The study is testing ARX788, a medicine for people with a certain type of breast cancer called HER2-positive metastatic breast cancer. Metastatic means the cancer has spread to other parts of the body. HER2-positive means the cancer cells have more HER2 protein than normal. ARX788 is given through an IV every three weeks. The study is for adults who have already tried up to five other treatments, including one called T-DXd.

Here are some key points to consider:

• Study Length: Participants will receive ARX788 every 3 weeks.
• Eligibility: Must be 18 or older with life expectancy of at least 6 months, and have previously tried T-DXd treatment.
• Exclusions: Cannot join if you have severe lung or heart conditions, certain brain issues, or allergies to ARX788.

Before joining, make sure you discuss with your doctor to see if you're fit for this study and understand all the requirements and risks. You must agree to follow the study rules and give permission to use your medical information. This study helps doctors learn more about ARX788's effectiveness and safety.