0831 Effectiveness and Safety of Low-Sodium Oxybate in Participants with Narcolepsy: Results from the DUET Study

Abstract 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) assessing the effectiveness of low-sodium oxybate (LXB; Xywav®) treatment on daytime and nighttime symptoms in participants with narcolepsy (type 1 [NT1] or 2 [NT2]) or idiopathic hypersomnia. Data presented are from the narcolepsy cohort. Methods DUET included a screening period (with 2-week washout for current oxybate users), 8-day baseline (BL) period, 2- to 8-week LXB titration period, 2-week stable-dose period, 8-day end-of treatment (EOT) period, and 2-week safety follow-up. The primary endpoint was change in Epworth Sleepiness Scale (ESS) score from BL to EOT. Key secondary endpoints for the narcolepsy cohort included change in polysomnography parameters: total shifts from deeper to lighter sleep stages, stage N3 sleep duration (minutes), and number of awakenings. Additional endpoints included Patient Global Impression of Change (PGIc)–overall narcolepsy disease. Primary and key secondary endpoints were controlled for multiplicity with sequential testing; other P-values are considered nominal. Results Fifty-five narcolepsy participants enrolled and were dosed with LXB (NT1, n=26; NT2, n=29); 13 transferred to another cohort and 34 were completers (NT1, n=16; NT2, n=18). Enrolled participants were mostly female (72.7%) and White (80.0%); mean (SD) age was 33.4 (12.9) years (NT1=34.6 [12.6]; NT2=32.4 [13.2]). For completers, least-squares mean (LSM) (SE) changes in ESS score were −7.7 (0.9), P<.0001, overall; NT1=−6.5 (1.4), P<.0001; NT2=−8.8 (1.3), P<.0001. Compared with BL, sleep architecture at EOT showed fewer deeper to lighter sleep stage shifts (LSM [SE]: −13.1 [2.9], P<.0001, overall; NT1=−13.9 [4.3], P=0.0029; NT2=−12.3 [4.1], P=0.0050); increased stage N3 sleep (minutes) (45.0 [8.8], P<.0001, overall; NT1=49.8 [13.0], P=0.0006; NT2=40.8 [12.3], P=0.0023); and fewer awakenings (−3.2 [0.9], P=0.0015, overall; NT1=−4.1 [1.4], P=0.0056; NT2=−2.3 [1.3], P=0.0771). Most participants (93.3%, n=30; NT1, 86.7%, n=15; NT2, 100%, n=15) reported improvement (very much, much, minimally) in overall narcolepsy disease on PGIc. Treatment-emergent adverse events were consistent with the known safety profile of LXB. Conclusion Participants with NT1 and NT2 taking open-label LXB showed improvements in daytime sleepiness (decreased ESS scores) and reduced symptom burden (improved PGIc), which paralleled improvements in sleep architecture and disruption. Support (if any) Jazz Pharmaceuticals