The authors concluded that, of the compounds that inhibited the parasite, none showed selectivity toward CRK3, suggesting that this was not the primary target causing growth inhibition. Of these, 43 compounds were selective toward the Leishmania kinase over the human CDK. Of the 16 most potent compounds with IC 50 values ranging from 2. Eight of the most potent compounds against the parasite kinase were tested against L.
Additional azapurine derivatives were synthesized and screened as well. Several compounds showed modest inhibition of the L. There were 13 compounds selective toward the parasite kinase, and of these, all were thiazole derivatives. There were 11 of these compounds tested against L.
Interestingly, two compounds that were inactive against CRK3:CYC6 were also tested against the whole parasite cells, and these showed inhibition, further suggesting that the link between the Leishmania CRK3:CYC6 potency and the parasite inhibition may be tenuous. Cleghorn et al. Several compounds gave excellent inhibition of the parasite kinase in the nanomolar range and showed no activity against the human homologue, such as 70 and 71 in Figure The compounds showing activity and selectivity toward the Leishmania kinase were also screened against L.
In addition, the physicochemical properties of the compounds were measured, and many compounds had properties suitable for membrane penetration. Since the researchers thought that cellular penetration was not the reason for lack of parasite activity, it was concluded that the results may have been because the compounds were effluxed from the cell. Alternative explanations included the possibility that CRK3 binds to a cyclin other than CYC6 in the parasitic cells, or that the CRK3 is not essential due to bypass mechanisms.
Although Grant et al. An alternative method for identifying new kinase inhibitor chemotypes could be to identify classes of compounds that are known to be potent inhibitors of human homologues of essential kinases or families of kinases in parasites. Aurora kinases play an important role in cell division events such as mitotic spindle assembly, chromosomal separation, and cytokinesis. These kinases have been pursued as targets that have led to various inhibitors that are now in clinical trials for cancer.
Human aurora kinase inhibitors. Another analogue 76 was a 0. Other analogues showed good potency against L. SAR exploration of the hesperadin chemotype. Danusertib 77 Figure 24 , a phase II clinical candidate drug against solid tumors, and its predecessor analogue PHA 78 , were used to assess the SAR as its medicinal chemistry and structural biology profiles are well-known. Compounds 77 and 78 inhibited T. Driven by docking experiments using a homology model of TbAUK1, analogues of 77 were designed that maintained the tetrahedral geometry of the carbon center adjacent to the carbonyl group in the headgroup.
Analogues were tested against T.
The analogues synthesized were docked into the homology model of TbAUK1, and the docking scores correlated with cellular EC 50 values, suggesting that growth inhibition may indeed be mediated by TbAUK1 inhibition. However, confirmatory biochemical IC 50 determinations were precluded by difficulties in expression of catalytically active TbAUK1. As examples of lipid kinases, PI3Ks control growth and metabolism, and in humans, inhibitors of these enzymes have drawn interest as a target for anticancer and anti-inflammatory agents, and inhibitors of PI3K and mTOR selective, or cross-reactive have been shown to be promising agents for cancer therapy.
In the trypanosomatid parasites, there are at least 12 proteins belonging to the family of PI3K lipid kinases, some which are unique to the parasites. Some examples of these PI3Ks have been shown to be involved with trypanosomatid virulence and Golgi complex segregation, and the downstream TOR complexes are critical for trypanosomal cell growth.
From these inhibitors was identified NVP-BEZ 80 Figure 25 , an advanced drug candidate against solid tumors, which showed high potency against all three parasites. In addition, in vivo efficacy was observed in a mouse model of T. Though these analogues showed reduced potency against T.
Though trypanosomatid parasites do not express tyrosine kinases, 40 Tyr phosphorylation has been observed in the parasite. The nonspecific tyrosine kinase inhibitor tyrphostin inhibited the key cellular process of transferrin uptake, which translated to inhibition of cell growth. Both compounds have an improved selectivity profile over HepG2 cells, and 85 is fold more potent than lapatinib.
Importantly, this analogue showed excellent plasma exposure following oral dosing in mice, though brain drug levels were low. Instead, this compound blocked the duplication of kinetoplast and arrested cytokinesis without the disruption of the nucleus division on the parasite. This is clearly suggestive that 85 is inhibiting parasite growth via a mechanism different from lapatinib.
Importantly, cross-screening of these analogues against T. Research performed over the last 15 years has made great headway in elucidating the importance of kinases in cellular signaling processes in trypanosomatid parasites, enabled by the advances in cellular and molecular biology approaches that uncover the functions and essentiality of a specific kinase or families of kinases. The resultant expanded understanding of this gene family strengthens the conviction that kinases are important targets for new antiparasitic therapeutics, as in other species.
Trypanosomatid kinase medicinal chemistry is in its infancy compared to that of mammalian kinases, but the application of modern medicinal chemistry optimization approaches has quickly led to the identification of small drug-like molecules that inhibit kinase function and in some cases have effective antiparasitic activity.
However, issues of selectivity over host kinases are neither resolved nor predictable. The properties that are shared by human and parasite kinases that suggest that effective parasite kinase inhibitors can be discovered on the basis of prior knowledge also raise concern about potential cross-species selectivity. That said, it is currently unclear what characteristics of antiparasitic therapies need to be avoided because of potential effects on host kinase targets. The considerations of off-target effects are likely to differ for parasitic diseases, especially in the acute or life threatening phase, where dosing regimens may be of shorter duration, resulting in less concern with long-term toxicity.
