ORGANIZATION AND NATURE OF OPERATIONS - Narrative (Details) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Aug. 31, 2019 $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) $ / shares shares	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) $ / shares shares	Dec. 31, 2017 shares
Business Acquisition [Line Items]
Common stock, par value (in usd per share) | $ / shares		$ 0.01				$ 0.01				$ 0.01	$ 0.01
Common stock, shares outstanding (in shares) | shares	7,810,680	8,480,968				589,001				8,480,968	589,001
Common stock, shares issued (in shares) | shares	7,810,680	8,480,968				589,001				8,480,968	589,001
Net loss		$ (10,862)	$ (4,781)	$ (3,654)	$ (4,580)	$ (3,670)	$ (2,541)	$ (3,552)	$ 527	$ (23,877)	$ (9,236)
Net cash used in operating activities										(35,981)	3,967
Cash, cash equivalents and marketable securities		11,700								11,700
Accumulated deficit		$ (84,980)				$ (71,624)				$ (84,980)	$ (71,624)
Common Stock
Business Acquisition [Line Items]
Common stock, shares outstanding (in shares) | shares		8,480,968				589,001				8,480,968	589,001	585,262
Brickell Former Securityholders
Business Acquisition [Line Items]
Percent of shares owned	57.00%
Vical Former Securityholders
Business Acquisition [Line Items]
Percent of shares owned	43.00%
Vical
Business Acquisition [Line Items]
Common stock, par value (in usd per share) | $ / shares	$ 0.01
Reverse stock split ratio	0.1429
Series A, B, C & C-1 Redeemable Convertible Preferred Stock
Business Acquisition [Line Items]
Conversion ratio	1
Common Stock
Business Acquisition [Line Items]
Conversion ratio		2.4165								2.4165