Lapatinib is a small molecule and a member of the 4-anilinoquinazoline class of kinase inhibitors. It is present as the monohydrate of the ditosylate salt (trade name TYKERB). Lapatinib is dual inhibitor of the EGFR (epidermal growth factor receptor; also called HER1 or ErbB1) and HER2 receptor tyrosine kinases. Lapatinib was developed by GlaxoSmithKline, however, Novartis subsequently acquired all the rights to the drug from GlaxoSmithKline. TYKERB is indicated in combination therapy for the treatment of metastatic breast cancer that overexpresses the HER2 receptor.