Abstract:Nematode parasites have a profound impact on humankind, infecting nearly one-quarter of the world’s population, as well as livestock. There is a pressing need for discovering nematicides due to the spread of resistance to currently used drugs. The free-living nematode Caenorhabditis elegans is a formidable experimentally tractable model organism that offers key advantages in accelerating nematicide discovery. We report the screening of drug-like libraries using an overnight high-throughput C. elegans assay, ba… Show more
“…However, this approach, which relies on the digital segmentation of objects from the ‘background’ [ 22 ], can sometimes be challenging to apply to parasitic worms, depending on their movement characteristics and tendency to clump. Measuring motility via electrical impedance [ 27 ] or with infrared light beam-interference [ 28 , 29 ] shows considerable promise for developing medium to high throughput techniques.…”
Parasitic worms cause very significant diseases in animals and humans worldwide, and their control is critical to enhance health, well-being and productivity. Due to widespread drug resistance in many parasitic worms of animals globally, there is a major, continuing demand for the discovery and development of anthelmintic drugs for use to control these worms. Here, we established a practical, cost-effective and semi-automated high throughput screening (HTS) assay, which relies on the measurement of motility of larvae of the barber’s pole worm (Haemonchus contortus) using infrared light-interference. Using this assay, we screened 80,500 small molecules and achieved a hit rate of 0.05%. We identified three small molecules that reproducibly inhibited larval motility and/or development (IC50 values of ~4 to 41 µM). Future work will critically assess the potential of selected hits as candidates for subsequent optimisation or repurposing against parasitic nematodes. This HTS assay has a major advantage over most previous assays in that it achieves a ≥ 10-times higher throughput (i.e., 10,000 compounds per week), and is thus suited to the screening of libraries of tens of thousands to hundreds of thousands of compounds for subsequent hit-to-lead optimisation or effective repurposing and development. The current assay should be adaptable to many socioeconomically important parasitic nematodes, including those that cause neglected tropical diseases (NTDs). This aspect is of relevance, given the goals of the World Health Organization (WHO) Roadmap for NTDs 2021–2030, to develop more effective drugs and drug combinations to improve patient outcomes and circumvent the ineffectiveness of some current anthelmintic drugs and possible drug resistance.
“…However, this approach, which relies on the digital segmentation of objects from the ‘background’ [ 22 ], can sometimes be challenging to apply to parasitic worms, depending on their movement characteristics and tendency to clump. Measuring motility via electrical impedance [ 27 ] or with infrared light beam-interference [ 28 , 29 ] shows considerable promise for developing medium to high throughput techniques.…”
Parasitic worms cause very significant diseases in animals and humans worldwide, and their control is critical to enhance health, well-being and productivity. Due to widespread drug resistance in many parasitic worms of animals globally, there is a major, continuing demand for the discovery and development of anthelmintic drugs for use to control these worms. Here, we established a practical, cost-effective and semi-automated high throughput screening (HTS) assay, which relies on the measurement of motility of larvae of the barber’s pole worm (Haemonchus contortus) using infrared light-interference. Using this assay, we screened 80,500 small molecules and achieved a hit rate of 0.05%. We identified three small molecules that reproducibly inhibited larval motility and/or development (IC50 values of ~4 to 41 µM). Future work will critically assess the potential of selected hits as candidates for subsequent optimisation or repurposing against parasitic nematodes. This HTS assay has a major advantage over most previous assays in that it achieves a ≥ 10-times higher throughput (i.e., 10,000 compounds per week), and is thus suited to the screening of libraries of tens of thousands to hundreds of thousands of compounds for subsequent hit-to-lead optimisation or effective repurposing and development. The current assay should be adaptable to many socioeconomically important parasitic nematodes, including those that cause neglected tropical diseases (NTDs). This aspect is of relevance, given the goals of the World Health Organization (WHO) Roadmap for NTDs 2021–2030, to develop more effective drugs and drug combinations to improve patient outcomes and circumvent the ineffectiveness of some current anthelmintic drugs and possible drug resistance.
