ACVR2B and myelodysplastic syndrome: Luspatercept, previously known as ACE-536, is a modified activin receptor type IIB ligand trap (ActRIIB) which is currently being tested for use in diseases characterized by ineffective erythropoiesis, such as beta-thalassemia (β-thalassemia), myelodysplastic syndromes (MDS) and primary myelofibrosis (PMF) [1,2,3].