Discovery of new Schistosoma mansoni aspartyl protease inhibitors by structure-based virtual screening

BACKGROUND Schistosomiasis is a neglected tropical disease caused by trematodes of the genus Schistosoma, with a limited treatment, mainly based on the use of praziquantel (PZQ). Currently, several aspartic proteases genes have already been identified within the genome of Schistosoma species. At least one enzyme encoded from this gene family (SmAP), named SmCD1, has been validated for the development of schistosomicidal drugs, since it has a key role in haemoglobin digestion by worms. OBJECTIVE In this work, we integrated a structure-based virtual screening campaign, enzymatic assays and adult worms ex vivo experiments aiming to discover the first classes of SmCD1 inhibitors. METHODS Initially, the 3D-structures of SmCD1, SmCD2 and SmCD3 were generated using homology modelling approach. Using these models, we prioritised 50 compounds from 20,000 compounds from ChemBridge database for further testing in adult worm aqueous extract (AWAE) and recombinant SmCD1 using enzymatic assays. FINDINGS Seven compounds were confirmed as hits and among them, two compounds representing new chemical scaffolds, named 5 and 19, had IC50 values against SmCD1 close to 100 μM while presenting binding efficiency indexes comparable to or even higher than pepstatin, a classical tight-binding peptide inhibitor of aspartyl proteases. Upon activity comparison against mammalian enzymes, compound 50 was selective and the most potent against the AWAE aspartic protease activity (IC50 = 77.7 μM). Combination of computational and experimental results indicate that compound 50 is a selective inhibitor of SmCD2. Compounds 5, 19 and 50 tested at low concentrations (10 uM) were neither cytotoxic against WSS-1 cells (48 h) nor could kill adult worms ex-vivo, although compounds 5 and 50 presented a slight decrease on female worms motility on late incubations times (48 or 72 h). MAIN CONCLUSION Overall, the inhibitors identified in this work represent promising hits for further hit-to-lead optimisation.

In silico repositioning of new drugs against Schistosoma mansoni

Schistosomiasis is a neglected tropical disease caused by parasites of the genus Schistosoma. In Brazil only Schistosoma mansoni causes this disease. The World Health Organization estimated in 2012 approximately 249 million people at risk of acquiring this disease around the world. The main strategy to control this disease is praziquantel treatment of individuals living in endemic areas. The drug praziquantel is used on a large scale in the treatment of schistosomiasis and currently there are reported cases of resistance, indicating the need to discover new drugs. In silico drug repositioning is a time and cost reducing strategy in the search for anti-Schistosoma agents. This work used bioinformatic tools to identify potential schistosomicidal drugs. A list was compiled of S. mansoni potential targets that are part of essential processes in the database TDR and the targets that are part of the tegument were obtained in the scientific literature. The file with S. mansoni targets contained 1,376 targets, and of these only 61 targets associated with 399 drugs had homology with drug targets. After removal of duplicate drugs, drugs found in previous studies and after the analysis of the conservation of the binding site, only 28 S. mansoni targets associated with 102 drugs had 60% or more of the active site conserved. Some of the drugs had activity and are interesting to validate this study such as: artemether, lumefantrine, meloxicam. Among the drugs found 18 drugs were selected to be tested in prospective experimental assays according to the following criteria: low toxicity in vivo, off-patent status, and logP <5.0.

Synthesis and molecular modelling studies of pyrimidinones and pyrrolo[34-d]-pyrimidinodiones as new antiplasmodial compounds

BACKGROUND Malaria is responsible for 429,000 deaths per year worldwide, and more than 200 million cases were reported in 2015. Increasing parasite resistance has imposed restrictions to the currently available antimalarial drugs. Thus, the search for new, effective and safe antimalarial drugs is crucial. Heterocyclic compounds, such as dihydropyrimidinones (DHPM), synthesised via the Biginelli multicomponent reaction, as well as bicyclic compounds synthesised from DHPMs, have emerged as potential antimalarial candidates in the last few years. METHODS Thirty compounds were synthesised employing the Biginelli multicomponent reaction and subsequent one-pot substitution/cyclisation protocol; the compounds were then evaluated in vitro against chloroquine-resistant Plasmodium falciparum parasites (W2 strain). Drug cytotoxicity in baseline kidney African Green Monkey cells (BGM) was also evaluated. The most active in vitro compounds were evaluated against P. berghei parasites in mice. Additionally, we performed an in silico target fishing approach with the most active compounds, aiming to shed some light into the mechanism at a molecular level. RESULTS The synthetic route chosen was effective, leading to products with high purity and yields ranging from 10-84%. Three out of the 30 compounds tested were identified as active against the parasite and presented low toxicity. The in silico study suggested that among all the molecular targets identified by our target fishing approach, Protein Kinase 3 (PK5) and Glycogen Synthase Kinase 3β (GSK-3β) are the most likely molecular targets for the synthesised compounds. CONCLUSIONS We were able to easily obtain a collection of heterocyclic compounds with in vitro anti-P. falciparum activity that can be used as scaffolds for the design and development of new antiplasmodial drugs.

