Alkermes plc (Nasdaq: ALKS) reported interim data from the ongoing long-term extension (LTE) of its Phase II Vibrance program showing that once-daily orexin 2 receptor agonist alixorexton maintained efficacy through approximately nine months of treatment in both narcolepsy type 1 (NT1) and type 2 (NT2), with no serious treatment-emergent adverse events reported.
The LTE enrolled participants completing the Vibrance-1 (NT1) and Vibrance-2 (NT2) studies. Data were cut off on May 12, 2026, with efficacy assessed after 24 weeks in the extension.
Among NT1 participants, around 85% entered the LTE and approximately 90% remained on treatment. Mean Maintenance of Wakefulness Test (MWT) sleep latency reached approximately 29 minutes across participants, compared with baseline values of 1.7-3.4 minutes. Epworth Sleepiness Scale (ESS) scores remained in the normal range, averaging 7.5, while median weekly cataplexy episodes fell from roughly 15-20 at baseline to two.
Approximately 70% of NT2 participants enrolled in the LTE, with about 80% remaining on treatment. Mean MWT sleep latency improved to approximately 18 minutes, while ESS scores also remained within the normal range.
Exploratory measures of cognition and fatigue also improved through week 24 in both populations. No serious treatment-emergent adverse events were reported.
The durability data strengthen Alkermes' Phase III Brilliance program by demonstrating sustained efficacy and a stable safety profile in a chronic disease requiring lifelong treatment. The company is conducting three global Phase III studies in NT1 and NT2, while the LTE will continue to collect longer-term data. Alkermes also expects Phase II data in idiopathic hypersomnia later in 2026.
Alixorexton received US FDA Breakthrough Therapy designation for NT1 in January 2026 and holds Orphan Drug designation in the US and EU.