Neutralising effects of small molecule toxin inhibitors on nanofractionated coagulopathic Crotalinae snake venoms

Haemotoxicity of snakes: a review of pathogenesis, clinical manifestations, novel diagnostics and challenges in management

Haemotoxicity is the most common complication of systemic envenoming following snakebite, leading to diverse clinical syndromes ranging from haemorrhagic to prothrombotic manifestations. Key haematological abnormalities include platelet dysfunction, venom-induced consumption coagulopathy, anticoagulant coagulopathy and organ-threatening thrombotic microangiopathy. Diagnostic methods include the bedside whole blood clotting test, laboratory coagulation screening and other advanced methods such as thromboelastogram and clot strength analysis. The primary management strategies are venom neutralisation with antivenom and correction of coagulopathy with blood component transfusions, while options such as plasma exchange are utilised in certain cases. Recent advancements in understanding the pathogenesis of haemotoxicity have facilitated the development of new diagnostic and treatment modalities. This review summarises current knowledge on the pathogenesis, diagnosis, clinical and laboratory manifestations and treatment of the haematological effects of snake envenoming. Furthermore, it highlights important challenges concerning diagnosis and management. Addressing these challenges is crucial for achieving the WHO's goal of reducing deaths and disabilities caused by snakebites by 2030.

The Toxin Diversity, Cytotoxicity, and Enzymatic Activity of Cape Cobra (Naja nivea) Venom

"True" cobras (genus Naja) are among the venomous snakes most frequently involved in snakebite accidents in Africa and Asia. The Cape cobra (Naja nivea) is one of the African cobras of highest medical importance, but much remains to be learned about its venom. Here, we used a shotgun proteomics approach to better understand the qualitative composition of N. nivea venom and tested its cytotoxicity and protease activity as well as its effect on intracellular Ca2+ release and NO synthesis. We identified 156 venom components representing 17 protein families, with the dominant ones being three-finger toxins, mostly of the short-chain type. Two-thirds of the three-finger toxin entries identified were assigned as cytotoxins, while the remainder were categorized as neurotoxins, including short-chain, long-chain, and ancestral three-finger toxins. We also identified snake venom metalloproteinases and members of CRISP, l-amino acid oxidase, and other families. Protease activity and its effect on intracellular Ca2+ release and NO synthesis were low. Phospholipase A2 activity was surprisingly high, despite this toxin family being marginally recovered in the analyzed venom. Cytotoxicity was relevant only at higher venom concentrations, with macrophage and neuroblastoma cell lines showing the lowest viability. These results are in line with the predominantly neurotoxic envenomation symptoms caused by Cape cobra bites. The present overview of the qualitatively complex and functionally intriguing venom of N. nivea may provide insights into the pathobiochemistry of this species' venom.

Plug and play virus-like particles for the generation of anti-toxin antibodies

Snakebite is a major global health concern, for which antivenom remains the only approved treatment to neutralise the harmful effects of the toxins. However, some medically important toxins are poorly immunogenic, resulting in reduced efficacy of the final product. Boosting the immunogenicity of these toxins in the commercial antivenom immunising mixtures could be an effective strategy to improve the final dose efficacy, and displaying snake antigens on Virus-like particles (VLPs) is one method for this. However, despite some applications in the field of snakebite, VLPs have yet to be explored in methods that could be practical at an antivenom manufacturing scale. Here we describe the utilisation of a "plug and play" VLP system to display immunogenic linear peptide epitopes from three finger toxins (3FTxs) and generate anti-toxin antibodies. Rabbits were immunised with VLPs displaying individual consensus linear epitopes and their antibody responses were characterised by immunoassay. Of the three experimental consensus sequences, two produced antibodies capable of recognising the consensus peptides, whilst only one of these could also recognise native whole toxins. Further characterisation of antibodies raised against this peptide demonstrated a sub-class specific response, and that these were able to elicit partially neutralising antibody responses, resulting in increased survival times in a murine snakebite envenoming model.