Computational drug discovery for the Zika virus

Few Zika virus (ZIKV) outbreaks had been reported since its first detection in 1947, until the recent epidemics occurred in South America (2014/2015) and expeditiously became a global public health emergency. This arbovirus reached 0.5-1.3 million cases of ZIKV infection in Brazil in 2015 and rapidly spread in new geographic areas such as the Americas. Despite the mild symptoms of the Zika fever, the major concern is related to the related severe neurological disorders, especially microcephaly in newborns. Advances in ZIKV drug discovery have been made recently and constitute promising approaches to ZIKV treatment. In this review, we summarize current computational drug discovery efforts and their applicability to discovery of anti-ZIKV drugs. Lastly, we present successful examples of the use of computational approaches to ZIKV drug discovery.

Efficacy of sertraline against Trypanosoma cruzi: an in vitro and in silico study

Drug repurposing has been an interesting and cost-effective approach, especially for neglected diseases, such as Chagas disease. Methods: In this work, we studied the activity of the antidepressant drug sertraline against Trypanosoma cruzi trypomastigotes and intracellular amastigotes of the Y and Tulahuen strains, and investigated its action mode using cell biology and in silico approaches. Results: Sertraline demonstrated in vitro efficacy against intracellular amastigotes of both T. cruzi strains inside different host cells, including cardiomyocytes, with IC50 values between 1 to 10 µM, and activity against bloodstream trypomastigotes, with IC50 of 14 µM. Considering the mammalian cytotoxicity, the drug resulted in a selectivity index of 17.8. Sertraline induced a change in the mitochondrial integrity of T. cruzi, resulting in a decrease in ATP levels, but not affecting reactive oxygen levels or plasma membrane permeability. In silico approaches using chemogenomic target fishing, homology modeling and molecular docking suggested the enzyme isocitrate dehydrogenase 2 of T. cruzi (TcIDH2) as a potential target for sertraline. Conclusions: The present study demonstrated that sertraline had a lethal effect on different forms and strains of T. cruzi, by affecting the bioenergetic metabolism of the parasite. These findings provide a starting point for future experimental assays and may contribute to the development of new compounds.(AU)

Twenty-six years of HIV science: an overview of anti-HIV drugs metabolism / Regulamento de medicamentos fitoterápicos no Brasil: avanços e perspectivas

From the identification of HIV as the agent causing AIDS, to the development of effective antiretroviral drugs, the scientific achievements in HIV research over the past twenty-six years have been formidable. Currently, there are twenty-five anti-HIV compounds which have been formally approved for clinical use in the treatment of AIDS. These compounds fall into six categories: nucleoside reverse transcriptase inhibitors (NRTIs), nucleotide reverse transcriptase inhibitors (NtRTIs), non-nucleoside reverse transcriptase inhibitors (NNRTIs), protease inhibitors (PIs), cell entry inhibitors or fusion inhibitors (FIs), co-receptor inhibitors (CRIs), and integrase inhibitors (INIs). Metabolism by the host organism is one of the most important determinants of the pharmacokinetic profile of a drug. Formation of active or toxic metabolites will also have an impact on the pharmacological and toxicological outcomes. Therefore, it is widely recognized that metabolism studies of a new chemical entity need to be addressed early in the drug discovery process. This paper describes an overview of the metabolism of currently available anti-HIV drugs.

Da identificação do HIV como o agente causador da AIDS, ao desenvolvimento de fármacos antirretrovirais eficazes, os avanços científicos na pesquisa sobre o HIV nos últimos vinte e seis anos foram marcantes. Atualmente, existem vinte e cinco fármacos anti-HIV formalmente aprovados pelo FDA para utilização clínica no tratamento da AIDS. Estes compostos são divididos em seis classes: inibidores nucleosídeos de transcriptase reversa (INTR), inibidores nucleotídeos de transcriptase reversa (INtTR), inibidores não-nucleosídeos de transcriptase reversa (INNTR), inibidores de protease (IP), inibidores da entrada celular ou inibidores de fusão (IF), inibidores de co-receptores (ICR) e inibidores de integrase (INI). O metabolismo consiste em um dos maiores determinantes do perfil farmacocinético de um fármaco. A formação de metabólitos ativos ou tóxicos terá impacto nas respostas farmacológicas ou toxicológicas do fármaco. Portanto, é amplamente reconhecido que estudos do metabolismo de uma nova entidade química devem ser realizados durante as fases iniciais do processo de desenvolvimento de fármacos. Este artigo descreve uma abordagem do metabolismo dos fármacos anti-HIV atualmente disponíveis na terapêutica.

