Clinical Outcomes of Rituximab Infusion Among Refractory Myasthenia Gravis Patients in the Philippines: A 10-Year Retrospective Study

TL;DR

This study shows that rituximab is safe and effective for treating refractory myasthenia gravis in the Philippines, especially for MuSK-positive patients.

Contribution

The study provides real-world evidence of rituximab's efficacy in refractory MG from a low- to middle-income country context.

Findings

50% of patients achieved complete or near-complete remission after rituximab treatment.

MuSK-positive patients showed the most rapid response to rituximab.

Rituximab was well-tolerated with only mild infusion-related reactions.

Abstract

Background: Myasthenia gravis (MG) is an autoimmune disorder causing muscle weakness, with 10%-20% of cases becoming refractory to standard treatments. Rituximab, a CD20-targeting monoclonal antibody, has shown promise in refractory MG but lacks data from low- and middle-income countries (LMICs), such as the Philippines.

Methods: A retrospective, cross-sectional study was conducted in treatment-refractory MG patients in St. Luke’s Medical Center in the Philippines between January 2014 and December 2023. Clinical outcomes were assessed before and after treatment, including MGFA scores, pyridostigmine dosage, and CD19/CD20 levels. Subgroup analyses were performed based on thymectomy and MG antibody status.

Results: Twenty-one MG patients (10 acetylcholine receptor (AChR) positive, eight seronegative, and three muscle-specific kinase (MuSK) positive) were identified. These patients (mean age 46.4 years, 76% female) showed significant improvement post-rituximab, with 50% achieving complete or near-complete remission (MGFA Class I). Pyridostigmine dosage decreased significantly, and CD19/CD20 levels dropped markedly. MuSK-positive patients responded most rapidly, and thymectomy did not considerably impact outcomes. Rituximab was well-tolerated, with mild infusion-related reactions in two patients.

Conclusion: Rituximab is a safe and effective option for refractory MG, especially in MuSK-positive patients, offering a cost-effective alternative in LMICs where treatments like eculizumab are inaccessible.