<p>Lapatinib is a 4-anilinoquinazoline tyrosine kinase inhibitor of both Epidermal Growth Factor Receptor (EGFR [ErbB1]) and Human Epidermal Receptor Type 2 (HER2 [ErbB2]) receptors. It blocks the phosphorylation and activation of downstream 2nd messengers (Erk1/2 and Akt) which regulate cellular proliferation and survival of ErbB- and ErbB2-expressing tumours.</p>