Researchers at Dartmouth Cancer Center reported on Mar. 25 that the blood pressure medication telmisartan can significantly improve the effectiveness of the targeted cancer therapy olaparib, according to findings published in The Journal for ImmunoTherapy of Cancer.
The study could impact treatment options for many patients with cancer, especially those whose tumors do not respond to current therapies. Olaparib and other PARP inhibitors are most effective against cancers with certain DNA repair defects, but these defects are absent in many tumors, limiting who can benefit from such drugs. Resistance to PARP inhibitors is also a common problem.
Lead researcher Tyler J. Curiel said his team found that telmisartan made tumor cells more sensitive to PARP inhibitors even when they lacked the usual DNA repair issues required for these drugs to work. In preclinical studies, combining telmisartan with olaparib increased DNA damage within tumor cells and activated immune responses by boosting type I interferons—molecules that help the immune system recognize and attack cancer. "This immune activation appears to be a key reason the combination works so well," Curiel said.
Telmisartan is part of a class of medications known as angiotensin II receptor blockers (ARBs), which are typically used for hypertension. According to Curiel's team, among all ARBs tested in their research, only telmisartan had this unique effect on enhancing cancer treatment outcomes. The drug also lowered levels of PD-L1 inside tumor cells—a protein that helps cancers evade detection by the immune system—further increasing its potential as an adjunct therapy.
"Telmisartan has several distinct anticancer effects that, together with targeted therapy, could make tumors more responsive to distinct types of treatments," Curiel said. He added that data also suggest telmisartan may improve outcomes when combined with other chemotherapy classes and immunotherapies across various cancers.
Curiel noted that because telmisartan is safe and well-tolerated—even by people without high blood pressure—it is suitable for clinical use alongside existing treatments. Two clinical trials at Dartmouth Cancer Center are now underway: one in men with metastatic castration-resistant prostate cancer and another in platinum-resistant ovarian cancer. "We are encouraged by what we are seeing so far," Curiel said.
