Triclabendazole and clofazimine reduce replication and spermine uptake in vitro in Toxoplasma gondii.

Toxoplasmosis is a worldwide zoonosis caused by the protozoan parasite Toxoplasma gondii. Although this infection is generally asymptomatic in immunocompetent individuals, it can cause serious clinical manifestations in newborns with congenital infection or in immunocompromised patients. As current treatments are not always well tolerated, there is an urgent need to find new drugs against human toxoplasmosis. Drug repurposing has gained considerable momentum in the last decade and is a particularly attractive approach for the search of therapeutic alternatives to treat rare and neglected diseases. Thus, in this study, we investigated the antiproliferative effect of several repurposed drugs. Of these, clofazimine and triclabendazole displayed a higher selectivity against T. gondii, affecting its replication. Furthermore, both compounds inhibited spermine incorporation into the parasite, which is necessary for the formation of other polyamines. The data reported here indicate that clofazimine and triclabendazole could be used for the treatment of human toxoplasmosis and confirms that drug repurposing is an excellent strategy to find new therapeutic targets of intervention.

A Combined Ligand- and Structure-Based Virtual Screening To Identify Novel NaV1.2 Blockers: In Vitro Patch Clamp Validation and In Vivo Anticonvulsant Activity.

Epilepsy is a neurological disorder characterized by recurrent seizures that arise from abnormal electrical activity in the brain. Voltage-gated sodium channels (NaVs), responsible for the initiation and propagation of action potentials in neurons, play a critical role in the pathogenesis of epilepsy. This study sought to discover potential anticonvulsant compounds that interact with NaVs, specifically, the brain subtype hNaV1.2. A ligand-based QSAR model and a docking model were constructed, validated, and applied in a parallel virtual screening over the DrugBank database. Montelukast, Novobiocin, and Cinnarizine were selected for in vitro testing, using the patch-clamp technique, and all of them proved to inhibit hNaV1.2 channels heterologously expressed in HEK293 cells. Two hits were evaluated in the GASH/Sal model of audiogenic seizures and demonstrated promising activity, reducing the severity of sound-induced seizures at the doses tested. The combination of ligand- and structure-based models presents a valuable approach for identifying potential NaV inhibitors. These findings may provide a basis for further research into the development of new antiseizure drugs for the treatment of epilepsy.

Garbage in, garbage out: how reliable training data improved a virtual screening approach against SARS-CoV-2 MPro.

Introduction: The identification of chemical compounds that interfere with SARS-CoV-2 replication continues to be a priority in several academic and pharmaceutical laboratories. Computational tools and approaches have the power to integrate, process and analyze multiple data in a short time. However, these initiatives may yield unrealistic results if the applied models are not inferred from reliable data and the resulting predictions are not confirmed by experimental evidence. Methods: We undertook a drug discovery campaign against the essential major protease (MPro) from SARS-CoV-2, which relied on an in silico search strategy -performed in a large and diverse chemolibrary- complemented by experimental validation. The computational method comprises a recently reported ligand-based approach developed upon refinement/learning cycles, and structure-based approximations. Search models were applied to both retrospective (in silico) and prospective (experimentally confirmed) screening. Results: The first generation of ligand-based models were fed by data, which to a great extent, had not been published in peer-reviewed articles. The first screening campaign performed with 188 compounds (46 in silico hits and 100 analogues, and 40 unrelated compounds: flavonols and pyrazoles) yielded three hits against MPro (IC50 ≤ 25 µM): two analogues of in silico hits (one glycoside and one benzo-thiazol) and one flavonol. A second generation of ligand-based models was developed based on this negative information and newly published peer-reviewed data for MPro inhibitors. This led to 43 new hit candidates belonging to different chemical families. From 45 compounds (28 in silico hits and 17 related analogues) tested in the second screening campaign, eight inhibited MPro with IC50 = 0.12-20 µM and five of them also impaired the proliferation of SARS-CoV-2 in Vero cells (EC50 7-45 µM). Discussion: Our study provides an example of a virtuous loop between computational and experimental approaches applied to target-focused drug discovery against a major and global pathogen, reaffirming the well-known "garbage in, garbage out" machine learning principle.

