Analysis of hybridoma and CHO-derived pritumumab for therapeutic applications.

Abstract

71 Background: Pritumumab, a natural huma IgG1 kappa antibody was obtained from a regional draining lymph node of a patient with cervical carcinoma through traditional hybridoma technology. Methods: Both cell lines and tissues were processed and analyzed for FACS analysis, Western blots, and immunohistochemistry. Results: Specificity analysis of the target antigen, an altered form of vimentin (ecto-domain vimentin (EDV)) shows it to be limited to cell surface expression on cancer cells. Clinically, 249 Japanese brain cancer patients were treated with a low dose pritumumab regimen, either at 1mg once a week or 1mg twice a week, and overall response rates of between 25-30% were seen with several complete and partial responses. A recombinant version of the mAb was made using the GPEx system in CHO cells. In a series of comparable studies the CHO mAb was compared with the original hybridoma. Binding specificity with both flow cytometry and immunohistochemical (IHC) analysis, Western blot analysis, and Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC) activity confirms the comparability of the two versions. IHC analysis suggests restricted binding to tumor cells and not normal cells and tissues. Further studies include establishing a xenograft model with both SCID and athymic nude mice in which pritumumab was effective in preventing tumor growth in nude mice but not in SCID mice. Analysis of a blood brain barrier model suggests pritumumab shows minimal distribution in normal brain tissues and significant binding in tumor areas of brain tissues indicating the mAb crosses the tumor brain barrier. Conclusions: Overall, these data together suggest pritumumab is suitable for development as an anti-tumor therapeutic.