Clinical trials with haemopoietic growth factors

Five glycoprotein growth factors capable of stimulating the proliferation and differentiation of haemopoietic progenitor cells in vitro have been identified and sequenced over the past ten years. Recombinant DNA technology has recently enabled the production of sufficient amounts of these agents for preclinical testing. Erythropoietin (EPO), granulocyte-macrophage colony-stimulating factor (GM-CSF), and granulocyte colony-stimulating factor (G-CSF) have already entered clinical studies in humans. Interleukin-3 (IL-3) and macrophage colony-stimulating factor (M-CSF) should soon be available for use in humans. EPO corrects the anaemia of end stage renal failure, improving the quality of life for such patients and preventing the need for red cell transfusions. At high dose it increases platelet production in vitro and in vivo and may be of value in humans to prevent the thrombocytopaenia associated with chemotherapy. G-CSF and GM-CSF have been used in several clinical studies. Administration of both growth factors results in a leucocytosis, G-CSF predominantly increasing neutrophil production and GM-CSF increasing production of neutrophils, eosinophils and monocytes. The optimal administration of these agents is via continuous intravenous infusion or daily subcutaneous injections at doses of 3-10 micrograms/kg/24 h. GM-CSF has shown promising results in patients with AIDS and the myelodysplastic syndrome and both G-CSF and GM-CSF have reduced the duration of neutropaenia and incidence of infection associated with chemotherapy. These agents may allow an escalation of the dose-intensity of chemotherapy in the future and thereby, hopefully, increase the response rate and survival for patients with a variety of neoplasms. Several other potential roles for these haemopoietic growth factors are discussed.