ABSTRACT
Chagas disease, caused by the protozoan parasite Trypanosoma cruzi, affects millions of people in the Americas and across the world, leading to considerable morbidity and mortality. Current treatment options, benznidazole (BNZ) and nifurtimox, offer limited efficacy and often lead to adverse side effects because of long treatment durations. Better treatment options are therefore urgently required. Here, we describe a pyrrolopyrimidine series, identified through phenotypic screening, that offers an opportunity to improve on current treatments. In vitro cell-based washout assays demonstrate that compounds in the series are incapable of killing all parasites; however, combining these pyrrolopyrimidines with a subefficacious dose of BNZ can clear all parasites in vitro after 5 days. These findings were replicated in a clinically predictive in vivo model of chronic Chagas disease, where 5 days of treatment with the combination was sufficient to prevent parasite relapse. Comprehensive mechanism of action studies, supported by ligand-structure modeling, show that compounds from this pyrrolopyrimidine series inhibit the Qi active site of T. cruzi cytochrome b, part of the cytochrome bc1 complex of the electron transport chain. Knowledge of the molecular target enabled a cascade of assays to be assembled to evaluate selectivity over the human cytochrome b homolog. As a result, a highly selective and efficacious lead compound was identified. The combination of our lead compound with BNZ rapidly clears T. cruzi parasites, both in vitro and in vivo, and shows great potential to overcome key issues associated with currently available treatments.
Subject(s)
Chagas Disease , Parasites , Trypanocidal Agents , Trypanosoma cruzi , Animals , Humans , Cytochromes b , Trypanocidal Agents/adverse effects , Chagas Disease/drug therapy , Chagas Disease/chemically induced , Chagas Disease/parasitologyABSTRACT
New drugs for visceral leishmaniasis that are safe, low cost, and adapted to the field are urgently required. Despite concerted efforts over the last several years, the number of new chemical entities that are suitable for clinical development for the treatment of Leishmania remains low. Here, we describe the discovery and preclinical development of DNDI-6174, an inhibitor of Leishmania cytochrome bc1 complex activity that originated from a phenotypically identified pyrrolopyrimidine series. This compound fulfills all target candidate profile criteria required for progression into preclinical development. In addition to good metabolic stability and pharmacokinetic properties, DNDI-6174 demonstrates potent in vitro activity against a variety of Leishmania species and can reduce parasite burden in animal models of infection, with the potential to approach sterile cure. No major flags were identified in preliminary safety studies, including an exploratory 14-day toxicology study in the rat. DNDI-6174 is a cytochrome bc1 complex inhibitor with acceptable development properties to enter preclinical development for visceral leishmaniasis.
Subject(s)
Leishmaniasis, Visceral , Leishmaniasis , Rats , Animals , Leishmaniasis, Visceral/drug therapy , Leishmaniasis, Visceral/parasitology , Disease Models, AnimalABSTRACT
Phenotypic screening of a 900 compound library of antitubercular nitroimidazole derivatives related to pretomanid against the protozoan parasite Trypanosoma cruzi (the causative agent for Chagas disease) identified several structurally diverse hits with an unknown mode of action. Following initial profiling, a first proof-of-concept in vivo study was undertaken, in which once daily oral dosing of a 7-substituted 2-nitroimidazooxazine analogue suppressed blood parasitemia to low or undetectable levels, although sterile cure was not achieved. Limited hit expansion studies alongside counter-screening of new compounds targeted at visceral leishmaniasis laid the foundation for a more in-depth assessment of the best leads, focusing on both drug-like attributes (solubility, metabolic stability and safety) and maximal killing of the parasite in a shorter timeframe. Comparative appraisal of one preferred lead (58) in a chronic infection mouse model, monitored by highly sensitive bioluminescence imaging, provided the first definitive evidence of (partial) curative efficacy with this promising nitroimidazooxazine class.
