The epidermal growth factor receptor is a receptor tyrosine kinases that signals in response to various growth factors. Overexpression has been linked to numerous types of cancer and EGFR is the target of both biological and small molecular therapeutics. The double T790M L858R mutant of EGFR displays resistance to Erlotinib (Tarceva) and sensitivity to HKI-272 and rapamycin combination therapy.