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Sanofi Ends Development of Breast Cancer Drug Amcenestrant

NEW YORK – Sanofi on Wednesday announced it is discontinuing development of its selective estrogen receptor degrader amcenestrant after it failed to meet a prespecified endpoint in the Phase III AMEERA-5 trial.

In the study, Sanofi was comparing amcenestrant plus Pfizer's CDK 4/6 inhibitor Ibrance (palbociclib) versus letrozole plus Ibrance in patients with estrogen receptor (ER)-positive, HER2-negative advanced breast cancer. Sanofi said that an independent data monitoring committee analyzed the study and found the amcenestrant combination did not meet a prespecified boundary for continuation in comparison with the control arm, and subsequently recommended stopping the trial.

The primary endpoint for the AMEERA-5 trial was progression-free survival. Sanofi noted that no new safety signals were observed and that patients in the study will be transitioned to standard-of-care therapy. The company will continue to review the data and report results in the future.

Earlier this year, Sanofi reported that amcenestrant monotherapy failed to meet its primary endpoint in the Phase II AMEERA-3 trial. The drug did not improve progression-free survival in patients with locally advanced or metastatic ER-positive, HER2-negative breast cancer compared to physician's choice of endocrine therapy.

With these two trial failures, Sanofi is ending all development programs for amcenestrant, including the Phase III AMEERA-6 study of the drug as an adjuvant therapy for hormone receptor-positive early-stage breast cancer. The AMEERA-6 trial started enrolling patients this year.