LICENSE AGREEMENTS AND COMMITMENTS - Lease costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Leases
Total operating lease costs	$ 676
Rental expense for operating leases		$ 394
Cash paid for amounts included in the measurement of lease liabilities	606
Research and development expense
Leases
Total operating lease costs	493
General and administrative expense
Leases
Total operating lease costs	$ 183
Rental expense for operating leases		$ 394