Drug Repurposing for Schistosomiasis: Combinations of Drugs or Biomolecules

Efficacy and safety of praziquantel plus artemisinin-based combinations versus praziquantel in the treatment of Kenyan children with Schistosoma mansoni infection: open-label, randomized, head-to-head, non-inferiority trial

Praziquantel alone is insufficient for the control of schistosomiasis due to poor efficacy against juvenile worms and increasing concerns about the risk of drug resistance. We compared the efficacy and safety of praziquantel combined with four different artemisinin-based combinations to praziquantel alone in treating Schistosoma mansoni infection in Kenyan children. In this randomized, open-label, five-arm, head-to-head, non-inferiority trial, children (aged 9-15 years) with S. mansoni infection according to duplicate Kato Katz thick smears from a stool sample in the Mwea irrigation scheme of central Kenya, were enrolled. Participants were randomly assigned (1:1:1:1:1) via a computer-generated block randomization procedure to receive a single oral dose of praziquantel (PZQ) (40 mg/kg/day) alone or in combination with a 3-day course (4 mg/kg of artesunate) of artesunate plus sulfalene-pyrimethamine (As + SP), artesunate plus amodiaquine (As + AQ), artesunate plus mefloquine (As + MQ) or dihydroartemisinin-piperaquine (DHAP). Laboratory technicians were masked to treatment allocation, but participants, clinicians, and study nurses were not. The primary outcomes were the cure rate and frequency of adverse events, which were assessed 6 weeks after treatment in the available case population using a per-protocol analysis. The non-inferiority margin was set at -10% for the risk difference in cure rates between combination therapy and PZQ alone. Between 12 September 2018 and 11 January 2019, 540 participants were assigned to receive PZQ alone (n = 108), PZQ plus As + SP (n = 108), PZQ plus As + AQ (n = 108), PZQ plus As + MQ (n = 108), or PZQ plus DHAP (n = 108). Primary outcome data were available for 523 (96.9%) participants. The cure rate was 82.5% (85/103) in PZQ alone, 81.7% (85/104) in PZQ plus As + SP, 76.2% (80/105) in PZQ plus As + AQ, 88.7% (94/106) in PZQ plus As + MQ, and 85.7% (90/105) in PZQ plus DHAP arm. Non-inferiority was declared for PZQ plus As + MQ (difference 6.2 [95% confidence interval: -3.3 to 15.6]) and PZQ plus DHAP (3.2 [-6.7 to 13.1]) but not for PZQ plus As + SP (-0.8 [-11.2 to 9.6]) or PZQ plus As + AQ (-6.3 [-17.3 to 4.6]). Adverse events were reported by 26% (138/540) of participants, including abdominal pain, headache, and vomiting. There were no serious adverse events. Alternatives to praziquantel should include praziquantel plus artesunate-mefloquine or praziquantel plus dihydroartemisinin-piperaquine. However, further multicentre trials are needed in different epidemiological settings and population groups to confirm these findings.CLINICAL TRIALSThis study is registered with the Pan-African Clinical Trials Registry under PACTR202001919442161.

Impact of nanostructured formulations for schistosomiasis treatment: a systematic review of in vivo preclinical evidence

BACKGROUND

Schistosomiasis is a neglected tropical disease caused by Schistosoma sp., and praziquantel (PZQ) is the first-line treatment. However, traditional PZQ formulations have low solubility and fast metabolism, limiting its effectiveness. Thus, nanoparticles have been proposed to improve the bioavailability and efficacy of poorly soluble antischistosomal drugs.

AIMS

This systematic review used in vivo preclinical studies to map the available evidence and compare the efficacy of free PZQ and PZQ-based nanostructured formulations (N-PZQ) for schistosomiasis treatment.

METHODS

PubMed, Embase, Scopus, and Web of Science were searched, and 1186 experimental studies published between 1974 and 2024 were screened. Parasitological, histopathological, pharmacokinetic, and toxicological outcomes were evaluated.

RESULTS

Twelve relevant studies were identified exploring N-PZQ formulations based on liposomes, nanoliposomes, and nanocrystals. N-PZQ demonstrated better therapeutic efficacy than free PZQ, reducing parasite load, modifying oogram profiles, and down-regulating liver granuloma development (number and size). N-PZQ also exhibited improved pharmacokinetic profile, with enhanced bioavailability and longer half-life, as well as reduced toxicity (cytotoxicity, genotoxicity, and hepatotoxicity) compared to free PZQ.

CONCLUSION

PZQ-based nanostructured formulations represent a promising strategy to enhance schistosomiasis treatment by improving chemotherapy efficacy, optimizing antiparasitic responses, pharmacokinetics, and reducing drug toxicity.

Schistosomiasis Chemotherapy, Chemoprevention, and Vaccines: History, Progress, and Priorities

BACKGROUND

Schistosomiasis is a major human disease of public health importance. Freshwater snails serving as intermediary hosts and human interaction with surface water tainted by feces or urine are both necessary components of the transmission cycle. Schistosoma haematobium, Schistosoma mansoni, and Schistosoma japonicum are the primary pathogen species. Over 250 million individuals are infected globally, according to the World Health Organization, causing significant morbidity and an estimated loss of 1.9 million disability-adjusted life years, a number that is probably underestimated. Immunological protection is slowly built up through complex immunological systems, although innate factors also play a role. Chronic schistosomiasis affects mainly individuals residing in poor rural area. Vaccination is considered as one of the most sustainable options for the control of any pathogen, but schistosomiasis vaccine for humans or animals is not available till now despite the discovery of numerous potentially promising schistosome vaccine antigens.

OBJECTIVE

To provide an overview of the schistosomiasis chemotherapy, chemoprevention, and vaccines history and progress.

DESIGN

Review article.

DATA SOURCES

PubMed, ISI Web of Science, Science Direct, and the World Health Organization database.

CONCLUSION

Favorably praziquantel (PZQ) is a medication with excellent chemopreventive treatment compliance. Due to the extensive usage of PZQ, there is a great deal of debate surrounding the emergence of drug resistance. PZQ is effective against all species of schistosomes, schistosomiasis prevalence has remained largely unaffected, due to reinfection in high transmission areas and growing juvenile worms that were not affected by the drug, even though the need for a schistosomiasis vaccine is even more pressing.

Efficacy and safety of single-dose artesunate plus sulfalene/pyrimethamine combined with praziquantel for the treatment of children with Schistosoma mansoni or Schistosoma haematobium in western Kenya: a randomised, open-label controlled trial

BACKGROUND

Reliance on praziquantel for the treatment and control of schistosomiasis is likely to facilitate the emergence of drug resistance. Combination therapy targeting adult and juvenile schistosome worms is urgently needed to improve praziquantel efficacy and delay the potential development of drug resistance. We assessed the efficacy and safety of single-dose praziquantel combined with single-dose artesunate plus sulfalene-pyrimethamine in the treatment of Kenyan children with schistosomiasis.

METHODS

This was an open-label, randomised clinical trial involving 426 school-aged children (7-15 years old) diagnosed with Schistosoma mansoni (by Kato-Katz) or S. haematobium (by urine filtration). They were randomly assigned (1:1:1) to receive a single dose of praziquantel (40 mg/kg), a single dose of artesunate plus sulfalene-pyrimethamine (12 mg/kg artesunate) or combination therapy using a single dose of praziquantel (40 mg/kg) combined with a single dose of artesunate plus sulfalene-pyrimethamine (12 mg/kg artesunate). The primary outcome was cure and egg reduction rates at 6 weeks post-treatment in the available case population. Adverse events were assessed within 3 h after treatment.