Aligning Post-Column ESI-MS, MALDI-MS, and Coagulation Bioassay Data of Naja spp., Ophiophagus hannah, and Pseudonaja textillis Venoms Chromatographically to Assess MALDI-MS and ESI-MS Complementarity with Correlation of Bioactive Toxins to Mass Spectrometric Data

Snakebite is a serious health issue in tropical and subtropical areas of the world and results in various pathologies, such as hemotoxicity, neurotoxicity, and local swelling, blistering, and tissue necrosis around the bite site. These pathologies may ultimately lead to permanent morbidity and may even be fatal. Understanding the chemical and biological properties of individual snake venom toxins is of great importance when developing a newer generation of safer and more effective snakebite treatments. Two main approaches to ionizing toxins prior to mass spectrometry (MS) analysis are electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI). In the present study, we investigated the use of both ESI-MS and MALDI-MS as complementary techniques for toxin characterization in venom research. We applied nanofractionation analytics to separate crude elapid venoms using reversed-phase liquid chromatography (RPLC) and high-resolution fractionation of the eluting toxins into 384-well plates, followed by online LC-ESI-MS measurements. To acquire clear comparisons between the two ionization approaches, offline MALDI-MS measurements were performed on the nanofractionated toxins. For comparison to the LC-ESI-MS data, we created so-called MALDI-MS chromatograms of each toxin. We also applied plasma coagulation assaying on 384-well plates with nanofractionated toxins to demonstrate parallel biochemical profiling within the workflow. The plotting of post-column acquired MALDI-MS data as so-called plotted MALDI-MS chromatograms to directly align the MALDI-MS data with ESI-MS extracted ion chromatograms allows the efficient correlation of intact mass toxin results from the two MS-based soft ionization approaches with coagulation bioassay chromatograms. This facilitates the efficient correlation of chromatographic bioassay peaks with the MS data. The correlated toxin masses from ESI-MS and/or MALDI-MS were all around 6-8 or 13-14 kDa, with one mass around 20 kDa. Between 24 and 67% of the toxins were observed with good intensity from both ionization methods, depending on the venom analyzed. All Naja venoms analyzed presented anticoagulation activity, whereas pro-coagulation was only observed for the Pseudonaja textillis venom. The data of MALDI-MS can provide complementary identification and characterization power for toxin research on elapid venoms next to ESI-MS.

Dual-Modal Cellular Nanoparticles for Continuous Neurotoxin Detoxification

Neurotoxins are known for their extreme lethality. However, due to their enormous diversity, effective and broad-spectrum countermeasures are lacking. This study presents a dual-modal cellular nanoparticle (CNP) formulation engineered for continuous neurotoxin neutralization. The formulation involves encapsulating the metabolic enzyme N-sulfotransferase (SxtN) into metal-organic framework (MOF) nanoparticle cores and coating them with a natural neuronal membrane, termed "Neuron-MOF/SxtN-NPs". The resulting nanoparticles combine membrane-enabled broad-spectrum neurotoxin neutralization with enzyme payload-enabled continuous neurotoxin neutralization. The studies confirm the protection of the enzyme payload by the MOF core and validate the continuous neutralization of saxitoxin (STX). In vivo studies conducted using a mouse model of STX intoxication reveal markedly improved survival rates compared with control groups. Furthermore, acute toxicity assessments show no adverse effects associated with the administration of Neuron-MOF/SxtN-NPs in healthy mice. Overall, Neuron-MOF/SxtN-NPs represent a unique biomimetic nanomedicine platform poised to effectively neutralize neurotoxins, marking an important advancement in the field of countermeasure nanomedicine.

Assessing Target Specificity of the Small Molecule Inhibitor MARIMASTAT to Snake Venom Toxins: A Novel Application of Thermal Proteome Profiling

New treatments that circumvent the pitfalls of traditional antivenom therapies are critical to address the problem of snakebite globally. Numerous snake venom toxin inhibitors have shown promising cross-species neutralization of medically significant venom toxins in vivo and in vitro. The development of high-throughput approaches for the screening of such inhibitors could accelerate their identification, testing, and implementation and thus holds exciting potential for improving the treatments and outcomes of snakebite envenomation worldwide. Energetics-based proteomic approaches, including thermal proteome profiling and proteome integral solubility alteration (PISA) assays, represent "deep proteomics" methods for high throughput, proteome-wide identification of drug targets and ligands. In the following study, we apply thermal proteome profiling and PISA methods to characterize the interactions between venom toxin proteoforms in Crotalus atrox (Western Diamondback Rattlesnake) and the snake venom metalloprotease (SVMP) inhibitor marimastat. We investigate its venom proteome-wide effects and characterize its interactions with specific SVMP proteoforms, as well as its potential targeting of non-SVMP venom toxin families. We also compare the performance of PISA thermal window and soluble supernatant with insoluble precipitate using two inhibitor concentrations, providing the first demonstration of the utility of a sensitive high-throughput PISA-based approach to assess the direct targets of small molecule inhibitors for snake venom.

