EGFR inhibitor is a cell permeable, pyrimidine compound that selectively inhibits the EGFR kinase with IC50 value of 21 nM [1].

EGFR is a transmembrane protein, and is a receptor for members of epidermal growth factor family. The binding of EGFR with its ligands induces receptor dimerization and tyrosine autophosphorylation, and leads to cell proliferation. The overactivity of EGFR tyrosine kinases is associated with a number of cancers, inhibition of EGFR can downregulate antiapoptotic proteins such as surviving and upregulate proapoptotic proteins such as Bim. Thus, EGFR inhibitor can induce cell apoptosis, resulting in anti-tumor effectivity [2].

EGFR inhibitor inhibited EGFR kinase in vitro and blocks receptor autophosphorylation in cells. EGFR inhibitor also inhibited L858R and L861Q EGFR mutants with IC50 values of 63 and 4 nM, respectively [1].

References:
1.  Q. Zhang, Y. Liu, F. Gao, et al. Discovery of EGFR selective 4,6-disubstituted pyrimidines from a combinatorial kinase-directed heterocycle library. Journal of the American Chemical Society 128(7), 2182-2183 (2006).
2.  F. Ciardiello, G. Tortora. EGFR antagonists in cancer treatment. New England Journal of Medicine 358(11), 1160-1174 (2008).