Combined effects of granulocyte-macrophage colony stimulating factor with erythropoietin in subhuman primates.

Recently, we showed in a cynomolgus monkey model that the combination of interleukin-3 (IL-3) and granulocyte-macrophage colony stimulating factors (GM-CSF) demonstrates synergistic effects, if administered sequentially. Not only were progenitor cells of the myelocytic lineage stimulated cooperatively, but platelet release was also observed. These effects could not be found using these factors alone. In this study, GM-CSF was administered with erythropoietin (EPO) in a sequential manner. This treatment of GM-CSF and EPO resulted in a GM-CSF-stimulated increase in cells of myelomonocytic differentiation, and enhanced stimulation of erythroid and megakaryocytic lineages. The observed effects of growth factor combination were seen to the same extent with intravenous or subcutaneous administration. The results obtained may predict the potential usefulness of GM-CSF treatment together with EPO. This could improve the effectiveness of single growth factors in only limited indications, e.g., reduced need for transfusion (platelets, blood), correction of iatrogenic anemia, and recovery from myelosuppression due to chemo- and radiotherapeutic agents.