In addition, the uptake, metabolism and retention of inhibitors by the parasite may either enhance or reduce efficacy during an infection. Parasite kinase inhibitor discovery has employed two complementary approaches: target-based, which focuses on selective inhibition of specific essential parasite kinases, and phenotype-based, which focuses on inhibition of cellular growth or other observable phenotypes that result from treatment with an investigational agent. On one hand, understanding mechanism-of-action may be useful, although a recent review of drug approvals indicated that the majority of approved drugs were discovered without initially knowing the target of action.
In some cases the mechanism of action was elucidated during or after the drug development process was complete. This is more the case in infectious diseases, where targets and pathways are not as well-understood as in the mammalian system. Thus, driving medicinal chemistry optimization in a cellular assay factors in cellular permeability and provides a physiologically relevant system for testing the inhibitor. These considerations can complicate, but certainly not prevent, medicinal chemistry optimization.
In a perfect situation, identification of trypanosome growth inhibitors would be followed by detailed mechanism of action studies, in order to learn what kinase inhibition profiles lead to successful antiparasitic drugs and to develop potent and selective probe molecules that can enable further research into parasite kinase function.
However, the resource poor environment of neglected tropical diseases may make this combination of experiments a luxury, although it may be the most cost-effective in the long run. While this review primarily discusses protein kinase inhibition as antitrypanosomatid approach, other nonprotein kinases e. As mentioned above, translation of understanding of kinase function in these parasites is still in its infancy compared to what is known about kinase function in humans.
We expect, in time, that a broader and deeper expansion of small molecule discovery efforts into kinases involved in lipid metabolism or glycolysis will emerge. In summary, great strides have been made toward understanding the utility of kinase inhibitors as antiparasitic agents, and progress appears to be accelerating, enabled and enhanced by new technologies and by redirecting existing technologies originally developed for use against mammalian kinases.
Time will tell whether compounds of clinical utility can be found that target trypanosomatid kinases and which have the needed selectivity and physicochemical properties to be efficacious. The authors declare no competing financial interest. Nature Publishing Group. A review. An assessment of the no. Now that we know the size of the human genome, it is interesting to consider just how many mol. We start from the position that we understand the properties that are required for a good drug, and therefore must be able to understand what makes a good drug target. Google Scholar There is no corresponding record for this reference.
El-Sayed, Najib M. Cecilia M. American Association for the Advancement of Science. A comparison of gene content and genome architecture of Trypanosoma brucei, Trypanosoma cruzi, and Leishmania major, three related pathogens with different life cycles and disease pathol. Many species-specific genes, esp. Retroelements, structural RNAs, and gene family expansion are often assocd.
Contrary to recent reports, the analyses reveal no evidence that these species are descended from an ancestor that contained a photosynthetic endosymbiont. Whole-genome sequencing of the protozoan pathogen Trypanosoma cruzi revealed that the diploid genome contains a predicted 22, proteins encoded by genes, of which 12, represent allelic pairs. Analyses of the T. Although the Tritryp lack several classes of signaling mols. Michael R. David; Fairlamb, Alan H. African trypanosomes cause human sleeping sickness and livestock trypanosomiasis in sub-Saharan Africa. The 11 megabase-sized chromosomes of Trypanosoma brucei were sequenced and analyzed.
Large subtelomeric arrays contain an archive of variant surface glycoprotein VSG genes used by the parasite to evade the mammalian immune system. Most VSG genes are pseudogenes, which may be used to generate expressed mosaic genes by ectopic recombination. Comparisons of the cytoskeleton and endocytic trafficking systems with those of humans and other eukaryotic organisms reveal major differences. A comparison of metabolic pathways encoded by the genomes of T. Horizontal transfer of genes of bacterial origin has contributed to some of the metabolic differences in these parasites, and a no.
In The Trypanosomiases ; Maudlin, I. Drug Resist. Verlinde, Christophe L. Harcourt Publishers Ltd. A review with refs. Glycolysis is perceived as a promising target for new drugs against parasitic trypanosomatid protozoa because this pathway plays an essential role in their ATP supply. Trypanosomatid glycolysis is unique in that it is compartmentalized, and many of its enzymes display unique structural and kinetic features. Structure- and catalytic mechanism-based approaches are applied to design compds. For some trypanosomatid enzymes, potent and selective inhibitors have already been developed that affect only the growth of cultured trypanosomatids, and not mammalian cells.
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Mary Ann Liebert, Inc. Significance: Parasitic diseases affect hundreds of millions of people worldwide and represent major health problems. Treatment is becoming extremely difficult due to the emergence of drug resistance, the absence of effective vaccines, and the spread of insecticide-resistant vectors. Thus, identification of affordable and readily available drugs against resistant parasites is of global demand.
Recent Advances: Susceptibility of many parasites to oxidative stress is a well-known phenomenon. Therefore, generation of reactive oxygen species ROS or inhibition of endogenous antioxidant enzymes would be a novel therapeutic approach to develop antiparasitic drugs. This article highlights the unique metabolic pathways along with redox enzymes of unicellular Plasmodium falciparum, Trypanosoma cruzi, Trypanosoma brucei, Leishmania donovani, Entamoeba histolytica, and Trichomonas vaginalis and multicellular parasites Schistosoma mansoni , which could be utilized to promote ROS-mediated toxicity.
