Momenta Pharmaceuticals Inc., of Cambridge, Mass., dosed the first healthy volunteers in a phase I randomized, double-blind, placebo-controlled, ascending-dose cohort study to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of M281, an anti-FcRn monoclonal antibody, for the treatment of autoimmune diseases. In preclinical models, M281 potently antagonizes FcRn binding of IgGs and rapidly diminishes circulating levels of IgG antibodies, the primary pathogenic agent in a number of autoimmune diseases. The study will enroll up to approximately 72 healthy volunteers.