Phase 3 Study Comparing Palazestrant Plus Ribociclib With Letrozole Plus Ribociclib for First-Line Treatment of ER, HER2- Advanced Breast Cancer

What this Trial Is About

Researchers are evaluating the effectiveness and safety of palazestrant combined with ribociclib compared to letrozole combined with ribociclib in adults with advanced breast cancer that is estrogen receptor positive ER and human epidermal growth factor receptor 2 negative HER2-. This phase 3 clinical trial includes women and men who have not yet received systemic treatment for their advanced breast cancer, aiming to find improved first-line treatment options. Participants are randomly assigned to one of two groups one group receives palazestrant 90 mg daily with ribociclib 600 mg daily taken on days 1-21 of each 28-day cycle plus a placebo matching letrozole the other group receives letrozole 2.5 mg daily with ribociclib 600 mg daily plus a placebo matching palazestrant. Treatments are given in repeating 28-day cycles. The study is double-blind and active-controlled, meaning neither participants nor researchers know who receives which treatment, and both groups receive active drugs. During the trial, participants will be monitored regularly for disease progression and survival over approximately 3.5 to 5.5 years. Assessments include tumor response evaluations, safety and tolerability checks, pharmacokinetic blood tests every 28 days, and patient-reported health outcomes. The primary outcome is progression-free survival, measuring the time from randomization until disease worsens or death. Safety monitoring continues for up to 42 days after treatment ends, with the study lasting until 2032.

Palazestrant in Combination With Ribociclib for the First-line Treatment of ER+/HER2- Advanced Breast Cancer