Disposition of mefloquine and enpiroline is highly influenced by a chronic Schistosoma mansoni infection.

Chronic Schistosoma mansoni infections lead to severe tissue destruction of the gut wall and liver and can influence drug disposition. This study aimed to investigate the impact of a chronic S. mansoni infection on the pharmacokinetic (PK) parameters of two promising antischistosomal lead candidates (mefloquine and enpiroline) in mice. Studies were conducted in two different mouse cohorts (S. mansoni-infected and uninfected mice) for both drugs. Plasma samples were collected at various time points after oral treatment (200 mg/kg of body weight) with study drugs. A high-performance liquid chromatography (HPLC) method was validated to analyze enpiroline and mefloquine in plasma. Livers and intestines were collected from infected animals to determine the onset of action, hepatic shift, and worm burden reduction. Following mefloquine administration, hepatic shifting and significant worm burden reductions (79.2%) were observed after 72 h. At 1 week posttreatment with enpiroline, the majority of worms had migrated to the liver and significant worm burden reductions were observed (93.1%). The HPLC method was selective, accurate (87.8 to 111.4%), and precise (<10%) for the analysis of both drugs in plasma samples. The PK profiles revealed increased values for half-life (t1/2) and area under the concentration-time curve (AUC) for both drugs in infected animals compared to the t1/2 and AUC values in uninfected animals. Considerable changes were observed for mefloquine, with a 5-fold increase of t1/2 (182.7 h versus 33.6 h) and 2-fold increase of AUC (1,116,517.8 ng · h/ml versus 522,409.1 ng · h/ml). S. mansoni infections in mice influence the PK profiles of enpiroline and mefloquine, leading to delayed clearance. Our data confirm that drug disposition should be carefully studied in schistosomiasis patients.

[(η(6)-Praziquantel)Cr(CO)3] derivatives with remarkable in vitro anti-schistosomal activity.

The antischistosomal effect of two [(η(6)-praziquantel)Cr(CO)(3)] derivatives was investigated. The compounds (see figure: Cr purple, N blue, O red) were prepared in a one-step procedure from commercially available praziquantel. Both derivatives show a high in vitro activity against Schistosoma mansoni, a parasitic trematode, and only a minor cytotoxic effect on selected mammalian cell lines.

Enhancing the usefulness of cross dehydrogenative coupling reactions with a removable protecting group.

A removable protecting group has been identified that allows the products of widely-used cross dehydrogenative couplings to be synthetically elaborated. The method can be used with enantiopure amines with no loss of enantiomeric excess. The methodology is exemplified by a new synthesis of enantiopure praziquantel, the drug used in the treatment of millions of people suffering from the neglected tropical disease, schistosomiasis.

Antischistosomal activities of mefloquine-related arylmethanols.

Interesting antischistosomal properties have been documented for the antimalarial mefloquine, a 4-quinolinemethanol. We evaluated the antischistosomal activities of nine mefloquine-related compounds belonging to the 4-pyridinemethanols, 9-phenanthrenmethanols, and 4-quinolinemethanols. Eight compounds revealed high activities against Schistosoma mansoni in vitro, with two drugs (the 4-quinolinemethanols WR7573 and WR7930) characterized by significantly lower half-maximal inhibitory concentrations (IC(50)s) (2.7 and 3.5 µM, respectively) compared to mefloquine (11.4 µM). Mefloquine and WR7930 showed significantly decreased IC(50)s when incubated in the presence of hemoglobin. High worm burden reductions (WBR) were obtained with enpiroline (WBR, 82.7%; dosage, 200 mg/kg of body weight) and its threo isomers (+)-threo (WBR, 100%) and (-)-threo (WBR, 89%) and with WR7930 (WBR, 87%; dosage, 100 mg/kg) against adult S. mansoni in mice. Furthermore, excellent in vitro and in vivo antischistosomal activity was observed for two WR7930-related structures (WR29252 and WR7524). In addition, mefloquine (WBR, 81%), enpiroline (WBR, 77%), and WR7930 (WBR, 100%) showed high activities against S. haematobium harbored in mice following single oral doses of 200 mg/kg. These results provide a deeper insight into the structural features of the arylmethanols that rule antischistosomal activity. Further studies should be launched with enpiroline and WR7930.

In vivo activity of aryl ozonides against Schistosoma species.

