A Study of MEHD7945A Versus Cetuximab in Patients With Recurrent/Metastatic Squamous Cell Carcinoma of The Head And Neck

Inclusion Criteria: * Adult patients, \>/= 18 years of age * Histologically confirmed Stage III or IV recurrent/metastatic squamous cell carcinoma of the head and neck (R/M SCCHN) * Progressive disease on or after first-line platinum-based chemotherapy regimen for R/M SCCHN (maximum of 6 cycles) * No more than one platinum-based chemotherapy regimen for R/M SCCHN is allowed * Prior platinum-based treatment as definitive chemo/radiotherapy for locally advanced disease is allowed if completed/terminated \>/= 6 months before the platinum-based regimen for R/M SCCHN * Consent to provide archival tumor tissue for biomarker testing * Measurable disease per RECIST v1.1 * ECOG performance status of 0, 1 or 2 * Adequate hematologic, renal and liver function Exclusion Criteria: * Nasopharyngeal cancer * Prior treatment with an investigational or approved agent for the purpose of inhibiting HER family members * This includes but is not limited to cetuximab, panitumumab, erlotinib, geftinib, and lapatinib * Prior treatment with an EGFR inhibitor is allowed if it was administered as part of definitive therapy for locally advanced disease and completed \>/=1 year before study enrollment * Leptomeningeal disease as the only manifestation of the current malignancy * Active infection requiring iv antibiotics * Active autoimmune disease that is not controlled by non-steroidal anti-inflammatory drugs * Current severe, uncontrolled systemic disease (e.g. clinically significant cardiovascular, pulmonary, or metabolic disease; wound healing disorders; ulcers; bone fractures) * History of heart failure or serious cardiac arrhythmia * History of myocardial infarction within 6 months of Cycle 1, Day 1 * Clinically significant liver disease, including active viral, alcoholic or other hepatitis, cirrhosis, or current alcohol abuse * HIV infection * Primary central nervous system (CNS) malignancy or untreated/active CNS metastases (progressing or requiring anticonvulsants or corticosteroids for symptomatic control) * Pregnant or lactating women * Malignancies other than SCCHN within 5 years prior to randomization, with the exception of adequately treated basal or squamous cell skin cancer and carcinoma in situ of the cervix