Humanized Hepsin Neutralizing Antibody Ro5486055 Inhibits Tumor Growth And Leads To Accumulation Of Hepsin Substrate Laminin-332

Hepsin is overexpressed in prostate and other cancers where it is implicated in promoting tumor growth, invasion, and metastasis. To further our understanding of the role of hepsin in prostate and breast cancer, a fully humanized monoclonal antibody that recognizes human and cynomolgus hepsin has been developed. RO5486055 selectively binds to hepsin but not related type II transmembrane serine proteases, and neutralizes hepsin serine protease activity with an IC 50 in the single digit nM range. In LNCaP prostate cancer cells, both shRNA knockdown of the hepsin gene and RO5486055 treatment cause a similar accumulation of the β3 chain of laminin-332, a known hepsin substrate. With ip administration in mice, RO5486055 demonstrates dose-dependent exposure and a long serum half-life of 168-406 hours. RO5486055 attenuates tumor growth in the LNCaP prostate cancer and T-47D breast cancer xenograft models, but not in the CRW-22Rv1 prostate or MCF-7 breast cancer xenografts. In these models, it has been shown that the level of the β3 chain of laminin-332 detected by Western blot analysis predicts sensitivity to RO5486055-mediated growth inhibition. Moreover, accumulation of the β3 chain during RO5486055 treatment correlates with antitumor activity. In 8/10 hepsin-expressing patient-derived prostate tumors, an inverse correlation between hepsin and β3 chain expression is observed. The β3 chain of laminin-332 may therefore be useful as both a predictive and response biomarker for anti-hepsin therapy. RO5486055-mediated tumor growth inhibition is enhanced by combination with the EGFR-targeted antibody cetuximab in LNCaP prostate cancer xenografts, and by combination with hormone withdrawal in T-47D breast cancer xenografts. These preclinical results suggest that hepsin-directed therapy could be effective in prostate and breast cancer treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4827. doi:1538-7445.AM2012-4827