0743 Vibrance-2: A Randomized Phase 2 Study Evaluating Efficacy and Safety of the Orexin 2 Receptor Agonist Alixorexton in Patients with Narcolepsy Type 2

Abstract Introduction Narcolepsy type 2 (NT2) is characterized by excessive daytime sleepiness, heterogeneous symptom severity, and typically normal endogenous orexin levels. The Vibrance-2 phase 2 study evaluated alixorexton, a selective orexin 2 receptor agonist, in patients with NT2. Methods Vibrance-2 was a placebo-controlled, dose-ranging phase 2 study. After a 2-week washout from current narcolepsy medications, adults with NT2 meeting ICSD-3-TR diagnostic criteria were randomized 1:1:1:1 to receive placebo or alixorexton once daily at doses of 10, 14, or 18mg for 8 weeks, followed by an optional 5-week open-label extension. Dual primary endpoints were the change from baseline to week 8 in mean sleep latency (MSL) on the Maintenance of Wakefulness Test (MWT) and on the Epworth Sleepiness Scale (ESS). Safety evaluation included treatment-emergent adverse events (TEAEs). P-values were adjusted for multiplicity. Results Ninety-three patients were randomized to placebo (n=24) or alixorexton (10mg, n=23; 14mg, n=22; 18mg, n=24); 90 completed double-blind treatment. At baseline, patients had severe symptoms (MWT: 5.6 minutes; ESS: 17.4). The study met its dual primary endpoints. At week 8, MSL on MWT increased 9.3, 6.7, and 6.7 minutes at 10, 14, and 18mg, respectively, from baseline versus placebo, with statistically significant differences observed for the 14 and 18mg doses (adjusted p< 0.05). ESS improved by -2.1, -3.2, and -3.6 points from baseline versus placebo at week 8 for the 10, 14, and 18mg groups, respectively, with statistical significance observed for the 18mg dose (adjusted p< 0.05), where more than 70% of patients achieved normalization. TEAEs in 10% of all alixorexton-treated patients through week 8 were pollakiuria, insomnia, micturition urgency, dizziness, and headache. Most TEAEs were mild-to-moderate with no serious TEAEs. Conclusion Vibrance-2 was the first large clinical trial in patients with NT2 to demonstrate positive results with an orexin 2 receptor agonist. Alixorexton resulted in statistically significant and clinically meaningful improvements in wakefulness and daytime sleepiness at Week 8 and was generally well tolerated. These results support phase 3 clinical development of alixorexton as a treatment for NT2. Support (if any) Alkermes, Inc.