Purpose

The primary objectives of this study are: * To confirm the safety and tolerability of magrolimab monotherapy in a relapsed/refractory (R/R) acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) population, and of magrolimab in combination with azacitidine in previously untreated participants with AML or MDS and participants with R/R AML and MDS * To evaluate the efficacy of magrolimab monotherapy in R/R AML/MDS, and of magrolimab in combination with azacitidine in previously untreated participants with AML/MDS, or R/R AML/MDS as measured by complete remission (CR) rate for participants with AML and higher-risk MDS, and duration of complete response for participants with AML and higher-risk MDS, and duration of CR for participants with AML and higher-risk MDS * To evaluate the safety, tolerability, and efficacy of magrolimab monotherapy or combination with azacitidine in low-risk MDS participants as measured by red blood cell (RBC) transfusion independence rate