This is a randomized, open-label, multi-center, global, Phase II study to determine the efficacy and safety of MEDI4736 + tremelimumab combination therapy, MEDI4736 monotherapy and tremelimumab monotherapy in the treatment of patients with recurrent or metastatic PD-L1-negative squamous cell carcinoma of the head and neck (SCCHN) who have progressed during or after treatment with only 1 systemic palliative regimen for recurrent or metastatic disease, that must have contained a platinum agent.