Pfizer (NYSE:PFE) reported a significant clinical milestone in its oncology pipeline today, announcing that the Phase 2 FOURLIGHT-1 study of atirmociclib met its primary endpoint.
The trial evaluated the investigational, potential first-in-class CDK4 inhibitor in combination with fulvestrant for patients with hormone receptor-positive (HR+), HER2-negative advanced or metastatic breast cancer.
The study specifically targeted a difficult-to-treat population: those whose disease had progressed following prior treatment with the current standard-of-care, CDK4/6 inhibitors.
The combination of atirmociclib and fulvestrant demonstrated a statistically significant and clinically meaningful improvement in progression-free survival (PFS) compared to the control arms of fulvestrant alone or a combination of everolimus and exemestane.
The study yielded a hazard ratio of 0.60, representing a 40% reduction in the risk of disease progression or death.
Notably, these results remained consistent across all prespecified patient subgroups, regardless of menopausal status, the presence of visceral disease, or the specific type of prior CDK4/6 inhibitor received.
Atirmociclib is designed to be more selective than existing treatments by specifically targeting the CDK4 enzyme, which is a key driver of cell cycle progression in breast cancer.