Caenorhabditis elegans in anthelmintic research - Old model, new perspectives

Spirocerca lupi draft genome, vaccine and anthelmintic targets

Spirocerca lupi is a parasitic nematode affecting predominantly domestic dogs. It causes spirocercosis, a disease that is often fatal. The assembled draft genome of S. lupi consists of 13,627 predicted protein-coding genes and is approximately 150 Mb in length. Several known anthelmintic gene targets such as for β-Tubulin, glutamate, and GABA receptors as well as known vaccine gene targets such as cysteine protease inhibitor and cytokines were identified in S. lupi by comparing orthologs of C. elegans anthelmintic gene targets as well as orthologs to known vaccine candidates. New anthelmintic targets were predicted through an inclusion-exclusion strategy and new vaccine targets were predicted through an immunoinformatics approach. New anthelminthic targets include DNA-directed RNA polymerases, chitin synthase, polymerases, and other enzymes. New vaccine targets include cuticle collagens. These gene targets provide a starting platform for new drug identification and vaccine design.

Use of Viscous medium to study anthelmintic drug action in Caenorhabditis elegans

Caenorhabditis elegans is an appealing tool for experimental evolution and for working with antiparasitic drugs, from understanding the molecular mechanisms of drug action and resistance to uncover new drug targets. We present a new methodology for studying the impact of antiparasitic drugs in C. elegans. Viscous medium was initially designed for C. elegans maintenance during long-term evolution experiments. Viscous medium provides a less structured environment than the standard nematode growth media agar, yet the bacteria food source remains suspended. Further, the Viscous medium offers the worm population enough support to move freely, mate, and reproduce at a rate comparable to standard agar cultures. Here, the Viscous medium was adapted for use in antiparasitic research. We observed a similar sensitivity of C. elegans to anthelmintic drugs as in standard liquid media and statistical difference to the standard agar media through a larval development assay. Using Viscous medium in C. elegans studies will considerably improve antiparasitic resistance research, and this medium could be used in studies aimed at understanding long-term multigenerational drug activity.

Synthesis and anthelmintic activity of novel thiosemicarbazide and 1,2,4-triazole derivatives: In vitro, in vivo, and in silico study

INTRODUCTION

Intestinal parasitic infections are neglected diseases and, due to the increasing resistance of parasites to available drugs, they pose an increasing therapeutic challenge. Therefore, there is a great need for finding new compounds with antiparasitic activity.

OBJECTIVES

In this work, new thiosemicarbazide and 1,2,4-triazole derivatives were synthesized and tested for their anthelmintic activity.

METHODS

The synthesis was carried out by classical methods of organic chemistry. Anthelmintic activity tests were carried out in vitro (Rhabditis sp., Haemonchus contortus, Strongylidae sp.) in vivo (Heligmosomoides polygyrus/bakeri), and in silico analysis was performed.

RESULTS

Quinoline-6-carboxylic acid derivative compounds were designed and synthesized. The highest activity in the screening tests in the Rhabditis model was demonstrated by compound II-1 with a methoxyphenyl substituent LC50 = 0.3 mg/mL. In the next stage of the research, compound II-1 was analyzed in the H. contortus model. The results showed that compound II-1 was active and had ovicidal (percentage of dead eggs > 45 %) and larvicidal (percentage of dead larvae > 75 %) properties. Studies in the Strongylidae sp. model confirmed the ovicidal activity of compound II-1 (percentage of dead eggs ≥ 55 %). In vivo studies conducted in the H. polygyrus/bakeri nematode model showed that the number of nematodes decreased by an average of 30 % under the influence of compound II-1. In silico studies have shown two possible modes of action of compound II-1, i.e. inhibition of tubulin polymerization and SDH. The test compound did not show any systemic toxic effects. Its influence on drug metabolism related to the activity of cytochrome CYP450 enzymes was also investigated.

CONCLUSION

The results obtained in the in vitro, in vivo, and in silico studies indicate that the test compound can be described as a HIT, which in the future may be used in the treatment of parasitic diseases in humans and animals.

Systematic approaches to machine learning models for predicting pesticide toxicity

Pesticides play an important role in modern agriculture by protecting crops from pests and diseases. However, the negative consequences of pesticides, such as environmental contamination and adverse effects on human and ecological health, underscore the importance of accurate toxicity predictions. To address this issue, artificial intelligence models have emerged as valuable methods for predicting the toxicity of organic compounds. In this review article, we explore the application of machine learning (ML) for pesticide toxicity prediction. This review provides a detailed summary of recent developments, prediction models, and datasets used for pesticide toxicity prediction. In this analysis, we compared the results of several algorithms that predict the harmfulness of various classes of pesticides. Furthermore, this review article identified emerging trends and areas for future direction, showcasing the transformative potential of machine learning in promoting safer pesticide usage and sustainable agriculture.

Alstoboonine, an Ulean-Type Indole Alkaloid from Alstonia boonei Leaves

Alstonia boonei De Wild is a common plant in West Africa used in traditional medicine for various indications. While the stem bark has frequently been investigated, not much is known about the phytochemistry and bioactivity of the leaves. Within the current study, the major alkaloids of a hydroethanolic leaf extract were therefore isolated and characterized by MS, NMR, and ECD. This led to the identification of alstoboonine 1, a new ulean-type alkaloid, along with eight previously reported indole alkaloids, 15-hydroxyangustilobine A (2), 6,7-seco-angustilobine B (3), 6,7-seco-19,20-α-epoxyangustilobine B (4), alstrostine E (5), alstrostine C (6), alstrostine D (7), 12-methoxyechitamidine (8), and 19-oxo-12-methoxyechitamidine (9). 1 was moderately active in vitro against Plasmodium falciparum NF54 (IC50 6.9 μM), but inactive against other protozoan parasites (Trypanosoma brucei, Trypanosoma cruzi, Leishmania donovani). No significant cytotoxic effects were observed in L6 rat skeletal myoblast cells and MCF-7 breast cancer cells. Similarly, compounds 3 to 9 did not show cytotoxicity in MCF-7 cells. Due to the reported traditional use of the plant as an anthelmintic, the major alkaloids 2, 5, 6, and 8 were tested against the nematode Caenorhabditis elegans. Nematicidal effects were observed for 6 (LC50 400 μM), whereas 2, 5, and 8 were inactive.

