Small change, big difference: A promising praziquantel derivative designated P96 with broad-spectrum antischistosomal activity for chemotherapy of schistosomiasis japonica.

BACKGROUND: Praziquantel (PZQ) has been the first line antischistosomal drug for all species of Schistosoma, and the only available drug for schistosomiasis japonica, without any alternative drugs since the 1980s. However, PZQ cannot prevent reinfection, and cannot cure schistosomiasis thoroughly because of its poor activity against juvenile schistosomes. In addition, reliance on a single drug is extremely dangerous, the development and spread of resistance to PZQ is becoming a great concern. Therefore, development of novel drug candidates for treatment and control of schistosomiasis is urgently needed. METHODOLOGYS/PRINCIPAL FINDINGS: One of the PZQ derivative christened P96 with the substitution of cyclohexyl by cyclopentyl was synthesized by School of Pharmaceutical Sciences of Shandong University. We investigated the in vitro and in vivo activities of P96 against different developmental stages of S. japonicum. Parasitological studies and scanning electron microscopy were used to study the primary action characteristics of P96 in vitro. Both mouse and rabbit models were employed to evaluate schistosomicidal efficacy of P96 in vivo. Besides calculation of worm reduction rate and egg reduction rate, quantitative real-time PCR was used to evaluate the in vivo antischistosomal activity of P96 at molecular level. In vitro, after 24h exposure, P96 demonstrated the highest activities against both juvenile and adult worm of S. japonicum in comparison to PZQ. The antischistosomal efficacy was concentration-dependent, with P96 at 50µM demonstrating the most evident schistosomicidal effect. Scanning electron microscopy demonstrated that P96 caused more severe damages to schistosomula and adult worm tegument compared to PZQ. In vivo, our results showed that P96 was effective against S. japonicum at all developmental stages. Notably, its efficacy against young stage worms was significantly improved compared to PZQ. Moreover, P96 retained the high activity comparable to PZQ against the adult worm of S. japonicum. CONCLUSIONS: P96 is a promising drug candidate for chemotherapy of schistosomiasis japonica, which has broad spectrum of action against various developmental stage, potentially addressing the deficiency of PZQ. It might be promoted as a drug candidate for use either alone or in combination with PZQ for the treatment of schistosomiasis.

Could we expect new praziquantel derivatives? A meta pharmacometrics/pharmacoinformatics analysis of all antischistosomal praziquantel derivatives found in the literature.

Praziquantel (PZQ) is the first line drug for the treatment of human Schistosoma spp. worm infections. However, it suffers from low activity towards immature stages of the worm, and its prolonged use induces resistance/tolerance. During the last 40 years, 263 PZQ analogues have been synthesized and tested against Schistosoma spp. worms, but less than 10% of them showed significant activity. Here, we propose a rationalization of the chemical space of the PZQ derivatives by a ligand-based approach. First, we constructed an in-house database with all PZQ derivatives available in the literature. This analysis shows a high heterogeneity in the data. Fortunately, all studies include PZQ as a reference, permitting the classification of compounds into three classes according to their activities. Models involving ligand-based pharmacophore and logistic regression were performed. Five physicochemical parameters were identified as the best to explain the biological activity. In the end, we proposed new PZQ derivatives with modifications at positions 1 and 7, we analysed them with our models, and we observed that they can be more active than the previously synthesized derivatives. The main goal of this work was to conduct the most valuable meta-pharmacometrics/pharmacoinformatics analysis with all Praziquantel medicinal chemistry data available in the literature.

Selective Depletion of Chiral 4-Hydroxypraziquantel Metabolites in Three Types of Aquaculture Fish by LC-MS/MS.

