Synthesis and antiparasitic activity of new bis-arylimidamides: DB766 analogs modified in the terminal groups

Drugs in preclinical and early clinical development for the treatment of Chagas´s disease: the current status

INTRODUCTION

Chagas disease is spreading faster than expected in different countries, and little progress has been reported in the discovery of new drugs to combat Trypanosoma cruzi infection in humans. Recent clinical trials have ended with small hope. The pathophysiology of this neglected disease and the genetic diversity of parasites are exceptionally complex. The only two drugs available to treat patients are far from being safe, and their efficacy in the chronic phase is still unsatisfactory.

AREAS COVERED

This review offers a comprehensive examination and critical review of data reported in the last 10 years, and it is focused on findings of clinical trials and data acquired in vivo in preclinical studies.

EXPERT OPINION

The in vivo investigations classically in mice and dog models are also challenging and time-consuming to attest cure for infection. Poorly standardized protocols, availability of diagnosis methods and disease progression markers, the use of different T. cruzi strains with variable benznidazole sensitivities, and animals in different acute and chronic phases of infection contribute to it. More synchronized efforts between research groups in this field are required to put in evidence new promising substances, drug combinations, repurposing strategies, and new pharmaceutical formulations to impact the therapy.

Synthesis and Biophysical and Biological Studies of N-Phenylbenzamide Derivatives Targeting Kinetoplastid Parasites

The AT-rich mitochondrial DNA (kDNA) of trypanosomatid parasites is a target of DNA minor groove binders. We report the synthesis, antiprotozoal screening, and SAR studies of three series of analogues of the known antiprotozoal kDNA binder 2-((4-(4-((4,5-dihydro-1H-imidazol-3-ium-2-yl)amino)benzamido)phenyl)amino)-4,5-dihydro-1H-imidazol-3-ium (1a). Bis(2-aminoimidazolines) (1) and bis(2-aminobenzimidazoles) (2) showed micromolar range activity against Trypanosoma brucei, whereas bisarylimidamides (3) were submicromolar inhibitors of T. brucei, Trypanosoma cruzi, and Leishmania donovani. None of the compounds showed relevant activity against the urogenital, nonkinetoplastid parasite Trichomonas vaginalis. We show that series 1 and 3 bind strongly and selectively to the minor groove of AT DNA, whereas series 2 also binds by intercalation. The measured pKa indicated different ionization states at pH 7.4, which correlated with the DNA binding affinities (ΔTm) for series 2 and 3. Compound 3a, which was active and selective against the three parasites and displayed adequate metabolic stability, is a fine candidate for in vivo studies.

Structural improvement of new thiazolyl-isatin derivatives produces potent and selective trypanocidal and leishmanicidal compounds

Neglected diseases are a group of transmissible diseases that occur mostly in countries in tropical climates. Among this group, Chagas disease and leishmaniasis stand out, considered threats to global health. Treatment for these diseases is limited. Therefore, there is a need for new therapies against these diseases. In this sense, our proposal consisted of developing two series of compounds, using a molecular hybridization of the heterocyclic isatin and thiazole. The isatin and thiazole ring are important scaffold for several biological disorders, including antiparasitic ones. Herein, thiazolyl-isatin has been synthesized from respective thiosemicarbazone or phenyl-thiosemicarbazone, being some of these new thiazolyl-isatin toxic for trypomastigotes without affecting macrophages viability. From this series, compounds 2e (IC₅₀ = 4.43 μM), 2j (IC₅₀ = 2.05 μM), 2l (IC₅₀ = 4.12 μM) and 2m (1.72 μM) showed the best anti-T. cruzi activity for trypomastigote form presenting a selectivity index higher than Benznidazole (BZN). Compounds 2j, 2l and 2m were able to induce a significantly labelling compatible with necrosis in trypomastigotes. Analysis by scanning electron microscopy showed that T. cruzi trypomastigote cells treated with the compound 2m from IC₅₀ concentrations, promoted changes in the shape, flagella and surface of body causing of the parasite dead. Concerning leishmanicidal evaluation against L. amazonensis and L. infantum, compounds 2l (IC₅₀ = 7.36 and 7.97 μM, respectively) and 2m (6.17 and 6.04 μM, respectively) showed the best activity for promastigote form, besides showed a higher selectivity than Miltefosine. Thus, compounds 2l and 2m showed dual in vitro trypanosomicidal and leishmanicidal activities. A structural activity relationship study showed that thiazolyl-isatin derivatives from phenyl-thiosemicarbazone (2a-m) were, in general, more active than thiazolyl-isatin derivatives from thiosemicarbazone (1a-g). Crystallography studies revealed a different configuration between series 1a-g and 2a-m. The configuration and spatial arrangement divergent between the two sub-series could explain the improved biological activity profile of 2a-m sub-series.

