This review focuses on the cytotoxic effect of new synthetic pyrazolo[4,3-e][1,2,4]triazine derivatives against different tumor cell lines. Some annulated pyrazolotriazines i.e., pyrazolo[4,3-e][1,2,4]triazolo[4,3-b][1,2,4]triazines and pyrazolo[4,3-e]tetrazolo[1,5-b][1,2,4]triazine demonstrated significant broad cytotoxic activity in micromolar range concentration, which could have excellent potential to be new candidate therapeutic agents in cancer chemotherapy.