The rise of aquaculture has necessitated the use of antibiotics and other agents in these densely populated and often closed environments. An enantioselective depletion study of four chiral 4-hydroxypraziquantel metabolites (4-OH-PZQ) in perch, tilapia, and ricefield-eel muscles was done using a simple, sensitive, and reliable liquid-chromatography-tandem-mass-spectrometry (LC-MS/MS) method. These metabolites result from the uptake of the drug praziquantel (PZQ), which is used in aquaculture. A novel strategy of using a C18 short column in tandem with a chiral hydroxypropyl-ß-cyclodextrin superficially porous particle (CDShell-RSP) column produced the optimal separation for both the enantiomers and diastereoisomers of 4-OH-PZQ. The method was linear over the concentration range of 1-250 µg L-1 ( r2 ≥ 0.99) for R- trans-4-OH-PZQ, S- trans-4-OH-PZQ, R- cis-4-OH-PZQ, and S- cis-4-OH-PZQ. The average recoveries of four analytes at three spiked levels of 1, 10, and 100 µg kg-1 ranged from 84.2 to 93.1%, and the intraday and interday relative standard deviations were less than 7.9%. The limits of quantification of the four 4-OH-PZQ metabolites in perch-, tilapia-, and ricefield-eel-muscle matrices were 1.0 µg kg-1. The method was utilized to monitor the depletion of trans- and cis-4-OH-PZQ enantiomers in perch, tilapia, and ricefield-eel muscle following oral administration (medicine bath for ricefield eel). Species-specific differences in the PZQ metabolism of isomers were observed. In addition, new metabolites of PZQ were observed: 3-hydroxypraziquantel diastereomers.

Praziquantel Resistance in the Zoonotic Cestode Dipylidium caninum.

Dipylidium caninum is a cosmopolitan cestode infecting dogs, cats, and humans. Praziquantel is a highly effective cestocidal drug and resistance in adult cestodes has not been reported. From 2016 to 2018, a population of dogs with cestode infections that could not be eliminated despite multiple treatments with praziquantel or epsiprantel was identified. Cases of D. caninum were clinically resistant to praziquantel and could not be resolved despite increasing the dose, frequency, and duration of treatment. Resistant isolates were identified and characterized by sequencing the 28S, 12S, and voltage-gated calcium channel beta subunit genes. Cases were only resolved following treatment with nitroscanate or a compounded pyrantel/praziquantel/oxantel product. Clinicians should be aware of this alarming development as treatment options for cestodes are limited in both human and veterinary medicine.

In vitro and in vivo activity of R- and S- praziquantel enantiomers and the main human metabolite trans-4-hydroxy-praziquantel against Schistosoma haematobium.

BACKGROUND: Praziquantel (PZQ) is the mainstay of schistosomiasis control and has been successfully used for decades. However, its mechanism of action is not fully understood. While the majority of studies have been conducted on Schistosoma mansoni, it is not known which enantiomer, R- or S-praziquantel (R-/S-PZQ), is responsible for the activity on Schistosoma haematobium. METHODS: In vitro and in vivo studies were conducted to evaluate the activity of R- and S-PZQ, racemic PZQ and the main human metabolite, namely trans-4-OH-PZQ, on S. haematobium. IC50 values on adult S. haematobium were determined in vitro. Dose-response relationship studies were performed in golden Syrian hamsters, harbouring a chronic S. haematobium infection. RESULTS: R-PZQ displayed the highest activity against adult worms in vitro, revealing an IC50 of 0.007 µg/ml at 4 h and 0.01 µg/ml at 72 h. In contrast, S-PZQ was 501× less active (eudysmic ratio at 4 h), with an IC50 of 3.51 and 3.40 µg/ml (4 and 72 h, respectively). Racemic PZQ and trans-4-OH-PZQ resulted in an IC50 of 0.03 µg/ml and 1.47 µg/ml both at 4 and 72 h, respectively. In vivo, R-PZQ was the most potent drug with worm burden reductions (WBRs) of 98.5, 75.6 and 73.3% at 125.0, 62.5 and 31.0 mg/kg, respectively. A single oral dose of 250.0 mg/kg PZQ resulted in a WBR of 99.3%. S-PZQ was highly active in vivo at 250.0 and 500.0 mg/kg with WBRs of 83.0 and 94.1%, respectively. The lowest tested dose of S-PZQ, 125.0 mg/kg, showed moderate activity (WBR of 46.7%). The calculated ED50 for R- and S-PZQ were 24.7 and 127.6 mg/kg, respectively, with a corresponding eudysmic ratio of 5.17. CONCLUSION: Our data support the theory of R-PZQ driving the antischistosomal activity. Interestingly, also S-PZQ proved to possess a significant activity towards S. haematobium, particularly in vivo.

