Abstract 4830: ABX9xx: A bispecific centyrin that synergizes to attenuate intracellular signaling in Met/EGFR positive tumors

ABX9xx is a bispecific Centyrin targeting the Met-EGFR axis, an emerging cancer treatment paradigm. Centyrins are small, chemically simple proteins based on a human FN3 domain that can be engineered to have high affinity for a selected target and are easily linked to form multi-specific binders. The standard of care for patients with EGFR mutant non-small cell lung cancer (NSCLC) is treatment with small molecule tyrosine kinase inhibitors (TKI) including recently approved third generation molecules (ie. osimertinib). Despite initial promising responses with TKIs, most patients regress within 12-14 months due to resistance. A predominant resistance mechanism dependent on Met amplification and signaling has been described from both in vitro experiments and clinical data. Targeting Met and EGFR with a bispecific ligand blocking inhibitor that attenuates intracellular signaling may provide a significant efficacy advantage and reduced side effect profile compared to small molecule TKI combinations. Exploiting the potential for avidity on tumor tissue, a bispecific ligand blocking inhibitor of Met and EGFRis also anticipated to provide improved selectivity for tumor tissue that overexpress both receptors compared to normal tissue with lower receptor expression. To enable sustained exposure while maintaining small size for good tumor penetration, ABX9xx includes a domain comprising an albumin binding Centyrin. ABX9xx activity on Met, EGFR and downstream signaling proteins was confirmed on several lung cancer cell lines in vitro including those carrying clinically observed mutations in Met and EGFR. ABX9xx inhibited EGFR phosphorylation independent of EGFR mutational status with higher potency than osimertinib. In addition, ABX9xx inhibited Met phosphorylation with higher potency than Crizotinib, an ALK inhibitor with cross reactivity to Met, currently used to treat Met positive patients. The pharmacokinetic properties of ABX9xx in animal models suggest a suitable dosing paradigm in patients. Together the data provides a strong rationale for advancing ABX9xx into clinical development for NSCLC and other cancers where EGFR and MET are drivers of tumor progression. Citation Format: Russ Addis, Robert Kolakowski, Swapnil Kulkarni, Josh Gorsky, Rebecca Meyer, Karyn ONeil. ABX9xx: A bispecific centyrin that synergizes to attenuate intracellular signaling in Met/EGFR positive 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 4830.