Subject(s)
Chagas Disease/drug therapy , Nitroimidazoles/chemistry , Nitroimidazoles/pharmacology , Trypanocidal Agents/chemistry , Trypanocidal Agents/pharmacology , Trypanosoma cruzi/drug effects , Animals , Drug Evaluation, Preclinical , Mice , Nitroimidazoles/therapeutic use , Trypanocidal Agents/therapeutic use , Trypanosoma cruzi/physiologyABSTRACT
Recent clinical trials investigating treatment of chronic indeterminate Chagas disease with two re-purposed azole anti-fungal drugs, posaconazole and ravuconazole, revealed their inferiority to the current standard-of-care benznidazole and highlighted the inadequacy of the existing pre-clinical testing paradigm for this disease. A very limited number of controlled clinical trials for Chagas disease have been conducted to date. The selection of these compounds for clinical evaluation relied heavily on pre-clinical data obtained from in vitro screens and animal studies. This chapter reviews the evolution of CYP51 as a target for Trypanosoma cruzi growth inhibition and also explores the impact of clinical trial data on contemporary Chagas disease drug discovery. Advances in pre-clinical profiling assays, the current compound landscape and progress towards the identification of new drug targets to re-invigorate research are reviewed.
Subject(s)
Chagas Disease/drug therapy , Drug Discovery , 14-alpha Demethylase Inhibitors/therapeutic use , Clinical Trials as Topic , Humans , Nitroimidazoles/therapeutic useABSTRACT
Chagas disease, caused by the protozoan parasite Trypanosoma cruzi (T. cruzi), is an increasing threat to global health. Available medicines were introduced over 40 years ago, have undesirable side effects, and give equivocal results of cure in the chronic stage of the disease. We report the development of two compounds, 6 and (S)-7, with PCR-confirmed curative activity in a mouse model of established T. cruzi infection after once daily oral dosing for 20 days at 20 mg/kg 6 and 10 mg/kg (S)-7. Compounds 6 and (S)-7 have potent in vitro activity, are noncytotoxic, show no adverse effects in vivo following repeat dosing, are prepared by a short synthetic route, and have druglike properties suitable for preclinical development.
Subject(s)
Chagas Disease/drug therapy , Pyrimidines/pharmacology , Trypanocidal Agents/pharmacology , Trypanosoma cruzi/drug effects , Animals , Chagas Disease/parasitology , Disease Models, Animal , Dose-Response Relationship, Drug , Male , Mice , Molecular Structure , Parasitic Sensitivity Tests , Pyrimidines/administration & dosage , Pyrimidines/chemistry , Structure-Activity Relationship , Trypanocidal Agents/administration & dosage , Trypanocidal Agents/chemistryABSTRACT
BACKGROUND: Inhibitors of Trypanosoma cruzi with novel mechanisms of action are urgently required to diversify the current clinical and preclinical pipelines. Increasing the number and diversity of hits available for assessment at the beginning of the discovery process will help to achieve this aim. RESULTS: We report the evaluation of multiple hits generated from a high-throughput screen to identify inhibitors of T. cruzi and from these studies the discovery of two novel series currently in lead optimization. Lead compounds from these series potently and selectively inhibit growth of T. cruzi in vitro and the most advanced compound is orally active in a subchronic mouse model of T. cruzi infection. CONCLUSION: High-throughput screening of novel compound collections has an important role to play in diversifying the trypanosomatid drug discovery portfolio. A new T. cruzi inhibitor series with good drug-like properties and promising in vivo efficacy has been identified through this process.
