Abstract 338: A new investigational ATM Inhibitor, M3541, synergistically potentiates fractionated radiotherapy and chemotherapy in cancer cells and animal models

Physical or chemical DNA damaging agents are among the most widely used classes of cancer therapeutics today. Radiotherapy and topoisomerase inhibitors induce double strand breaks (DSB) considered most dangerous if left unrepaired because they can induce growth arrest, chromosomal abnormality and/or cell death. ATM is an essential kinase which orchestrates one of the two major pathways for repair of DSBs via the high fidelity homologous recombination (HR) mechanism. In addition, ATM acts as an upstream signaling kinase, regulating cell cycle checkpoint control in the response to DSB damage. Inhibitors of ATM kinase are expected to suppress DSB DNA repair, block checkpoint controls and enhance the therapeutic effect of radiation therapy and other DSB-inducing treatment modalities. We have developed a novel, highly potent and selective inhibitor of ATM, M3541, which modifies cellular response to DSB damage leading to potentiation of radiation therapy and DSB-inducing chemotherapy. Here, we present data from the preclinical evaluation of M3541 therapeutic potential in cellular and xenograft models of cancer. ATM inhibitor sensitized multiple tumor cell lines to ionizing radiation and a topoisomerase inhibitor in vitro. Oral administration of M3541 to nude mice bearing human tumor xenografts in a clinically relevant radiation regimen strongly enhanced the antitumor activity, leading to complete tumor regression. These activities resulted from inhibition of ATM kinase activity and modulation of its downstream effects in the xenograft tissues. M3541 is currently under clinical investigation in a Phase I trial. Citation Format: Astrid Zimmermann, Frank Zenke, Heike Dahmen, Christian Sirrenberg, Thomas Grombacher, Lyubomir T. Vassilev, Thomas Fuchss, Andree Blaukat. A new investigational ATM Inhibitor, M3541, synergistically potentiates fractionated radiotherapy and chemotherapy in cancer cells and animal models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 338.