0851 Effectiveness and Safety of Low-Sodium Oxybate in Idiopathic Hypersomnia Participants: Results from the DUET Study

Abstract Introduction Introduction: Jazz DUET (Develop hypersomnia Understanding by Evaluating low-sodium oxybate Treatment) is a phase 4, prospective, multicenter, single-arm, multiple-cohort, open-label study (NCT05875974) evaluating the effectiveness of low-sodium oxybate (LXB, Xywav®) treatment on daytime and nighttime symptoms, including excessive daytime sleepiness (EDS) and polysomnography in participants with idiopathic hypersomnia (IH) or narcolepsy. Data presented are from the IH cohort. Methods DUET included screening (with 2-week washout for oxybate users), 8-day baseline (BL), 2- to 8-week LXB titration, 2-week stable-dose, 8-day end-of-treatment (EOT), and 2-week safety follow-up periods. The primary endpoint was change in Epworth Sleepiness Scale (ESS) score from BL to EOT. Secondary endpoints for the IH cohort included change in Idiopathic Hypersomnia Severity Scale (IHSS) total score, Patient Global Impression of Change (PGIc)−overall IH disease, PGIc−sleep inertia, and Patient Global Impression of Severity (PGIs)−sleep inertia. Exploratory endpoints included IHSS component scores (daytime functioning, sleep inertia). Primary and key secondary (IHSS total score) endpoints were controlled for multiplicity with sequential testing; all other P-values are considered nominal. Results Forty-six people with IH enrolled and were dosed with LXB; 40 were completers. Enrolled participants were mostly female (80.4%) and White (84.8%), with a mean (SD) age of 38.1 (11.8) years. For completers, BL mean (SD) ESS score and IHSS total score were 16.5 (2.7) and 32.9 (7.1), respectively; least-squares mean (LSM) (SE) changes from BL to EOT were −8.4 (0.7), P<.0001 and −15.5 (1.5), P<.0001. BL mean (SD) IHSS component scores for daytime functioning and sleep inertia were 17.7 (4.2) and 10.7 (3.1), respectively; LSM (SE) changes from BL to EOT were −8.8 (1.0), P<.0001 and −4.8 (0.4), P<.0001. At EOT, most participants reported improvement (very much, much, minimally) on PGIc−overall IH disease (94.6%) and PGIc−sleep inertia (81.1%). At BL, 25.0% of participants reported sleep inertia severity as very mild/mild/not present on PGIs–sleep inertia vs 59.0% at EOT. Treatment-emergent adverse events were consistent with the known safety profile of LXB. Conclusion People with IH taking open-label LXB showed improvements in EDS and sleep inertia (decreased ESS and IHSS component scores) and reported reduced multi-symptom burden (decreased IHSS total scores and improved PGIc/PGIs ratings). Support (if any) Jazz Pharmaceuticals