A phenotypic screen of the Global Health Priority Box identifies an insecticide with anthelmintic activity

BACKGROUND

Infection with parasitic nematodes (helminths), particularly those of the order Strongylida (such as Haemonchus contortus), can cause significant and burdensome diseases in humans and animals. Widespread drug (anthelmintic) resistance in livestock parasites, the absence of vaccines against most of these nematodes, and a lack of new and effective chemical entities on the commercial market demands the discovery of new anthelmintics. In the present study, we searched the Global Health Priority Box (Medicines for Malaria Venture) for new candidates for anthelmintic development.

METHODS

We employed a whole-organism, motility-based phenotypic screening assay to identify compounds from the Global Health Priority Box with activity against larvae of the model parasite H. contortus, and the free-living comparator nematode Caenorhabditis elegans. Hit compounds were further validated via dose-response assays, with lead candidates then assessed for nematocidal activity against H. contortus adult worms, and additionally, for cytotoxic and mitotoxic effects on human hepatoma (HepG2) cells.

RESULTS

The primary screen against H. contortus and C. elegans revealed or reidentified 16 hit compounds; further validation established MMV1794206, otherwise known as 'flufenerim', as a significant inhibitor of H. contortus larval motility (half-maximal inhibitory concentration [IC50] = 18 μM) and development (IC50 = 1.2 μM), H. contortus adult female motility (100% after 12 h of incubation) and C. elegans larval motility (IC50 = 0.22 μM). Further testing on a mammalian cell line (human hepatoma HepG2 cells), however, identified flufenerim to be both cytotoxic (half-maximal cytotoxic concentration [CC50] < 0.7 μM) and mitotoxic (half-maximal mitotoxic concentration [MC50] < 0.7 μM).

CONCLUSIONS

The in vitro efficacy of MMV1794206 against the most pathogenic stages of H. contortus, as well as the free-living C. elegans, suggests the potential for development as a broad-spectrum anthelmintic compound; however, the high toxicity towards mammalian cells presents a significant hindrance. Further work should seek to establish the protein-drug interactions of MMV1794206 in a nematode model, to unravel the mechanism of action, in addition to an advanced structure-activity relationship investigation to optimise anthelmintic activity and eliminate mammalian cell toxicity.

Quantifying the fitness effects of resistance alleles with and without anthelmintic selection pressure using Caenorhabditis elegans

Albendazole and ivermectin are the two most commonly co-administered anthelmintic drugs in mass-drug administration programs worldwide. Despite emerging resistance, we do not fully understand the mechanisms of resistance to these drugs nor the consequences of delivering them in combination. Albendazole resistance has primarily been attributed to variation in the drug target, a beta-tubulin gene. Ivermectin targets glutamate-gated chloride channel (GluCl) genes, but it is unknown whether these genes are involved in ivermectin resistance in nature. Using Caenorhabditis elegans, we defined the fitness costs associated with loss of the drug target genes singly or in combinations of the genes that encode GluCl subunits. We quantified the loss-of function effects on three traits: (i) multi-generational competitive fitness, (ii) fecundity, and (iii) development. In competitive fitness and development assays, we found that a deletion of the beta-tubulin gene ben-1 conferred albendazole resistance, but ivermectin resistance required loss of two GluCl genes (avr-14 and avr-15) or loss of three GluCl genes (avr-14, avr-15, and glc-1). The fecundity assays revealed that loss of ben-1 did not provide any fitness benefit in albendazole and that no GluCl deletion mutants were resistant to ivermectin. Next, we searched for evidence of multi-drug resistance across the three traits. Loss of ben-1 did not confer resistance to ivermectin, nor did loss of any single GluCl subunit or combination confer resistance to albendazole. Finally, we assessed the development of 124 C. elegans wild strains across six benzimidazoles and seven macrocyclic lactones to identify evidence of multi-drug resistance between the two drug classes and found a strong phenotypic correlation within a drug class but not across drug classes. Because each gene affects various aspects of nematode physiology, these results suggest that it is necessary to assess multiple fitness traits to evaluate how each gene contributes to anthelmintic resistance.

Structure activity relationship and target prediction for ABX464 analogues in Caenorhabditis elegans

Global challenges with treatment failures and/or widespread resistance in parasitic worms against commercially available anthelmintics lend impetus to the development of new anthelmintics with novel mechanism(s) of action. The free-living nematode Caenorhabditis elegans is an important model organism used for drug discovery, including the screening and structure-activity investigation of new compounds, and target deconvolution. Previously, we conducted a whole-organism phenotypic screen of the 'Pandemic Response Box' (from Medicines for Malaria Venture, MMV) and identified a hit compound, called ABX464, with activity against C. elegans and a related, parasitic nematode, Haemonchus contortus. Here, we tested a series of 44 synthesized analogues to explore the pharmacophore of activity on C. elegans and revealed five compounds whose potency was similar or greater than that of ABX464, but which were not toxic to human hepatoma (HepG2) cells. Subsequently, we employed thermal proteome profiling (TPP), protein structure prediction and an in silico-docking algorithm to predict ABX464-target candidates. Taken together, the findings from this study contribute significantly to the early-stage drug discovery of a new nematocide based on ABX464. Future work is aimed at validating the ABX464-protein interactions identified here, and at assessing ABX464 and associated analogues against a panel of parasitic nematodes, towards developing a new anthelmintic with a mechanism of action that is distinct from any of the compounds currently-available commercially.

