Synthesis, in vitro and in vivo giardicidal activity, and pharmacokinetic profile of a new nitazoxanide analog

Abstract 4-Nitro-N-(5-nitro-1,3-thiazol-2-yl)benzamide (1), a new nitazoxanide analog, was synthesized; its chemical structure was confirmed by 1H, 13C NMR, and HRMS. In this study, we evaluated the in vitro activity of compound 1 against Giardia lamblia trophozoites, as well as its in vivo giardicidal activity in a CD-1 mouse model. A pharmacokinetic study in Wistar rats evaluated compound 1 disposition after intravenous (IV) and oral administration of 3.3 and 150 mg/kg, respectively. Compound 1 inhibited G. lamblia growth in vitro with a median inhibitory concentration (IC50) of 0.78 ± 0.01 μM, and thus was more effective than metronidazole (IC50 = 5.36 ± 0.23 μM), the drug of choice against this parasite. An evaluation of cytotoxicity using VERO cells showed that compound 1 was less cytotoxic than metronidazole (CC50 = 685.98 vs. CC50 = 68 μM, respectively), with a favorable selectivity index (SI = 879). In vivo, we found that 97.2 % of parasite load was eliminated after intragastric administration of compound 1 (75 mg/kg). An analysis of the oral pharmacokinetic profile revealed a double peak of maximum concentration. Pharmacokinetic parameters indicated an absolute bioavailability approaching 33 %, a prolonged half-life, a large distribution volume, and slow clearance. This pharmacokinetic behavior of compound 1 makes it a promising candidate for the treatment of infections caused by both intestinal and systemic parasites.