Accrued Expenses and Other Payables (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Accrued Expenses and Other Payables
Accrued clinical and research related expenses	$ 8,956	$ 7,232
Accrued employee related expenses	1,731	4,637
Accrued interest payable	68	68
Accrued professional service fees	725	301
Other	136	122
Total accrued expenses and other payables	$ 11,616	$ 12,360