Atezolizumab in Large Cell Neuroendocrine Carcinoma

Cohorts A and B: Inclusion Criteria: * Histologically confirmed Stage IV (metastatic) or unresectable locally advanced LCNEC * No prior treatment * With or without brain metastasis, if symptomatic patients should be treated with WBRT first * Performance Status ≤ 2 * Life expectancy \> 3 months * Written informed consent * Measurable disease according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 Exclusion Criteria: * Prior treatment with chemotherapy, immunotherapy, targeted small molecule therapy, or radiation therapy (except WBRT for brain metastasis from LCNEC) * Active or history of autoimmune disease or immune deficiency * Treatment with systemic immunosuppressive medications with the following exceptions: Patients who have received acute, low-dose systemic immunosuppressant medication (≤ 10 mg/day oral prednisone or equivalent) or a one-time pulse dose of systemic immunosuppressant medication (e.g., 48 hours of corticosteroids for a contrast allergy) are eligible for the study after Medical Monitor approval has been obtained. * Major surgical procedure other than for diagnosis within 4 weeks before initiation of study treatment, or anticipation of need for a major surgical procedure during the study * Active malignancy or malignancy within 3 years * Active tuberculosis * Current severe, uncontrolled systemic disease other than cancer * Known clinically significant liver disease * Treatment with any other investigational agent or participation in an…