Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities.
Accrued compensation and benefits	$ 2,021	$ 2,490
Accrued contract manufacturing	732	1,550
Accrued clinical	545	606
Accrued professional services	393	530
Accrued research	172	275
Current portion of operating lease liabilities	577	506
Other	121	295
Total accrued expenses and other current liabilities	$ 4,561	$ 6,252