Even though lung cancer patients harboring a mutation in the epidermal growth factor receptor (EGFR) gene exhibit an initial dramatic response to EGFR tyrosine kinase inhibitors (EGFR-TKIs), acquired resistance is almost inevitable after a progression-free period of approximately 10 months. A secondary point mutation that substitutes methionine for threonine at amino acid position 790 (T790M) is a molecular mechanism that produces a drug-resistant variant of the targeted kinase. The T790M mutation is present in about half of the lung cancer patients with acquired resistance, and reported to act by increasing the affinity of the receptor to adenosine triphosphate, relative to its affinity to TKIs.
