A drug used to treat certain types of small cell lung cancer, breast cancer, non-small cell lung cancer, and urothelial cancer (a type of bladder cancer). It is also being studied in the treatment of other types of cancer. Atezolizumab binds to a protein called PD-L1, which is found on some cancer cells. Atezolizumab 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 Tecentriq.