Abstract 2203: Targeting monoclonal antibodies to the tumor microenvironment for cancer immunotherapy

Abstract

Abstract Therapeutic antibodies and immune checkpoint inhibitors can be delivered more efficiently to the tumor microenvironment (TME) by targeting the exposed collagenous (XC) proteins at the site/s of tumor invasion, stroma formation, and neoangiogenesis.Purpose: To assess the ability of bifunctional fusion polypepetides (mAb-Tropins) to selectively deliver monoclonal antibodies (mAbs) to the TME in tumor-bearing nude mice.Materials and Methods: Synthetic peptide probes and polypeptide aptamers (25-45 aa), fluorescein-labeled IgGs, and an anti-VEGF human mAb were tested in vitro in exposed collagen (XC)-agarose binding assays, in HUVEC cultures, and in vivo in a human xenograft model of pancreatic cancer in nude mice.Results: The XC-targeted mAb-Tropins, bound non-covalently to FITC-labeled IgGs [but not to truncated F(Ab’)2 fragments], exhibited selectivity for XC-agarose over control agarose matrices. Importantly, the biological activity of the XC/mAb-Tropin-bound anti-VEGF mAbs was fully preserved, as demonstrated by inhibition of endothelial cell proliferation in HUVEC cultures. In vivo, intense fluorescence was observed in tumors of mice injected with mAb-Tropin targeted IgGs at 15 and 60 minutes after intravenous injection, but not in non-targeted IgG-treated mice (see Figure below).Conclusions: Tumor XC-targeted mAb-Tropins are an effective method of delivering therapeutic mAbs precisely to the tumor compartments, with meaningful implications for cancer immunotherapy. Figure Figure Legend: The performance of mAb-Tropin 277 is evaluated in vitro in XC-binding assays and in vivo in a murine xenograft model of metastatic cancer. XC-agarose chromatography using mAb-Tropin 277 and FITC-IgGs, followed by stringent washing and analysis of column eluates and retentates (A,B), demonstrates aptamer-dependent binding of IgGs to XC-proteins (retentates), as well as depletion of the fluorescent IgGs from solution (column pass-through). The mAb-Tropin 277 dependent targeting of fluorescent IgGs (via the systemic circulation) to tumors is demonstrated in a murine metastatic cancer model (C). Taken together with the in vitro binding data—which showed that the bifunctional mAb-targeting onco-aptamers efficiently sequester IgGs (A) and concentrate the bound IgGs on collagen matrices (B)—this in vivo data indicates that mAb-Tropins concentrate and compartmentalize IgGs/mAbs within the TME (C). Citation Format: Frederick L. Hall, Sant P. Chawla, Neal S. Chawla, Erlinda M. Gordon. Targeting monoclonal antibodies to the tumor microenvironment for cancer immunotherapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2203.