Chloroquine interferes with dengue-2 virus replication in U937 cells

Much ado about nothing? Discrepancy between the available data on the antiviral effect of hydroxychloroquine in March 2020 and its inclusion in COVID-19 clinical trials and outpatient prescriptions

OBJECTIVES

Many of the 2020 COVID-19 clinical trials included an (hydroxy)chloroquine ((H)CQ) arm. We aimed to juxtapose the state of science before April 2020 regarding the benefits of (H)CQ for viral infections with the number and size of the clinical trials studying (H)CQ and the volume of (H)CQ dispensed in France.

STUDY DESIGN

We identified and analysed published scientific material regarding the antiviral activity of (H)CQ and publicly available data regarding clinical trials and drug dispensation in France.

METHODS

We conducted a review of scientific publications available before April 2020 and a systematic analysis of COVID-19 clinical trials featuring (H)CQ registered on clinicaltrials.gov.

RESULTS

Before April 2020, 894 scientific publications mentioning (H)CQ for viruses other than coronaviruses were available, including 35 in vitro studies (reporting an inconstant inhibition of viral replication), 11 preclinical studies (reporting no or disputable positive effects), and 32 clinical trials (reporting no or disputable positive effects). Moreover, 67 publications on (H)CQ and coronavirus infections were available, including 12 in vitro studies (reporting an inconstant inhibition of viral replication), two preclinical studies (reporting contradictory results), and no clinical trials. Meanwhile, 253 therapeutic clinical trials featuring an HCQ arm were registered in 2020, intending to enrol 246,623 patients.

CONCLUSIONS

The number and size of (H)CQ clinical trials for COVID-19 launched in 2020 were not supported by the literature published before April 2020.

Biologics for dengue prevention: up-to-date

INTRODUCTION

Dengue is a worsening global public health problem. The vector-viral-host interactions driving the pathogenesis of dengue are multi-dimensional. Sequential dengue virus (DENV) infections with different DENV types significantly increase the risk of severe disease. Treatment is supportive in nature as there are no licensed anti-DENV antivirals or immuno-therapeutics. A single dengue vaccine has widely been licensed with two others in advanced clinical development. Dengvaxia® has been licensed in numerous countries but uptake has been slow as a result of safety signals noted in the youngest recipients and those who were dengue naïve at the time of vaccination.

AREAS COVERED

In this review, the current state of dengue vaccine and antiviral drug development will be discussed as well as new developments in controlled human infection models to support product development.

EXPERT OPINION

The world needs a safe and efficacious tetravalent dengue vaccine capable of protecting multiple different populations across a broad age range and different flavivirus immunologic backgrounds. Safe and effective antivirals are also needed to prevent or attenuate dengue disease in the unvaccinated, in cases of vaccine failure, or in high-risk populations.

Antiviral Activity of Approved Antibacterial, Antifungal, Antiprotozoal and Anthelmintic Drugs: Chances for Drug Repurposing for Antiviral Drug Discovery

Drug repurposing process aims to identify new uses for the existing drugs to overcome traditional de novo drug discovery and development challenges. At the same time, as viral infections became a serious threat to humans and the viral organism itself has a high ability to mutate genetically, and due to serious adverse effects that result from antiviral drugs, there are crucial needs for the discovery of new antiviral drugs, and to identify new antiviral effects for the exciting approved drugs towards different types of viral infections depending on the observed antiviral activity in preclinical studies or clinical findings is one of the approaches to counter the viral infections problems. This narrative review article summarized mainly the published preclinical studies that evaluated the antiviral activity of drugs that are approved and used mainly as antibacterial, antifungal, antiprotozoal, and anthelmintic drugs, and the preclinical studies included the in silico, in vitro, and in vivo findings, additionally some clinical observations were also included while trying to relate them to the preclinical findings. Finally, the structure used for writing about the antiviral activity of the drugs was according to the families of the viruses used in the studies to form a better image for the target of antiviral activity of different drugs in the different kinds of viruses and to relate between the antiviral activity of the drugs against different strains of viruses within the same viral family.

