Patients are being asked to take part in this clinical research study because they have advanced, un-resectable stage III or IV Melanoma. If they participate they will be randomized to receive Pembrolizumab (KEYTRUDA®) or the combination of Pembrolizumab (KEYTRUDA®) plus Metformin.~This research study will evaluate the effectiveness and safety of the combination of Pembrolizumab (KEYTRUDA®) and the investigational drug, Metformin.~Patients will be randomized into one of two groups - either Arm A or Arm B. In Arm A, patients will receive pembrolizumab alone. In Arm B, patients will receive both pembrolizumab and metformin.~If patients are randomized to Arm A, they will be administered pembrolizumab (200 mg), by IV, every three weeks. After the first three doses, pembrolizumab dosing can be changed to 400mg IV every 6 weeks, at the treating physician's discretion. Pembrolizumab can be administered up to two years, if disease does not progress or have unacceptable toxicity. However, if the disease progresses the patient may continue on the study if they are clinically stable or clinically improved.~If patients are randomized to Arm B, they will be administered pembrolizumab (200 mg), by IV, every three weeks, plus metformin (500 mg), twice a day for nine weeks. Metformin will be taken in the morning and evening, 12hrs apart, with food. After the first three doses, pembrolizumab dosing can be changed to 400mg IV every 6 weeks, at the treating physician's discretion.~Discontinuation of treatment may be considered for patients who have attained a confirmed complete response that have been treated for at least 24 weeks with pembrolizumab and had at least two treatments with pembrolizumab beyond the date when the initial complete response was declared.~Patients will be followed for 5 years after removal from study or until death, whichever occurs first, through standard of care visits, phone call or by medical records review.
The purpose of this study is to evaluate the effectiveness and safety of the combination of Pembrolizumab (KEYTRUDA®) and the investigational drug, Metformin.