0749 Effectiveness and Safety of Low-Sodium Oxybate by Patient-Reported Long Sleep Need in DUET Study Participants with Idiopathic Hypersomnia

Introduction Low-sodium oxybate (LXB; Xywav®), the only FDA-approved treatment for idiopathic hypersomnia in adults, was evaluated in the phase 4, open-label DUET study (NCT05875974). This post-hoc analysis evaluated subgroups of participants with idiopathic hypersomnia stratified by patient-reported ideal nighttime sleep duration (with [>9 hours] and without [≤9 hours] long sleep need [LSN]), based on Idiopathic Hypersomnia Severity Scale (IHSS) Item 1. Methods DUET included screening, 8-day baseline (BL), 2−8-week LXB dose titration/optimization, 2-week stable-dose, 8-day end-of-treatment (EOT), and 2-week safety follow-up periods. Outcomes were Epworth Sleepiness Scale (ESS), IHSS, polysomnographic total sleep time (TST), and Patient Global Impression of Severity (PGI-S) and Change (PGI-C). Least squares mean (LSM) changes (BL-to-EOT) were BL-adjusted; P values are nominal. Treatment-emergent adverse events (TEAEs) were assessed by subgroup. Results Of 46 enrolled participants with idiopathic hypersomnia, 45 had BL IHSS data; 24 reported LSN (>9 hours) and 21 reported no LSN (≤9 hours). Most (LSN/without LSN) were female (100%/61.9%) and White (91.7%/76.2%), with mean±SD age 36.8±11.1/38.6±12.1 years; 20/24 and 19/21 completed the study. BL mean±SE (LSN/without LSN) ESS scores were 16.8±0.5/16.1±0.7; LSM changes (95% CI): LSN −9.5 (−11.5, −7.6; P< 0.0001; n=20), without LSN −7.4 (−9.4, −5.4; P< 0.0001; n=19). BL mean±SE (LSN/without LSN) IHSS total scores were 35.7±1.3/30.5±1.8; LSM changes (95% CI): LSN −18.3 (−22.4, −14.1; P< 0.0001; n=19), without LSN −12.5 (−16.9, −8.0; P< 0.0001; n=17). BL mean±SE (LSN/without LSN) IHSS long sleep/sleep inertia component scores were 12.5±0.6/9.2±0.6; LSM changes (95% CI): LSN −5.5 (−6.8, −4.1; P< 0.0001; n=19), without LSN −4.0 (−5.4, −2.5; P< 0.0001; n=17). BL mean±SE (LSN/without LSN) polysomnographic TSTs were 490.0±26.0/442.7± 24.7 minutes; LSM changes (95% CI): LSN −53.1 (−92.5, −13.7; P=0.0097; n=20), without LSN −59.4 (−99.8, −18.9; P=0.0052; n=19). On the PGI-C, most participants (LSN/without LSN) endorsed improved overall disease (100%/88.2%; n=19/n=17) at EOT. TEAEs were reported in 79.2% (LSN) and 66.7% (without LSN); most (LSN/without LSN) were mild (45.8%/42.9%) or moderate (33.3%/23.8%) in severity; 1 (without LSN) was serious (unrelated to study drug). Conclusion Participants with or without LSN (>9 hours or ≤9 hours, respectively) taking LXB showed improvements in multiple idiopathic hypersomnia symptoms and reduced TST. Support (if any) Jazz Pharmaceuticals