RESULTS

Of the 426 children enrolled, 135 received praziquantel, 150 received artesunate plus sulfalene-pyrimethamine, and 141 received combination therapy. Outcome data were available for 348 (81.7%) children. For S. mansoni-infected children (n = 335), the cure rates were 75.6%, 60.7%, and 77.8%, and the egg reduction rates were 80.1%, 85.0%, and 88.4% for praziquantel, artesunate plus sulfalene-pyrimethamine, and combination therapy, respectively. For S. haematobium-infected children (n = 145), the corresponding cure rates were 81.4%, 71.1%, and 82.2%, and the egg reduction rates were 95.6%, 97.1%, and 97.7%, respectively. Seventy-one (16.7%) children reported mild-intensity adverse events. The drugs were well tolerated and no serious adverse events were reported.

CONCLUSIONS

A single oral dose of praziquantel combined with artesunate plus sulfalene-pyrimethamine cured a high proportion of children with S. haematobium but did not significantly improve the treatment efficacy for either urinary or intestinal schistosomiasis. Sequential administration of praziquantel and artesunate plus sulfalene-pyrimethamine may enhance the efficacy and safety outcomes.

Insights into the epidemiology, pathogenesis, and differential diagnosis of schistosomiasis

Schistosomiasis is a neglected tropical disease that is prevalent in low- and middle-income countries. There are five human pathogenic species, of which Schistosoma haematobium, Schistosoma mansoni and Schistosoma japonicum are the most prevalent worldwide and cause the greatest burden of disease in terms of mortality and morbidity. In addition, hybrid schistosomes have been identified through molecular analysis. Human infection occurs when cercariae, the larval form of the parasite, penetrate the skin of people while bathing in contaminated waters such as lakes and rivers. Schistosomiasis can cause both urogenital and intestinal symptoms. Urogenital symptoms include haematuria, bladder fibrosis, kidney damage, and an increased risk of bladder cancer. Intestinal symptoms may include abdominal pain, sometimes accompanied by diarrhoea and blood in the stool. Schistosomiasis affects more than 250 million people and causes approximately 70 million Disability-Adjusted Life Years (DALYs), mainly in Africa, South America, and Asia. To control infection, it is essential to establish sensitive and specific diagnostic tests for epidemiological surveillance and morbidity reduction. This review provides an overview of schistosomiasis, with a focus on available diagnostic tools for Schistosoma spp. Current molecular detection methods and progress in the development of new diagnostics for schistosomiasis infection are also discussed.

Targeting SmCB1: Perspectives and Insights to Design Antischistosomal Drugs

Neglected tropical diseases (NTDs) are prevalent in tropical and subtropical countries, and schistosomiasis is among the most relevant diseases worldwide. In addition, one of the two biggest problems in developing drugs against this disease is related to drug resistance, which promotes the demand to develop new drug candidates for this purpose. Thus, one of the drug targets most explored, Schistosoma mansoni Cathepsin B1 (SmCB1 or Sm31), provides new opportunities in drug development due to its essential functions for the parasite's survival. In this way, here, the latest developments in drug design studies targeting SmCB1 were approached, focusing on the most promising analogs of nitrile, vinyl sulphones, and peptidomimetics. Thus, it was shown that despite being a disease known since ancient times, it remains prevalent throughout the world, with high mortality rates. The therapeutic arsenal of antischistosomal drugs (ASD) consists only of praziquantel, which is widely used for this purpose and has several advantages, such as efficacy and safety. However, it has limitations, such as the impossibility of acting on the immature worm and exploring new targets to overcome these limitations. SmCB1 shows its potential as a cysteine protease with a catalytic triad consisting of Cys100, His270, and Asn290. Thus, design studies of new inhibitors focus on their catalytic mechanism for designing new analogs. In fact, nitrile and sulfonamide analogs show the most significant potential in drug development, showing that these chemical groups can be better exploited in drug discovery against schistosomiasis. We hope this manuscript guides the authors in searching for promising new antischistosomal drugs.

Schistosoma japonicum Associated Colorectal Cancer and Its Management

BACKGROUND

An association between Schistosoma japonicum and colorectal cancer in humans has been known since a long time; however, this association remains understudied and lacks comprehensive experimentation support.

OBJECTIVE

Various epidemiological and pathological studies have established the role of chronic inflammation as a major factor behind the induction of colorectal cancer. The aim of this review is to present the current knowledge on the association of Schistosoma japonicum with colorectal cancer.

RESULT

Mechanisms which lead to induction and progression of colorectal cancer are highlighted along with diagnosis and treatment for the same. Further, various methodologies, including mass drug administration, use of new drugs and vaccines, role of apoptosis, and histone-modifying enzymes, have been described which can either prevent the schistosomal infection itself or can check it from reaching an advanced stage.

CONCLUSIONS

Epidemiological, clinical, pathological and surgical studies suggest that Schistosoma japonicum is responsible for induction of colorectal cancer. However, thorough clinical studies are required to support and globally accept this notion. Further, methodologies highlighted in this work can be employed in order to take care of schistosomal infection or address the cancer induction and progression.

SCHISTOACT: a protocol for an open-label, five-arm, non-inferiority, individually randomized controlled trial of the efficacy and safety of praziquantel plus artemisinin-based combinations in the treatment of Schistosoma mansoni infection

BACKGROUND

Schistosomiasis control relies on praziquantel for preventive chemotherapy. Alternative drugs are needed for the treatment and control of schistosomiasis. Praziquantel is effective against adult schistosome worms but ineffective against larval stages of the parasite and cannot prevent re-infection or interrupt the transmission of infection. Continued reliance on praziquantel for wide-scale schistosomiasis control will likely accelerate the emergence of drug resistance. Artemisinin derivatives are effective against the juvenile stages but ineffective against adult worms. The SCHISTOACT study aimed to evaluate the efficacy and safety of praziquantel plus one of four artemisinin-based combinations in treating Schistosoma mansoni infection in Kenya.

METHODS

The SCHISTOACT study is an open-label, head-to-head, five-arm, proof-of-concept, non-inferiority, individually randomized controlled trial with a follow-up of 12 weeks. A total of 540 primary school-aged children from the Mwea area, Kirinyaga County in central Kenya, diagnosed with S. mansoni infection (by Kato-Katz method) are randomly allocated (1:1:1:1:1) to a single dose of praziquantel plus a 3-day course of artesunate-sulfalene/pyrimethamine, or artesunate-amodiaquine, or artesunate plus mefloquine, or dihydroartemisinin-piperaquine, or praziquantel control arm. The primary endpoints are efficacy (cure rate, assessed by microscopy) and safety (adverse events) of each study arm 6 weeks after treatment. Secondary endpoints include cumulative cure rate, egg reduction rate, and re-infection 12 weeks after treatment. The non-inferiority margin is set at - 10 for the risk difference in cure rates between praziquantel and the combined treatment.

DISCUSSION

This study assesses a strategy for repurposing artemisinin-based combination therapies (ACTs) for treating schistosomiasis. It adopts a head-to-head comparison of four different ACTs to test a non-inferiority hypothesis and to strengthen local capacity to conduct clinical trials for interventions against neglected tropical diseases.

TRIAL REGISTRATION

Pan-African Clinical Trials Registry PACTR202001919442161 . Retrospectively registered on 6 January 2020.

Mining host candidate regulators of schistosomiasis-induced liver fibrosis in response to artesunate therapy through transcriptomics approach

BACKGROUND

Artesunate (ART) has been reported to have an antifibrotic effect in various organs. The underlying mechanism has not been systematically elucidated. We aimed to clarify the effect of ART on liver fibrosis induced by Schistosoma japonicum (S. japonicum) in an experimentally infected rodent model and the potential underlying mechanisms.

METHODS

The effect of ART on hepatic stellate cells (HSCs) was assessed using CCK-8 and Annexin V-FITC/PI staining assays. The experimental model of liver fibrosis was established in the Mongolian gerbil model infected with S. japonicum cercariae and then treated with 20 mg/kg or 40 mg/kg ART. The hydroxyproline (Hyp) content, malondialdehyde (MDA) content, superoxide dismutase (SOD) and glutathione peroxidase (GPX) activities in liver tissue were measured and histopathological changes of liver tissues were observed. Whole-transcriptome RNA sequencing (RNA-seq) of the liver tissues was performed. Differentially expressed genes (DEGs) were identified using bioinformatic analysis and verified by quantitative PCR (qPCR) and western blot assay.

