Pfizer began enrolling patients in a multicenter Phase II of PF-06252616, an experimental anti-myostatin monoclonal antibody, for the treatment of Duchenne muscular dystrophy (DMD). The study was designed to evaluate the safety, tolerability and efficacy of PF-06252616 in boys aged between six and ten years, with a diagnosis of DMD regardless of genotype. DMD is a genetic disease characterized by progressive muscle degeneration and weakness. Myostatin is a protein that helps muscle growth and it is believed that by blocking its activity could have potential therapeutic application in the treatment of diseases such as DMD. Based on the proposed mechanism of action of PF-06252616, the company is considering whether there is the ability to increase muscle mass and function in boys with DMD who are weak and have lost muscle. The Food and Drug Administration (FDA) has granted orphan drug designation for PF-06252616 in July 2012 and fast track designation in November 2012.