Supplemental Balance Sheet Information - Accrued Expense and Other Current Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Supplemental Balance Sheet Information [Abstract]
Accrued payroll-related expenses	$ 921	$ 920
Accrued legal expenses	245	254
Accrued clinical, contract research and manufacturing costs	554	515
Common stock warrant liability, current	71	0
Lease liability, current	177	292
Accrued other expenses	156	454
Accrued expenses and other current liabilities	$ 2,124	$ 2,435