Review on Experimental Treatment Strategies Against Trypanosoma cruzi

Chagas disease is a neglected tropical disease caused by the protozoan Trypanosoma cruzi. Currently, only nitroheterocyclic nifurtimox (NFX) and benznidazole (BNZ) are available for the treatment of Chagas disease, with limitations such as variable efficacy, long treatment regimens and toxicity. Different strategies have been used to discover new active molecules for the treatment of Chagas disease. Target-based and phenotypic screening led to thousands of compounds with anti-T. cruzi activity, notably the nitroheterocyclic compounds, fexinidazole and its metabolites. In addition, drug repurposing, drug combinations, re-dosing regimens and the development of new formulations have been evaluated. The CYP51 antifungal azoles, as posaconazole, ravuconazole and its prodrug fosravuconazole presented promising results in experimental Chagas disease. Drug combinations of nitroheterocyclic and azoles were able to induce cure in murine infection. New treatment schemes using BNZ showed efficacy in the experimental chronic stage, including against dormant forms of T. cruzi. And finally, sesquiterpene lactone formulated in nanocarriers displayed outstanding efficacy against different strains of T. cruzi, susceptible or resistant to BNZ, the reference drug. These pre-clinical results are encouraging and provide interesting evidence to improve the treatment of patients with Chagas disease.

An Overview of the Synthesis and Antimicrobial, Antiprotozoal, and Antitumor Activity of Thiazole and Bisthiazole Derivatives

Thiazole, a five-membered heteroaromatic ring, is an important scaffold of a large number of synthetic compounds. Its diverse pharmacological activity is reflected in many clinically approved thiazole-containing molecules, with an extensive range of biological activities, such as antibacterial, antifungal, antiviral, antihelmintic, antitumor, and anti-inflammatory effects. Due to its significance in the field of medicinal chemistry, numerous biologically active thiazole and bisthiazole derivatives have been reported in the scientific literature. The current review provides an overview of different methods for the synthesis of thiazole and bisthiazole derivatives and describes various compounds bearing a thiazole and bisthiazole moiety possessing antibacterial, antifungal, antiprotozoal, and antitumor activity, encouraging further research on the discovery of thiazole-containing drugs.

Thiazole, thio and semicarbazone derivatives against tropical infective diseases: Chagas disease, human African trypanosomiasis (HAT), leishmaniasis, and malaria

Thiazole, thiosemicarbazone and semicarbazone moieties are privileged scaffolds (acting as primary pharmacophores) in many compounds that are useful to treat several diseases, mainly tropical infectious diseases. In this review article, we critically analyzed the contribution of these scaffolds to medicinal chemistry in the last five years, focusing on tropical infectious diseases, such as Chagas disease, human African trypanosomiasis (HAT), leishmaniasis, and malaria. We also present perspectives for their use in drug design in order to contribute to the development of new drugs.

Novel Catechol Derivatives of Arylimidamides as Antileishmanial Agents

Two novel bis-arylimidamide derivatives with terminal catechol moieties (9a and 10a) and two parent compounds with terminal phenyl groups (DB613 and DB884) were synthesized as dihydrobromide salts (9b and 10b). The designed compounds were hybrid molecules consisting of a catechol functionality embedded in an arylimidamide moiety. All compounds were examined for in vitro antiparasitic activity upon promastigotes of Leishmania major and L. infantum as well as axenic amastigotes of L. major. It was shown that conversion of terminal phenyl groups into catechol moieties resulted in more than 10-fold improvement in potency, coupled with lower cytotoxicity against fibroblast cells, compared to the corresponding parent compounds. The furan-containing analog 9a exhibited the highest activity with submicromolar IC₅₀ values, ranging from 0.29 to 0.36 μm, which is comparable in efficacy to the reference drug amphotericin B (IC₅₀ 0.28 - 0.33 μm). The results justify further study of this class of compounds. It seems that the combination of catechol chelating groups with potent antiparasitic agents could improve the efficacy by presenting novel hybrid compounds.