Abstract 6217: Inhibiting ataxia-telangiectasia mutated and RAD3-related (ATR) by BAY 1895344 overcomes chemoresistance to oxaliplatin and promotes synergistic anti-tumor effect in pancreatic cancer

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Abstract Pancreatic Ductal Adenocarcinoma (PDAC) is a highly aggressive disease with a poor prognosis and a limited response to most of the treatments. Despite a platinum-based drug such as oxaliplatin or cisplatin is one of the most effective chemotherapy drugs for PDAC, resistance to it is a major limiting factor in PDAC treatment, indicating an urgent need for new approaches. Recently, targeting major DNA damage response (DDR) regulators such as ATM (Ataxia-telangiectasia mutated) or ATR (Ataxia telangiectasia mutated and Rad3-related) kinase has shown therapeutic potential in cancer treatment. This shows that it may be possible to enhance the responsiveness of platinum medicines via a DDR inhibition strategy. The most recently developed ATR inhibitor with the greatest potency, BAY 1895344, showed an anti-proliferative effect in clinical trials. Here, we aimed to evaluate the effect of ATR inhibition using BAY 1895344 on responsiveness to oxaliplatin in pancreatic cancer, for the first time. CFPAC-1 and Capan-2 are selected among six kinds of pancreatic cancer cell lines as oxaliplatin-sensitive and -resistant cells, respectively. According to BRAID analysis, combining the BAY 1895344 and oxaliplatin resulted in strong synergistic effects in both cell lines, particularly in Capan-2. The synergism is also confirmed in all four organoids derived from PDAC patients. We found that p-Chk1, coordinating DDR and cell cycle checkpoint, was considerably suppressed by the combined treatments, which was associated with elevated γ-H2AX intensity, cell cycle arrest and apoptosis. Moreover, we investigated the in vivo synergistic anti-tumor efficacy of combination therapy using a tumor-bearing nude mice model with CFPAC-1 and Capan-2 cells, demonstrating a substantial reduction of tumor growth in combination therapy when compared to single treatment. In conclusion, ATR inhibition enhanced the anticancer effect of oxaliplatin, and this combined therapeutic strategy may be effective in overcoming chemo-resistance in PDAC. (This study is supported by National Cancer Center, Republic of Korea (No. 2212470, 2010330)) Citation Format: Hye Won Shon, Jung Won Chun, Jeong Eun Gong, Mi Rim Lee, Yu-Sun Lee, Sumin Kang, Sunshin Kim, Sang Myung Woo, In Rae Cho, Woo Hyun Paik, Woo Jin Lee, Ji Kon Ryu, Yong-Tae Kim, Sang Hyub Lee, Yun-Hee Kim. Inhibiting ataxia-telangiectasia mutated and RAD3-related (ATR) by BAY 1895344 overcomes chemoresistance to oxaliplatin and promotes synergistic anti-tumor effect in pancreatic cancer [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 6217.

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