Effectiveness of Natural Antioxidants against SARS-CoV-2? Insights from the In-Silico World

The SARS CoV-2 pandemic has affected millions of people around the globe. Despite many efforts to find some effective medicines against SARS CoV-2, no established therapeutics are available yet. The use of phytochemicals as antiviral agents provides hope against the proliferation of SARS-CoV-2. Several natural compounds were analyzed by virtual screening against six SARS CoV-2 protein targets using molecular docking simulations in the present study. More than a hundred plant-derived secondary metabolites have been docked, including alkaloids, flavonoids, coumarins, and steroids. SARS CoV-2 protein targets include Main protease (MPro), Papain-like protease (PLpro), RNA-dependent RNA polymerase (RdRp), Spike glycoprotein (S), Helicase (Nsp13), and E-Channel protein. Phytochemicals were evaluated by molecular docking, and MD simulations were performed using the YASARA structure using a modified genetic algorithm and AMBER03 force field. Binding energies and dissociation constants allowed the identification of potentially active compounds. Ligand-protein interactions provide an insight into the mechanism and potential of identified compounds. Glycyrrhizin and its metabolite 18-β-glycyrrhetinic acid have shown a strong binding affinity for MPro, helicase, RdRp, spike, and E-channel proteins, while a flavonoid Baicalin also strongly binds against PLpro and RdRp. The use of identified phytochemicals may help to speed up the drug development and provide natural protection against SARS-CoV-2.

Chloroquine and pyrimethamine inhibit the replication of human respiratory syncytial virus A

Human respiratory syncytial virus (hRSV) is a major cause of respiratory illness in young children and can cause severe infections in the elderly or in immunocompromised adults. To date, there is no vaccine to prevent hRSV infections, and disease management is limited to preventive care by palivizumab in infants and supportive care for adults. Intervention with small-molecule antivirals specific for hRSV represents a good alternative, but no such compounds are currently approved. The investigation of existing drugs for new therapeutic purposes (drug repositioning) can be a faster approach to address this issue. In this study, we show that chloroquine and pyrimethamine inhibit the replication of human respiratory syncytial virus A (long strain) and synergistically increase the anti-replicative effect of ribavirin in cellulo. Moreover, chloroquine, but not pyrimethamine, inhibits hRSV replication in the mouse model. Our results show that chloroquine can potentially be an interesting compound for treatment of hRSV infection in monotherapy or in combination with other antivirals.

Antimalarial drugs-are they beneficial in rheumatic and viral diseases?-considerations in COVID-19 pandemic

The majority of the medical fraternity is continuously involved in finding new therapeutic schemes, including antimalarial medications (AMDs), which can be useful in combating the 2019-nCoV: coronavirus disease (COVID-19). For many decades, AMDs have been widely used in the treatment of malaria and various other anti-inflammatory diseases, particularly to treat autoimmune disorders of the connective tissue. The review comprises in vitro and in vivo studies, original studies, clinical trials, and consensus reports for the analysis, which were available in medical databases (e.g., PubMed). This manuscript summarizes the current knowledge about chloroquine (CQ)/hydroxychloroquine (HCQ) and shows the difference between their use, activity, recommendation, doses, and adverse effects on two groups of patients: those with rheumatic and viral diseases (including COVID-19). In the case of connective tissue disorders, AMDs are prescribed for a prolonged duration in small doses, and their effect is observed after few weeks, whereas in the case of viral infections, they are prescribed in larger doses for a short duration to achieve a quick saturation effect. In rheumatic diseases, AMDs are well tolerated, and their side effects are rare. However, in some viral diseases, the effect of AMDs is questionable or not so noticeable as suggested during the initial prognosis. They are mainly used as an additive therapy to antiviral drugs, but recent studies have shown that AMDs can diminish the efficacy of some antiviral drugs and may cause respiratory, kidney, liver, and cardiac complications.

The Rise and Fall of Chloroquine/Hydroxychloroquine as Compassionate Therapy of COVID-19

