Eculizumab in thymoma-associated myasthenia gravis: a real-world cohort study

Abstract

Background: Thymoma-associated myasthenia gravis (TAMG) is a subtype of myasthenia gravis (MG) that is associated with more severe symptoms and a relatively poor prognosis. Eculizumab, an inhibitor to target human C5 component of the complement cascade, is considered a treatment option for refractory generalized MG (gMG). Objectives: To explore the safety and efficacy of eculizumab in patients with TAMG. Design: This is an observational multicenter real-world cohort study to assess TAMG who were treated with eculizumab from June 2023 to June 2024. Data sources and methods: Clinical features associated with thymoma-associated multi-organ autoimmunity (TAMA), Myasthenia Gravis Activities of Daily Living (MG-ADL) score, and the incidence of treatment-emergent adverse events (TEAEs) were prospectively collected. Results: Overall, 42 patients with gMG were treated with eculizumab at 5 research centers, of whom 22 patients with TAMG were finally included. This cohort had a mean age of 51.5 ± 12.1 years and an average disease duration of 4.0 ± 4.3 years. Regarding thymomas, the World Health Organization (WHO) histological classification was primarily B2 and B3 (63.7%), and Masaoka staging was predominantly IV (45.5%). Nine participants (40.9%) switched from efgartigimod to eculizumab aiming at a better clinical improvement and reducing steroid use. By week 12, the MG-ADL score decreased to 4.8 ± 4.7 (baseline: 11.7 ± 6.0), and the corticosteroid dose reduced to 23.2 ± 26.5 mg (baseline: 41.8 ± 63.9 mg). Two patients with TAMA showed significant improvement in skin lesions and thrombocytopenia. Two TEAEs were recorded including COVID-19 and herpes labialis infection. Four patients (18.2%) died of respiratory or circulatory failure owing to thymoma metastasis. Conclusion: This real-world study demonstrates the efficacy of eculizumab in achieving symptom control and corticosteroid reduction for TAMG. It may also be a therapeutic option for refractory TAMG and TAMA. Trial registration: NCT04535843.