Identification of 1,2,4-triazoles as new thymidine phosphorylase inhibitors: Future anti-tumor drugs

Thymidine phosphorylase (TP) is over expressed in several solid tumors and its inhibition can offer unique target suitable for drug discovery in cancer. A series of 1,2,4-triazoles 3a-3l has been synthesized in good yields and subsequently inhibitory potential of synthesized triazoles 3a-3l against thymidine phosphorylase enzyme was evaluated. Out of these twelve analogs five analogues 3b, 3c, 3f, 31 and 31 exhibited a good inhibitory potential against thymidine phosphorylase. Inhibitory potential in term of IC50 values were found in the range of 61.98 +/- 0.43 to 273.43 +/- 0.96 mu M and 7-Deazaxanthine was taken as a standard inhibitor with IC50 = 38.68 +/- 4.42 mu M. Encouraged by these results, more analogues 1,2,4-triazole-3-mercaptocarboxylic acids 4a-4g were synthesized and their inhibitory potential against thymidine phosphorylase was evaluated. In this series, six analogues 4b-4g exhibited a good inhibitory potential in the range of 43.86 +/- 1.11-163.43 +/- 2.03 mu M. Angiogenic response of 1,2,4-triazole acid 4d was estimated using the chick chorionic allantoic membrane (CAM) assay. In the light of these findings, structure activity relationship and molecular docking studies of selected triazoles to determine the key binding interactions was discussed. Docking studies demonstrate that synthesized analogues interacted with active site residues of thymidine phosphorylase enzyme through pi-pi stacking, thiolate and hydrogen bonding interactions.