Issues: Enzymes involved in various vital redox reactions could be potential targets for drug development. Future Directions: The identification of redox-active antiparasitic drugs along with their mode of action will help researchers around the world in designing novel drugs in the future. Redox Signal. American Society for Microbiology. Trypanosomatids are early-diverged, protistan parasites of which Trypanosoma brucei, Trypanosoma cruzi, and several species of Leishmania cause severe, often lethal diseases in humans.
To better combat these parasites, their mol. This process, in conjunction with polyadenylation, generates individual mRNAs from polycistronic precursors and creates functional mRNA by providing the cap structure. The reaction is a two-step transesterification process analogous to intron removal by cis splicing which, in trypanosomatids, is confined to very few pre-mRNAs. While trypanosomatids possess a full set of spliceosomal U snRNAs, only a few splicing factors were identified by std.
This review focuses on recent progress made in the characterization of the splicing factor repertoire in T. RNA recognition motifs, and by mining the genome database. In addn. FEMS Microbiol. Elsevier B. Purine salvage is an essential function for all obligate parasitic protozoa studied to date and most are also capable of efficient uptake of preformed pyrimidines. Much progress has been made in the identification and characterization of protozoan purine and pyrimidine transporters.
While the genes encoding protozoan or metazoan pyrimidine transporters have yet to be identified, numerous purine transporters have now been cloned. All protozoan purine transporter-encoding genes characterized to date have been of the Equilibrative Nucleoside Transporter family conserved in a great variety of eukaryote organisms. However, these protozoan transporters have been shown to be sufficiently different from mammalian transporters to mediate selective uptake of therapeutic agents. Recent studies are increasingly addressing the structure and substrate recognition mechanisms of these vital transport proteins.
Veterinary parasitology , , ISSN: To understand the importance of domestic pigs in the epidemiology of human trypanosomiasis, PCR was used to identify trypanosome populations in pigs from the Fontem sleeping sickness focus of Cameroon. The results from this study show that Trypanosoma vivax, T. The use of repeated DNA sequences detected T.
Such pigs can be possible reservoir hosts for T. Mixed infections were revealed in Furthermore, we observed that under natural conditions, No significant difference was observed between the percentage of T. PLoS Comput. John; Checchi, Francesco. Public Library of Science. Many infections can be transmitted between animals and humans. The epidemiol. Here, we present a method to identify transmission cycles in different combinations of species from field data.
We used this method to synthesize epidemiol. We estd. R0 of gambiense HAT in Bipindi and evaluated the potential for transmission in the absence of human cases. We found that under the assumption of random mixing between vectors and hosts, gambiense HAT could not be maintained in this focus without the contribution of animals. This result remains robust under extensive sensitivity anal. When using the distributions of species among habitats to est.
Stochastic simulation of the system confirmed that unless vectors moved between species very rarely, reintroduction would usually occur shortly after elimination of the infection from human populations. This suggests that elimination strategies may have to be reconsidered as targeting human cases alone would be insufficient for control, and reintroduction from animal reservoirs would remain a threat. Our approach is broadly applicable and could reveal animal reservoirs crit. Domestic pigs from the Arusha region of northern Tanzania were screened for trypanosomes using PCR-based methods to examine the role of pigs as a reservoir of human and animal trypanosomiasis.
A suite of PCR-based methods was used to identify the species and sub-species of trypanosomes including: Internally Transcribed Sequence to identify multiple species; species specific PCR to identify T. Nineteen pigs were infected with Trypanosoma brucei s. Infection, genetics and evolution : journal of molecular epidemiology and evolutionary genetics in infectious diseases , 6 2 , ISSN: In order to study the existence of a wild animal reservoir for Trypanosoma brucei gambiense in South Cameroon, blood was collected from wild animals in three human African trypanosomiasis foci and from a nonendemic control area.
Protein Phosphorylation in Parasites: Novel Targets for Antiparasitic Intervention
The wild animals sampled belonged to 36 different species pertaining to eight orders primates, artiodactyls, rodents, 54 pangolins, 53 carnivores, 11 saurians and crocodilians, and five hyraxes. Using specific primers, T. This infection rate was 5. Of the animals of the endemic zone, PCR revealed T. These hosts included two rodents, two artiodactyls, two carnivores and two primates. A decrease in the prevalence of T. The epidemiological implications of these findings remain to be determined with further investigations. BioMed Res. Trypanosoma evansi, the agent of "surra," is a salivarian trypanosome, originating from Africa.
It is thought to derive from Trypanosoma brucei by deletion of the maxicircle kinetoplastic DNA genetic material required for cyclical development in tsetse flies. It is mostly mechanically transmitted by tabanids and stomoxes, initially to camels, in sub-Saharan area. It can affect a very large range of domestic and wild hosts including camelids, equines, cattle, buffaloes, sheep, goats, pigs, dogs and other carnivores, deer, gazelles, and elephants. It found a new large range of wild and domestic hosts in Latin America, including reservoirs capybaras and biological vectors vampire bats.