Praziquantel for Schistosomiasis: Single-Drug Metabolism Revisited, Mode of Action, and Resistance.

Schistosomiasis, a major neglected tropical disease, affects more than 250 million people worldwide. Treatment of schistosomiasis has relied on the anthelmintic drug praziquantel (PZQ) for more than a generation. PZQ is the drug of choice for the treatment of schistosomiasis; it is effective against all major forms of schistosomiasis, although it is less active against juvenile than mature parasites. A pyrazino-isoquinoline derivative, PZQ is not considered to be toxic and generally causes few or transient, mild side effects. Increasingly, mass drug administration targeting populations in sub-Saharan Africa where schistosomiasis is endemic has led to the appearance of reduced efficacy of PZQ, which portends the selection of drug-resistant forms of these pathogens. The synthesis of improved derivatives of PZQ is attracting attention, e.g., in the (i) synthesis of drug analogues, (ii) rational design of pharmacophores, and (iii) discovery of new compounds from large-scale screening programs. This article reviews reports from the 1970s to the present on the metabolism and mechanism of action of PZQ and its derivatives against schistosomes.

Design, synthesis and biological evaluation of praziquantel and endoperoxide conjugates as antischistosomal agents.

BACKGROUND: The widespread use of praziquantel for the treatment of schistosomiasis has led to concerns over the potential development of drug resistance. Therefore, the discovery of novel antischistosomal agents is imperative. In this study, a series of praziquantel and endoperoxide conjugates were synthesized and evaluated as potential antischistosomal agents. RESULTS: Some compounds exhibited high efficacy against both adult and juvenile Schistosoma, in in vitro studies. Structure-activity relationship (SAR) analysis revealed that compounds with amide bond linker and cyclopentyl adjacent to the 1,2,4,5-tetraxane pharmacophore displayed the highest efficacy. Overall, compounds showed consistent activity against Schistosoma japonicum and Schistosoma mansoni. In vivo study resulted in moderate but statistically significant activity. CONCLUSION: Important preliminary results were obtained from thorough activity evaluation of praziquantel-endoperoxide conjugates. Further pharmacokinetic property investigation is necessary to improve in vivo efficacy.

Toward organometallic antischistosomal drug candidates.

In the recent years, there has been a growing interest in the use of novel approaches for the treatment of parasitic diseases such as schistosomiasis. Among the different approaches used, organometallic compounds were found to offer unique opportunities in the design of antiparasitic drug candidates. A ferrocenyl derivative, namely ferroquine, has even entered clinical trials as a novel antimalarial. In this short review, we report on the studies describing the use of organometallic compounds against schistosomiasis.

Development of chiral praziquantel analogues as potential drug candidates with activity to juvenile Schistosoma japonicum.

A series of chiral praziquantel analogues were synthesized and evaluated against Schistosoma japonicum both in vitro and in vivo. All compounds exhibited low to considerable good activity in vivo. Remarkably, worm reduction rate of R-3 was 60.0% at a single oral dose of 200mg/kg against juvenile stage of Schistosoma japonicum. The target compounds displayed in vivo antischistosomal activity against both Schistosoma japonicum and Schistosoma mansoni. Furthermore, all R-isomers displayed stronger antischistosomal activity than S-isomers in vivo, indicating R-isomers were the active enantiomers, while S-isomers were less active ones. This structure activity relationship (SAR) could have important implications in further drug development for schistosomiasis.

Synthesis and SAR studies of praziquantel derivatives with activity against Schistosoma japonicum.

The synthesis and structure-activity relationship (SAR) studies of praziquantel derivatives with activity against adult Schistosoma japonicum are described. Several of them showed better worm killing activity than praziquantel and could serve as leads for further optimization.

Praziquantel derivatives with antischistosomal activity: aromatic ring modification.