RESULTS

ART significantly inhibited the proliferation and induce the apoptosis of HSCs in a dose-dependent manner. In vivo, Hyp content decreased significantly in the ART-H group compared to the model (MOD) group and GPX activity was significantly higher in the ART-H group than in the MOD group. Besides, ART treatment significantly reduced collagen production (p <0.05). A total of 158 DEGs and 44 differentially expressed miRNAs related to ART-induced anti-schistosomiasis liver fibrosis were identified. The qPCR and western blot results of selected DEGs were consistent with the sequencing results. These DEGs were implicated in key pathways such as immune and inflammatory response, integrin-mediated signaling and toll-like receptor signaling pathways.

CONCLUSION

ART is effective against liver fibrosis using Mongolian gerbil model induced by S. japonicum infection. We identified host candidate regulators of schistosomiasis-induced liver fibrosis in response to ART through transcriptomics approach.

Nanoparticles as Potent Agents for Treatment of Schistosoma Infections: A Systematic Review

Background

Schistosomiasis is an acute and chronic parasitic disease caused by blood flukes of the genus Schistosoma. The current drugs for treating schistosomiasis are associated with some side effects.

Objective

The aim of this systematic study was an overview of the treatment of diseases caused by Schistosoma based on nanoparticles.

Methods

In the present systematic research with keywords "Schistosoma", "parasitism", "anti-Schistosoma activity", "nanoparticles", "metal nanoparticles", "silver nanoparticles", "gold nanoparticles", "polymer nanoparticles", "PLGA nanoparticles", "nanoemulsions", "in vitro", and "in vivo" from five English-language databases, including ScienceDirect, europePMC, PubMed, Scopus, Ovid, and Cochrane were searched from 2000 to 2022 by 2 researchers.

Results

In the initial search, 250 studies were selected. Based on the inclusion and exclusion criteria, 27 articles were finally selected after removing duplicate, unrelated, and articles containing full text. In present article, the most nanoparticles used against Schistosoma were gold nanoparticles (22%).

Conclusions

The results indicate the high potential of various nanoparticles, including metal nanoparticles, against Schistosoma. Also, the remarkable anti-schistosomal activity of nanoparticles suggests their use in different fields to eliminate this pathogenic microorganism so that it can be used as an effective candidate in the preparation of anti-schistosomal compounds because these compounds have fewer side effects than chemical drugs. Ther Res Clin Exp. 2023; XX:XXX-XXX).

Ex vivo and In vitro antiplasmodial activities of approved drugs predicted to have antimalarial activities using chemogenomics and drug repositioning approach

High malaria mortality coupled with increased emergence of resistant multi-drug resistant strains of Plasmodium parasite, warrants the development of new and effective antimalarial drugs. However, drug design and discovery are costly and time-consuming with many active antimalarial compounds failing to get approved due to safety reasons. To address these challenges, the current study aimed at testing the antiplasmodial activities of approved drugs that were predicted using a target-similarity approach. This approach is based on the fact that if an approved drug used to treat another disease targets a protein similar to Plasmodium falciparum protein, then the drug will have a comparable effect on P. falciparum. In a previous study, in vitro antiplasmodial activities of 10 approved drugs was reported of the total 28 approved drugs. In this study, six out of 18 drugs that were previously not tested, namely epirubicin, irinotecan, venlafaxine, palbociclib, pelitinib, and PD153035 were tested for antiplasmodial activity. The drug susceptibility in vitro assays against five P. falciparum reference strains (D6, 3D7, W2, DD2, and F32 ART) and ex vivo assays against fresh clinical isolates were done using the malaria SYBR Green I assay. Standard antimalarial drugs were included as controls. Epirubicin and irinotecan showed excellent antiplasmodial ex vivo activity against field isolates with mean IC50 values of 0.044 ± 0.033 μM and 0.085 ± 0.055 μM, respectively. Similar activity was observed against W2 strain where epirubicin had an IC50 value of 0.004 ± 0.0009 μM, palbociclib 0.056 ± 0.006 μM, and pelinitib 0.057 ± 0.013 μM. For the DD2 strain, epirubicin, irinotecan and PD 153035 displayed potent antiplasmodial activity (IC50 < 1 μM). Epirubicin and irinotecan showed potent antiplasmodial activities (IC50 < 1 μM) against DD2, D6, 3D7, and F32 ART strains and field isolates. This shows the potential use of these drugs as antimalarials. All the tested drugs showed antiplasmodial activities with IC50 values below 20 μM, which suggests that our target similarity-based strategy is successful at predicting antiplasmodial activity of compounds thereby circumventing challenges in antimalarial drug discovery.

Long non-coding RNAs are essential for Schistosoma mansoni pairing-dependent adult worm homeostasis and fertility

The trematode parasite Schistosoma mansoni causes schistosomiasis, which affects over 200 million people worldwide. Schistosomes are dioecious, with egg laying depending on the females' obligatory pairing with males. Long non-coding RNAs (lncRNAs) are transcripts longer than 200 nucleotides with low or no protein-coding potential that have been involved in other species with reproduction, stem cell maintenance, and drug resistance. In S. mansoni, we recently showed that the knockdown of one lncRNA affects the pairing status of these parasites. Here, we re-analyzed public RNA-Seq data from paired and unpaired adult male and female worms and their gonads, obtained from mixed-sex or single-sex cercariae infections, and found thousands of differentially expressed pairing-dependent lncRNAs among the 23 biological samples that were compared. The expression levels of selected lncRNAs were validated by RT-qPCR using an in vitro unpairing model. In addition, the in vitro silencing of three selected lncRNAs showed that knockdown of these pairing-dependent lncRNAs reduced cell proliferation in adult worms and their gonads, and are essential for female vitellaria maintenance, reproduction, and/or egg development. Remarkably, in vivo silencing of each of the three selected lncRNAs significantly reduced worm burden in infected mice by 26 to 35%. Whole mount in situ hybridization experiments showed that these pairing-dependent lncRNAs are expressed in reproductive tissues. These results show that lncRNAs are key components intervening in S. mansoni adult worm homeostasis, which affects pairing status and survival in the mammalian host, thus presenting great potential as new therapeutic target candidates.

Parasitological and histopathological studies to the effect of aqueous extract of Moringa oleifera Lam. leaves combined with praziquantel therapy in modulating the liver and spleen damage induced by Schistosoma mansoni to male mice

This study assessed the effectiveness of an aqueous extract of Moringa Oleifera Lam. leaves (MOL) alone or in combination with praziquantel (PZQ) drug targeting-infected mice with Schistosoma mansoni-induced liver and spleen damage. Mice were divided into eight groups control mice group treated orally with saline. PZQ group: non-infected mice treated orally with 300 mg/kg bwt PZQ three consecutive days. MOL group: non-infected mice treated orally with 150 mg/kg bwt MOL extract for 15 days. PZQ/ MOL group: non-infected mice treated orally with 300 mg/kg bwt PZQ for three consecutive days and 150 mg/kg bwt MOL extract for 15 days. IF group: infected mice with 100 cercariae/mouse of the Egyptian strain of S. mansoni. IF/PZQ group infected mice with S. mansoni cercariae and treated orally with 300 mg/kg bwt PZQ for three consecutive days. IF/MOL group: infected mice with S. mansoni cercariae treated orally with 150 mg/kg bwt MOL extract for 15 days. IF/PZQ +MOL group: infected mice with S. mansoni cercariae treated orally with 300 mg/kg bwt PZQ for three consecutive days and 150 mg/kg bwt MOL extract for 15 days. Blood, liver, spleen, worm, and eggs were collected at the end of the experimental period. Treatment of infected mice with MOL and PZQ together significantly reduced the number of ova/g tissue and eliminated the parasites. In addition, the liver and spleen of infected mice showed less histopathological alteration and immunohistochemical expression of nuclear factor kappa β (NF-Kβ). We can conclude that MOL extract combined with PZ has a curative effect on S. mansoni infection and helped to lessen its pathological effects.

