Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid research and development project costs	$ 420	$ 853
Prepaid insurance	233	918
Other receivables	228	190
Other	511	408
Total prepaid expenses and other current assets	$ 1,392	$ 2,369