Annual report pursuant to Section 13 and 15(d)

INCOME TAXES (Details)

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INCOME TAXES (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Deferred tax assets      
Net operating loss carryforwards $ 240,157 $ 226,388  
Orphan drug and research and development credits 59,603 55,276  
Deferred compensation 8,817 7,155  
Lease liabilities 6,989    
Capitalized research and development expenses 2,282 424  
Other, net 529 809  
Deferred tax liabilities      
Operating lease right-of-use asset (6,719)    
Total net deferred tax assets 311,658 290,052  
Valuation allowance (311,658) (290,052)  
Deferred tax assets, net of allowance  
Reconciliation of the statutory federal income tax rate to the effective tax rate      
Federal statutory tax rate (as a percent) (21.00%) (21.00%) (34.00%)
Federal statutory rate reduction     160.20%
State, Net of Federal Benefit 0.10%    
Valuation allowance (as a percent) 21.70% 16.30% (126.50%)
Stock compensation (as a percent) 2.80% 8.20% 5.70%
Orphan drug and research and development credits (5.10%) (3.70%) (3.60%)
Other, net (as a percent) 1.50% 0.20% (1.80%)
Effective tax rate (as a percent) 0.00% 0.00% 0.00%