Neglected tropical diseases and systemic racism especially in Brazil: from socio-economic aspects to the development of new drugs

Neglected tropical diseases (NTDs) are highly prevalent communicable diseases in tropical and subtropical countries, generally not economically attractive for drug development and related to poverty. In Brazil, more specifically, socioeconomic inequalities and health indicators are strongly influenced by skin color, race, and ethnicity, due to the historical process of slavery. In this context, it is important to understand the concept of systemic racism: a form of indirect racial discrimination present in many institutions, which determines the process of illness and death of the black population, the ethnic group most affected by these diseases. The main objective of this paper was to carry out a literature review on the socioeconomic aspects of these diseases, relating them to institutional racism, and to encourage reflection on the influence of this type of racism in the NTDs context. Therefore, we present a paper that brings a evident correlation between racism versus neglected populations, which are affected by equally neglected diseases. A more humane and comprehensive view is needed to realize that these illnesses affect neglected and vulnerable populations, who require decent living conditions, health, and social justice. We hope to provide, with this paper, enough, but not exhaust, knowledge to initiate the discussion about neglected diseases, their socioeconomic aspects and institutional racism.

Schistosomiasis: Discovery of New Molecules for Disease Treatment and Vaccine Development

The parasite blood flukes belonging to the genus Schistosoma cause schistosomiasis. Among the Schistosoma species that infect humans, three stand out: Schistosoma japonicum (S. japonicum), which occurs in Asia, mainly in China and the Philippines; Schistosoma haematobium (S. haematobium), which occurs in Africa; and Schistosoma mansoni (S. mansoni), which occurs in Africa and South America and the center of Venezuela (Brazil). Research has shown that these species comprise strains that are resistant to Praziquantel (PZQ), the only drug of choice to fight the disease. Moreover, patients can be reinfected even after being treated with PZQ , and this drug does not act against young forms of the parasite. Therefore, several research groups have focused their studies on new molecules for disease treatment and vaccine development. This chapter will focus on (i) parasite resistance to PZQ , (ii) molecules that are currently being developed and tested as possible drugs against schistosomiasis, and (iii) candidates for vaccine development with a primary focus on clinical trials.

Schistosomicidal and hepatoprotective activity of gamma-aminobutyric acid (GABA) alone or combined with praziquantel against Schistosoma mansoni infection in murine model

OBJECTIVE

This study aimed to evaluate the efficacy of gamma-aminobutyric acid (GABA) alone or combined with praziquantel (PZQ) against Schistosoma (S) mansoni infection in a murine model.

METHODS

Five groups, 8 mice each, were studied; GI served as normal controls; GII: S. mansoni-infected control group and the other three S. mansoni-infected groups received drug regimens for 5 consecutive days as follows GIII: Infected-PZQ treated group (200 mg/kg/day); GIV: Infected-GABA treated group (300 mg/kg/day) and GV: Infected-PZQ-GABA treated group (100 mg/kg/day for each drug). All animal groups were sacrificed two weeks later and different parasitological, histopathological and biochemical parameters were assessed.

RESULTS

Combined GABA-PZQ treated group recorded the highest significant reduction in all parasitological, histopathological and biochemical parameters followed by PZQ and finally GABA groups. Combined GABA-PZQ treatment led to the complete disappearance of immature eggs and marked reduction of deposited eggs in liver tissues and improved liver pathology. Significant improvement in hepatic oxidative stress levels, serum albumin and total protein in response to GABA treatment alone or combined with PZQ.

CONCLUSION

GABA had schistosomicidal, hepatoprotective and antioxidant activities against S. mansoni infection, GABA disrupted parasite pairing and activity, reduced the total number of worms recovered and the number of ova in the tissues. GABA may be considered an adjuvant therapy to potentiate PZQ antiparasitic activity and eradicate infection-induced liver damage and oxidative stress.

Drug Repurposing and De Novo Drug Discovery of Protein Kinase Inhibitors as New Drugs against Schistosomiasis

Schistosomiasis is a neglected tropical disease affecting more than 200 million people worldwide. Chemotherapy relies on one single drug, praziquantel, which is safe but ineffective at killing larval stages of this parasite. Furthermore, concerns have been expressed about the rise in resistance against this drug. In the absence of an antischistosomal vaccine, it is, therefore, necessary to develop new drugs against the different species of schistosomes. Protein kinases are important molecules involved in key cellular processes such as signaling, growth, and differentiation. The kinome of schistosomes has been studied and the suitability of schistosomal protein kinases as targets demonstrated by RNA interference studies. Although protein kinase inhibitors are mostly used in cancer therapy, e.g., for the treatment of chronic myeloid leukemia or melanoma, they are now being increasingly explored for the treatment of non-oncological conditions, including schistosomiasis. Here, we discuss the various approaches including screening of natural and synthetic compounds, de novo drug development, and drug repurposing in the context of the search for protein kinase inhibitors against schistosomiasis. We discuss the status quo of the development of kinase inhibitors against schistosomal serine/threonine kinases such as polo-like kinases (PLKs) and mitogen-activated protein kinases (MAP kinases), as well as protein tyrosine kinases (PTKs).

Schistosoma mansoni α-N-acetylgalactosaminidase (SmNAGAL) regulates coordinated parasite movement and egg production

α-galactosidase (α-GAL) and α-N-acetylgalactosaminidase (α-NAGAL) are two glycosyl hydrolases responsible for maintaining cellular homeostasis by regulating glycan substrates on proteins and lipids. Mutations in the human genes encoding either enzyme lead to neurological and neuromuscular impairments seen in both Fabry- and Schindler/Kanzaki- diseases. Here, we investigate whether the parasitic blood fluke Schistosoma mansoni, responsible for the neglected tropical disease schistosomiasis, also contains functionally important α-GAL and α-NAGAL proteins. As infection, parasite maturation and host interactions are all governed by carefully-regulated glycosylation processes, inhibiting S. mansoni's α-GAL and α-NAGAL activities could lead to the development of novel chemotherapeutics. Sequence and phylogenetic analyses of putative α-GAL/α-NAGAL protein types showed Smp_089290 to be the only S. mansoni protein to contain the functional amino acid residues necessary for α-GAL/α-NAGAL substrate cleavage. Both α-GAL and α-NAGAL enzymatic activities were higher in females compared to males (p<0.05; α-NAGAL > α-GAL), which was consistent with smp_089290's female biased expression. Spatial localisation of smp_089290 revealed accumulation in parenchymal cells, neuronal cells, and the vitellaria and mature vitellocytes of the adult schistosome. siRNA-mediated knockdown (>90%) of smp_089290 in adult worms significantly inhibited α-NAGAL activity when compared to control worms (siLuc treated males, p<0.01; siLuc treated females, p<0.05). No significant reductions in α-GAL activities were observed in the same extracts. Despite this, decreases in α-NAGAL activities correlated with a significant inhibition in adult worm motility as well as in egg production. Programmed CRISPR/Cas9 editing of smp_089290 in adult worms confirmed the egg reduction phenotype. Based on these results, Smp_089290 was determined to act predominantly as an α-NAGAL (hereafter termed SmNAGAL) in schistosome parasites where it participates in coordinating movement and oviposition processes. Further characterisation of SmNAGAL and other functionally important glycosyl hydrolases may lead to the development of a novel anthelmintic class of compounds.

