Synthesis and antitumor activity of novel pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-one derivatives

► New pyrido[2,3-d][1,2,4]triazolo[4,3-a]pyrimidin-5-ones bearing different substituents at position 3 were synthesized. ► Some of these new compounds exhibited good antitumor activity against MCF7 when compared to doxorubicin as a reference drug. ► The best results was obtained by derivatives bearing thioxo, alkylthio or amino groups at position 3. ► The 3-amino derivative 12 was the most potent compound in this screening with IC50 equal to 3.74 μg/mL.