Tirzepatide Shows Promise in Reducing Breast Cancer Growth Linked to Obesity in Mouse Study

A recent investigation presented at the Endocrine Society's annual meeting, ENDO 2025, in San Francisco, has revealed that tirzepatide, an anti-obesity medication, may slow the growth of breast cancer associated with obesity in a mouse model.

Obesity is recognized as a significant risk factor for developing breast cancer, and existing evidence indicates that individuals with obesity have poorer outcomes compared to those of normal weight. Moreover, weight loss has been correlated with improved prognoses. Traditional weight loss methods, however, often pose various challenges.

The study's lead researcher, Amanda Kucinskas, a Ph.D. candidate at the University of Michigan, along with her colleagues, utilized tirzepatide, a medication that targets GLP-1 (glucagon-like peptide 1) and GIP (glucose-dependent insulinotropic polypeptide) receptors. The objective was to assess whether tirzepatide could inhibit the progression of obesity-related breast cancer.

The experimental setup involved 16 C57BL/6 mice, which were placed on a high-fat diet comprising 40% fat and kept in a warm environment to induce obesity. At 32 weeks of age, the mice were divided into two groups, receiving either tirzepatide or a placebo through injections administered every other day for a duration of 16 weeks. Tumor sizes were monitored bi-weekly throughout the study.

The findings indicated that tirzepatide led to a reduction in both body weight and fat levels by approximately 20%, mirroring the weight loss often observed in human patients using this medication. The weight reduction was chiefly attributed to decreased adipose tissue, demonstrated by lower adipose depot weights in treated mice compared to the control group.

Moreover, tumors in the mice receiving tirzepatide exhibited smaller volumes relative to those receiving the placebo. At the conclusion of the study, a significant correlation was observed between tumor volume and metrics such as body weight, total adipose mass, and hepatic fat storage.

While these results are still in the preliminary phase, they suggest the potential for tirzepatide to positively influence breast cancer outcomes related to obesity. Ongoing research will further explore the effects of tirzepatide, aiming to delineate the specific impact of weight loss from the drug's direct effects on tumor growth.