Balance Sheet Components - Summary of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Prepaid insurance	$ 1,464	$ 918
Prepaid research and development project costs	456	853
Other receivables	328	190
Other	708	408
Total prepaid expenses and other current assets	$ 2,956	$ 2,369