Structure-activity relationship and target investigation of 2-aryl quinolines with nematocidal activity

Within the context of our anthelmintic discovery program, we recently identified and evaluated a quinoline derivative, called ABX464 or obefazimod, as a nematocidal candidate; synthesised a series of analogues which were assessed for activity against the free-living nematode Caenorhabditis elegans; and predicted compound-target relationships by thermal proteome profiling (TPP) and in silico docking. Here, we logically extended this work and critically evaluated the anthelmintic activity of ABX464 analogues on Haemonchus contortus (barber's pole worm) - a highly pathogenic nematode of ruminant livestock. First, we tested a series of 44 analogues on H. contortus (larvae and adults) to investigate the nematocidal pharmacophore of ABX464, and identified one compound with greater potency than the parent compound and showed moderate activity against a select number of other parasitic nematodes (including Ancylostoma, Heligmosomoides and Strongyloides species). Using TPP and in silico modelling studies, we predicted protein HCON_00074590 (a predicted aldo-keto reductase) as a target candidate for ABX464 in H. contortus. Future work aims to optimise this compound as a nematocidal candidate and investigate its pharmacokinetic properties. Overall, this study presents a first step toward the development of a new nematocide.

Diagnostic tests for human Schistosoma mansoni and Schistosoma haematobium infection: a systematic review and meta-analysis

BACKGROUND

Accurate diagnosis is pivotal for implementing strategies for surveillance, control, and elimination of schistosomiasis. Despite their low sensitivity in low-endemicity areas, microscopy-based urine filtration and the Kato-Katz technique are considered as reference diagnostic tests for Schistosoma haematobium and Schistosoma mansoni infections, respectively. We aimed to collate all available evidence on the accuracy of other proposed diagnostic techniques.

METHODS

In this systematic review and meta-analysis, we searched PubMed, Embase, the Cochrane Library, and LILACS for studies published from database inception to Dec 31, 2022, investigating the sensitivity and specificity of diagnostic tests for S haematobium and S mansoni infections against Kato-Katz thick smears or urine microscopy (reference tests) involving adults (aged ≥18 years), school-aged children (aged 7 to 18 years), or preschool-aged children (aged 1 month to 7 years). We extracted raw data on true positives, true negatives, false positives, and false negatives for the diagnostic tests and data on the number of participants, study authors, publication year, journal, study design, participants' age and sex, prevalence of Schistosoma infection, and treatment status. To account for imperfect reference tests, we used a hierarchical Bayesian latent class meta-analysis to model test accuracy.

FINDINGS

Overall, we included 121 studies, assessing 28 different diagnostic techniques. Most studies (103 [85%] of 121) were done in Africa, 14 (12%) in South America, one (1%) in Asia, and one (1%) in an unknown country. Compared with the reference test, Kato-Katz thick smears, circulating cathodic antigen urine cassette assay version 1 (CCA1, 36 test comparisons) had excellent sensitivity (95% [95% credible interval 88-99]) and reasonable specificity (74% [63-83]) for S mansoni. ELISA-based tests had a performance comparable to circulating cathodic antigen, but there were few available test comparisons. For S haematobium, proteinuria (42 test comparisons, sensitivity 73% [62-82]; specificity 94% [89-98]) and haematuria (75 test comparisons, sensitivity 85% [80-90]; specificity 96% [92-99]) reagent strips showed high specificity, with haematuria reagent strips having better sensitivity. Despite limited data, nucleic acid amplification tests (NAATs; eg, PCR or loop-mediated isothermal amplification [LAMP]) showed promising results with sensitivity estimates above 90%. We found an unclear risk of bias of about 70% in the use of the reference or index tests and of 50% in patient selection. All analyses showed substantial heterogeneity (I2>80%).

INTERPRETATION

Although NAATs and immunological diagnostics show promise, the limited information available precludes drawing definitive conclusions. Additional research on diagnostic accuracy and cost-effectiveness is needed before the replacement of conventional tests can be considered.

FUNDING

WHO and Luxembourg Institute of Health.

Clonorchiasis and opisthorchiasis: epidemiology, transmission, clinical features, morbidity, diagnosis, treatment, and control

Clonorchis sinensis, Opisthorchis viverrini, and Opisthorchis felineus are important liver flukes that cause a considerable public health burden in eastern Asia, southeastern Asia, and eastern Europe, respectively. The life cycles are complex, involving humans, animal reservoirs, and two kinds of intermediate hosts. An interplay of biological, cultural, ecological, economic, and social factors drives transmission. Chronic infections are associated with liver and biliary complications, most importantly cholangiocarcinoma. With regard to diagnosis, stool microscopy is widely used in epidemiologic surveys and for individual diagnosis. Immunologic techniques are employed for screening purposes, and molecular techniques facilitate species differentiation in reference laboratories. The mainstay of control is preventive chemotherapy with praziquantel, usually combined with behavioral change through information, education and communication, and environmental control. Tribendimidine, a drug registered in the People's Republic of China for soil-transmitted helminth infections, shows potential against both C. sinensis and O. viverrini and, hence, warrants further clinical development. Novel control approaches include fish vaccine and biological control. Considerable advances have been made using multi-omics which may trigger the development of new interventions. Pressing research needs include mapping the current distribution, disentangling the transmission, accurately estimating the disease burden, and developing new diagnostic and treatment tools, which would aid to optimize control and elimination measures.

Egg excretion patterns of soil-transmitted helminth infections in humans following albendazole-ivermectin and albendazole treatment

BACKGROUND

Control efforts of soil-transmitted helminthiases rely primarily on large scale administration of anthelminthic drugs. The assessment of drug efficacies and understanding of drug behavior is pivotal to the evaluation of treatment successes, both in preventive chemo-therapy programs as well as in research of novel treatment options. The current WHO guidelines recommend an interval of 14-21 days between the treatment and follow-up, yet no in-depth analysis of egg excretion patterns of Trichuris trichiura after treatment has been conducted to date.

METHODS

Within the framework of a multi-country trial to assess the efficacy and safety of albendazole-ivermectin combination therapy vs albendazole monotherapy against T. trichiura infections, we conducted a study collecting daily stool samples over the period of 28 days post-treatment in 87 participants in Pak Khan, Lao PDR. Egg counts were derived by duplicate Kato-Katz on-site for T. trichiura, hookworm and Ascaris lumbricoides and stool sample aliquots were subsequently analyzed by qPCR for the detection of T. trichiura infections. Sensitivity and specificity was calculated for each day separately using data derived by Kato-Katz to determine the optimal timepoint at which to assess drug efficacy.

RESULTS

Egg excretion patterns varied across treatment arms. For T. trichiura, only the albendazole-ivermectin treatment led to a considerable reduction in mean egg counts, whereas both treatments reduced hookworm egg counts and A. lumbricoides were cleared in all participants after day 7. For T. trichiura, we found sensitivity to be highest at days 18 and 22 when using egg counts as outcome and days 19 and 24 when using qPCR. Specificity was high (>0.9) from day 14 onwards. For hookworm, the highest sensitivity and specificity were found at days 17 and 25, respectively.

CONCLUSIONS

Based on our study, the ideal time period to assess drug efficacy for soil-transmitted helminth infections would be between day 18 and 24. The current WHO recommendation of 14 to 21 days is likely to yield acceptable outcome measures for soil-transmitted helminth infections.

TRIAL REGISTRATION

NCT03527732.

Efficacy and safety of moxidectin compared with ivermectin against Strongyloides stercoralis infection in adults in Laos and Cambodia: a randomised, double-blind, non-inferiority, phase 2b/3 trial

BACKGROUND

Infection with the soil-transmitted helminth Strongyloides stercoralis affects up to 600 million people globally, most of whom live in rural areas with poor sanitation. If untreated, infection leads to long-lasting morbidity and might even be life-threatening. Moxidectin might be a promising alternative to ivermectin, the only currently recommended single-dose treatment. We aimed to assess whether moxidectin is non-inferior in terms of efficacy and safety compared with ivermectin.

