LICENSE AGREEMENTS AND COMMITMENTS - Other agreements (Details) $ in Thousands							3 Months Ended		9 Months Ended
	Sep. 13, 2019	Oct. 01, 2018 individual	Nov. 13, 2017	Jun. 27, 2017 agreement	Jun. 21, 2017	Mar. 20, 2016 individual	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)
Agreements
Research and development							$ 19,660	$ 8,731	$ 46,665	$ 23,228
SRA
Agreements
Research service period	5 years
Research and development							306	297	918	891
MDSA
Agreements
Research and development							205	60	547	273
CTA
Agreements
Research service period					5 years
Research and development							513	363	2,647	2,504
CFAs
Agreements
Number of service agreements | agreement				2
Research and development							186	28	674	223
CD33-SRA
Agreements
Research service period			2 years
Research and development							$ 174	$ 167	$ 521	$ 501
Researchers, Employees of MSK | MDSA
Agreements
Number of individuals | individual		5				2