A drug used with other drugs to treat adults with extensive-stage small cell lung cancer that has not already been treated. It is also used alone to treat adults with stage III non-small cell lung cancer that cannot be removed by surgery and did not get worse after treatment with radiation therapy and anticancer drugs that included platinum. Durvalumab is also used alone to treat adults with urothelial carcinoma (a type of bladder cancer) that is advanced or has spread to other parts of the body and got worse during or after treatment with anticancer drugs that included platinum. It is also being studied in the treatment of other types of cancer. Durvalumab binds to a protein called PD-L1, which is found on some cancer cells. Durvalumab may block this protein and help the immune system kill cancer cells. It is a type of monoclonal antibody and a type of immune checkpoint inhibitor. Also called Imfinzi.