METHODS

In this randomised, double-blind, parallel-group, non-inferiority, phase 2b/3 trial in communities in Laos and Cambodia, adults aged 18-65 years were screened for the presence of S stercoralis larvae in their stool via sextuplicate quantitative Baermann assays. Using computer-generated group allocation (block randomisation stratified by infection intensity), parasitologically (two or more positive Baermann assays) and clinically eligible participants were randomly assigned (1:1) to receive single oral doses of either moxidectin (8 mg) and ivermectin-matched placebo, or ivermectin (200 μg/kg bodyweight) and moxidectin-matched placebo. The primary endpoint was cure rate assessed at 14-21 days after treatment, using the available-case population analysed according to intention-to-treat principles. Moxidectin was considered non-inferior to ivermectin if the lower limit of the two-sided 95% CI of the difference was greater than the non-inferiority margin of -10 percentage points. Safety endpoints were assessed before treatment, and at 2-3 h, 24 h, and 14-21 days after treatment. This trial is registered at ClinicalTrials.gov, NCT04056325 and NCT04848688.

FINDINGS

Between Dec 6, 2020, and May 21, 2022, 4291 participants were screened, 726 of whom were enrolled and randomly assigned to moxidectin (n=363) or ivermectin (n=363). For the participants with primary outcome data, we observed a cure rate of 93·6% (95% CI 90·5 to 96·0; 324 of 346 participants) in the moxidectin group and 95·7% (93·0 to 97·6; 335 of 350 participants) in the ivermectin group, resulting in a between-group difference of -2·1 percentage points (95% CI -5·5 to 1·3). The most common adverse events were abdominal pain (32 [9%] of 363 with moxidectin vs 34 [9%] of 363 with ivermectin) and headache (25 [7%] vs 30 [8%]), which were predominantly mild and transient.

INTERPRETATION

Moxidectin was non-inferior to ivermectin in terms of efficacy in the treatment of strongyloidiasis. Additionally, both drugs had a similar safety profile. The fixed dose and lower cost of moxidectin compared with ivermectin make it a valuable alternative for people with strongyloidiasis.

FUNDING

Swiss National Science Foundation.

Strongyloidiasis

Strongyloidiasis is a neglected tropical disease caused primarily by the roundworm Strongyloides stercoralis. Strongyloidiasis is most prevalent in Southeast Asia and the Western Pacific. Although cases have been documented worldwide, global prevalence is largely unknown due to limited surveillance. Infection of the definitive human host occurs via direct skin penetration of the infective filariform larvae. Parasitic females reside in the small intestine and reproduce via parthenogenesis, where eggs hatch inside the host before rhabditiform larvae are excreted in faeces to begin the single generation free-living life cycle. Rhabditiform larvae can also develop directly into infectious filariform larvae in the gut and cause autoinfection. Although many are asymptomatic, infected individuals may report a range of non-specific gastrointestinal, respiratory or skin symptoms. Autoinfection may cause hyperinfection and disseminated strongyloidiasis in immunocompromised individuals, which is often fatal. Diagnosis requires direct examination of larvae in clinical specimens, positive serology or nucleic acid detection. However, there is a lack of standardization of techniques for all diagnostic types. Ivermectin is the treatment of choice. Control and elimination of strongyloidiasis will require a multifaceted, integrated approach, including highly sensitive and standardized diagnostics, active surveillance, health information, education and communication strategies, improved water, sanitation and hygiene, access to efficacious treatment, vaccine development and better integration and acknowledgement in current helminth control programmes.

SAFETY AND PHARMACOKINETICS OF PRAZIQUANTEL IN EUROPEAN POND TURTLES (EMYS ORBICULARIS)

Spirorchiidosis, caused by blood flukes of the genus Spirorchis, is a disease of great concern for the critically endangered European pond turtle (EPT; Emys orbicularis) in Switzerland. The endogenous life cycle of the parasite often leads to systemic inflammatory reactions, thrombosis, and death. Praziquantel (PZQ) is the treatment of choice against adult Spirorchis spp. in green (Chelonia mydas) and in loggerhead (Caretta caretta) sea turtles and is therefore considered for the treatment of EPT. This study aimed to establish a safe, easily applicable PZQ treatment for EPT, based on pharmacokinetics and tolerability. Three application methods were tested in a total of 12 adult EPT. Each turtle received a total of 75 mg/kg PZQ (three doses of 25 mg/kg in 3-h intervals [q3h × 3]) via IM (n = 3 turtles), SC (n = 3 turtles), or PO (n = 6 turtles) administration. Blood was collected 3, 6, 24, and 48 h after the first administration to determine the plasma concentration of PZQ using high-performance liquid chromatography coupled to mass spectrometry. Maximum measured R-PZQ concentrations (Cmax) were reached after 6 h. The mean Cmax of the total PZQ (sum of R- and S-PZQ) in the PO-treated EPT group was 1,929 ng/ml. Significantly higher concentrations were measured after IM and SC injection (mean Cmax of total PZQ = 12,715 ng/ml and 10,114 ng/ml, respectively). Transient side effects were evident after IM administration (local swelling and lameness), whereas no adverse drug effects were observed after PO and SC administration. Based on these results and the ease of administration to EPT, SC injection of PZQ at 25 mg/kg q3h times 3 serves as promising treatment application for the future.

Trichuris muris egg-hatching assay for anthelminthic drug discovery and characterization

Trichuriasis is a neglected tropical disease widely distributed among tropical and sub-tropical areas and associated with poverty and lack of access to safe drinking water, sanitation and hygiene. Existing drugs have limited efficacy and face a constant risk of developing resistance, necessitating the search for alternative treatments. However, drug discovery efforts are sparse and little research has been performed on anthelminthic effects on embryonated eggs, the infectious life stage of Trichuris spp. We examined bacterial species dependent egg hatching of the murine model parasite Trichuris muris and identified Escherichia coli, Pseudomonas aeruginosa and Enterobacter hormaechei effective as hatching inducers, resulting in hatching yields of 50-70%. Streptococcus salivarius, reported to be associated with reduced drug efficacy of ivermectin-albendazole coadministration in Trichuris trichiura infected patients, did not promote egg hatching in vitro. We optimized hatching conditions using E. coli grown in luria broth or brain-heart infusion media to reach consistently high hatching yields to provide a sensitive, robust and simple egg-hatching assay. Oxantel pamoate demonstrated the strongest potency in preventing hatching, with an EC50 value of 2-4 μM after 24 h, while pyrantel pamoate, levamisole and tribendimidine exhibited only moderate to weak inhibitory effects. Conversely, all tested benzimidazoles and macrolide anthelminthics as well as emodepside failed to prevent hatching (EC50 > 100 μM). Our study demonstrates that egg-hatching assays complement larval and adult stage drug sensitivity assays, to expand knowledge about effects of current anthelminthics on Trichuris spp. Further, the developed T. muris egg-hatching assay provides a simple and cheap screening tool that could potentially lead to the discovery of novel anthelminthic compounds.

Efficacy and Safety of Moxidectin-Albendazole and Ivermectin-Albendazole Combination Therapy Compared to Albendazole Monotherapy in Adolescents and Adults Infected with Trichuris trichiura: A Randomized, Controlled Superiority Trial

BACKGROUND

The currently recommended benzimidazole monotherapy is insufficiently effective to control infection with the soil-transmitted helminth Trichuris trichiura. Ivermectin-albendazole combination has shown promising, but setting-dependent efficacy, with therapeutic underperformance in Côte d'Ivoire. We evaluated whether moxidectin-albendazole could serve as an alternative to albendazole monotherapy in Côte d'Ivoire.

METHODS

In this community-based, randomized, placebo-controlled, parallel-group superiority trial, individuals aged 12-60 years were screened for T. trichiura eggs in their stool using quadruplicate Kato-Katz thick smears. Diagnostically and clinically eligible participants were randomly assigned (1:1:1) to receive single oral doses of moxidectin (8 mg) and albendazole (400 mg), ivermectin (200 µg/kg) and albendazole (400 mg), or albendazole (400 mg) and placebo. The primary outcome was proportion cured, ie, cure rate (CR), assessed at 2-3 weeks post-treatment. Safety endpoints were assessed pre-treatment and at 3 and 24 hours post-treatment.

RESULTS

For the 210 participants with primary outcome data, we observed CRs of 15.3% in the moxidectin-albendazole arm and 22.5% in the ivermectin-albendazole arm, which did not differ significantly from the CR of 13.4% in the albendazole arm (differences: 1.8%-points [95% confidence interval: -10.1 to 13.6] and 9.1%-points [-3.9 to 21.8], respectively). Most common adverse events were abdominal pain (range across arms: 11.9%-20.9%), headache (4.7%-14.3%), and itching (5.8%-13.1%), which were predominantly mild and transient.

