Potential Anti-trypanosomal Agents Research Articles

Discovery of 5-Phenylpyrazolopyrimidinone Analogs as Potent Antitrypanosomal Agents with In Vivo Efficacy.

Human African Trypanosomiasis (HAT), caused by Trypanosoma brucei, is one of the neglected tropical diseases with a continuing need for new medication. We here describe the discovery of 5-phenylpyrazolopyrimidinone analogs as a novel series of phenotypic antitrypanosomal agents. The most potent compound, 30 (NPD-2975), has an in vitro IC50 of 70 nM against T. b. brucei with no apparent toxicity against human MRC-5 lung fibroblasts. Showing good physicochemical properties, low toxicity potential, acceptable metabolic stability, and other pharmacokinetic features, 30 was further evaluated in an acute mouse model of T. b. brucei infection. After oral dosing at 50 mg/kg twice per day for five consecutive days, all infected mice were cured. Given its good drug-like properties and high in vivo antitrypanosomal potential, the 5-phenylpyrazolopyrimidinone analog 30 represents a promising lead for future drug development to treat HAT.

Exploring the Antiplasmodial 2-Aminopyridines as Potential Antitrypanosomal Agents.

Recently we reported the results of a screen of the Pathogen Box in which we identified 4-(2-amino-5-(4-(methylsulfonyl) phenyl) pyridin-3-yl)-2-methoxyphenol (MMV010576, 1) as our priority antitrypanosomal hit. This compound had previously been identified as a potent and selective antiplasmodial agent, where a focused optimization campaign, resulted in a medium-sized library of compounds, with favorable drug-like properties, one of which (MMV048, 2, 5-(4-(methylsulfonyl)phenyl)-6'-(trifluoromethyl)-[3,3'-bipyridin]-2-amine) is currently undergoing clinical trials for malaria. Accordingly, we investigated this library, in order to elucidate structural activity relationship details of this class of compounds as inhibitors of Trypanosoma brucei. Our study has identified several structural features important for antitrypanosomal activity, which are distinct from those required for antiplasmodial activity. Results from this study can be exploited to develop potent antitrypanosomal agents.

The Synthesis of Waltherione F and Its Analogues with Modifications at the 2- and 3-Positions as Potential Antitrypanosomal Agents.

Chagas disease also know as American Trypanosomiasis (AT) is a tropical parasitic disease endemic in South America, is caused by Trypanosoma cruzi, which is transmitted by the blood-sucking insect vectors called triatomine bugs. Quinoline alkaloids from the root extract of Waltheria indica are known to possess antitrypanosomal activity. Waltherione F, one of those alkaloids, was synthesised in 5 steps in 11 % overall yield. We report here the first X-ray crystallographic confirmation of the structure of Waltherione F 3. A key step in the sequence utilised the Conrad-Limpach synthesis for the formation of the quinolin-4(1H)-one ring system. Our synthetic strategy was designed to enable the modification of the 2- and 3-positions of the scaffold, allowing the generation of a diverse library of analogues to support our on-going medicinal chemistry program that is looking for new agents to tackle this devastating disease.

Quinoxaline derivatives as potential antitrypanosomal and antileishmanial agents

Continuous efforts have been made to discover new drugs for the treatment of Chagas’ disease, human African trypanosomiasis, and leishmaniasis. We have previously reported the synthesis and antileishmanial and antitrypanosomal (Y strain) properties of 2,3-disubstituted quinoxalines. Considering their promising antiparasitic potential, the present study was conducted to expand our search and take advantage of high-throughput assays to investigate the effects of quinoxaline derivatives against Leishmania donovani, Trypanosoma brucei, and Trypanosoma cruzi (Tulahuen strain). These compounds were active against the kinetoplastid parasites that were evaluated. The 2-chloro-3-methylsulfoxylsulfonyl and 2-chloro-3-methylsulfinyl quinoxalines were the most potent, and some of these derivatives were even more active than the reference drugs. Although the 2,3-diaryl-substituted quinoxalines were not active against all of the parasites, they were active against T. brucei and intracellular amastigotes of T. cruzi, without interfering with mammalian cell viability. These compounds presented encouraging results that will guide our future studies on in vivo bioassays towards the mode of action.