The emergence and rapid spread of novel coronavirus disease (COVID-19) has posed a serious challenge to global public health in 2020. The speed of this viral spread together with the high mortality rate has caused an unprecedented public health crisis. With no antivirals or vaccines available for the treatment of COVID-19, the medical community is presently exploring repositioning of clinically approved drugs for COVID-19. Chloroquine (CQ) and hydroxychloroquine (HCQ) have emerged as potential candidates for repositioning as anti-COVID-19 therapeutics and have received FDA authorization for compassionate use in COVID-19 patients. On March 28, 2020, the U.S. Food and Drug Administration (FDA) issued an Emergency Use Authorization (EUA) for HCQ in the treatment of COVID-19. However, it was later revoked by the FDA on June 15, 2020, after analyzing the emerging scientific data from ongoing clinical trials. Similarly, the World Health Organization (WHO) also conducted a Solidarity trial of chloroquine, hydroxychloroquine, remdesivir, lopinavir, and ritonavir. However, on May 23, 2020, the executive body of the "Solidarity trial" decided to put a temporary hold on the HCQ trial. On June 17, 2020, the WHO abruptly stopped the Solidarity trial of HCQ. The current review strives to examine the basis of compassionate use of CQ and HCQ for the treatment of COVID-19 in terms of literature evidence, establishing the antiviral efficacy of these drugs against corona and related viruses. Furthermore, the review presents a critical analysis of the clinical trial findings and also provides an insight into the dynamically changing decision on the authorization and withdrawal of HCQ as anti-COVID-19 therapy by the U.S. FDA and the WHO. Ultimately, our study necessitates an evidenced-based treatment protocol to confront the ongoing COVID-19 pandemic and not the mere observational study that mislead the public healthcare system, which paralyzes the entire world.

Strategy, Progress, and Challenges of Drug Repurposing for Efficient Antiviral Discovery

Emerging or re-emerging viruses are still major threats to public health. Prophylactic vaccines represent the most effective way to prevent virus infection; however, antivirals are more promising for those viruses against which vaccines are not effective enough or contemporarily unavailable. Because of the slow pace of novel antiviral discovery, the high disuse rates, and the substantial cost, repurposing of the well-characterized therapeutics, either approved or under investigation, is becoming an attractive strategy to identify the new directions to treat virus infections. In this review, we described recent progress in identifying broad-spectrum antivirals through drug repurposing. We defined the two major categories of the repurposed antivirals, direct-acting repurposed antivirals (DARA) and host-targeting repurposed antivirals (HTRA). Under each category, we summarized repurposed antivirals with potential broad-spectrum activity against a variety of viruses and discussed the possible mechanisms of action. Finally, we proposed the potential investigative directions of drug repurposing.

Matrix metalloproteinases in the pathogenesis of dengue viral disease: Involvement of immune system and newer therapeutic strategies

Globally, the burden due to dengue infection is increasing with a recent estimate of 96 million progressing to the disease every year. Dengue pathogenesis and the factors influencing it are not completely known. It is now widely speculated that there is an important role of matrix metalloproteinases (MMPs) in the initiation and progression of dengue pathogenesis; however, their exact roles are not fully understood. Overactivation of matrix metalloproteinases may contribute to the severity of dengue pathogenesis. Cytokines and various other mediators of inflammation interact with the vascular endothelium and matrix metalloproteinases may be one of the components among them. Extensive plasma leakage into tissue spaces may result in a shock. It is evident in the literature that MMP2 and MMP9 increase in dengue patients is correlated with the severity of the disease; however, the underlying mechanism is still unknown. Activation of innate cells and adaptive immune cells which include, B and T cells, macrophages or monocytes and dendritic cells also contribute to the dengue pathology. Newer therapeutic strategies include microRNAs, such as miR-134 (targets MMP3 and MMP1) and MicroRNA-320d, (targets MMP/TIMP proteolytic system). The use of antibodies-based therapeutics like (Andecaliximab; anti-matrix metalloproteinase-9 antibody) is also suggested against MMPs in dengue. In this review, we summarize some recent developments associated with the involvement of immune cells and their mediators associated with the matrix metalloproteinases mediated dengue pathogenesis. We highlight that, there is still very little knowledge about the MMPs in dengue pathogenesis which needs attention and extensive investigations.

