Accrued Expenses and Other Liabilities - Schedule of Accrued Expenses and Other Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Accrued Liabilities And Other Liabilities [Abstract]
Accrued clinical	$ 350	$ 85
Accrued professional services	182	158
Accrued vacation	131	111
Accrued compensation and related expenses	52
Accrued other	47
Total accrued expenses and other liabilities	$ 762	$ 354