Abstract
BACKGROUND AND OBJECTIVES: Biologics that target pathogenic antibodies (Abs) and their effector functions such as the complement inhibitor ravulizumab and the neonatal Fc receptor agonist efgartigimod have recently been approved for the treatment of acetylcholine receptor (AChR)-Ab-positive myasthenia gravis (MG), but comparative studies are lacking. METHODS: In a prospective, exploratory real-world study, we assessed clinical efficacy, safety, and biological effects of ravulizumab and efgartigimod treatment initiation. Myasthenia Gravis-Activities of Daily Living and Quantitative Myasthenia Gravis scores were used as clinical endpoints. Ab effector functions were determined by AChR-Ab-dependent complement activation and phagocytosis assays and systemic complement activation profiling. RESULTS: We observed similar moderate short-term efficacy of ravulizumab and efgartigimod in achieving clinical improvement. Ravulizumab reduced systemic terminal complement activation, but neither treatment showed significant effects on complement pathways proximal to C5 or functional capacities of AChR-Abs. Both treatment modalities were well tolerated with no serious adverse events reported. DISCUSSION: Clinical benefits obtained with ravulizumab and efgartigimod can be remarkably heterogeneous in daily clinical practice. Neither treatment relevantly changed effector functions of pathogenic AChR-Abs, supporting the concept that durable disease control in MG requires continuous administration of both fast-acting agents. CLASSIFICATION OF EVIDENCE: This study provides Class III evidence that in AChR-Ab-positive patients with generalized MG, ravulizumab and efgartigimod provide comparable modest improvement in MG functional scales.