We evaluated the in vivo antischistosomal activities of 11 structurally diverse synthetic peroxides. Of all compounds tested, ozonide (1,2,4-trioxolane) OZ418 had the highest activity against adult Schistosoma mansoni, with total and female worm burden reductions of 80 and 90% (P < 0.05), respectively. Furthermore, treatment of S. haematobium-infected mice with OZ418 reduced the total worm burden by 86%. In conclusion, OZ418 is a promising antischistosomal lead compound.

In vitro and in vivo activity of 3-alkoxy-1,2-dioxolanes against Schistosoma mansoni.

OBJECTIVES: Compounds characterized by a peroxidic skeleton are an interesting starting point for antischistosomal drug discovery. Previously a series of 3-alkoxy-1,2-dioxolanes, which are chemically stable cyclic peroxides, demonstrated significant in vitro activity against Plasmodium falciparum. We aimed to evaluate the potential of these compounds against Schistosoma mansoni and elucidate the roles of iron and peroxidic groups in activity. METHODS: Drugs were tested against juvenile and adult stages of S. mansoni in vitro and in vivo. Selected structures were assessed in vitro against schistosomes in the presence of additional iron sources. In addition, drugs were tested in vitro and in vivo against Echinostoma caproni, a non-blood-feeding intestinal fluke. Finally, the activity of non-peroxidic analogues was evaluated. RESULTS: Three dioxolanes displayed IC50s ≤ 20.1 µM against adult schistosomes and values as low as 4.2 µM against newly transformed schistosomula. Nonetheless, only moderate, non-significant worm burden reductions were observed after treatment of mice harbouring adult infections. Drugs lacked activity against juvenile schistosomes in vivo. Two selected dioxolanes showed in vitro activity against E. caproni down to concentrations of 5 mg/L, but none of the compounds revealed in vivo activity. All tested non-peroxidic analogues lacked activity in vitro against both parasites. CONCLUSIONS: Selected dioxolanes presented interesting in vitro activity, but low in vivo activities have to be overcome to identify a lead candidate. Although the inactivity of non-peroxidic analogues underlines the necessity of a peroxide functional group, incubation of adult schistosomes with additional iron sources did not alter activity, supporting an iron-independent mode of activation.

Antiparasitic drugs for paediatrics: systematic review, formulations, pharmacokinetics, safety, efficacy and implications for control.

Drug development for paediatric applications entails a number of challenges, such as the wide age spectrum covered - from birth to adolescence - and developmental changes in physiology during biological maturation that influence the efficacy and toxicity of drugs. Safe and efficacious antiparasitic drugs for children are of pivotal importance given the large proportion of burden attributable to parasitic diseases in this age group, and growing efforts to administer, as widely as possible, antiparasitic drugs to at-risk populations, such as infants and school-aged children, often without prior diagnosis. The purpose of this review is to investigate whether antiparasitic drugs have been adequately studied for use in paediatrics. We approached this issue through a systematic review using PubMed and the Cochrane Central Register of Trials covering a period of 10 years and 8 months until the end of August 2010 to identify trials that investigated efficacy, safety and pharmacokinetic (PK) parameters of antiparasitic drugs for paediatrics. Overall, 269 clinical drug trials and 17 PK studies met our inclusion criteria. Antimalarial drugs were the most commonly studied medicines (82·6%). Most trials were carried out in Africa and children aged 2-11 years were the age group most often investigated. Additionally, we critically examined available drug formulations for anthelminthics and identified a number of shortcomings that are discussed. Finally, we shed new light on current proposals to expand 'preventive chemotherapy' to preschool-aged children and emphasise that new research, including risk-benefit analyses, are needed before such a strategy can be adopted more widely.

Development of an in vitro drug sensitivity assay based on newly excysted larvae of Echinostoma caproni.

BACKGROUND: Echinostomiasis is one of the major food-borne trematodiases and the species Echinostoma caproni serves as a useful model for trematocidal drug discovery. The current in vitro drug sensitivity assay uses adult E. caproni worms that are incubated with candidate drugs and scored microscopically for viability at 72 hrs. The aim of this study was to investigate the use of newly excysted larvae (NEL) of E. caproni for in vitro drug testing, which would be faster, more cost effective and more ethical compared to adult worm assays. METHODS: Larvae were obtained by collecting metacercariae from snails and triggering their excystation using the trypsin-bile salt excystation method. Studies concerning various parameters of this chemical transformation process as well as appropriate NEL culturing conditions were carried out and findings evaluated. NEL and adult worms were incubated with praziquantel, tribendimidine, albendazole and quinine and evaluated microscopically 72 hrs post-incubation. In addition, the colorimetric markers resazurin, CellTiter-Glo® and Vybrant® were tested as an alternative assay read-out method. RESULTS: The chemical excystation method successfully induced E. caproni metacercariae to excyst at a rate of about 20-60%. NEL remained viable in culture medium for 5-7 days. The results of an in vitro drug assay using NEL mirrored the results of an assay using adult worms incubated with the same drugs. None of the markers could reliably produce signals proportional to NEL viability or cytotoxicity without significant complications. CONCLUSION: NEL are adequate for in vitro drug testing. Challenges remain in further improving the excystation yield and the practicability of the assay setup. Resolving these issues could also improve read-outs using colorimetric markers. Using NEL is in alignment with the 3 R rules of the ethical use of laboratory animals and can greatly increase the rate and affordability with which drugs are screened in vitro against this intestinal trematode.

