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1.
Int J Parasitol Drugs Drug Resist ; 16: 140-147, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34111649

RESUMO

Human schistosomiasis is a debilitating, life-threatening disease affecting more than 229 million people in as many as 78 countries. There is only one drug of choice effective against all three major species of Schistosoma, praziquantel (PZQ). However, as with many monotherapies, evidence for resistance is emerging in the field and can be selected for in the laboratory. Previously used therapies include oxamniquine (OXA), but shortcomings such as drug resistance and affordability resulted in discontinuation. Employing a genetic, biochemical and molecular approach, a sulfotransferase (SULT-OR) was identified as responsible for OXA drug resistance. By crystallizing SmSULT- OR with OXA, the mode of action of OXA was determined. This information allowed a rational approach to novel drug design. Our team approach with schistosome biologists, medicinal chemists, structural biologists and geneticists has enabled us to develop and test novel drug derivatives of OXA to treat this disease. Using an iterative process for drug development, we have successfully identified derivatives that are effective against all three species of the parasite. One derivative CIDD-0149830 kills 100% of all three human schistosome species within 5 days. The goal is to generate a second therapeutic with a different mode of action that can be used in conjunction with praziquantel to overcome the ever-growing threat of resistance and improve efficacy. The ability and need to design, screen, and develop future, affordable therapeutics to treat human schistosomiasis is critical for successful control program outcomes.


Assuntos
Descoberta de Drogas , Esquistossomose , Animais , Humanos , Oxamniquine , Praziquantel/farmacologia , Schistosoma mansoni , Esquistossomose/tratamento farmacológico
2.
PLoS Negl Trop Dis ; 14(8): e0008517, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32810153

RESUMO

Currently there is only one method of treatment for human schistosomiasis, the drug praziquantel. Strong selective pressure has caused a serious concern for a rise in resistance to praziquantel leading to the necessity for additional pharmaceuticals, with a distinctly different mechanism of action, to be used in combination therapy with praziquantel. Previous treatment of Schistosoma mansoni included the use of oxamniquine (OXA), a prodrug that is enzymatically activated in S. mansoni but is ineffective against S. haematobium and S. japonicum. The oxamniquine activating enzyme was identified as a S. mansoni sulfotransferase (SmSULT-OR). Structural data have allowed for directed drug development in reengineering oxamniquine to be effective against S. haematobium and S. japonicum. Guided by data from X-ray crystallographic studies and Schistosoma worm killing assays on oxamniquine, our structure-based drug design approach produced a robust SAR program that tested over 300 derivatives and identified several new lead compounds with effective worm killing in vitro. Previous studies resulted in the discovery of compound CIDD-0066790, which demonstrated broad-species activity in killing of schistosome species. As these compounds are racemic mixtures, we tested and demonstrate that the R enantiomer CIDD-007229 kills S. mansoni, S. haematobium and S. japonicum better than the parent drug (CIDD-0066790). The search for derivatives that kill better than CIDD-0066790 has resulted in a derivative (CIDD- 149830) that kills 100% of S. mansoni, S. haematobium and S. japonicum adult worms within 7 days. We hypothesize that the difference in activation and thus killing by the derivatives is due to the ability of the derivative to fit in the binding pocket of each sulfotransferase (SmSULT-OR, ShSULT-OR, SjSULT-OR) and to be efficiently sulfated. The purpose of this research is to develop a second drug to be used in conjunction with praziquantel to treat the major human species of Schistosoma. Collectively, our findings show that CIDD-00149830 and CIDD-0072229 are promising novel drugs for the treatment of human schistosomiasis and strongly support further development and in vivo testing.


Assuntos
Anti-Helmínticos/farmacologia , Oxamniquine/análogos & derivados , Oxamniquine/farmacologia , Schistosoma/efeitos dos fármacos , Esquistossomose/parasitologia , Animais , Anti-Helmínticos/química , Simulação por Computador , Proteínas de Helminto/química , Proteínas de Helminto/metabolismo , Humanos , Modelos Biológicos , Modelos Moleculares , Estrutura Molecular , Oxamniquine/química , Ligação Proteica
3.
Chemistry ; 26(66): 15232-15241, 2020 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-32852116

RESUMO

Schistosomiasis is a disease of poverty affecting millions of people. Praziquantel (PZQ), with its strengths and weaknesses, is the only treatment available. We previously reported findings on three lead compounds derived from oxamniquine (OXA), an old antischistosomal drug: ferrocene-containing (Fc-CH2 -OXA), ruthenocene-containing (Rc-CH2 -OXA) and benzene-containing (Ph-CH2 -OXA) OXA derivatives. These derivatives showed excellent in vitro activity against both Schistosoma mansoni larvae and adult worms and S. haematobium adult worms, and were also active in vivo against adult S. mansoni. Encouraged by these promising results, we conducted additional in-depth preclinical studies and report in this investigation on metabolic stability studies, in vivo studies on S. haematobium and juvenile S. mansoni, computational simulations, and formulation development. Molecular dynamics simulations supported the in vitro results on the target protein. Though all three compounds were poorly stable within an acidic environment, they were only slightly cleared in the in vitro liver model. This is likely the reason why the promising in vitro activity did not translate into in vivo activity on S. haematobium. This limitation could not be overcome by the formulation of lipid nanocapsules as a way to improve the in vivo activity. Further studies should focus on increasing the compound's bioavailability, to reach an active concentration in the microenvironment of the parasite.


