I. To describe the toxicities and assess the tolerability of recombinant EphB4-HSA fusion protein (sEphB4-HSA) in combination with an approved hypomethylating agent (HMA) among patients with myelodysplastic syndrome (MDS) who are refractory to or have lost their response to one or more HMAs and among patients with relapsed/refractory acute myeloid leukemia (AML) previously treated with a HMA.