A new study suggests that blockbuster drugs like Ozempic may lower patients’ risk of developing certain types of cancer that are strongly linked to obesity.

Patients with Type 2 diabetes who were prescribed drugs known as glucagon-like peptide-1, or GLP-1, developed fewer obesity-related cancers than patients who were treated with insulin, according to a study published Friday in JAMA Network Open. However, these newer drugs did not perform better than metformin, an older diabetes drug known to reduce cancer risk.

The study focused on a group of drugs that includes Novo Nordisk A/S’s Ozempic, a diabetes treatment. Since the study concluded, two similar drugs were approved for weight loss: Novo’s Wegovy and Eli Lilly & Co.’s Mounjaro.

Novo’s American depositary receipts rose 2.2% at 11:40 a.m. in New York on Friday. Eli Lilly’s shares gained 1.6%.

The study was based on electronic health records of over 1.6 million patients with Type 2 diabetes for 15 years ending in November 2018. As Ozempic was only introduced in the U.S. less than a year before the study ended, most of the GLP-1 patients were likely taking first-generation medications like Novo’s Victoza, according to Lindsey Wang, a rising second-year student in the BS-MD program at Case Western Reserve University, who conducted the data analysis.

Despite this, the study adds to the growing evidence that widely popular diabetes and weight-loss shots could play a role in cancer prevention. However, more research, including randomized trials comparing GLP-1 drugs to other treatments, is needed to confirm whether these drugs can truly prevent certain types of cancer.

“Obesity is the tobacco of our age when it comes to cancer risk,” said Arif Kamal, chief patient officer of the American Cancer Society. Kamal considers the early evidence on GLP-1s “compelling.”

These drugs have been used for nearly two decades, but the newer, more potent versions have significantly expanded the market. With millions of people now taking them, scientists are uncovering new potential uses and some surprising side effects. These drugs have triggered a gold rush for Big Pharma, with analysts at Goldman Sachs estimating the market for obesity alone could reach $130 billion by the end of the decade.

Cancer links

Excess body fat is known to increase the risk of developing 13 specific types of cancer, representing 40% of all cancer diagnoses in the U.S., according to the Centers for Disease Control and Prevention.

In the JAMA study, patients prescribed GLP-1s were nearly 50% less likely to develop colon cancer than those treated with insulin alone. GLP-1s were also associated with a lower risk of developing other tumors in the digestive system, including esophageal cancer, gallbladder cancer, and pancreatic cancer.

“This is very significant because usually when you get these cancers, you have a poor prognosis,” said Wang. She conducted the research under the guidance of Case Western Professor Nathan Berger, who passed away last month at the age of 83.

In a surprising finding, Wang noted that the drugs did not appear to reduce the risk of post-menopausal breast cancer. There was also no impact on thyroid cancer. Patients who took GLP-1s were more likely to develop kidney cancer than those who took metformin.

However, tracking these associations through electronic health records is “very problematic,” said Anne McTiernan, a professor of epidemiology at the Fred Hutch Cancer Center, who was not part of the research team but reviewed the study results.

“Electronic health records do not accurately portray other health conditions beyond the condition for which billing is done,” she said in an email, noting that the dataset in the study didn’t accurately reflect alcohol use and might have underestimated the number of overweight patients in the study with a family history of colon polyps. 

Furthermore, U.S. drug labels for both Ozempic and Wegovy carry a warning about thyroid tumors in rodents, stating that it is unclear whether these drugs cause such tumors in humans.

The European Medicines Agency investigated this issue last year after independent researchers pointed to the potential of an increased risk of thyroid cancers when people with Type 2 diabetes use these medications. However, they found no evidence to support a causal association. Other research groups have reached similar conclusions.