Xenon Pharmaceuticals Inc. shares fell 30.17% on September 18, 2026, after the company temporarily paused new-patient enrollment in its Phase 3 trials of azetukalner for major depressive disorder and bipolar depression. The decision followed unexpected neuropsychiatric adverse events, including confusion, excessive drowsiness, coordination problems, and isolated psychotic episodes. Although epilepsy trials for the drug continue, the safety setback prompted analysts to downgrade the stock and cut price targets.