СИНТЕЗ ТА ДОСЛІДЖЕННЯ АНТИТРИПАНОСОМНОЇ АКТИВНОСТІ НОВИХ 5-ІЛІДЕН-2-(1,3,4-ТІАДІАЗОЛ-2-ІЛ)ІМІНОТІАЗОЛІДИН-4-ОНІВ

Мета роботи. На основі реакцій гетероциклізації та Кньовенагеля здійснити синтез нових тіадіазоло-2-імінотіазолідин-4-онів та їх 5-ариліденпохідних для скринінгу антитрипаносомної активності.Матеріали і методи. Органічний синтез, спектроскопія ЯМР, елементний аналіз, фармакологічний скринінг.Результати й обговорення. Циклізацією N-(1,3,4-тіадіазол-2-іл)заміщених 2-хлороацетамідів під дією амонію тіоціанату в середовищі ацетону синтезовано серію нових похідних 2-імінотіазолідин-4-ону. Наявність метиленактивної групи в положенні 5 тіазолідинового циклу отриманих 2-(1,3,4-тіадіазол-2-іл)імінотіазолідин-4-онів дозволила провести їх подальшу модифікацію в умовах реакції Кньовенагеля з різноманітними арил(гетерил)карбальдегідами, ізатином або похідними коричного альдегіду з утворенням серій відповідних 5-арил(гетерил)іліден- та 5-ізатин(3-фенілпропен)іліденпохідних як потенційних антитрипаносомних агентів. Структуру синтезованих сполук підтверджено елементним аналізом та спектроскопією ПМР.Висновки. Результати скринінгу антитрипаносомної активності in vitro синтезованих сполук на штамі Trypanosoma brucei gambiense (TBG) дозволили ідентифікувати чотири високоактивні сполуки, які зі значеннями IC50 в межах 7,3-12,8 мкМ володіли суттєвим трипаноцидним ефектом.

Lipophilic conformationally constrained spiro carbocyclic 2,6-diketopiperazine-1-acetohydroxamic acid analogues as trypanocidal and leishmanicidal agents: An extended SAR study.

We have previously described a number of lipophilic conformationally constrained spiro carbocyclic 2,6-diketopiperazine (2,6-DKP)-1-acetohydroxamic acids as potent antitrypanosomal agents. In this report, we extend the SAR analysis in this class of compounds with respect to in vitro growth inhibition of Trypanosoma and Leishmania parasites. Introduction of bulky hydrophobic substituents at the vicinal position of the basic nitrogen atom in the spiro carbocyclic 2,6-DKP ring system can provide analogues which are potently active against bloodstream form Trypanosomabrucei and exhibit significant activities toward Trypanosoma cruzi epimastogotes and Leishmania infantum promastigotes and intracellular amastigotes. In particular, compounds possessing a benzyl or 4-chlorobenzyl substituent were found to be the most active growth inhibitors, with activities in the low nanomolar and low micromolar ranges for T.brucei and L.infantum, respectively. The benzyl-substituted (S)-enantiomer was the most potent derivative against T.brucei (IC50 =6.8nm), T.cruzi (IC50 =0.21μm), and L.infantum promastigotes (IC50 =2.67μm) and intracellular amastigotes (IC50 =2.60μm). Moreover, the (R)-chiral benzyl-substituted derivative and its racemic counterpart displayed significant activities against L.donovani. Importantly, the active compounds show high selectivity in comparison with two mammalian cell lines.

