Recurrent and/or metastatic HNSCC patients will be treated with combination of metformin and pembrolizumab. Patients will be randomized into arms 1 and 2, to either receive Metformin prior to pembrolizumab or to begin Metformin after pembrolizumab treatment begins. The patients are randomized for the exploratory endpoints in order to better understand the difference of effects of metformin versus pembrolizumab on the immune system although efficacy is based on combination.
The purpose of this study is to determine anti-tumor activity by measuring overall response rate in recurrent and/or metastatic HNSCC patients receiving the combination of metformin and pembrolizumab.