Synthesis, in vitro and in vivo giardicidal activity of nitrothiazole-NSAID chimeras displaying broad antiprotozoal spectrum

Abstract We designed and synthesized five new 5-nitrothiazole-NSAID chimeras as analogues of nitazoxanide, using a DCC-activated amidation. Compounds 1 – 5 were tested in vitro against a panel of five protozoa: 2 amitochondriates ( Giardia intestinalis , Trichomonas vaginalis ) and 3 kinetoplastids ( Leishmania mexicana, Leishmania amazonensis and Trypanosoma cruzi ) . All chimeras showed broad spectrum and potent antiprotozoal activities, with IC 50 values ranging from the low micromolar to nanomolar order. Compounds 1 – 5 were even more active than metronidazole and nitazoxanide, two marketed first-line drugs against giardiasis. In particular, compound 4 (an indomethacin hybrid) was one of the most potent of the series, inhibiting G. intestinalis growth in vitro with an IC 50 of 0.145 μM. Compound 4 was 38-times more potent than metronidazole and 8-times more active than nitazoxanide. The in vivo giardicidal effect of 4 was evaluated in a CD-1 mouse model obtaining a median effective dose of 1.709 μg/kg (3.53 nmol/kg), a 321-fold and 1015-fold increase in effectiveness after intragastric administration over metronidazole and nitazoxanide, respectively. Compounds 1 and 3 (hybrids of ibuprofen and clofibric acid), showed potent giardicidal activities in the in vitro as well as in the in vivo assays after oral administration. Therefore, compounds 1 – 5 constitute promising drug candidates for further testing in experimental chemotherapy against giardiasis, trichomoniasis, leishmaniasis and even trypanosomiasis infections.