Epigenetics in NAFLD/NASH: Targets and therapy

Recently non-alcoholic fatty liver disease (NAFLD) has grabbed considerable scientific attention, owing to its rapid increase in prevalence worldwide and growing burden on end-stage liver diseases. Metabolic syndrome including obesity, diabetes, and hypertension poses a grave risk to NAFLD etiology and progression. With no drugs available, the mainstay of NAFLD management remains lifestyle changes with exercise and dietary modifications. Nonselective drugs such as metformin, thiazolidinediones (TZDs), ursodeoxycholic acid (UDCA), silymarin, etc., are also being used to target the interrelated pathways for treating NAFLD. Considering the enormous disease burden and the unmet need for drugs, fresh insights into pathogenesis and drug discovery are required. The emergence of the field of epigenetics offers a convincing explanation for the basis of lifestyle, environmental, and other risk factors to influence NAFLD pathogenesis. Therefore, understanding these epigenetic modifications to target the primary cause of the disease might prove a rational strategy to prevent the disease and develop novel therapeutic interventions. Apart from describing the role of epigenetics in the pathogenesis of NAFLD as in other reviews, this review additionally provides an elaborate discussion on exploiting the high plasticity of epigenetic modifications in response to environmental cues, for developing novel therapeutics for NAFLD. Besides, this extensive review provides evidence for epigenetic mechanisms utilized by several potential drugs for NAFLD.

Repurposing Drugs for the Management of Patients with Confirmed Coronavirus Disease 2019 (COVID-19)

BACKGROUND

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), termed coronavirus disease 2019 (COVID-19) by the World Health Organization, is a newly emerging zoonotic agent that emerged in China in December 2019. No specific treatment for COVID-19 is currently available. Usual palliative treatment includes maintaining hydration and nutrition and controlling fever and cough. The clinical severity and extent of transmission need to be determined, and therapeutic options need to be developed and optimized.

METHODS

The present review discusses the recent repurposing of drugs for COVID-19 treatment.

RESULTS

Several compounds, including remdesivir, lopinavir, ritonavir, interferon-β, ribavirin, chloroquine/ hydroxychloroquine, azithromycin, tocilizumab, and ivermectin, have emerged as promising alternatives. They block the virus from entering host cells, prevent viral replication, and attenuate exacerbation of the host's immune response.

CONCLUSION

Although some evidence indicates the positive actions of different classes of compounds for the treatment of COVID-19, few clinical assays have been established to definitively demonstrate their therapeutic value in humans. Multicenter clinical studies are urgently needed to validate and standardize therapeutic regimens that involve these agents. Although science has not yet presented us with a specific drug against COVID-19, the repurposing of drugs appears to be promising in our fight against this devastating disease.

Efficacy of chloroquine or hydroxychloroquine in COVID-19 patients: a systematic review and meta-analysis

OBJECTIVES

Clinical studies of chloroquine (CQ) and hydroxychloroquine (HCQ) in COVID-19 disease reported conflicting results. We sought to systematically evaluate the effect of CQ and HCQ with or without azithromycin on outcomes of COVID-19 patients.

METHODS

We searched multiple databases, preprints and grey literature up to 17 July 2020. We pooled only adjusted-effect estimates of mortality using a random-effect model. We summarized the effect of CQ or HCQ on viral clearance, ICU admission/mechanical ventilation and hospitalization.

RESULTS

Seven randomized clinical trials (RCTs) and 14 cohort studies were included (20 979 patients). Thirteen studies (1 RCT and 12 cohort studies) with 15 938 hospitalized patients examined the effect of HCQ on short-term mortality. The pooled adjusted OR was 1.05 (95% CI 0.96-1.15, I2 = 0%). Six cohort studies examined the effect of the HCQ+azithromycin combination with a pooled adjusted OR of 1.32 (95% CI 1.00-1.75, I2 = 68.1%). Two cohort studies and four RCTs found no effect of HCQ on viral clearance. One small RCT demonstrated improved viral clearance with CQ and HCQ. Three cohort studies found that HCQ had no significant effect on mechanical ventilation/ICU admission. Two RCTs found no effect for HCQ on hospitalization risk in outpatients with COVID-19.

CONCLUSIONS

Moderate certainty evidence suggests that HCQ, with or without azithromycin, lacks efficacy in reducing short-term mortality in patients hospitalized with COVID-19 or risk of hospitalization in outpatients with COVID-19.

