Lapatinib is a 4-anilinoquinazoline kinase inhibitor of the intracellular tyrosine kinase domains of both epidermal growth factor receptor (HER1/EGFR/ERBB1) and human epidermal growth factor receptor type 2 (HER2/ERBB2)with a dissociation half-life of ≥300 minutes. Lapatinib inhibits ERBB-driven tumor cell growth in vitro and in various animal models. An additive effect was demonstrated in an in vitro study when lapatinib and 5-florouracil (the active metabolite of capecitabine) were used in combination in the 4 tumor cell lines tested. The growth inhibitory effects of lapatinib were evaluated in trastuzumab-conditioned cell lines. Lapatinib retained significant activity against breast cancer cell lines selected for long-term growth in trastuzumab-containing medium in vitro. These in vitro findings suggest non-cross-resistance between these two agents.
Lapatinib is a small molecule and a member of the 4-anilinoquinazoline class of kinase inhibitors. An anti-cancer drug, lapatinib was developed by GlaxoSmithKline (GSK) as a treatment for solid tumours such as breast and lung cancer. It was approved by the FDA on March 13, 2007, for use in patients with advanced metastatic breast cancer in conjunction with the chemotherapy drug capecitabine.
Lapatinib undergoes extensive metabolism, primarily by CYP3A4 and CYP3A5, with minor contributions from CYP2C19 and CYP2C8 to a variety of oxidated metabolites, none of which accounts for more than 14% of the dose recovered in the feces or 10% of lapatinib concentration in plasma.
There has been a report of one patient who took 3, 000 mg of lapatinib for 10 days. This patient had grade 3 diarrhea and vomiting on day 10.