Pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives as RAF-MEK-ERK pathway signaling pathway blockers: Synthesis, cytotoxic activity, mechanistic investigation and structure-activity relationships.

The constitutive activation of ERK1/2 (RAF-MEK-ERK) signaling pathway has been widely observed in many types of tumors, and the blockade of ERK1/2 signaling pathway has been proved to reduce tumor growth. Therefore, ERK1/2 signaling pathway has become an interesting therapeutic target for cancer therapy. Despite the successful development of BRAF and MEK inhibitors in clinic treatment, resistance often appears to re-enhance ERK1/2 signaling. Here we report the design, synthesis, biological activity of a series of novel pyrido[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives based on compound 1. Among them, the target compound N-(3-chlorophenyl)-2-((1,3-dimethyl-7-(4-methylpiperazin-1-yl)-2,4-dioxo-1,2,3,4-tetrahydropyrido[2,3-d]pyrimidin-5-yl)amino)acetamide (14m) exhibited excellent antiproliferative activity towards MCF-7, A375, SK-MEL-2 and SK-HEP-1 cells, with low cytotoxicity in C28/I2 cells. Tumor spheroid assay demonstrated the superior potency of 14m in inhibiting the growth of SK-HEP-1 spheroidal models. The mechanism of 14m to induce cancer cell death was shown to suppress cell migrations, induce cell apoptosis, decrease the levels of phosphorylated ERK and MEK in a dose-dependent manner and increase ROS production.