0573 Application of AASM Clinical Significance Thresholds to Once-Nightly Sodium Oxybate for Improvement in Narcolepsy Symptoms

Abstract

Introduction: Once-nightly sodium oxybate (ON-SXB; FT218), an investigational, extended-release treatment, was evaluated for the treatment of narcolepsy in adults in the phase 3 REST-ON clinical trial (NCT02720744). The 3 co-primary endpoints, mean sleep latency on the Maintenance of Wakefulness Test (MWT), Clinical Global Impression-Improvement rating, and weekly number of cataplexy attacks (NCA), and the secondary endpoint of Epworth Sleepiness Scale (ESS) score were significant for ON-SXB vs placebo at weeks 3 (6-g dose), 8 (7.5-g dose), and 13 (9-g dose; all P< 0.001). These data were published after the cutoff for inclusion in the American Academy of Sleep Medicine (AASM) clinical practice guidelines for narco-lepsy treatment; thus, REST-ON results were analyzed according to AASM clinical significance thresholds (CSTs). Methods: Individuals with narcolepsy type 1/2 and age ≥16 years were randomized 1:1 to receive double-blind ON-SXB (4.5 g, 1 week; 6 g, 2 weeks; 7.5 g, 5 weeks; 9 g, 5 weeks) or matching placebo. For each dose (6 g, week 3; 7.5 g, week 8; and 9 g, week 13), least-squares mean (LSM) difference from placebo was calculated for change from baseline in mean sleep latency on the MWT, ESS score, and percentage reduction in NCA. As defined in the 2021 AASM guidelines, CSTs were the following changes vs placebo: MWT, ≥2-minute increase; ESS, ≥2-point decrease; and cataplexy, ≥25% decrease in NCA. Results: 190 participants (ON-SXB, n=97; placebo, n=93) were in the modified intent-to-treat population. On the MWT, difference in LSM change from baseline was 5.0, 6.2, and 6.1 minutes for ON-SXB 6, 7.5, and 9 g vs placebo, respectively. Differences in LSM change from baseline ESS scores were −2.1, −3.2, and −3.9 for ON-SXB 6, 7.5, and 9 g vs placebo, respectively. Differences in LSM percentage reduction in NCA were 26.0%, 34.2%, and 36.1% for ON-SXB 6, 7.5, and 9 g vs placebo, respectively. Conclusion: Clinically significant improvement in excessive daytime sleepiness and cataplexy per AASM-established criteria was met with ON-SXB 6, 7.5, and 9 g doses. If FDA approved, ON-SXB will provide a once-nightly treatment for improving EDS and cataplexy in adults with narcolepsy. Support (if any): Avadel Pharmaceuticals