Several hematopoietic growth factors (HGFs) have achieved widespread clinical application. In the United States alone, more than US $5 billion per year of the health care budget is spent on these factors. The first patients were treated with recombinant human erythropoietin (rHuEPO, epoetin alfa, Epogen®) in 1985 and the first patients received recombinant methionyl human granulocyte colony-stimulating factor (r-metHuG-CSF, filgrastim, Neupogen®) or recombinant human granulocyte-macrophage colonystimulating factor (rHuGM-CSF, sargramostim, Leukine® or Prokine®) in 1986. The first agent promoting platelet recovery was formally approved in 1997 (recombinant human interleukin-11 [rHuIL-11], oprelvekin, Neumega®). In 2002, sustained-duration derivative r-metHuG-CSF (pegfilgrastim, Neulasta®) was formally approved for clinical use
