CD33 and myelodysplastic syndrome: In addition, MDSCs express high levels of CD33, and therapies directed against CD33 to deplete MDSC counts in the bone marrow are in development, including both a monoclonal antibody against CD33 (BI 836858) that has been evaluated in preclinical models [84] and a novel bispecific tetravalent antibody against CD33 and CD3 (AMV564) that is being evaluated in a phase 1 study in patients with intermediate- or high-risk MDS after HMA failure (NCT03516591 [85]).