ARM I: Patients receive tremelimumab intravenously (IV) over 1 hour on day 1. Treatment repeats every 4 weeks for up to 4 courses in the absence of disease progression or unacceptable toxicity. Patients also receive durvalumab IV over 1 hour on day 1. Treatment repeats every 4 weeks for up to 1 year in the absence of disease progression or unacceptable toxicity. Patients achieving disease control may restart treatment upon evidence of progressive disease, with or without confirmation.