Abstract 321: Synergistic activity of the ATR inhibitor BAY 1895344 in combination with DNA damage inducing and DNA repair compromising therapies in preclinical tumor models

Abstract The DNA damage response (DDR) system consists of complex signalling pathways that secure the integrity of the genome in eukaryotic cells. DDR pathway activation follows recognition of DNA damage and results in cell cycle arrest, suppression of general translation, induction of DNA repair, cell survival or even cell death. Proteins that directly recognize aberrant DNA structures recruit and activate kinases of the DDR, such as ATR (ataxia telangiectasia and Rad3-related). ATR responds to a broad spectrum of DNA damages, including double-strand breaks (DSB) and lesions derived from interference with DNA replication as well as increased replication stress. Therefore, inhibition of ATR kinase activity could be the basis for a novel anti-cancer therapy in tumors with increased DNA damage, deficiency in DDR or replication stress. The potential of combining ATR kinase inhibitor with DNA damage inducing or DNA repair compromising anti-cancer therapeutics was studied in preclinical tumor models. We assessed the novel ATR kinase inhibitor (ATRi) BAY 1895344 in combination with external beam radiation therapy (EBRT), poly ADP ribose polymerase (PARP) inhibition or anti-androgen (AA) therapy. In cellular anti-proliferation assays as well as in tumor xenograft studies we could demonstrate synergistic activity of BAY 1895344 in combination treatment with the PARP inhibitor AZD-2281 in the homologous recombination (HR) defective breast cancer model MDA-MB-436, and with the non-steroidal AA darolutamide in the hormone-dependent prostate cancer model LAPC-4. Strong synergistic anti-tumor activity of BAY 1895344 could be further demonstrated in combination with EBRT inducing long-lasting tumor growth inhibition in the colorectal cancer xenograft model LOVO. The mechanism-based potential of combining DNA damage induction by EBRT with ATRi BAY 1895344 suggests a potential new treatment option for radiation therapy-resistant patients. Furthermore, the inhibition of parallel DDR pathways, as a combination of ATRi BAY 1895344 with a PARP inhibitor, indicates novel treatment opportunities in breast cancer patients with homologous recombination deficiencies, as does the synergism of BAY 1895344 and AA darolutamide therapy in hormone-dependent prostate cancer patients. BAY 1895344 is currently under clinical investigation in patients with advanced solid tumors and lymphomas (NCT03188965). Citation Format: Antje Margret Wengner, Gerhard Siemeister, Ulrich Luecking, Julien Lefranc, Kirstin Meyer, Eleni Lagkadinou, Bernard Haendler, Pascale Lejeune, Dominik Mumberg. Synergistic activity of the ATR inhibitor BAY 1895344 in combination with DNA damage inducing and DNA repair compromising therapies in preclinical tumor 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 321.