Cytotoxicity of lapatinib versus O-debenzylated lapatinib in HepaRG cells and the effect of glutathione depletion by BSO on lapatinib-induced cytotoxicity. (A) HepaRG cells were incubated with LAP or LAP-OH (10, 50, 100 μM) or vehicle control for 24 hours. Cell viability was monitored using WST-1 assays. (B) HepaRG cells were pretreated with 25 μM BSO for 24 hours, prior to incubation with LAP (10, 50, 100 μM) or vehicle control for 24 hours. For (A), LAP-OH was compared with incubation with LAP at each concentration. Data represent means ± S.E.M. of triplicate values from three independent experiments. For (B), LAP + BSO was compared with incubation with LAP alone at each concentration. Data represent the mean ± S.D. of triplicate values. *P < 0.05; **P < 0.01; ***P < 0.001 (unpaired t test, two-tailed P values).