Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
U.S., foreign, and state net operating loss carryforwards	$ 15,815	$ 5,183
Research and development credits	454	95
Capitalized start up and organizational costs	35	39
Equity based compensation	185	29
Derivative liability		101
Licensing agreements	1,258	800
Accruals and other	948	239
Total deferred tax assets	18,695	6,486
Valuation allowance	(18,457)	(6,466)
Net deferred tax assets	238	20
Deferred tax liabilities:
Property and equipment	(238)	(20)
Total deferred tax liabilities	$ 0	$ 0