Subject(s)
Trypanocidal Agents/pharmacology , Trypanosoma cruzi/drug effects , Administration, Oral , Animals , Cell Line , Cell Survival/drug effects , Chagas Disease/drug therapy , Chagas Disease/mortality , Cytochrome P-450 CYP3A/metabolism , Cytochrome P-450 CYP3A Inhibitors , Disease Models, Animal , High-Throughput Screening Assays , Humans , Mice , Parasitic Sensitivity Tests , Rats , Structure-Activity Relationship , Survival Rate , Time Factors , Trypanocidal Agents/chemistry , Trypanocidal Agents/therapeutic useABSTRACT
Chagas disease, caused by the eukaryotic (protozoan) parasite Trypanosoma cruzi, is an alarming emerging global health problem with no clinical drugs available to treat the chronic stage. Azole inhibitors of sterol 14α-demethylase (CYP51) were proven effective against Chagas, and antifungal drugs posaconazole and ravuconazole have entered clinical trials in Spain, Bolivia, and Argentina. Here we present the x-ray structures of T. cruzi CYP51 in complexes with two alternative drug candidates, pyridine derivatives (S)-(4-chlorophenyl)-1-(4-(4-(trifluoromethyl)phenyl)-piperazin-1-yl)-2-(pyridin-3-yl)ethanone (UDO; Protein Data Bank code 3ZG2) and N-[4-(trifluoromethyl)phenyl]-N-[1-[5-(trifluoromethyl)-2-pyridyl]-4-piperi-dyl]pyridin-3-amine (UDD; Protein Data Bank code 3ZG3). These compounds have been developed by the Drugs for Neglected Diseases initiative (DNDi) and are highly promising antichagasic agents in both cellular and in vivo experiments. The binding parameters and inhibitory effects on sterol 14α-demethylase activity in reconstituted enzyme reactions confirmed UDO and UDD as potent and selective T. cruzi CYP51 inhibitors. Comparative analysis of the pyridine- and azole-bound CYP51 structures uncovered the features that make UDO and UDD T. cruzi CYP51-specific. The structures suggest that although a precise fit between the shape of the inhibitor molecules and T. cruzi CYP51 active site topology underlies their high inhibitory potency, a longer coordination bond between the catalytic heme iron and the pyridine nitrogen implies a weaker influence of pyridines on the iron reduction potential, which may be the basis for the observed selectivity of these compounds toward the target enzyme versus other cytochrome P450s, including human drug-metabolizing P450s. These findings may pave the way for the development of novel CYP51-targeted drugs with optimized metabolic properties that are very much needed for the treatment of human infections caused by eukaryotic microbial pathogens.
Subject(s)
14-alpha Demethylase Inhibitors/chemistry , Antiprotozoal Agents/chemistry , Chagas Disease/enzymology , Protozoan Proteins/antagonists & inhibitors , Protozoan Proteins/chemistry , Sterol 14-Demethylase/chemistry , Trypanosoma cruzi/enzymology , 14-alpha Demethylase Inhibitors/therapeutic use , Antiprotozoal Agents/therapeutic use , Chagas Disease/drug therapy , Chagas Disease/genetics , Crystallography, X-Ray , Humans , Protozoan Proteins/genetics , Protozoan Proteins/metabolism , Sterol 14-Demethylase/genetics , Sterol 14-Demethylase/metabolism , Thiazoles/chemistry , Triazoles/chemistry , Trypanosoma cruzi/geneticsABSTRACT
A scaffold hopping exercise undertaken to expand the structural diversity of the fenarimol series of anti-Trypanosoma cruzi (T. cruzi) compounds led to preparation of simple 1-[phenyl(pyridin-3-yl)methyl]piperazinyl analogues of fenarimol which were investigated for their ability to inhibit T. cruzi in vitro in a whole organism assay. A range of compounds bearing amide, sulfonamide, carbamate/carbonate and aryl moieties exhibited low nM activities and two analogues were further studied for in vivo efficacy in a mouse model of T. cruzi infection. One compound, the citrate salt of 37, was efficacious in a mouse model of acute T. cruzi infection after once daily oral dosing at 20, 50 and 100 mg/kg for 5 days.
Subject(s)
Chagas Disease/drug therapy , Piperazines/chemistry , Piperazines/therapeutic use , Trypanocidal Agents/chemistry , Trypanocidal Agents/therapeutic use , Trypanosoma cruzi/drug effects , Administration, Oral , Animals , Chagas Disease/parasitology , Drug Design , Humans , Mice , Piperazine , Piperazines/administration & dosage , Piperazines/pharmacology , Pyrimidines/administration & dosage , Pyrimidines/chemistry , Pyrimidines/pharmacology , Pyrimidines/therapeutic use , Structure-Activity Relationship , Trypanocidal Agents/administration & dosage , Trypanocidal Agents/pharmacologyABSTRACT
We report the discovery of nontoxic fungicide fenarimol (1) as an inhibitor of Trypanosoma cruzi ( T. cruzi ), the causative agent of Chagas disease, and the results of structure-activity investigations leading to potent analogues with low nM IC(50)s in a T. cruzi whole cell in vitro assay. Lead compounds suppressed blood parasitemia to virtually undetectable levels after once daily oral dosing in mouse models of T. cruzi infection. Compounds are chemically tractable, allowing rapid optimization of target biological activity and drug characteristics. Chemical and biological studies undertaken in the development of the fenarimol series toward the goal of delivering a new drug candidate for Chagas disease are reported.
