Structure-based design of potent inhibitors of EGF-receptor tyrosine kinase as anti-cancer agents

In a systematic effort to design inhibitors of the epidermal growth factor receptor (EGFR) family protein tyrosine kinases (PTK) as anti-cancer agents , we have constructed a three-dimensional homology model of the EGFR kinase domain and used molecular modeling methods for the structure-based design of analogs of the active metabolite of leflunomide (LFM) with potent and sp ecific inhibitory activity against EGFR. These docking studies identified a lpha-cyano-beta-hydroxy-beta-methyl-N-[4-(trifluoromethoxy)phenyl]-propenam ide (LFM-A12) as our lead compound, which was predicted to bind to the EGFR catalytic site in a planar conformation. LFM-A12, inhibited the proliferat ion (IC50 = 26.3 mu M) and in vitro invasiveness (IC50 = 28.4 mu M) of EGFR positive human breast cancer cells in a concentration-dependent fashion. S imilarly, the model of the EGFR binding pocket was used in combination with docking procedures to predict the favorable placement of chemical groups w ith defined sizes at multiple modification sites on another class of EGFR i nhibitors, the 4-anilinoquinazoline. This approach has led to the successfu l design of a dibromo quinazoline derivative, WHI-P97, which had an estimat ed K-i value of 0.09 mu M from modeling studies and a measured IC50 value o f 2.5 mu M in EGFR kinase inhibition assays, WHI-P97 effectively inhibited the in vitro invasiveness of EGFR-positive human cancer cells in a concentr ation-dependent manner. However, unlike LFM-A12, the quinazoline compounds are not specific for EGFR.