Property and Equipment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property and equipment
Property and equipment, gross	$ 2,789	$ 1,904
Less: accumulated depreciation	(573)	(610)
Property and equipment	2,216	1,294
Laboratory equipment
Property and equipment
Property and equipment, gross	1,756	1,756
Leasehold improvements
Property and equipment
Property and equipment, gross	899
Office furniture and equipment
Property and equipment
Property and equipment, gross	$ 134	$ 148