CONCLUSIONS

All therapies showed similar low efficacy in treating trichuriasis in Côte d'Ivoire. Alternative treatment options need to be evaluated, and further analyses should be conducted to understand the lack of enhanced activity of the combination therapies in Côte d'Ivoire.

CLINICAL TRIALS REGISTRATION

NCT04726969.

Praziquantel meets Niclosamide: A dual-drug Antiparasitic Cocrystal

In this paper we report a successful example of combining drugs through cocrystallization. Specifically, the novel solid is formed by two anthelminthic drugs, namely praziquantel (PZQ) and niclosamide (NCM) in a 1:3 molar ratio, and it can be obtained through a sustainable one-step mechanochemical process in the presence of micromolar amounts of methanol. The novel solid phase crystallizes in the monoclinic space group of P21/c, showing one PZQ and three NCM molecules linked through homo- and heteromolecular hydrogen bonds in the asymmetric unit, as also attested by SSNMR and FT-IR results. A plate-like habitus is evident from scanning electron microscopy analysis with a melting point of 202.89 °C, which is intermediate to those of the parent compounds. The supramolecular interactions confer favorable properties to the cocrystal, preventing NCM transformation into the insoluble monohydrate both in the solid state and in aqueous solution. Remarkably, the PZQ - NCM cocrystal exhibits higher anthelmintic activity against in vitro S. mansoni models than corresponding physical mixture of the APIs. Finally, due to in vitro promising results, in vivo preliminary tests on mice were also performed through the administration of minicapsules size M.

Repurposing Know-how for Drug Development: Case Studies from the Swiss Tropical and Public Health Institute

In pursuing novel therapeutic solutions, drug discovery and development rely on efficiently utilising existing knowledge and resources. Repurposing know-how, a strategy that capitalises on previously acquired information and expertise, has emerged as a powerful approach to accelerate drug discovery and development processes, often at a fraction of the costs of de novo developments. For 80 years, collaborating within a network of partnerships, the Swiss Tropical and Public Health Institute (Swiss TPH) has been working along a value chain from innovation to validation and application to combat poverty-related diseases. This article presents an overview of selected know-how repurposing initiatives conducted at Swiss TPH with a particular emphasis on the exploration of drug development pathways in the context of neglected tropical diseases and other infectious diseases of poverty, such as schistosomiasis, malaria and human African trypanosomiasis.

Key Contributions by the Swiss Tropical and Public Health Institute Towards New and Better Drugs for Tropical Diseases

Thanks to its expertise in clinical research, epidemiology, infectious diseases, microbiology, parasitology, public health, translational research and tropical medicine, coupled with deeply rooted partnerships with institutions in low- and middle-income countries (LMICs), the Swiss Tropical and Public Health Institute (Swiss TPH) has been a key contributor in many drug research and development consortia involving academia, pharma and product development partnerships. Our know-how of the maintenance of parasites and their life-cycles in the laboratory, plus our strong ties to research centres and disease control programme managers in LMICs with access to field sites and laboratories, have enabled systems for drug efficacy testing in vitro and in vivo, clinical research, and modelling to support the experimental approaches. Thus, Swiss TPH has made fundamental contributions towards the development of new drugs - and the better use of old drugs - for neglected tropical diseases and infectious diseases of poverty, such as Buruli ulcer, Chagas disease, food-borne trematodiasis (e.g. clonorchiasis, fascioliasis and opisthorchiasis), human African trypanosomiasis, leishmaniasis, malaria, schistosomiasis, soil-transmitted helminthiasis and tuberculosis. In this article, we show case the success stories of molecules to which Swiss TPH has made a substantial contribution regarding their use as anti-infective compounds with the ultimate aim to improve people's health and well-being.

Metabolism of (R)-Praziquantel versus the Activation of a Parasite Transient Receptor Potential Melastatin Ion Channel

Praziquantel (PZQ) is an essential anthelmintic drug recently established to be an activator of a Transient Receptor Potential Melastatin (TRPMPZQ ) ion channel in trematode worms. Bioinformatic, mutagenesis and drug metabolism work indicate that the cyclohexyl ring of PZQ is a key pharmacophore for activation of trematode TRPMPZQ , as well as serving as the primary site of oxidative metabolism which results in PZQ being a short-lived drug. Based on our recent findings, the hydrophobic cleft in schistosome TRPMPZQ defined by three hydrophobic residues surrounding the cyclohexyl ring has little tolerance for polarity. Here we evaluate the in vitro and in vivo activities of PZQ analogues with improved metabolic stability relative to the challenge of maintaining activity on the channel. Finally, an estimation of the respective contribution to the overall activity of both the parent and the main metabolite of PZQ in humans is reported.

Design, Synthesis and Evaluation of Praziquantel Analogues and New Molecular Hybrids as Potential Antimalarial and Anti-Schistosomal Agents

Malaria and schistosomiasis are two of the neglected tropical diseases that persistently wreak havoc worldwide. Although many antimalarial drugs such as chloroquine are readily available, the emergence of drug resistance necessitates the development of new therapies to combat this disease. Conversely, Praziquantel (PZQ) remains the sole effective drug against schistosomiasis, but its extensive use raises concerns about the potential for drug resistance to develop. In this project, the concept of molecular hybridization was used as a strategy to design the synthesis of new molecular hybrids with potential antimalarial and antischistosomal activity. A total of seventeen molecular hybrids and two PZQ analogues were prepared by coupling 6-alkylpraziquanamines with cinnamic acids and cyclohexane carboxylic acid, respectively. The synthesised compounds were evaluated for their antimalarial and antischistosomal activity; while all of the above compounds were inactive against Plasmodium falciparum (IC₅₀ > 6 µM), many were active against schistosomiasis with four particular compounds exhibiting up to 100% activity against newly transformed schistosomula and adult worms at 50 µM. Compared to PZQ, the reference drug, the activity of which is 91.7% at 1 µM, one particular molecular hybrid, compound 32, which bears a para-isopropyl group on the cinnamic acid moiety, exhibited a notable activity at 10 µM (78.2% activity). This compound has emerged as the front runner candidate that might, after further optimization, hold promise as a potential lead compound in the fight against schistosomiasis.

Bridged 1,2,4-Trioxolanes: SnCl4-Catalyzed Synthesis and an In Vitro Study against S. mansoni

A synthesis of bridged 1,2,4-trioxolanes (bridged ozonides) from 1,5-diketones and hydrogen peroxide catalyzed by SnCl₄ was developed. It was shown that the ratio of target ozonides can be affected by the application of SnCl₄ as a catalyst and varying the solvent. A wide range of bridged 1,2,4-trioxolanes (ozonides) was obtained in yields from 50 to 84%. The ozonide cycle was moderately resistant to the reduction of the ester group near the peroxide cycle to alcohol with LiAlH₄. The bridged ozonides were evaluated for their antischistosomal activity. These ozonides exhibited a very high activity against newly transformed schistosomula and adult Schistosoma mansoni.

Evaluation of 43 species of Congolese medicinal plants used traditionally for the treatment of schistosomiasis leading to the isolation of an anti-schistosomal phaeophytin from Pseudolachnostylis maprouneifolia Pax

ETHNOPHARMACOLOGICAL RELEVANCE

Schistosomiasis (bilharzia) is an important, prevalent and neglected tropical disease for which new treatments are urgently required. In the DR Congo and other sub- and tropical countries, traditional medicines are widely used for the control of schistosomiasis.

AIM OF STUDY

To evaluate 43 Congolese plant species used traditionally for the treatment of urogenital schistosomiasis against Schistosoma mansoni.

MATERIALS AND METHODS

Methanolic extracts were screened against S. mansoni newly transformed schistosomula (NTS). Three of the most active extracts were evaluated for acute oral toxicity in guinea pigs and activity guided fractionation of the least toxic was carried out using S. mansoni NTS and adult stages. An isolated compound was identified by means of spectroscopic techniques.

