DNA 损伤反应 (DDR) 是通过协调 DNA 修复和凋亡途径来调节基因组稳定性和细胞周期检查点激活的主要机制。共济失调毛细血管扩张和 Rad3 相关蛋白 (ATR) 在 DDR 中发挥着重要作用，因为它能够检测广泛的 DNA 损伤。因此，靶向DDR，特别是ATR，是癌症治疗中一种有前途的治疗策略。此外，ATR 的抑制使癌细胞对放射治疗 (RT) 敏感。在此，我们首次在体外研究了 Elimusertib (BAY-1895344) 作为一种高效选择性 ATR 抑制剂与 RT 组合在三阴性乳腺癌 (TNBC) 中的协同作用。MDA-MB-231 TNBC 细胞首先用不同浓度的 Elimusertib 处理 24 h，然后接受 4 和 8 Gy 的 X 射线照射。照射后72小时后，进行WST-1、Annexin V、细胞周期、吖啶橙/碘化丙啶、线粒体染色和蛋白质印迹分析。我们的研究结果表明，4 Gy照射和较低剂量（尤其是2和4 nM） Elimusertib 组合在辐射后 72 小时通过凋亡细胞死亡、明显的核和线粒体损伤以及抑制基于 ATR-Chk1 的 DDR 机制发挥了相当大的抗癌活性。 Elimusertib 与 RT 组合的 ATR 抑制可能是一种有前途的新治疗策略在 TNBC 的治疗中。然而，应该进行进一步的实验来阐明这种联合治疗的治疗功效的潜在分子机制及其与 TNBC 体外和体内 DNS 修复机制的关联。

DNA damage response (DDR) is the principal mechanism regulating genomic stability and cell cycle checkpoint activation by coordinating DNA repair and apoptotic pathways. Ataxia telangiectasia and Rad3-related protein (ATR) play a significant role in the DDR due to its capability to detect a wide spectrum of DNA damage. Therefore, targeting DDR, specifically ATR, is a promising therapeutic strategy in cancer treatment. Furthermore, the inhibition of ATR sensitizes cancer cells to radiotherapy (RT). Herein, we, for the first time, investigated the synergistic effects of Elimusertib (BAY-1895344) as a highly potent selective ATR inhibitor with RT combination in triple-negative breast cancer (TNBC), in vitro.MDA-MB-231 TNBC cells were firstly treated with different concentrations of Elimusertib for 24 h and then exposed to 4 and 8 Gy of X-ray irradiation. After post-irradiation for 72 h, WST-1, Annexin V, cell cycle, acridine orange/propidium iodide, mitochondria staining and western blot analysis were conducted.Our findings showed that 4 Gy irradiation and lower doses (especially 2 and 4 nM) of Elimusertib combination exerted a considerable anticancer activity at 72 h post-irradiation through apoptotic cell death, marked nuclear and mitochondrial damages and the suppression of ATR-Chk1 based DDR mechanism.ATR inhibition by Elimusertib in combination with RT may be a promising new treatment strategy in the treatment of TNBC. However, further experiments should be performed to elucidate the underlying molecular mechanisms of the therapeutic efficacy of this combination treatment and its association with DNS repair mechanisms in TNBC, in vitro and in vivo.