0731 Cognitive and Functional Outcomes from the Phase 3 Open-Label Extension and Randomized-Withdrawal ENCORE Trial of AXS-12 in Narcolepsy with Cataplexy

Abstract Introduction AXS-12 (reboxetine) is a highly selective norepinephrine reuptake inhibitor and cortical dopamine modulator under development for the treatment of narcolepsy. Long-term efficacy and safety of AXS-12 in participants with narcolepsy with cataplexy (NT1) were previously reported from the Phase 3 ENCORE trial. To better understand the impact of AXS-12 on overall functional burden in NT1, we evaluated changes in cognition and functional outcomes during the ENCORE trial. Methods ENCORE included a 24-week open-label extension (OLE) period, followed by a 3-week double-blind randomized-withdrawal (DBRW) period. During the OLE, participants received AXS-12 (5 mg once-daily for 1 week, twice-daily for 23 weeks). Following this, participants were randomized 1:1 to continue twice-daily AXS-12 for 3 weeks or switch to once-daily AXS-12 plus placebo for 1 week, then placebo twice-daily for 2 weeks. P-values reported are nominal. Results ENCORE enrolled 68 participants; 42 completed the OLE and entered the DBRW (AXS-12, n=22; placebo, n=20). In the OLE, participants treated with AXS-12 reported improvement in the NSAQ Ability to Concentrate item at 1 (54.8%) and 6 (58.5%) months. Participants reported improvement in concentration, assessed by PGI-C, at 1 (66.7%) and 6 (70.0%) months. Narcolepsy overall, assessed by the CGI-C, improved at 1 (90.3%) and 6 (90.2%) months; and improved at 1 (77.8%) and 6 (80.0%) months, assessed by the PGI-C. Functional impairment, assessed by the WPAI, was reduced from 53.0% at baseline to 34.0% at 1 month and 24.3% at 6 months. In the DBRW, a greater proportion of participants switched to placebo experienced worsening on the NSAQ Ability to Concentrate item (52.6% vs 14.3%; P=0.011), and PGI-C for ability to concentrate (57.9% vs 22.2%; P=0.029) at 3 weeks compared with those continuing AXS-12. A greater proportion switched to placebo also reported worsening of their narcolepsy overall (PGI-C) at 3 weeks compared with those continuing AXS-12 (52.6% vs 16.7%; P=0.024). Treatment with AXS-12 was generally well tolerated. Conclusion Long-term, open-label treatment with AXS-12 was associated with improvements in cognitive/functional domains and productivity. Randomized withdrawal to placebo led to worsening cognition and narcolepsy overall. These results further support the long-term therapeutic benefit of AXS-12 for narcolepsy. Support (if any) Axsome Therapeutics Inc.