Synthesis and biological evaluation of new antiseizure compounds derived from valproic acid.

Background: New hybrid compounds were synthesized by linking the valproic acid (VPA) structure with other anticonvulsant/anti-inflammatory scaffolds. Materials & methods: The chemistry involved the incorporation of the linker oxymethyl ester into VPA, followed by reaction with the second scaffold. The antiseizure effects were investigated by the maximal electroshock seizure test, and the most active compound was additionally evaluated in the 6 Hz test and pentylenetetrazol test in mice. Results: The compounds showed protection against seizures. The hybrid structure with the butylparaben scaffold exhibited an ED50 of 8.265 mg/kg (0.0236 mmol/Kg) in the maximal electroshock seizure test and 50.00 mg/kg (0.147 mmol/kg) in the 6 Hz test. Conclusion: The antiseizure activity of the synthesized compounds highlighted the potential of hybrid structures to treat multifactorial diseases such as epilepsy.

This article focuses on the design of new anticonvulsant compounds that combine the chemical structure of valproic acid with other interesting scaffolds with anticonvulsant or anti-inflammatory properties. These compounds protected against in vivo acute seizure models (mice). The results revealed the capacity of combining known scaffolds into a single structure to generate new active compounds with multitarget purposes.

A combined ligand and target-based virtual screening strategy to repurpose drugs as putrescine uptake inhibitors with trypanocidal activity.

Chagas disease, also known as American trypanosomiasis, is a neglected tropical disease caused by the protozoa Trypanosoma cruzi, affecting nearly 7 million people only in the Americas. Polyamines are essential compounds for parasite growth, survival, and differentiation. However, because trypanosomatids are auxotrophic for polyamines, they must be obtained from the host by specific transporters. In this investigation, an ensemble of QSAR classifiers able to identify polyamine analogs with trypanocidal activity was developed. Then, a multi-template homology model of the dimeric polyamine transporter of T. cruzi, TcPAT12, was created with Rosetta, and then refined by enhanced sampling molecular dynamics simulations. Using representative snapshots extracted from the trajectory, a docking model able to discriminate between active and inactive compounds was developed and validated. Both models were applied in a parallel virtual screening campaign to repurpose known drugs as anti-trypanosomal compounds inhibiting polyamine transport in T. cruzi. Montelukast, Quinestrol, Danazol, and Dutasteride were selected for in vitro testing, and all of them inhibited putrescine uptake in biochemical assays, confirming the predictive ability of the computational models. Furthermore, all the confirmed hits proved to inhibit epimastigote proliferation, and Quinestrol and Danazol were able to inhibit, in the low micromolar range, the viability of trypomastigotes and the intracellular growth of amastigotes.

Identification of New Carbonic Anhydrase VII Inhibitors by Structure-Based Virtual Screening.

Human carbonic anhydrase VII (hCA VII) constitutes a promising molecular target for the treatment of epileptic seizures and other central nervous system disorders due to its almost exclusive expression in neurons. Achieving isoform selectivity is one of the main challenges for the discovery of new hCA inhibitors, since nonspecific inhibition may lead to tolerance and side effects. In the present work, we report the development of a molecular docking protocol based on AutoDock4Zn for the search of new hCA VII inhibitors by virtual screening. The docking protocol was applied to the screening of two sets of compounds: a ZINC15 subset of sulfur-containing structures and an in-house library consisting of synthetic and commercial candidates (including approved drugs). Five compounds were selected from the first screening campaign and three from the second one, and they were tested in vitro against the enzyme. Among the eight selected structures, four showed Ki values in the low nanomolar range. These confirmed hits include three approved drugs: meloxicam, piroxicam, and nitrofurantoin, which also showed good selectivity for hCA VII versus hCA II.

Structure-Based Virtual Screening Identifies Novobiocin, Montelukast, and Cinnarizine as TRPV1 Modulators with Anticonvulsant Activity In Vivo.

