COMMITMENTS AND CONTINGENCIES, LEASES (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) claim	Nov. 01, 2018 USD ($)	May 03, 2018 USD ($) ft²	Nov. 30, 2011 USD ($) ft²
Lessee, Lease, Description [Line Items]
Costs expected to be paid to clinical research organization | $	$ 5,300
Cambridge Lease
Lessee, Lease, Description [Line Items]
Lease space (in square feet) | ft²				26,342
Term of commercial lease	6 years 3 months
Number of options to extend lease | claim	1
Term of lease extension option	5 years
Standby letter of credit | $		$ 60	$ 40	$ 311
Cambridge Lease | Sublease
Lessee, Lease, Description [Line Items]
Lease space (in square feet) | ft²			5,104