Planejamento racional de novos tuberculostáticos com base na estrutura das enzimas enoil redutase e timidina monofosfato quinase do Mycobacterium tuberculosis / Rational design of new antituberculosis agents based on the structures of Mycobacterium tuberculosis enzymes enoyl reductase and thymidylate kinase

Nos últimos quinze anos, a tuberculose (TB) ressurgiu tanto em países em desenvolvimento quanto naqueles desenvolvidos. Em 1993, a Organização Mundial da Saúde (OMS) declarou a TB como emergência global de saúde pública. Atualmente, um terço da população mundial está infectada pelo Mycobacterium tuberculosis e mais de 10% destes indivíduos desenvolverão a doença ativa. Em 2006, estimaram-se 9 milhões de novos casos de TB em todo o mundo. No Brasil, aproximadamente 95.000 novos casos são registrados anualmente, com incidência de 50 casos em cada 100.000 habitantes. Tendo em vista o quadro alarmante da TB no mundo e, em especial no Brasil, e considerando os índices elevados de resistência do microrganismo aos fármacos convencionalmente utilizados na terapêutica, há necessidade urgente do desenvolvimento de novos tuberculostáticos. Além disso, a busca por novos alvos de ação se faz necessária, já que os antimicobacterianos utilizados na terapia anti-TB têm como alvo apenas pequeno número de enzimas relacionadas a funções essenciais do microrganismo. A biossíntese bacteriana de ácidos graxos tem despertado atenção especial como alvo atraente no desenvolvimento de novos agentes antibacterianos. Diferenças bioquímicas e funcionais fazem com que as enzimas envolvidas em tal processo sejam alvos potencialmente atraentes para o desenvolvimento de novos agentes antibacterianos/antimicobacterianos. As enoil-acp redutases são enzimas determinantes na etapa de alongamento de ácidos graxos, produtos intermediários na biossíntese dos principais constituintes da parede celular micobacteriana, os ácidos micólicos...

Abordagem racional no planejamento de novos tuberculostáticos: inibidores da InhA, enoil-ACP redutase do M. tuberculosis: [revisão] / Rational approach in the new antituberculosis agent design: inhibitors of InhA, the enoyl-ACP reductase from Mycobacterium tuberculosis: [review]

Associada à disseminação da infecção causada pelo HIV, a tuberculose (TB) é considerada, atualmente, problema mundial de saúde pública devido às proporções que vem assumindo. A resistência micobacteriana aos fármacos utilizados na terapêutica é a principal causa da reincidência da TB. Diante deste quadro alarmante, o desenvolvimento de novos e seletivos fármacos anti-TB se faz urgente e necessário. A biossíntese de ácidos graxos é um processo bioquímico realizado por procariotos e eucariotos, o qual fornece precursores essenciais à montagem de componentes celulares importantes, tais como fosfolipídeos, lipoproteínas, lipopolissacarídeos, ácidos micólicos e envelope celular. As diferenças bioquímicas e funcionais entre o mecanismo biossintético de ácidos graxos em bactérias e mamíferos tornam-no alvo relevante ao planejamento de novos antibacterianos, mais seletivos e menos tóxicos. As enoil-ACP redutases são enzimas cruciais à etapa de alongamento de ácidos graxos, considerados produtos intermediários na biossíntese de ácidos micólicos - os principais componentes da parede celular micobacteriana. Portanto, tais enzimas são tidas como alvos moleculares no planejamento racional de novos tuberculostáticos. Avanços recentes no processo de descoberta de novos agentes anti-TB, particularmente os inibidores da enoil-ACP redutase, serão discutidos nesta revisão.

In conjunction with the spread of HIV infection, tuberculosis (TB) has been among the worldwide health threats. Mycobacteria resistance to the drugs currently used in the therapeutics is the main cause of TB resurgence. In view of this severe situation, the new and selective anti-TB design is of utmost importance. Fatty acid biosynthesis is a prokariontes and eucariontes biochemical process that supplies essential precursors for the assembly of important cellular components, such as phospholipids, lipoproteins, lipopolysaccharides, mycolic acids and cellular envelope. However, the biochemical and functional differences between the bacterial and mammals' fatty acid synthetic pathway have endowed the mycobacterial enzymes with distinct properties. These provide valuable opportunities for structure- or catalytic mechanism-based design of selective inhibitors as novel anti-TB drugs with improved properties. The enoyl-reductases are essential enzymes in the fatty acids elongation pathway towards the mycolic acids, the main mycobacteria cell wall constituents, biosynthesis and so they are potential targets to the rational new antimycobacteria drug design. This paper highlights recent approaches regarding the design of new anti-TB agents, particularly, the enoyl-ACP reductase inhibitors.