A drug used to treat certain types of non-small cell lung cancer. It is also used together with gemcitabine to treat pancreatic cancer and is being studied in the treatment of other types of cancer. Tarceva is a type of epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor. Also called CP-358,774, erlotinib, erlotinib hydrochloride, and OSI-774.