The transient receptor potential vanilloid 1 (TRPV1) receptor is a nonselective cation channel, known to be involved in the regulation of many important physiological and pathological processes. In the last few years, it has been proposed as a promising target to develop novel anticonvulsant compounds. However, thermoregulatory effects associated with the channel inhibition have hampered the path for TRPV1 antagonists to become marketed drugs. In this regard, we conducted a structure-based virtual screening campaign to find potential TRPV1 modulators among approved drugs, which are known to be safe and thermally neutral. To this end, different docking models were developed and validated by assessing their pose and score prediction powers. Novobiocin, montelukast, and cinnarizine were selected from the screening as promising candidates for experimental testing and all of them exhibited nanomolar inhibitory activity. Moreover, the in vivo profiles showed promising results in at least one of the three models of seizures tested.

Novel Dimeric hHv1 Model and Structural Bioinformatic Analysis Reveal an ATP-Binding Site Resulting in a Channel Activating Effect.

The human voltage-gated proton channel (hHv1) is a highly selective ion channel codified by the HVCN1 gene. It plays a fundamental role in several physiological processes such as innate and adaptive immunity, insulin secretion, and sperm capacitation. Moreover, in humans, a higher hHv1 expression/function has been reported in several types of cancer cells. Here we report a multitemplate homology model of the hHv1 channel, built and refined as a dimer in Rosetta. The model was then subjected to extensive Gaussian accelerated molecular dynamics (GaMD) for enhanced conformational sampling, and representative snapshots were extracted by clustering analysis. Combining different structure- and sequence-based methodologies, we predicted a putative ATP-binding site located on the intracellular portion of the channel. Furthermore, GaMD simulations of the ATP-bound dimeric hHv1 model showed that ATP interacts with a cluster of positively charged residues from the cytoplasmic N and C terminal segments. According to the in silico predictions, we found that 3 mM intracellular ATP significantly increases the H+ current mediated by the hHv1 channel expressed in HEK293 cells and measured by the patch-clamp technique in an inside-out configuration (2.86 ± 0.63 fold over control at +40 mV). When ATP was added on the extracellular side, it was not able to activate the channel supporting the idea that the ATP-binding site resides in the intracellular face of the hHV1 channel. In a physiological and pathophysiological context, this ATP-mediated modulation could integrate the cell metabolic state with the H+ efflux, especially in cells where hHv1 channels are relevant for pH regulation, such as pancreatic ß-cells, immune cells, and cancer cells.

Strengths and Weaknesses of Docking Simulations in the SARS-CoV-2 Era: the Main Protease (Mpro) Case Study.

The scientific community is working against the clock to arrive at therapeutic interventions to treat patients with COVID-19. Among the strategies for drug discovery, virtual screening approaches have the capacity to search potential hits within millions of chemical structures in days, with the appropriate computing infrastructure. In this article, we first analyzed the published research targeting the inhibition of the main protease (Mpro), one of the most studied targets of SARS-CoV-2, by docking-based methods. An alarming finding was the lack of an adequate validation of the docking protocols (i.e., pose prediction and virtual screening accuracy) before applying them in virtual screening campaigns. The performance of the docking protocols was tested at some level in 57.7% of the 168 investigations analyzed. However, we found only three examples of a complete retrospective analysis of the scoring functions to quantify the virtual screening accuracy of the methods. Moreover, only two publications reported some experimental evaluation of the proposed hits until preparing this manuscript. All of these findings led us to carry out a retrospective performance validation of three different docking protocols, through the analysis of their pose prediction and screening accuracy. Surprisingly, we found that even though all tested docking protocols have a good pose prediction, their screening accuracy is quite limited as they fail to correctly rank a test set of compounds. These results highlight the importance of conducting an adequate validation of the docking protocols before carrying out virtual screening campaigns, and to experimentally confirm the predictions made by the models before drawing bold conclusions. Finally, successful structure-based drug discovery investigations published during the redaction of this manuscript allow us to propose the inclusion of target flexibility and consensus scoring as alternatives to improve the accuracy of the methods.

Computational and Synthetic Target-based Approaches to the Discovery of Novel Anticonvulsant Compounds.

