629-B Window of opportunity for durvalumab plus metformin trial in head & neck squamous cell carcinoma (HNSCC) by Madalina Tuluc, Jennifer Johnson, Derek Mann, Ubaldo Martinez-Outschoorn, Adam J Luginbuhl, Athanassios Argiris, Ramez Philips, Angela Alnemri, Sruti Tekumalla, Hushan Yang, Alban Linnenbach, Diana Menezes, Voichita Bar-Ad, David Cognetti, Ramakrishna Mitra, Joseph M Curry