IL-6 functions in cynomolgus monkeys blocked by a humanized antibody to human IL-6 receptor

A humanized antibody to the human interleukin-6 receptor (IL-6R), hPM-1, blocked the interleukin-6 (IL-6) functions in normal cynomolgus monkey lymphocytes in vitro. The binding activity of hPM-1 to non-human primate IL-6R was examined in peripheral blood lymphocytes by flow cytometry. PM-1 recognized the IL-6R on T lymphocytes of cynomolgus and rhesus monkeys, but did not on those of marmosets. The homology between human IL-6R and its cynomolgus monkey counterpart was 97.3% in the extracellular domain of the amino acid sequence, as determined by DNA sequencing of the PCR product from peripheral blood mononuclear cells. PM-1 inhibited two functional parameters in vitro in cynomolgus monkeys: (1), T-cell proliferation stimulated by phytohemaglutinin and human IL-6; (2), Immunoglobulin G-production evoked by Staphylococcus aureus Cowan-1- and human IL-6-stimulated B lymphocytes. These data show that hPM-1 binds to and functionally blocks the cynomolgus monkey IL-6 receptors.

In vivo blocking effects of a humanized antibody to human interleukin-6 receptor on interleukin-6 function in primates

A humanized antibody to human interleukin-6 (IL-6) receptor, MRA, which was constructed by grafting the complementary determining regions, is expected to be useful as a therapeutic agent for IL-6-related diseases, especially multiple myeloma. We examined the ability of MRA to block the in vivo function of IL-6 and its serum concentration profile in primates. Cynomolgus monkeys were intravenously administered with MRA at doses of 0 (vehicle) or 5 mg/kg, then subcutaneously injected with human IL-6 at a dose of 5 micrograms/kg, once a day for 7 days. The injections of IL-6 increased blood platelet counts two-fold and elevated serum C-reactive protein levels to 0.15 to 0.17 mg/ml. These IL-6-induced typical responses were completely inhibited by single pretreatment with MRA. Serum concentrations of MRA were maintained for a long period; some even at one week after administration, were regarded as having sufficient levels to inhibit the myeloma cell growth. These findings suggest that MRA may be effective in the treatment of IL-6-related diseases.

Safety and kinetic properties of a humanized antibody to human interleukin-6 receptor in healthy non-human primates

A monoclonal antibody, hPM-1, was constructed by grafting the complementarity determining regions to human interleukin-6 (IL-6) receptor, raised in mouse, onto a human antibody backbone (humanized antibody). It is expected to be useful as a therapeutic agent for IL-6-related diseases such as multiple myeloma. To investigate the toxicological and kinetic properties of hPM-1 preliminarily, normal cynomolgus monkeys, which showed cross-reactivity with hPM-1, were intravenously administered with hPM-1 at doses of 0 (vehicle), 4 or 40 mg/kg once a week for 13 weeks. Upon toxicological examination, there were no changes in clinical signs, food consumption, body weights, urinalyses, body temperatures, electrocardiograms, hematological and biochemical parameters including blood platelet counts, serum levels of immunoglobulin G and C-reactive protein, and pathological findings. In a kinetic study, serum concentrations of hPM-1 showed a linearity between doses of 4 and 40 mg/kg. The serum concentrations, even at a dose of 4 mg/kg, were maintained at a high enough level to inhibit the IL-6 functions throughout the period of the study. Concentrations of hPM-1 in bone marrow were almost equal to those in serum. The antibodies against hPM-1 were detected only in one of four monkeys receiving hPM-1. This study suggests that blockage of the IL-6 receptor by hPM-1 does not induce any influence on a healthy living body, and hPM-1 is not toxic under the conditions of this investigation.