In a recent press release, Pfizer shared positive findings from the Phase 2 FOURLIGHT-1 clinical trial of atirmociclib as a second-line treatment for metastatic breast cancer.
Atirmociclib is a next-generation therapy that inhibits cyclin-dependent kinase 4 (CDK4), a molecule that drives cell division. Pfizer is currently investigating the drug in patients with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer.
The investigators evaluated atirmociclib and fulvestrant versus fulvestrant or everolimus plus exemestane. The trial enrolled 264 individuals across 14 countries with advanced or metastatic breast cancer who experienced disease progression after CDK 4/6 inhibitor therapy. Over 90% of individuals who began atirmociclib did so within three months of receiving a CDK 4/6 inhibitor.
Participants in the treatment group experienced a 40% lower risk of death or disease progression. Moreover, progression-free survival did not differ by menopausal status, length or type of prior CDK 4/6 inhibitor treatment, spread to other organs or patient’s functional status.
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Throughout the trial, 6.4% of participants discontinued treatment due to side effects. The overall safety profile of the drug was consistent with that of previous studies, though.
“These results are especially encouraging given that the FOURLIGHT‑1 study enrolled patients whose disease had progressed soon after prior CDK4/6 inhibitor therapy, a difficult-to-treat population,” said Jeff Legos, chief oncology officer at Pfizer. “We are continuing to accelerate development of this next-generation cell cycle inhibitor in earlier lines of therapy where it may offer even greater benefit for patients.”
Pfizer plans to share more detailed trial information at an upcoming medical conferences. In addition, a Phase 3 trial of atirmociclib as a first-line therapy in metastatic breast cancer is currently underway.
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