High-throughput discovery of highly selective reversible hMAO-B inhibitors based on at-line nanofractionation

Human monoamine oxidase B (hMAO-B) has emerged as a pivotal therapeutic target for Parkinson's disease. Due to adverse effects and shortage of commercial drugs, there is a need for novel, highly selective, and reversible hMAO-B inhibitors with good blood-brain barrier permeability. In this study, a high-throughput at-line nanofractionation screening platform was established with extracts from Chuanxiong Rhizoma, which resulted in the discovery of 75 active compounds, including phenolic acids, volatile oils, and phthalides, two of which were highly selective novel natural phthalide hMAO-B inhibitors that were potent, selective, reversible and had good blood‒brain permeability. Molecular docking and molecular dynamics simulations elucidated the inhibition mechanism. Sedanolide (IC50 = 103 nmol/L; SI = 645) and neocnidilide (IC50 = 131 nmol/L; SI = 207) demonstrated their excellent potential as hMAO-B inhibitors. They offset the limitations of deactivating enzymes associated with irreversible hMAO-B inhibitors such as rasagiline. In SH-SY5Y cell assays, sedanolide (EC50 = 0.962 μmol/L) and neocnidilide (EC50 = 1.161 μmol/L) exhibited significant neuroprotective effects, comparable to the positive drugs rasagiline (EC50 = 0.896 μmol/L) and safinamide (EC50 = 1.079 μmol/L). These findings underscore the potential of sedanolide as a novel natural hMAO-B inhibitor that warrants further development as a promising drug candidate.

Unraveling snake venom phospholipase A2: an overview of its structure, pharmacology, and inhibitors

Snake bite is a neglected disease that affects millions of people worldwide. WHO reported approximately 5 million people are bitten by various species of snakes each year, resulting in nearly 1 million deaths and an additional three times cases of permanent disability. Snakes utilize the venom mainly for immobilization and digestion of their prey. Snake venom is a composition of proteins and enzymes which is responsible for its diverse pharmacological action. Snake venom phospholipase A2 (SvPLA2) is an enzyme that is present in every snake species in different quantities and is known to produce remarkable functional diversity and pharmacological action like inflammation, necrosis, myonecrosis, hemorrhage, etc. Arachidonic acid, a precursor to eicosanoids, such as prostaglandins and leukotrienes, is released when SvPLA2 catalyzes the hydrolysis of the sn-2 positions of membrane glycerophospholipids, which is responsible for its actions. Polyvalent antivenom produced from horses or lambs is the standard treatment for snake envenomation, although it has many drawbacks. Traditional medical practitioners treat snake bites using plants and other remedies as a sustainable alternative. More than 500 plant species from more than 100 families reported having venom-neutralizing abilities. Plant-derived secondary metabolites have the ability to reduce the venom's adverse consequences. Numerous studies have documented the ability of plant chemicals to inhibit the enzymes found in snake venom. Research in recent years has shown that various small molecules, such as varespladib and methyl varespladib, effectively inhibit the PLA2 toxin. In the present article, we have overviewed the knowledge of snake venom phospholipase A2, its classification, and the mechanism involved in the pathophysiology of cytotoxicity, myonecrosis, anticoagulation, and inflammation clinical application and inhibitors of SvPLA2, along with the list of studies carried out to evaluate the potency of small molecules like varespladib and secondary metabolites from the traditional medicine for their anti-PLA2 effect.

Considerations for the development of a field-based medical device for the administration of adjunctive therapies for snakebite envenoming

The timely administration of antivenom is the most effective method currently available to reduce the burden of snakebite envenoming (SBE), a neglected tropical disease that most often affects rural agricultural global populations. There is increasing interest in the development of adjunctive small molecule and biologic therapeutics that target the most problematic venom components to bridge the time-gap between initial SBE and the administration antivenom. Unique combinations of these therapeutics could provide relief from the toxic effects of regional groupings of medically relevant snake species. The application a PRISMA/PICO literature search methodology demonstrated an increasing interest in the rapid administration of therapies to improve patient symptoms and outcomes after SBE. Advice from expert interviews and considerations regarding the potential routes of therapy administration, anatomical bite location, and species-specific venom delivery have provided a framework to identify ideal metrics and potential hurdles for the development of a field-based medical device that could be used immediately after SBE to deliver adjunctive therapies. The use of subcutaneous (SC) or intramuscular (IM) injection were identified as potential routes of administration of both small molecule and biologic therapies. The development of a field-based medical device for the delivery of adjunctive SBE therapies presents unique challenges that will require a collaborative and transdisciplinary approach to be successful.

