Abstract 1658: M3814, a novel investigational DNA-PK inhibitor: enhancing the effect of fractionated radiotherapy leading to complete regression of tumors in mice

Physical or chemical agents that damage DNA such as ionizing radiation are among the most widely used classes of cancer therapeutics today. Double strand breaks (DSB) generated in DNA by radiation induce multitude of cellular responses, including DNA repair, cell cycle arrest or cell death if the damage is left unrepaired. A complex set of molecular events are responsible for DNA repair via two major mechanisms - homologous recombination (HR) or non-homologous end joining (NHEJ). DNA-PKcs with its regulatory protein subunits, Ku70 and Ku80, is an integral component of NHEJ and considered an attractive intervention point to inhibit DNA repair. We have developed an orally bioavailable, highly potent, and selective inhibitor of DNA-PK, M3814, for cancer therapy in combination with DNA damaging modalities such as radiation, and radio-chemotherapy. Here, we present the preclinical characterization of M3814 using biochemical, cellular and human tumor xenograft models. M3814 sensitized multiple tumor cell lines to radiation therapy in vitro and strongly enhanced the antitumor activity of ionizing radiation in vivo with complete tumor regression applying a clinically relevant fractionated radiation regimen. These effects are due to inhibition of DNA-PK protein kinase activity as demonstrated by the levels of DNA-PK autophosphorylation in human tumor cell lines, and xenograft tumors M3814 is currently investigated in PhI clinical trials. Citation Format: Frank T. Zenke, Astrid Zimmermann, Christian Sirrenberg, Heike Dahmen, Lubo Vassilev, Ulrich Pehl, Thomas Fuchss, Andree Blaukat. M3814, a novel investigational DNA-PK inhibitor: enhancing the effect of fractionated radiotherapy leading to complete regression of tumors in mice. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1658.