RESULTS

Thirty-nine of 62 extracts killed S. mansoni NTS at 100μg/mL and 7 extracts were active at ≥ 90% at 25μg/mL; 3 extracts were selected for acute oral toxicity evaluation; the least toxic of these, Pseudolachnostylis maprouneifolia leaf was then subjected to activity-guided fractionation. 17³-ethoxyphaeophorbide a (1) was isolated as an active compound with 56% activity against NTS at 50 μg/mL and 22.5% activity against adult S. mansoni at 100 μg/mL but these activities are significantly less than those of the parent fractions suggesting that other active compounds are also present and/or that synergistic interactions are taking place.

CONCLUSION

This study has identified 39 plant extracts with activity against S. mansoni NTS lending support to their traditional use in the treatment of schistosomiasis for which new treatments are urgently needed. P. maprouneifolia leaf extract was found to have potent anti-schistosomal activity and low in vivo oral toxicity in guinea pigs; activity-guided fractionation resulted in the isolation of an active compound, 17³-ethoxyphaeophorbide a. Phaeophorbides may merit exploration as potential anti-schistosomal agents and further work on plant species shown to have potent activity against S. mansoni NTS in this study would be worthwhile.

Emodepside for Trichuris trichiura and Hookworm Infection

BACKGROUND

Current treatments for soil-transmitted helminth infections in humans have low efficacy against Trichuris trichiura. Emodepside - a drug in veterinary use and under development for the treatment of onchocerciasis in humans - is a leading therapeutic candidate for soil-transmitted helminth infection.

METHODS

We conducted two phase 2a, dose-ranging, randomized, controlled trials to evaluate the efficacy and safety of emodepside against T. trichiura and hookworm infections. We randomly assigned, in equal numbers, adults 18 to 45 years of age in whom T. trichiura or hookworm eggs had been detected in stool samples to receive emodepside, at a single oral dose of 5, 10, 15, 20, 25, or 30 mg; albendazole, at a single oral dose of 400 mg; or placebo. The primary outcome was the percentage of participants who were cured of T. trichiura or hookworm infection (the cure rate) with emodepside 14 to 21 days after treatment, determined with the use of the Kato-Katz thick-smear technique. Safety was assessed 3, 24, and 48 hours after the receipt of treatment or placebo.

RESULTS

A total of 266 persons were enrolled in the T. trichiura trial and 176 in the hookworm trial. The predicted cure rate against T. trichiura in the 5-mg emodepside group (85% [95% confidence interval {CI}, 69 to 93]; 25 of 30 participants) was higher than the predicted cure rate in the placebo group (10% [95% CI, 3 to 26]; 3 of 31 participants) and the observed cure rate in the albendazole group (17% [95% CI, 6 to 35]; 5 of 30 participants). A dose-dependent relationship was shown in participants with hookworm: the observed cure rate was 32% (95% CI, 13 to 57; 6 of 19 participants) in the 5-mg emodepside group and 95% (95% CI, 74 to 99.9; 18 of 19 participants) in the 30-mg emodepside group; the observed cure rates were 14% (95% CI, 3 to 36; 3 of 21 participants) in the placebo group and 70% (95% CI, 46 to 88; 14 of 20 participants) in the albendazole group. In the emodepside groups, headache, blurred vision, and dizziness were the most commonly reported adverse events 3 and 24 hours after treatment; the incidence of events generally increased in a dose-dependent fashion. Most adverse events were mild in severity and were self-limited; there were few moderate and no serious adverse events.

CONCLUSIONS

Emodepside showed activity against T. trichiura and hookworm infections. (Funded by the European Research Council; ClinicalTrials.gov number, NCT05017194.).

Development of a hookworm egg hatching assay to determine the ovicidal effects of anthelminthics

BACKGROUND

Few anthelminthics are currently available, manifesting the urgent need for new treatment options. In vitro profiling of current anthelminthics against larval and adult stage helminths displayed varying effects on closely related worm species and between life stages of the same species. Conversely, limited research has been performed on the egg stage of human hookworms, and the effects of investigational compounds on the egg stage are not routinely assessed.

METHODS

We profiled the development and hatching of Heligmosomoides polygyrus, Ancylostoma duodenale and Necator americanus eggs isolated from rodent faeces in liquid media with various nutrient levels, osmolar concentrations, and acidities in dependence on incubation temperature and light exposure. Incubation conditions were optimised to allow the study of drug effect on immature and embryonated eggs. We analysed concentration-effect relationships of commercially available anthelminthics over 72 h.

RESULTS

Rapid embryonation and hatching were observed at room temperature with and without light exposure without nutrient supplementation in a wide range of acidities. Hookworms hatched optimally at room temperature in PBS achieving > 75% hatching over 34 h. Developmental delays were seen when eggs were stored at 4 °C with no effect on viability. Similar delays were also seen with increased osmolar concentrations resulting in decreased viability. Benzimidazole anthelminthics effectively reduced the viability and prevented hatching of hookworm eggs, with albendazole and thiabendazole eliciting particularly potent effects at EC₅₀ values below 1 µM. Macrolide anthelminthics as well as emodepside, oxantel pamoate, and pyrantel pamoate were inactive while monepantel, levamisole, and tribendimidine displayed varied potencies among the hookworm species.

CONCLUSION

The presented egg-hatching assay will complement ongoing anthelminthic drug discovery and allow a full characterisation of drug activity against all life stages. In the development and application of the egg-hatching assay, good accordance was observed between the three hookworm species evaluated. Marketed anthelminthics show differences of drug action compared to larval and adult stages highlighting the importance of profiling drug activity against all life stages.

A general framework to support cost-efficient fecal egg count methods and study design choices for large-scale STH deworming programs-monitoring of therapeutic drug efficacy as a case study

BACKGROUND

Soil-transmitted helminth (STH) control programs currently lack evidence-based recommendations for cost-efficient survey designs for monitoring and evaluation. Here, we present a framework to provide evidence-based recommendations, using a case study of therapeutic drug efficacy monitoring based on the examination of helminth eggs in stool.

METHODS

We performed an in-depth analysis of the operational costs to process one stool sample for three diagnostic methods (Kato-Katz, Mini-FLOTAC and FECPAKG2). Next, we performed simulations to determine the probability of detecting a truly reduced therapeutic efficacy for different scenarios of STH species (Ascaris lumbricoides, Trichuris trichiura and hookworms), pre-treatment infection levels, survey design (screen and select (SS); screen, select and retest (SSR) and no selection (NS)) and number of subjects enrolled (100-5,000). Finally, we integrated the outcome of the cost assessment into the simulation study to estimate the total survey costs and determined the most cost-efficient survey design.

PRINCIPAL FINDINGS

Kato-Katz allowed for both the highest sample throughput and the lowest cost per test, while FECPAKG2 required both the most laboratory time and was the most expensive. Counting of eggs accounted for 23% (FECPAKG2) or ≥80% (Kato-Katz and Mini-FLOTAC) of the total time-to-result. NS survey designs in combination with Kato-Katz were the most cost-efficient to assess therapeutic drug efficacy in all scenarios of STH species and endemicity.

CONCLUSIONS/SIGNIFICANCE

We confirm that Kato-Katz is the fecal egg counting method of choice for monitoring therapeutic drug efficacy, but that the survey design currently recommended by WHO (SS) should be updated. Our generic framework, which captures laboratory time and material costs, can be used to further support cost-efficient choices for other important surveys informing STH control programs. In addition, it can be used to explore the value of alternative diagnostic techniques, like automated egg counting, which may further reduce operational costs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03465488.

Correlation of Cytokines with Parasitic Infections, Undernutrition and Micronutrient Deficiency among Schoolchildren in Rural Tanzania: A Cross-Sectional Study

Malnutrition and parasitic infections are often interconnected in a vicious cycle. Malnutrition can lead to changes in immune response, which may affect cytokine concentrations and potentially increase susceptibility to infections. In turn, parasitic infections can exacerbate malnutrition by impairing nutrient absorption. This cross-sectional study aimed to explore this interplay. Schoolchildren aged 6-12 years living in rural Tanzania (n = 120) provided blood, stool and urine samples to determine the relationship between cytokine concentrations (interleukin 4 (IL-4), interferon gamma (IFNγ) and interleukin 17A (IL-17A)), parasitic infections, undernutrition and micronutrient deficiency adjusting for sex, age, inflammatory markers, socioeconomic status and school categories. All schoolchildren had a normal blood cell count. The concentration of IL-4 was significantly higher in schoolchildren diagnosed with stunting, Schistosoma mansoni infection, a high C-reactive protein concentration, nausea, poor housing and increasing age. The concentration of IFNγ was associated with Plasmodium falciparum and Entamoeba histolytica/Entamoeba dispar/Entamoeba moshkovskii infections, vitamin A deficiency, attending the most remote schools and low socioeconomic status. Our study confirms a potential relationship between cytokine concentrations and parasitic infections, malnutrition and low socioeconomic status. A better understanding of long-term effects of parasitic infections and malnutrition on the immune function could help in designing tailored and effective interventions.

