A Common Blood Pressure Pill Supercharges a Cancer Drug, Dartmouth Scientists Find

A medication taken by millions of people to control high blood pressure could make an important class of cancer drugs far more powerful, according to new research from the Dartmouth Cancer Center. Scientists found that telmisartan, a widely used and inexpensive blood-pressure pill, dramatically boosted the cancer-killing activity of the targeted therapy olaparib in laboratory experiments.

Olaparib belongs to a group of drugs known as PARP inhibitors, which work by exploiting weaknesses in how certain cancer cells repair damaged DNA. Tumors with defects in their DNA-repair machinery — such as those driven by faulty BRCA genes — are especially vulnerable to these drugs, because blocking the PARP repair pathway leaves the cancer cells unable to fix the genetic damage that eventually kills them.

The Dartmouth team discovered that adding telmisartan changed the equation in two important ways. In preclinical experiments, combining the blood-pressure drug with olaparib increased the amount of DNA damage building up inside cancer cells. At the same time, it activated key immune defenses, boosting the production of type I interferons — signaling molecules that help the immune system recognize and attack tumors. In effect, the combination hit the cancer directly while also recruiting the body's own defenses to finish the job.

Perhaps the most striking result was that telmisartan appeared to make tumors more sensitive to PARP inhibitors even when they lacked the DNA-repair weaknesses that the drugs normally rely on. That raises the tantalizing possibility of extending the benefits of olaparib beyond the relatively narrow group of patients whose cancers carry BRCA-type mutations. When the researchers compared telmisartan with other drugs in the same blood-pressure class, known as angiotensin receptor blockers, they found that its cancer-enhancing effects were unique — suggesting the benefit is not simply a general property of the drug family.

The findings were published in The Journal for ImmunoTherapy of Cancer. Because the work so far has been carried out in laboratory and preclinical models rather than in human clinical trials, doctors caution that patients should not change their medications on the basis of the study, and that carefully designed trials will be needed to confirm whether the combination is safe and effective in people.

Still, the appeal of repurposing an existing, low-cost and well-understood drug is considerable. If the results hold up, pairing a decades-old blood-pressure pill with a modern targeted therapy could offer a relatively fast and affordable way to make cancer treatment more effective for a broader range of patients.