Additional Study Information: The purpose of this study is to test the safety of an experimental drug called Hu5F9-G4 in patients with blood cancers such as acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). This study will enroll 2 different groups of patients: Relapsed/Refractory (R/R) and Treatment-nave Unfit (TN/U). The use of Hu5F9-G4 in this research study is experimental, which means that the U.S. Food and Drug Administration (FDA) or European Medicines Agency (EMA) has not approved its use for cancer treatment or treatment of any other disease.