COMMITMENTS AND CONTINGENCIES, LEASES (Details) $ in Thousands			12 Months Ended
	May 03, 2018 USD ($) ft²	Oct. 31, 2017 USD ($) ft² item	Dec. 31, 2018 USD ($)	Nov. 01, 2018 USD ($)	Jun. 30, 2018 USD ($)	Jun. 19, 2017 USD ($)	Jun. 13, 2017 ft²
Lessee, Lease, Description [Line Items]
Deferred rent removed and gain on lease assignment			$ 603
Loss on impairment of fixed assets	$ 48		48
Prepaid rent			17
Rent expense			837
Operating Lease, Expense			837
Moderna Sublease
Lessee, Lease, Description [Line Items]
Lease space (in square feet) | ft²							5,233
Sublease income recorded as offset to rent expense			112
Tenant security deposit						$ 55
Third Party Lease
Lessee, Lease, Description [Line Items]
Lease space (in square feet) | ft²	5,104
Standby letter of credit	$ 40			$ 60
Tenant security deposit					$ 55
Cambridge Lease
Lessee, Lease, Description [Line Items]
Lease space (in square feet) | ft²		26,342
Term of commercial lease		6 years 3 months		5 years
Number of options to extend lease | item		1
Term of lease extension option		5 years
Standby letter of credit		$ 311
Letter of credit terminated amount	$ 311
Loss on impairment of fixed assets			$ 48