Suzuki S, Uzawa A, Nagane Y, Masuda M, Konno S, Kubota T, Samukawa M, Ishizuchi K, Tokuyasu D, Handa H, Yasuda M, Kawaguchi N, Kimura T, Suzuki Y, Sugimoto T, Minami N, Takahashi MP, Murai H, and Utsugisawa K
Background and Objectives: Efgartigimod, which has been well tolerated and efficacious in individuals with generalized myasthenia gravis (MG), is available in Japan not only for the treatment of anti-acetylcholine receptor-positive (AChR+) but also anti-muscle-specific receptor tyrosine kinase (MuSK+) and seronegative generalized MG. We report details of the use of efgartigimod for generalized MG in clinical practice in Japan., Methods: We included patients with generalized MG in the 2021 survey of Japan Myasthenia Gravis Registry (JAMG-R) study group who received an initial cycle of efgartigimod between May and September 2022. We defined "responders" as patients who achieved a score ≥2 points for MG activities of daily living (MG-ADL) in the first treatment cycle. The MG composite and the Revised scale of the 15-item Myasthenia Gravis-Quality of Life scale (MG-QOL15-r) were also evaluated., Results: Of 1,343 JAMG-R patients, 36 (2.7%) started efgartigimod (female 68%, age 53 years). Their serologic profiles were as follows: AChR+, n = 19 (53%); MuSK+, n = 6 (17%); and seronegative, n = 11 (31%). Twenty-six patients (72%) had refractory MG. There were 81 cycles of efgartigimod during the 26-week observation in 34 patients (average, 2.4 cycles). The mean interval between cycles was 5.9 weeks. A continuous 4-weekly infusion of efgartigimod was performed in 65 (80%) of 81 cycles. In the first cycle, the MG-ADL score of the 34 patients decreased significantly from 10.5 ± 4.3 to 6.9 ± 5.1 ( p = 0.003). Similarly, the mean MG composite and MG-QOL15-r decreased from 18.4 ± 13.6 to 11.8 ± 9.6 ( p = 0.004) and from 19.2 ± 6.3 to 14.2 ± 8.3 ( p = 0.007), respectively. Twenty-one (62%) patients were responders. Therapeutic responses were observed in the subsequent cycles. The duration of effectiveness of efgartigimod was varied among the responders; 4 responders had only a single effective cycle. Significant improvement was observed in the MuSK+ patients. Prednisolone dose of 7 patients was reduced. Our examination of the patients' postintervention status revealed that 6 patients achieved minimal manifestations. COVID-19 occurred in 5 patients. We failed to detect clinical or laboratory findings associated with responders., Discussion: Efgartigimod can be considered for the treatment of patients with generalized MG who do not achieve minimal manifestations, with a broad flexibility of patient selection and treatment schedules., Competing Interests: S. Suzuki has received personal fees from Alexion Pharmaceuticals, Argenx, UCB Pharma, the Japan Blood Products Organization, and Asahi Kasei Medical. A. Uzawa has received honoraria from Alexion Pharmaceuticals and Argenx. Y. Nagane has received speaker honoraria from Argenx, Alexion Pharmaceuticals, and the Japan Blood Products Organization. M. Masuda and S. Konno declare no potential conflicts of interest related to this article. T. Kubota has received honoraria for lectures from Alexon Pharmaceuticals, Argenx, and UCB Pharma. M. Samukawa, K. Ishizuchi, D. Tokuyasu, H. Handa, M. Yasuda, N. Kawaguchi, T. Kimura, Y. Suzuki, T. Sugimoto, and N. Minami declare no potential conflicts of interest related to this article. M.P. Takahashi reports unrestricted research grants from Japan Blood Products Organization, Astellas Pharma, Mitsubishi Tanabe Pharma, and Pfizer outside the submitted work and honoraria for lectures from Argenx, Alexion Pharmaceuticals, and UCB Pharma. H. Murai has served as a paid consultant for Alexion, AstraZeneca Rare Disease, Argenx, and UCB and has received speaker honoraria from the Japan Blood Products Organization and Chugai Pharmaceutical and research support from the Ministry of Health, Labour and Welfare, Japan. K. Utsugisawa has served as a paid consultant for UCB Pharma, Argenx, Janssen Pharma, Viela Bio, Chugai Pharma, Hanall BioPharma, and Mitsubishi Tanabe Pharma and has received speaker honoraria from Argenx, Alexion Pharmaceuticals, and the Japan Blood Products Organization. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)