Pfizer releases new topline phase 2 results for CDK4 inhibitor, Atirmociclib in 2nd line Metastatic Breast Cancer

Pfizer has recently announced new positive topline results from their randomised Phase 2 FOURLIGHT-1 study evaluating atirmociclib in combination with fulvestrant, versus fulvestrant or everolimus plus exemestane, in people with hormone receptor HR-positive, human epidermal growth factor receptor 2-negative advanced or metastatic breast cancer who had received prior cyclin-dependent kinase 4/6 inhibitor-based treatment.

“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, Pfizer. “The strength of these data reinforces our confidence that atirmociclib may meaningfully differentiate from the CDK4/6 inhibitor class, the standard-of-care backbone in HR-positive breast cancer, with the potential for improved efficacy and tolerability. 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.”

Note that in the FOURLIGHT-1, atirmociclib demonstrated manageable safety and was well tolerated, with 6.4 percent of patients discontinuing atirmociclib due to treatment-emergent adverse events. Its safety profile was consistent with prior studies, and no new safety signals were identified. Detailed results will be submitted for presentation at a future medical meeting.

In addition, these findings support their strategy to advance atirmociclib in first-line and early-stage disease, where durable endocrine-based control has the potential to have the greatest impact.

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Related Topics and Keywords

Atirmociclib, breast cancer, CDK4, metastatic breast cancer, Pfizer, Phase 2 Results