Assessing Early Efficacy After Initiation of Once-Nightly Sodium Oxybate (ON-SXB; FT218) in Participants with Narcolepsy Type 1 or 2: A Post Hoc Analysis from the Phase 3 REST-ON Trial

Background: Once-nightly sodium oxybate (LUMRYZ™; ON-SXB; FT218) significantly improved narcolepsy symptoms in the phase 3 REST-ON trial. The objective of this post hoc analysis was to investigate the early efficacy of ON-SXB at weeks 1 (4.5-g dose) and 2 (6-g dose). Methods: In REST-ON, participants (≥ 16 years) with narcolepsy type 1 or 2 were randomized 1:1 to ON-SXB (4.5 g, 1 week; 6 g, 2 weeks; 7.5 g, 5 weeks; 9 g, 5 weeks) or placebo. Protocol-prespecified efficacy assessments were conducted at weeks 3 (6-g dose), 8 (7.5-g dose), and 13 (9-g dose). A post hoc analysis was conducted to assess the early efficacy of ON-SXB, defined as efficacy at weeks 1 (4.5-g dose) and 2 (6-g dose) on Epworth Sleepiness Scale (ESS) score, visual analog scale (VAS) sleep quality, and VAS refreshing nature of sleep. Least squares mean differences (LSMD) in change from baseline to weeks 1 and 2, 95% confidence intervals (CIs), and P values were calculated using mixed-effects models for repeated measures. Results: In the modified intent-to-treat population (n = 190; ON-SXB, n = 97; placebo, n = 93), baseline ESS scores were 16.6 and 17.5, sleep quality scores were 53.8 and 55.9, and refreshing nature of sleep scores were 46.5 and 49.9 with ON-SXB and placebo, respectively. At week 1 (4.5 g), numerical improvement in ESS score (LSMD [95% CI], − 0.7 [− 1.6 to 0.2]) and significant improvements in sleep quality (3.6 [1.1–6.1]; P < 0.01) and refreshing nature of sleep (3.2 [0.5–5.9]; P < 0.05) were observed with ON-SXB versus placebo. At week 2 (6 g), significant improvements with ON-SXB versus placebo were observed for ESS score (− 1.3 [− 2.4 to − 0.2]; P < 0.02), sleep quality (7.0 [3.8–10.1]; P < 0.001), and refreshing nature of sleep (5.8 [2.3–9.4]; P = 0.001). Conclusions: ON-SXB improved daytime sleepiness, sleep quality, and refreshing nature of sleep, with observable benefits beginning in the first week of treatment. These data may help clinicians set expectations with patients. Clinical Trial ID: NCT02720744.