Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid insurance	$ 582	$ 918
Prepaid research and development project costs	581	853
Other receivables	156	190
Other	617	408
Total prepaid expenses and other current assets	$ 1,936	$ 2,369