Diagnosis and treatment of schistosomiasis in children in the era of intensified control.

In the current era of intensified and integrated control against schistosomiasis and other neglected tropical diseases, there is a need to carefully rethink and take into consideration disease-specific issues pertaining to the diagnosis, prevention, control and local elimination. Here, we present a comprehensive overview about schistosomiasis including recent trends in the number of people treated with praziquantel and the latest developments in diagnosis and control. Particular emphasis is placed on children. Identified research needs are offered for consideration; namely, expanding our knowledge about schistosomiasis in preschool-aged children, assessing and quantifying the impact of schistosomiasis on infectious and noncommunicable diseases, developing new antischistosomal drugs and child-friendly formulations, designing and implementing setting-specific control packages and developing highly sensitive, but simple diagnostic tools that are able to detect very light infections in young children and in people living in areas targeted for schistosomiasis elimination.

In vitro metabolic profile and in vivo antischistosomal activity studies of (η(6)-praziquantel)Cr(CO)3 derivatives.

In vitro metabolic behavior was investigated for two chromium tricarbonyl derivatives of the antischistosomal drug praziquantel (PZQ) with the formula (η(6)-PZQ)Cr(CO)3 (1 and 2), by use of human liver microsomes. The metabolic profiles of the derivatives differ significantly. The optically pure (η(6)-PZQ)Cr(CO)3 derivatives (S, Sp)-1, (R, Rp)-1, (S, Rp)-2, and (R, Sp)-2 were also prepared to assess the eudysmic ratios of 1 and 2 against Schistosoma mansoni in vitro. A strong enantioselective antischistosomal activity was observed. The R-enantiomers are highly active against adult schistosomes in vitro (IC50 0.08-0.13 µM), whereas both S-enantiomers lack activity. The in vivo activity of 1 and 2 was then studied in mice harboring a chronic S. mansoni infection. A single dose of 1 and 2 (400 mg/kg) resulted in low worm burden reductions of 24% and 29% (p > 0.05).

Development of an in vitro drug screening assay using Schistosoma haematobium schistosomula.

BACKGROUND: The development of novel antischistosomal drugs is crucial, as currently no vaccine and only a single drug is available for the treatment of schistosomiasis. Fast and accurate in vitro assays are urgently needed to identify new drug candidates and research efforts should include Schistosoma haematobium. The aim of the present study was to develop a S. haematobium drug sensitivity assay based on newly transformed schistosomula (NTS). METHODS: We first undertook comparative studies on the cercarial emergence rhythms of the intermediate host snails Biomphalaria glabrata (S. mansoni) and Bulinus truncatus (S. haematobium). Two transformation methods as well as three purification methods were studied on S. haematobium cercariae in order to produce a large number of viable and clean NTS. Known antischistosomal drugs were tested in the established NTS assay in vitro. Drug effects were evaluated either microscopically or fluorometrically, using a resazurin based viability marker. Microscopically obtained IC50 values were compared with results obtained for S. mansoni. RESULTS: A circadian rhythm existed in both snail species. Infected B. truncatus snails shed less cercariae than B. glabrata during the testing period. The highest transformation rate (69%) of S. haematobium cercariae into NTS was obtained with the vortex transformation (mechanical input) and the highest purification factor was observed using Percoll®. The fluorimetric readout based on resazurin was very precise in detecting dead or/and severely damaged schistosomula. CONCLUSIONS: With the use of viability markers such as resazurin, drug screening assays using S. haematobium NTS can be efficiently performed. However, drugs acting on the morphology and motility of S. haematobium NTS, such as metrifonate are missed. Drug sensitivity assays with NTS of both species, S. haematobium and S. mansoni, showed very similar results using known antischistosomal drugs. The S. mansoni NTS assay might be more suitable as primary screen in drug discovery efforts, which ultimately aim for a broad-spectrum antischistosomal drug as a larger number of S. mansoni NTS can be generated.

