Measuring the effect of rozanolixizumab using the Myasthenia Gravis Impairment Index: analyses from the randomized phase 3 MycarinG study

Abstract

Background: Generalized myasthenia gravis (gMG) is an autoimmune disease characterized by fluctuating muscle weakness. The MG Impairment Index (MGII) incorporates patients' perspectives (22 items) and physician evaluation (6 items) of impairment. We evaluated the effect of rozanolixizumab using the MGII in the randomized, double-blind, placebo-controlled, Phase 3 MycarinG study. Methods: Adult patients with gMG were randomized 1:1:1 to once-weekly rozanolixizumab 7 mg/kg, 10 mg/kg or placebo for 6 weeks. MGII assessment was optional. Exploratory MGII analyses included change from baseline (CFB) to Day 43 in total score and ocular/generalized subscores; higher scores reflect greater impairment. Post hoc analyses included responder rates (≥ 5.5-point improvement) and achievement of patient-acceptable symptom state (PASS; ≤ 10 points, patient-reported items only). Results: Overall, 200 patients received rozanolixizumab 7 mg/kg (n = 66), 10 mg/kg (n = 67) or placebo (n = 67). The MGII was completed by 144/200 (72.0%) patients. Mean CFB in MGII total score was greater in the rozanolixizumab groups versus placebo; mean CFB in ocular and generalized subscores was consistent with the total score. At Day 43, 57.1%, 83.3% and 40.4% of patients, respectively, were responders, and 30.8%, 39.2% and 7.7%, respectively, achieved MGII PASS. Responsiveness correlations between MGII total score CFB and MG-ADL anchor at Day 43 demonstrated a Spearman's correlation coefficient of 0.5991 (p < 0.0001). Conclusion: These findings further support efficacy analyses from MycarinG to highlight the benefit of rozanolixizumab in patients with gMG and demonstrate the utility of the MGII in evaluating patient-relevant symptoms following treatment.