Surra is a major disease in camels, equines, and dogs, in which it can often be fatal in the absence of treatment, and exhibits nonspecific clinical signs anaemia, loss of weight, abortion, and death , which are variable from one host and one place to another; however, its immunosuppressive effects interfering with intercurrent diseases or vaccination campaigns might be its most significant and questionable aspect. Whereas HPR assocn. Here we report that T. Two addnl. According to such a multifactorial defense mechanism, transgenic expression of T.
However, these transgenic parasites were killed in hypohaptoglobinemic serum, after high TLF-1 uptake in the absence of haptoglobin Hp that competes for Hb and receptor binding. PLoS Pathog. Most species of trypanosome, such as T. Understanding how T.
Previous work indicated that a failure to take up TLF-1 in T. Here, we have examd. Deletion of TgsGP in T. Reintroducing TgsGP into knockout parasite lines restored resistance. We conclude that TgsGP is essential for human serum resistance in T. Chagas disease is a chronic, systemic, parasitic infection caused by the protozoan Trypanosoma cruzi, and was discovered in In the past three decades, the control and management of Chagas disease has undergone several improvements. Large-scale vector control programmes and screening of blood donors have reduced disease incidence and prevalence.
Although more effective trypanocidal drugs are needed, treatment with benznidazole or nifurtimox is reasonably safe and effective, and is now recommended for a widened range of patients. Improved models for risk stratification are available, and certain guided treatments could halt or reverse disease progression. By contrast, some challenges remain: Chagas disease is becoming an emerging health problem in non-endemic areas because of growing population movements; early detection and treatment of asymptomatic individuals are underused; and the potential benefits of novel therapies eg, implantable cardioverter defibrillators need assessment in prospective randomised trials.
Allergy Immunol. International archives of allergy and immunology , 2 , ISSN: The major goal of studies on immunity to Trypanosoma cruzi is the understanding of immunological mechanisms involved in resistance to this protozoan as well as the pathogenesis of Chagas' disease. In contrast, during the chronic stage of the disease parasite-specific antibodies that fix complement and lyse the blood from trypomastigotes are thought to be the main effector molecules responsible for maintaining latent infection.
In both acute and chronic infection with T. The immunological mechanisms involved in the pathogenesis of Chagas' disease are much more controversial. Although many experiments suggest the involvement of autoimmunity in the pathogenesis of Chagas' disease, recent studies both in mice and humans indicate a positive association of tissue parasitism, inflammation and severity of pathology induced by T. Finally, T. The main clinical forms of Chagas disease acute, indeterminate and chronic cardiac present strong evidences for the participation of the immune system on pathogenesis.
Although parasite multiplication is evident during acute infection, the intense acute myocarditis of this phase exhibits clear ultrastructural signs of cell-mediated immune damage, inflicted to parasitized and non-parasitized myocardiocytes and to the endothelium of myocardial capillaries microangiopathy. Inflammation subsides almost completely when immunity decreases parasite load and suppressor factors modulate host reaction, but inflammation does not disappear when the disease enters the indeterminate phase.
Inflammation becomes mild and focal and undergoes cyclic changes leading to complete resolution. However, the process is maintained because the disappearance of old focal lesions is balanced by the upsurge of new ones. This equilibrium allows for prolonged host survival in the absence of symptoms or signs of disease. The chronic cardiac form is represented by a delayed-type, cell-mediated diffuse myocarditis, that probably ensues when the suppressive mechanisms, operative during the indeterminate phase, become defaulted. The mechanism responsible for the transition from the indeterminate to the cardiac form, is poorly understood.
Leishmania is a genus of protozoan parasites that are transmitted by the bite of phlebotomine sandflies and give rise to a range of diseases collectively known as leishmaniases that affect over million people worldwide. Cellular immune mechanisms have a major role in the control of infections with all Leishmania spp. However, as discussed in this Review, recent evidence suggests that each host-pathogen combination evokes different solns. Understanding the extent of this diversity will be increasingly important in ensuring the development of broadly applicable vaccines, drugs and immunotherapeutic interventions.
Cell Infect. Frontiers in cellular and infection microbiology , 2 , 99 ISSN:. Viannia , was detected several decades ago but its role in leishmanial virulence and metastasis was only recently described. The resultant inflammatory cascade has been shown to increase disease severity, parasite persistence, and perhaps even resistance to anti-leishmanial drugs.
Curiously, LRVs were found mostly in clinical isolates prone to infectious metastasis in both their human source and experimental animal model, suggesting an association between the viral hyperpathogen and metastatic complications such as mucocutaneous leishmaniasis MCL. MCL presents as chronic secondary lesions in the mucosa of the mouth and nose, debilitatingly inflamed and notoriously refractory to treatment. Immunologically, this outcome has many of the same hallmarks associated with the reaction to LRV: production of type 1 interferons, bias toward a chronic Th1 inflammatory state and an impaired ability of host cells to eliminate parasites through oxidative stress.
More intriguing, is that the risk of developing MCL is found almost exclusively in infections of the L. Viannia subtype, further indication that leishmanial metastasis is caused, at least in part, by a parasitic component. LRV present in this subgenus may contribute to the destructive inflammation of metastatic disease either by acting in concert with other intrinsic "metastatic factors" or by independently preying on host TLR3 hypersensitivity.
