Prepaid Expenses and Other Current Assets - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid research and development	$ 667	$ 864
Prepaid other	533	555
Other receivable	403
Prepaid insurance	269	251
Other governmental agencies receivables	6	20
Total	$ 1,878	$ 1,690