Repurposing New Use for Old Drug Chloroquine against Metabolic Syndrome: A Review on Animal and Human Evidence

Chloroquine (CQ) and hydroxychloroquine (HCQ) are traditional anti-malarial drugs that have been repurposed for new therapeutic uses in many diseases due to their simple usage and cost-effectiveness. The pleiotropic effects of CQ and HCQ in regulating blood pressure, glucose homeostasis, lipid, and carbohydrate metabolism have been previously described in vivo and in humans, thus suggesting their role in metabolic syndrome (MetS) prevention. The anti-hyperglycaemic, anti-hyperlipidaemic, cardioprotective, anti-hypertensive, and anti-obesity effects of CQ and HCQ might be elicited through reduction of inflammatory response and oxidative stress, improvement of endothelial function, activation of insulin signalling pathway, inhibition of lipogenesis and autophagy, as well as regulation of adipokines and apoptosis. In conclusion, the current state of knowledge supported the repurposing of CQ and HCQ usage in the management of MetS.

Novel coronavirus disease (COVID-19) pandemic: A recent mini review

The COVID-19, caused by a novel coronavirus, was declared as a global pandemic by WHO more than five months ago, and we are still experiencing a state of global emergency. More than 74.30 million confirmed cases of the COVID-19 have been reported globally so far, with an average fatality rate of almost 3.0%. Seven different types of coronaviruses had been detected from humans; three of them have resulted in severe outbreaks, i.e., MERS-CoV, SARS-CoV, and SARS-CoV-2. Phylogenetic analysis of the genomes suggests that the possible occurrence of recombination between SARS-like-CoVs from pangolin and bat might have led to the origin of SARS-CoV-2 and the COVID-19 outbreak. Coronaviruses are positive-sense, single-stranded RNA viruses and harbour a genome (30 kb) consisting of two terminal untranslated regions and twelve putative functional open reading frames (ORFs), encoding for non-structural and structural proteins. There are sixteen putative non-structural proteins, including proteases, RNA-dependent RNA polymerase, helicase, other proteins involved in the transcription and replication of SARS-CoV-2, and four structural proteins, including spike protein (S), envelope (E), membrane (M), and nucleocapsid (N). SARS-CoV-2 infection, with a heavy viral load in the body, destroys the human lungs through cytokine storm, especially in elderly persons and people with immunosuppressed disorders. A number of drugs have been repurposed and employed, but still, no specific antiviral medicine has been approved by the FDA to treat this disease. This review provides a current status of the COVID-19, epidemiology, an overview of phylogeny, mode of action, diagnosis, and possible treatment methods and vaccines.

Beyond the Surface: Endocytosis of Mosquito-Borne Flaviviruses

Flaviviruses are a group of positive-sense RNA viruses that are primarily transmitted through arthropod vectors and are capable of causing a broad spectrum of diseases. Many of the flaviviruses that are pathogenic in humans are transmitted specifically through mosquito vectors. Over the past century, many mosquito-borne flavivirus infections have emerged and re-emerged, and are of global importance with hundreds of millions of infections occurring yearly. There is a need for novel, effective, and accessible vaccines and antivirals capable of inhibiting flavivirus infection and ameliorating disease. The development of therapeutics targeting viral entry has long been a goal of antiviral research, but most efforts are hindered by the lack of broad-spectrum potency or toxicities associated with on-target effects, since many host proteins necessary for viral entry are also essential for host cell biology. Mosquito-borne flaviviruses generally enter cells by clathrin-mediated endocytosis (CME), and recent studies suggest that a subset of these viruses can be internalized through a specialized form of CME that has additional dependencies distinct from canonical CME pathways, and antivirals targeting this pathway have been discovered. In this review, we discuss the role and contribution of endocytosis to mosquito-borne flavivirus entry as well as consider past and future efforts to target endocytosis for therapeutic interventions.

The endosomal lipid bis(monoacylglycero) phosphate as a potential key player in the mechanism of action of chloroquine against SARS-COV-2 and other enveloped viruses hijacking the endocytic pathway

