Improvement in Patient‐Reported Symptoms of Generalised Myasthenia Gravis With Rozanolixizumab in the Randomised Phase 3 MycarinG Study Using the MG Symptoms PRO

ABSTRACT Background In the Phase 3 MycarinG study (NCT03971422), rozanolixizumab improved myasthenia gravis (MG)‐specific outcomes versus placebo in patients with generalised MG, including those measured by the five independent MG Symptoms patient‐reported outcome (PRO) scales: Muscle Weakness Fatigability (MWF), Physical Fatigue (PF) and Bulbar Muscle Weakness (BMW) as secondary endpoints and Ocular Muscle Weakness and Respiratory Muscle Weakness (exploratory endpoints). This research aimed to provide further insights into these improvements. Methods Post hoc analyses evaluated correlation (Pearson coefficient) between MG Symptoms PRO and subdomain scores of MG Activities of Daily Living (MG‐ADL) and Quantitative MG (QMG) at baseline. Proportions of responders reaching clinically meaningful thresholds and analyses at the item level (observed mean change and Rasch modelling of predicted change from baseline) are reported for MWF, PF, and BMW with rozanolixizumab versus placebo at Day 43. Results Correlation coefficients between MG Symptoms PRO and MG‐ADL were strong (≥ 0.7) for ocular and bulbar scores and moderate (0.5 to < 0.7) for other scores. Correlations with clinician‐assessed QMG scores were generally weak (< 0.5). For MWF, PF, and BMW, greater proportions of responders were observed with rozanolixizumab 7 mg/kg (46.9%, 31.3% and 26.6%, respectively) or 10 mg/kg (56.5%, 48.4% and 32.3%) versus placebo (28.1%, 26.6% and 10.9%). Item‐level analyses demonstrated rozanolixizumab benefit at a symptom‐specific level. Discussion MG Symptoms PRO scales correlate well with concepts in MG‐ADL while assessing additional concepts, such as PF and MWF. Results from the MG Symptoms PRO in MycarinG reflected improvements from baseline in patient‐relevant symptoms, including fatigue, with rozanolixizumab.