A new study has found that an anti-obesity drug called tirzepatide, which is sold under the names Mounjaro for diabetes and Zepbound for obesity, may help slow down the growth of breast cancer linked to obesity.
The research was presented at ENDO 2025, the annual meeting of the Endocrine Society held in San Francisco, California.
Obesity is known to increase the risk of developing breast cancer. Women with obesity often face worse outcomes after being diagnosed with breast cancer compared to those with a healthy weight.
While losing weight can help improve health and reduce cancer risks, many people find it difficult to lose weight using traditional methods like dieting and exercise alone.
Tirzepatide is part of a new generation of weight loss drugs that work by targeting two hormones in the body: GLP-1 and GIP. These hormones help control blood sugar and reduce appetite. In this study, researchers wanted to find out if using tirzepatide could not only help with weight loss but also reduce the growth of breast cancer caused by obesity.
The study was conducted using 16 female mice. These mice were fed a high-fat diet that made up 40% of their food and were kept in a warm environment to help them gain weight. By the time the mice were 32 weeks old, they had become obese.
Then, they were divided into two groups. One group received injections of tirzepatide every other day for 16 weeks, while the other group received a placebo. The researchers measured the size of the tumors in the mice twice a week.
By the end of the study, the researchers found that the mice treated with tirzepatide lost about 20% of their body weight and body fat. This amount of weight loss is similar to what women have experienced in human trials of the drug. Most of the weight loss came from a reduction in fat tissue.
Importantly, the drug also led to smaller tumor sizes in the mice that received it, compared to those in the placebo group. The researchers found a strong link between the amount of weight and fat the mice had and the size of their tumors. This suggests that lowering body fat may help slow the growth of breast cancer.
Amanda Kucinskas, the lead researcher and a Ph.D. student at the University of Michigan, said that while this is early data, the results are encouraging. She noted that new anti-obesity drugs like tirzepatide might help reduce the risk of breast cancer or improve outcomes for people with obesity-related breast cancer.
Further studies are being done in collaboration with Dr. Steve Hursting’s lab at the University of North Carolina at Chapel Hill. These studies aim to understand whether the effects on tumors are directly caused by the drug or just a result of the weight loss.
In summary, this study offers hope that weight loss medications might one day play a role in fighting breast cancer, especially in people with obesity. However, more research is needed before this approach can be recommended for humans.
If you care about breast cancer, please read studies about how eating patterns help ward off breast cancer, and soy and plant compounds may prevent breast cancer recurrence.
For more health information, please see recent studies about how your grocery list can help guard against cancer, and a simple way to fight aging and cancer.
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