Abstract 2657: Preclinical model to evaluate the safety and efficacy of PODO83: A monoclonal antibody against podocalyxin that targets tumor growth and metastasis

Abstract

Abstract Podocalyxin (PODXL) is a highly glycosylated transmembrane sialomucin normally found on the apical free surface of mesothelial, vascular endothelial, luminal mammary epithelial cells, kidney podocytes and pluripotent and hematopoietic stem cells. We were the first to show that PODXL is upregulated on human cancers and an independent predictor of poor prognosis in breast and high-grade serous ovarian carcinoma (HGSOC). We also demonstrated that PODXL expression is crucial for primary tumor growth, local invasion, and experimental metastasis to distant organs. Subsequently, these results were extended to a wide range of other tumor types. We next developed a large series of high-affinity monoclonal antibodies (mAb) to human PODXL and evaluated these for therapeutic activity against the PODXL+ metastatic breast cancer cell line, MDA-MB-231, in xenografted NOD-SCID IL2Rγ-/- (NSG) mice. One of these, PODO83, potently attenuated primary tumor growth and formation of distal metastases. The PODO83 reactive epitope maps to the juxtamembrane stalk domain (non-glycosylated region) of the PODXL core protein. As a promising therapeutic it is imperative to perform toxicity studies and determine if PODO83 adversely affects the function of PODXL on normal tissues. Accordingly, we generated a transgenic mouse strain (C57Bl/6 congenic) replacing 4 of the 8 mouse PODXL-encoding exons with the orthologous human exons (including those encoding the PODO83 epitope). These mice were healthy and we confirmed by immunohistochemistry that they exhibit appropriate PODO83 immunoreactivity in all expected tissues (podocytes, endothelia, etc). Strikingly, administration of PODO83 in vivo at high doses (4 treatments of 5 mg/kg over 14 days) resulted in no overt signs of toxicity. To now fully assess the safety and efficacy profile of the PODO83 mAb in this preclinical humanized mouse model we have developed mouse metastatic tumor cell line expressing human PODXL and will evaluate the ability of PODO83 to inhibit tumor growth and metastasis while sparing normal tissues in vivo. The results from this study will help us advance PODO83 mAb as a safe and effective approach to treating the wide variety of cancer subtypes that express PODXL. Citation Format: Julyanne Brassard, Michael R. Hughes, Pamela Dean, Diana Canals Hernaez, Janella Schwab, Yasmine Lau, Calvin D. Roskelley, Kelly M. McNagny. Preclinical model to evaluate the safety and efficacy of PODO83: A monoclonal antibody against podocalyxin that targets tumor growth and metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2657.