Switching to subcutaneous zilucoplan from intravenous complement component 5 inhibitors in generalised myasthenia gravis: a phase IIIb, open-label study.

Background: Zilucoplan, a peptide complement component 5 (C5) inhibitor, is self-administered as a subcutaneous (SC) injection, which offers an alternative to intravenous infusion of antibody-based complement C5 inhibitors.

Objective: To evaluate subcutaneous zilucoplan in adults with acetylcholine receptor autoantibody-positive generalised myasthenia gravis (gMG) who switched from intravenous complement C5 inhibitors to zilucoplan.

Design: MG0017 (NCT05514873) was a phase IIIb, open-label, single-arm study.

Methods: Eligible patients had clinically stable gMG on an intravenous complement C5 inhibitor and were willing to switch to zilucoplan. Patients received a 12-week treatment period of daily subcutaneous zilucoplan 0.3 mg/kg. Incidence of treatment-emergent adverse events (TEAEs) was the primary endpoint. Change from baseline in the Myasthenia Gravis Activities of Daily Living (MG-ADL) score at Week 12 was a secondary endpoint. Treatment preference (Week 12) and treatment satisfaction (9-item Treatment Satisfaction Questionnaire for Medication (TSQM-9)) were both exploratory endpoints. Assessments by prior intravenous complement C5 inhibitor were conducted post hoc.

Results: Twenty-six patients enrolled and received zilucoplan; 16 switched from eculizumab and 10 from ravulizumab. TEAEs occurred in 19/26 (73.1%) patients and were mostly mild in severity. At Week 12, least squares (LS) mean (95% confidence interval) MG-ADL scores improved from baseline by -1.15 (-2.11, -0.19), p = 0.0217 and Quantitative MG (QMG) scores by -1.24 (-2.64, 0.16), p = 0.0802. Clinically meaningful improvement from baseline in mean MG-ADL and QMG scores was observed at Week 12 among patients who switched from ravulizumab (-2.41 (-4.52, -0.30; p = 0.0307) and -3.52 (-6.14, -0.90; p = 0.0149), respectively). At Week 12, 76.9% (n = 20) patients preferred subcutaneous injection compared with intravenous infusion. Mean (standard deviation) changes from baseline in the TSQM-9 Global Satisfaction, Effectiveness and Convenience subscores at Week 12 were +19.410 (27.429), +13.889 (21.534) and +21.739 (19.955), respectively. Complement inhibition increased from baseline and was complete (>95%) by Week 2 and maintained to Week 12.

Conclusion: Zilucoplan demonstrated a favourable safety profile. gMG symptoms improved during zilucoplan treatment; this was clinically meaningful for those switching from ravulizumab.

Trial registration: ClinicalTrials.gov (NCT05514873); 22 August 2022. https://clinicaltrials.gov/study/NCT05514873.