In vitro
Lapatinib can inihbit Epidermal growth factor receptor (erbB1) with IC50 of 2.9 nM.[1] Lapatinib also inhibit receptor protein-tyrosine kinase(erbB-2) with IC50 around 3 nM.[1] Overexpression of ABC subfamily B member 1 (ABCB1) and ABC subfamily G member 2 (ABCG2) transporters would result in tumor multidrug resistance (MDR). Lapatinib significantly enhanced the sensitivity to ABCB1 or ABCG2 substrates in cells by stimulating the ATPase activity of both ABCB1 and ABCG2. And lapatinib reverses ABCB1- and ABCG2-mediated MDR by directly inhibiting their transport function so that lapatinib (Tykerb, GW572016) may combinate with other inhibitors to block proliferation of cancer cells and get better results. Lapatinib can inhibit SK-OV-3, an Ovarian carcinoma cell line which overexpress HER2, with IC50 from 3 to 4.5 nM.
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