Lapatinib Ditosylate (Tykerb) was found to have 50% inhibitory concentration (IC50) values against purified EGFR and HER2 of 10.2 and 9.8 nM, respectively. And IC50 >10000nM against c-Raf-1,MEK,ERK,CDK1CDK2,p38 and VEGFR-2.
The IC50s for inhibition of cell growth by 72h treatment with GW2016 are 0.16μM for A431,0.12 μM for HN5,0.10 μM for BT474,0.09 μM for N87.
Lapatinib undergoes first-pass metabolism catalyzed by CYP3A4/5 and does not appear to be a substrate for P-glycoprotein. [2]