New 2-nitroimidazole-N-acylhydrazones, analogs of benznidazole, as anti-Trypanosoma cruzi agents.

Chagas disease is a neglected tropical parasitic disease caused by the protozoan Trypanosoma cruzi. Worldwide, an estimated 8 million people are infected with T. cruzi, causing more than 10,000 deaths per year. Currently, only two drugs, nifurtimox and benznidazole (BNZ), are approved for its treatment. However, both are ineffective during the chronic phase, show toxicity, and produce serious side effects. This work aimed to obtain and evaluate novel 2-nitroimidazole-N-acylhydrazone derivatives analogous to BNZ. The design of these compounds used the two important pharmacophoric subunits of the BNZ prototype, the 2-nitroimidazole nucleus and the benzene ring, and the bioisosterism among the amide group of BNZ and N-acylhydrazone. The 27 compounds were obtained by a three-step route in 57%-98% yields. The biological results demonstrated the potential of this new class of compounds, since eight compounds were potent and selective in the in vitro assay against T. cruzi amastigotes and trypomastigotes using a drug-susceptible strain of T. cruzi (Tulahuen) (IC50 = 4.3-6.25 µM) and proved to be highly selective with low cytotoxicity on L929 cells. The type I nitroreductase (TcNTR) assay suggests that the new compounds may act as substrates for this enzyme.

Synthesis and leishmanicidal evaluation of sulfanyl- and sulfonyl-tethered functionalized benzoate derivatives featuring a nitroimidazole moiety.

A series of new nitroimidazole-containing derivatives was synthesized by coupling of 2-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethylthio]ethanol with diversely substituted benzoic acids. Upon treatment with m-CPBA, 12 of these sulfanyl compounds were further oxidized to their sulfonyl analogs. All the 26 synthetic compounds were examined for in vitro activity against Leishmania (V.) braziliensis and Leishmania (L.) mexicana, and some of them displayed an efficient antileishmanial activity. Among the compounds tested, the catecholic derivative 2-{[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]sulfanyl}ethyl 3,4-dihydroxybenzoate (9a, LC50 = 13 and 11 µM) and the pyrogallolic derivative 2-{[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]sulfanyl}ethyl 3,4,5-trihydroxybenzoate (9b, LC50 = 4 and 1 µM) were the most active ones against the two Leishmania strains.

Novel nitroimidazole derivatives evaluated for their trypanocidal, cytotoxic, and genotoxic activities.

The current treatment of Chagas disease is based on the use of two drugs, nifurtimox (Nfx) and benznidazole (Bnz), both of which present limited efficacy in the chronic stage of the disease and toxic side effects. Thus, the discovery of novel compounds is urgently required. Herein, we report the successful synthesis of 4-nitroimidazole analogs of Bnz via nucleophilic aromatic substitution or cycloaddition reactions. The analogs were biologically evaluated, and compound 4 (4-cyclopropyl-1-(1-methyl-4-nitro-1H-imidazole-5-yl)-1H-1,2,3-triazole) was identified as the most potent against both the trypomastigote (IC50 = 5.4 µM) and amastigote (IC50 = 12.0 µM) forms of T. cruzi, showing activity in the same range as Bnz (IC50 = 8.8 and 8.7 µM, respectively). The cytotoxic and genotoxic activities of compounds 5, 4 and 11 were assessed. These three compounds were cytotoxic and genotoxic to RAW and HepG2 cells and mutagenic to Salmonella enterica strains. However, 4 exhibited toxic effects only at concentrations higher than those needed for trypanocidal activity. Molecular docking of 4 showed the importance of the size and π-π interactions between the nitroimidazole and the cofactor (flavin mononucleotide) of T.cruzi-nitroreductase (TcNTR). Moreover, the residues His503 and Tyr545 are relevant for binding to TcNTR. Our design strategy was capable of generating novel and active Bnz analogs.

Development and characterization of benznidazole nano- and microparticles: A new tool for pediatric treatment of Chagas disease?