Drug associations as alternative and complementary therapy for neglected tropical diseases

The present paper aims to establish different treatments for neglected tropical disease by a survey on drug conjugations and possible fixed-dose combinations (FDC) used to obtain alternative, safer and more effective treatments. The source databases used were Science Direct and PubMed/Medline, in the intervals between 2015 and 2021 with the drugs key-words or diseases, like "schistosomiasis", "praziquantel", "malaria", "artesunate", "Chagas' disease", "benznidazole", "filariasis", diethylcarbamazine", "ivermectin", " albendazole". 118 works were the object of intense analysis, other articles and documents were used to increase the quality of the studies, such as consensuses for harmonizing therapeutics and historical articles. As a result, an effective NTD control can be achieved when different public health approaches are combined with interventions guided by the epidemiology of each location and the availability of appropriate measures to detect, prevent and control disease. It was also possible to verify that the FDCs promote a simplification of the therapeutic regimen, which promotes better patient compliance and enables a reduction in the development of parasitic resistance, requiring further studies aimed at resistant strains, since the combined APIs usually act by different mechanisms or at different target sites. In addition to eliminating the process of developing a new drug based on the identification and validation of active compounds, which is a complex, long process and requires a strong long-term investment, other advantages that FDCs have are related to productive gain and gain from the industrial plant, which can favor and encourage the R&D of new FDCs not only for NTDs but also for other diseases that require the use of more than one drug.

Prediction of antischistosomal small molecules using machine learning in the era of big data

Schistosomiasis is a neglected tropical disease caused by helminths of the Schistosoma genus. Despite its high morbidity and socio-economic burden, therapeutics are just a handful with praziquantel being the main drug. Praziquantel is an old drug registered for human use in 1982 and has since been administered en masse for chemotherapy, risking the development of resistance, thus the need for new drugs with different mechanisms of action. This review examines the use of machine learning (ML) in this era of big data to aid in the prediction of novel antischistosomal molecules. It first discusses the challenges of drug discovery in schistosomiasis. Explanations are then offered for big data, its characteristics and then, some open databases where large biochemical data on schistosomiasis can be obtained for ML model development are examined. The concepts of artificial intelligence, ML, and deep learning and their drug applications are explored in schistosomiasis. The use of binary classification in predicting antischistosomal compounds and some algorithms that have been applied including random forest and naive Bayesian are discussed. For this review, some deep learning algorithms (deep neural networks) are proposed as novel algorithms for predicting antischistosomal molecules via binary classification. Databases specifically designed for housing bioactivity data on antischistosomal molecules enriched with functional genomic datasets and ontologies are thus urgently needed for developing predictive ML models. This shows the application of machine learning techniques for the discovery of novel antischistosomal small molecules via binary classification in the era of big data.

Control Strategies for Carcinogenic-Associated Helminthiases: An Integrated Overview

Helminthiases are extremely prevalent in the developing world. In addition, the chronic infection with some parasitic worms are classified as carcinogenic. Therefore, it is utmost importance to understand the parasite-host interactions, the mechanisms underlay carcinogenesis and how they could be counteracted. This knowledge may ultimately guide novel control strategies that include chemotherapy-based approaches targeting these pathogens and associated pathologies caused by their infections. Little is known on how some helminthiases are associated with cancer; however, it has been hypothesized that chemical carcinogenesis may be involved in the process. Here, we summarize the current knowledge on chemical carcinogenesis associated with helminthiases, along with available therapeutic options and potential therapeutic alternatives including chemotherapy and/or immunotherapy. Ideally, the treatment of the carcinogenic helminthiases should target both the parasite and associated pathologies. The success of any chemotherapeutic regimen often depends on the host immune response during the infection and nutritional status among other factors. The close association between chemotherapy and cell-mediated immunity suggests that a dual therapeutic approach would be advantageous. In addition, there is a pressing need for complementary drugs that antagonize the carcinogenesis process associated with the helminth infections.

A Novel Treatment of Schistosomiasis: Nano-Calcium Silicate Incorporating 5% Copper Oxide

Purpose: Praziquantel (PZQ) is a well-known drug accredited by the World Health Organization (WHO) for the treatment of schistosomiasis. It shows poor efficiency in patients during the earliest infection phases. Therefore, the search for new alternative drugs was the intention of many researchers. Methods: In the current study, the effect of different concentrations (ranging from 0.07-10 μg∕mL) of calcium silicate (CS) containing 5% copper oxide [CS-5%CuO] on golden hamster infected by Schistosoma mansoni and Schistosoma haematobium (Egyptian strains) was evaluated in both in vitro and in vivo. To the best of our knowledge, this is a novel study in investigating the efficiency of CS-5%CuO against both strains of schistosomes. The worms of S. mansoni and S. haematobium were tested in RPMI-1640 medium in vitro. Results: The results declare that CS-5% CuO exhibited excellent anti-schistosomal activities on both in vitro and in vivo experiments for both Egyptians Schistosoma strains. The most potential effect of the CS-5% CuO was exhibited after 6 h by 10 μg∕mL with significant activity of (P value = 0.001). Conclusion: Therefore, CS-5%CuO may become an innovative treatment for the schistosomiasis.

Radicicol, a Novel Lead Compound against the Migratory-Stage Schistosomula of Schistosoma japonicum

Schistosomiasis poses a serious threat to human health and remains a major tropical and parasitic disease in more than 70 countries. Praziquantel (PZQ) has been the primary treatment for schistosomiasis for nearly 4 decades. However, its efficacy against migratory-stage schistosomula is limited. Radicicol (RAD), a β-resorcylic acid lactone derived from Paecilomyces sp. strain SC0924, was investigated as an alternative treatment for Schistosoma japonicum In vitro tests showed that within 72 h, RAD (10 μmol/liter) completely killed schistosomula of both skin and liver stages with an efficacy significantly higher than that of PZQ, although it was less potent against adult worms than PZQ. In vivo, RAD reduced worm burdens and liver eggs by 91.18% and 86.01%, respectively, by killing migratory-stage schistosomula. Optical microscopy and scanning electron microscopy revealed that RAD damaged the epiderm and tegument morphology of S. japonicum worms at various stages and altered their motility to different degrees. RAD exhibited schistosomicidal effects at different stages in vitro and in vivo, especially at the migratory stage, implying that its mechanism could be different from that of PZQ. Collectively, these results showed that RAD is promising as a lead for the development of drugs to control the migratory-stage schistosomula of S. japonicum.

Long non-coding RNA levels can be modulated by 5-azacytidine in Schistosoma mansoni

Schistosoma mansoni is a flatworm that causes schistosomiasis, a neglected tropical disease that affects more than 200 million people worldwide. There is only one drug indicated for treatment, praziquantel, which may lead to parasite resistance emergence. The ribonucleoside analogue 5-azacytidine (5-AzaC) is an epigenetic drug that inhibits S. mansoni oviposition and ovarian development through interference with parasite transcription, translation and stem cell activities. Therefore, studying the downstream pathways affected by 5-AzaC in S. mansoni may contribute to the discovery of new drug targets. Long non-coding RNAs (lncRNAs) are transcripts longer than 200 nucleotides with low or no protein coding potential that have been involved in reproduction, stem cell maintenance and drug resistance. We have recently published a catalog of lncRNAs expressed in S. mansoni life-cycle stages, tissues and single cells. However, it remains largely unknown if lncRNAs are responsive to epigenetic drugs in parasites. Here, we show by RNA-Seq re-analyses that hundreds of lncRNAs are differentially expressed after in vitro 5-AzaC treatment of S. mansoni females, including intergenic, antisense and sense lncRNAs. Many of these lncRNAs belong to co-expression network modules related to male metabolism and are also differentially expressed in unpaired compared with paired females and ovaries. Half of these lncRNAs possess histone marks at their genomic loci, indicating regulation by histone modification. Among a selected set of 8 lncRNAs, half of them were validated by RT-qPCR as differentially expressed in females, and some of them also in males. Interestingly, these lncRNAs are also expressed in other life-cycle stages. This study demonstrates that many lncRNAs potentially involved with S. mansoni reproductive biology are modulated by 5-AzaC and sheds light on the relevance of exploring lncRNAs in response to drug treatments in parasites.