Assuntos
Oxamniquine/química , Preparações Farmacêuticas , Schistosoma mansoni/química , Esquistossomose mansoni , Esquistossomose , Animais , Humanos , Esquistossomose/tratamento farmacológico , Esquistossomose mansoni/tratamento farmacológico
4.
Artigo em Inglês | MEDLINE | ID: mdl-32315953

RESUMO

Human schistosomiasis is a disease which globally affects over 229 million people. Three major species affecting humans are Schistosoma mansoni, S. haematobium and S. japonicum. Previous treatment of S. mansoni includes the use of oxamniquine (OXA), a prodrug that is enzymatically activated in S. mansoni but is ineffective against S. haematobium and S. japonicum. The OXA activating enzyme was identified and crystallized, as being a S. mansoni sulfotransferase (SmSULT). S. haematobium and S. japonicum possess homologs of SmSULT (ShSULT and SjSULT) begging the question; why does oxamniquine fail to kill S. haematobium and S. japonicum adult worms? Investigation of the molecular structures of the sulfotransferases indicates that structural differences, specifically in OXA contact residues, do not abrogate OXA binding in the active sites as previously hypothesized. Data presented argue that the ability of SULTs to sulfate and thus activate OXA and its derivatives is linked to the ability of OXA to fit in the binding pocket to allow the transfer of a sulfur group.


Assuntos
Oxamniquine/farmacologia , Schistosoma/efeitos dos fármacos , Sulfotransferases/química , Animais , Estrutura Molecular , Schistosoma/metabolismo , Schistosoma haematobium/efeitos dos fármacos , Schistosoma haematobium/metabolismo , Schistosoma japonicum/efeitos dos fármacos , Schistosoma japonicum/metabolismo , Schistosoma mansoni/efeitos dos fármacos , Schistosoma mansoni/metabolismo , Esquistossomicidas/farmacologia , Sulfotransferases/efeitos dos fármacos , Sulfotransferases/metabolismo
5.
Mol Biochem Parasitol ; 236: 111257, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32027942

RESUMO

Hycanthone (HYC) is a retired drug formerly used to treat schistosomiasis caused by infection from Schistosoma mansoni and S. haematobium. Resistance to HYC was first observed in S. mansoni laboratory strains and in patients in the 1970s and the use of this drug was subsequently discontinued with the substitution of praziquantel (PZQ) as the single antischistosomal drug in the worldwide formulary. In endemic regions, multiple organizations have partnered with the World Health Organization to deliver PZQ for morbidity control and prevention. While the monotherapy reduces the disease burden, additional drugs are needed to use in combination with PZQ to stay ahead of potential drug resistance. HYC will not be reintroduced into the schistosomiasis drug formulary as a combination drug because it was shown to have adverse properties including mutagenic, teratogenic and carcinogenic activities. Oxamniquine (OXA) was used to treat S. mansoni infection in Brazil during the brief period of HYC use, until the 1990s. Its antischistosomal efficacy has been shown to work through the same mechanism as HYC and it does not possess the undesirable properties linked to HYC. OXA demonstrates cross-resistance in Schistosoma strains with HYC resistance and both are prodrugs requiring metabolic activation in the worm to toxic sulfated forms. The target activating enzyme has been identified as a sulfotransferase enzyme and is currently used as the basis for a structure-guided drug design program. Here, we characterize the sulfotransferases from S. mansoni and S. haematobium in complexes with HYC to compare and contrast with OXA-bound sulfotransferase crystal structures. Although HYC is discontinued for antischistosomal treatment, it can serve as a resource for design of derivative compounds without contraindication.


