When Tyler Curiel started prescribing a blood pressure pill to his cancer patients, he wasn't trying to lower their blood pressure at all.
Curiel, a physician-researcher at Dartmouth Cancer Center in Lebanon, New Hampshire, has spent years looking for ways to make cancer treatments work better. His latest finding, published in The Journal for ImmunoTherapy of Cancer, suggests that an old, inexpensive blood pressure medication could dramatically boost the power of a widely used cancer drug called olaparib.
Olaparib belongs to a class of targeted therapies called PARP inhibitors. These drugs exploit weaknesses in how certain cancer cells repair their DNA. They work well against tumors with specific genetic defects, like those linked to BRCA mutations. But many patients don't have those defects, and even when the drugs initially work, tumors often become resistant over time.
That's where telmisartan comes in.
Telmisartan is part of a family of blood pressure drugs called ARBs (angiotensin II receptor blockers). It's been approved by the FDA for years, costs very little, and is taken as a simple pill. Curiel's team discovered that this drug does something unexpected: it makes tumors more sensitive to PARP inhibitors, even tumors that lack the DNA repair weaknesses these drugs usually need.
In lab experiments, combining telmisartan with olaparib did two important things. First, it increased DNA damage inside cancer cells. Second, it triggered a powerful immune response by boosting production of type I interferons—signaling molecules that help the immune system recognize and attack tumors. The drug also lowered levels of PD-L1, a protein that many cancers use to hide from the immune system.
"Telmisartan has several distinct anticancer effects that, together with targeted therapy, could make tumors more responsive to distinct types of treatments," Curiel said.
What makes this especially promising is that telmisartan's cancer-boosting effects appear unique among blood pressure medications in its class. Researchers compared it with other ARBs and found the effect didn't carry over. Only telmisartan had the right combination of properties to enhance cancer treatment.
Because the drug is already widely used, has a strong safety record, and is taken by mouth, Curiel's team was able to move quickly into human trials. They've already launched two clinical studies. The first is testing telmisartan with olaparib in men with advanced prostate cancer. According to Curiel, the very first patient enrolled experienced what he called an exceptional response to treatment. A second trial recently opened for women with ovarian cancer that has become resistant to standard chemotherapy.
"We are encouraged by what we are seeing so far," Curiel said. His goal is to see whether this combination can help more patients benefit from PARP inhibitors and potentially overcome the resistance that often develops over time.
Support from the Guyre Fund and Gmelich Fund at Dartmouth Cancer Center helped make both the research and the clinical trials possible. If the results hold up, a cheap blood pressure pill that doctors have used for decades might one day help thousands more cancer patients benefit from treatments that already exist.