A new experimental drug, called CS18, shows promise in helping to overcome a major challenge in cancer treatment—drug resistance. This occurs when cancer cells develop ways to survive and continue growing despite treatment. A study published in Science Advances highlights early evidence that CS18 could be a valuable tool in future cancer therapies. Developed by researchers at Baylor College of Medicine, the drug targets a protein known as TopBP1, which acts like a "biological switchboard" by regulating several pathways that support cancer growth and survival. CS18 was created by modifying a compound known as 3B6. In laboratory tests, it was found to reduce the activity of proteins that promote cancer, such as MYC and mutant p53, which are often involved in uncontrolled cell growth. It also weakened the activity of proteins responsible for DNA repair, which cancer cells rely on to survive treatment. At the same time, CS18 increased the activity of genes that help stop uncontrolled cancer growth. These effects were observed in several types of cancer cells, including triple-negative breast cancer, ovarian cancer, and various lung cancers, as well as acute myeloid leukemia. Importantly, CS18 was less harmful to non-cancerous cells compared to many existing cancer treatments. The researchers tested CS18 in combination with existing cancer drugs, such as PARP inhibitors and osimertinib, which are used to treat certain cancers. When used together, the combination was more effective at killing cancer cells than either treatment alone. This was especially notable in lung cancer cells that had become resistant to osimertinib. Adding CS18 restored the cells' sensitivity to the drug, allowing osimertinib to work more effectively and increase cancer cell death. The study suggests that CS18 could be a valuable addition to combination cancer therapies. By targeting key mechanisms that cancer cells use to resist treatment, CS18 may help prevent the development of resistance or make resistant cancers more responsive to therapy. While more research is needed, these findings offer hope for new strategies in the ongoing fight against cancer.