Because LRV amplifies parasite virulence, its presence may provide a unique target for diagnostic and clinical intervention of metastatic leishmaniasis. Taking examples from other members of the Totiviridae virus family, this paper reviews the benefits and costs of endosymbiosis, specifically for the maintenance of LRV infection in Leishmania parasites, which is often at the expense of its human host. Elsevier Ltd. Despite the many decades of use of most of the current trypanocides, we know little of their mode of action. This may in part be because most of these will act on multiple targets once inside the cell, and they derive their selective action on the parasite from selective accumulation by the pathogen.
Loss of this capacity for drug uptake by the trypanosome would thus be a major cause for drug resistance. We here discuss the use of current drugs against human and veterinary African trypanosomiasis, the prevalence, causes and mechanisms of drug resistance and new developments in trypanosomiasis therapy such as the introduction of nifurtimox and DB Human African trypanosomiasis HAT; sleeping sickness caused by Trypanosoma brucei gambiense is a fatal disease.
Current treatment options for patients with second-stage disease are toxic, ineffective, or impractical. We assessed the efficacy and safety of nifurtimox-eflornithine combination therapy NECT for second-stage disease compared with the std. Patients aged 15 years or older with confirmed second-stage T b gambiense infection were randomly assigned by computer-generated randomization sequence to receive i. This study is registered with, no. One patient from the eflornithine group absconded after receiving the first dose, without any type of assessment done, and was excluded from all analyses.
In the ITT population, In the PP population, Drug-related adverse events were frequent in both groups; 41 The efficacy of NECT is non-inferior to that of eflornithine monotherapy. Since this combination treatment also presents safety advantages, is easier to administer ie, infusion every 12 h for 7 days vs every 6 h for 14 days , and potentially protective against the emergence of resistant parasites, it is suitable for first-line use in HAT control programs.
PLoS Neglected Trop. Jacobs, Robert T. Background: Human African trypanosomiasis HAT is an important public health problem in sub-Saharan Africa, affecting hundreds of thousands of individuals. An urgent need exists for the discovery and development of new, safe, and effective drugs to treat HAT, as existing therapies suffer from poor safety profiles, difficult treatment regimens, limited effectiveness, and a high cost of goods.
We have discovered and optimized a novel class of small-mol. ADMET properties consistent with the compd. In a murine stage 2 study, SCYX is effective orally at doses as low as In vivo pharmacokinetic characterization of SCYX demonstrates that the compd.
Furthermore, SCYX readily distributes into cerebrospinal fluid to achieve therapeutically relevant concns. SCYX has been selected to enter preclin. Agents Chemother. Kaiser, Marcel; Bray, Michael A. Fexinidazole is a 5-nitroimidazole drug currently in clin. The compd. The parent mol. Pharmacokinetic data indicate that it is likely that the sulfoxide and sulfone metabolites provide most, if not all, of the in vivo killing activity.
Fexinidazole and its metabolites require up to 48 h exposure in order to induce maximal trypanocidal efficacy in vitro. The parent drug and its metabolites show no in vitro cross-reactivity in terms of trypanocidal activity with either themselves or other known trypanocidal drugs in use in humans. The in vitro and in vivo antitrypanosomal activities of fexinidazole and its two principal metabolites provide evidence that the compd. Lead discovery is currently a key bottleneck in the pipeline for much-needed novel drugs for tropical diseases such as malaria, tuberculosis, African sleeping sickness, leishmaniasis and Chagas disease.
Here, the authors discuss the different approaches to lead discovery for tropical diseases and emphasize a coordination strategy that involves highly integrated partnerships and networks between scientists in academic institutions and industry in both wealthy industrialized countries and disease-endemic countries. This strategy offers the promise of reducing the inherently high attrition rate of the early stages of discovery research, thereby increasing the chances of success and enhancing cost-effectiveness.
Trends Parasitol. Elsevier Science Ltd. Chagas disease, caused by Trypanosoma cruzi, is a major public health problem in Latin America, where it constitutes one of the largest parasitic disease burdens. Specific treatment of this condition has been controversial, but there is a growing consensus that elimination of T. Currently available chemotherapy, based on a nitrofuran nifurtimox and a nitroimidazole benznidazole , is unsatisfactory because of their limited efficacy in the prevalent chronic stage of the disease and their toxic side effects.
New approaches to specific chemotherapy are being advanced. Several of these compds. Other promising approaches include interference with trypanothione synthesis and redox metab. Chagas disease is caused by infection with the protozoan pathogen, Trypanosoma cruzi. The only approved therapeutics for treating Chagas disease are two nitroheterocyclic compds. Sterol demethylase inhibitors include azole antifungal drugs such as ketoconazole, fluconazole, itraconazole, and others.
The first reports of potent activity of azole antifungal drugs against Trypanosoma cruzi came out about 25 years ago. Since then, a sizeable literature has accumulated on this topic. Newer triazole compds. Small clin. However, there is good reason for optimism that newer compds. Data have been published demonstrating synergistic activity of azole drugs with various other compds.
In light of the near absence of adequate therapeutics for curing patients with chronic Chagas disease, addnl. Visceral leishmaniasis remains a public health problem worldwide. This illness was included by the World Health Organization in the list of neglected tropical diseases targeted for elimination by The widespread emergence of resistance to pentavalent antimonials in India where half cases occur globally and the unavailability of a vaccine in clinical use constitute major obstacles in achieving of this goal.
