LICENSE AGREEMENTS AND COMMITMENTS - Lease costs (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Leases
Total operating lease costs	$ 646	$ 173	$ 1,291	$ 347
Cash paid for amounts included in the measurement of lease liabilities	549	205	1,093	393
Research and development expense
Leases
Total operating lease costs	587	124	1,174	247
General and administrative
Leases
Total operating lease costs	$ 59	$ 49	$ 117	$ 100