Design, Synthesis and Antitumor Activity Evaluation in Vitro of Novel 1,6-Naphthyridine Derivatives

In the search for novel, highly effective antitumor agents, a series of novel 1,6-naphthyridine derivatives were designed, synthesized and evaluated for antiproliferative activity against five human cancer cell lines (HepG-2, MCF-7, NCI-H1650, U87MG and A549) using CCK-8 assay in vitro . Among them, compound (R)-N-(1-(3-(difluoromethyl)-2-fluorophenyl)ethyl)-8-(3-ethylphenyl)-7-methoxy-1,6-naphthyridin-4-amine ( 16f ) exhibited promising broad-spectrum activity against all tested cell lines. It was particularly potent against U87MG cells, with IC ₅₀ values of 3.28±0.15 μM. The antitumor activity was significantly better than that of the positive control 5-Fluorouracil. Preliminary mechanistic studies revealed that compound 16f inhibited the clonogenic formation and migration of U87MG cells in a concentration-dependent manner, with migration inhibition also showing time dependence. Furthermore, 16f induced apoptosis in a concentration-dependent manner by increasing the reactive oxygen species level within the cells. At a concentration of 4 μM, the apoptotic cell population increased from 3.92% (control) to 25.18%, representing a 6.4-fold increase. Nuclear damage observed via DAPI staining provided further evidence of its cytotoxic effects. The DAPI staining further confirmed the cytotoxic action of compound 16f , showing clear morphological damage to the nuclei of U87MG cells. Collectively, these findings indicate that compound 16f is a promising candidate for further development as a potent antitumor drug.