Synthesis and antitumor evaluation of novel 4‐anilino‐7,8‐dihydropyrido[4,3‐d]pyrimidine‐6(5H)‐carboxylate derivatives as potential EGFR inhibitors

: Novel series of 4-anilino-7,8-dihydropyrido[4,3-d]pyrimidine-6(5H)-carboxylates (5a-p, 7, and 8a-e) were synthesized and evaluated for their antiproliferative activity against the A549, HT29, H460, and H1975 cancer cell lines in vitro. Nine compounds (5a-c, 5i, 5j, 7, 8a, 8b, 8i) demonstrated moderate to significant cytotoxic activity with IC50 values below 18 µM on A549 cells, which were comparable to that of the reference gefitinib (IC50  = 18.44 µM). Especially, the further enzymatic analysis on epidermal growth factor receptor (EGFR), HER2, and VEGFR identified compound 5a as a promising hit that exhibited considerable potency both in cellular (IC50  = 5.67, 17.04, 11.29, and 12.65 µM, respectively) and EGFR enzymatic assays (IC50  = 14.8 nM). Compound 5a was capable of down-regulating the expression of EGFR and inhibited EGFR phosphorylation in a dose-dependent manner, representing a potential EGFR candidate for further optimization.