Analytical Size Exclusion Chromatography Coupled with Mass Spectrometry in Parallel with High-Throughput Venomics and Bioassaying for Venom Profiling

Modern analytical size exclusion chromatography (SEC) is a suitable technique to separate venom toxin families according to their size characteristics. In this study, a method was developed to separate intact venom toxins from Bungarus multicinctus and Daboia russelii venoms via analytical SEC using volatile, non-salt-containing eluents for post-column mass spectrometry, coagulation bioassaying and high-throughput venomics. Two venoms were used to demonstrate the method developed. While the venom of Bungaurs multicinctus is known to exert anticoagulant effects on plasma, in this study, we showed the existence of both procoagulant toxins and anticoagulant toxins. For Daboia russelii venom, the method revealed characteristic procoagulant effects, with a 90 kDa mass toxin detected and matched with the Factor X-activating procoagulant heterotrimeric glycoprotein named RVV-X. The strong procoagulant effects for this toxin show that it was most likely eluted from size exclusion chromatography non-denatured. In conclusion, the separation of snake venom by size gave the opportunity to separate some specific toxin families from each other non-denatured, test these for functional bioactivities, detect the eluting mass on-line via mass spectrometry and identify the eluted toxins using high-throughput venomics.

Pathophysiological and Clinical Significance of Crotalus durissus cascavella Venom-Induced Pulmonary Impairment in a Murine Model

Crotalus venom has broad biological activity, including neurotoxic, myotoxic, hematologic, and cytotoxic compounds that induce severe systemic repercussions. We evaluated the pathophysiological and clinical significance of Crotalus durissus cascavella (Cdc) venom-induced pulmonary impairment in mice. We conducted a randomized experimental study, involving 72 animals intraperitoneally inoculated with saline solution in the control group (CG), as well as venom in the experimental group (EG). The animals were euthanized at predetermined intervals (1 h, 3 h, 6 h, 12 h, 24 h, and 48 h), and lung fragments were collected for H&E and Masson histological analysis. The CG did not present inflammatory alterations in pulmonary parenchyma. In the EG, interstitial and alveolar swelling, necrosis, septal losses followed by alveolar distensions, and areas of atelectasis in the pulmonary parenchyma were observed after three hours. The EG morphometric analysis presented pulmonary inflammatory infiltrates at all time intervals, being more significant at three and six (p = 0.035) and six and 12 h (p = 0.006). The necrosis zones were significant at intervals of one and 24 h (p = 0.001), one and 48 h (p = 0.001), and three and 48 h (p = 0.035). Crotalus durissus cascavella venom induces a diffuse, heterogeneous, and acute inflammatory injury in the pulmonary parenchyma, with potential clinical implications for respiratory mechanics and gas exchange. The early recognition and prompt treatment of this condition are essential to prevent further lung injury and to improve outcomes.

A fast-acting brain-targeted nano-delivery system with ultra-simple structure for brain emergency poisoning rescue

Treatment for acute brain conditions remains a major challenge owing to the unavailability of antidotes, especially for organophosphorus compounds, exposure to which leads to rapid death. Despite recent advances in brain-targeted nano delivery systems (BTNDS), the traditional ones which have been developed will likely not lead to the quick release of an antidote, which is essential to counteract fast neurotoxic effects. Herein, we present a BTNDS using thermosensitive liposomes, without the need for functionalization, to obtain a platform for brain-targeted delivery, which has a simple structure and thus can be easily synthesized and scaled-up. The brain-targeting effect of BTNDS was amplified by phospholipase A2 (PLA2), an inflammatory biomarker. The combination of PLA2 and BTNDS significantly improved brain targeting, leading to an excellent emergency rescue effect - 83- and 4.8-fold better cerebral AChE reactivation response and survival time, respectively. These findings provide a promising strategy to generate a facile, druggable, and effective BTNDS.

