Purpose

This is a Phase 2, multicenter, open-label study to evaluate the efficacy and safety of luspatercept in subjects with MPN-associated myelofibrosis and anemia with and without RBC-transfusion dependence. The study is divided into a Screening Period, a Treatment Period (consisting of a Primary Phase, a Day 169 Disease Response Assessment, and an Extension Phase), followed by a Posttreatment Follow-up Period.