Abstract 6358: Arming tumor-associated macrophages to inhibit cancer progression

Abstract Integrin αvβ3 is a marker of cancer progression in a range of epithelial cancers. In the 1990s, a humanized anti-αvβ3 antibody (Etaracizumab) was developed to target αvβ3+ cancer cells via NK cell-mediated cytotoxicity. While it demonstrated safety and some efficacy in clinical trials, our recent study of the immune microenvironment in αvβ3+ human epithelial tumors revealed increased tumor-associated macrophages (TAMs) but minimal NK cell accumulation. Accordingly, we re-engineered Etaracizumab to favor TAM engagement over NK cells and compared the efficacy of this antibody (ABT101) to that of Etaracizumab in various αvβ3+ epithelial cancer models. While ABT101 and Etaracizumab exhibited identical affinity for αvβ3, ABT 101 showed superior anti-tumor activity in vivo. Notably, depleting NK cells in mice had no impact on ABT101’s effectiveness, while macrophage depletion completely abolished its anti-tumor activity. Interestingly, tumors in mice treated with ABT101 displayed a significant increase in TAMs. Here we define an “antigen-effector cell matching” strategy that allows for maximal anti-tumor activity for various drug resistant epithelial cancers. ABT101 will enter clinical trials for patients with drug resistant lung cancer in the first quarter of 2024. Citation Format: Joshua P. Reddy, Ziqi Yu, Ryan M. Shepard, Tami Von Schalscha, Stephen J. McCormack, Sara M. Weis, David A. Cheresh, Hiromi I. Wettersten. Arming tumor-associated macrophages to inhibit cancer progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6358.