Discovery of Potent N-Ethylurea Pyrazole Derivatives as Dual Inhibitors of Trypanosoma brucei and Trypanosoma cruzi

Synthesis and Anti-Trypanosoma cruzi Activity of New Pyrazole-Thiadiazole Scaffolds

Chagas disease, a silent but widespread disease that mainly affects a socioeconomically vulnerable population, lacks innovative safe drug therapy. The available drugs, benznidazole and nifurtimox, are more than fifty years old, have limited efficacy, and carry harmful side effects, highlighting the need for new therapeutics. This study presents two new series of pyrazole-thiadiazole compounds evaluated for trypanocidal activity using cellular models predictive of efficacy. Derivatives 1c (2,4-diCl) and 2k (4-NO2) were the most active against intracellular amastigotes. Derivative 1c also showed activity against trypomastigotes, with the detachment of the flagellum from the parasite body being a predominant effect at the ultrastructural level. Analogs have favorable physicochemical parameters and are predicted to be orally available. Drug efficacy was also evaluated in 3D cardiac microtissue, an important target tissue of Trypanosoma cruzi, with derivative 2k showing potent antiparasitic activity and a significant reduction in parasite load. Although 2k potentially reduced parasite load in the washout assay, it did not prevent parasite recrudescence. Drug combination analysis revealed an additive profile, which may lead to favorable clinical outcomes. Our data demonstrate the antiparasitic activity of pyrazole-thiadiazole derivatives and support the development of these compounds using new optimization strategies.

Privileged small molecules against neglected tropical diseases: A perspective from structure activity relationships

Neglected tropical diseases (NTDs) comprise diverse infections with more incidence in tropical/sub-tropical areas. In spite of preventive and therapeutic achievements, NTDs are yet serious threats to the public health. Epidemiological reports of world health organization (WHO) indicate that more than 1.5 billion people are afflicted with at least one NTD type. Among NTDs, leishmaniasis, chagas disease (CD) and human African trypanosomiasis (HAT) result in substantial morbidity and death, particularly within impoverished countries. The statistical facts call for robust efforts to manage the NTDs. Currently, most of the anti-NTD drugs are engaged with drug resistance, lack of efficient vaccines, limited spectrum of pharmacological effect and adverse reactions. To circumvent the issue, numerous scientific efforts have been directed to the synthesis and pharmacological development of chemical compounds as anti-infectious agents. A survey of the anti-NTD agents reveals that the majority of them possess privileged nitrogen, sulfur and oxygen-based heterocyclic structures. In this review, recent achievements in anti-infective small molecules against parasitic NTDs are described, particularly from the SAR (Structure activity relationship) perspective. We also explore current advocating strategies to extend the scope of anti-NTD agents.

Hit-to-lead optimization of a 2-aminobenzimidazole series as new candidates for chagas disease

Chagas disease is a neglected tropical disease caused by Trypanosoma cruzi. Because current treatments present several limitations, including long duration, variable efficacy and serious side effects, there is an urgent need to explore new antitrypanosomal drugs. The present study describes the hit-to-lead optimization of a 2-aminobenzimidazole hit 1 identified through in vitro phenotypic screening of a chemical library against intracellular Trypanosoma cruzi amastigotes, which focused on optimizing potency, selectivity, microsomal stability and lipophilicity. Multiparametric Structure-Activity Relationships were investigated using a set of 277 derivatives. Although the physicochemical and biological properties of the initial hits were improved, a combination of low kinetic solubility and in vitro cytotoxicity against mammalian cells prevented progression of the best compounds to an efficacy study using a mouse model of Chagas disease.

Collaborative Virtual Screening Identifies a 2-Aryl-4-aminoquinazoline Series with Efficacy in an In Vivo Model of Trypanosoma cruzi Infection

Probing multiple proprietary pharmaceutical libraries in parallel via virtual screening allowed rapid expansion of the structure-activity relationship (SAR) around hit compounds with moderate efficacy against Trypanosoma cruzi, the causative agent of Chagas Disease. A potency-improving scaffold hop, followed by elaboration of the SAR via design guided by the output of the phenotypic virtual screening efforts, identified two promising hit compounds 54 and 85, which were profiled further in pharmacokinetic studies and in an in vivo model of T. cruzi infection. Compound 85 demonstrated clear reduction of parasitemia in the in vivo setting, confirming the interest in this series of 2-(pyridin-2-yl)quinazolines as potential anti-trypanosome treatments.