Ivermectin and moxidectin against soil-transmitted helminth infections

Ivermectin and moxidectin, two macrocyclic lactones, are potent antiparasitic drugs currently registered and mainly used against filarial diseases; however, their potential value for improved soil-transmitted helminth (STH) control has been acknowledged. This review provides insights on recent studies evaluating the efficacy of ivermectin and moxidectin as single or coadministered therapy against human soil-transmitted helminthiases (including Strongyloides stercoralis infections) and on pharmacokinetic/pharmacodynamic parameters measured in treated populations. Furthermore, we discuss current gaps for research, highlight advantages - but also existing challenges - for uptake of ivermectin and/or moxidectin treatment schemes into routine STH control in endemic countries.

In Vitro and In Vivo Antischistosomal Activity Profiling and Pharmacokinetics of Ozonide Carboxylic Acids

Praziquantel, the only drug in clinical use for the treatment and control of schistosomiasis, is inactive against developing infections. Ozonides are synthetic peroxide derivatives inspired by the naturally occurring artemisinin and show particularly promising activity against juvenile schistosomes. We conducted an in-depth characterization of the in vitro and in vivo antischistosomal activity and pharmacokinetics of lead ozonide carboxylic acid OZ418 and four of its active analogs. In vitro, the ozonides featured rapid and consistent activity against schistosomula and adult schistosomes at double-digit micromolar EC50 values. Potency did not vary considerably between Schistosoma spp. The zwitterionic OZ740 and OZ772 were more active in vivo compared to their non-amphoteric carboxylic acids OZ418 and OZ748, despite their much lower systemic plasma exposure (AUC). The most active compound in vivo was ethyl ester OZ780, which was rapidly transformed to its parent zwitterion OZ740 and achieved ED50 values of 35 ± 2.4 and 29 ± 2.4 mg/kg against adult and juvenile Schistosoma mansoni, respectively. Ozonide carboxylic acids represent promising candidates for further optimization and development due to their good efficacy against both life stages together with their broad activity range against all relevant parasite species.

Co-Crystalline Solid Solution Affords a High-Soluble and Fast-Absorbing Form of Praziquantel

Praziquantel (PZQ) is a chiral class-II drug, and it is used as a racemate for the treatment of schistosomiasis. The knowledge of several cocrystals with dicarboxylic acids has prompted the realization of solid solutions of PZQ with both enantiomers of malic acid and tartaric acid. Here, the solid form landscape of such a six-component system has been investigated. In the process, two new cocrystals were structural-characterized and three non-stoichiometric, mixed crystal forms identified and isolated. Thermal and solubility analysis indicates a fourfold solubility advantage for the newly prepared solid solutions over the pure drug. In addition, a pharmacokinetic study was conducted in rats, which involved innovative mini-capsules for the oral administration of the solid samples. The available data indicate that the faster dissolution rate of the solid solutions translates in faster absorption of the drug and helps maintain a constant steady-state concentration.

Efficacy and safety of moxidectin and albendazole compared with ivermectin and albendazole coadministration in adolescents infected with Trichuris trichiura in Tanzania: an open-label, non-inferiority, randomised, controlled, phase 2/3 trial

BACKGROUND

Control efforts against soil-transmitted helminths focus on preventive chemotherapy with albendazole and mebendazole, however these drugs yield unsatisfactory results against Trichuris trichiura infections. We aimed to assess the efficacy and safety of moxidectin and albendazole compared with ivermectin and albendazole against T trichiura in adolescents living on Pemba Island, Tanzania.

METHODS

This open-label, non-inferiority, randomised, controlled, phase 2/3 trial was done in four secondary schools (Kilindi, Kwale, Ndagoni [Chake Chake District], and Kiuyu [Wete District]) on Pemba Island, Tanzania. Adolescents aged 12-19 years who tested positive for T trichiura in at least two of four Kato-Katz slides with a mean infection intensity of 48 eggs per gram (EPG) of stool or higher were considered for inclusion. Participants were randomly assigned (21:21:2:2:8) to five treatment groups (8 mg moxidectin and 400 mg albendazole [group 1], 200 μg/kg ivermectin and 400 mg albendazole [group 2], 400 mg albendazole [group 3], 200 μg/kg ivermectin [group 4], or 8 mg moxidectin [group 5]) using a computer-generated randomisation code, stratified by baseline T trichiura infection intensity. Study site investigators and participants were not masked to study treatment; however, allocation was concealed to participants. The primary outcome was egg reduction rate (ERR) of T trichiura 14-21 days after treatment in the available case population. Moxidectin and albendazole was considered non-inferior to ivermectin and albendazole (control group) when the lower limit of the two-sided 95% CI of the difference was higher than the non-inferiority margin of -2 percentage points. This study is registered with ClinicalTrials.gov, NCT04700423.

FINDINGS

Between March 1 and April 30, 2021, 771 participants were assessed for eligibility. 221 (29%) of 771 participants were ineligible and a further 14 (2%) were excluded. 207 (39%) of 536 participants were randomly assigned to moxidectin and albendazole, 211 (39%) to ivermectin and albendazole, 19 (4%) to albendazole, 19 (4%) to ivermectin, and 80 (15%) to moxidectin. Primary outcome data were available for all 536 participants. The geometric mean ERR of T trichiura after 14-21 days was 96·8% (95% CI 95·8 to 97·6) with moxidectin and albendazole and 99·0% (98·7 to 99·3) with ivermectin and albendazole (difference of -2·2 percentage points [-4·2 to -1·4]). No serious adverse events were reported during the study. The most reported adverse events were headache (160 [34%] of 465), abdominal pain (78 [17%]), itching (44 [9%]), and dizziness (26 [6%]).

INTERPRETATION

Our findings show inferiority of moxidectin and albendazole to ivermectin and albendazole against T trichiura. However, given the high efficacy, moxidectin coadministration might complement treatment progammes, particularly in areas in which ivermectin is not available FUNDING: Bill and Melinda Gates Foundation, reference number OPP1153928.

Chemically Diverse S. mansoni HDAC8 Inhibitors Reduce Viability in Worm Larval and Adult Stages

Schistosoma mansoni HDAC8 is a reliable target to fight schistosomiasis, and several inhibitors have been reported in the literature up to now. Nevertheless, only a few displayed selectivity over the human deacetylases and some exhibited very low or no activity against parasite larvae and/or adult worms. We report here the in vitro enzyme and biological activity of a small library of HDAC inhibitors from our lab, in many cases exhibiting submicromolar/nanomolar potency against smHDAC8 and diverse degrees of selectivity over hHDAC1 and/or hHDAC6. Such compounds were tested against schistosomula, and a selection of them against the adult forms of S. mansoni, to detect their effect on viability. Some of them showed the highest viability reduction for the larval stage with IC₅₀ values around 1 μM and/or displayed ∼40-50 % activity in adult worms at 10 μM, joined to moderate to no toxicity in human fibroblast MRC-5 cells.

Correction: A systematic review and an individual patient data meta-analysis of ivermectin use in children weighing less than fifteen kilograms: Is it time to reconsider the current contraindication?

[This corrects the article DOI: 10.1371/journal.pntd.0009144.].

High Sensitivity of Mobile Phone Microscopy Screening for Schistosoma haematobium in Azaguié, Côte d'Ivoire

Schistosomiasis infections continue to impact African settings disproportionately, and there is an urgent need for novel tools to evaluate infection control and elimination strategies at the community level. Mobile phone microscopes are portable and semiautomated devices with multiple applications for screening neglected tropical diseases. In a community-based schistosomiasis screening program in Azaguié, Côte d'Ivoire, mobile phone microscopy demonstrated a sensitivity of 85.7% (95% CI: 69.7-95.2%) and specificity of 93.3% (95% CI: 87.7-96.9%) for Schistosoma haematobium identification compared with conventional light microscopy, and 95% sensitivity (95% CI: 74.1-99.8%) with egg concentrations of five or more per 10 mL of urine. Mobile phone microscopy is a promising tool for schistosomiasis control and elimination efforts.

