ORGANIZATION AND NATURE OF OPERATIONS - Narrative (Details)		3 Months Ended						9 Months Ended
	Aug. 31, 2019 $ / shares shares	Sep. 30, 2019 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) shares	Mar. 31, 2019 USD ($) shares	Sep. 30, 2018 USD ($) shares	Jun. 30, 2018 USD ($) shares	Mar. 31, 2018 USD ($) shares	Sep. 30, 2019 USD ($) $ / shares shares	Sep. 30, 2018 USD ($) shares	Dec. 31, 2018 USD ($) $ / 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
Common stock, shares outstanding | shares	7,810,680	7,810,680						7,810,680		589,001
Common stock, shares issued | shares	7,810,680	7,810,680						7,810,680		589,001
Net loss		$ (4,781,000)	$ (3,654,000)	$ (4,580,000)	$ (2,541,000)	$ (3,552,000)	$ 527,000	$ (13,015,000)	$ (5,566,000)
Net cash used in operating activities								(21,940,000)	$ 7,621,000
Cash, cash equivalents and marketable securities		25,700,000						25,700,000
Accumulated deficit		$ (74,118,000)						$ (74,118,000)		$ (71,624,000)
Common Stock
Business Acquisition [Line Items]
Common stock, shares outstanding | shares		7,810,680	589,001	589,001	587,563	586,700	586,700	7,810,680	587,563	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	1						1
NovaQuest
Business Acquisition [Line Items]
Commitment amount					$ 25,000,000.0				$ 25,000,000.0
Stock issuable upon warrants (in shares) | shares		241,225						241,225