EGFR/HER2/DHFR-IN-3 (compound 4c) is a potent dual inhibitor of EGFR/HER2 , with IC 50 s of 0.138 and 0.092 μM, respectively. EGFR/HER2/DHFR-IN-3 also inhibits DHFR , with an IC 50 of 0.193 M. EGFR/HER2/DHFR-IN-3 causes arrest at the S phase of the cell cycle and induces apoptosis in MCF7 breast cancer cells.