0755 Patient-Reported Improvement in Hypersomnolence Measures in Participants with Narcolepsy Taking >9 Gram Dosage of Low-Sodium Oxybate in the DUET Study

Introduction Jazz DUET (Develop hypersomnia Understanding by Evaluating low-sodium oxybate Treatment; NCT05875974) was the first study to evaluate effectiveness/safety of low-sodium oxybate (LXB; Xywav®) >9 g/night (outside the recommended range: 6–9 g/night). This analysis evaluated changes in patient-reported hypersomnolence measures in participants with narcolepsy taking LXB >9 g/night compared with LXB 9 g/night. Methods DUET was a phase 4, prospective, open-label study with screening, 8-day LXB 9 g/night (9g-baseline), titration/optimization, stable-dose, and 8-day end-of-treatment (EOT) optimized LXB >9 g/night (up to 12g; >9g-EOT) periods. Patient-reported measures included Epworth Sleepiness Scale (ESS), electronic sleep diaries (completed daily during 9g-baseline and >9g-EOT; subjective total sleep time [TST], number of awakenings, sleep efficiency [TST divided by time in bed], sleep quality [5-point scale; “very good” to “very poor”], and how rested/refreshed the participant felt upon awakening [5-point scale; “very well” to “not at all”]), Karolinska Sleepiness Scale (KSS; administered 90 minutes post-polysomnography awakening at 9g-baseline and >9g-EOT), and Functional Outcomes of Sleep Questionnaire-10 (FOSQ-10). LSM differences (95% CI) from 9g-baseline to >9g-EOT (nominal P-values) were 9g-baseline-adjusted. Results Forty-eight participants took LXB >9g (mean±SD age: 39.2±10.9 years; 62.5% female). Total stable-dose LXB (mean±SD) was 11.1±1.0 g/night (n=45). From 9g-baseline to >9g-EOT, ESS scores improved (LSM [95% CI]: –3.1 [–4.2, –1.9]; P< 0.0001; n=44), nocturnal TST increased (0.3h [0.1, 0.4]; P=0.0163; n=26), sleep efficiency increased (3.8% [1.7, 5.9]; P=0.0011; n=26), and number of awakenings remained stable (–0.2 [–0.7, 0.3]; P=0.3959; n=26). Percentage of participants rating sleep quality as “very good”/”good” increased from 26.9% (9g-baseline) to 61.5% (>9g-EOT), as did rested sleep (“very well”/”well”/”somewhat” rested) from 57.7% to 69.2%, respectively. From 9g-baseline to >9g-EOT, KSS scores decreased (–0.9 [–1.4, –0.4]; P=0.0004; n=39); FOSQ-10 scores also increased (1.3 [0.5, 2.0]; P=0.0014; n=40). Of 48 participants, 36 (75.0%) experienced ≥1 TEAE (mostly mild/moderate and 1 serious [syncope, unrelated to treatment]). No changes in respiratory polysomnography measures were observed. Conclusion Participants with narcolepsy who optimized to LXB >9 g/night, relative to 9 g/night, reported increased sleep quality and restfulness that paralleled improvements in daytime sleepiness and daytime functioning. TEAEs were consistent with those at lower dosages. Support (if any) Jazz Pharmaceuticals