Open this photo in gallery: Ian Mortimer, CEO of Xenon, at the company's laboratory in Burnaby, B.C, on Dec. 1.Tijana Martin/The Globe and Mail Canada’s most valuable drug developer is a B.C. company whose epilepsy treatment sharply reduces seizures in patients without causing an odd side effect from a similar drug shelved by GSK plc in 2017: turning patients’ skin blue. Now, Xenon Pharmaceuticals Inc. XENE-Q hopes to show its anti-seizure drug can do something else: Make depressed people happier. The Burnaby company plans to develop antidepressant drugs based on its flagship molecule, XEN1101, after unveiling promising results last Monday...