MC1R-targeted Alpha-particle Monotherapy and Combination Therapy Trial With Nivolumab in Adults With Advanced Melanoma

This study tests a new type of targeted radiation therapy (called alpha-particle therapy) that specifically seeks out melanoma cells using a protein called MC1R found on their surface. It is being tested alone and in combination with nivolumab (an immunotherapy drug) in adults with advanced melanoma. **You may be eligible if...** - You are 18 or older - You have advanced melanoma (unresectable Stage III or Stage IV) that has come back or progressed after at least one approved treatment - Your melanoma tumors show uptake of the targeting agent on imaging scans - Your overall health and organ function meet study requirements **You may NOT be eligible if...** - You have not previously received treatment for advanced melanoma - Your tumors do not show uptake of the imaging agent used in this study - You have serious medical conditions that would make participation unsafe - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.