Can a Triple-Drug combo keep advanced breast cancer in check?

This phase II trial is testing whether adding a new oral drug called culmerciclib to standard anti-HER2 therapy and hormone therapy can help maintain control of advanced breast cancer that is both hormone receptor-positive and HER2-positive. The study enrolls women with metastatic or locally advanced breast cancer that cannot be removed surgically. Participants receive culmerciclib at increasing doses along with trastuzumab (with or without pertuzumab) and a doctor-chosen endocrine therapy, continuing until the disease worsens or side effects become unacceptable. The main goal is to see how long the cancer stays under control.