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STOCK BASED COMPENSATION - Fair Value Assumptions (Details) - $ / shares
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Equity [Abstract]    
Volatility   104.99%
Expected term (in years)   6 years
Risk-free rate   2.24%
Expected dividend yield 0.00% 0.00%
Weighted-average grant date fair value per option (in dollars per share)   $ 2.24