This clinical trial is focused on studying a type of breast cancer known as HER2-positive, HR-positive breast cancer. This type of cancer is characterized by the presence of certain proteins and hormone receptors that can promote the growth of cancer cells. The study involves a combination of treatments to evaluate their safety and how well they are tolerated by patients. The treatments being studied include a new medication called JZP598, which contains the active substance zanidatamab, and two other medications, palbociclib and fulvestrant. These medications are used together to see if they can effectively manage the disease.
The purpose of the study is to find a suitable dose of JZP598 when used with palbociclib and fulvestrant and to assess the combination’s ability to control the cancer. The study is divided into two parts. In the first part, researchers will determine the best dose of JZP598 to use with the other medications. In the second part, they will evaluate how well this combination works in treating the cancer. Participants will receive the medications through different methods: JZP598 is given as an infusion, palbociclib is taken orally as a capsule, and fulvestrant is administered as an injection.
Throughout the study, participants will be monitored for any side effects and how their cancer responds to the treatment. The study aims to provide valuable information on the effectiveness and safety of using these medications together for treating HER2-positive, HR-positive breast cancer. The trial is expected to continue until early 2026, with the goal of improving treatment options for patients with this type of breast cancer.



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