Venom biotechnology: casting light on nature's deadliest weapons using synthetic biology

Venoms are complex chemical arsenals that have evolved independently many times in the animal kingdom. Venoms have attracted the interest of researchers because they are an important innovation that has contributed greatly to the evolutionary success of many animals, and their medical relevance offers significant potential for drug discovery. During the last decade, venom research has been revolutionized by the application of systems biology, giving rise to a novel field known as venomics. More recently, biotechnology has also made an increasing impact in this field. Its methods provide the means to disentangle and study venom systems across all levels of biological organization and, given their tremendous impact on the life sciences, these pivotal tools greatly facilitate the coherent understanding of venom system organization, development, biochemistry, and therapeutic activity. Even so, we lack a comprehensive overview of major advances achieved by applying biotechnology to venom systems. This review therefore considers the methods, insights, and potential future developments of biotechnological applications in the field of venom research. We follow the levels of biological organization and structure, starting with the methods used to study the genomic blueprint and genetic machinery of venoms, followed gene products and their functional phenotypes. We argue that biotechnology can answer some of the most urgent questions in venom research, particularly when multiple approaches are combined together, and with other venomics technologies.

Current situation of snakebites envenomation in the Neotropics: Biotechnology, a versatile tool in the production of antivenoms

Snakebite envenomation is a neglected tropical disease that affects millions of people around the world with a great impact on health and the economy. Unfortunately, public health programs do not include this kind of disease as a priority in their social programs. Cases of snakebite envenomations in the Neotropics are inaccurate due to inadequate disease management from medical records to the choice of treatments. Victims of snakebite envenomation are primarily found in impoverished agricultural areas where remote conditions limit the availability of antivenom. Antivenom serum is the only Food and Drug Administration-approved treatment used up to date. However, it has several disadvantages in terms of safety and effectiveness. This review provides a comprehensive insight dealing with the current epidemiological status of snakebites in the Neotropics and technologies employed in antivenom production. Also, modern biotechnological tools such as transcriptomic, proteomic, immunogenic, high-density peptide microarray and epitope mapping are highlighted for producing new-generation antivenom sera. These results allow us to propose strategic solutions in the Public Health Sector for managing this disease. Keywords: antivenom, biotechnology, neglected tropical disease, omics, recombinant antibody.

High-Resolution Bioassay Profiling with Complemented Sensitivity and Resolution for Pancreatic Lipase Inhibitor Screening

How to rapidly and accurately screen bioactive components from complex natural products remains a major challenge. In this study, a screening platform for pancreatic lipase (PL) inhibitors was established by combining magnetic beads-based ligand fishing and high-resolution bioassay profiling. This platform was well validated using a mixture of standard compounds, i.e., (-)- epigallocatechin gallate (EGCG), luteolin and schisandrin. The dose-effect relationship of high-resolution bioassay profiling was demonstrated by the standard mixture with different concentrations for each compound. The screening of PL inhibitors from green tea extract at the concentrations of 0.2, 0.5 and 1.0 mg/mL by independent high-resolution bioassay profiling was performed. After sample pre-treatment by ligand fishing, green tea extract at the concentration of 0.2 mg/mL was specifically enriched and simplified, and consequently screened through the high-resolution bioassay profiling. As a result, three PL inhibitors, i.e., EGCG, (-)-Gallocatechin gallate (GCG) and (-)-Epicatechin gallate (ECG), were rapidly identified from the complex matrix. The established platform proved to be capable of enriching affinity binders and eliminating nonbinders in sample pre-treatment by ligand fishing, which overcame the technical challenges of high-resolution bioassay profiling in the aspects of sensitivity and resolution. Meanwhile, the high-resolution bioassay profiling possesses the ability of direct bioactive assessment, parallel structural analysis and identification after separation. The established platform allowed more accurate and rapid screening of PL inhibitors, which greatly facilitated natural product-based drug screening.

Pharmacological re-assessment of traditional medicinal plants-derived inhibitors as antidotes against snakebite envenoming: A critical review

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional healers have used medicinal plants to treat snakebite envenomation worldwide; however, mostly without scientific validation. There have been many studies on the therapeutic potential of the natural products against snake envenomation.