A series of aromatic ring-modified praziquantel derivatives were prepared and evaluated against juvenile and adult stage of Schistosoma japonicumin. Several analogs comparable in activity to the drug praziquantel have been identified based on in vitro and in vivo japonuicum schistosomes worm viability assay. Structure and activity relationship of these praziquantel aromatic ring-modified compounds was revealed. Specifically, a compound in which a bromine has been introduced in the aromatic ring of praziquantel demonstrated close antischistosomal activity to praziquantel in vivo.

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.

Efficacy of praziquantel and artemisinin derivatives for the treatment and prevention of human schistosomiasis: a systematic review and meta-analysis.

BACKGROUND: Praziquantel has been used as first-line drug for chemotherapy of schistosomiasis since 1984. Besides praziquantel, artemether and artesunate have also been used for the control of this infectious disease since late 1990s. In this article, we conducted a systematic review and meta-analysis to evaluate the antischistosomal efficacy of different medication strategies including monotherapy or combination therapies of these drugs. RESULTS: A number of 52 trials from 38 articles published in peer-reviewed journals before July 2011 were selected for analysis after searching the following literature databases: the Cochrane Library, PubMed/Medline, ISI Web of Science, Chinese Biomedicine Literature Database, and China National Knowledge Infrastructure. Our meta-analyses showed that a dosage of 30-60 mg/kg praziquantel compared with placebo produced a protection rate of about 76% (95% CI: 67%-83%) for treating human schistosomiasis, which varied from 70% to 76% with no significant differences among the subspecies S. haematobium, S. japonicum or S. mansoni. Protection rates were higher when praziquantel doses were elevated, as concluded from the nRCTs results: the protection rate of praziquantel at 40 mg/kg was 52% (95% CI: 49%-55%), and it increased to 91% (95% CI: 88%-92%) when the dosages were elevated to 60/80/100 mg/kg divided two or more doses. Multiple doses of artemether or artesunate over 1- or 2-week intervals resulted in protection rates of 65% to 97% for preventing schistosomiasis, and increased doses and shorter medication intervals improved their efficacies. Praziquantel and artemisinin derivatives (artemether or artesunate) in combination resulted in a higher protection rate of 84% (95% CI: 64%-91%) than praziquantel monotherapy for treatment. praziquantel and artesunate in combination had a great protection rate of 96% (95% CI: 78%-99%) for preventing schistosomes infection. CONCLUSIONS: According to the results, praziquantel remains effective in schistosomiasis treatment, and multiple doses would improve its efficacy; meanwhile, praziquantel is also a good drug for preventing acute schistosomiasis morbidity. It's better to use multiple doses of artemether or artesunate with 1- or 2-week intervals for prevention against schistosome infection. Praziquantel and artemether or artesunate in combination perform better in treatment than praziquantel monotherapy, and they are especially suitable for treating the patients with repeated exposure to infected water.

Metabolite profiling of praziquantel and its analogs during the analysis of in vitro metabolic stability using information-dependent acquisition on a hybrid triple quadrupole linear ion trap mass spectrometer.

Rapid determination of in vitro metabolic stability and metabolite profiling of new chemical entities using microsomes or other liver preparations is one of the most important steps in drug discovery. In this paper, we report the use of liquid chromatography-hybrid triple quadrupole/linear ion trap mass spectrometry for the simultaneous analysis of metabolic stability, metabolite profiling, and the kinetics of metabolite formation of praziquantel and three structural analogs. Multiple reaction monitoring (MRM) scans were used to quantify the disappearance of parent compounds and the formation of metabolites. MRM-information dependent acquisition-enhanced product ion (MRM-IDA-EPI) scans were used for the identification of the metabolites formed. Metabolic stability of these anthelmintics were studied in human liver microsomes (HLM) using MRM as a survey scan, which resulted in the identification of a higher number of metabolites compared to neutral loss (NL), precursor ion (PI), and enhanced mass spectrometry (EMS) scans. MRM-IDA-EPI scans resulted in the generation of similar calibration curves to MRM-only quantitative analysis. Therefore, the quantitative capabilities of the method was not affected by the additional qualitative information obtained during the same run. The formation of major metabolites was also simultaneously monitored, which could be used to understand the kinetics and mechanism of metabolite formation. Finally, our data demonstrate that the three analogs had higher metabolic stability than the anthelmintic prototype (praziquantel).