Benznidazole (BNZ) is the drug of choice for the treatment of Chagas disease in many countries. However, its low water solubility produces low and/or variable oral bioavailability. Thus, the aim of this work was to formulate micro- and nanoparticles based on Eudragit® RS PO and Eudragit® RL PO as a convenient approach to increase the dissolution rate of BNZ. The microparticles were obtained by means of spray-drying process while the nanoparticles were prepared through the nanoprecipitation technique and further freeze-drying. The results indicated that nanoparticles were obtained in 86% yield while microparticles were obtained in 68% yield. In both cases, the encapsulation efficiency of particles was greater than 78% while drug loading capacity was nearly 24% w/w and 18% w/w, after spray-drying and freeze-drying procedures, respectively. Images of scanning electron microscopy showed that the particles obtained by spray-drying and freeze-drying were in the micrometer and nanometer scale, respectively. FT-IR spectra of BNZ-loaded particles obtained by both methods showed characteristic bands of BNZ confirming that part of drug remained on their surface. Thermal analysis revealed that the drug crystallinity after both methods decreased. Physical stability evaluation of the nanoparticles confirmed that Pluronic® F68 was suitable to keep the particles size in a range of 300 nm after 70 days storage at 4 ± 2 °C. In-vitro release studies showed increased dissolution rate of drug from the particles obtained by both methods respect to untreated BNZ. The kinetics of drug release in acid media followed the Higuchi kinetics indicating drug diffusion mechanism from particles.

Drug Discovery for Paediatric Chagas Disease.

Chagas disease is caused by the parasite Trypanosoma cruzi and is regularly found among particular people living in Central and South America. Paediatric Chagas disease occurs in 1-10% of infants of infected mothers. The major important point considered in the treatment of congenital Chagas disease focuses on killing the parasite in acute infection and managing signs and symptoms in later stages. Nowadays, two drugs benznidazole and nifurtimox are currently available in the market for the treatment of paediatric Chagas disease.

1,2,3-Triazole-based analogue of benznidazole displays remarkable activity against Trypanosoma cruzi.

The current treatment of Chagas disease is based on the use of two drugs, nifurtimox and benznidazole, which present limited efficacy in the chronic stage of the disease and toxic side effects. Although some progress has been made in the development of new drugs to treat this disease, the discovery of novel compounds is urgently required. In this work we report the synthesis and biological evaluation of 1,2,3-triazole-based analogues of benznidazole. A small series of 27 compounds was successfully synthesized via microwave-assisted copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) and ruthenium-catalyzed azide-alkyne cycloaddition (RuAAC) from N-benzyl-2-azidoacetamide (1) and a set of commercial terminal alkynes. Analogues 24 (IC50 40 µM) and 28 (IC50 50 µM) showed comparable activities to benznidazole (IC50 34 µM) against trypomastigote form and analogue 15 (IC50 7 µM) was found to be the most active. Regarding the cytotoxicity assessment of the series, most compounds were not cytotoxic. This work shows that the designed strategy is efficiently capable of generating novel benzindazole analogues and reveals one analogue is more active than benznidazole.

Synthesis, in vitro and in vivo characterization of two novel 68Ga-labelled 5-nitroimidazole derivatives as potential agents for imaging hypoxia.

INTRODUCTION: Hypoxia imaging is an important field in radiopharmaceutical research since hypoxic cells are very resistant to radiation treatment and diffusional limitations restrict the efficacy of chemotherapy. Gallium-68 is a widely used radionuclide for positron emission tomography (PET) due to the availability of the (68)Ge/(68)Ga-generator. With the aim to develop new potential [(68)Ga]-radiopharmaceuticals for imaging hypoxia, we have synthesized and evaluated two novel (68)Ga-labelled 5-nitroimidazole derivatives. METHODS: Two 5-nitroimidazole derivatives, and were synthesized. Preparation of [(68)Ga]complexes [(68)Ga]-Nit1 and [(68)Ga]-Nit2 was performed at pH 4.5 and 95 °C during 15 minutes and radiochemical purity (RP) was evaluated by reverse phase HPLC. Stability, lipophilicity and plasma protein binding were studied. Biological behaviour in HCT-15 cells both in normoxia and hypoxia has been assessed. Biodistribution in animals bearing induced 3LL Lewis murine lung carcinoma was studied. Comparison with [(18)F]FMISO is also presented. RESULTS: Nit1 and Nit2 have been successfully synthesized. Labelling in high radiochemical purity was achieved for both ligands. Complexes are stable in labelling milieu for at least four hours and in human plasma or in the presence of an excess of DTPA for at least two hours. Both compounds showed high uptake in hypoxic cells in vitro and a very favourable biodistribution profile in mice bearing induced tumours. Results are comparable to those obtained for [(18)F]FMISO. CONCLUSIONS: Selective uptake and retention in tumour together with favourable tumour/muscle ratio make these compounds promising candidates for further evaluation as potential hypoxia imaging agents.

