Study on Patritumab Deruxtecan and Trastuzumab Deruxtecan for Advanced Breast Cancer

Inclusion Criteria

• Have breast cancer that cannot be surgically removed or has spread to other parts of the body.
• Cancer must be hormone receptor-positive, meaning it has estrogen or progesterone receptors.
• Cancer must have low or very low levels of HER2 protein, as determined by specific tests.
• Provide a tumor sample from a recent biopsy or a new biopsy if needed.
• Cancer must have shown progression after previous treatment.
• Must have tried hormone therapy for advanced cancer and it is no longer effective.
• Have previously used a CDK4/6 inhibitor.
• If eligible for other targeted therapies, must have tried them unless not available or suitable.
• No prior chemotherapy for advanced breast cancer, but previous chemotherapy for early-stage cancer is allowed.
• Be in good overall health with a performance status of 0 or 1.
• Have at least one measurable tumor on a scan.
• Have adequate blood cell counts and organ function based on recent tests.

Exclusion Criteria

• Have previously been treated with anti-HER3 drugs or similar therapies.
• Have a history of lung diseases like interstitial lung disease or pneumonitis.
• Are taking high doses of steroids or other immunosuppressive drugs.
• Have active or untreated brain or spinal cord metastases.
• Have not had enough time since previous treatments before starting the study.
• Have uncontrolled heart conditions or significant heart disease.
• Have had another active cancer within the last 3 years, except for certain skin or cervical cancers.
• Have unresolved side effects from previous cancer treatments.
• Have allergies to the study drugs or their ingredients.