Enantioselective analysis of praziquantel and trans-4-hydroxypraziquantel in human plasma by chiral LC-MS/MS: Application to pharmacokinetics.

A simple enantioselective method for the determination of praziquantel (PZQ) and trans-4-hydroxypraziquantel (4-OHPZQ) in human plasma was developed and validated by high-performance liquid chromatography/mass spectrometry. The plasma samples were prepared by liquid-liquid extraction using a mixture of methyl-tert-butylether/dichloromethane (2:1, v/v) as extraction solvent. The direct resolution of PZQ and 4-OHPZQ enantiomers was performed on a Chiralpak AD column using hexane-isopropanol (75:25, v/v) as the mobile phase. Diazepam was used as internal standard. The method described here is simple and reproducible. The quantitation limit of 1.25ng/ml for each PZQ enantiomer and of 12.5ng/ml for each 4-OHPZQ enantiomer permits the use of the method in studies investigating the kinetic disposition of a single dose of 1.5g racemic PZQ. Enantioselectivity in the kinetic disposition of PZQ and 4-OHPZQ was observed in the clinical study, with the demonstration of a higher proportion of the (+)-(S)-PZQ and (-)-(R)-4-OHPZQ enantiomers in plasma.

Praziquantel derivatives I: Modification of the aromatic ring.

Several analogues of the potent anthelmintic praziquantel were prepared with variation in the aromatic ring. The biological activity of these analogues was evaluated and compared against known analogues. Amination of the ring was tolerated while other variations were not. These results have important implications for drug development for schistosomiasis.

Human fascioliasis.

Fasciola hepatica, a zoonotic liver fluke, can also cause disease in humans. Common symptoms are epigastric pain, upper abdominal pain and malaise. Fever and arthralgia are common in acute fascioliasis. Eosinophilia is the predominant laboratory finding, especially in patients with the acute form of the disease. Diagnosis and treatment is not easy, as physicians rarely encounter this disease, and effective drugs are not available in many countries. Human fascioliasis may be underestimated. Patients with eosinophilia and abdominal pain should be evaluated for F. hepatica infestation by parasitological, radiological and serological tests.

[Efficacy of the Russian anthelmintic agent trichlorophen]. / Potentsiruiushchie effecty otechestvennogo antigel'mintika trikhlofena.

Experiments have established the high efficacy of combinations of the micronized dosage form of trichlorophen, with albendazole or medamine in treating trichocephaliasis (its causative agent being Trichocephalus muris) in DBA/2st mice and that of trichlorophen in combination with azinox or fenasal in outbred albino mice with hymenolepiasis (its causative agent being Hymenolepis nana). These combinations are promising in treating patients with cestodosis and nemadosis, respectively.

[Impact of anthelminthic therapy for opisthorchiasis on the biochemical parameters of hepatic function]. / Effekt terapii na biokhimicheskie pokazateli funktsii pecheni pri opistorkhoze.

A response of a complex of biochemical parameters of hepatic function to therapeutic exposures was studied at different stages of development of Opisthorchis invasion. The activity of AST, ALT, GGT, GGT, AP, AM, and CE and the concentration of bilirubin, cholesterol, and glucose in the sera from 232 patients with acute or chronic opisthorchiasis were studied. Their study was conducted in several steps: before treatment, after a course of pathogenetic therapy, 1-3 days after antihelminthic therapy with bilthricide and azinox, in early (following 1-3 months) and late (following more than 6 months) residual periods. Pathogenetic therapy was found to alleviate an acute inflammatory process in the liver, but without eliminating cholestasis completely. Antihelminthic therapy improved the results of hepatic tests in different periods after treatment for acute or chronic opisthorchiasis in relation to the rate of compensation of structural lesions. By and large, after pathogenetic and antihelminthic therapy for opisthorchiasis the parameters characterizing the cytolytic syndrome became more rapidly than those that reflect the biliary system. However, there was no complete recovery of impaired hepatic and pancreatic functions throughout the follow-up.