AIM OF THE STUDY

This review has highlighted snake venom inhibitory activity of bioactive compounds and peptides from plants that have found a traditional use in treating snakebite envenomation. We have systematically reviewed the scenario of different phases of natural snake venom inhibitors characterization covering a period from 1994 until the present and critically analysed the lacuna of the studies if any, and further scope for their translation from bench to bedside.

MATERIALS AND METHODS

The medicinal plant-derived compounds used against snakebite therapy were reviewed from the available literature in public databases (Scopus, MEDLINE) from 1994 till 2020. The search words used were 'natural inhibitors against snakebite,' 'natural products as therapeutics against snakebite,' 'natural products as antidote against snake envenomation,' ' snake venom toxin natural inhibitors,' 'snake venom herbal inhibitors'. However, the scope of this review does not include computational (in silico) predictions without any wet laboratory validation and snake venom inhibitory activity of the crude plant extracts. In addition, we have also predicted the ADMET properties of the identified snake venom inhibitors to highlight their valuable pharmacokinetics for future clinical studies.

RESULTS

The therapeutic application of plant-derived natural inhibitors to treat snakebite envenomation as an auxiliary to antivenom therapy has been gaining significant momentum. Pharmacological reassessment of the natural compounds derived from traditional medicinal plants has demonstrated inhibition of the principal toxic enzymes of snake venoms at various extents to curb the lethal and/or deleterious effects of venomous snakebite. Nevertheless, such molecules are yet to be commercialized for clinical application in the treatment of snakebite. There are many obstacles in the marketability of the plant-derived natural products as snake envenomation antidote and strategies must be explored for the translation of these compounds from drug candidates to their clinical application.

CONCLUSION

In order to minimize the adverse implications of snake envenomation, strategies must be developed for the smooth transition of these plant-derived small molecule inhibitors from bench to bedside. In this article we have presented an inclusive review and have critically analysed natural products for their therapeutic potential against snake envenomation, and have proposed a road map for use of natural products as antidote against snakebite.

In vitro and in vivo preclinical venom inhibition assays identify metalloproteinase inhibiting drugs as potential future treatments for snakebite envenoming by Dispholidus typus

Snakebite envenoming affects more than 250,000 people annually in sub-Saharan Africa. Envenoming by Dispholidus typus (boomslang) results in venom-induced consumption coagulopathy (VICC), whereby highly abundant prothrombin-activating snake venom metalloproteinases (SVMPs) consume clotting factors and deplete fibrinogen. The only available treatment for D. typus envenoming is the monovalent SAIMR Boomslang antivenom. Treatment options are urgently required because this antivenom is often difficult to source and, at US$6000/vial, typically unaffordable for most snakebite patients. We therefore investigated the in vitro and in vivo preclinical efficacy of four SVMP inhibitors to neutralise the effects of D. typus venom; the matrix metalloproteinase inhibitors marimastat and prinomastat, and the metal chelators dimercaprol and DMPS. The venom of D. typus exhibited an SVMP-driven procoagulant phenotype in vitro. Marimastat and prinomastat demonstrated equipotent inhibition of the SVMP-mediated procoagulant activity of the venom in vitro, whereas dimercaprol and DMPS showed considerably lower potency. However, when tested in preclinical murine models of envenoming using mixed sex CD1 mice, DMPS and marimastat demonstrated partial protection against venom lethality, demonstrated by prolonged survival times of experimental animals, whereas dimercaprol and prinomastat failed to confer any protection at the doses tested. The preclinical results presented here demonstrate that DMPS and marimastat show potential as novel small molecule-based therapeutics for D. typus snakebite envenoming. These two drugs have been previously shown to be effective against Echis ocellatus VICC in preclinical models, and thus we conclude that marimastat and DMPS should be further explored as potentially valuable early intervention therapeutics to broadly treat VICC following snakebite envenoming in sub-Saharan Africa.

