RismadarVoice Health
September 18, 2026
Xenon Pharmaceuticals has temporarily stopped enrolling new patients in clinical trials of its experimental depression drug, azetukalner, after reports of neurological and psychiatric side effects among some participants.
The company said the voluntary pause affects studies testing the drug for major depressive disorder and bipolar depression and was introduced as a precaution following consultations with an independent safety monitoring board and a review of adverse events across the trials.
Patients already enrolled will continue receiving treatment while the company evaluates the findings.
Reported side effects included confusion, difficulties with speech and problems with motor coordination. Xenon executives also said a very small number of cases were classified under the broad medical category of psychosis.
Chief Medical Officer Christopher Kenney said the rate of cases classified as psychosis was around 1 per cent or lower, adding that the reported events were brief and resolved without identified long-term effects.
The company said the side effects had not emerged in an earlier mid-stage depression study and became more noticeable as the experimental treatment was tested in a substantially larger patient population.
Xenon is now examining possible dose adjustments aimed at reducing the frequency or severity of the side effects and improving how well patients tolerate the treatment.
The announcement sent the company’s shares down more than 25 per cent in after-hours trading on Thursday.
EPILEPSY PROGRAMME UNAFFECTED
Xenon said the enrolment pause does not affect its separate development programme for azetukalner as an epilepsy treatment.
The company has submitted an application to the US Food and Drug Administration seeking approval to use the drug for focal seizures, a common type of epilepsy seizure.
Azetukalner remains an investigational treatment for depression, and the temporary enrolment pause will allow Xenon and trial monitors to further assess its safety profile before deciding how the psychiatric studies should proceed.