Drug Repurposing Approaches to Combating Viral Infections

Development of novel antiviral molecules from the beginning costs an average of $350 million to $2 billion per drug, and the journey from the laboratory to the clinic takes about 10–15 years. Utilization of drug repurposing approaches has generated substantial interest in order to overcome these drawbacks. A drastic reduction in the failure rate, which otherwise is ~92%, is achieved with the drug repurposing approach. The recent exploration of the drug repurposing approach to combat the COVID-19 pandemic has further validated the fact that it is more beneficial to reinvestigate the in-practice drugs for a new application instead of designing novel drugs. The first successful example of drug repurposing is zidovudine (AZT), which was developed as an anti-cancer agent in the 1960s and was later approved by the US FDA as an anti-HIV therapeutic drug in the late 1980s after fast track clinical trials. Since that time, the drug repurposing approach has been successfully utilized to develop effective therapeutic strategies against a plethora of diseases. Hence, an extensive application of the drug repurposing approach will not only help to fight the current pandemics more efficiently but also predict and prepare for newly emerging viral infections. In this review, we discuss in detail the drug repurposing approach and its advancements related to viral infections such as Human Immunodeficiency Virus (HIV) and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2).

Single oral fixed-dose praziquantel-miltefosine nanocombination for effective control of experimental schistosomiasis mansoni

Background

The control of schistosomiasis has been centered to date on a single drug, praziquantel, with shortcomings including treatment failure, reinfection, and emergence of drug resistance. Drug repurposing, combination therapy or nanotechnology were explored to improve antischistosomal treatment. The aim of the present study was to utilize a novel combination of the three strategies to improve the therapeutic profile of praziquantel. This was based on a fixed-dose nanocombination of praziquantel and miltefosine, an antischistosomal repurposing candidate, co-loaded at reduced doses into lipid nanocapsules, for single dose oral therapy.

Methods

Two nanocombinations were prepared to provide 250 mg praziquantel-20 mg miltefosine/kg (higher fixed-dose) or 125 mg praziquantel-10 mg miltefosine/kg (lower fixed-dose), respectively. Their antischistosomal efficacy in comparison with a non-treated control and their praziquantel or miltefosine singly loaded counterparts was assessed in murine schistosomiasis mansoni. A single oral dose of either formulation was administered on the initial day of infection, and on days 21 and 42 post-infection. Scanning electron microscopic, parasitological, and histopathological studies were used for assessment. Preclinical data were subjected to analysis of variance and Tukeyʼs post-hoc test for pairwise comparisons.

Results

Lipid nanocapsules (~ 58 nm) showed high entrapment efficiency of both drugs (> 97%). Compared to singly loaded praziquantel-lipid nanocapsules, the higher nanocombination dose showed a significant increase in antischistosomal efficacy in terms of statistically significant decrease in mean worm burden, particularly against invasive and juvenile worms, and amelioration of hepatic granulomas (P ≤ 0.05). In addition, scanning electron microscopy examination showed extensive dorsal tegumental damage with noticeable deposition of nanostructures.

Conclusions

The therapeutic profile of praziquantel could be improved by a novel multiple approach integrating drug repurposing, combination therapy and nanotechnology. Multistage activity and amelioration of liver pathology could be achieved by a new praziquantel-miltefosine fixed-dose nanocombination providing 250 mg praziquantel-20 mg miltefosine/kg. To the best of our knowledge, this is the first report of a fixed-dose nano-based combinatorial therapy for schistosomiasis mansoni. Further studies are needed to document the nanocombination safety and explore its prophylactic activity and potential to hinder the onset of resistance to the drug components.

Activity of Combinations of Antioxidants and Anthelmintic Drugs against the Adult Stage of Schistosoma mansoni

Schistosomiasis remains a major neglected tropical disease. The treatment and control of schistosomiasis rely on a single drug, praziquantel (PZQ). Despite its efficacy, treatment with PZQ presents some major drawbacks including an inability of the chemotherapy to reverse disease-induced fibrosis and the prospect of the emergence of drug resistance. Here, we investigated a novel therapeutic approach with antioxidant biomolecules in combination with PZQ against the adult developmental stage of Schistosoma mansoni and oviposition in vitro, given that this therapeutic approach achieved synergistic/additive activity against larval schistosomes. The antioxidants curcumin and oxadiazole per se exhibited antischistosomal activity against adult worms leading to severe morphological alterations and death. Additionally, the antioxidant flavone combined with vandetanib or imatinib improved antischistosomal activity against adult forms. By contrast, however, these antioxidant-anthelmintic combinations were not as effective against adults in comparison to larval schistosomes. Nevertheless, the antioxidants alone or combined with drugs inhibited oviposition.

Molecular Context of ADP-ribosylation in Schistosomes for Drug Discovery and Vaccine Development

Schistosome infection is regarded as one of the most important and neglected tropical diseases associated with poor sanitation. Like other living organisms, schistosomes employ multiple biological processes, of which some are regulated by a post-translational modification called Adenosine Diphosphate-ribosylation (ADP-ribosylation), catalyzed by ADP-ribosyltransferases. ADP-ribosylation is the addition of ADP-ribose moieties from Nicotinamide Adenine Dinucleotide (NAD+) to various targets, which include proteins and nucleotides. It is crucial in biological processes such as DNA repair, apoptosis, carbohydrate metabolism and catabolism. In the absence of a vaccine against schistosomiasis, this becomes a promising pathway in the identification of drug targets against various forms of this infection. The tegument of the worm is an encouraging immunogenic target for anti-schistosomal vaccine development. Vaccinology, molecular modeling and target-based drug discovery strategies have been used for years in drug discovery and for vaccine development. In this paper, we outline ADP-ribosylation and other different approaches to drug discovery and vaccine development against schistosomiasis.

Current and Novel Therapies Against Helminthic Infections: The Potential of Antioxidants Combined with Drugs

Infections caused by Schistosoma haematobium and Opisthorchisviverrini are classified as Group 1 biological carcinogen and it has been postulated that parasites produce oxysterol and estrogen-like metabolites that might be considered as initiators of infection-associated carcinogenesis. Chemotherapy for these helminthic infections relies on a single drug, praziquantel, (PZQ) that mainly targets the parasite. Additionally, PZQ has some major drawbacks as inefficacy against juvenile form and alone it is not capable to counteract pathologies associated to infections or prevent carcinogenesis. There is an urgent need to develop novel therapeutic approaches that not only target the parasite but also improve the pathologies associated to infection, and ultimately, counteract or/and prevent the carcinogenesis processes. Repurposing the drug in combination of compounds with different modes of action is a promising strategy to find novel therapeutics approaches against these helminthic infections and its pathologies. Here, we emphasized that using antioxidants either alone or combined with anthelmintic drugs could ameliorate tissue damage, infection-associated complications, moreover, could prevent the development of cancer associated to infections. Hence, antioxidants represent a potential adjuvant approach during treatment to reduce morbidity and mortality. Despite the success of some strategies, there is a long way to go to implement novel therapies for schistosomiasis.

Searching for drugs for Chagas disease, leishmaniasis and schistosomiasis: a review

Chagas disease, leishmaniasis and schistosomiasis are neglected diseases (NDs) and are a considerable global challenge. Despite the huge number of people infected, NDs do not create interest from pharmaceutical companies because the associated revenue is generally low. Most of the research on these diseases has been conducted in academic institutions. The chemotherapeutic armamentarium for NDs is scarce and inefficient and better drugs are needed. Researchers have found some promising potential drug candidates using medicinal chemistry and computational approaches. Most of these compounds are synthetic but some are from natural sources or are semi-synthetic. Drug repurposing or repositioning has also been greatly stimulated for NDs. This review considers some potential drug candidates and provides details of their design, discovery and activity.

