STRATEGIC ALLIANCE AND COLLABORATION WITH SERVIER - Narrative (Details) - USD ($)	1 Months Ended	3 Months Ended								12 Months Ended		20 Months Ended
	Feb. 28, 2019	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Jan. 01, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 880,000	$ 695,000	$ 2,514,000	$ 372,000	$ 476,000	$ 944,000	$ 2,182,000	$ 4,784,000	$ 4,461,000	$ 8,386,000
Amounts incurred but not yet billed		300,000				500,000				300,000	500,000	$ 300,000
Accounts receivable		108,000				24,000				108,000	24,000	108,000
Servier
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable		$ 0				$ 0				0	0	0
Milestone payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue										$ 0	$ 3,690,000
Servier Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum reimbursements of development costs													$ 3,100,000
Incremental increase in amount	$ 1,000,000
Development and regulatory milestones													$ 60,400,000
Servier Collaboration Agreement | Milestone payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue												$ 7,500,000