Platform Study of ADC Rechallenge in ADC-treated Metastatic Breast Cancer

This is a platform study testing whether re-treating patients with a class of drugs called antibody-drug conjugates (ADCs) — targeted therapies that deliver chemotherapy directly to cancer cells — can still work in metastatic breast cancer patients who have already received an ADC but whose cancer has progressed. **You may be eligible if...** - You are 18 or older - You have locally advanced or metastatic breast cancer that has come back - You have already received at least one ADC treatment - You have measurable disease on imaging - If your breast cancer is hormone receptor-positive, you have already received a CDK4/6 inhibitor - Your blood counts, liver, and kidney function are at acceptable levels **You may NOT be eligible if...** - You have not previously received an ADC - Your organ function is too poor for treatment - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.