Abstract A59: A novel bispecific FAP-DR5 antibody inducing potent and tumor-specific death receptor 5 (DR5) activation by fibroblast activation protein (FAP) dependent crosslinking

Abstract

Abstract Background: Activation of the extrinsic apoptosis pathway in tumor cells through agonistic death receptor 5 (DR5) antibodies has been evaluated in the clinic with limited success so far. In this context, several reports show that DR5 activation is strongly dependent on receptor hyperclustering on the cell surface. Therefore a therapeutic principle that induces DR5 hyperclustering specifically at the tumor site may provide superior efficacy, potency and safety compared to conventional DR5 agonistic antibodies. Fibroblast activation protein (FAP) is a marker for activated fibroblasts and abundantly expressed in cancer associated fibroblasts of various epithelial tumor indications and as a tumor antigen on tumors of mesenchymal origin. Due to its relative absence from normal tissues, FAP can be used as a tumor targeting antigen. Here, we are using the broad expression of FAP in tumor stroma for crosslinking of DR5 by a bispecific antibody. Aim: In order to achieve superior tumor targeting and tumor located DR5 hyperclustering we have generated a bispecific antibody, RG7386, comprised of an agonistic DR5 binder and a FAP targeting moiety. Results: RG7386 shows potent and selective binding to FAP and DR5 and can simultaneously bind to both targets. In in vitro co-culture assays, using human DLD1 colon tumor cells and FAP expressing fibroblasts, RG7386 induces potent, FAP dependent DR5 hyperclustering and apoptosis induction in DR5 positive tumor cells (IC50: 0.05 nM). In preclinical in vivo models with co-injection of DLD-1 tumor cells and fibroblasts as well as patient-derived colorectal cancer models, RG7386 shows FAP dependent efficacy and apoptosis induction superior to conventional DR5 antibodies. Furthermore the superior induction of apoptosis could be confirmed by in vivo and ex vivo analysis of cleaved Caspase-3 with imaging, Luminex and histopathology. Conclusion: RG7386 is a promising novel therapeutic entity for the treatment of solid tumors with FAP positive tumor stroma inducing DR5 activation by FAP dependent DR5 hypercrosslinking which results in potent anti-tumor activity. Citation Format: Katharina Wartha, Barbara Weiser, Thomas Friess, Meher Majety, Valeria Runza, Frank Herting, Thomas Weber, Werner Scheuer, Suzana Vega Harring, Hadassah Sade, Huifeng Niu. A novel bispecific FAP-DR5 antibody inducing potent and tumor-specific death receptor 5 (DR5) activation by fibroblast activation protein (FAP) dependent crosslinking. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr A59. doi:10.1158/1538-7445.CHTME14-A59