Accrued Expenses and Other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued Expenses and Other Current Liabilities.
Accrued compensation and benefits	$ 995	$ 2,490
Accrued contract manufacturing	1,578	1,550
Accrued clinical	405	606
Accrued professional services	756	530
Accrued research	186	275
Current portion of operating lease liabilities	544	506
Other	169	295
Total accrued expenses and other current liabilities	$ 4,633	$ 6,252