A Trial of Pembrolizumab and Metformin Versus Pembrolizumab Alone in Advanced Melanoma

This trial is testing whether adding the diabetes drug metformin to an immunotherapy drug called pembrolizumab improves outcomes for patients with advanced melanoma (a serious form of skin cancer) that cannot be surgically removed. **You may be eligible if...** - You are 18 or older with stage III or stage IV melanoma that cannot be removed by surgery - Your disease is measurable on scans - You are well enough to participate (good performance status) - You are willing to give written informed consent **You may NOT be eligible if...** - You have already received pembrolizumab or other similar immunotherapy drugs - You have serious autoimmune disease - You have uncontrolled diabetes or conditions that make metformin unsafe - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.