BACKGROUND: During the past decades, an important number of anticonvulsant drugs have been incorporated into the collection of drugs to treat epilepsy. However, two main difficulties remain unsolved in therapy: the development of drug-resistant epilepsy and the occurrence of severe toxic effects caused by the medication in responsive patients. The retrospective analysis of the strategies for discovering known anticonvulsant drugs showed that screening campaigns on animal models of epilepsy have been almost the exclusive strategy for identifying the marketed compounds. However, the actual structural and functional information about the molecular targets of the anticonvulsant drugs and the increasing knowledge of the molecular alterations that generate epileptic seizures allow a more rational identification of active compounds. OBJECTIVE: This review compiles target-based strategies used for the discovery of new anticonvulsant candidates and is divided in two main topics. The first one provides an overview of the computational approaches (docking-based virtual screening and molecular dynamics) to find anticonvulsant structures that interact with the voltage-gated ion channels and the enzyme carbonic anhydrase. The second one includes the analysis of active compounds synthesized to act simultaneously on different molecular targets by the combination of pharmacophores of anticonvulsant drugs. CONCLUSION: Current knowledge of the architectures of anticonvulsant targets makes computational simulations attractive methods for the discovery and optimization of active compounds. Combining the results achieved by virtual screening of different targets could lead to multitarget compounds, as an alternative to the design of structures that merge scaffolds of known drugs.

Can drug repurposing strategies be the solution to the COVID-19 crisis?

Introduction: The COVID-19 pandemic resulted in disastrous human and economic costs, mainly due to the initial lack of specific treatments. Complementary to immunotherapies, drug repurposing is possibly the best option to arrive at COVID-19 treatments in the short term.Areas covered: Repurposing prospects undergoing clinical trials or with some level of evidence emerging from clinical studies are overviewed. The authors discuss some possible intellectual property and commercial barriers to drug repurposing, and strategies to facilitate equitable access to incoming therapeutic solutions, highlighting the importance of collaborative drug discovery models. Based on a critical analysis of the available literature about in silico screens against SARS-CoV-2 main protease, the authors illustrate how frequently overconfident conclusions are being drawn in COVID-19-related literature.Expert opinion: Most of the current clinical trials on potential COVID-19 treatments are, in fact, drug repurposing examples. In October 2020, the FDA approved a repurposed antiviral, remdesivir, as the first treatment for COVID-19. Considering the high expectations invested in approaching therapeutic solutions, the scientific community must be careful not to raise unrealistic expectations. Today more than ever, the conclusions drawn in scientific reports have to be fully supported by the level of evidence, avoiding any sort of unfounded speculation.

Citrus reticulata peel oil as an antiatherogenic agent: Hypolipogenic effect in hepatic cells, lipid storage decrease in foam cells, and prevention of LDL oxidation.

BACKGROUND AND AIMS: Hypercholesterolemia and oxidative stress are two of the most important risk factors for atherosclerosis. The aim of the present work was to evaluate mandarin (Citrus reticulata) peel oil (MPO) in cholesterol metabolism and lipid synthesis, and its antioxidant capacity. METHODS AND RESULTS: Incubation of hepatic HepG2 cells with MPO (15-60 µL/L) reduced cholesterogenesis and saponifiable lipid synthesis, demonstrated by [14C]acetate radioactivity assays. These effects were associated with a decrease in a post-squalene reaction of the mevalonate pathway. Molecular docking analyses were carried out using three different scoring functions to examine the cholesterol-lowering property of all the components of MPO against lanosterol synthase. Docking simulations proposed that minor components of MPO monoterpenes, like alpha-farnesene and neryl acetate, as well the major component, limonene and its metabolites, could be partly responsible for the inhibitory effects observed in culture assays. MPO also decreased RAW 264.7 foam cell lipid storage and its CD36 expression, and prevented low-density lipoprotein (LDL) lipid peroxidation. CONCLUSION: These results may imply a potential role of MPO in preventing atherosclerosis by a mechanism involving inhibition of lipid synthesis and storage and the decrease of LDL lipid peroxidation.

Cannabidiol (CBD) Inhibited Rhodamine-123 Efflux in Cultured Vascular Endothelial Cells and Astrocytes Under Hypoxic Conditions.

