A First-in-Human Phase 1 Safety and Biodistribution of [177Lu]Lu-ABY-271 in Subjects With HER2-positive Metastatic Breast Cancer

This is a first-in-human safety study of a new type of targeted radiation treatment called [177Lu]Lu-ABY-271, which uses a small molecule that seeks out HER2 protein on cancer cells and delivers radiation directly to them. It is being tested in people with advanced HER2-positive breast cancer that has spread (metastatic) and cannot be surgically removed. **You may be eligible if...** - You have locally advanced or metastatic breast cancer - Your tumor has confirmed high HER2 expression (a protein that helps cancer cells grow) - You have at least one tumor lesion 15mm or larger - You are in reasonably good health (ECOG 0–2) - For Part B: Your cancer has progressed through at least 3 prior standard treatment lines **You may NOT be eligible if...** - You have active brain metastases - You have recently received another investigational drug or anti-tumor therapy since your last documented cancer progression Talk to your doctor to see if this trial is right for you.