The anti-malarial drug Chloroquine (CQ) and its derivative hydroxychloroquine have shown antiviral activities in vitro against many viruses, including coronaviruses, dengue virus and the biosafety level 4 Nipah and Hendra paramyxoviruses. The in vivo efficacy of CQ in the treatment of COVID-19 is currently a matter of debate. CQ is a lysosomotrophic compound that accumulates in lysosomes, as well as in food vacuoles of Plasmodium falciparum. In the treatment of malaria, CQ impairs the digestion and growth of the parasite by increasing the pH of the food vacuole. Similarly, it is assumed that the antiviral effects of CQ results from the increase of lysosome pH and the inhibition of acidic proteases involved in the maturation of virus fusion protein. CQ has however other effects, among which phospholipidosis, characterized by the accumulation of multivesicular bodies within the cell. The increase in phospholipid species particularly concerns bis(monoacylglycero)phosphate (BMP), a specific lipid of late endosomes involved in vesicular trafficking and pH-dependent vesicle budding. It was shown previously that drugs like progesterone, the cationic amphiphile U18666A and the phospholipase inhibitor methyl arachidonyl fluoro phosphonate (MAFP) induce the accumulation of BMP in THP-1 cells and decrease cell infection by human immunodeficiency virus. HIV viral particles were found to be retained into large endosomal-type vesicles, preventing virus spreading. Since BMP was also reported to favour virus entry through hijacking of the endocytic pathway, we propose here that BMP could play a dual role in viral infection, with its antiviral effects triggered by lysosomotropic drugs like CQ.

Identification of an Antiviral Compound from the Pandemic Response Box that Efficiently Inhibits SARS-CoV-2 Infection In Vitro

With over 50 million currently confirmed cases worldwide, including more than 1.3 million deaths, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic has a major impact on the economy and health care system. Currently, limited prophylactic or therapeutic intervention options are available against SARS-CoV-2. In this study, 400 compounds from the antimicrobial “pandemic response box” library were screened for inhibiting properties against SARS-CoV-2. An initial screen on Vero E6 cells identified five compounds that inhibited SARS-CoV-2 replication. However, validation of the selected hits in a human lung cell line highlighted that only a single compound, namely Retro-2.1, efficiently inhibited SARS-CoV-2 replication. Additional analysis revealed that the antiviral activity of Retro-2.1 occurs at a post-entry stage of the viral replication cycle. Combined, these data demonstrate that stringent in vitro screening of preselected compounds in multiple cell lines refines the rapid identification of new potential antiviral candidate drugs targeting SARS-CoV-2.

Molecular dynamics simulation perception study of the binding affinity performance for main protease of SARS-CoV-2

Like common cold and flu, SARC-CoV-2 virus spreads by droplets of sneezes or coughs which virus affects people of various age groups. Today, this virus is almost distributed all over the world. Since binding process plays a crucial role between host and receptor, therefore, we studied the molecules intended toward inhibition process through molecular docking and molecular dynamics simulation process. From the molecular docking study, it is noteworthy that remdesivir shows better binding affinity toward the main protease of SARS-CoV2 compared to other studied drugs. Within studied phytochemicals, carnosic acid shows better binding poses toward main protease of SARS-CoV2 among studied phytochemicals. The amino acid residues GLN110 and PHE294 were almost found in all the studied interactions of drugs and phytochemicals with main protease of SARS-CoV-2. Furthermore, the results show a larger contribution of the Van der Waals energies as compared to others like electrostatic energies suggesting that ligands at the binding pocket are predominantly stabilized by hydrophobic interactions. The conformational change during ligand binding was predicted from Gibbs free energy landscape analysis through molecular dynamics simulation. We observed that, there were two main free energy basins for both docked carnosic acid complex and for docked remdesivir complex, only one main free energy basin was found in the global free energy minimum region.

Communicated by Ramaswamy H. Sarma

No benefit of hydroxychloroquine in COVID-19: Results of Systematic Review and Meta-Analysis of Randomized Controlled Trials"

BACKGROUND AND AIMS

Coronavirus pandemic is currently a global public health emergency with no definitive treatment guidelines. We conducted a systematic review and meta-analysis of the literature evaluating the efficacy of hydroxychloroquine and its related formulations in COVID-19 patients.

METHODS

A systematic search of PubMed, Scopus, MedRxiv data and Cochrane Central Register of Clinical Trials for published articles that reported the outcomes of COVID-19 patients treated with hydroxychloroquine or its compounds was done. We identified 1071 published studies and 7 studies were included in the analysis.

RESULTS

The study population consisted of a total of 4984 patients, of which 1721 (34.5%) received hydroxychloroquine or its congeners (HCQ group) while 3091 (62.01%) received standard of care or had included antiviral medication (control group). The pooled estimate of successful treatment in the hydroxychloroquine group and the control group was 77.45% and 77.87% respectively, which indicated similar clinical outcomes in patients treated with hydroxychloroquine compared to the control group. The odds ratio of a favourable outcome with hydroxychloroquine was 1.11 (95 CI 0.72 to 1.69) (p = 0.20). The pooled risk difference of favourable outcome with hydroxychloroquine versus control group was 0.00 (95 CI -0.03 to 0.03) which was statistically not significant (p = 0.10).