Terrestrial venomous animals, the envenomings they cause, and treatment perspectives in the Middle East and North Africa

The Middle East and Northern Africa, collectively known as the MENA region, are inhabited by a plethora of venomous animals that cause up to 420,000 bites and stings each year. To understand the resultant health burden and the key variables affecting it, this review describes the epidemiology of snake, scorpion, and spider envenomings primarily based on heterogenous hospital data in the MENA region and the pathologies associated with their venoms. In addition, we discuss the venom composition and the key medically relevant toxins of these venomous animals, and, finally, the antivenoms that are currently in use to counteract them. Unlike Asia and sub-Saharan Africa, scorpion stings are significantly more common (approximately 350,000 cases/year) than snakebites (approximately 70,000 cases/year) and present the most significant contributor to the overall health burden of envenomings, with spider bites being negligible. However, this review also indicates that there is a substantial lack of high-quality envenoming data available for the MENA region, rendering many of these estimates speculative. Our understanding of the venoms and the toxins they contain is also incomplete, but already presents clear trends. For instance, the majority of snake venoms contain snake venom metalloproteinases, while sodium channel-binding toxins and potassium channel-binding toxins are the scorpion toxins that cause most health-related challenges. There also currently exist a plethora of antivenoms, yet only few are clinically validated, and their high cost and limited availability present a substantial health challenge. Yet, some of the insights presented in this review might help direct future research and policy efforts toward the appropriate prioritization of efforts and aid the development of future therapeutic solutions, such as next-generation antivenoms.

Advances in the Therapeutic Application of Small-Molecule Inhibitors and Repurposed Drugs against Snakebite

The World Health Organization has declared snakebite as a neglected tropical disease. Antivenom administration is the sole therapy against venomous snakebite; however, several limitations of this therapy reinforce the dire need for an alternative and/or additional treatment against envenomation. Inhibitors against snake venoms have been explored from natural resources and are synthesized in the laboratory; however, repurposing of small-molecule therapeutics (SMTs) against the principal toxins of snake venoms to inhibit their lethality and/or obnoxious effect of envenomation has been garnering greater attention owing to their established pharmacokinetic properties, low-risk attributes, cost-effectiveness, ease of administration, and storage stability. Nevertheless, SMTs are yet to be approved and commercialized for snakebite treatment. Therefore, we have systematically reviewed and critically analyzed the scenario of small synthetic inhibitors and repurposed drugs against snake envenomation from 2005 to date and proposed novel approaches and commercialization strategies for the development of efficacious therapies against snake envenomation.

A Spider Toxin Exemplifies the Promises and Pitfalls of Cell-Free Protein Production for Venom Biodiscovery

Arthropod venoms offer a promising resource for the discovery of novel bioactive peptides and proteins, but the limited size of most species translates into minuscule venom yields. Bioactivity studies based on traditional fractionation are therefore challenging, so alternative strategies are needed. Cell-free synthesis based on synthetic gene fragments is one of the most promising emerging technologies, theoretically allowing the rapid, laboratory-scale production of specific venom components, but this approach has yet to be applied in venom biodiscovery. Here, we tested the ability of three commercially available cell-free protein expression systems to produce venom components from small arthropods, using U₂-sicaritoxin-Sdo1a from the six-eyed sand spider Hexophtalma dolichocephala as a case study. We found that only one of the systems was able to produce an active product in low amounts, as demonstrated by SDS-PAGE, mass spectrometry, and bioactivity screening on murine neuroblasts. We discuss our findings in relation to the promises and limitations of cell-free synthesis for venom biodiscovery programs in smaller invertebrates.

Utilisation of compounds from venoms in drug discovery

Difficult drug targets are becoming the normal course of business in drug discovery, sometimes due to large interacting surfaces or only small differences in selectivity regions. For these, a different approach is merited: compounds lying somewhere between the small molecule and the large antibody in terms of many properties including stability, biodistribution and pharmacokinetics. Venoms have evolved over millions of years to be complex mixtures of stable molecules derived from other somatic molecules, the stability comes from the pressure to be ready for delivery at a moment's notice. Snakes, spiders, scorpions, jellyfish, wasps, fish and even mammals have evolved independent venom systems with complex mixtures in their chemical arsenal. These venom-derived molecules have been proven to be useful tools, such as for the development of antihypotensive angiotensin converting enzyme (ACE) inhibitors and have also made successful drugs such as Byetta® (Exenatide), Integrilin® (Eptifibatide) and Echistatin. Only a small percentage of the available chemical space from venoms has been investigated so far and this is growing. In a new era of biological therapeutics, venom peptides present opportunities for larger target engagement surface with greater stability than antibodies or human peptides. There are challenges for oral absorption and target engagement, but there are venom structures that overcome these and thus provide substrate for engineering novel molecules that combine all desired properties. Venom researchers are characterising new venoms, species, and functions all the time, these provide great substrate for solving the challenges presented by today's difficult targets.