Molecular design, synthesis and biological evaluation of 1,4-dihydro-4-oxoquinoline ribonucleosides as TcGAPDH inhibitors with trypanocidal activity

Neq135 is the first low micromolar trypanosomatidae inhibitor acting against Trypanosoma cruzi glyceraldehyde 3-phosphate dehydrogenase (TcGAPDH). It binds to the NAD+ site, being selective in vitro toward the parasite. The 1,4-dihydro-4-oxoquinoline ribonucleoside, Neq135, is the first low micromolar trypanosomatidae inhibitor to show good ligand efficiency (0.28kcalmol−1atom−1) and good ligand lipophilicity efficiency (0.37kcalmol−1atom−1) when acting against Trypanosoma cruzi glyceraldehyde 3-phosphate dehydrogenase (TcGAPDH). This and other six ribonucleosides were synthesized using our in-house technology, and assayed against the GAPDH NAD+ site using isothermal titration calorimetry (ITC). Compound Neq135 had acceptable in vitro cytotoxicity, inhibited TcGAPDH with a Kiapp value of 16μM and killed the trypomastigote form of Trypanosoma cruzi Tulahuen strain with a concentration similar to that displayed by the control drug benznidazole. Neq135 is tenfold lower kinetic affinity against hGAPDH and does not kill Balb-c fibroblast nor spleen mouse cells. These results emphasize the possibility of integrating ligand- and target-based designs to uncover potent and selective TcGAPDH inhibitors that expands the opportunity for further medicinal chemistry endeavor towards NAD+ TcGAPDH site.