Assuntos
Hicantone , Oxamniquine/análogos & derivados , Esquistossomose/tratamento farmacológico , Sulfotransferases , Animais , Cristalização/métodos , Cristalografia por Raios X/métodos , Desenho de Fármacos , Resistência a Medicamentos , Humanos , Hicantone/efeitos adversos , Hicantone/análogos & derivados , Hicantone/química , Oxamniquine/química , Oxamniquine/uso terapêutico , Praziquantel/uso terapêutico , Ligação Proteica/efeitos dos fármacos , Proteínas Recombinantes/efeitos dos fármacos , Proteínas Recombinantes/metabolismo , Schistosoma haematobium/efeitos dos fármacos , Schistosoma haematobium/metabolismo , Schistosoma mansoni/efeitos dos fármacos , Schistosoma mansoni/metabolismo , Esquistossomicidas/uso terapêutico , Sulfotransferases/efeitos dos fármacos , Sulfotransferases/metabolismo
6.
Curr Comput Aided Drug Des ; 16(4): 451-459, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31284869

RESUMO

BACKGROUND: Sulfotransferase family comprises key enzymes involved in drug metabolism. Oxamniquine is a pro-drug converted into its active form by schistosomal sulfotransferase. The conformational dynamics of side-chain amino acid residues at the binding site of schistosomal sulfotransferase towards activation of oxamniquine has not received attention. OBJECTIVE: The study investigated the conformational dynamics of binding site residues in free and oxamniquine bound schistosomal sulfotransferase systems and their contribution to the mechanism of oxamniquine activation by schistosomal sulfotransferase using molecular dynamics simulations and binding energy calculations. METHODS: Schistosomal sulfotransferase was obtained from Protein Data Bank and both the free and oxamniquine bound forms were subjected to molecular dynamics simulations using GROMACS-4.5.5 after modeling it's missing amino acid residues with SWISS-MODEL. Amino acid residues at its binding site for oxamniquine was determined and used for Principal Component Analysis and calculations of side-chain dihedrals. In addition, binding energy of the oxamniquine bound system was calculated using g_MMPBSA. RESULTS: The results showed that binding site amino acid residues in free and oxamniquine bound sulfotransferase sampled different conformational space involving several rotameric states. Importantly, Phe45, Ile145 and Leu241 generated newly induced conformations, whereas Phe41 exhibited shift in equilibrium of its conformational distribution. In addition, the result showed binding energy of -130.091 ± 8.800 KJ/mol and Phe45 contributed -9.8576 KJ/mol. CONCLUSION: The results showed that schistosomal sulfotransferase binds oxamniquine by relying on hybrid mechanism of induced fit and conformational selection models. The findings offer new insight into sulfotransferase engineering and design of new drugs that target sulfotransferase.


Assuntos
Oxamniquine/farmacologia , Pró-Fármacos/farmacologia , Schistosoma/enzimologia , Esquistossomicidas/farmacologia , Sulfotransferases/metabolismo , Animais , Humanos , Simulação de Acoplamento Molecular , Simulação de Dinâmica Molecular , Oxamniquine/metabolismo , Pró-Fármacos/metabolismo , Schistosoma/química , Schistosoma/efeitos dos fármacos , Schistosoma/metabolismo , Esquistossomose/tratamento farmacológico , Esquistossomose/parasitologia , Esquistossomicidas/metabolismo , Sulfotransferases/química
7.
PLoS Pathog ; 15(10): e1007881, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31652296

RESUMO

Do mutations required for adaptation occur de novo, or are they segregating within populations as standing genetic variation? This question is key to understanding adaptive change in nature, and has important practical consequences for the evolution of drug resistance. We provide evidence that alleles conferring resistance to oxamniquine (OXA), an antischistosomal drug, are widespread in natural parasite populations under minimal drug pressure and predate OXA deployment. OXA has been used since the 1970s to treat Schistosoma mansoni infections in the New World where S. mansoni established during the slave trade. Recessive loss-of-function mutations within a parasite sulfotransferase (SmSULT-OR) underlie resistance, and several verified resistance mutations, including a deletion (p.E142del), have been identified in the New World. Here we investigate sequence variation in SmSULT-OR in S. mansoni from the Old World, where OXA has seen minimal usage. We sequenced exomes of 204 S. mansoni parasites from West Africa, East Africa and the Middle East, and scored variants in SmSULT-OR and flanking regions. We identified 39 non-synonymous SNPs, 4 deletions, 1 duplication and 1 premature stop codon in the SmSULT-OR coding sequence, including one confirmed resistance deletion (p.E142del). We expressed recombinant proteins and used an in vitro OXA activation assay to functionally validate the OXA-resistance phenotype for four predicted OXA-resistance mutations. Three aspects of the data are of particular interest: (i) segregating OXA-resistance alleles are widespread in Old World populations (4.29-14.91% frequency), despite minimal OXA usage, (ii) two OXA-resistance mutations (p.W120R, p.N171IfsX28) are particularly common (>5%) in East African and Middle-Eastern populations, (iii) the p.E142del allele has identical flanking SNPs in both West Africa and Puerto Rico, suggesting that parasites bearing this allele colonized the New World during the slave trade and therefore predate OXA deployment. We conclude that standing variation for OXA resistance is widespread in S. mansoni.


