Accrued Expenses - Additional Information (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Accounts Payable and Accrued Liabilities [Line Items]
Accrued expenses	$ 868	$ 739
Accrued Vacation And Bonus	200	100
Accrued Clinical And Preclinical	500	400
Accrued License Maintenance Fee	100	100
Other Accrued Liabilities	$ 100	$ 100