Repositioning of HIV Aspartyl Peptidase Inhibitors for Combating the Neglected Human Pathogen Trypanosoma cruzi

Chagas disease, caused by the flagellate parasite Trypanosoma cruzi, is a wellknown neglected tropical disease. This parasitic illness affects 6-7 million people and can lead to severe myocarditis and/or complications of the digestive tract. The changes in its epidemiology facilitate co-infection with the Human Immunodeficiency Virus (HIV), making even more difficult the diagnosis and prognosis. The parasitic infection is reactivated in T. cruzi/HIV co-infection, with the appearance of unusual manifestations in the chronic phase and the exacerbation of classical clinical signs. The therapeutic arsenal to treat Chagas disease, in all its clinical forms, is restricted basically to two drugs, benznidazole and nifurtimox. Both drugs are extremely toxic and the therapeutic efficacy is still unclear, making the clinical treatment a huge issue to be solved. Therefore, it seems obvious the necessity of new tangible approaches to combat this illness. In this sense, the repositioning of approved drugs appears as an interesting and viable strategy. The discovery of Human Immunodeficiency Virus Aspartyl Peptidase Inhibitors (HIV-PIs) represented a milestone in the treatment of Acquired Immune Deficiency Syndrome (AIDS) and, concomitantly, a marked reduction in both the incidence and prevalence of important bacterial, fungal and parasitic co-infections was clearly observed. Taking all these findings into consideration, the present review summarizes the promising and beneficial data concerning the effects of HIV-PIs on all the evolutionary forms of T. cruzi and in important steps of the parasite's life cycle, which highlight their possible application as alternative drugs to treat Chagas disease.

Anthelmintics in the future: current trends in the discovery and development of new drugs against gastrointestinal nematodes

The control of gastrointestinal nematodes (GINs), the most abundant and serious parasites of livestock, has become difficult because of the limited number of available drugs and fast development of drug resistance. Thus, considerable efforts have been devoted to developing new anthelmintics that are efficient against nematodes, especially resistant species. Here, we summarize the most recent results using various approaches: target-based or high-throughput screening (HTS) of compound libraries; the synthesis of new derivatives or new combinations of current anthelmintics; the repurposing of drugs currently approved for other indications; and lastly, the identification of active plant products. We also evaluate the advantages and disadvantages of each of these approaches.

Enhancement of the therapeutic efficacy of praziquantel in murine Schistosomiasis mansoni using silica nanocarrier

The main objective of this work is preparation of mesoporous silica nanoparticles loaded with praziquantel (PZQ-Si) in order to enhance the therapeutic efficacy of praziquantel (PZQ). Mice were experimentally infected with Schistosoma mansoni and treated 6 weeks post-infection with PZQ in different doses via either oral or intraperitoneal (IP) routes. PZQ in the same doses orally administered to S. mansoni-infected mice was used as a drug control, and infected and non-infected non-treated mice served as positive and negative controls, respectively. PZQ-Si exhibited good physicochemical attributes in terms of small uniform size (105 nm), spherical shape, and PZQ entrapment efficiency (83%). A maximum antischistosomal effect was achieved using orally administered PZQ-Si as reflected by total worm burden, tissue egg count, oogram pattern, and hepatic granuloma count and diameter. The biomarkers related to liver oxidative stress status and immunomodulatory effect (serum TNF-α and IL-10) were significantly improved. Data obtained implied that IP route was less efficacious for the delivery of PZQ-Si. Encapsulation of PZQ permits the reduction of the used therapeutic dose of PZQ. Hepatic DNA fragmentation, measured by comet assay, was significantly improved in infected mice treated with maximum dose of PZQ-Si as compared to positive or PZQ control groups. The results indicate that mesoporous silica NP is a promising safe nanocarrier for PZQ potentiating its antischistosomal, antioxidant, immunomodulatory, and anti-inflammatory action in animal model infected with S. mansoni. From a practical standpoint, PZQ-Si using a lower dose of PZQ could be suggested for effective PZQ antischistosomal mass chemotherapy.

Assessment of the potential therapeutic effects of omeprazole in Schistosoma mansoni infected mice

Schistosomiasis is a neglected chronic parasitic disease with a significant lasting morbidity. Currently, praziquantel (PZQ) is the most efficient drug for schistosomiasis worldwide. However, the possibility of the occurrence of resistance to PZQ is increasing. Therefore, there is a vital need to find new antischistosomal drugs or to increase the efficacy of the existing ones. Omeprazole is a proton pump inhibitor which is reported to have antiparasitic properties. Thus, the aim of this study was to assess the potential therapeutic effects of omeprazole in experimental Schistosoma mansoni infection either alone or in combination with PZQ. For this aim, 80 laboratory bred mice were divided into 3 groups; uninfected control, infected untreated control, and infected and treated at tenth week P.I. The last group was divided into three subgroups that received either PZQ alone, omeprazole alone, or both drugs. The effectiveness of treatment was assessed by adult worm counts, liver egg count, scanning electron microscopy of adult worms, histopathological, and immunohistochemical (GFAP) examination. There was significant reduction of adult worm counts, liver egg counts, size, diameter of hepatic granulomas, hepatic fibrosis, and GFAP expression in the group that received combined treatment as compared to PZQ group. Moreover, the tegumental changes were more evident in the group that received combined treatment. In conclusion, the administration of omeprazole with PZQ improved the efficacy of PZQ in the treatment of Schistosomiasis mansoni.

Cannabinoid receptor-1 antagonism: a new perspective on treating a murine schistosomal liver fibrosis model

BACKGROUND

Formation of schistosomal granulomata surrounding the ova can result in schistosomiasis-associated liver fibrosis (SSLF). The current standard of treatment is praziquantel (PZQ), which cannot effectively reverse SSLF. The role of the cannabinoid (CB) receptor family in liver fibrosis has recently been highlighted.

OBJECTIVES

This study aimed to assess the therapeutic effect of CB1 receptor antagonism in reversing SSLF in a murine model of Schistosoma mansoni infection.

METHODS

One hundred male Swiss albino mice were divided equally into five groups: healthy uninfected control (group I), infected control (group II), PZQ treated (group III), rimonabant (RIM) (SR141716, a CB1 receptor antagonist)-treated (group IV) and group V was treated with combined PZQ and RIM. Liver sections were obtained for histopathological examination, alpha-1 smooth muscle actin (α-SMA) immunostaining and assessment of CB1 receptor expression using real-time polymerase chain reaction (RT-PCR).

FINDINGS

The most effective reduction in fibrotic marker levels and granuloma load was achieved by combined treatment with PZQ+RIM (group V): CB1 receptor expression (H = 26.612, p < 0.001), number of α-SMA-positive cells (F = 57.086, p < 0.001), % hepatic portal fibrosis (F = 42.849, p < 0.001) and number of granulomata (F = 69.088, p < 0.001).

MAIN CONCLUSIONS

Combining PZQ with CB1 receptor antagonists yielded the best results in reversing SSLF. To our knowledge, this is the first study to test this regimen in S. mansoni infection.

Biological activity of artemisinin-naphthoquine phosphate on Schistosoma haematobium stages and the vector Bulinus truncatus

BACKGROUND

Schistosoma haematobium infection is a major public health problem in most of Africa and the Middle East and praziquantel remains the only drug used for schistosomiasis control, therefore emergence of drug resistance is unavoidable. The antimalarial artemisinin-naphthoquine phosphate combination (co-ArNp) was recently documented to have promising effects on Schistosoma mansoni and its snail host.

METHODS

We conducted this in vitro study to assess the bioactivity of co-ArNp on S. haematobium and its snail vector Bulinus truncatus.

RESULTS

Treatment of S. haematobium worms with 1 μg/ml co-ArNp for 24 h reduced worm motility, while 20 μg/ml resulted in 25-100% mortality of adult flukes within 48-72 h. Incubation of S. haematobium miracidia and cercariae with the molluscicidal co-ArNp (50% lethal concentration 7.5 μg/ml) killed all the free larval stages within 40 and 15 min, respectively. Also, exposure of B. truncatus adult snails to 20 ppm of the combined regimen caused a mortality rate of 100% within 24 h.

