Therapeutic Responses to Efgartigimod for Generalized Myasthenia Gravis in Japan

Shigeaki Suzuki; Akiyuki Uzawa; Yuriko Nagane; Masayuki Masuda; Shingo Konno; Tomoya Kubota; Makoto Samukawa; Kei Ishizuchi; Daiki Tokuyasu; Hideo Handa; Manato Yasuda; Naoki Kawaguchi; Takashi Kimura; Yasushi Suzuki; Takamichi Sugimoto; Naoya Minami; Masanori P Takahashi; Hiroyuki Murai; Kimiaki Utsugisawa

doi:10.1212/CPJ.0000000000200276

Therapeutic Responses to Efgartigimod for Generalized Myasthenia Gravis in Japan

Neurol Clin Pract. 2024 Jun;14(3):e200276. doi: 10.1212/CPJ.0000000000200276. Epub 2024 Mar 25.

Authors

Shigeaki Suzuki¹, Akiyuki Uzawa¹, Yuriko Nagane¹, Masayuki Masuda¹, Shingo Konno¹, Tomoya Kubota¹, Makoto Samukawa¹, Kei Ishizuchi¹, Daiki Tokuyasu¹, Hideo Handa¹, Manato Yasuda¹, Naoki Kawaguchi¹, Takashi Kimura¹, Yasushi Suzuki¹, Takamichi Sugimoto¹, Naoya Minami¹, Masanori P Takahashi¹, Hiroyuki Murai¹, Kimiaki Utsugisawa¹

Affiliation

¹ Department of Neurology (SS, KI, DT), Keio University School of Medicine, Tokyo; Department of Neurology (AU, HH, MY), Graduate School of Medicine, Chiba University; Department of Neurology (YN, KU), Hanamaki General Hospital; Department of Neurology (MM), Tokyo Medical University; Department of Neurology (SK), Toho University Ohashi Medical Center, Tokyo; Division of Health Sciences (T. Kubota, MPT), Department of Clinical Laboratory and Biomedical Sciences, Osaka University Graduate School of Medicine; Department of Neurology (MS), Kindai University Faculty of Medicine, Sayama; Department of Neurology (NK), Neurology Chiba Clinic; Department of Neurology (T. Kimura), Hyogo Medical University, Nishinomiya; Department of Neurology (YS), National Hospital Organization Sendai Medical Center, Sendai; Department of Clinical Neuroscience and Therapeutics (TS), Hiroshima University; Department of Neurology (NM), National Hospital Organization Hokkaido Medical Center, Sapporo; and Department of Neurology (HM), International University of Health and Welfare, Narita, Japan.

Abstract

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.