BIBW-2992 is a potent irreversible EGFR/HER2 inhibitor. The potency of BIBW-2992 on the EGFR and HER2 kinases revealed IC₅₀ values of 0.5 nM and 14 nM, respectively. BIBW-2992 is highly selective for these kinases and no additional inhibition of other kinases has been observed.