Interleukin-6 induction by a muramyltripeptide derivative in cancer patients.

Interleukin-6 (IL-6) was measured in sera from 26 patients with advanced malignancies before and after an I.V. infusion of muramyltripeptide-phosphatidylethanolamine (MPT-PE) in liposomes. Significantly elevated IL-6 could be measured 2 and 4 h after medium (0.25-0.5 mg/m2) and high (1.0-6.0 mg/m2) doses of the drug accompanied by a rise in body temperature. The biological activity of IL-6 in sera could be inhibited in vitro by monoclonal antibodies against IL-6. Other biological effects of MTP-PE in vivo such as leukocytosis and elevated acute phase reactants are discussed in view of increased IL-6 levels. It is concluded that MTP-PE in liposomes generates increased amounts of IL-6 measurable in serum several hours after administration. IL-6 could therefore play an important role in the biological response modification induced by the drug.