Potential new EGFRT790M inhibitors comprised of structurally modified diphenylpyrimidine derivatives bearing a morpholine functionality (Mor-DPPYs) were used to improve the activity and selectivity of gefitinib-resistant non-small cell lung cancer (NSCLC) treatment. This led to the identification of inhibitor 10c, which displayed high activity against EGFRT790M/L858R kinase (IC50 = 0.71 nM) and repressed H1975 cell replication harboring EGFRT790M mutations at a concentration of 0.037 μM. Inhibitor 10c demonstrated high selectivity (SI = 631.9) for T790M-containing EGFR mutants over wild type EGFR, suggesting that it will cause less side effects. Moreover, this compound also shows promising antitumor efficacy in a murine EGFRT790M/L858R-driven H1975 xenograft model without affecting body weight. This study provides new potential lead compounds for further development of anti-NSCLC drugs.