Abstract 689: Anti-tumor activity of <i>Bifidobacterium</i> secreting dual specific T cell redirecting antibody against EGFR/HER3-expressing cancer

<jats:title>Abstract</jats:title> <jats:p>Anti-cancer therapies targeting EGFR family, including monoclonal antibodies and kinase inhibitors, are the state of art for solid tumors such as colorectal and non-small cell lung cancers. T cell redirecting bispecific antibodies are a promising approach for cancer immune therapy, whereas their application is limited to hematological malignancy due to adverse events caused by the systemic exposure to highly immunologically active molecule.</jats:p> <jats:p>To avoid the immunological adverse events, we have created a recombinant Bifidobacterium (APS002) that specifically colonizes in solid tumor and continuously secretes T cell redirecting antibody. The antibody was designed to form a diabody based on the sequence of dual specific antibody for EGFR/HER3 and CD3.</jats:p> <jats:p>The diabody (termed DBERB1) comprises the equal amount of two polypeptides, anti-h CD3 (VL) - anti-EGFR/hHER3 (VH) and anti-hEGFR/hHER3 (VL) - anti-hCD3 (VH), respectively. DBERB1 bound to human EGFR and HER3, and human CD3. DBERB1 demonstrated potent cytotoxic activities against EGFR- and HER3-expressing human colon cancer HCT116 cells in the presence of human peripheral blood mononuclear cells (hPBMC) with EC50 values of 3 - 9 × 10−12 M. When APS002 was i.v. dosed to HCT116 tumor-bearing SCID mice inoculated with hPBMC, APS002 colonized only in the tumor and DBERB1 was detected in the tumors but not in the plasma. The growth of HCT116 tumors was significantly suppressed by APS002 but not by Bifidobacterium transfected with control vector.</jats:p> <jats:p>In conclusion, our study in the mouse model indicates that APS002 is a novel and an extremely potent anti-cancer agent distributed only in the tumor. We are currently preparing for pre-clinical studies for the future clinical trials.</jats:p> <jats:p>Citation Format: Satoshi Kobayashi, Koichiro Shioya, Yuji Seki, Tomio Matsumura, Yasuyoshi Kanari, Yuko Shimatani, Hikaru Nakazawa, Mitsuo Umetsu, Shiro Kataoka, Takaaki Nakamura. Anti-tumor activity of Bifidobacterium secreting dual specific T cell redirecting antibody against EGFR/HER3-expressing cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 689.</jats:p>