Ulipristal acetate has long been used for emergency contraception and, in some cases, the treatment of fibroids.
But researchers in Manchester, reporting their findings in Nature, wanted to explore another question: could blocking progesterone, one of the hormones that shapes breast development, also influence early biological markers linked to cancer?
According to Healthline, the team enrolled premenopausal women who carried a higher-than-usual risk because several relatives had developed breast cancer.
Each participant took a low daily dose of ulipristal acetate for 12 weeks, starting on the first day of a menstrual cycle.
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Before and after the treatment period, clinicians collected small samples of breast tissue to compare how the cells responded.
Shifts inside the tissue
When the samples were examined in the laboratory, several changes stood out.
Fewer cells were actively dividing, and the activity of a group of cells thought to be involved in aggressive breast cancers dropped noticeably.
Researchers also observed adjustments in the surrounding tissue framework. Collagen fibers appeared less rigidly organized, and the breast tissue itself was slightly softer.
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These details matter because stiffer, denser tissue has been linked to elevated cancer risk.
The study team suggested that by altering how hormone-sensing cells behave, and how much structural protein they produce, the drug may interrupt some of the conditions that allow certain cell populations to grow unchecked.
What specialists make of the findings
Oncologists not involved in the research told Healthline that the results are intriguing but preliminary.
The study was small, short, and designed mainly to test biological response rather than real-world cancer outcomes.
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For now, experts continue to emphasize familiar prevention strategies: regular screenings, healthy body weight, limiting alcohol, not smoking, and discussing family history–related risks with clinicians.
Sources: Healthline.com, Nature
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