Advancing Strongyloides omics data: bridging the gap with Caenorhabditis elegans

Among nematodes, the free-living model organism Caenorhabditis elegans boasts the most advanced portfolio of high-quality omics data. The resources available for parasitic nematodes, including Strongyloides spp., however, are lagging behind. While C. elegans remains the most tractable nematode and has significantly advanced our understanding of many facets of nematode biology, C. elegans is not suitable as a surrogate system for the study of parasitism and it is important that we improve the omics resources available for parasitic nematode species. Here, we review the omics data available for Strongyloides spp. and compare the available resources to those for C. elegans and other parasitic nematodes. The advancements in C. elegans omics offer a blueprint for improving omics-led research in Strongyloides. We suggest areas of priority for future research that will pave the way for expansions in omics resources and technologies. This article is part of the Theo Murphy meeting issue 'Strongyloides: omics to worm-free populations'.

Model nematodes as a practical innovation to promote high throughput screening of natural products for anthelmintics discovery in South Asia: Current challenges, proposed practical and conceptual solutions

With the increasing prevalence of anthelmintic resistance in animals recorded globally, and the threat of resistance in human helminths, the need for novel anthelmintic drugs is greater than ever. Most research aimed at discovering novel anthelmintic leads relies on high throughput screening (HTS) of large libraries of synthetic small molecules in industrial and academic settings in developed countries, even though it is the tropical countries that are most plagued by helminth infections. Tropical countries, however, have the advantage of possessing a rich flora that may yield natural products (NP) with promising anthelmintic activity. Focusing on South Asia, which produces one of the world's highest research outputs in NP and NP-based anthelmintic discovery, we find that limited basic research and funding, a lack of awareness of the utility of model organisms, poor industry-academia partnerships and lack of technological innovations greatly limit anthelmintics research in the region. Here we propose that utilizing model organisms including the free-living nematode Caenorhabditis elegans, that can potentially allow rapid target identification of novel anthelmintics, and Oscheius tipulae, a closely related, free-living nematode which is found abundantly in soil in hotter temperatures, could be a much-needed innovation that can enable cost-effective and efficient HTS of NPs for discovering compounds with anthelmintic/antiparasitic potential in South Asia and other tropical regions that historically have devoted limited funding for such research. Additionally, increased collaborations at the national, regional and international level between parasitologists and pharmacologists/ethnobotanists, setting up government-industry-academia partnerships to fund academic research, creating a centralized, regional collection of plant extracts or purified NPs as a dereplication strategy and HTS library, and holding regional C. elegans/O. tipulae-based anthelmintics workshops and conferences to share knowledge and resources regarding model organisms may collectively promote and foster a NP-based anthelmintics landscape in South Asia and beyond.

Mapping resistance-associated anthelmintic interactions in the model nematode Caenorhabditis elegans

Parasitic nematodes infect billions of people and are mainly controlled by anthelmintic mass drug administration (MDA). While there are growing efforts to better understand mechanisms of anthelmintic resistance in human and animal populations, it is unclear how resistance mechanisms that alter susceptibility to one drug affect the interactions and efficacy of drugs used in combination. Mutations that alter drug permeability across primary nematode barriers have been identified as potential resistance mechanisms using the model nematode Caenorhabditis elegans. We leveraged high-throughput assays in this model system to measure altered anthelmintic susceptibility in response to genetic perturbations of potential cuticular, amphidial, and alimentary routes of drug entry. Mutations in genes associated with these tissue barriers differentially altered susceptibility to the major anthelmintic classes (macrocyclic lactones, benzimidazoles, and nicotinic acetylcholine receptor agonists) as measured by animal development. We investigated two-way anthelmintic interactions across C. elegans genetic backgrounds that confer resistance or hypersensitivity to one or more drugs. We observe that genetic perturbations that alter susceptibility to a single drug can shift the drug interaction landscape and lead to the appearance of novel synergistic and antagonistic interactions. This work establishes a framework for investigating combinatorial therapies in model nematodes that can potentially be translated to amenable parasite species.

Biochemometry identifies ostruthin as pluripotent antimicrobial and anthelmintic agent from masterwort

The root extract of Peucedanum ostruthium (PO-E) was identified as a promising antibacterial source from a screening of 158 extracts against Staphylococcus aureus. It has also recently been shown to significantly decrease the survival of the nematode Caenorhabditis elegans. We used the biochemometric approach ELINA to investigate the phytochemical characteristics of the multicomponent mixture PO-E to identify the anti-infective constituent(s) targeting S. aureus and C. elegans.1H NMR spectra of PO-E-derived microfractions were correlated with their respective bioactivity data. Heterocovariance analyses unambiguously identified ostruthin as an anti-staphylococcal constituent, which potently also inhibited Enterococcus spp.. ELINA demonstrated that anthelmintic activity was due to a combinatorial effect of ostruthin and isoimperatorin. A C. elegans-based survival and motility assay confirmed that isoimperatorin, imperatorin, and verapamil modulated the susceptibility of ostruthin. The combinatorial effect of these natural products was shown in larvae studies to be related to the function of the nematodes' efflux pump.

Indirect Modulation by FLP-1 Peptides on Chemotaxis and Dispersal Behavior in C. elegans

Parasitic nematodes infect and cause morbidity in over one billion people worldwide, with current anthelmintic drugs decreasing in efficacy. To date, nematodes produce more types of neuropeptides than any other animal. We are interested in the role of neuropeptide signaling systems as a possible target for new anthelmintic drugs. Although FMRFamide-related peptides are found throughout the animal kingdom, the number of these peptides in nematodes greatly exceeds that of any other phylum. We are using Caenorhabditis elegans as a model for examining FMRFamide-like peptides, all of which share a C-terminal Arg-Phe-amide and which are known as FLPs in nematodes. Our previous work indicated interactions between the daf-10 , tax-4 , and flp-1 signaling pathways. In this paper, we further explore these interactions with chemotaxis and dispersal assays.