CONCLUSIONS

Co-ArNp therapy has also shown encouraging activity against the other major human schistosome, S. haematobium, as well as its vector.

Combination Anthelmintic/Antioxidant Activity Against Schistosoma Mansoni

Schistosomiasis is a major neglected tropical disease. Treatment for schistosomiasis with praziquantel (PZQ), which is effective against the parasite, by itself is not capable to counteract infection-associated disease lesions including hepatic fibrosis. There is a pressing need for novel therapies. Due to their biological properties, antioxidant biomolecules might be useful in treating and reverting associated pathological sequelae. Here, we investigated a novel therapy approach based on a combination of anthelmintic drugs with antioxidant biomolecules. We used a host-parasite model involving Bioamphalaria glabrata and newly transformed schistosomula (NTS) of Schistosoma mansoni. For in vitro drug screening assays, was selected several antioxidants and evaluated not only antischistosomal activity but also ability to enhance activity of the anthelmintic drugs praziquantel (PZQ) and artesunate (AS). The morphological alterations induced by compounds alone/combined were assessed on daily basis using an inverted and automated microscope to quantify NTS viability by a fluorometric-based method. The findings indicated that not only do some antioxidants improve antischistosomal activity of the two anthelmintics, but they exhibit activity per se, leading to high mortality of NTS post-exposure. The combination index (CI) of PZQ + Mel (CI = 0.80), PZQ + Resv (CI = 0.74), AS + Resv (CI = 0.34), AS + NAC (CI = 0.89), VDT + Flav (CI = 1.03) and VDT + Resv (CI = 1.06) reveal that they display moderate to strong synergism. The combination of compounds with discrete mechanisms of action might provide a valuable adjunct to contribution for treatment of schistosomiasis-associated disease.

PZQ Therapy: How Close are we in the Development of Effective Alternative Anti-schistosomal Drugs?

Today schistosomiasis, caused mainly by the three major schistosome species (S. mansoni, S. haematobium and S. japonicum), has for many decades and still continues to be on a rapid and swift rise globally, claiming thousands of lives every year and leaving 800 million people at the risk of infection. Due to the high prevalence of this disease and the steady increase in the infection rates, praziquantel (PZQ) remains the only effective drug against this acute disease although it has no effect on the juvenile schistosome parasite. However, no significant approaches have been made in recent years in the discovery of new or alternative drugs and unfortunately, resistance to this drug has been reported in some parts of the world. Therefore, it is imperative to develop a new drug for this debilitating disease. In this review, a brief history of past, present, and new promising anti-schistosomal drugs is presented.

An Abies procera-derived tetracyclic triterpene containing a steroid-like nucleus core and a lactone side chain attenuates in vitro survival of both Fasciola hepatica and Schistosoma mansoni

Two economically and biomedically important platyhelminth species, Fasciola hepatica (liver fluke) and Schistosoma mansoni (blood fluke), are responsible for the neglected tropical diseases (NTDs) fasciolosis and schistosomiasis. Due to the absence of prophylactic vaccines, these NTDs are principally managed by the single class chemotherapies triclabendazole (F. hepatica) and praziquantel (S. mansoni). Unfortunately, liver fluke resistance to triclabendazole has been widely reported and blood fluke insensitivity/resistance to praziquantel has been observed in both laboratory settings as well as in endemic communities. Therefore, the identification of new anthelmintics is necessary for the sustainable control of these NTDs in both animal and human populations. Here, continuing our work with phytochemicals, we isolated ten triterpenoids from the mature bark of Abies species and assessed their anthelmintic activities against F. hepatica and S. mansoni larval and adult lifecycle stages. Full ¹H and ¹³C NMR-mediated structural elucidation of the two most active triterpenoids revealed that a tetracyclic steroid-like nucleus core and a lactone side chain are associated with the observed anthelmintic effects. When compared to representative mammalian cell lines (MDBK and HepG2), the most potent triterpenoid (700015; anthelmintic EC₅₀s range from 0.7 μM–15.6 μM) displayed anthelmintic selectivity (selectivity indices for F. hepatica: 13 for newly excysted juveniles, 46 for immature flukes, 2 for mature flukes; selectivity indices for S. mansoni: 14 for schistosomula, 9 for immature flukes, 4 for adult males and 3 for adult females) and induced severe disruption of surface membranes in both liver and blood flukes. S. mansoni egg production, a process responsible for pathology in schistosomiasis, was also severely inhibited by 700015. Together, our results describe the structural elucidation of a novel broad acting anthelmintic triterpenoid and support further investigations developing this compound into more potent analogues for the control of both fasciolosis and schistosomiasis.

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Abies species contain anthelmintic phytochemical triterpenoids.

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The triterpenoid 700015 affects larval, juvenile and adult fluke viabilities.

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700015 is moderately selective against both fluke species.

Schistosomiasis

Schistosomiasis (bilharzia) is a neglected tropical disease caused by parasitic flatworms (blood flukes) of the genus Schistosoma, with considerable morbidity in parts of the Middle East, South America, Southeast Asia and, particularly, in sub-Saharan Africa. Infective larvae grow in an intermediate host (fresh-water snails) before penetrating the skin of the definitive human host. Mature adult worms reside in the mesenteric (Schistosoma mansoni and Schistosoma japonicum) or pelvic (Schistosoma haematobium) veins, where female worms lay eggs, which are secreted in stool or urine. Eggs trapped in the surrounding tissues and organs, such as the liver and bladder, cause inflammatory immune responses (including granulomas) that result in intestinal, hepato-splenic or urogenital disease. Diagnosis requires the detection of eggs in excreta or worm antigens in the serum, and sensitive, rapid, point-of-care tests for populations living in endemic areas are needed. The anti-schistosomal drug praziquantel is safe and efficacious against adult worms of all the six Schistosoma spp. infecting humans; however, it does not prevent reinfection and the emergence of drug resistance is a concern. Schistosomiasis elimination will require a multifaceted approach, including: treatment; snail control; information, education and communication; improved water, sanitation and hygiene; accurate diagnostics; and surveillance-response systems that are readily tailored to social-ecological settings.

Innovation in neglected tropical disease drug discovery and development

BACKGROUND

Neglected tropical diseases (NTDs) are closely related to poverty and affect over a billion people in developing countries. The unmet treatment needs cause high mortality and disability thereby imposing a huge burden with severe social and economic consequences. Although coordinated by the World Health Organization, various philanthropic organizations, national governments and the pharmaceutical industry have been making efforts in improving the situation, the control of NTDs is still inadequate and extremely difficult today. The lack of safe, effective and affordable medicines is a key contributing factor. This paper reviews the recent advances and some of the challenges that we are facing in the fight against NTDs.

MAIN BODY

In recent years, a number of innovations have demonstrated propensity to promote drug discovery and development for NTDs. Implementation of multilateral collaborations leads to continued efforts and plays a crucial role in drug discovery. Proactive approaches and advanced technologies are urgently needed in drug innovation for NTDs. However, the control and elimination of NTDs remain a formidable task as it requires persistent international cooperation to make sustainable progresses for a long period of time. Some currently employed strategies were proposed and verified to be successful, which involve both mechanisms of 'Push' which aims at cutting the cost of research and development for industry and 'Pull' which aims at increasing market attractiveness. Coupled to this effort should be the exercise of shared responsibility globally to reduce risks, overcome obstacles and maximize benefits. Since NTDs are closely associated with poverty, it is absolutely essential that the stakeholders take concerted and long-term measures to meet multifaceted challenges by alleviating extreme poverty, strengthening social intervention, adapting climate changes, providing effective monitoring and ensuring timely delivery.

CONCLUSIONS

The ongoing endeavor at the global scale will ultimately benefit the patients, the countries they are living and, hopefully, the manufacturers who provide new preventive, diagnostic and therapeutic products.