Christian Sirrenberg

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.

Abstract 4183: A novel selective DNA-PK inhibitor, M3814, as a potential combination partner of Etoposide and Cisplatin in the therapy of lung cancer

M3814 is a potent and selective inhibitor of DNA-PK, one of the key cellular regulators of DNA damage induced by ionizing radiation or certain cytostatics used in the treatment malignant disease. One of these drugs, Etoposide, induces double strand breaks (DSB) in cellular DNA. DSBs are most difficult to repair and, if left unrepaired, can lead to induction of cell cycle arrest and/or apoptosis and ultimately cell death. DNA-PK plays a critical role in the repair of DSB via the non-homologous end-joining pathway. M3814 was tested for activity in combination with Etoposide in a panel of 98 cancer cell lines derived from lung cancer. A broad potentiation effect of DNA-PK inhibitor was observed in most cancer cell lines. As a rule, cell lines sensitive to Etoposide demonstrated increased sensitivity to the combination. M3814 did not show significant effect on cancer cell growth/viability in combination with Cisplatin compared to Cisplatin alone at concentrations that effectively inhibit DNA-PK activity. At the same time, M3814 did not negatively affect the antitumor activity of Cisplatin. The therapeutic effect of M3814 in combination with the standard of care (SoC) regimen of Etoposide and Cisplatin was tested in the human small cell lung cancer xenograft model, NCI-H520. Triple combination of M3814, Etoposide and Cisplatin resulted in increased efficacy compared to SoC treatment arm. Since myeloid and lymphoid suppression is one of the dose limiting toxicities of the SoC regimen in patients, the effect of the triple combination on myeloid and lymphoid blood cells was investigated in immunocompetent mice. Whereas the SoC treatment showed reduction of the myeloid and lymphoid compartments, the addition of M3814 did not additionally reduce these cells neither in the treatment nor the recovery phase. Our results warrant further investigations to explore the potential of the combination in the clinical setting. Citation Format: Christian Sirrenberg, Astrid Zimmermann, Thomas Grombacher, Lyubomir T. Vassilev, Lars Damstrup, Frank T. Zenke, Andree Blaukat. A novel selective DNA-PK inhibitor, M3814, as a potential combination partner of Etoposide and Cisplatin in the therapy of lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4183. doi:10.1158/1538-7445.AM2017-4183