The last decade new antileishmanials became available, including the oral agent miltefosine. However, in poor endemic countries their wide use was curtailed because of the high costs, and also due to concerns of toxicity and emergence of resistance. Various mechanisms of antileishmanial resistance were identified recently in field isolates. Their elucidation will boost the design of new drugs and the molecular surveillance of resistance.
Combination regimens should be evaluated in large trials. Overall, the development of antileishmanials has been generally slow; new drugs are needed. In order to control visceral leishmaniasis worldwide, treatment advances should become affordable in the poorest countries, where they are needed most.
Nazrul; Mascie-Taylor, C. Nicholas; Berman, Jonathan; Arana, Byron. American Society of Tropical Medicine and Hygiene.
Protein phosphorylation in parasites: novel targets for antiparasitic intervention.
Miltefosine target dose of 2. We evaluated miltefosine in a phase IV trial of patients in Bangladesh. At the six-month final follow up, were cured. One hundred twenty-one patients were not assessable. Of 13 severe adverse events, 6 led to treatment discontinuation and 7 resulted in deaths, but only 1 death assocd. Oral miltefosine is an attractive alternative to i. University of Chicago Press. Development of high levels of resistance to various existing drugs necessitated the search for alternative orally administered drugs.
Hospital-based studies have shown that oral miltefosine is a highly effective treatment for VL both in adults and in children. An open, single-arm trial was designed to investigate the feasibility of treatment of VL patients with miltefosine in field conditions in 13 centers in Bihar. The phase 4 study was conducted among adult and pediatric VL patients.
Compliance was good, with Nine hundred and seventy-one This study supports the use of miltefosine in an outpatient setting in an area where VL is endemic. Assay Drug Dev. Smithson, David C. Herein, the optimization of a linked enzyme assay suitable for high-throughput screening of decarboxylases, a target family whose activity has historically been difficult to quantify, is described.
The approach uses a com. The assay is performed in a fully enclosed automated screening system under inert nitrogen atm. Receiver operating characteristic ROC anal.
American Chemical Society. Cruzain is the major cysteine protease of Trypanosoma cruzi, which is the causative agent of Chagas disease and is a promising target for the development of new chemotherapy. With the goal of developing potent nonpeptidic inhibitors of cruzain, the substrate activity screening SAS method was used to screen a library of protease substrates initially designed to target the homologous human protease cathepsin S.
Structure-based design was next used to further improve substrate cleavage efficiency by introducing addnl. The optimized substrates were then converted to inhibitors by the introduction of cysteine protease mechanism-based pharmacophores. Inhibitor 38 was detd. For these inhibitors, potency did not solely depend on leaving group pKa, with 2,3,5,6-tetrafluorophenoxymethyl ketone 54 identified as one of the most potent inhibitors with a second-order inactivation const.
This inhibitor completely eradicated the T. Ferreira, Rafaela S. Virtual and high-throughput screens HTS should have complementary strengths and weaknesses, but studies that prospectively and comprehensively compare them are rare. We undertook a parallel docking and HTS screen of compds. These fell into five chemotypes: two were prioritized by scoring among the top 0. Prioritizing mols. Gunatilleke, Shamila S. Although a major cause of morbidity and mortality due to heart failure, as well as inflicting a heavy economic burden in affected regions, Chagas Disease elicits scant notice from the pharmaceutical industry because of adverse economic incentives.
The discovery and development of new routes to chemotherapy for Chagas Disease is a clear priority. To diversify the therapeutic pipeline of anti-Chagasic drug candidates we exploited an approach that included directly probing the T. Two pools of hits partially overlapped. The top hit inhibited T. Cheminformatic anal. Surprisingly, strong similarity is suggested to glutaminyl-peptide cyclotransferase, which is unrelated to CYP51 by sequence or structure.
Lead compds. Sage Publications. The use of a high-throughput technique to perform a pilot screen for Leishmania major protein disulfide isomerase LmPDI inhibitors identification is reported. In eukaryotic cells, protein disulfide isomerase PDI plays a crucial role in protein folding by catalyzing the rearrangement of disulfide bonds in substrate proteins following their synthesis. LmPDI displays similar domain structure organization and functional properties to other PDI family members and is involved in Leishmania virulence.
The authors used a method based on the enzyme-catalyzed redn. The screen of a small library of compds. The authors further tested the cytotoxicity of these compds. Results show hexachlorophene and a mixt. Cleghorn, Laura A. New drugs are urgently needed for the treatment of tropical parasitic diseases such as leishmaniasis and human African trypanosomiasis HAT. Eight hit series were identified, of which four [3-acylaminoarylpyrazoles, 5-aminoarylpyrazolo[1,5-a]pyrimidines, 2-acylaminoaryl[1,2,4]triazolo[1,5-a]pyridines, and N- oxocyclohexenyl ureas] were followed up.
The optimization of these series using classical SAR studies afforded low-nanomolar CRK3 inhibitors with significant selectivity over the closely related human cyclin dependent kinase CDK2. Grant, Karen M. The CRK3 cyclin-dependent kinase of Leishmania has been shown by genetic manipulation of the parasite to be essential for proliferation. The authors present data which demonstrate that chem. A microtiter plate-based histone H1 kinase assay was developed to screen CRK3 against a chem.
