Do GLP-1 drugs like Ozempic prevent cancer?

SAN DIEGO — Weight loss, type 2 diabetes, sleep apnea, liver disease, heart disease … cancer?

Drugs like Ozempic can help treat a variety of health conditions, but the portrait of their effects in cancer remains blurry. At an April 18 session at the annual American Association for Cancer Research meeting, scientists offered an update on the field and weighed the evidence for any cancer prevention powers.

Bottom line: The jury’s still out.

Several studies have served up tantalizing hints about the drugs’ potential benefits, but other results land all over the map. Scientists have linked the medications, called GLP-1 receptor agonists, to increased survival in cancer patients and a reduction in obesity-related cancers. Other studies, however, have found little or no such association. And some research has raised, if not red flags, perhaps a few yellowish ones. One study noted a potential increased risk of kidney cancer in people taking the drugs. And work in lab animals has sparked concerns about developing thyroid cancer, though more recent research suggests that this isn’t likely in people.

Altogether, the data are kind of messy, said Jennifer Ligibel, an oncologist at Dana-Farber Cancer Institute in Boston. GLP-1 drugs have “really revolutionized weight loss,” she said. “But I think it’s still an open question about their effect on cancer.”

These drugs include semaglutide (sold under the brand names Ozempic, Wegovy and Rybelsus) and tirzepatide (brand names Mounjaro and Zepbound). They mimic gut hormones that play a role in digestion and metabolism, prompting weight loss and acting on the body in a smorgasbord of other ways, some still unknown. As more GLP-1 drugs become available, including the newly approved pill Foundayo, and more people take them over longer periods, researchers may get a clearer picture of whether the medications affect cancer risk.

At this point, though, “you can’t really make any kind of strong conclusions,” said nutrition and cancer researcher Stephen Hursting of the University of North Carolina at Chapel Hill. Science News discussed open questions in the field with Hursting, Ligibel and health data scientist Jiang Bian of the Indiana University School of Medicine in Indianapolis. The conversations have been edited for length and clarity.

SN: Can we say that GLP-1 drugs prevent cancer?

Bian: No. But I do think there are some potential benefits.

Hursting: No. It wouldn’t be surprising, but we need the data to be able to say for sure.

Ligibel: No. Not yet. I’m hopeful.

SN: Why are you hopeful?

Ligibel: The bariatric surgery literature is quite clear that weight loss can lead to a lower risk of developing cancer. You don’t get as much weight loss with GLP-1 receptor agonists as you do with bariatric surgery, on average. But certainly, many patients do achieve very high levels of weight loss. So I think it is very, very promising, but I would not, as an oncologist, consider the data at this point definitive.

SN: Why don’t we have a definitive answer yet?

Bian: These drugs are new, and they’re evolving. A lot of the drugs [may not work the same way for every patient]. And the patient populations among studies are different. We need more data.

Hursting: The newest, most effective drugs aren’t even really included in much of the data. Tirzepatide was only approved for weight loss two and a half years ago, so there just [hasn’t been enough time] to see an effect for a disease like cancer.

SN: How might these drugs work to prevent cancer?

Hursting: There’s a constellation of metabolic changes that occur with obesity. There’s low-level constant inflammation, immune dysfunction, high levels of hormones like insulin and leptin. We know obesity is a major factor in cancer, and these drugs reverse a lot of obesity’s effects.

SN: There has been research that suggests GLP-1 drugs might cause cancer. How worried should patients be?

Ligibel: Those patterns aren’t that consistent. There’s not much preliminary data that makes me worried.

Bian: I’m not currently worried, and I’ve personally been on tirzepatide for weight loss for the last two years.

SN: What would it take to better understand the role these drugs play in cancer?

Bian: Randomized clinical trials are the gold standard. But there are real-world limitations. You can’t do a [randomized clinical trial] on all cancer types, following patients for 20 years. So we’re going to need a combination of different kinds of evidence. Some will be randomized clinical trials, and another piece will be real-world data. [Real-world data come from patients not in clinical trials; it illustrates a medication’s use and efficacy in people’s daily lives.]

Hursting: We need more people asking questions in animal models [lab animals used to study aspects of human disease] so we get a bit more clarity around what cancers are most responsive.

SN: What are the biggest open questions in the field now?

Ligibel: Do these drugs actually reduce the risk of developing cancer? That’s the main one. And could they impact cancer outcomes in people diagnosed with the disease? We have a lot more information toward the first question, and there’s almost nothing toward the second question.

Hursting: We don’t have a great feel for the long-term effects of the newer drugs. I’m also interested in how we get people off the drugs once they’ve lost the weight. [Many people tend to regain weight once they stop using the drugs.]

SN: What do you want people considering taking GLP-1 drugs to know?

Ligibel: Healthy lifestyle is still important. Your diet quality makes a difference. People can lose muscle mass on these drugs. So it’s important that people are still thinking about being healthy.

Hursting: These drugs can be a wonderful tool, but we have to figure out when is best to use them.

They’re not for everyone, and there are going to be individual differences. Some people don’t lose weight.

Bian: There’s not been a definite conclusion that the drugs protect against cancer. [If you’re worried about potential harms,] you should discuss them with your physician.