Helminth infections: Enabling the World Health Organization Road Map

Helminthiases are considered among the most persistent public health problems. Control and/or elimination remains a global health challenge and the World Health Organization Road Map highlights critical gaps and actions required to reach the 2030 targets, among them the need for new and more effective treatment options. Stronger collaborations across different fields are required to reach these goals. The helminth elimination platform is one example of how knowledge of two different disease areas can be aligned to fuse expertise and break disease silos.

Medicinal Plant Preparations Administered by Botswana Traditional Health Practitioners for Treatment of Worm Infections Show Anthelmintic Activities

Schistosomiasis and soil-transmitted helminths are some of the priority neglected tropical diseases (NTDs) targeted for elimination by the World Health Organization (WHO). They are prevalent in Botswana and although Botswana has begun mass drug administration with the hope of eliminating soil-transmitted helminths as a public health problem, the prevalence of schistosomiasis does not meet the threshold required to warrant large-scale interventions. Although Botswana has a modern healthcare system, many people in Botswana rely on traditional medicine to treat worm infections and schistosomiasis. In this study, ten plant species used by traditional health practitioners against worm infections were collected and tested against Ancylostoma ceylanicum (zoonotic hookworm), Heligmosomoides polygyrus (roundworm of rodents), Necator americanus (New World hookworm), Schistosoma mansoni (blood fluke) [adult and newly transformed schistosomula (NTS)], Strongyloides ratti (threadworm) and Trichuris muris (nematode parasite of mice) in vitro. Extracts of two plants, Laphangium luteoalbum and Commiphora pyaracanthoides, displayed promising anthelmintic activity against NTS and adult S. mansoni, respectively. L. luteoalbum displayed 85.4% activity at 1 μg/mL against NTS, while C. pyracanthoides displayed 78.5% activity against adult S. mansoni at 10 μg/mL.

Thermal proteome profiling reveals Haemonchus orphan protein HCO_011565 as a target of the nematocidal small molecule UMW-868

Parasitic roundworms (nematodes) cause destructive diseases, and immense suffering in humans and other animals around the world. The control of these parasites relies heavily on anthelmintic therapy, but treatment failures and resistance to these drugs are widespread. As efforts to develop vaccines against parasitic nematodes have been largely unsuccessful, there is an increased focus on discovering new anthelmintic entities to combat drug resistant worms. Here, we employed thermal proteome profiling (TPP) to explore hit pharmacology and to support optimisation of a hit compound (UMW-868), identified in a high-throughput whole-worm, phenotypic screen. Using advanced structural prediction and docking tools, we inferred an entirely novel, parasite-specific target (HCO_011565) of this anthelmintic small molecule in the highly pathogenic, blood-feeding barber’s pole worm, and in other socioeconomically important parasitic nematodes. The “hit-to-target” workflow constructed here provides a unique prospect of accelerating the simultaneous discovery of novel anthelmintics and associated parasite-specific targets.

Modulation of Host-Parasite Interactions with Small Molecules Targeting Schistosoma mansoni microRNAs

Parasites use different strategies of communication with their hosts. One communication channel that has been studied in recent years is the use of vesicle microRNAs to influence the host immune system by trematodes. sma-microRNA-10, secreted from Schistosoma mansoni, has been shown to influence the fate of host T-cells through manipulation of the NF-κB pathway. We have identified low molecular weight tool compounds that can interfere with this microRNA-mediated manipulation of the host immune system. We used a fragment-based screening approach by means of nuclear magnetic resonance (NMR) to identify binders to the precursor of the parasite sma-microRNA-10 present in their extracellular vesicles. The small fragments identified were used to select larger molecules. These molecules were shown to counteract the inhibition of NF-κB activity by sma-microRNA-10 in cell-based assays.

Modeling the effect of different drugs and treatment regimen for hookworm on cure and egg reduction rates taking into account diagnostic error

BACKGROUND

Hookworm infections, caused by Ancylostoma duodenale and Necator americanus, are of considerable public health importance. The World Health Organization recommends preventive chemotherapy as the key strategy for morbidity control. Meta-analyses have been conducted to estimate treatment efficacy of available drugs and drug combinations. However, in most studies, the relation between the diagnostic error and infection intensity have not been considered, resulting in an overestimation of cure rates (CRs).

METHODOLOGY

A Bayesian model was developed to compare the 'true' CR and egg reduction rate of different treatment regimens for hookworm infections taking into account the error of the recommended Kato-Katz thick smear diagnostic technique. It was fitted to the observed egg count data which was linked to the distribution of worms, considered the day-to-day variation of hookworm egg excretion and estimated the infection intensity-dependent sensitivity. The CR was obtained by defining the prevalence of infection at follow-up as the probability of having at least one fertilized female worm. The model was applied to individual-level egg count data available from 17 treatments and six clinical trials.

PRINCIPAL FINDINGS

Taking the diagnostic error into account resulted in considerably lower CRs than previously reported. Overall, of all treatments analyzed, mebendazole administered in six dosages of 100 mg each was the most efficacious treatment with a CR of 88% (95% Bayesian credible interval: 79-95%). Furthermore, diagnostic sensitivity varied with the infection intensity and sampling effort. For an infection intensity of 50 eggs per gram of stool, the sensitivity is close to 60%; for two Kato-Katz thick smears it increased to approximately 76%.

CONCLUSIONS/SIGNIFICANCE

Our model-based estimates provide the true efficacy of different treatment regimens against hookworm infection taking into account the diagnostic error of the Kato-Katz method. Estimates of the diagnostic sensitivity for different number of stool samples and thick smears are obtained. To accurately assess efficacy in clinical trials with the Kato-Katz method, at least two stool samples on consecutive days should be collected.

Egg-laying and locomotory screens with C. elegans yield a nematode-selective small molecule stimulator of neurotransmitter release

Nematode parasites of humans, livestock and crops dramatically impact human health and welfare. Alarmingly, parasitic nematodes of animals have rapidly evolved resistance to anthelmintic drugs, and traditional nematicides that protect crops are facing increasing restrictions because of poor phylogenetic selectivity. Here, we exploit multiple motor outputs of the model nematode C. elegans towards nematicide discovery. This work yielded multiple compounds that selectively kill and/or immobilize diverse nematode parasites. We focus on one compound that induces violent convulsions and paralysis that we call nementin. We find that nementin stimulates neuronal dense core vesicle release, which in turn enhances cholinergic signaling. Consequently, nementin synergistically enhances the potency of widely-used non-selective acetylcholinesterase (AChE) inhibitors, but in a nematode-selective manner. Nementin therefore has the potential to reduce the environmental impact of toxic AChE inhibitors that are used to control nematode infections and infestations.

A C. elegans-based screening approach identifies nementin as a nematode-selective nematicide that can be used synergistically with acetylcholinesterase inhibitors

Phenotypic Screening of Histone Deacetylase (HDAC) Inhibitors against Schistosoma mansoni

Schistosomiasis is a prevalent yet neglected tropical parasitic disease caused by the Schistosoma genus of blood flukes. Praziquantel is the only currently available treatment, hence drug resistance poses a major threat. Recently, histone deacetylase 8 (HDAC8) selective inhibitors have been proposed as a viable treatment for schistosomiasis. Herein, we report the phenotypic screening of a focused library of small molecules of varying HDAC isozyme-inhibition profiles, including eight HDAC8 inhibitors with >10-fold selectivity in comparable functional inhibition assays and IC₅₀ values against HDAC8<100 nM. HDAC8-selective inhibitors showed the lowest potency against Schistosoma mansoni newly transformed schistosomula (NTS). Pan-HDAC inhibitors MMH258, MMH259, and MMH373, as assessed by functional inhibition assays, with minimal or no-observed hHDAC8 and SmHDAC8 activities, were active against both NTS (MMH258, IC₅₀ =1.5 μM; MMH259, IC₅₀ =2.3 μM) and adult S. mansoni (MMH258, IC₅₀ =2.1 μM; MMH373, IC₅₀ =3.4 μM). Our results indicate that neither hHDAC8 nor SmHDAC8 activity were directly correlated to their NTS and adult S. mansoni activities.