Assuntos
Resistência a Medicamentos/genética , Oxamniquine/uso terapêutico , Schistosoma mansoni/efeitos dos fármacos , Schistosoma mansoni/genética , Esquistossomicidas/uso terapêutico , Adaptação Fisiológica/genética , Alelos , Animais , Cricetinae , Humanos , Níger , Omã , Polimorfismo de Nucleotídeo Único/genética , Ratos , Esquistossomose mansoni/tratamento farmacológico , Senegal , Caramujos/parasitologia , Tanzânia
8.
PLoS Negl Trop Dis ; 13(1): e0006590, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30689639

RESUMO

BACKGROUND: The arsenal in anthelminthic treatment against schistosomiasis is limited and relies almost exclusively on a single drug, praziquantel (PZQ). Thus, resistance to PZQ could constitute a major threat. Even though PZQ is potent in killing adult worms, its activity against earlier stages is limited. Current in vitro drug screening strategies depend on newly transformed schistosomula (NTS) for initial hit identification, thereby limiting sensitivity to new compounds predominantly active in later developmental stages. Therefore, the aim of this study was to establish a highly standardized, straightforward and reliable culture method to generate and maintain advanced larval stages in vitro. We present here how this method can be a valuable tool to test drug efficacy at each intermediate larval stage, reducing the reliance on animal use (3Rs). METHODOLOGY/PRINCIPAL FINDINGS: Cercariae were mechanically transformed into skin-stage (SkS) schistosomula and successfully cultured for up to four weeks with no loss in viability in a commercially available medium. Under these serum- and cell-free conditions, development halted at the lung-stage (LuS). However, the addition of human serum (HSe) propelled further development into liver stage (LiS) worms within eight weeks. Skin and lung stages, as well as LiS, were submitted to 96-well drug screening assays using known anti-schistosomal compounds such as PZQ, oxamniquine (OXM), mefloquine (MFQ) and artemether (ART). Our findings showed stage-dependent differences in larval susceptibility to these compounds. CONCLUSION: With this robust and highly standardized in vitro assay, important developmental stages of S. mansoni up to LiS worms can be generated and maintained over prolonged periods of time. The phenotype of LiS worms, when exposed to reference drugs, was comparable to most previously published works for ex vivo harvested adult worms. Therefore, this in vitro assay can help reduce reliance on animal experiments in search for new anti-schistosomal drugs.


Assuntos
Schistosoma mansoni/efeitos dos fármacos , Schistosoma mansoni/crescimento & desenvolvimento , Esquistossomicidas/farmacologia , Animais , Artemeter/farmacologia , Cercárias/efeitos dos fármacos , Cercárias/crescimento & desenvolvimento , Meios de Cultura Livres de Soro/química , Meios de Cultura Livres de Soro/farmacologia , Avaliação Pré-Clínica de Medicamentos , Humanos , Mefloquina/farmacologia , Oxamniquine/farmacologia , Praziquantel/farmacologia , Esquistossomose mansoni/tratamento farmacológico , Esquistossomicidas/isolamento & purificação
9.
Parasit Vectors ; 11(1): 580, 2018 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-30400935

RESUMO

BACKGROUND: Schistosomiasis is one of the most harmful parasitic diseases worldwide, praziquantel being the only drug in widespread use to treat it. We recently demonstrated that ferrocenyl, ruthenocenyl and benzyl derivatives of oxamniquine (Fc-OXA, Rc-OXA and Bn-OXA) are promising antischistosomal drug candidates. METHODS: In this study we assessed the tegumental damage of these three derivatives of oxamniquine using scanning electron microscopy. Adult Schistosoma mansoni and S. haematobium were exposed to a concentration of 100 µM of each drug and incubated for 4-120 h, according to their onset of action and activity. RESULTS: While on S. mansoni the fastest acting compound was Fc-OXA, which revealed high activity after 4 h of incubation, on S. haematobium, Rc-OXA revealed the quickest onset, being lethal on all males within 24 h. In both species studied, the three derivatives showed the same patterns of tegumental damage consisting of blebs, sloughing and tegument rupturing all over the body. Additionally, on S. mansoni distinct patterns of tegumental damage were observed for each of the compounds: tissue ruptures in the gynaecophoric canal for Fc-OXA, loss of spines for Rc-OXA and oral sucker rupture for Bn-OXA. CONCLUSIONS: Our study confirmed that Fc-OXA, Rc-OXA and Bn-OXA are promising broad spectrum antischistosomal drug candidates. All derivatives show fast in vitro activity against S. mansoni and S. haematobium while validating the previous finding that the parent drug oxamniquine is less active in vitro under the conditions described. This work sets the base for further studies on the identification of a lead oxamniquine derivative, with the aim of identifying a molecule with the potential to become a new drug for human use.


