Recombinant granulocyte/macrophage-colony stimulating factor in human and murine bone marrow transplantation

Recombinant granulocyte/macrophage-colony stimulating factor (rGM-CSF) is a protein that mediates a broad range of biological activities including inducing proliferation of bone marrow progenitor cells and up-regulating the functional capabilities of neutrophils, monocytes, and macrophages. We have administered rGM-CSF in vivo in the context of allogeneic (murine) and autologous (human) bone marrow transplantation (BMT). In a murine allogeneic model of T-cell depletion constructed to favor graft failure/rejection of donor marrow, ex vivo treatment of marrow with rGM-CSF significantly promoted engraftment. However, when rGM-CSF was infused in vivo, engraftment was significantly impaired. We have initiated a phase I clinical trial of rGM-CSF in human autologous BMT for patients with acute lymphoblastic leukemia (ALL). rGM-CSF has been administered for 14-21 days in a dose escalation study (16-128 micrograms/M2/day). At high doses of rGM-CSF, neutrophil recovery has returned earlier and to higher levels than previously observed in historical controls. rGM-CSF related toxicity in this study has been mild.