Accounts Payable and Other Liabilities - Schedule of Accounts Payable and Other Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Trade accounts payable	$ 702	$ 6,016
Accrued clinical/preclinical expenses	3,655	2,667
Accrued compensation and vacation	21	1,553
Other accrued liabilities	249	720
Accounts payable and other liabilities	$ 4,627	$ 10,956