AST-1306 is a selective irreversible inhibitor of the epidermal growth factor receptor (EGFR) 1 and 2. Studies show that AST-1306 inhibited the enzymatic activities of wild-type EGF) and ErbB2 as well as EGFR resistant mutant in both cell-free and cell-based systems. AST-1306 was more effective in inhibiting tumors with ErbB2-overexpressing cells than EGFR-overexpressing tumor.