3,5-dimethyl-pyrido-1,2,3,5-tetrazepin-4-one

PYRZ, also known as 3,5-dimethyl-pyrido-1,2,3,5-tetrazepin-4-one, is a novel cytotoxic heterocycle structurally related to temozolomide. Despite its structural similarities to temozolomide, PYRZ exhibits a distinct mechanism of action. It inhibits the synthesis of DNA, RNA, and protein, and induces dose-dependent DNA fragmentation. This leads to an accumulation of cells in the late S and G2+M phases of the cell cycle. PYRZ has demonstrated significant cell-killing kinetics in human epithelial ovarian cancer cell lines, with 50-90% cell killing observed within 24 hours at micromolar concentrations. Its mechanism of action is considered atypical for 1,2,3-triazene-containing alkylating agents, as it shows only background levels of DNA alkylation compared to temozolomide.