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Xenon Halts Phase 3 Depression and Bipolar Trial Enrollment

By Drooid · Sep 19, 2026, 3:03 PM UTC · How we work

Summary

Xenon Pauses Trials

Xenon Pharmaceuticals paused enrollment in its Phase 3 depression (X-NOVA2) and bipolar (X-CEED) trials after neuropsychiatric adverse events.
The X-NOVA2 study stopped with 360 of 450 participants enrolled, while the X-CEED trial also halted.
Reported adverse events were mild-to-moderate confusion, aphasia, ataxia and one reversible psychosis case.
Shares fell 27% on Friday to EUR 36.40, with cash at USD 1,245.1 million and a net loss of USD 110.7 million.

Summary

Xenon Files NDA

Xenon submitted an NDA for azetukalner to treat focal seizures, citing Phase 2b X-TOLE and Phase 3 X-TOLE2 results.
Xenon paused psychiatry trial enrollment after consulting its Data Safety Monitoring Board.
Chief Medical Officer Christopher Kenney said psychosis occurred in about 1% of patients and was brief.
MDD X-NOVA2 enrollment reached 360 patients, about 80% of its 450-patient goal.
Phase 3 X-TOLE3 and X-ACKT epilepsy trials keep recruiting despite the pause.

History

Historical Context

In the 1990s GSK funded Study 329, led by Martin Keller, which claimed Paxil worked in depressed teens but later showed no efficacy and a 3.4 % suicide-related event rate versus 0.9 % on placebo. After the MHRA warned against pediatric use in June 2003, the FDA halted GSK’s 2006 Phase III pediatric Paxil trial when a 2 % rise in suicidal thoughts emerged.

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Xenon Pauses Trials

Xenon Pharmaceuticals paused enrollment in its Phase 3 depression (X-NOVA2) and bipolar (X-CEED) trials after neuropsychiatric adverse events.
The X-NOVA2 study stopped with 360 of 450 participants enrolled, while the X-CEED trial also halted.
Reported adverse events were mild-to-moderate confusion, aphasia, ataxia and one reversible psychosis case.
Shares fell 27% on Friday to EUR 36.40, with cash at USD 1,245.1 million and a net loss of USD 110.7 million.

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