Pritumumab Binding To Glioma Cells Induces Adcc And Inhibits Tumor Growth.

e14004 Background: Pritumumab is a natural human IgG1 kappa antibody originally isolated from a regional draining lymph node of a patient with cervical carcinoma. This antibody binds ectodomain vimentin on the surface of tumor cells and has demonstrated some benefit to glioblastoma patients in limited clinical trials. We wanted to determine if pritumumab inhibits glioma growth in vivo and if binding to glioma cells induces cell-mediated immunity. Methods: Pritumumab was used in flow cytometry experiments with several glioma cell lines and patient-derived neurosphere lines. Antibody-dependent cell-mediated cytotoxicity (ADCC) reporter assay was used with glioma target cells. Xenograft studies were performed in mice with and without intact B- and NK- cells. Results: We performed flow cytometry using pritumumab antibody and demonstrate binding of pritumumab to the surface of glioma cells and patient-derived glioma initiating cells. We observed significant induction of ADCC by pritumumab binding to glioma cells. Xenograft studies demonstrated pritumumab was effective in preventing tumor growth in nude mice but not in SCID mice. Intact cell-mediated immunity was necessary for pritumumab’s anti-tumor effect. Analysis of a blood brain barrier model showed significant binding of pritumumab in brain tumor areas and minimal distribution in normal brain tissues suggesting the antibody can cross the blood brain barrier. Conclusions: Our data demonstratepritumumab binds glioma cells in vitro and can induce ADCC. In addition, pritumumab can limit the growth of xenograft glioma tumors in vivo only in the presence of intact cell-mediated immunity. Together these data suggest pritumumab is suitable for development as an anti-tumor therapeutic.