SKB264 Plus Inetetamab in HER2-Positive Metastatic Breast Cancer Patients Progressing After T-DXd Treatment

This study is testing a combination of SKB264 (a new antibody-drug conjugate) with inetetamab (a HER2-targeted antibody) in people with HER2-positive metastatic breast cancer that has already been treated with trastuzumab deruxtecan (T-DXd) and trastuzumab. **You may be eligible if...** - You are 18 or older - You have HER2-positive breast cancer that has spread (metastatic) or cannot be surgically removed - You have previously received both trastuzumab (or a biosimilar) and trastuzumab deruxtecan (T-DXd) for advanced disease - Your cancer is measurable on imaging - You have adequate organ function and a good performance status **You may NOT be eligible if...** - Your cancer is not HER2-positive - You have not received prior T-DXd and trastuzumab - You have active brain metastases, severe lung problems, or serious heart conditions - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.