Breast cancer: Pfizer said that an experimental breast cancer drug combination cut the risk of disease progression or death by 40% in a mid-stage clinical trial, offering a possible boost to its oncology pipeline. The company said the results support further testing of the treatment in earlier lines of care, including newly diagnosed and early-stage breast cancer.
The treatment combines atirmociclib, Pfizer’s investigational oral CDK4 inhibitor, with fulvestrant, a hormone therapy. It was studied in patients with hormone receptor-positive, HER2-negative metastatic breast cancer whose disease had already spread and who had received prior treatment.
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According to Pfizer, the study focused on a particularly difficult-to-treat group: patients whose cancer had returned soon after treatment with commonly used CDK4/6 inhibitors. The company reported that more than 90% of those enrolled had started atimociclib within three months of discontinuing their prior cancer medication.
The trial compared atirmociclib plus fulvestrant against currently used treatment options, including fulvestrant alone or everolimus combined with exemestane. Pfizer reported that the drug combination had a manageable safety profile, with 6.4% of patients discontinuing treatment due to adverse effects.
The company said overall survival data are still immature, meaning it is too early to draw conclusions on that measure. Even so, Pfizer said the findings strengthen its case for moving the drug into larger and earlier-stage studies. A late-stage trial in newly diagnosed metastatic breast cancer is already underway.
Atirmociclib is designed to target CDK4, a protein involved in cell-cycle control that can help drive tumour growth. Pfizer is positioning the drug as a next-generation candidate in breast cancer treatment, especially for patients who need better disease control after earlier therapies stop working.