Hybrid-Compounds Against Trypanosomiases

Neglected tropical diseases (NTDs) are a global public health problem associated with approximately 20 conditions. Among these, Chagas disease (CD), caused by Trypanosoma cruzi, and human African trypanosomiasis (HAT), caused by T. brucei gambiense or T. brucei rhodesiense, affect mainly the populations of the countries from the American continent and sub- Saharan Africa. Pharmacological therapies used for such illnesses are not yet fully effective. In this context, the search for new therapeutic alternatives against these diseases becomes necessary. A drug design tool, recently recognized for its effectiveness in obtaining ligands capable of modulating multiple targets for complex diseases, concerns molecular hybridization. Therefore, this review aims to demonstrate the importance of applying molecular hybridization in facing the challenges of developing prototypes as candidates for the treatment of parasitic diseases. Therefore, studies involving different chemical classes that investigated and used hybrid compounds in recent years were compiled in this work, such as thiazolidinones, naphthoquinones, quinolines, and others. Finally, this review covers several applications of the exploration of molecular hybridization as a potent strategy in the development of molecules potentially active against trypanosomiases, in order to provide information that can help in designing new drugs with trypanocidal activity.

Cs2CO3 catalyzed direct aza-Michael addition of azoles to α,β-unsaturated malonates

A highly efficient method for the synthesis of azole derivatives via a direct aza-Michael addition of azoles to α,β-unsaturated malonates using Cs₂CO₃ as a catalyst, has been successfully developed. A series of azole derivatives have been obtained in up to 94% yield and the reaction could be amplified to gram scale in excellent yield in the presence of 10 mol% of Cs₂CO₃.

A highly efficient method for the synthesis of azole derivatives via a direct aza-Michael addition of azoles to α,β-unsaturated malonates has been successfully developed. A series of azole derivatives have been obtained in up to 94% yield.

Bioactivity of Novel Pyrazole-Thiazolines Scaffolds against Trypanosoma cruzi: Computational Approaches and 3D Spheroid Model on Drug Discovery for Chagas Disease

Chagas disease, a century-old disease that mainly affects the impoverished population in Latin America, causes high morbidity and mortality in endemic countries. The available drugs, benznidazole (Bz) and nifurtimox, have limited effectiveness and intense side effects. Drug repurposing, and the development of new chemical entities with potent activity against Trypanosoma cruzi, are a potential source of therapeutic options. The present study describes the biological activity of two new series of pyrazole-thiazoline derivatives, based on optimization of a hit system 5-aminopyrazole-imidazoline previously identified, using structure−activity relationship exploration, and computational and phenotype-based strategies. Promising candidates, 2c, 2e, and 2i derivatives, showed good oral bioavailability and ADMET properties, and low cytotoxicity (CC50 > 100 µM) besides potent activity against trypomastigotes (0.4−2.1 µM) compared to Bz (19.6 ± 2.3 µM). Among them, 2c also stands out, with greater potency against intracellular amastigotes (pIC50 = 5.85). The selected pyrazole-thiazoline derivatives showed good permeability and effectiveness in the 3D spheroids system, but did not sustain parasite clearance in a washout assay. The compounds’ mechanism of action is still unknown, since the treatment neither increased reactive oxygen species, nor reduced cysteine protease activity. This new scaffold will be targeted to optimize in order to enhance its biological activity to identify new drug candidates for Chagas disease therapy.