Despite the constant development of new antiepileptic drugs (AEDs), more than 30% of patients develop refractory epilepsy (RE) characterized by a multidrug-resistant (MDR) phenotype. The "transporters hypothesis" indicates that the mechanism of this MDR phenotype is the overexpression of ABC transporters such as P-glycoprotein (P-gp) in the neurovascular unit cells, limiting access of the AEDs to the brain. Recent clinical trials and basic studies have shown encouraging results for the use of cannabinoids in RE, although its mechanisms of action are still not fully understood. Here, we have employed astrocytes and vascular endothelial cell cultures subjected to hypoxia, to test the effect of cannabidiol (CBD) on the P-gp-dependent Rhodamine-123 (Rho-123) efflux. Results show that during hypoxia, intracellular Rho-123 accumulation after CBD treatment is similar to that induced by the P-gp inhibitor Tariquidar (Tq). Noteworthy, this inhibition is like that registered in non-hypoxia conditions. Additionally, docking studies predicted that CBD could behave as a P-gp substrate by the interaction with several residues in the α-helix of the P-gp transmembrane domain. Overall, these findings suggest a direct effect of CBD on the Rho-123 P-gp-dependent efflux activity, which might explain why the CBD add-on treatment regimen in RE patients results in a significant reduction in seizure frequency.

A structure-based approach towards the identification of novel antichagasic compounds: Trypanosoma cruzi carbonic anhydrase inhibitors.

Trypanosoma cruzi carbonic anhydrase (TcCA) has recently emerged as an interesting target for the design of new compounds to treat Chagas disease. In this study we report the results of a structure-based virtual screening campaign to identify novel and selective TcCA inhibitors. The combination of properly validated computational methodologies such as comparative modelling, molecular dynamics and docking simulations allowed us to find high potency hits, with KI values in the nanomolar range. The compounds also showed trypanocidal effects against T. cruzi epimastigotes and trypomastigotes. All the candidates are selective for inhibiting TcCA over the human isoform CA II, which is encouraging in terms of possible therapeutic safety and efficacy.

Design, synthesis and biological evaluation of N-substituted α-hydroxyimides and 1,2,3-oxathiazolidine-4-one-2,2-dioxides with anticonvulsant activity.

In this investigation, we studied a family of compounds with an oxathiazolidine-4-one-2,2-dioxide skeleton and their amide synthetic precursors as new anticonvulsant drugs. The cyclic structures were synthesized using a three-step protocol that include solvent-free reactions and microwave-assisted heating. The compounds were tested in vivo through maximal electroshock seizure test in mice. All the structures showed activity at the lower doses tested (30 mg/Kg) and no signs of neurotoxicity were detected. Compound encoded as 1g displayed strong anticonvulsant effects in comparison with known anticonvulsants (ED50 = 29 mg/Kg). First approximations about the mechanisms of action of the cyclic structures were proposed by docking simulations and in vitro assays against sodium channels (patch clamp methods).

Searching for New Leads To Treat Epilepsy: Target-Based Virtual Screening for the Discovery of Anticonvulsant Agents.

The purpose of this investigation is to contribute to the development of new anticonvulsant drugs to treat patients with refractory epilepsy. We applied a virtual screening protocol that involved the search into molecular databases of new compounds and known drugs to find small molecules that interact with the open conformation of the Nav1.2 pore. As the 3D structure of human Nav1.2 is not available, we first assembled 3D models of the target, in closed and open conformations. After the virtual screening, the resulting candidates were submitted to a second virtual filter, to find compounds with better chances of being effective for the treatment of P-glycoprotein (P-gp) mediated resistant epilepsy. Again, we built a model of the 3D structure of human P-gp, and we validated the docking methodology selected to propose the best candidates, which were experimentally tested on Nav1.2 channels by patch clamp techniques and in vivo by the maximal electroshock seizure (MES) test. Patch clamp studies allowed us to corroborate that our candidates, drugs used for the treatment of other pathologies like Ciprofloxacin, Losartan, and Valsartan, exhibit inhibitory effects on Nav1.2 channel activity. Additionally, a compound synthesized in our lab, N, N'-diphenethylsulfamide, interacts with the target and also triggers significant Na1.2 channel inhibitory action. Finally, in vivo studies confirmed the anticonvulsant action of Valsartan, Ciprofloxacin, and N, N'-diphenethylsulfamide.

Computer-Aided Recognition of ABC Transporters Substrates and Its Application to the Development of New Drugs for Refractory Epilepsy.

