Abstract 559: Preclinical characterization of the bispecific EGFR/CD16A innate immune cell engager AFM24 for the treatment of EGFR-expressing solid tumors

Affimed has engineered AFM24 based on its Redirected Optimized Cell Killing (ROCK®) platform to redirect innate immune cells to EGFR-positive tumor cells with the potential for activation of a broad anti-tumor immune response. This fully human tetravalent bispecific EGFR and CD16A binding antibody was designed for the treatment of EGFR-expressing malignancies with the potential to overcome the resistance to other EGFR-targeting agents and offering a better safety profile. The efficacy of current standard of care (SOC), including EGFR-targeting monoclonal antibodies (mAbs) and tyrosine kinase inhibitors (TKIs), depends on intrinsic or acquired mutations that impact EGFR signal transduction. AFM24 exerts a mutation-independent mechanism of action (MOA), redirecting innate immunity via NK cells or macrophages to EGFR-positive tumor cells. PK analyses of AFM24 revealed a half-life of ~14 days in mice and ~5 days in cynomolgus monkeys. Using radioactively labeled AFM24 in mice, tumor-specific accumulation in subcutaneous human tumors was observed. While binding to CD16A by classical mAbs has low affinity and is further impaired by competition with serum IgG, no substantial changes in the very high binding affinity of AFM24 to NK cells were observed in the presence of IgG. Anti-tumor efficacy has been shown in in vitro cytotoxicity assays and in in vivo tumor models. Due to its MOA, AFM24 was also active against tumor cell lines expressing mutated Ras in in vitro assays. Antibody-dependent cellular phagocytosis (ADCP) of tumor cell lines expressing high levels of EGFR was comparable between AFM24 and classical or Fc-enhanced mAbs, but ADCP of tumor cells with lower EGFR expression mediated by AFM24 was more pronounced. Owing to their MOA of blocking EGFR-induced signaling, the therapeutic use of current SOC is associated with severe side effects such as skin toxicity, potentially limiting its use due to dosing interruptions and/or treatment termination. AFM24 is designed to exhibit a reduced potential to inhibit EGFR signaling, aiming for an improved safety profile. In a 4-week toxicology study in cynomolgus monkeys, no skin or organ toxicity was observed at AFM24 doses between 24 and 75 mg/kg i.v. once weekly. In toxicology studies investigating EGFR-targeting mAbs, e.g. cetuximab, with a similar experimental design, severe toxicities have been observed at those dosages. In summary, AFM24 is a novel, differentiated bispecific innate immune cell engager binding to EGFR and CD16A, thereby redirecting tumor cell killing by NK cells and macrophages to EGFR-expressing tumors. Its preclinical characterization described here, encourages AFM24’s development for the treatment of EGFR-expressing tumors with the potential to overcome resistance to current SOC while conferring a favorable safety profile. IND-enabling preclinical development is ongoing. Citation Format: Michael Kluge, Uwe Reusch, Stefan Knackmuss, Torsten Haneke, Susanne Wingert, Michael Damrat, Michael Tesar, Martin Treder. Preclinical characterization of the bispecific EGFR/CD16A innate immune cell engager AFM24 for the treatment of EGFR-expressing solid tumors [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 559.