Recombinant human interleukin 3 in clinical oncology

Interleukin 3 (IL-3) is a multipotent hematopoietic growth factor which became available as a recombinant (rh) growth factor for use in the clinic a few years ago. In dose-finding studies, this hematopoietic growth factor has been evaluated without and after standard chemotherapy. Stimulatory effects on leukocytes, neutrophils, eosinophils, monocytes, reticulocytes and platelets were observed in some studies. Chemotherapy postponement due to insufficient bone marrow recovery was less frequent when IL-3 was administered. There are some clinical studies available in which rhIL-3 is combined with rh granulocyte-macrophage colony-stimulating factor (GM-CSF). The results do not clearly suggest superiority of these combinations over rhGM-CSF alone, but this may be partly due to the time scheduling of the growth factors. Administration s.c. is not inferior to i.v. Side effects mainly consist of flu-like symptoms and headache. The role of rhIL-3 after high-dose chemotherapy and autologous bone marrow reinfusion is still questionable. The addition of rhIL-3 to rhGM-CSF both administered after chemotherapy may allow a very high yield of peripheral stem cells suitable for bone marrow reconstitution after high-dose chemotherapy. rhIL-3 can stimulate leukemia tumor cell proliferation in vitro as well as proliferation of solid tumor cell lines. It is not yet clear in which way rhIL-3 combined with chemotherapy will effect tumor response and patient survival. It is too early to define the exact place of rhIL-3 in oncology. Additional studies with rhIL-3 alone and in combination with other growth factors are needed.