New potent 5-nitroindazole derivatives as inhibitors of Trypanosoma cruzi growth: synthesis, biological evaluation, and mechanism of action studies.

New 5-nitroindazole derivatives were developed and their antichagasic properties studied. Eight compounds (14-18, 20, 26 and 28) displayed remarkable in vitro activities against Trypanosoma cruzi (T. cruzi). Its unspecific cytotoxicity against macrophages was evaluated being not toxic at a concentration at least twice that of T. cruzi IC(50), for some derivatives. The electrochemical studies, parasite respiration studies and ESR experiment showed that 5-nitroindazole derivatives not be able to yield a redox cycling with molecular oxygen such as occurs with nifurtimox (Nfx). The study on the mechanism of action proves to be related to the production of reduced species of the nitro moiety similar to that observed with benznidazole.

Novel nitroimidazoles with trypanocidal and cell growth inhibition activities.

Chagas' disease, caused by the protozoan parasite Trypanosoma cruzi, affects 18 million people in Latin America and is an important cause of heart disease. Although transmission has been reduced, an effective therapy for the infected population is lacking. New nitroimidazoles were designed and synthesized aimed at the development of a trypanocidal drug. The coupling of nitroimidazoles with heterocyclic N-trifluoromethyltriazolyl and pyrazolyl groups, 5-[N-(3-(5-trifluoromethyl)-1H-1,2,4-triazolyl)]amino-1-methyl-4-nitroimidazole (compound 4) and 5-N-(1-pyrazolyl)-1-methyl-4-nitroimidazole (compound 5). The in vitro trypanocidal effects of compounds 4 and 5 were evaluated. The results demonstrated that compound 5 was the most active compound, killing about 100% and 64% of the parasites in 0.3 mg/ml and 0.003 mg/ml concentrations, respectively. Interestingly, compound 4 also inhibited myeloma cell growth in a dose-dependent manner.

[Synthesis of 1-substituted nitroimidazoles and its evaluation as radiosensitizing agents]. / Síntesis de nitroimidazoles 1-sustituidos y su evaluación como radiosensibilizantes.

The synthesis of various substituted nitroimidazoles with lipophilic and hydrophilic side chains as potential radiosensitizing agents is described. The starting material employed was 4(5)-nitroimidazole, which was alkylated via the sodium salt with various chloro-methylated, substituted alcohols and esters, in order to obtain analogues of misonidazole, metronidazole and desmethylmisonidazole of known radiosensitizing and bactericidal activity. Some final products were assayed for their radiosensitizing properties giving negative results under the testing conditions used.

Sintesis de nitroimidazoles 1-sustituidos y su evaluación como radiosensibilizantes / Synthesis of 1-substituted nitroimidazoles and its evaluation as radiosensitizing agents

Se describe la sístesis de varios nitroimidazoles sustituídos con cadenas lipofílicas e hidrofílicas como posibles agentes radiosensibilizantes. El material de partida empleado fue el 4(5)-nitroimidazol, el cual fue alquilado vía su sal sódica, con cadenas clorometiladas provenientes de ésteres o alcoholes, de manera de obtener análogos estructurales de compuestos de reconocida actividad rediosensibilizantes y bactericida tales como el misonidazol, metronidazol y desmetilmisonidazol. Algunos productos de esta sístesis fueron sometidos a pruebas de radiosensibilización, dando resultados negativos, bajo las condiciones ensayadas