Real-World Experience with FcRn Inhibitors Efgartigimod and Rozanolixizumab in Myasthenia Gravis: Administration in Multiple Cycles and Transition from Intravenous to Subcutaneous Formulation

INTRODUCTION: The neonatal Fc receptor (FcRn) inhibitors efgartigimod and rozanolixizumab have not long been introduced for treating generalized myasthenia gravis (MG); hence, real-world evidence for their administration in multiple cycles and switching from intravenous to subcutaneous formulation remains insufficient. METHODS: We retrospectively assessed 17 consecutive patients with generalized MG and diverse backgrounds who were treated with FcRn inhibitors. RESULTS: All patients initially received an intravenous efgartigimod formulation. Of 17 patients, 10 (59%) were considered responders, defined as a persistent improvement of at least two points for a minimum of four consecutive weeks in the MG activities of daily living score during the first treatment cycle. Four of the non-responders in the first cycle demonstrated an improvement in fulfilling the criteria for responders in the second cycle. One of these patients, who had thymoma metastatic lesions, experienced a significant worsening of MG symptoms during the first treatment cycle. Five patients switched from intravenous to subcutaneous formulations, which was successful in all patients. The efficacy of the subcutaneous formulations was similar to that of the intravenous formulation, even in patients who switched from efgartigimod to rozanolixizumab. The drugs were well tolerated without any drug-related serious adverse events irrespective of the formulation type. CONCLUSION: FcRn inhibitors were effective and safe in patients with generalized MG, but their efficacy may depend on the disease activity during treatment. The transition from the intravenous formulation to more convenient subcutaneous formulations was successful, indicating the likely growth of future demand for subcutaneous formulations.