Assuntos
Compostos Organometálicos/farmacologia , Oxamniquine/farmacologia , Schistosoma haematobium/anatomia & histologia , Schistosoma haematobium/efeitos dos fármacos , Schistosoma mansoni/anatomia & histologia , Schistosoma mansoni/efeitos dos fármacos , Animais , Feminino , Concentração Inibidora 50 , Camundongos , Microscopia Eletrônica de Varredura , Compostos Organometálicos/química , Oxamniquine/química , Schistosoma mansoni/ultraestrutura , Esquistossomose/parasitologia , Esquistossomicidas/farmacologia
10.
Artigo em Inglês | MEDLINE | ID: mdl-28971860

RESUMO

To date, there is only one drug in use, praziquantel, to treat more than 250 million people afflicted with schistosomiasis, a debilitating parasitic disease. The aryl hydantoin Ro 13-3978 is a promising drug candidate with in vivo activity superior to that of praziquantel against both adult and juvenile Schistosoma mansoni organisms. Given the drug's contrasting low activity in vitro and the timing of its onset of action in vivo, it was postulated that immune-assisted parasite clearance could contribute to the drug's in vivo activity. We undertook histopathological studies to investigate this hypothesis. Infected mice were treated with an effective dose of Ro 13-3978 (100 mg/kg of body weight) and were dissected before and after the drug's in vivo onset of action. The veins and livers were excised, paraffin-embedded, and sectioned, and macrophages (IBA-1), neutrophils (Neutro), B cells (CD45R), and T cells (CD3) were stained by immunohistochemistry. For comparison, samples from infected untreated mice and mice treated with effective doses of praziquantel (400 mg/kg), oxamniquine (200 mg/kg), and mefloquine (200 mg/kg) were examined. At 24 h after treatment with Ro 13-3978, significant macrophage recruitment to the veins was observed, along with a modest increase in circulating B cells, and at 48 h, neutrophils and T cells are also present. Treatment with praziquantel and oxamniquine showed similar patterns of recruitment but with comparatively higher cellular levels, whereas mefloquine treatment resulted in minimal cell recruitment until 3 days posttreatment. Our study sheds light on the immediate immune responses to antischistosomal treatment in mice and provides further insight into immune effector mechanisms of schistosome clearance.


Assuntos
Hidantoínas/farmacologia , Mefloquina/farmacologia , Oxamniquine/farmacologia , Praziquantel/farmacologia , Schistosoma mansoni/imunologia , Esquistossomose mansoni/tratamento farmacológico , Esquistossomose mansoni/imunologia , Esquistossomicidas/farmacologia , Animais , Linfócitos B/imunologia , Feminino , Macrófagos/imunologia , Masculino , Camundongos , Schistosoma mansoni/efeitos dos fármacos , Esquistossomose mansoni/parasitologia , Linfócitos T/imunologia
12.
Acta Trop ; 176: 179-187, 2017 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28803725

RESUMO

Neglected tropical diseases (NTDs) affect millions of people in different geographic regions, especially the poorest and most vulnerable. Currently NTDs are prevalent in 149 countries, seventeen of these neglected tropical parasitic diseases are classified as endemic. One of the most important of these diseases is schistosomiasis, also known as bilharzia, a disease caused by the genus Schistosoma. It presents several species, such as Schistosoma haematobium, Schistosoma japonicum and Schistosoma mansoni, the latter being responsible for parasitosis in Brazil. Contamination occurs through exposure to contaminated water in the endemic region. This parasitosis is characterized by being initially asymptomatic, but it is able to evolve into more severe clinical forms, potentially causing death. Globally, more than 200 million people are infected with one of three Schistosome species, including an estimated 40 million women of reproductive age. In Brazil, about 12 million children require preventive chemotherapy with anthelmintic. However, according to the World Health Organization (WHO), only about 15% of the at-risk children receive regular treatment. The lack of investment by the pharmaceutical industry for the development and/or improvement of new pharmaceutical forms, mainly aimed at the pediatric public, is a great challenge. Currently, the main forms of treatment used for schistosomiasis are praziquantel (PZQ) and oxaminiquine (OXA). PZQ is the drug of choice because it presents as a high-spectrum anthelmintic, used in the treatment of all known species of schistosomiasis and some species of cestodes and trematodes. OXA, however, is not active against the three Schistosome species. This work presents a literature review regarding schistosomiasis. It addresses points such as available treatments, the role of the pharmaceutical industry against neglected diseases, and perspectives for treatment.