Egg excretion indicators for the measurement of soil-transmitted helminth response to treatment

Background

Periodic administration of anthelmintic drugs is a cost-effective intervention for morbidity control of soil-transmitted helminth (STH) infections. However, with programs expanding, drug pressure potentially selecting for drug-resistant parasites increases. While monitoring anthelmintic drug efficacy is crucial to inform country control program strategies, different factors must be taken into consideration that influence drug efficacy and make it difficult to standardize treatment outcome measures. We aimed to identify suitable approaches to assess and compare the efficacy of different anthelmintic treatments.

Methodology

We built an individual participant-level database from 11 randomized controlled trials and two observational studies in which subjects received single-agent or combination therapy, or placebo. Eggs per gram of stool were calculated from egg counts at baseline and post-treatment. Egg reduction rates (ERR; based on mean group egg counts) and individual-patient ERR (iERR) were utilized to express drug efficacy and analyzed after log-transformation with a linear mixed effect model. The analyses were separated by follow-up duration (14–21 and 22–45 days) after drug administration.

Principal findings

The 13 studies enrolled 5,759 STH stool-positive individuals; 5,688 received active medication or placebo contributing a total of 11,103 STH infections (65% had two or three concurrent infections), of whom 3,904 (8,503 infections) and 1,784 (2,550 infections) had efficacy assessed at 14–21 days and 22–45 days post-treatment, respectively. Neither the number of helminth co-infections nor duration of follow-up affected ERR for any helminth species. The number of participants treated with single-dose albendazole was 689 (18%), with single-dose mebendazole 658 (17%), and with albendazole-based co-administrations 775 (23%). The overall mean ERR assessed by day 14–21 for albendazole and mebendazole was 94.5% and 87.4%, respectively on Ascaris lumbricoides, 86.8% and 40.8% on hookworm, and 44.9% and 23.8% on Trichuris trichiura. The World Health Organization (WHO) recommended criteria for efficacy were met in 50%, 62%, and 33% studies of albendazole for A. lumbricoides, T. trichiura, and hookworm, respectively and 25% of mebendazole studies. iERR analyses showed similar results, with cure achieved in 92% of A. lumbricoides-infected subjects treated with albendazole and 93% with mebendazole; corresponding figures for hookworm were 70% and 17%, and for T. trichiura 22% and 20%.

Conclusions/significance

Combining the traditional efficacy assessment using group averages with individual responses provides a more complete picture of how anthelmintic treatments perform. Most treatments analyzed fail to meet the WHO minimal criteria for efficacy based on group means. Drug combinations (i.e., albendazole-ivermectin and albendazole-oxantel pamoate) are promising treatments for STH infections.

To reduce morbidity caused by parasitic worm infections, hundreds of million treatments are given to children every year through repeat cycles of single-dose deworming drugs. This strategy works, and is cost-effective. However, the downside is drug pressure that potentially selects for resistant parasites. Hence, there is a need to monitor treatment efficacy, and do so in a way that allows us to pick up early any deterioration in treatment effects. We analyzed data from 13 trials that enrolled 5,688 infected people who were given deworming drugs or a placebo, by calculating the reduction in worm egg counts in their stools from before to 14–21 and 22–45 days after treatment using different methods. We found that many people harbored more than one species of parasitic worms. Neither multiple infections, nor the intensity of infection, or whether effects were measured earlier or later, appeared to affect treatment efficacy. We also found that the most common treatments are only partially effective. The World Health Organization recommended criteria for efficacy were met in 50%, 62%, and 33% studies of albendazole for roundworm, whipworm, and hookworm, respectively and in 25% of mebendazole studies. In addition, we confirmed that combinations of albendazole-ivermectin and albendazole-oxantel pamoate are promising treatments.

Benzimidazole and aminoalcohol derivatives show in vitro anthelmintic activity against Trichuris muris and Heligmosomoides polygyrus

Background

Infections by gastrointestinal nematodes cause significant economic losses and disease in both humans and animals worldwide. The discovery of novel anthelmintic drugs is crucial for maintaining control of these parasitic infections.

Methods

For this purpose, the aim of the present study was to evaluate the potential anthelmintic activity of three series of compounds against the gastrointestinal nematodes Trichuris muris and Heligmosomoides polygyrus in vitro. The compounds tested were derivatives of benzimidazole, lipidic aminoalcohols and diamines. A primary screening was performed to select those compounds with an ability to inhibit T. muris L₁ motility by > 90% at a single concentration of 100 µM; then, their respective IC₅₀ values were calculated. Those compounds with IC₅₀ < 10 µM were also tested against the adult stage of T. muris and H. polygyrus at a single concentration of 10 µM.

Results

Of the 41 initial compounds screened, only compounds AO14, BZ6 and BZ12 had IC₅₀ values < 10 µM on T. muris L₁ assay, showing IC₅₀ values of 3.30, 8.89 and 4.17 µM, respectively. However, only two of them displayed activity against the adult stage of the parasites: BZ12 killed 81% of adults of T. muris (IC₅₀ of 8.1 µM) and 53% of H. polygyrus while BZ6 killed 100% of H. polygyrus adults (IC₅₀ of 5.3 µM) but only 17% of T. muris.

Conclusions

BZ6 and BZ12 could be considered as a starting point for the synthesis of further structurally related compounds.

Graphical Abstract

Improving translational power in antischistosomal drug discovery

Schistosomiasis is a poverty-associated tropical disease caused by blood dwelling trematodes that threaten approximately 10% of the world population. Praziquantel, the sole drug currently available for treatment, is insufficient to eliminate the disease and the clinical drug development pipeline is empty. Here, we review the characteristics of the patent Schistosoma mansoni mouse model used for in vivo antischistosomal drug discovery, highlighting differences in the experimental set-up across research groups and their potential influence on experimental results. We explore the pharmacokinetic/pharmacodynamic relationship of selected drug candidates, showcasing opportunities to improve the drug profile to accelerate the transition from the early drug discovery phase to new clinical candidates.

Effects of Structurally Different HDAC Inhibitors against Trypanosoma cruzi, Leishmania, and Schistosoma mansoni

Neglected tropical diseases (NTDs), including trypanosomiasis, leishmaniasis, and schistosomiasis, result in a significant burden in terms of morbidity and mortality worldwide every year. Current antiparasitic drugs suffer from several limitations such as toxicity, no efficacy toward all of the forms of the parasites’ life cycle, and/or induction of resistance. Histone-modifying enzymes play a crucial role in parasite growth and survival; thus, the use of epigenetic drugs has been suggested as a strategy for the treatment of NTDs. We tested structurally different HDACi 1–9, chosen from our in-house library or newly synthesized, against Trypanosoma cruzi, Leishmania spp, and Schistosoma mansoni. Among them, 4 emerged as the most potent against all of the tested parasites, but it was too toxic against host cells, hampering further studies. The retinoic 2′-aminoanilide 8 was less potent than 4 in all parasitic assays, but as its toxicity is considerably lower, it could be the starting structure for further development. In T. cruzi, compound 3 exhibited a single-digit micromolar inhibition of parasite growth combined with moderate toxicity. In S. mansoni, 4’s close analogs 17–20 were tested in new transformed schistosomula (NTS) and adult worms displaying high death induction against both parasite forms. Among them, 17 and 19 exhibited very low toxicity in human retinal pigment epithelial (RPE) cells, thus being promising compounds for further optimization.

Development of Praziquantel sulphonamide derivatives as antischistosomal drugs

The almost empty armamentarium to treat schistosomiasis, a neglected parasitic disorder caused by trematode flatworms of the genus Schistosoma, except Praziquantel (PZQ), urged to find new alternatives to fight this infection. Carbonic Anhydrase from Schistosoma mansoni (SmCA) is a possible new target against this nematode. Here, we propose new PZQ derivatives bearing a primary sulphonamide group in order to obtain hybrid drugs. All compounds were evaluated for their inhibition profiles on both humans and Schistosoma CAs, X-ray crystal data of SmCA and hCA II in adduct with some inhibitors were obtained allowing the understanding of the main structural factors responsible of activity. The compounds showed in vitro inhibition of immature and adult S. mansoni, but further optimisation is required for improved activity.

