Abstract 1569: OXC-101 kills cancer by disturbing microtubule polymerization and inhibiting MTH1

Abstract Many cancers suffer from replication stress, oxidative stress, a dysfunctional redox status, and high levels of endogenous oxidative DNA damage. OXC-101 (karonudib, TH1579) targets these vulnerabilities by stopping the cancer cells in mitosis, generating ROS which increases oxidative stress and oxidative DNA damage, thereby killing the cancer cells. The aim of this study was to further investigate the underlying mechanism of OXC-101 and the cancer specific effects in solid cancers. Using e.g. microtubule polymerization assays, co-immunoprecipitation and immunofluorescence microscopy, we show a dual mechanism of action of OXC-101, disturbing microtubule function and inhibiting the nucleotide pool sanitizing enzyme MTH1. Furthermore, we demonstrate the importance of a functional spindle assemble checkpoint (SAC) for the response of OXC-101, since knocking down MAD2,using siRNA, or inhibiting SAC with reversine, results in treatment resistance. We show that the excess of oxidized nucleotides is cytotoxic when inhibiting or knocking out MTH1 in zebrafish embryos, and that pretreatment with ROS scavenger rescues the effect of OXC-101 in cancer cells. These data indicate that the increased incorporation of oxidized nucleotides into DNA is, together with the mitotic arrest, an important part of the mechanism of action and response. OXC-101 has a broad anti-cancer effect. In an ex vivo drug sensitivity study of 157 primary biopsies from solid cancer patients, OXC-101 was efficacious in a large proportion of the patient derived samples, with best responses in endometrial (73%), HNSCC (73%), bladder (70%) and prostate (83%) cancer samples. Biomarker searches for genetic alterations explaining responders/non-responders are presently on-going. In summary, the dual mechanism of action of the mitotic MTH1 inhibitor OXC-101 explains its strong anti-cancer effect. Citation Format: Ulrika Warpman Berglund, Helge Gad, Kumar Sanjiv, Ann-Sofie Jemth, Oliver Mortusewics, Lars Brautigam, Juha Rantala, Thomas Helleday. OXC-101 kills cancer by disturbing microtubule polymerization and inhibiting MTH1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1569.