593 Effect of OM-163, a new biological response modifier on the immuno-suppression caused by cytostatics and ionizing radiation

Immunosuppression induced by antitumor agents and ionizing radiation is an undesirable side effect of cancer chemo- and radiation therapy. The dose- and time dependent stimulatory effect of OM-163 (cell wall protein extract of E. coli from Lab. OMS. A., Meyrin, Switzerland) on the humoral and cellular immune response was measured and verified by using the plaque forming cell- and rosette forming cell assay. The compensatory effect of OM-163 on the diminished immune response of mice treated with different cytostatic agents (VCR, 5-FU, CisPt) or Co 60 irradiation was studied. OM-163 was generally able to compensate the immunosuppressive effect of cytostatics and radiation treatment without interfering with their antitumor activities. On the basis of our experiences OM-163 may be a potent agent in cancer therapy.