Despite the introduction of more than 15 third generation antiepileptic drugs to the market from 1990 to the moment, about one third of the epileptic patients still suffer from refractory to intractable epilepsy. Several hypotheses seek to explain the failure of drug treatments to control epilepsy symptoms in such patients. The most studied one proposes that drug resistance might be related with regional overactivity of efflux transporters from the ATP-Binding Cassette (ABC) superfamily at the blood-brain barrier and/or the epileptic foci in the brain. Different strategies have been conceived to address the transporter hypothesis, among them inhibiting or down-regulating the efflux transporters or bypassing them through a diversity of artifices. Here, we review scientific evidence supporting the transporter hypothesis along with its limitations, as well as computer-assisted early recognition of ABC transporter substrates as an interesting strategy to develop novel antiepileptic drugs capable of treating refractory epilepsy linked to ABC transporters overactivity.

Novel sulfamides and sulfamates derived from amino esters: Synthetic studies and anticonvulsant activity.

We report herein the design and optimization of a novel series of sulfamides and sulfamates derived from amino esters with anticonvulsant properties. The structures were designed based on the pharmacophoric pattern previously proposed, with the aim of improving the anticonvulsant action. The compounds were obtained by a new synthetic procedure with microwave assisted heating and the use of adsorbents in the isolation process. All the derivatives showed protection against the maximal electroshock seizure test (MES test) in mice at the lowest dose tested (30 mg/kg) but they did not show significant protection against the chemical induced convulsion by pentylenetetrazole. These results verify the ability of the computational model for designing new anticonvulsants structures with anti-MES activity. Additionally, we evaluated the capacity of the synthesized structures to bind to the benzodiazepine binding site (BDZ-bs) of the γ-aminobutiric acid receptor (GABAA receptor). Some of them showed medium to low affinity for the BDZ-bs.

Sulfamide derivatives with selective carbonic anhydrase VII inhibitory action.

A set of N,N'-disubstituted sulfamides and sodium cyclamate have been tested for their inhibitory action against six isoforms of carbonic anhydrase (CA, EC 4.2.1.1) found in the brain, that is, CA I, CA II, CA VII, CA IX, CA XII and CA XIV, some of which are involved in epileptogenesis. The biological data showed interesting results for CA VII inhibition, the isozyme thought to be a novel antiepileptic target. Strong CA VII inhibitors, with Ki values in the low nanomolar-subnanomolar range were identified. Some of these derivatives showed selectivity for inhibition of CA VII versus the ubiquitous isoform CA II, for which the Ki values were in the micromolar range. Molecular modeling approaches were employed to understand the binding interactions between these compounds and the two CA isoforms, since the mechanism of action of such disubstituted sulfamides was not yet investigated by means of X-ray crystallography.

Computer-guided drug repurposing: identification of trypanocidal activity of clofazimine, benidipine and saquinavir.

In spite of remarkable advances in the knowledge on Trypanosoma cruzi biology, no medications to treat Chagas disease have been approved in the last 40 years and almost 8 million people remain infected. Since the public sector and non-profit organizations play a significant role in the research efforts on Chagas disease, it is important to implement research strategies that promote translation of basic research into the clinical practice. Recent international public-private initiatives address the potential of drug repositioning (i.e. finding second or further medical uses for known-medications) which can substantially improve the success at clinical trials and the innovation in the pharmaceutical field. In this work, we present the computer-aided identification of approved drugs clofazimine, benidipine and saquinavir as potential trypanocidal compounds and test their effects at biochemical as much as cellular level on different parasite stages. According to the obtained results, we discuss biopharmaceutical, toxicological and physiopathological criteria applied to decide to move clofazimine and benidipine into preclinical phase, in an acute model of infection. The article illustrates the potential of computer-guided drug repositioning to integrate and optimize drug discovery and preclinical development; it also proposes rational rules to select which among repositioned candidates should advance to investigational drug status and offers a new insight on clofazimine and benidipine as candidate treatments for Chagas disease. One Sentence Summary: We present the computer-guided drug repositioning of three approved drugs as potential new treatments for Chagas disease, integrating computer-aided drug screening and biochemical, cellular and preclinical tests.