Assuntos
Anti-Helmínticos/uso terapêutico , Doenças Negligenciadas/tratamento farmacológico , Oxamniquine/uso terapêutico , Praziquantel/uso terapêutico , Esquistossomose/tratamento farmacológico , Animais , Pesquisa Biomédica , Brasil , Criança , Feminino , Humanos , Schistosoma haematobium , Schistosoma japonicum , Schistosoma mansoni , Esquistossomose/epidemiologia , Microbiologia da Água
13.
ACS Infect Dis ; 3(9): 645-652, 2017 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-28686009

RESUMO

Schistosomiasis is a parasitic disease that affects more than 250 million people annually, mostly children in poor, tropical, rural areas. Only one treatment (praziquantel) is available, putting control efforts at risk should resistance occur. In pursuit of treatment alternatives, we derivatized an old antischistosomal agent, oxamniquine (OXA). Four organometallic derivatives of OXA were synthesized and tested against Schistosoma mansoni in vitro and in vivo. Of these, a ferrocenyl derivative, 1, killed larval and adult worms 24 h postexposure in vitro, in contrast to OXA, which lacks in vitro activity against adult worms. A dose of 200 mg/kg of 1 completely eliminated the worm burden in mice. Subsequently, a ruthenocenyl (5) and a benzyl derivative (6) of OXA were synthesized to probe the importance of the ferrocenyl group in 1. Compounds 1, 5, and 6 were lethal to both S. mansoni and S. haematobium adults in vitro. In vivo, at 100 mg/kg, all three compounds revealed S. mansoni worm burden reductions of 76 to 93%, commensurate with OXA. Our findings present three compounds with activity against S. mansoni in vitro, comparable activity in vivo, and high activity against S. haematobium in vitro. These compounds may possess a different binding mode or mode of action compared to OXA and present excellent starting points for further SAR studies.


Assuntos
Anti-Helmínticos/administração & dosagem , Compostos Organometálicos/administração & dosagem , Oxamniquine/análogos & derivados , Esquistossomose Urinária/tratamento farmacológico , Esquistossomose mansoni/tratamento farmacológico , Animais , Anti-Helmínticos/síntese química , Anti-Helmínticos/química , Anti-Helmínticos/farmacologia , Química Farmacêutica , Modelos Animais de Doenças , Feminino , Masculino , Camundongos , Compostos Organometálicos/síntese química , Compostos Organometálicos/química , Compostos Organometálicos/farmacologia , Schistosoma haematobium/efeitos dos fármacos , Schistosoma mansoni/efeitos dos fármacos , Relação Estrutura-Atividade
14.
J Biol Chem ; 292(27): 11154-11164, 2017 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-28536265

RESUMO

The antischistosomal prodrug oxamniquine is activated by a sulfotransferase (SULT) in the parasitic flatworm Schistosoma mansoni. Of the three main human schistosome species, only S. mansoni is sensitive to oxamniquine therapy despite the presence of SULT orthologs in Schistosoma hematobium and Schistosoma japonicum The reason for this species-specific drug action has remained a mystery for decades. Here we present the crystal structures of S. hematobium and S. japonicum SULTs, including S. hematobium SULT in complex with oxamniquine. We also examined the activity of the three enzymes in vitro; surprisingly, all three are active toward oxamniquine, yet we observed differences in catalytic efficiency that implicate kinetics as the determinant for species-specific toxicity. These results provide guidance for designing oxamniquine derivatives to treat infection caused by all species of schistosome to combat emerging resistance to current therapy.


Assuntos
Resistência a Medicamentos , Proteínas de Helminto/química , Oxamniquine , Schistosoma haematobium/enzimologia , Schistosoma japonicum/enzimologia , Sulfotransferases/química , Animais , Cristalografia por Raios X , Proteínas de Helminto/genética , Proteínas de Helminto/metabolismo , Schistosoma haematobium/genética , Schistosoma japonicum/genética , Sulfotransferases/genética
15.
Bioorg Med Chem ; 25(13): 3259-3277, 2017 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-28495384

