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 mu M on A549 cells, which were comparable to that of the reference gefitinib (IC50=18.44 mu M). 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 mu M, respectively) and EGFR enzymatic assays (IC50=14.8nM). 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.