Once daily dosing of 1250 mg lapatinib, the approved dose in combination with capecitabine, achieves minimum steady-state plasma concentrations in the low μΜ range throughout most of the dosing interval [12], which exceeds the IC90 (~900 nM or 500 ng/mL) for lapatinib in multiple HER2+ human breast cancer cell lines [10]. Here, ERBB2 is linked to breast carcinoma.