Kumakogen

Researchers are evaluating the effectiveness and safety of adding Tersolisib (LY4064809/STX-478) to other anti-cancer drugs as the first treatment for adults with advanced hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2-) breast cancer. This phase 3 study focuses on participants whose cancer has a specific genetic change called a PIK3CA mutation and who have not received prior treatment for advanced breast cancer. The study aims to understand how well this treatment combination works and its safety over time. Participants will receive Tersolisib or a placebo, combined with a CDK4/6 inhibitor (Ribociclib, Palbociclib, or Abemaciclib) and endocrine therapy (Anastrozole, Letrozole, Exemestane, or Fulvestrant). All drugs are given orally except for Fulvestrant, which is given by injection into the muscle. The study includes two parts: Part 1 allows participants who have had up to two prior treatments for advanced breast cancer, including chemotherapy; Part 2 includes those with no prior treatment for advanced disease and classifies them as endocrine sensitive or resistant based on their cancer history. During the study, participants will be regularly assessed for cancer response, progression-free survival, and side effects. Researchers will monitor measurable disease or bone involvement and track overall response rates, including complete or partial tumor shrinkage. The study will continue as long as the treatment is helping without causing unbearable side effects. Follow-up may last up to five years to observe long-term outcomes and safety.