Borussertib is primarily used in cancer research and drug development due to its potent inhibition of the DNA-dependent protein kinase (DNA-PK). This enzyme plays a critical role in the repair of DNA double-strand breaks, particularly through the non-homologous end joining (NHEJ) pathway. By blocking DNA-PK, Borussertib impairs the ability of cancer cells to repair radiation- or chemotherapy-induced DNA damage, thereby enhancing the effectiveness of these treatments. It is being investigated as a radiosensitizer and chemosensitizer in various solid tumors and hematologic malignancies. Its application is especially promising in cancers that rely heavily on the NHEJ pathway for DNA repair, making them more vulnerable when this pathway is inhibited. Borussertib has shown synergistic effects when combined with ionizing radiation or DNA-damaging agents like cisplatin or topoisomerase inhibitors. Due to its targeted mechanism, Borussertib supports the development of precision oncology therapies, aiming to increase tumor cell death while minimizing damage to healthy tissues. It remains under preclinical and clinical evaluation to determine optimal dosing, safety, and efficacy in combination regimens.