Changes in corticosteroid and non-steroidal immunosuppressive therapy with long-term zilucoplan treatment in generalized myasthenia gravis.

BACKGROUND: The efficacy and safety of complement component 5 inhibitor zilucoplan in patients with anti-acetylcholine receptor antibody-positive generalized myasthenia gravis (gMG) were assessed in two double-blind studies (NCT03315130/NCT04115293 [RAISE]). During these studies and the first 12 weeks of the open-label extension study, RAISE-XT, corticosteroid and non-steroidal immunosuppressive therapy (NSIST) doses were kept stable; thereafter doses could be changed at the investigator's discretion. We evaluated corticosteroid and NSIST dose changes in patients with gMG during zilucoplan treatment in RAISE-XT. METHODS: In RAISE-XT, patients who completed a qualifying double-blind study self-administered once-daily subcutaneous zilucoplan 0.3mg/kg. We assessed (post hoc) patients who changed their corticosteroid or NSIST dose relative to double-blind baseline at Week 120 (data cutoff: November 11, 2023). RESULTS: Overall, 200 patients enrolled. At Week 120, 61.1% (n = 33/54) of patients who were on corticosteroids at double-blind baseline had reduced or discontinued corticosteroids (mean 15.5mg dose reduction); mean change from baseline (CFB) in Myasthenia Gravis Activities of Daily Living (MG-ADL) score:-6.55 (standard deviation [SD] 3.65). Of patients on NSIST at double-blind baseline, 29.8% (n = 14/47) reduced or discontinued ≥ 1 NSIST; mean CFB in MG-ADL score:-7.57 (SD 4.69). Among all patients at Week 120, 9.3% (n = 8/86) had increased or started corticosteroids; 2.4% of patients (n = 2/85) had increased NSIST, including one who started a new NSIST. Zilucoplan was well tolerated. CONCLUSIONS: Treatment with zilucoplan allowed for reduction or discontinuation of corticosteroids in the majority of patients and NSIST in about a third of patients, while maintaining efficacy. TRIAL REGISTRATION: NCT04225871; October 2, 2019.