Albatrellus confluens (Alb. & Schwein.) Kotl. & Pouz.: Natural Fungal Compounds and Synthetic Derivatives with In Vitro Anthelmintic Activities and Antiproliferative Effects against Two Human Cancer Cell Lines

Neglected tropical diseases affect the world's poorest populations with soil-transmitted helminthiasis and schistosomiasis being among the most prevalent ones. Mass drug administration is currently the most important control measure, but the use of the few available drugs is giving rise to increased resistance of the parasites to the drugs. Different approaches are needed to come up with new therapeutic agents against these helminths. Fungi are a source of secondary metabolites, but most fungi remain largely uninvestigated as anthelmintics. In this report, the anthelmintic activity of Albatrellus confluens against Caenorhabditis elegans was investigated using bio-assay guided isolation. Grifolin (1) and neogrifolin (2) were identified as responsible for the anthelmintic activity. Derivatives 4-6 were synthesized to investigate the effect of varying the prenyl chain length on anthelmintic activity. The isolated compounds 1 and 2 and synthetic derivatives 4-6, as well as their educts 7-10, were tested against Schistosoma mansoni (adult and newly transformed schistosomula), Strongyloides ratti, Heligmosomoides polygyrus, Necator americanus, and Ancylostoma ceylanicum. Prenyl-2-orcinol (4) and geranylgeranyl-2-orcinol (6) showed promising activity against newly transformed schistosomula. The compounds 1, 2, 4, 5, and 6 were also screened for antiproliferative or cytotoxic activity against two human cancer lines, viz. prostate adenocarcinoma cells (PC-3) and colorectal adenocarcinoma cells (HT-29). Compound 6 was determined to be the most effective against both cell lines with IC₅₀ values of 16.1 µM in PC-3 prostate cells and 33.7 µM in HT-29 colorectal cells.

Real-time and automated monitoring of antischistosomal drug activity profiles for screening of compound libraries

Schistosomiasis is a neglected tropical disease that affects over 200 million people annually. As the antischistosomal drug pipeline is currently empty, repurposing of compound libraries has become a source for accelerating drug development, which demands the implementation of high-throughput and efficient screening strategies. Here, we present a parallelized impedance-based platform for continuous and automated viability evaluation of Schistosoma mansoni schistosomula in 128 microwells during 72 h to identify antischistosomal hits in vitro. By initially screening 57 repurposed compounds against larvae, five drugs are identified, which reduce parasite viability by more than 70%. The activity profiles of the selected drugs are then investigated via real-time dose-response monitoring, and four compounds reveal high potency and rapid action, which renders them suitable candidates for follow-up tests against adult parasites. The study shows that our device is a reliable tool for real-time drug screening analysis of libraries to identify new promising therapeutics against schistosomiasis.

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Scalable, plastic microwell chip with integrated platinum electrodes

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Automated impedance-based recording of 128 microwell units in parallel

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Continuous monitoring of in vitro drug library efficacy on schistosomula for 72 h

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Identification of four fast-acting antischistosomal drugs for in vivo testing

Whole-organism phenotypic screening methods used in early-phase anthelmintic drug discovery

Diseases caused by parasitic helminths (worms) represent a major global health burden in both humans and animals. As vaccines against helminths have yet to achieve a prominent role in worm control, anthelmintics are the primary tool to limit production losses and disease due to helminth infections in both human and veterinary medicine. However, the excessive and often uncontrolled use of these drugs has led to widespread anthelmintic resistance in these worms - particularly of animals - to almost all commercially available anthelmintics, severely compromising control. Thus, there is a major demand for the discovery and development of new classes of anthelmintics. A key component of the discovery process is screening libraries of compounds for anthelmintic activity. Given the need for, and major interest by the pharmaceutical industry in, novel anthelmintics, we considered it both timely and appropriate to re-examine screening methods used for anthelmintic discovery. Thus, we reviewed current literature (1977-2021) on whole-worm phenotypic screening assays developed and used in academic laboratories, with a particular focus on those employed to discover nematocides. This review reveals that at least 50 distinct phenotypic assays with low-, medium- or high-throughput capacity were developed over this period, with more recently developed methods being quantitative, semi-automated and higher throughput. The main features assessed or measured in these assays include worm motility, growth/development, morphological changes, viability/lethality, pharyngeal pumping, egg hatching, larval migration, CO₂- or ATP-production and/or enzyme activity. Recent progress in assay development has led to the routine application of practical, cost-effective, medium- to high-throughput whole-worm screening assays in academic or public-private partnership (PPP) contexts, and major potential for novel high-content, high-throughput platforms in the near future. Complementing this progress are major advances in the molecular data sciences, computational biology and informatics, which are likely to further enable and accelerate anthelmintic drug discovery and development.

Malnutrition, anemia, micronutrient deficiency and parasitic infections among schoolchildren in rural Tanzania

Background

Malnutrition, anemia, micronutrient deficiency and parasitic infections continue to impact the nutritional status and health of children in lower-income countries. However, not enough data concerning this issue is available. The aim of this study was to assess the distribution of nutritional indicators, anemia and micronutrient deficiency and their underlying risk factors among schoolchildren in south-eastern Tanzania.

Methodology/Principal findings

This cross-sectional study enrolled primary schoolchildren aged 6–12 years from Kikwawila and Kiberege wards, Tanzania. In total, 471 schoolchildren underwent a physical examination and provided blood, stool and urine samples for an assessment of the levels of different micronutrients, nutritional and anemia status, and parasitic infection status. We employed bivariate and multivariate logistic regression to determine the association between nutritional statuses, anemia, micronutrient deficiency and parasitic infections. We found that 23.90%, 12.60% and 16.20% of schoolchildren were stunted, underweight and wasted, respectively. About 14.0% of schoolchildren were found to be anemic. Children diagnosed with Plasmodium falciparum infection were more likely to have low levels of ferritin (aOR: 10.40, 95% CI: 2.88-40.53) and elevated levels of serum soluble transferrin receptor (aOR: 3.59, 95% CI: 1.27-11.23), respectively. Vitamin A (34.71%) and vitamin B12 (8.79%) were the most prevalent micronutrients found to be deficient in diagnosed children. Finally, we found that schoolchildren attending the most rural schools were five times more likely to be diagnosed with at least one micronutrient deficiency (aOR: 5.04, 95% CI: 2.38–11.44).

Conclusions/Significance

Malnutrition, anemia and micronutrient deficiency still pose a significant health burden among schoolchildren living in rural Tanzania. To effectively tackle this burden, health interventions such as deworming, micronutrient supplementation, vector control, health education and access to clean water and improved sanitation should be strengthened and made sustainable.

In this study, we assessed the distribution and risk factors of nutritional indicators, anemia and micronutrient deficiency among schoolchildren of the Kikwawila and Kiberege wards, Tanzania. Our analysis revealed that malnutrition in form of stunting and wasting is still very high among schoolchildren in this region. About 14.0% of children were found to be anemic. Micronutrient deficiency was highly variable ranging from 0.50% (Folate) to 35.0% (Vitamin A). Schoolchildren from most rural schools were more likely to be found stunted and deficient with at least one type of micronutrient. Efforts to control and eliminate malnutrition, anemia, micronutrient deficiency and parasitic infections would benefit from sustainable and integrated approaches such as deworming, micronutrient supplementation, health education, vector control and an improvement in access to clean water and improved sanitation.

G-quadruplexes in helminth parasites

Parasitic helminths infecting humans are highly prevalent infecting ∼2 billion people worldwide, causing inflammatory responses, malnutrition and anemia that are the primary cause of morbidity. In addition, helminth infections of cattle have a significant economic impact on livestock production, milk yield and fertility. The etiological agents of helminth infections are mainly Nematodes (roundworms) and Platyhelminths (flatworms). G-quadruplexes (G4) are unusual nucleic acid structures formed by G-rich sequences that can be recognized by specific G4 ligands. Here we used the G4Hunter Web Tool to identify and compare potential G4 sequences (PQS) in the nuclear and mitochondrial genomes of various helminths to identify G4 ligand targets. PQS are nonrandomly distributed in these genomes and often located in the proximity of genes. Unexpectedly, a Nematode, Ascaris lumbricoides, was found to be highly enriched in stable PQS. This species can tolerate high-stability G4 structures, which are not counter selected at all, in stark contrast to most other species. We experimentally confirmed G4 formation for sequences found in four different parasitic helminths. Small molecules able to selectively recognize G4 were found to bind to Schistosoma mansoni G4 motifs. Two of these ligands demonstrated potent activity both against larval and adult stages of this parasite.