Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Income Statement [Abstract]
Revenue (note 13):	$ 6,829
Type of Revenue [Extensible List]	us-gaap:LicenseAndServiceMember	us-gaap:LicenseAndServiceMember
Operating expenses:
Research and development	$ 38,845	$ 23,634
General and administrative	10,803	8,406
Buy-out of future milestones and royalties (note 14c)		6,000
Total operating expenses	49,648	38,040
Loss from operations	(42,819)	(38,040)
Other income (expense):
Interest income	2,353	1,216
Interest expense	(1,434)	(1,394)
Foreign exchange gain (loss)	282	(701)
Gain on termination of collaboration agreement (note 13c)		4,398
Loss before income taxes	(41,618)	(34,521)
Income tax recovery	(23)	(24)
Net loss and comprehensive loss	(41,595)	(34,497)
Net loss attributable to preferred shareholders	(1,568)	(2,881)
Net loss attributable to common shareholders	$ (40,027)	$ (31,616)
Net loss per common share (note 6):
Basic and diluted	$ (1.54)	$ (1.63)
Weighted-average common shares outstanding (note 6):
Basic and diluted	25,939,405	19,425,711