Rapid Serum IgG Reduction as a Potential Indicator of Short-Term Clinical Improvement in AChR-Ab-Positive Generalized Myasthenia Gravis: A Post Hoc Analysis of a Phase III Batoclimab Trial.

INTRODUCTION Generalized myasthenia gravis (gMG) is an autoimmune disorder often associated with anti-acetylcholine receptor antibodies (AChR-Abs). Identifying short-term predictors or indicators of clinical improvement is crucial for optimizing treatment strategies.

Methods

This post hoc analysis utilized data from a phase III, multicenter randomized controlled trial enrolling 65 patients with AChR-Ab-positive gMG across 27 centers in China. We evaluated serum immunoglobulin G (IgG) as a potential short-term indicator of clinical improvement in patients treated with batoclimab. Clinical severity was evaluated using the Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scales. Spearman correlation analyses, mixed-effects models, and multivariate analyses were performed to assess relations between biomarker changes and symptom improvement.

Results

Within-patient Spearman correlation showed significant associations between reductions in IgG or AChR-Ab levels and symptom improvement (ΔIgG vs. MG-ADL change: r = 0.372, p < 0.001; ΔIgG vs. QMG change: r = 0.492, p < 0.001). Mixed-effects modeling indicated that an 80% reduction in IgG corresponded to a 59% probability of MG-ADL improvement by ≥ 3 points and a 77% probability of QMG improvement by ≥ 3 points. High baseline body mass index (BMI) was identified as an independent risk factor for slower IgG decline.

Conclusion

Batoclimab rapidly reduced IgG and pathogenic AChR-Ab levels, leading to improved clinical outcomes in patients with gMG. The reduction rate in total IgG may serve as a valuable short-term indicator of clinical response in patients with AChR-Ab-positive gMG following neonatal fragment crystallizable receptor antagonist therapy. TRIAL REGISTRATION ClinicalTrials.gov Identifier NCT05039190.