Property and equipment, net - Summary (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 1,253	$ 1,253
Less: Accumulated depreciation	(824)	(780)
Property and equipment, net	429	473
Computer equipment
Property, Plant and Equipment [Line Items]
Gross property and equipment	201	201
Office and other equipment
Property, Plant and Equipment [Line Items]
Gross property and equipment	260	260
Laboratory equipment
Property, Plant and Equipment [Line Items]
Gross property and equipment	729	729
Leasehold improvements
Property, Plant and Equipment [Line Items]
Gross property and equipment	$ 63	$ 63

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

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Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

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