Twenty-seven potent CRK3 inhibitors were discovered and screened against Leishmania donovani amastigotes in vitro. These compds. The paullones and staurosporine derivs. The most potent inhibitors of CRK3 compds. In culture, the indirubins caused growth arrest, a change in DNA content, and aberrant cell types, all consistent with the intracellular inhibition of a cyclin-dependent kinase and disruption of cell cycle control.
Thus, use of chem. Drug Des. Morgan, Rachel E. Tubulin is the proposed target for drugs against cancer and helminths and is also a validated target in kinetoplastid parasites. With the aim of identifying new lead compds. One compd. Another compd. This compd. Subsequent testing of analogs of 8 contained within the library identified two compds.
The more potent antitubulin agent also showed promising activity against cancer cell lines in vitro, with IC50 values ranging from 0. Elsevier Science Ireland Ltd. Eukaryotes modify numerous proteins, including small GTPases of the ras superfamily, with isoprenes as a mechanism for membrane attachment.
Inhibition of farnesylation of ras has been successfully exploited to control cell growth, with promise in the clinic for treatment of human tumors. Using an in vitro screen of mammalian farnesyltransferase inhibitors, we have identified manumycin A as potently active against growth of both bloodstream and procyclic forms of Trypanosoma brucei. Other structural classes of farnesyltransferase inhibitors were far less effective. Exposure of T. Manumycin A did not affect trypanosomal protein and DNA synthesis or cell cycle progression but altered incorporation of prenyl groups into several polypeptides indicating a specific effect on the prenylation without effect on other mevalonate pathway products, most importantly prenyl pyrophosphate levels.
Structural analogs of manumycin A contg. Furthermore, manumycin A also elicited mitochondrial alterations in mammalian cells indicating that the effect is not confined to lower eukaryotes. Manumycin A is well tolerated in vivo but failed to cure exptl. Elsevier Masson SAS. A whole organism high-throughput screen of approx. Herein we report a structure-activity relation SAR investigation around one of these hit classes, the 3- oxazolo[4,5-b]pyridinyl anilides. Sharp SAR is revealed, with our most active compd.
I exhibiting an IC50 of 91 nM against the human pathogenic strain T. For the most potent representatives, we show that soly. In the course of a larger screen of plant and fungal exts. They were tested for in vitro antitrypanosomal activities and cytotoxicity alongside the structurally related sesquiterpene lactones parthenolide 5 , zaluzanin D 6 , and eupatoriopicrin 7 , and had IC50s between 0.
Cytotoxic IC50s were from 1. Planta Med. Georg Thieme Verlag. In a medium throughput screen of plant and fungal exts. Subsequent isolation and structure elucidation yielded the known substances miltirone 1 , tanshinone II a 2 , 1,2 dihydrotanshinquinone 3 , methylenetanshinquinone 4 , 1-oxomiltirone 5 , hydroxymiltiodiol 6 , tanshinone I 7 , methyltanshinonate 8 , and cryptotanshinone 9. The IC50s of the compds. They ranged from 4.
IC50s against T. Tatipaka, Hari Babu; Gillespie, J. Robert; Chatterjee, Arnab K. A phenotypic screen of a compd. A total of analogs were prepd. I was orally bioavailable and displayed good plasma and brain exposure in mice. I cured mice infected with Trypanosoma brucei when dosed orally down to 2. Given its potent antiparasitic properties and its ease of synthesis, I represents a new lead for the development of drugs to treat human African trypanosomiasis. Vodnala, Suman K. New drugs for the treatment of human African trypanosomiasis are urgently needed.
Described compds. Specifically, 6- [6-fluoro-3,4-dihydro-2Hbenzopyranyl ]oxy -N- piperidinyl pyrazinamine CBK is trypanotoxic for T. Mice inoculated i. Thus, CBK and related analogs are promising leads for the development of novel treatments for human African trypanosomiasis. ACS Med. Dandapani, Sivaraman; Germain, Andrew R. After evaluating stereochem. The p-phenoxy benzyl group appended to the secondary amine could be replaced with halobenzyl groups without loss in potency.
The exocyclic primary alc. Most importantly, these compds. Analog 5 was nominated as the mol. Libraries Probe Prodn. Centers Network. Germain, Andrew R. We report the outcome of a high-throughput small-mol. Two compds. Future Med. Keenan, Martine; Alexander, Paul W. Andrew; Charman, Susan A. Future Science Ltd. Background: Inhibitors of Trypanosoma cruzi with novel mechanisms of action are urgently required to diversify the current clin.
Increasing the no. Results: We report the evaluation of multiple hits generated from a high-throughput screen to identify inhibitors of T. Conclusion: High-throughput screening of novel compd. A new T. Engel, Juan C. Chagas' disease, caused by infection with the parasite Trypanosoma cruzi, is the major cause of heart failure in Latin America.
Classic clin. To ameliorate disease, chemotherapy must eradicate the parasite. Current drugs are ineffective and toxic, and new therapy is a crit. To expedite drug screening for this neglected disease, we have developed and validated a cell-based, high-throughput assay that can be used with a variety of untransfected T.
