Inhibition of Interleukin-6 (IL-6) Signaling and Tumor Growth by a Human Neutralizing Anti-IL-6 Antibody with a Prolonged Half-Life

Interleukin-6 (IL-6) is a pleiotropic cytokine that plays a major role in responding to injury or infection as well as immune response, inflammation, and hematopoiesis. High levels of circulating IL-6 are observed in many tumor types and are associated with poor outcomes. We show that knockdown of IL-6 or IL-6 receptor (IL-6R) inhibits IL-6 signaling and cell viability. In contrast, over-expression of IL-6 enhances tumor growth in vitro and in vivo, thereby supporting the role of IL-6 in tumorigenesis. We developed a human monoclonal antibody against human IL-6 (MEDI5117) that bears Fc mutations (YTE) to extend its half-life. We tested this antibody in several cancer cell lines that secrete high levels of IL-6, soluble IL-6R, and express gp130. High constitutive pSTAT3 (phosphorylated signal transducer and activator of transcription 3) activation is seen in several of these cell lines, suggesting autocrine growth stimulation by IL-6. Treating these cell lines with MEDI5117 effectively blocked phosphorylation of STAT3 and inhibited IL-6-induced cell proliferation. In vivo, MEDI5117 suppressed the growth of multiple cancer xenograft models and specifically modulated IL-6 signaling and downstream gene expression. Combining MEDI5117 with chemotherapy or gefitinib demonstrated significantly enhanced anti-tumor activities in vivo. Taken together, our data suggest that IL-6 signaling contributes to tumor growth, thereby supporting the development of MEDI5117 as a therapy to treat solid tumors. Xenograft tumors from DU145, KPL4, and NCI-H1650 were treated with 30 mg/kg of MEDI5117 or IgG isotype control IgG1 for a total of two doses. Differentially expressed genes were identified and canonical pathway enrichment analysis was performed