Subject(s)
Chagas Disease/drug therapy , Pyrimidines/chemistry , Pyrimidines/pharmacology , Trypanocidal Agents/chemistry , Trypanocidal Agents/pharmacology , Trypanosoma cruzi/drug effects , Animals , Cell Line , Chagas Disease/metabolism , Chagas Disease/parasitology , Disease Models, Animal , Gas Chromatography-Mass Spectrometry , Inhibitory Concentration 50 , Male , Mice , Nuclear Magnetic Resonance, Biomolecular , Pyrimidines/chemical synthesis , Pyrimidines/pharmacokinetics , Rats , Rats, Sprague-Dawley , Structure-Activity Relationship , Trypanocidal Agents/chemical synthesis , Trypanocidal Agents/pharmacokineticsABSTRACT
PURPOSE OF REVIEW: Boron-based drugs represent a new class of molecules that have been found to exhibit attractive properties and activities against a number of protozoans causative of neglected tropical diseases. RECENT FINDINGS: This review highlights recent advances in discovery of potential treatments for human African trypanosomiasis, malaria and Chagas disease from a class of boron-containing drugs, the benzoxaboroles. SUMMARY: Research at several biotechnology companies, sponsored by product development partners (PDPs), has been successful in identifying a novel class of boron-based drugs, the benzoxaboroles, as potential treatments for neglected tropical diseases. This work was based, in part, on the earlier observation of antifungal, antibacterial and anti-inflammatory activities of the benzoxaboroles. The unique properties of boron, namely its ability to reversibly interact with biochemical targets through an empty p-orbital, are important to the success of these new drug candidates. Physicochemical and pharmacokinetic properties of the boron-based compounds are consistent with features required for oral absorption, metabolic stability and low toxicity - all important for progression of this class to clinical trials.
Subject(s)
Antiprotozoal Agents/therapeutic use , Boron Compounds/therapeutic use , Chagas Disease/drug therapy , Malaria/drug therapy , Trypanosomiasis, African/drug therapy , Antimalarials/therapeutic use , HumansABSTRACT
Directed metallation and sulfinylation yields sulfoxides which undergo ipso nucleophilic aromatic substitution with tertiary and secondary alkyllithiums, giving aromatic rings bearing alkyl groups generally incompatible with directed metallation methods and with regioselectivity complementary with classical Friedel-Crafts substitution.
Subject(s)
Sulfur/chemistry , Thiocarbamates/chemistry , Benzamides/chemistry , Molecular StructureABSTRACT
Potent and selective ligands of the alpha7 nicotinic acetylcholine receptor are required to understand the pharmacological effect of alpha7 activation. A common cross-reactivity occurs with serotonergic 5-HT3 receptors with which alpha7 receptors have a high sequence homology. We demonstrate that certain quinuclidine 3-biaryl carboxamides are high affinity alpha7 ligands with an excellent binding selectivity over 5-HT3 receptors.
Subject(s)
Amides/chemical synthesis , Quinuclidines/chemical synthesis , Receptors, Nicotinic/chemistry , Receptors, Serotonin, 5-HT3/chemistry , Amides/chemistry , Cross Reactions , Drug Delivery Systems , Humans , Ligands , Protein Binding , Quinuclidines/chemistry , Radioligand Assay , Structure-Activity Relationship , alpha7 Nicotinic Acetylcholine ReceptorABSTRACT
[reaction: see text] Stereoselective aminohydroxylation and dihydroxylation using osmium(VIII) oxidants enabled the short and efficient synthesis of the aminocyclitol core of hygromycin A. In addition to allowing the selective introduction of the heteroatoms N and O, the use of osmium (via an osmate ester) as a protecting group for a 1,2-glycol is also reported. This tactic allowed efficient differentiation of otherwise equivalent hydroxyl groups and allowed us to complete the synthesis in short order (14 steps) and excellent overall yield (12%).
