Pfizer reports experimental breast cancer drug reduces risk of disease worsening in mid-stage trial

Pfizer said its experimental drug atirmociclib plus fulvestrant lowered the risk of disease progression or death by 40% in a mid-stage trial. The company reported a manageable safety profile, with 6.4% of patients stopping treatment due to side effects.

Pfizer announced mid-stage trial results for an experimental oral drug called atirmociclib, tested in combination with the hormone therapy fulvestrant. The company reported a 40% reduction in the risk of disease progression or death for the combination versus the comparator therapies. The study enrolled patients whose breast cancer had spread and who had received prior treatment, including many whose cancer returned soon after CDK4/6 drugs. Pfizer said a larger late-stage study in newly diagnosed metastatic patients is already underway. Study details: - Pfizer reported a 40% reduction in the risk of disease progression or death for atirmociclib plus fulvestrant in the mid-stage trial. - The trial compared the experimental combination to fulvestrant or to everolimus plus exemestane, a commonly used regimen for postmenopausal patients with this cancer type. - The study enrolled patients whose cancer returned soon after treatment with widely used CDK4/6 drugs, a group described by the company as harder to treat. - More than 90% of patients began atirmociclib within three months of stopping their previous cancer medicine, according to Pfizer. - Pfizer reported a manageable safety profile and said 6.4% of patients stopped treatment because of side effects. - Overall survival data were described as early and not ready for conclusions at this stage. Summary: Pfizer described the mid-stage results as supporting plans to test atirmociclib in first-line and earlier stages of breast cancer where longer disease control might be relevant. A large late-stage study in newly diagnosed metastatic patients is already underway, and overall survival outcomes remain undetermined at this time.