A study presented at the ENDO 2025 meeting revealed that tirzepatide, an anti-obesity medication commonly known as Mounjaro for diabetes and Zepbound for obesity, can reduce obesity-associated breast cancer growth in mice. Conducted by Amanda Kucinskas and colleagues at the University of Michigan, the research highlights obesity as a significant breast cancer risk factor. Existing studies indicate worse outcomes for obese breast cancer patients, with weight loss potentially improving these outcomes. Traditional weight loss methods, however, pose numerous challenges.

The study utilized 16 C57BL/6 mice, fed a high-fat diet to induce obesity. At 32 weeks, these mice were treated with tirzepatide or a placebo for 16 weeks. Results showed a 20% reduction in body weight and fat, attributed to decreased adipose mass. Additionally, tumor volume was significantly reduced in the tirzepatide group compared to controls, with tumor size correlating with body weight and adipose mass.

These preliminary findings suggest tirzepatide might not only aid weight loss but also improve breast cancer outcomes for obese patients. Further studies, in collaboration with Dr. Steve Hursting’s lab, aim to distinguish weight loss from direct tumor-specific effects of tirzepatide.

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[Source: ScienceDaily, July 15, 2025]

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