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Accrued Expenses - Schedule of Accrued Expenses (Detail) - USD ($)
$ in Thousands
Mar. 31, 2019
Dec. 31, 2018
Payables And Accruals [Abstract]    
Payroll related $ 1,165 $ 2,906
Professional fees 544 306
Research and development 2,023 1,585
Other 149 237
Total accrued expenses $ 3,881 $ 5,034