“…Linoleic acid (>99%) was purchased from Sigma, USA (L2376), and studied for its nematicidal and cytotoxic activities. Dose-response curves yielded an IC 50 of 0.4 µM (95% confidence interval, 0.30 to 0.52) or approximately 0.2 µg/mL (Figure 4), which compares favorably with that of the established anthelmintic levamisole (6.4 ± 0.3 µM) [22].…”
Section: Nematicidal Activity Of Linoleic Acidmentioning
Holigarna caustica (Dennst.) Oken is used by the tribes of Northeast India for the treatment of intestinal problems. Therefore, the present study was undertaken to investigate the active principles of this plant responsible for its anthelmintic activity, using bioassay-guided fractionation. An ethanol extract of H. caustica fruit was fractionated on a silica gel column, followed by HPLC, while nematicidal activity was followed throughout on Caenorhabditis (C.) elegans as a model organism. Our study constitutes the first nematicidal report for this plant. Bioassay-guided purification led to the isolation of one compound (IC50 = 0.4 µM) as the only active constituent in the most active fraction. The compound was identified as linoleic acid based on spectroscopic data (1H and 13C NMR and ESI-MS). No cytotoxicity was observed in the crude extract or in linoleic acid (up to 356 µM). The results support the use of H. caustica for the treatment of intestinal problems by traditional healers in India.
“…The Pathogen Box project is currently active, but several groups have already reported anthelmintic screens using this library [129,135,[161][162][163][164][165]. We have compiled the results from these published screens in Figure 5.…”
Section: Open Approaches To Developing Therapeuticsmentioning
confidence: 99%
“…For example MMV690102, which was originally developed as an Assay outline and citations for data sources: C. elegans growth/motility screen -automated quantification using the INVAPP system [135]. C. elegans motility screen -automated quantification using the WMicrotracker ONE system [163]. C. elegans viability screen -automated quantification of viability by differential absorption of the dyes DB-1 and propidium iodide [164].…”
Section: Open Approaches To Developing Therapeuticsmentioning
confidence: 99%
“…Perhaps the most promising lead from the Pathogen Box so far is tolfenpyrad, a pyrazole-5-carboxamide insecticide, which was first identified as an anthelmintic with activity against exsheathed L3 and L4 parasitic life stages of Haemonchus contortus, a major parasite of ruminants [129]. Subsequent studies have demonstrated activity against the model nematode C. elegans [135,163]. Tolfenpyrad (19) was found to be highly potent, with an IC 50 value between 0.02 and 3 µM in various H. contortus assays and 0.2 µM in a C. elegans assay [129,135].…”
Section: Open Approaches To Developing Therapeuticsmentioning
Helminths, including cestodes, nematodes and trematodes, are a huge global health burden, infecting hundreds of millions of people. In many cases, existing drugs such as benzimidazoles, diethylcarbamazine, ivermectin and praziquantel are insufficiently efficacious, contraindicated in some populations, or at risk of the development of resistance, thereby impeding progress towards World Health Organization goals to control or eliminate these neglected tropical diseases. However, there has been limited recent progress in developing new drugs for these diseases due to lack of commercial attractiveness, leading to the introduction of novel, more efficient models for drug innovation that attempt to reduce the cost of research and development. Open science aims to achieve this by encouraging collaboration and the sharing of data and resources between organisations. In this review we discuss how open science has been applied to anthelmintic drug discovery. Open resources, including genomic information from many parasites, are enabling the identification of targets for new antiparasitic agents. Phenotypic screening remains important, and there has been much progress in open-source systems for compound screening with parasites, including motility assays but also high content assays with more detailed investigation of helminth physiology. Distributed open science compound screening programs, such as the Medicines for Malaria Venture Pathogen Box, have been successful at facilitating screening in diverse assays against many different parasite pathogens and models. Of the compounds identified so far in these screens, tolfenpyrad, a repurposed insecticide, shows significant promise and there has been much progress in creating more potent and selective derivatives. This work exemplifies how open science approaches can catalyse drug discovery against neglected diseases.
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