Aryl- or heteroaryl-based hydrazinylphthalazine derivatives as new potential antitrypanosomal agents

A series of twenty phthalazinyl-hydrazones were synthesized and tested as potential anti-Trypanosoma cruzi agents. The phthalazines containing 5-nitroheteroaryl moiety 3l and 3m displayed an excellent in vitro antitrypanosomal profile, exhibiting low micromolar EC50 values against proliferative epimastigote of T. cruzi and minimal toxicity toward Vero cells. These derivatives were more potent than the reference drug benznidazole against the epimastigote stage of the parasite. Structure-property analysis indicates that the highly conjugated 5-nitroheteroaryl moiety connected to the phthalazin scaffold play an important role in the antichagasic activity of these phthalazines. The decrease on the mitochondrial dehydrogenase activity and significant ROS production found for the parasites treated with 3l and 3m suggest that both nitro-derivatives can act through an oxidative stress mechanism.

Ferrocenyl and cyrhetrenyl azines containing a 5-nitroheterocyclic moiety: Synthesis, structural characterization, electrochemistry and evaluation as anti-Trypanosoma cruzi agents

The synthesis of unsymmetrical ferrocenyl and cyrhetrenyl azines [(η5-C5H4)-CR=N-N=CH-2-C4H2X-5-NO2]M (M=Re(CO)3, Fe(η5-C5H5); R = H, CH3, X = O, S) has led to the development of new derivatives of 5-nitroheterocycles as potential anti-trypanosomal agents. The structures of compounds have been confirmed using conventional spectroscopic techniques (FT-IR, 1H and 13C NMR), mass spectrometry, including single-crystal X-ray diffraction analysis of compounds 2NT and 4NT. Based on the chemical shifts of the iminic carbons (C6, C7) and the reduction potential of the nitro group (E1/2 NO2), an extensive π-conjugation of the azine bridge (-C(R)=N-N=CH-) was observed along with a correlation between the opposing electronic effects of the cyrhetrenyl and ferrocenyl fragments. It was established that the existence of an electron-withdrawing group (cyrhetrene) could facilitate the generation of radical species (RNO2 to RNO2−) through the azine bridge. The organometallic azines were evaluated for anti-trypanosomal activity in vitro against the epimastigote form of the Dm28c strain of T. cruzi, yielding IC50 values in the low micromolar range.

Development of resazurin-based assay in 384-well format for high throughput whole cell screening of Trypanosoma brucei rhodesiense strain STIB 900 for the identification of potential anti-trypanosomal agents

To accelerate the discovery of novel leads for the treatment of Human African Trypanosomiasis (HAT), it is necessary to have a simple, robust and cost-effective assay to identify positive hits by high throughput whole cell screening. Most of the fluorescence assay was made in black plate however in this study the HTS assay developed in 384-well format using clear plate and black plate, for comparison. The HTS assay developed is simple, sensitive, reliable and reproducible in both types of plates. Assay robustness and reproducibility were determined under the optimized conditions in 384-well plate was well tolerated in the HTS assay, including percentage of coefficient of variation (% CV) of 4.68% and 4.74% in clear and black 384-well plate, signal-to-background ratio (S/B) of 12.75 in clear 384-well plate and 12.07 in black 384-well plate, Z′ factor of 0.79 and 0.82 in clear 384-well plate and black 384-well plate, respectively and final concentration of 0.30% dimethylsulfoxide (DMSO) in both types of plate. Drug sensitivity was found to be comparable to the reported anti-trypanosomal assay in 96-well format. The reproducibility and sensitivity of this assay make it compliant to automated liquid handler use in HTS applications.

Synthesis and evaluation of phenoxymethylbenzamide analogues as anti-trypanosomal agents

The synthesis of a compound library based on a high throughput screening hit led to the discovery of several potent anti-trypanosomal agents.

