3-Nitro-1H-1,2,4-triazole-based amides with a linear, rigid core and 3-nitrotriazole-based fluconazole analogs were synthesized as dual functioning antitrypanosomal agents. Such compounds are excellent substrates for type I nitroreductase (NTR) located in the mitochondrion of trypanosomatids and, at the same time, act as inhibitors of the sterol 14α-demethylase (T. cruzi CYP51) enzyme. Because combination treatments against parasites are often superior to monotherapy, we believe that this emerging class of bifunctional compounds may introduce a new generation of antitrypanosomal drugs. In the present work, the synthesis and in vitro and in vivo evaluation of such compounds is discussed.

Chagas disease, a neglected tropical disease caused by infection with the protozoan parasite Trypanosoma cruzi, is a potentially life-threatening illness that affects 5-8 million people in Latin America, and more than 10 million people worldwide. It is characterized by an acute phase, which is partly resolved by the immune system, but then develops as a chronic disease without an effective treatment. There is an urgent need for new antiprotozoal agents, as the current standard therapeutic options based on benznidazole and nifurtimox are characterized by limited efficacy, toxicity, and frequent failures in treatment. In vitro and in vivo assays were used to identify some new low-cost 5-nitroindazoles as a potential antichagasic therapeutic alternative. Compound 16 (3-benzyloxy-5-nitro-1-vinyl-1H-indazole) showed improved efficiency and lower toxicity than benznidazole in both in vitro and in vivo experiments, and its trypanocidal activity seems to be related to its effect at the mitochondrial level. Therefore, compound 16 is a promising candidate for the development of a new anti-Chagas agent, and further preclinical evaluation should be considered.

In trypanosomatids, redox homeostasis is centered on trypanothione (N(1),N(8)-bis(glutathionyl)spermidine, T(SH)2), a low molecular weight thiol that is distinctive for this taxonomic family and not present in the mammalian host. Thus, the study of the metabolism of T(SH)2 is interesting as a potential therapeutic target. In this review, we summarize the existing evidence about the metabolism of thiols in Trypanosoma cruzi, focused on those proteins that can be considered the best candidates for selective therapy. Herein, we examine the biosynthetic pathway of T(SH)2, identifying three key points that are susceptible to attack pharmacologically: the activity of the trypanothione reductase (TR), the function of glutamate-cysteine ligase (GCL) and polyamine transport in T. cruzi. TR has been widely studied and is a good example for the development of the medicinal chemistry of antichagasic compounds. Conversely, GCL and the polyamine uptake system are high flow points in the reductive metabolism of the parasite. However, very little is known at the molecular level about these two systems. Therefore, their potential as targets for drug development is discussed, and it is suggested that research should focus on the production of alternative drugs for Chagas' disease treatment.

For years, Chagas disease treatment has been limited to only two drugs of highly questionable and controversial use (Nifurtimox(®) and Benznidazole(®)). In the search of effective drugs, many efforts have been made, but only a few structures have emerged as actual candidates. Heading into this, the multitarget-directed approach appears as the best choice. In this framework, indazoles were shown to be potent Trypanosoma cruzi growth inhibitors, being able to lead both the formation of reactive oxygen species and the inhibition of trypanothione reductase. Herein, we discuss the main structural factors that rule the anti-T. cruzi properties of indazoles, and how they would be involved in the biological properties as well as in the action mechanisms, attempting to make parallels between the old paradigms and current evidences in order to outline what could be the next steps to follow in regard to the future drug design for Chagas disease treatment.