Subject(s)
Cinnamates/chemical synthesis , Hygromycin B/analogs & derivatives , Inositol/chemical synthesis , Cinnamates/chemistry , Crystallography, X-Ray , Hygromycin B/chemical synthesis , Hygromycin B/chemistry , Inositol/chemistry , Molecular Structure , Stereoisomerism , Streptomyces/chemistryABSTRACT
[reaction: see text] The tethered aminohydroxylation (TA) of acyclic allylic carbamates has been achieved in a stereospecific and stereoselective manner. Unusually high levels of stereocontrol were observed in the oxidation of 1,1-disubstituted substrates.
ABSTRACT
Tertiary 1-naphthamides racemise much more slowly than their laterally lithiated derivatives, and the relative rates of racemisation and epimerisation of these derivatives indicate that the lithium-bearing stereogenic centre inverts via a "conducted tour" mechanism, in which the lithium cation is delivered from one face to the other by coordination to the rotating amide group.
ABSTRACT
A series of substituted naphthyl containing chiral [2.2.1] bicycloheptanes were prepared utilizing asymmetric Diels-Alder chemistry. This paper describes structure-activity relationships in this series. The N-methyl 2-naphthyl analogue (16d) and its des-methyl analogue (17d) are active triple re-uptake inhibitors both in vivo and in vitro.
Subject(s)
Antidepressive Agents/chemistry , Bridged Bicyclo Compounds/chemistry , Depression/drug therapy , Neurotransmitter Uptake Inhibitors/chemistry , Animals , Antidepressive Agents/metabolism , Antidepressive Agents/therapeutic use , Binding Sites/drug effects , Binding Sites/physiology , Bridged Bicyclo Compounds/metabolism , Bridged Bicyclo Compounds/therapeutic use , Depression/metabolism , Mice , Neurotransmitter Uptake Inhibitors/metabolism , Neurotransmitter Uptake Inhibitors/therapeutic use , Synaptosomes/drug effects , Synaptosomes/metabolismABSTRACT
The tethered aminohydroxylation of cyclic allylic carbamates is described using catalytic amounts of potassium osmate. The mechanism of reaction involves formation of an imido-osmium complex which adds intramolecularly to alkenes with complete control of both regio- and stereoselectivity: the formation of syn-aminodiol motifs is now straightforward using this chemistry. Proof of the mechanism was obtained with an X-ray crystal structure of an azaglycolate osmate ester intermediate.
ABSTRACT
5-Hydroxytryptamine 3 (5-HT(3)) and alpha 7 nicotinic receptors share high sequence homology and pharmacological cross-reactivity. An assessment of the potential role of alpha 7 receptors in many neurophysiological processes, and hence their therapeutic value, requires the development of selective alpha 7 receptor agonists. We used a recently reported selective alpha 7 receptor agonist, (R)-(-)-5'Phenylspiro[1-azabicyclo[2.2.2] octane-3,2'-(3'H)furo[2,3-b]pyridine (PSAB-OFP) and confirmed its activity on human recombinant alpha 7 receptors. However, PSAB-OFP also displayed high affinity binding to 5-HT(3) receptors. To assess the functional activity of PSAB-OFP on 5-HT(3) receptors we studied recombinant human 5-HT(3) receptors expressed in Xenopus oocytes, as well as native mouse 5-HT(3) receptors expressed in N1E-115 neuroblastoma cells, using whole-cell patch clamp and Ca(2+) imaging. Our results show that PSAB-OFP is an equipotent, partial agonist of both alpha 7 and 5-HT(3) receptors. We conclude that it will be necessary to identify the determinant of this overlapping pharmacology in order to develop more selective alpha 7 receptor ligands.