RecruitingPhase 2Drug trialA Study of Elritercept Alone or Together With Ruxolitinib in Adults With MyelofibrosisThe main aim of this study is to learn how safe elritercept is and how well it is tolerated when taken alone and in combination with the JAK inhibitor, ruxolitinib. Other aims are to learn about the effects of elritercept on the signs and symptoms of MF when taken with or without ruxolitinib and to learn how elritercept affects the body, how the body processes elritercept, and the effects of elritercept on anemia when taken with or without ruxolitinib The study will also check on how safe elritercept is and how well it is tolerated.