Novel nitro(triazole/imidazole)-based heteroarylamides/sulfonamides as potential antitrypanosomal agents

We have previously shown that 3-nitro-1H-1,2,4-triazole-based arylamides and arylsulfonamides demonstrate significant activity in vitro against Trypanosoma cruzi, the causative parasite of Chagas disease. More importantly, several such analogs displayed significant antichagasic activity in vivo, superior to that of benznidazole, the current clinical standard. We now report the synthesis and in vitro evaluation of a small series of novel nitro(triazole/imidazole)-based heteroarylamides/sulfonamides (including 3-nitrotriazole-, 2- and 4-nitroimidazole-based compounds) as potential antitrypanosomal agents. All nitrotriazoles displayed significant growth inhibitory properties against T. cruzi with the most potent generating IC50 values of <1 μM and up to >1400-fold selectivity toward the parasite. The 2-nitroimidazole-based derivatives were moderately active against T. cruzi and displayed selectivity <50, while the 4-nitroimidazoles were mostly inactive. Several 3-nitrotriazole-based analogs showed activity against Trypanosoma brucei rhodesiense but none of the tested compounds displayed activity toward Leishmania donovani. From the detailed SARs presented here, we identified the 3-nitrotriazole-based chlorinated thiophene/benzothiophene sulfonamides/amides as being the most active antichagasic compounds, displaying up to 14-fold higher potency against T. cruzi than the reference compound benznidazole.

Synthesis of pyrazoline–thiazolidinone hybrids with trypanocidal activity

A series of novel 4-thiazolidinone–pyrazoline conjugates have been synthesized and tested for anti-Trypanosoma brucei activity. Screening data allowed us to identify five thiazolidinone–pyrazoline hybrids, which possess promising trypanocidal activity, with IC50 ≤ 1.2 μM. The highest active thiazolidinone–pyrazoline conjugates 3c and 6b (IC50 values of 0.6 μM and 0.7 μM, respectively) were 6-times more potent antitrypanosomal agents than nifurtimox. In addition, these compounds, as well as 6d and 6e had selectivity index higher than 50, and were more selective than nifurtimox. SAR study included substituent variations at the pyrazoline moiety, modifications of N3 position of the thiazolidinone portion, elongation of the linker between the heterocycles, as well as rhodanine–isorhodanine isomerism. It was also shown that methyl or aryl substitution at the thiazolidinone N3-position is crucial for trypanocidal activity.

In silico prediction and experimental evaluation of furanoheliangolides as potent antitrypanosomal agents

In silico prediction and experimental evaluation of furanoheliangolides as potent antitrypanosomal agents

ChemInform Abstract: Synthesis and Antitrypanosomal Activity of New 6,6,7‐Trisubstituted Thiopyrano[2,3‐d][1,3]thiazoles.

AbstractA variety of new trisubstituted thiopyransthiazoles are synthesized via hetero‐Diels—Alder reactions of 5‐arylidene‐4‐thioxo‐2‐thiazolidinones with itaconic acid (II) or its imides, and screened as potential antitrypanosomal agents.

Atom based 3D-QSAR study of 1,4-benzodiazepine-2-ones as potent anti-trypanosomal agents and its validation

In the investigation, a robust pharmacophore model to investigate structure–activity relationship of 1,4-benzodiazepine-2-ones derivatives was developed for human African trypanosomiasis (HAT) using PHASE module of Schrodinger software. The pharmacophore model consists of five contours such as two aromatic rings (R), one hydrophobic hydrogen (H) and two hydrogen-bond acceptor (A) with discrete geometries. The generated pharmacophore model was used to derive a predictive atom-based three-dimensional quantitative structure–activity relationship (3D-QSAR) model for the studied data set. The obtained 3D-QSAR model has an excellent correlation coefficient value (R 2 = 0.97) along with good statistical significance as shown by high Fisher ratio (F = 216.80). The model also exhibits good predictive power confirmed by the high value of cross-validated correlation coefficient (Q 2 = 0.80). To confirm the validity of the model further calculation of the enrichment factor and percentage recovery studies were calculated, which confirm the validity of the model. The findings of the QSAR study provide a set of guidelines for designing compounds with better HAT inhibitory activity.

