Dublin — Alkermes said an interim analysis of a long-term extension study showed that its experimental drug alixorexton produced sustained improvements in wakefulness and excessive daytime sleepiness in adults with narcolepsy type 1 and type 2.
The improvements were observed after 24 weeks in the extension study, representing up to about nine months of treatment for participants who previously received alixorexton in the phase 2 Vibrance-1 and Vibrance-2 studies.
Alixorexton is an investigational, once-daily oral orexin 2 receptor agonist being developed for narcolepsy type 1, narcolepsy type 2 and idiopathic hypersomnia.
“For people living with narcolepsy, symptom burden extends beyond excessive daytime sleepiness and can affect cognitive function and fatigue,” said Yves Dauvilliers, professor of neurology and physiology and director of the Sleep-Wake Disorders Center at the University of Montpellier in France. “It is exciting to see clinically meaningful improvements sustained across these important measures in this analysis of the long-term extension study of alixorexton in patients with narcolepsy type 1 and type 2.”
Among participants with narcolepsy type 1, all dose groups achieved mean sleep latency of at least 20 minutes on the Maintenance of Wakefulness Test at week 24. Mean sleep latency across participants was about 29 minutes, while the mean Epworth Sleepiness Scale score was 7.5, within the normal range.
The treatment also reduced weekly cataplexy rates. At week 24, the median weekly cataplexy rate across participants was two episodes.
About 85% of the 92 participants in Vibrance-1 entered the extension study, and roughly 90% of those participants remained on treatment as of the May 12, 2026, data cutoff.
Among participants with narcolepsy type 2, mean sleep latency was about 18 minutes at week 24, while the mean Epworth Sleepiness Scale score was 8.9. Improvements were also maintained in patient-reported measures of cognition and fatigue.
Approximately 70% of the 93 participants in Vibrance-2 enrolled in the extension study, and about 80% remained on treatment at the data cutoff.
Alixorexton was generally well tolerated across all tested doses, and no serious treatment-emergent adverse events were reported. Most adverse events were mild or moderate.
The most common adverse events among participants with narcolepsy type 1 included headache, urinary urgency, frequent urination and nasopharyngitis. Among those with narcolepsy type 2, the most common events included insomnia, headache, frequent urination and upper respiratory tract infection.
“These long-term results represent a significant contribution to our understanding of alixorexton as a potential new treatment option for patients with narcolepsy,” said Craig Hopkinson, chief medical officer and executive vice president of research and development at Alkermes. “We are particularly encouraged by the durability of effect observed across multiple dimensions of the disease, including wakefulness, cognition and fatigue, together with a safety profile that continued to be generally well tolerated.”
Alkermes is enrolling patients in its phase 3 Brilliance studies and expects to complete the phase 2 Vibrance-3 study of alixorexton in idiopathic hypersomnia later this year.