New Imidazolium Alkaloids with Broad Spectrum of Action from the Marine Bacterium Shewanella aquimarina

The continuous outbreak of drug-resistant bacterial and viral infections imposes the need to search for new drug candidates. Natural products from marine bacteria still inspire the design of pharmaceuticals. Indeed, marine bacteria have unique metabolic flexibility to inhabit each ecological niche, thus expanding their biosynthetic ability to assemble unprecedented molecules. The One-Strain-Many-Compounds approach and tandem mass spectrometry allowed the discovery of a Shewanella aquimarina strain as a source of novel imidazolium alkaloids via molecular networking. The alkaloid mixture was shown to exert bioactivities such as: (a) antibacterial activity against antibiotic-resistant Staphylococcus aureus clinical isolates at 100 µg/mL, (b) synergistic effects with tigecycline and linezolid, (c) restoration of MRSA sensitivity to fosfomycin, and (d) interference with the biofilm formation of S. aureus 6538 and MRSA. Moreover, the mixture showed antiviral activity against viruses with and without envelopes. Indeed, it inhibited the entry of coronavirus HcoV-229E and herpes simplex viruses into human cells and inactivated poliovirus PV-1 in post-infection assay at 200 µg/mL. Finally, at the same concentration, the fraction showed anthelminthic activity against Caenorhabditis elegans, causing 99% mortality after 48 h. The broad-spectrum activities of these compounds are partially due to their biosurfactant behavior and make them promising candidates for breaking down drug-resistant infectious diseases.

Praziquantel inhibits Caenorhabditis elegans development and species-wide differences might be cct-8-dependent

Anthelmintic drugs are used to treat parasitic roundworm and flatworm infections in humans and other animals. Caenorhabditis elegans is an established model to investigate anthelmintics used to treat roundworms. In this study, we use C. elegans to examine the mode of action and the mechanisms of resistance against the flatworm anthelmintic drug praziquantel (PZQ), used to treat trematode and cestode infections. We found that PZQ inhibited development and that this developmental delay varies by genetic background. Interestingly, both enantiomers of PZQ are equally effective against C. elegans, but the right-handed PZQ (R-PZQ) is most effective against schistosome infections. We conducted a genome-wide association mapping with 74 wild C. elegans strains to identify a region on chromosome IV that is correlated with differential PZQ susceptibility. Five candidate genes in this region: cct-8, znf-782, Y104H12D.4, Y104H12D.2, and cox-18, might underlie this variation. The gene cct-8, a subunit of the protein folding complex TRiC, has variation that causes a putative protein coding change (G226V), which is correlated with reduced developmental delay. Gene expression analysis suggests that this variant correlates with slightly increased expression of both cct-8 and hsp-70. Acute exposure to PZQ caused increased expression of hsp-70, indicating that altered TRiC function might be involved in PZQ responses. To test if this variant affects development upon exposure to PZQ, we used CRISPR-Cas9 genome editing to introduce the V226 allele into the N2 genetic background (G226) and the G226 allele into the JU775 genetic background (V226). These experiments revealed that this variant was not sufficient to explain the effects of PZQ on development. Nevertheless, this study shows that C. elegans can be used to study PZQ mode of action and resistance mechanisms. Additionally, we show that the TRiC complex requires further evaluation for PZQ responses in C. elegans.

Nematicidal Activity of Cyclotides: Toxicity Against Caenorhabditis elegans

Cyclotides are a unique family of stable and cyclic mini-proteins found in plants that have nematicidal and anthelmintic activities. They are distributed across the Rubiaceae, Violaceae, Fabaceae, Cucurbitaceae, and Solanaceae plant families, where they are posited to act as protective agents against pests. In this study, we tested the nematicidal properties of extracts from four major cyclotide-producing plants, Oldenlandia affinis, Clitoria ternatea, Viola odorata, and Hybanthus enneaspermus, against the free-living model nematode Caenorhabditis elegans. We evaluated the nematicidal activity of the cyclotides kalata B1, cycloviolacin O2, and hyen D present in these extracts and found them to be active against the larvae of C. elegans. Both the plant extracts and isolated cyclotides exerted dose-dependent toxicity on the first-stage larvae of C. elegans. Isolated cyclotides caused death or damage upon interacting with the worms' mouth, pharynx, and midgut or membrane. Cycloviolacin O2 and hyen D produced bubble-like structures around the C. elegans membrane, termed blebs, implicating membrane disruption causing toxicity and death. All tested cyclotides lost their toxicity when the hydrophobic patches present on them were disrupted via a single-point mutation. The present results provide a facile assay design to measure and explore the nematicidal activities of plant extracts and purified cyclotides on C. elegans.

Isolation, Identification and Molecular Mechanism Analysis of the Nematicidal Compound Spectinabilin from Newly Isolated Streptomyces sp. DT10

Plant parasitic nematodes (PPNs) are highly destructive and difficult to control, while conventional chemical nematicides are highly toxic and cause serious environmental pollution. Additionally, resistance to existing pesticides is becoming increasingly common. Biological control is the most promising method for the controlling of PPNs. Therefore, the screening of nematicidal microbial resources and the identification of natural products are of great significance and urgency for the environmentally friendly control of PPNs. In this study, the DT10 strain was isolated from wild moss samples and identified as Streptomyces sp. by morphological and molecular analysis. Using Caenorhabditis elegans as a model, the extract of DT10 was screened for nematicidal activity, which elicited 100% lethality. The active compound was isolated from the extracts of strain DT10 using silica gel column chromatography and semipreparative high-performance liquid chromatography (HPLC). The compound was identified as spectinabilin (chemical formula C₂₈H₃₁O₆N) using liquid chromatography mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR). Spectinabilin exhibited a good nematicidal activity on C. elegans L1 worms, with a half-maximal inhibitory concentration (IC₅₀) of 2.948 μg/mL at 24 h. The locomotive ability of C. elegans L4 worms was significantly reduced when treated with 40 μg/mL spectinabilin. Further analysis of spectinabilin against known nematicidal drug target genes in C. elegans showed that it acts via target(s) different from those of some currently used nematicidal drugs such as avermectin and phosphine thiazole. This is the first report on the nematicidal activity of spectinabilin on C. elegans and the southern root-knot nematode Meloidogyne incognita. These findings may pave the way for further research and application of spectinabilin as a potential biological nematicide.

