M281, an Anti‐FcRn Antibody: Pharmacodynamics, Pharmacokinetics, and Safety Across the Full Range of IgG Reduction in a First‐in‐Human Study

M281 is a fully human, anti‐neonatal Fc receptor (FcRn) antibody that inhibits FcRn‐mediated immunoglobulin G (IgG) recycling to decrease pathogenic IgG while preserving IgG production. A randomized, double‐blind, placebo‐controlled, first‐in‐human study with 50 normal healthy volunteers was designed to probe safety and the physiological maximum for reduction of IgG. Intravenous infusion of single ascending doses up to 60 mg/kg induced...