Identification of Leucinostatins from Ophiocordyceps sp. as Antiparasitic Agents against Trypanosoma cruzi

Safe and effective treatments for Chagas disease, a potentially fatal parasitic infection associated with cardiac and gastrointestinal pathology and caused by the kinetoplastid parasite Trypanosoma cruzi, have yet to be developed. Benznidazole and nifurtimox, which are currently the only available drugs against T. cruzi, are associated with severe adverse effects and questionable efficacy in the late stage of the disease. Natural products have proven to be a rich source of new chemotypes for other infectious agents. We utilized a microscopy-based high-throughput phenotypic screen to identify inhibitors of T. cruzi from a library of natural product samples obtained from fungi procured through a Citizen Science Soil Collection Program (https://whatsinyourbackyard.org/) and the Great Lakes (USA) benthic environment. We identified five leucinostatins (A, B, F, NPDG C, and NPDG D) as potent inhibitors of the intracellular amastigote form of T. cruzi. Leucinostatin B also showed in vivo suppression of T. cruzi in a mouse model of Chagas disease. Given prior reports that leucinostatins A and B have antiparasitic activity against the related kinetoplastid Trypanosoma brucei, our findings suggest a potential cross-trypanocidal compound class and provide a platform for the further chemical derivatization of a potent chemical scaffold against T. cruzi.

Thermodynamic Understanding of an Aza-Michael Reaction Enables Five-Step Synthesis of the Potent Integrin Inhibitor MK-0429

We describe a general strategy for the aza-Michael addition of nucleophilic heterocycles into β-substituted acrylates using potassium tert-butoxide as catalyst. Demonstrating that the reaction is under thermodynamic control underpins optimization efforts and enables rapid exploration of the substrate scope, with yields ranging from 55% to 94%. We further leverage these lessons in a significantly shortened synthesis of MK-0429, a potent pan-integrin inhibitor previously taken into human clinical trials for the treatment of prostate cancer and osteoporosis.

Structural Optimization and Biological Activity of Pyrazole Derivatives: Virtual Computational Analysis, Recovery Assay and 3D Culture Model as Potential Predictive Tools of Effectiveness against Trypanosoma cruzi

Chagas disease, a chronic and silent disease caused by Trypanosoma cruzi, is currently a global public health problem. The treatment of this neglected disease relies on benznidazole and nifurtimox, two nitroheterocyclic drugs that show limited efficacy and severe side effects. The failure of potential drug candidates in Chagas disease clinical trials highlighted the urgent need to identify new effective chemical entities and more predictive tools to improve translational success in the drug development pipeline. In this study, we designed a small library of pyrazole derivatives (44 analogs) based on a hit compound, previously identified as a T. cruzi cysteine protease inhibitor. The in vitro phenotypic screening revealed compounds 3g, 3j, and 3m as promising candidates, with IC₅₀ values of 6.09 ± 0.52, 2.75 ± 0.62, and 3.58 ± 0.25 µM, respectively, against intracellular amastigotes. All pyrazole derivatives have good oral bioavailability prediction. The structure–activity relationship (SAR) analysis revealed increased potency of 1-aryl-1H-pyrazole-imidazoline derivatives with the Br, Cl, and methyl substituents in the para-position. The 3m compound stands out for its trypanocidal efficacy in 3D microtissue, which mimics tissue microarchitecture and physiology, and abolishment of parasite recrudescence in vitro. Our findings encourage the progression of the promising candidate for preclinical in vivo studies.

Autoimmunity to phosphatidylserine and anemia in African Trypanosome infections

Anemia caused by trypanosome infection is poorly understood. Autoimmunity during Trypanosoma brucei infection was proposed to have a role during anemia, but the mechanisms involved during this pathology have not been elucidated. In mouse models and human patients infected with malaria parasites, atypical B-cells promote anemia through the secretion of autoimmune anti-phosphatidylserine (anti-PS) antibodies that bind to uninfected erythrocytes and facilitate their clearance. Using mouse models of two trypanosome infections, Trypanosoma brucei and Trypanosoma cruzi, we assessed levels of autoantibodies and anemia. Our results indicate that acute T. brucei infection, but not T. cruzi, leads to early increased levels of plasma autoantibodies against different auto antigens tested (PS, DNA and erythrocyte lysate) and expansion of atypical B cells (ABCs) that secrete these autoantibodies. In vitro studies confirmed that a lysate of T. brucei, but not T. cruzi, could directly promote the expansion of these ABCs. PS exposure on erythrocyte plasma membrane seems to be an important contributor to anemia by delaying erythrocyte recovery since treatment with an agent that prevents binding to it (Annexin V) ameliorated anemia in T. brucei-infected mice. Analysis of the plasma of patients with human African trypanosomiasis (HAT) revealed high levels of anti-PS antibodies that correlated with anemia. Altogether these results suggest a relation between autoimmunity against PS and anemia in both mice and patients infected with T. brucei.