Multivariate chemogenomic screening prioritizes new macrofilaricidal leads

Development of direct acting macrofilaricides for the treatment of human filariases is hampered by limitations in screening throughput imposed by the parasite life cycle. In vitro adult screens typically assess single phenotypes without prior enrichment for chemicals with antifilarial potential. We developed a multivariate screen that identified dozens of compounds with submicromolar macrofilaricidal activity, achieving a hit rate of >50% by leveraging abundantly accessible microfilariae. Adult assays were multiplexed to thoroughly characterize compound activity across relevant parasite fitness traits, including neuromuscular control, fecundity, metabolism, and viability. Seventeen compounds from a diverse chemogenomic library elicited strong effects on at least one adult trait, with differential potency against microfilariae and adults. Our screen identified five compounds with high potency against adults but low potency or slow-acting microfilaricidal effects, at least one of which acts through a novel mechanism. We show that the use of microfilariae in a primary screen outperforms model nematode developmental assays and virtual screening of protein structures inferred with deep learning. These data provide new leads for drug development, and the high-content and multiplex assays set a new foundation for antifilarial discovery.

Prenylated Benzophenones from Vismia Guianensis Reduced Nematode Growth and Chemotaxis

Biopesticides are generally considered a safer and more environmentally friendly alternative to conventional pesticides. Plant metabolites display a range of pest specific activity ranging from antimicrobial to larvicidal and nematocidal. We herein describe the evaluation of a Guyanese collection of Vismia guianensis (Clusiaceae) for anthelmintic activity. The bioassay-guided evaluation of the hexane extract yielded the new prenylated benzophenone 8,9-epoxyvismiaphenone F (1). The final structures were elucidated based on spectral analysis and comparison to the known metabolite. To evaluate the anthelmintic efficacy of these compounds, Caenorhabditis elegans were exposed to the compounds via a ring assay model. Post-exposure, the numbers of live C. elegans in the compound (middle), bacteria ring were recorded for 3 d, as well as the total number of live worms for each plate. Compound 1 reduced C. elegans' overall growth and reproduction, suggesting that these prenylated benzophenones may hold some promise as natural pesticides.

Transcriptomics of ivermectin response in Caenorhabditis elegans: Integrating abamectin quantitative trait loci and comparison to the Ivermectin-exposed DA1316 strain

Parasitic nematodes pose a significant threat to human and animal health, as well as cause economic losses in the agricultural sector. The use of anthelmintic drugs, such as Ivermectin (IVM), to control these parasites has led to widespread drug resistance. Identifying genetic markers of resistance in parasitic nematodes can be challenging, but the free-living nematode Caenorhabditis elegans provides a suitable model. In this study, we aimed to analyze the transcriptomes of adult C. elegans worms of the N2 strain exposed to the anthelmintic drug Ivermectin (IVM), and compare them to those of the resistant strain DA1316 and the recently identified Abamectin Quantitative Trait Loci (QTL) on chromosome V. We exposed pools of 300 adult N2 worms to IVM (10-7 and 10-8 M) for 4 hours at 20°C, extracted total RNA and sequenced it on the Illumina NovaSeq6000 platform. Differentially expressed genes (DEGs) were determined using an in-house pipeline. The DEGs were compared to genes from a previous microarray study on IVM-resistant C. elegans and Abamectin-QTL. Our results revealed 615 DEGs (183 up-regulated and 432 down-regulated genes) from diverse gene families in the N2 C. elegans strain. Of these DEGs, 31 overlapped with genes from IVM-exposed adult worms of the DA1316 strain. We identified 19 genes, including the folate transporter (folt-2) and the transmembrane transporter (T22F3.11), which exhibited an opposite expression in N2 and the DA1316 strain and were deemed potential candidates. Additionally, we compiled a list of potential candidates for further research including T-type calcium channel (cca-1), potassium chloride cotransporter (kcc-2), as well as other genes such as glutamate-gated channel (glc-1) that mapped to the Abamectin-QTL.

Fractionation Coupled to Molecular Networking: Towards Identification of Anthelmintic Molecules in Terminalia leiocarpa (DC.) Baill

Terminalia leiocarpa is a medicinal plant widely used in ethnoveterinary medicine to treat digestive parasitosis whose extracts were shown to be active against gastrointestinal nematodes of domestic ruminants. The objective of our study was to identify compounds responsible for this activity. Column fractionation was performed, and the activity of the fractions was assessed in vitro on Haemonchus contortus and Caenorhabditis elegans as well as their cytotoxicity on WI38 fibroblasts. Two fractions were the most active on both nematode models and less cytotoxic. LC-MS/MS analysis and manual dereplication coupled to molecular networking allowed identification of the main compounds: ellagic acid and derivatives, gallic acid, astragalin, rutin, quinic acid, and fructose. Other potentially identified compounds such as shikimic acid, 2,3-(S)-hexahydroxydiphenoyl-D-glucose or an isomer, quercetin-3-O-(6-O-galloyl)-β-D-galactopyranoside or an isomer, and a trihydroxylated triterpenoid bearing a sugar as rosamultin are reported in this plant for the first time. Evaluation of the anthelmintic activity of the available major compounds showed that ellagic and gallic acids were the most effective in inhibiting the viability of C. elegans. Their quantification in fractions 8 and 9 indicated the presence of about 8.6 and 7.1 µg/mg ellagic acid and about 9.6 and 2.0 µg/mg gallic acid respectively. These concentrations are not sufficient to justify the activity observed. Ellagic acid derivatives and other compounds that were found to be positively correlated with the anthelmintic activity of the fractions may have additive or synergistic effects when combined, but other unidentified compounds could also be implicated in the observed activity.

Benzimidazoles cause lethality by inhibiting the function of Caenorhabditis elegans neuronal beta-tubulin

Parasitic nematode infections cause an enormous global burden to both humans and livestock. Resistance to the limited arsenal of anthelmintic drugs used to combat these infections is widespread, including benzimidazole (BZ) compounds. Previous studies using the free-living nematode Caenorhabditis elegans to model parasitic nematode resistance have shown that loss-of-function mutations in the beta-tubulin gene ben-1 confer resistance to BZ drugs. However, the mechanism of resistance and the tissue-specific susceptibility are not well known in any nematode species. To identify in which tissue(s) ben-1 function underlies BZ susceptibility, transgenic strains that express ben-1 in different tissues, including hypodermis, muscles, neurons, intestine, and ubiquitous expression were generated. High-throughput fitness assays were performed to measure and compare the quantitative responses to BZ compounds among different transgenic lines. Significant BZ susceptibility was observed in animals expressing ben-1 in neurons, comparable to expression using the ben-1 promoter. This result suggests that ben-1 function in neurons underlies susceptibility to BZ. Subsetting neuronal expression of ben-1 based on the neurotransmitter system further restricted ben-1 function in cholinergic neurons to cause BZ susceptibility. These results better inform our current understanding of the cellular mode of action of BZs and also suggest additional treatments that might potentiate the effects of BZs in neurons.

