Accounts Payable - Additional Information (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Accounts Payable [Line Items]
Accounts Payable, Current	$ 607	$ 813
Other Payables [Member]
Accounts Payable [Line Items]
Accounts Payable, Current	100	100
Preclinical Expenses [Member]
Accounts Payable [Line Items]
Accounts Payable, Current		200
License Maintenance Fee [Member]
Accounts Payable [Line Items]
Accounts Payable, Current		100
Manufacturing Costs [Member]
Accounts Payable [Line Items]
Accounts Payable, Current		100
Legal Expenses [Member]
Accounts Payable [Line Items]
Accounts Payable, Current	200
Clinical Research Organizations [Member]
Accounts Payable [Line Items]
Accounts Payable, Current	$ 300	$ 300