Abstract 4831: Using reporter-based bioassays and engineered TNFalpha and VEGF+ target cells to measure Fc-mediated ADCC and CDC activity of anti-TNFá and anti-VEGF therapeutic antibodies

Abstract Fc receptor-mediated effects contribute to the therapeutic response in terms of efficacy and safety of anti-TNF antibodies. Measurement of Fc-mediated antibody-mediated cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC) during antibody drug discovery and development is not only important for antibodies that harness ADCC and/or CDC as their primary mechanism of action (e.g. rituximab, trastuzumab), but also for antibodies designed to target and block soluble ligands such as TNFα and VEGF. We previously reported the development of a cell-based reporter bioassay platform which has been used to measure ADCC and ADCP mediated through FcgRI, FcgRIIa and FcgRIIIa. These reporter bioassays exhibit the specificity, accuracy, precision, and robustness necessary for qualification according to ICH guidelines and have been used extensively to characterize and measure the potency of antibody-based biologics drugs that target cell surface immune receptors. In the current study, we sought to evaluate Fc-mediated ADCC and CDC activities of therapeutic antibodies designed to target and block soluble ligands including TNFa and VEGF. To measure ADCC activity of anti-TNFa and anti-VEGF blocking antibodies, we developed engineered target cells that express either membrane-bound TNFα or VEGF. When used as target cells with reporter-based effector cells expressing a relevant FcgR, ADCC activity of adalimumab (anti-TNFa) and bevacizumab (anti-VEGF) was detected in a specific and dose-dependent manner. Similarly, when used in a luminescence-based CDC assay, the engineered target cells elicited an appropriate FcgR-mediated response. The assay signals demonstrated IgG isotype specificity as IgG4 variants showed minimal activity in both ADCC and CDC assays. Our results demonstrate that the combined use of cell-based reporter bioassays with target cells engineered to express membrane-bound soluble ligands can provide a simple, specific, and quantitative platform to measure Fc-mediated effector functions of therapeutic antibodies targeting soluble ligands. Citation Format: Denise Garvin, Jamison Grailer, Rich Moravec, Jim Hartnett, Chris Heid, Frank Fan, Mei Cong, Jey Cheng. Using reporter-based bioassays and engineered TNFalpha and VEGF+ target cells to measure Fc-mediated ADCC and CDC activity of anti-TNFá and anti-VEGF therapeutic antibodies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4831.