Xenon stock falls 30% but FDA story proves more complex

Xenon Pharmaceuticals announced in one press release a New Drug Application to the FDA for azetukalner in focal seizures and a voluntary pause of new-patient enrollment in Phase 3 trials X-NOVA2 for major depressive disorder and X-CEED for bipolar depression after neuropsychiatric events including psychosis. Shares fell 30.69% from $57.35 to $39.75, versus a 52-week high of $73, erasing about $1.7 billion from a market cap near $3.85 billion. The company said the FDA imposed no clinical hold; already-enrolled patients continue on drug; and events including confusion, aphasia, ataxia and somnolence were short, reversible and without long-term sequelae. X-NOVA2 had enrolled about 360 of 450 patients (80%), with topline still guided for Q1 2027. CMO Christopher Kenney said a very small number of patients had an adverse event under the broad preferred term of psychosis. CEO Ian Mortimer said the company will make dosing changes over the coming months to improve tolerability. Analysts at Deutsche Bank, Needham, H.C. Wainwright, Baird, RBC and TD Cowen issued rating or target changes. NDA acceptance and dosing details are next.