RESUMO

Neglected tropical diseases (NTDs) are a group of diseases that, besides prevailing in poverty conditions, contribute to the maintenance of social inequality, being a strong barrier to a country development. Schistosomiasis, a NTD, is a tropical and subtropical disease caused by the trematode Schistosoma mansoni (Africa, Middle East, Caribbean, Brazil, Venezuela, Suriname), japonicum (China, Indonesia, the Philippines), mekongi (several districts of Cambodia and the Lao People's Democratic Republic), intercalatum and guianensis (areas of tropical rainforests in Central Africa) and hematobium (Middle East Africa, Corsica, France) whose adult forms inhabit the mesenteric vessels of the host, while the intermediate forms are found in the aquatic gastropod snails of the genus Biomphalaria. Currently, praziquantel (PZQ) is the first line drug chosen for the treatment of schistosomiasis according to the World Health Organization (WHO) Model List of Essential Medicines, 2015. PZQ chemotherapy is considered to be the most important development for decades in the treatment of schistosomiasis. Beside the PZQ, oxamniquine (OXA) has been first described in 1969 and launched in Brazil by Pfizer under the name of Mansil® for oral administration. It has a lower cost when compared to PZQ, being active in the intestinal and hepatosplenic infections caused exclusively by S. mansoni, single species in Brazil. Both PZQ and OXA have limitations, as low efficacy in the treatment of acute schistosomiasis, low activity against S. mansoni in immature stages and resistance or tolerance, which is the reason why further research are still necessary for the development of a second generation of antischistosomal drugs. For the development of new PZQ analogs, three main strategies can be adopted: (a) synthesis and evaluation of PZQ analogues; (b) rational design of new pharmacophores; (c) discovery of new active compounds from screening programs on a large scale. Such (b) approach is difficult as the target of PZQ still unknown, the synthesis of new active analogues is possible from delineation of structure-activity relationships for PZQ. Thus, we proposed for a review article an accurate analysis of PZQ and OXA medicinal properties and uses, focusing on the pharmacochemical aspects of both drugs through 178 bibliographic references. The mechanisms of action will be discussed, with the latest information available in the literature (for the first time in the case of the oxamniquine). Cases of resistance are also discussed. As both drugs are available as a racemic mixture the biological impact of their stereochemistry to activity and side effects are reviewed. The results obtained for the combination of PZQ and artemisinin derivatives against immature worms are also introduced in the discussion. Using the information about more than 200 PZQ new derivatives synthetized during almost 35years since its discovery, a deep structure-activity relationship (SAR) is also proposed in this study.


Assuntos
Doenças Negligenciadas/tratamento farmacológico , Oxamniquine/farmacologia , Praziquantel/farmacologia , Schistosoma mansoni/efeitos dos fármacos , Animais , Química Farmacêutica , Relação Dose-Resposta a Droga , Humanos , Estrutura Molecular , Oxamniquine/química , Praziquantel/química , Relação Estrutura-Atividade
17.
Int J Parasitol ; 46(7): 417-24, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-27073078

RESUMO

Molecular surveillance provides a powerful approach to monitoring the resistance status of parasite populations in the field and for understanding resistance evolution. Oxamniquine was used to treat Brazilian schistosomiasis patients (mid-1970s to mid-2000s) and several cases of parasite infections resistant to treatment were recorded. The gene underlying resistance (SmSULT-OR) encodes a sulfotransferase required for intracellular drug activation. Resistance has a recessive basis and occurs when both SmSULT-OR alleles encode for defective proteins. Here we examine SmSULT-OR sequence variation in a natural schistosome population in Brazil ∼40years after the first use of this drug. We sequenced SmSULT-OR from 189 individual miracidia (1-11 per patient) recovered from 49 patients, and tested proteins expressed from putative resistance alleles for their ability to activate oxamniquine. We found nine mutations (four non-synonymous single nucleotide polymorphisms, three non-coding single nucleotide polymorphisms and two indels). Both mutations (p.E142del and p.C35R) identified previously were recovered in this field population. We also found two additional mutations (a splice site variant and 1bp coding insertion) predicted to encode non-functional truncated proteins. Two additional substitutions (p.G206V, p.N215Y) tested had no impact on oxamniquine activation. Three results are of particular interest: (i) we recovered the p.E142del mutation from the field: this same deletion is responsible for resistance in an oxamniquine selected laboratory parasite population; (ii) frequencies of resistance alleles are extremely low (0.27-0.8%), perhaps due to fitness costs associated with carriage of these alleles; (iii) that four independent resistant alleles were found is consistent with the idea that multiple mutations can generate loss-of-function alleles.


Assuntos
Mutação , Oxamniquine/farmacologia , Schistosoma mansoni/efeitos dos fármacos , Esquistossomose/parasitologia , Esquistossomicidas/farmacologia , Alelos , Animais , Brasil , Criança , Pré-Escolar , Resistência a Medicamentos/genética , Éxons/genética , Fezes/parasitologia , Frequência do Gene , Estudo de Associação Genômica Ampla , Humanos , Lactente , Conformação Molecular , Reação em Cadeia da Polimerase , Polimorfismo de Nucleotídeo Único , Schistosoma mansoni/genética
18.
Am J Trop Med Hyg ; 94(1): 156-7, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26598562

RESUMO

Ectopic schistosomiasis is uncommon and tends to occur when the parasite's eggs or adult forms are located far from their normal site. This report presents the first described case of ectopic Schistosoma mansoni eggs inside a subcutaneous lipoma far from the tissues of this worm's life cycle and with no connection to either portal veins or any other vascular system. These eggs were found inside giant cells surrounded by inflammatory cells. In conclusion, in humans, ectopic S. mansoni eggs can be found far from the tissues of the described life cycle of this worm, with no connection to portal veins or other blood vessels used for their migration.