Caenorhabditis elegans as a valuable model for the study of anthelmintic pharmacodynamics and drug-drug interactions: The case of ivermectin and eprinomectin

Caenorhabditis elegans is a free-living nematode that has been validated for anthelmintic drug screening. However, this model has not been used to address anthelmintic dose-response-time and drug-drug interactions through matrix array methodology. Eprinomectin (EPM) and Ivermectin (IVM) are macrocyclic lactones widely used as anthelmintics. Despite being very similar, EPM and IVM are combined in commercial formulations or mixed by farmers, under the assumption that the combination would increase their efficacy. However, there is no data reported on the pharmacological evaluation of the combination of both drugs. In this study, we assessed the pharmacodynamics and drug-drug interactions of these two anthelmintic drugs. Since the action of these drugs causes worm paralysis, we used an infrared motility assay to measure EPM and IVM effects on worm movement over time. The results showed that EPM was slightly more potent than IVM, that drug potency increased with drug time exposure, and that once paralyzed, worms did not recover. Different EPM/IVM concentration ratios were used and synergy and combination sensitivity scores were determined at different exposure times, applying Highest Single Agent (HSA), Loewe additivity, Bliss and Zero Interaction Potency (ZIP) models. The results clearly indicate that there is neither synergy nor antagonism between both macrocyclic lactones. This study shows that it is more relevant to prioritize the exposure time of each individual drug than to combine them to improve their effects. The results highlight the utility of C. elegans to address pharmacodynamics studies, particularly for drug-drug interactions. Models in vitro can be integrated to facilitate preclinical and clinical translational studies and help researchers to understand drug-drug interactions and achieve rational therapeutic regimes.

Genomic landscape of drug response reveals mediators of anthelmintic resistance

Like other pathogens, parasitic helminths can rapidly evolve resistance to drug treatment. Understanding the genetic basis of anthelmintic drug resistance in parasitic nematodes is key to tracking its spread and improving the efficacy and sustainability of parasite control. Here, we use an in vivo genetic cross between drug-susceptible and multi-drug-resistant strains of Haemonchus contortus in a natural host-parasite system to simultaneously map resistance loci for the three major classes of anthelmintics. This approach identifies new alleles for resistance to benzimidazoles and levamisole and implicates the transcription factor cky-1 in ivermectin resistance. This gene is within a locus under selection in ivermectin-resistant populations worldwide; expression analyses and functional validation using knockdown experiments support that cky-1 is associated with ivermectin survival. Our work demonstrates the feasibility of high-resolution forward genetics in a parasitic nematode and identifies variants for the development of molecular diagnostics to combat drug resistance in the field.

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.

Interactions of C. elegans β-tubulins with the microtubule inhibitor and anthelmintic drug albendazole

Parasitic nematodes are major human and agricultural pests, and benzimidazoles are amongst the most important broad spectrum anthelmintic drug class used for their control. Benzimidazole resistance is now widespread in many species of parasitic nematodes in livestock globally and an emerging concern for the sustainable control of human soil transmitted helminths. β-tubulin is the major benzimidazole target, although other genes may influence resistance. Among the six C. elegans β-tubulin genes, loss of ben-1 causes resistance without other apparent defects. Here, we explored the genetics of C. elegans β-tubulin genes in relation to the response to the benzimidazole derivative albendazole. The most highly expressed β-tubulin isotypes, encoded by tbb-1 and tbb-2, were known to be redundant with each other for viability, and their products are predicted not to bind benzimidazoles. We found that tbb-2 mutants, and to a lesser extent tbb-1 mutants, were hypersensitive to albendazole. The double mutant tbb-2 ben-1 is uncoordinated and short, resembling the wild type exposed to albendazole, but the tbb-1 ben-1 double mutant did not show the same phenotypes. These results suggest that tbb-2 is a modifier of ABZ sensitivity. To better understand how BEN-1 mutates to cause benzimidazole resistance, we isolated mutants resistant to albendazole and found that 15 of 16 mutations occurred in the ben-1 coding region. Mutations ranged from likely nulls to hypomorphs, and several corresponded to residues that cause resistance in other organisms. Null alleles of ben-1 are albendazole-resistant and BEN-1 shows high sequence identity with tubulins from other organisms, suggesting that many amino acid changes could cause resistance. However, our results suggest that missense mutations conferring resistance are not evenly distributed across all possible conserved sites. Independent of their roles in benzimidazole resistance, tbb-1 and tbb-2 may have specialized functions as null mutants of tbb-1 or tbb-2 were cold or heat sensitive, respectively.

