EGFR/CD16A tetravalent bispecific antibody AFM24 to engage NK-cells to kill EGFR expressing tumor cells and safety results in cynomolgus monkey studies.

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e14001 Background: The epidermal growth factor receptor is a target for the treatment of solid tumors, like CRC, HNSCC and NSCLC. Therapeutic success of EGFR-targeting agents depends on mutations defining resistance to these agents, thus an effective EGFR-targeting therapy overcoming resistance would offer an attractive new treatment option. Natural killer (NK-) cells play a central role in the innate immune system and can destroy cancer cells. NK-cell-engaging bispecific antibodies may offer a safe and effective therapy to target EGFR-expressing tumor cells irrespective of their mutational status. Methods: AFM24 was generated using proprietary human anti-EGFR and anti-CD16A variable domains and characterized for binding, stability, manufacturability, efficacy and safety in biophysical and functional assays in vitro and in vivo. Assays for binding to target/effector cells and cytotoxicity were performed in the presence of physiologically relevant IgG levels using EGFR+ tumor cell lines with and without RAS. The safety profile of AFM24 was investigated in vitro for off-target activity and in vivo in cynomolgus monkeys. Results: AFM24 showed excellent biophysical properties and picomolar EC50 values in cytotoxicity assays. It was more potent than cetuximab, or an antibody with cetuximab-derived anti-EGFR variable domain. Importantly, AFM24 was less prone to IgG interference and eliminated cell lines harboring negative predictive biomarkers in in vitro cytotoxicity assays, even in the presence of relevant serum IgG levels. AFM24 demonstrated in vivo efficacy in a humanized hu-NOG mouse model. Furthermore, AFM24 exhibited a favorable safety profile in cynomolgus monkeys. It was well tolerated up to 94 mg/kg in a single dose, maximum tolerated dose study (MTD) when administered as a 2 hour infusion. Conclusions: Our data suggest that AFM24 is a highly potent and potentially safer drug candidate suitable for the treatment of EGFR-expressing cancers with the potential to overcome resistance to other EGFR-targeting agents and to avoid toxic side effects seen with other anti-EGFR therapeutics.