrants or rights (in usd per share) | $ / shares     $ 0.10           $ 4.00               $ 0.10  
Extension period       6 months                            
Short-term Warrants | Measurement Input, Exercise Price                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Warrants and rights outstanding, measurement input | $ / shares 0.10                   0.10     0.10        
Long-term Warrants                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Number of securities called by each warrant (in shares)                 2,508,634                  
Warrant term                 5 years                  
Exercise price of warrants or rights (in usd per share) | $ / shares                 $ 2.56                  
Long-term Warrants | Measurement Input, Exercise Price                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Warrants and rights outstanding, measurement input | $ / shares 0.10                   0.10     0.10        
Warrant                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Exercise price of warrants or rights (in usd per share) | $ / shares             $ 2.13                      
Number of securities called by warrants or rights (in shares) 1,539,424       2,994,762 5,441,023 4,318,272       1,539,424     1,539,424        
Placement Agent Warrants                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Warrant term             5 years                      
Exercise price of warrants or rights (in usd per share) | $ / shares             $ 2.53                      
Number of securities called by warrants or rights (in shares)             215,914                      
Placement agent fees | $             $ 35,000                      
Deferred offering costs | $             $ 25,000                      
Exchange Warrants                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Number of shares issued per warrant (in shares)           1.2                        
Warrant inducement expense | $                             $ 0      
Offer to Amend and Exercise                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Change in fair value of warrant liabilities | $                           $ (1,058,700)        
Private Placement | Series A Preferred Stock                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Warrant term   5 years                                
Exercise price of warrants or rights (in usd per share) | $ / shares   $ 58.94                                
Number of securities called by warrants or rights (in shares)   382,779                                
Warrant issuable per investment unit (in shares)     1                              
Broker Warrants                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Units warrant units issued (in shares)   8,112                                
Broker Warrants | Series A Preferred Stock                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Number of securities called by warrants or rights (in shares)   10,899                                
Warrant                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Gain on exchange of warrants | $                           $ 380,600        
Series A Preferred Stock | Private Placement                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Number of shares issued in transaction (in shares)   382,779                                
Shares issuable per investment unit (in shares)     1                              
Preferred stock, par or stated value per share (in dollars per share) | $ / shares   $ 0.0001                                
Common shares issuable upon conversion (in shares)   38,277,900                                
Series A Preferred Stock | Broker Warrants                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Common shares issuable upon conversion (in shares)   2,712,300                                
H.C. Wainwright & Co., LLC and Ladenburg Thalmann & Co., Inc. | At-the-Market Offering                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Sale of stock, ATM maximum equity offering price | $                   $ 40,000,000                
Number of shares issued in transaction (in shares)                             705,714      
SunTrust Robinson Humphrey | Subsequent Event                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Sale of stock, ATM maximum equity offering price | $                               $ 40,000,000    
Common Stock                                    
Significant Accounting Policies Disclosure [Line Items]                                    
Issuance of common stock and warrants (in shares)                     42,695,948 4,318,272 4,886,782          
Conversion of preferred stock to common stock (in shares) 38,277,900                   38,277,900