Meta-Analysis of Caenorhabditis elegans Transcriptomics Implicates Hedgehog-Like Signaling in Host-Microbe Interactions

Controlling nematode-caused diseases that affect cattle and crops world-wide remains a critical economic issue, owing to the lack of effective sustainable interventions. The interdependence of roundworms and their environmental microbes, including their microbiota, offers an opportunity for developing more targeted anthelminthic strategies. However, paucity of information and a currently narrow understanding of nematode-microbe interactions limited to specific infection contexts has precluded us from exploiting it. With the advent of omics approaches to map host-microbe genetic interactions, particularly in the model roundworm Caenorhabditis elegans, large datasets are now available across multiple models, that enable identification of nematode-microbe-specific pathways. In this work we collected 20 transcriptomic datasets documenting gene expression changes of C. elegans exposed to 20 different commensal and pathogenic microbes, performing gene enrichment analyses followed by functional testing using RNA interference directed toward genes of interest, before contrasting results from transcriptomic meta-analyses and phenomics. Differential expression analyses revealed a broad enrichment in signaling, innate immune response and (lipid) metabolism genes. Amongst signaling gene families, the nematode-divergent and expanded Hedgehog-like signaling (HHLS) pathway featured prominently. Indeed, 24/60 C. elegans Hedgehog-like proteins (HRPs) and 15/27 Patched-related receptors (PTRs) were differentially expressed in at least four microbial contexts, while up to 32/60 HRPs could be differentially expressed in a single context. interestingly, differentially expressed genes followed a microbe-specific pattern, suggestive of an adaptive microbe-specific response. To investigate this further, we knocked-down 96 individual HHLS genes by RNAi, using high-throughput assays to assess their impact on three worm-gut infection models (Pseudomonas aeruginosa, Staphylococcus aureus, and Enterococcus faecalis) and two worm-commensal paradigms (Comamonas sp., and Bacillus subtilis). We notably identified new putative infection response genes whose upregulation was required for normal pathogen resistance (i.e., grl-21 and ptr-18 protective against E. faecalis), as well as commensal-specific host-gene expression changes that are required for normal host stress handling. Importantly, interactions appeared more microbe-specific than shared. Our results thus implicate the Hedgehog-like signaling pathway in the modulation and possibly fine-tuning of nematode-microbe interactions and support the idea that interventions targeting this pathway may provide a new avenue for anthelmintic development.

Ivermectin-induced gene expression changes in adult Parascaris univalens and Caenorhabditis elegans: a comparative approach to study anthelminthic metabolism and resistance in vitro

Background

The nematode Parascaris univalens is one of the most prevalent parasitic pathogens infecting horses but anthelmintic resistance undermines treatment approaches. The molecular mechanisms underlying drug activity and resistance remain poorly understood in this parasite since experimental in vitro models are lacking. The aim of this study was to evaluate the use of Caenorhabditis elegans as a model for P. univalens drug metabolism/resistance studies by a comparative gene expression approach after in vitro exposure to the anthelmintic drug ivermectin (IVM).

Methods

Twelve adult P. univalens worms in groups of three were exposed to ivermectin (IVM, 10^–13 M, 10^–11 M, 10^–9 M) or left unexposed for 24 h at 37 °C, and total RNA, extracted from the anterior end of the worms, was sequenced using Illumina NovaSeq. Differentially expressed genes (DEGs) involved in metabolism, transportation, or gene expression with annotated Caernorhabditis elegans orthologues were identified as candidate genes to be involved in IVM metabolism/resistance. Similarly, groups of 300 adult C. elegans worms were exposed to IVM (10^–9 M, 10^–8 M and 10^–7 M) or left unexposed for 4 h at 20 °C. Quantitative RT-PCR of RNA extracted from the C. elegans worm pools was used to compare against the expression of selected P. univalens candidate genes after drug treatment.

Results

After IVM exposure, 1085 DEGs were found in adult P. univalens worms but the relative gene expression changes were small and large variabilities were found between different worms. Fifteen of the DEGs were chosen for further characterization in C. elegans after comparative bioinformatics analyses. Candidate genes, including the putative drug target lgc-37, responded to IVM in P. univalens, but marginal to no responses were observed in C. elegans despite dose-dependent behavioral effects observed in C. elegans after IVM exposure. Thus, the overlap in IVM-induced gene expression in this small set of genes was minor in adult worms of the two nematode species.

Conclusion

This is the first time to our knowledge that a comparative gene expression approach has evaluated C. elegans as a model to understand IVM metabolism/resistance in P. univalens. Genes in P. univalens adults that responded to IVM treatment were identified. However, identifying conserved genes in P. univalens and C. elegans involved in IVM metabolism/resistance by comparing gene expression of candidate genes proved challenging. The approach appears promising but was limited by the number of genes studied (n = 15). Future studies comparing a larger number of genes between the two species may result in identification of additional candidate genes involved in drug metabolism and/or resistance.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05260-4.

Appraisal of Cinnamaldehyde Analogs as Dual-Acting Antibiofilm and Anthelmintic Agents

Cinnamaldehyde has a broad range of biological activities, which include antibiofilm and anthelmintic activities. The ever-growing problem of drug resistance and limited treatment options have created an urgent demand for natural molecules with antibiofilm and anthelmintic properties. Hence, we hypothesized that molecules with a scaffold structurally similar to that of cinnamaldehyde might act as dual inhibitors against fungal biofilms and helminths. In this regard, eleven cinnamaldehyde analogs were tested to determine their effects on fungal Candida albicans biofilm and nematode Caenorhabditis elegans. α-Methyl and trans-4-methyl cinnamaldehydes efficiently inhibited C. albicans biofilm formation (>90% inhibition at 50 μg/mL) with minimum inhibitory concentrations (MICs) of ≥ 200 μg/mL and 4-bromo and 4-chloro cinnamaldehydes exhibited anthelmintic property at 20 μg/mL against C. elegans. α-Methyl and trans-4-methyl cinnamaldehydes inhibited hyphal growth and cell aggregation. Scanning electron microscopy was employed to determine the surface architecture of C. albicans biofilm and cuticle of C. elegans, and confocal laser scanning microscopy was used to determine biofilm characteristics. The perturbation in gene expression of C. albicans was investigated using qRT-PCR analysis and α-methyl and trans-4-methyl cinnamaldehydes exhibited down-regulation of ECE1, IFD6, RBT5, UCF1, and UME6 and up-regulation of CHT4 and YWP1. Additionally, molecular interaction of these two molecules with UCF1 and YWP1 were revealed by molecular docking simulation. Our observations collectively suggest α-methyl and trans-4-methyl cinnamaldehydes are potent biofilm inhibitors and that 4-bromo and 4-chloro cinnamaldehydes are anthelmintic agents. Efforts are required to determine the range of potential therapeutic applications of cinnamaldehyde analogs.

