A recent study presented at ENDO 2025, the annual meeting of the Endocrine Society in San Francisco, has highlighted potential benefits of the anti-obesity medication tirzepatide, marketed as Mounjaro for diabetes and Zepbound for obesity. Researchers found that this medication may reduce the growth of obesity-associated breast cancer in a mouse model, a development that could have implications for future treatments.
The study’s lead author, Amanda Kucinskas, a Ph.D. candidate at the University of Michigan, noted that obesity is a significant risk factor for breast cancer. Existing literature indicates that individuals with obesity often experience worse outcomes in breast cancer compared to those without obesity, and that weight loss can lead to improved outcomes. However, traditional weight loss methods present various challenges.
In the study, 16 C57BL/6 mice were subjected to a high-fat diet to induce obesity. At 32 weeks of age, they were administered either tirzepatide or a placebo for 16 weeks. The findings showed that mice receiving tirzepatide experienced a body weight and fat reduction of approximately 20%, similar to what has been observed in women using the medication. Notably, the researchers reported a significant decrease in tumor volume in the tirzepatide group compared to controls, with tumor size correlating with body weight and adipose mass.
Kucinskas emphasized that while these results are preliminary, they suggest that tirzepatide could positively influence breast cancer outcomes. Further studies are planned in collaboration with the University of North Carolina at Chapel Hill to differentiate the effects of weight loss from the specific impacts of tirzepatide on tumor growth.