Assay plates were automatically imaged and analyzed based on size differences between the DAPI 4',6-diamidinophenylindole -stained host cell nuclei and parasite kinetoplasts. A redn. The assay was used to screen a library of clin. The flexible assay design allows the use of various parasite strains, including clin. This high-throughput assay will have an important impact in antiparasitic drug discovery. Bell, Andrew S. Inhibition of N-myristoyltransferase has been validated pre-clin. In order to identify inhibitors of protozoan NMTs, we chose to screen a diverse subset of the Pfizer corporate collection against Plasmodium falciparum and Leishmania donovani NMTs.
Primary screening hits against either enzyme were tested for selectivity over both human NMT isoforms Hs1 and Hs2 and for broad-spectrum anti-protozoan activity against the NMT from Trypanosoma brucei. However, we did discover two novel series with selectivity for Plasmodium NMT over the other NMT orthologues in this study, and an addnl. We believe that release of results from this study into the public domain will accelerate the discovery of NMT inhibitors to treat malaria and leishmaniasis.
Osorio, Yaneth; Travi, Bruno L. Background: New drugs are needed to treat visceral leishmaniasis VL because the current therapies are toxic, expensive, and parasite resistance may weaken drug efficacy. We established a novel ex vivo splenic explant culture system from hamsters infected with luciferase-transfected Leishmania donovani to screen chem.
The assay showed excellent discrimination between pos. A duplicate screen of 4 chem. Eighty-four 2. The most frequently identified lead compds. Further in vivo evaluation and chem. Sharlow et al. Based on availability and chem. Benzothiazole cyanine compds.
PubChem and displayed potent activity against intracellular amastigotes, prompting a search for com. Pubchem the cyanine dye thiazole orange showed exceptionally potent activity against intracellular L. These protozoa possess complex life cycles that involve development in mammalian and insect hosts, and a tightly coordinated cell cycle ensures propagation of the highly polarized cells.
However, the ways in which the parasites respond to their environment and coordinate intracellular processes are poorly understood. As a part of an effort to understand parasite signaling functions, we report the results of a genome-wide analysis of protein kinases PKs of these three trypanosomatids. The representation of various groups of ePKs differs significantly as compared to humans: trypanosomatids lack receptor-linked tyrosine and tyrosine kinase-like kinases, although they do possess dual-specificity kinases.
A large number of unique ePKs show no strong affinity to any known group. The trypanosomatids possess few ePKs with predicted transmembrane domains, suggesting that receptor ePKs are rare. Accessory Pfam domains, which are frequently present in human ePKs, are uncommon in trypanosomatid ePKs. Whilst it was possible to place most of the trypanosomatid ePKs into the seven established groups using bioinformatic analyses, it has not been possible to ascribe function based solely on sequence similarity.
Hence the connection of stimuli to protein phosphorylation networks remains enigmatic. The presence of numerous PKs with significant sequence similarity to known drug targets, as well as a large number of unusual kinases that might represent novel targets, strongly argue for functional analysis of these molecules. Mottram, Jeremy C. Philomena; Brown, Kathryn G. The generation of homozygous null mutants for the crk1 cdc2-related kinase of Leishmania mexicana was attempted using targeted gene disruption. Promastigote mutants heterozygous for crk1 were readily isolated with a hyg-targeting fragment, but attempts to create null mutants by second-round transfections with a ble-targeting fragment yielded 2 classes of mutant, neither of which was null.
First, the transfected fragment formed an episome; second, the cloned transfectants contained wild-type crk1 alleles as well as hyg and ble integrations. DNA-content anal. Plasticity in chromosome no. These data support this theory and implicate crk1 as an essential gene, validating CRK1 as a potential drug target.
The expression of crk1 was further manipulated by engineering a hexa-histidine tag at the C-terminus of the kinase, allowing purifn. The Leishmania mexicana CRK3 gene encodes a cdc2-related protein kinase with activity towards histone H1. Attempts to disrupt both alleles of CRK3 in the promastigote life-cycle stage resulted in changes in cell ploidy, which were avoided only when an extra copy of CRK3 was expressed from an episome.
This provides strong evidence that CRK3 is essential to L. Incubation of promastigotes with 2. Methods Enzymol. Methods in Enzymology , Recomb. DNA, Pt. A review with 22 refs. A new plasmid shuffling procedure based on the 5-FOAR selection permits the recovery of conditional lethal mutations in cloned genes that encode vital functions. Murta, Silvane M. Leishmania major possesses single DHCH1 and FTL genes encoding exclusively cytosolic proteins, unlike other organisms where isoforms occur in the mitochondrion as well. Previous studies showed null ftl- mutants were normal, raising the possibility that loss of the purine synthetic pathway had rendered CHO-THF dispensable in evolution.
We were unable to generate dhch1- null mutants by gene replacement, despite using a wide spectrum of nutritional supplements expected to bypass DHCH function. We applied an improved method for testing essential genes in Leishmania, based on segregational loss of episomal complementing genes rather than transfection; anal.
Agents Gelmedin, V. Spiliotis, M. Suche Ansprechpartner. DE EN Intern. Aktuelles Archiv. Humanmedizin Hygiene und Umweltmedizin Zahnmedizin Mikrobiologie 8. Animation stoppen. Aktuelles Diag. Mikrobiologie Klin. Detrimental effects of the anti-cancer drug Imatinib on Echinococcus larvae Hemer and Brehm, OK Abbrechen. Anfahrt Campus Medizin. Campus Medizin.