The role of alternative toxicological trials in drug discovery programs: The case of Caenorhabditis elegans and other methods

The discovery of a new drug requires over a billion dollars and around 12 years of research efforts, and toxicity is the leading reason for failure to approve candidate drugs. Many alternative methods have been validated to detect toxicity as early as possible to diminish the waste of resources and efforts in medicinal chemistry research, and in vivo alternative methods are especially valuable for the amount of information they can give at little cost and in a short time. In this work, we present a review of the literature published between the years 2000 and 2021 of in vivo alternative methods of toxicity screening employed in medicinal chemistry, which we believe will be useful because, in addition to shortening research times, these studies provide much additional information aside from the toxicity of drug candidate compounds. These in vivo models include zebrafish, Artemia salina, Galleria mellonella, Drosophila melanogaster, planarians, and Caenorhabditis elegans as highlights. The most published ones in the last decade were zebrafish, D. melanogaster and C. elegans due to their reliability, ease and cost-effectiveness of implementation and flexibility. Special attention is given to C. elegans because of its rising popularity, a wide range of uses including toxicity screening, and active effects measurement, from antioxidant effects to anthelmintic and antimicrobial activities, and its fast and reliable results. Over time, C. elegans also became a viable high-throughput (HTS) automated drug screening option. Additionally, this manuscript lists briefly the other screening methods used for the initial toxicological analyses and the role of alternative in vivo methods in these scenarios, classifying them as in silico, in vitro and alternative in vivo models, the latter of which have been receiving a growing increase in interest in recent years.

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.

A High-Throughput Phenotypic Screen of the 'Pandemic Response Box' Identifies a Quinoline Derivative with Significant Anthelmintic Activity

Parasitic nematodes cause diseases in livestock animals and major economic losses to the agricultural industry worldwide. Nematodes of the order Strongylida, including Haemonchus contortus, are particularly important. The excessive use of anthelmintic compounds to treat infections and disease has led to widespread resistance to these compounds in nematodes, such that there is a need for new anthelmintics with distinctive mechanisms of action. With a focus on discovering new anthelmintic entities, we screened 400 chemically diverse compounds within the 'Pandemic Response Box' (from Medicines for Malaria Venture, MMV) for activity against H. contortus and its free-living relative, Caenorhabditis elegans-a model organism. Using established phenotypic assays, test compounds were evaluated in vitro for their ability to inhibit the motility and/or development of H. contortus and C. elegans. Dose-response evaluations identified a compound, MMV1581032, that significantly the motility of H. contortus larvae (IC₅₀ = 3.4 ± 1.1 μM) and young adults of C. elegans (IC₅₀ = 7.1 ± 4.6 μM), and the development of H. contortus larvae (IC₅₀ = 2.2 ± 0.7 μM). The favourable characteristics of MMV1581032, such as suitable physicochemical properties and an efficient, cost-effective pathway to analogue synthesis, indicates a promising candidate for further evaluation as a nematocide. Future work will focus on a structure-activity relationship investigation of this chemical scaffold, a toxicity assessment of potent analogues and a mechanism/mode of action investigation.

Practical High-Throughput Method to Screen Compounds for Anthelmintic Activity against Caenorhabditis elegans

In the present study, we established a practical and cost-effective high throughput screening assay, which relies on the measurement of the motility of Caenorhabditis elegans by infrared light-interference. Using this assay, we screened 14,400 small molecules from the "HitFinder" library (Maybridge), achieving a hit rate of 0.3%. We identified small molecules that reproducibly inhibited the motility of C. elegans (young adults) and assessed dose relationships for a subset of compounds. Future work will critically evaluate the potential of some of these hits as candidates for subsequent optimisation or repurposing as nematocides or nematostats. This high throughput screening assay has the advantage over many previous assays in that it is cost- and time-effective to carry out and achieves a markedly higher throughput (~10,000 compounds per week); therefore, it is suited to the screening of libraries of tens to hundreds of thousands of compounds for subsequent evaluation and development. The present phenotypic whole-worm assay should be readily adaptable to a range of socioeconomically important parasitic nematodes of humans and animals, depending on their dimensions and motility characteristics in vitro, for the discovery of new anthelmintic candidates. This focus is particularly important, given the widespread problems associated with drug resistance in many parasitic worms of livestock animals globally.

Behavioral fingerprints predict insecticide and anthelmintic mode of action

Novel invertebrate-killing compounds are required in agriculture and medicine to overcome resistance to existing treatments. Because insecticides and anthelmintics are discovered in phenotypic screens, a crucial step in the discovery process is determining the mode of action of hits. Visible whole-organism symptoms are combined with molecular and physiological data to determine mode of action. However, manual symptomology is laborious and requires symptoms that are strong enough to see by eye. Here, we use high-throughput imaging and quantitative phenotyping to measure Caenorhabditis elegans behavioral responses to compounds and train a classifier that predicts mode of action with an accuracy of 88% for a set of ten common modes of action. We also classify compounds within each mode of action to discover substructure that is not captured in broad mode-of-action labels. High-throughput imaging and automated phenotyping could therefore accelerate mode-of-action discovery in invertebrate-targeting compound development and help to refine mode-of-action categories.

A survey of the kinome pharmacopeia reveals multiple scaffolds and targets for the development of novel anthelmintics

Over one billion people are currently infected with a parasitic nematode. Symptoms can include anemia, malnutrition, developmental delay, and in severe cases, death. Resistance is emerging to the anthelmintics currently used to treat nematode infection, prompting the need to develop new anthelmintics. Towards this end, we identified a set of kinases that may be targeted in a nematode-selective manner. We first screened 2040 inhibitors of vertebrate kinases for those that impair the model nematode Caenorhabditis elegans. By determining whether the terminal phenotype induced by each kinase inhibitor matched that of the predicted target mutant in C. elegans, we identified 17 druggable nematode kinase targets. Of these, we found that nematode EGFR, MEK1, and PLK1 kinases have diverged from vertebrates within their drug-binding pocket. For each of these targets, we identified small molecule scaffolds that may be further modified to develop nematode-selective inhibitors. Nematode EGFR, MEK1, and PLK1 therefore represent key targets for the development of new anthelmintic medicines.