Assuntos
Lipoma/patologia , Óvulo/classificação , Schistosoma mansoni/classificação , Esquistossomose mansoni/patologia , Adulto , Animais , Humanos , Lipoma/parasitologia , Lipoma/cirurgia , Masculino , Oxamniquine/uso terapêutico , Esquistossomose mansoni/tratamento farmacológico , Esquistossomose mansoni/parasitologia , Esquistossomicidas/uso terapêutico
19.
PLoS Negl Trop Dis ; 9(10): e0004132, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26485649

RESUMO

BACKGROUND: For over two decades, a racemic mixture of oxamniquine (OXA) was administered to patients infected by Schistosoma mansoni, but whether one or both enantiomers exert antischistosomal activity was unknown. Recently, a ~30 kDa S. mansoni sulfotransferase (SmSULT) was identified as the target of OXA action. METHODOLOGY/PRINCIPAL FINDINGS: Here, we separate the OXA enantiomers using chromatographic methods and assign their optical activities as dextrorotary [(+)-OXA] or levorotary [(-)-OXA]. Crystal structures of the parasite enzyme in complex with optically pure (+)-OXA and (-)-OXA) reveal their absolute configurations as S- and R-, respectively. When tested in vitro, S-OXA demonstrated the bulk of schistosomicidal activity, while R-OXA had antischistosomal effects when present at relatively high concentrations. Crystal structures R-OXA•SmSULT and S-OXA•SmSULT complexes reveal similarities in the modes of OXA binding, but only the S-OXA enantiomer is observed in the structure of the enzyme exposed to racemic OXA. CONCLUSIONS/SIGNIFICANCE: Together the data suggest the higher schistosomicidal activity of S-OXA is correlated with its ability to outcompete R-OXA binding the sulfotransferase active site. These findings have important implications for the design, syntheses, and dosing of new OXA-based antischistosomal compounds.


Assuntos
Anti-Helmínticos/química , Anti-Helmínticos/farmacologia , Oxamniquine/química , Oxamniquine/farmacologia , Sulfotransferases/antagonistas & inibidores , Sulfotransferases/química , Animais , Cromatografia , Cristalografia por Raios X , Feminino , Camundongos , Modelos Moleculares , Testes de Sensibilidade Parasitária , Ligação Proteica , Conformação Proteica , Schistosoma mansoni/efeitos dos fármacos , Schistosoma mansoni/enzimologia , Estereoisomerismo
20.
BMC Genomics ; 15: 617, 2014 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-25048426

RESUMO

BACKGROUND: Identification of parasite genes that underlie traits such as drug resistance and host specificity is challenging using classical linkage mapping approaches. Extreme QTL (X-QTL) methods, originally developed by rodent malaria and yeast researchers, promise to increase the power and simplify logistics of linkage mapping in experimental crosses of schistosomes (or other helminth parasites), because many 1000s of progeny can be analysed, phenotyping is not required, and progeny pools rather than individuals are genotyped. We explored the utility of this method for mapping a drug resistance gene in the human parasitic fluke Schistosoma mansoni. RESULTS: We staged a genetic cross between oxamniquine sensitive and resistant parasites, then between two F1 progeny, to generate multiple F2 progeny. One group of F2s infecting hamsters was treated with oxamniquine, while a second group was left untreated. We used exome capture to reduce the size of the genome (from 363 Mb to 15 Mb) and exomes from pooled F2 progeny (treated males, untreated males, treated females, untreated females) and the two parent parasites were sequenced to high read depth (mean = 95-366×) and allele frequencies at 14,489 variants compared. We observed dramatic enrichment of alleles from the resistant parent in a small region of chromosome 6 in drug-treated male and female pools (combined analysis: Z = 11.07, p = 8.74 × 10(-29)). This region contains Smp_089320 a gene encoding a sulfotransferase recently implicated in oxamniquine resistance using classical linkage mapping methods. CONCLUSIONS: These results (a) demonstrate the utility of exome capture for generating reduced representation libraries in Schistosoma mansoni, and (b) provide proof-of-principle that X-QTL methods can be successfully applied to an important human helminth. The combination of these methods will simplify linkage analysis of biomedically or biologically important traits in this parasite.


Assuntos
Exoma/genética , Locos de Características Quantitativas , Schistosoma mansoni/genética , Animais , Mapeamento Cromossômico , Cricetinae , Cruzamentos Genéticos , Feminino , Frequência do Gene , Ligação Genética , Genótipo , Masculino , Oxamniquine/uso terapêutico , Fenótipo , Esquistossomose mansoni/tratamento farmacológico , Esquistossomicidas/uso terapêutico , Sulfotransferases/metabolismo
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