An experimental drug designed to fight cancer produced an unexpected result in a new study, leaving researchers looking far beyond its original purpose.
Scientists at the University of East Anglia found that the compound not only strengthened bones in postmenopausal mice but also appeared to reduce body fat despite no changes in food intake.
Researchers initially developed drug CADD522 as a potential cancer treatment, designed to block a protein that helps tumors grow and spread. The findings, published in the journal npj Drug Discovery, come as millions of women navigate hormonal changes that can weaken bones and make maintaining a healthy weight more difficult.
“The lack of body fat accumulation was the most surprising,” lead researcher Darrell Green from UEA’s Norwich Medical School told Newsweek. “We already had an inkling that CADD522 would benefit bone health, so we somewhat expected those findings, but the fat results were completely unexpected.”
Green said the discovery could be important because menopause-related weight gain is common and can increase the risk of metabolic conditions, including diabetes
How the Experiment Unfolded
After eight weeks of treatment, scans showed that mice receiving CADD522 had stronger, healthier bones than untreated animals.
The drug increased bone volume and helped preserve the fine, honeycomb-like internal structure that gives bones their strength.
Blood tests suggested the compound encouraged the formation of new bone while allowing the body’s normal cycle of bone breakdown and rebuilding to continue.
The researchers found that the mice receiving CADD522 weighed less than untreated animals despite eating the same amount of food.
The treated animals also carried less body fat and accumulated fewer fat deposits inside their bone marrow, a process commonly seen after menopause and one that has been linked to declining bone health.
The researchers then examined the animals’ brain tissue and found further potentially important effects.
Menopause-related disruptions in fat metabolism appeared to improve, with levels of beneficial omega-3 fatty acids, including DHA, remaining largely intact. Other lipid imbalances also shifted toward healthier patterns.
Green said the study’s findings on fat metabolism may have implications beyond weight management.
“Perhaps even more surprising, some of our other projects are showing that fat changes in the brain, which we also observed in our study, can lead to cognitive decline, leading to dementia,” he said. “It’s important that we learn the basics of these natural processes so we can step in with new medicines and preserve lifelong health.”
While the results are promising, the researchers caution that the treatment remains in the early stages of development. So far, it has been tested only on animals.
However, safety studies in mice, rats and dogs found the drug was well tolerated and could be taken orally.
Researchers also found that CADD522 appears to be broken down more slowly in human tissue than in rodents, potentially improving its effectiveness in people.
If the treatment eventually proves effective in humans, Green believes it could potentially help a broad range of women, such as those already living with osteoporosis, women approaching menopause or those hoping to prevent bone loss before it starts.
“We must be careful and recognize that we only investigated the postmenopausal state and after bone loss had already set in; so for sure, CADD522 would be best placed in this scenario,” Green said. “A preventative medicine would be even better, but we would need to test this next.”
Reference
Ersek, A., Kim, M.S., Suelzu, C. et al. (2026). RUNX2 inhibitor CADD522 improves bone microarchitecture and lipid metabolism in postmenopausal bone loss. npj Drug Discovery, 3. https://doi.org/10.1038/s44386-026-00076-z
Contact Newsweek editors on this story: Kara Dolman and Shakeema Edwards.