2D-QSAR study of 1,4-benzodiazepine-2-ones as potent anti-trypanosomal agents

2D-QSAR is one of the oldest methods of structure activity relationship analysis which provide many breakthroughs in the medicinal field. This method can provide a direct correlation between various physicochemical properties of a molecule with its structural characteristics. The correlations established by this method are based on the relative contribution of various descriptors. In the present study, this technique is utilized to develop a correlation equation between the anti-human African trypanosomiasis activity and the physicochemical parameters depicted by various descriptors utilized within the study. This series consists of 67 compounds with widespread range of activity between 0.78 and 3.13 μM. In addition, an effective correlation was obtained between SaasCE-index, Slogp, NitrogensCount, 0PathCount, Chi4pathCluster, CarbonsCount, and the biologic activity. These contributed descriptors illustrate that various physicochemical properties of the molecules responsible for the activities. The model suggests that the hydrophobicity has positive impact on the activity, while the presence of electronegative atom especially nitrogen and flexibility of the molecules also provide favorable effect on the activity.

Synthesis and antitrypanosomal activity of new 6,6,7-trisubstituted thiopyrano[2,3-d][1,3]thiazoles

А series of novel 6,6,7-trisubstituted thiopyrano[2,3-d][1,3]thiazoles-based molecules have been synthesized and evaluated as potential antitrypanosomal agents. The most active analogue 3b inhibited Trypanosoma brucei brucei and Trypanosoma brucei gambiense with an IC50 of 0.26 and 0.42μМ, respectively. They could be considered as potent hits for further antitrypanosomal drug discovery efforts.

Identification of selective tubulin inhibitors as potential anti-trypanosomal agents

The potency of a series of sulfonamide tubulin inhibitors against the growth of Trypanosoma brucei (T. brucei), as well as human cancer and primary fibroblast cells were evaluated with the aim of determining whether compounds that selectively inhibit parasite proliferation could be identified. Several compounds showed excellent selectivity against T. brucei growth, and have the potential to be used for the treatment of Human African trypanosomiasis. A T. brucei tubulin protein homology model was built based on the crystal structure of the bovine tubulin. The colchicine-binding domain, which is also the binding site of the tested sulfonamide tubulin inhibitors, showed clear differences between the tubulin structures and presumably explained the selectivity of the compounds.

Theoretical models for the antitrypanosomal activity of thiosemicarbazone derivatives

AbstractThiosemicarbazones are cruzain inhibitors which have been identified as potential antitrypanosomal agents. In this work, several molecular properties were calculated at the density functional theory (DFT)/B3LYP/6‐311G* level for a set of 44 thiosemicarbazones. Unsupervised and supervised pattern recognition techniques (hierarchical cluster analysis, principal component analysis, kth‐nearest neighbors, and soft independent modeling by class analogy) were used to obtain structure–activity relationship models, which are able to classify unknown compounds according to their activities. The chemometric analyses performed here revealed that 12 descriptors can be considered responsible for the discrimination between high and low activity compounds. Classification models were validated with an external test set, showing that predictive classifications were achieved with the selected variable set. The results obtained here are in good agreement with previous findings from the literature, suggesting that our models can be useful on further investigations on the molecular determinants for the antichagasic activity. © 2012 Wiley Periodicals, Inc.

Design and synthesis of new (E)-cinnamic N-acylhydrazones as potent antitrypanosomal agents

We report herein the synthesis and trypanocidal profile of new (E)-cinnamic N-acylhydrazones (NAHs) designed by exploiting molecular hybridization between the potent cruzain inhibitors (E)-1-(benzo[d][1,3]dioxol-5-yl)-3-(4-bromophenyl)prop-2-en-1-one and (E)-3-hydroxy-N′-((2-hydroxynaphthalen-1-yl)methylene)-7-methoxy-2-naphthohydrazide. These derivatives were evaluated against both amastigote and trypomastigote forms of Trypanosoma cruzi and lead us to identify two compounds that were approximately two times more active than the reference drug, benznidazole, and with good cytotoxic index. Although designed as cruzain inhibitors, the weak potency displayed by the best cinnamyl NAH derivatives indicated that another mechanism of action was likely responsible for their trypanocide action.