Accounts payable and accrued liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Accounts payable and accrued liabilities
Trade accounts payable	$ 3,324	$ 2,603
Accrued research and development liabilities	3,580	1,012
Other accrued liabilities	560	164
Accrued compensation and benefits payable	1,014	698
Accounts payable and accrued liabilities	$ 8,478	$ 4,477