Ferrocenyl derivatives of the anthelmintic praziquantel: design, synthesis, and biological evaluation.

The design, synthesis, and biological evaluation of 18 ferrocenyl derivatives (4A-12A and 4B-12B) of the most well-known drug against schistosomiasis, namely praziquantel (PZQ), are reported. These compounds, which have been all isolated as racemates, were unambiguously characterized by ¹H and ¹³C NMR spectroscopy, mass spectrometry, and elemental analysis as well as by X-ray crystallography for 4A, 5A, and 7A. Cytotoxicity studies revealed that the complexes were moderately toxic toward a cervical cancer cell line (HeLa) and, importantly, significantly less active toward a noncancerous cell line (MRC-5). The in vitro anthelmintic activity of the 18 ferrocenyl PZQ derivatives was tested against adult Schistosoma mansoni, and values in the micromolar range (26-68 µM) were determined for the four most active compounds. It was also demonstrated using two compounds of the series as models (8A and 8B) that the complexes were stable when incubated for 24 h at 37 °C in human plasma.

Identification of antischistosomal leads by evaluating bridged 1,2,4,5-tetraoxanes, alphaperoxides, and tricyclic monoperoxides.

Although antischistosomal properties of peroxides were studied in recent years, systematic structure-activity relationships have not been conducted. We evaluated the antischistosomal potential of 64 peroxides belonging to bridged 1,2,4,5-tetraoxanes, alphaperoxides, and tricyclic monoperoxides. Thirty-nine compounds presented IC50 values <15 µM on newly transformed schistosomula. Active drugs featured phenyl-, adamantane-, or alkyl residues at the methylene bridge. Lower susceptibility was documented on adult schistosomes, with most hit compounds being tricyclic monoperoxides (IC50: 7.7-13.4 µM). A bridged 1,2,4,5-tetraoxane characterized by an adamantane residue showed the highest activity (IC50: 0.3 µM) on adult Schistosoma mansoni . Studies with hemin and heme supplemented medium indicated that antischistosomal activation of peroxides is not necessarily triggered by iron porphyrins. Two compounds (tricyclic monoperoxide; bridged 1,2,4,5-tetraoxane) revealed high worm burden reductions in the chronic (WBR: 75.4-82.8%) but only moderate activity in the juvenile (WBR: 18.9-43.1%) S. mansoni mouse model. Our results might serve as starting point for the preparation and evaluation of related derivatives.

Prioritising the prevention of medication handling errors.

OBJECTIVE: Medication errors are frequent in a hospital setting and often caused by inappropriate drug handling. Systematic strategies for their prevention however are still lacking. We developed and applied a classification model to categorise medication handling errors and defined the urgency of correction on the basis of these findings. SETTING: Nurses on medical wards (including intensive and intermediate care units) of a 1,680-bed teaching hospital. METHOD: In a prospective observational study we evaluated the prevalence of 20 predefined medication handling errors on the ward. In a concurrent questionnaire survey, we assessed the knowledge of the nurses on medication handling. The severity of errors observed in individual areas was scored considering prevalence, potential risk of an error, and the involved drug. These scores and the prevalence of corresponding knowledge deficits were used to define the urgency of preventive strategies according to a four-field decision matrix. MAIN OUTCOME MEASURE: Prevalence and potential risk of medication handling errors, corresponding knowledge deficits in nurses committing the errors, and priority of quality improvement. RESULTS: In 1,376 observed processes 833 medication handling errors were detected. Errors concerning preparation (mean 0.88 errors per observed process [95% CI: 0.81-0.96], N = 645) were more frequent than administration errors (0.36 [0.32-0.41], N = 701, P < 0.001). Parenteral drugs (1.10 [1.00-1.19], N = 492) were more often involved in errors than enteral drugs (0.32 [0.28-0.36], N = 794, P < 0.001). Of the 833 observed medication errors 30.9% concerned processes of high risk, 19.0% of moderate risk, and 50.1% of low risk. Of these errors 11.4% were caused by critical dose drugs, 81.6% by uncomplicated drugs, and 6.9% by nutritional supplements or diluents without active ingredient. According to the decision matrix that also considered knowledge deficits two error types concerning enteral drugs (flaws in light protection and prescribing information) were given maximum priority for quality improvement. For parenteral drugs five errors (incompatibilities, flaws in hygiene, duration of administration, check for visible abnormalities, and again prescribing information) appeared most important. CONCLUSION: We successfully applied a newly developed classification model to prioritise medication handling errors for prevention strategies.