Discovery of 1,3,4,5-tetrasubstituted pyrazoles as anti-trypanosomatid agents: Identification of alterations in flagellar structure of L. amazonensis

Trypanosoma cruzi and Leishmania species are causative agents of Chagas disease and Leishmaniasis, respectively, known as Neglected Tropical Diseases. Up to now, the treatments are inadequate and based on old drugs. Thus, we report herein the discovery of 1,3,4,5-tetrasubstituted pyrazole derivatives that presented potent and selective inhibition against promastigote forms of L. amazonensis, and epimastigote forms of T. cruzi. The structure-activity relationship led to the identification of three compounds (2m, 2n and 2p) with an in vitro IC₅₀ of 7.4 µM (selective index - SI ≥ 133.0), 3.8 µM (SI in the range of 148.4 to 200.8), and 7.3 µM (SI in the range of 87.2 to 122.4) against L. amazonensis, respectively. Also, those compounds exhibited in vitro IC₅₀ of 9.7 µM (SI ≥ 101.5), 4.5 µM (SI in the range of 125.3 to 169.6) and 17.1 µM (SI in the range of 37.2 to 52.2) against T. cruzi, respectively. A preliminary study about the reaction mechanism in promastigotes showed that 2n caused an increase of the production of ROS and of lipid storage bodies. Furthermore, 2n induced abnormalities in the flagellum that may have an impact on the parasite motility.

Copper-catalyzed [3 + 2]-cycloaddition of α-halonitroalkenes with azomethine ylides: facile synthesis of multisubstituted pyrrolidines and pyrroles

An efficient route for the synthesis of multifunctionalized pyrrolidines based on copper-catalyzed diastereoselective [3 + 2]-cycloaddition of nitroalkenes with azomethine ylides was developed. Novel fluorinated heterocycles - β-fluoro-β-nitropyrrolidines - were accessed via this method. The products can be prepared in good to excellent yields and with high diastereoselectivity. Subsequent transformations of pyrrolidines including oxidative aromatization into fluorinated pyrrolines and medicinally attractive β-fluoro-NH-pyrroles as well as chemoselective reduction reactions were demonstrated. Application of the developed procedures for the non-fluorinated analogues was demonstrated to lead to various β-substituted pyrrole derivatives.

Discovery of imidazopyrrolopyridines derivatives as novel and selective inhibitors of JAK2

Herein, we describe the design, synthesis, and structure-activity relationships of a series of imidazopyrrolopyridines derivatives that selectively inhibit Janus kinase 2 (JAK2). These screening cascades revealed that 6k was a preferred compound, with IC₅₀ values of 10 nM for JAK2. Moreover, 6k was a selective JAK2 inhibitor with 19-fold, >30-fold and >30-fold selectivity over JAK1, JAK3 and TYK2 respectively. In cytokine-stimulated cell-based assays, 6k exhibited a higher JAK2 selectivity over JAK1 isoforms. Indeed, at a dose of 20 mg/kg compound 6k, pSTAT3 and pSTAT5 expression was reduced to levels comparable to those of control animals untreated with GM-CSF. Additionally, 6k showed a relatively good bioavailability (F = 38%), a suitable half-life time (T_1/2 = 1.9 h), a satisfactory metabolic stability, suggesting that 6k might be a promising inhibitor of JAK2 for further development research for the treatment of MPNs.