CONCLUSIONS

The present evidence shows no benefit of hydroxychloroquine in patients affected by mild to moderate COVID-19 disease. However, now several trials on HCQ are ongoing and hopefully more data will be available soon. Hence, the management of COVID-19 is set to change for better in the future.

Evolution of resistance to fluoroquinolones by dengue virus serotype 4 provides insight into mechanism of action and consequences for viral fitness

Drugs against flaviviruses such as dengue (DENV) and Zika (ZIKV) virus are urgently needed. We previously demonstrated that three fluoroquinolones, ciprofloxacin, enoxacin, and difloxacin, suppress replication of six flaviviruses. To investigate the barrier to resistance and mechanism(s) of action of these drugs, DENV-4 was passaged in triplicate in HEK-293 cells in the presence or absence of each drug. Resistance to ciprofloxacin was detected by the seventh passage and to difloxacin by the tenth, whereas resistance to enoxacin did not occur within ten passages. Two putative resistance-conferring mutations were detected in the envelope gene of ciprofloxacin and difloxacin-resistant DENV-4. In the absence of ciprofloxacin, ciprofloxacin-resistant viruses sustained a significantly higher viral titer than control viruses in HEK-293 and HuH-7 cells and resistant viruses were more stable than control viruses at 37 °C. These results suggest that the mechanism of action of ciprofloxacin and difloxacin involves interference with virus binding or entry.

Old Drugs with New Tricks: Efficacy of Fluoroquinolones to Suppress Replication of Flaviviruses

Repurposing FDA-approved compounds could provide the fastest route to alleviate the burden of disease caused by flaviviruses. In this study, three fluoroquinolones, enoxacin, difloxacin and ciprofloxacin, curtailed replication of flaviviruses Zika (ZIKV), dengue (DENV), Langat (LGTV) and Modoc (MODV) in HEK-293 cells at low micromolar concentrations. Time-of-addition assays suggested that enoxacin suppressed ZIKV replication at an intermediate step in the virus life cycle, whereas ciprofloxacin and difloxacin had a wider window of efficacy. A129 mice infected with 1 × 10⁵ plaque-forming units (pfu) ZIKV FSS13025 (n = 20) or phosphate buffered saline (PBS) (n = 11) on day 0 and treated with enoxacin at 10 mg/kg or 15 mg/kg or diluent orally twice daily on days 1–5 did not differ in weight change or virus titer in serum or brain. However, mice treated with enoxacin showed a significant, five-fold decrease in ZIKV titer in testes relative to controls. Mice infected with 1 × 10² pfu ZIKV (n = 13) or PBS (n = 13) on day 0 and treated with 15 mg/kg oral enoxacin or diluent twice daily pre-treatment and days 1–5 post-treatment also did not differ in weight and viral load in the serum, brain, and liver, but mice treated with enoxacin showed a significant, 2.5-fold decrease in ZIKV titer in testes relative to controls. ZIKV can be sexually transmitted, so reduction of titer in the testes by enoxacin should be further investigated.

Zinc(II)-The Overlooked Éminence Grise of Chloroquine's Fight against COVID-19?

Zn(II) is an inhibitor of SARS-CoV-2's RNA-dependent RNA polymerase, and chloroquine and hydroxychloroquine are Zn(II) ionophores-this statement gives a curious mind a lot to think about. We show results of the first clinical trials on chloroquine (CQ) and hydroxychloroquine (HCQ) in the treatment of COVID-19, as well as earlier reports on the anticoronaviral properties of these two compounds and of Zn(II) itself. Other FDA-approved Zn(II) ionophores are given a decent amount of attention and are thought of as possible COVID-19 therapeutics.

Recent advances in antiviral drug development towards dengue virus

Despite the high disease burden of dengue virus, there is no approved antiviral treatment or broadly applicable vaccine to treat or prevent dengue virus infection. In the last decade, many antiviral compounds have been identified but only few have been further evaluated in pre-clinical or clinical trials. This review will give an overview of the direct-acting and host-directed antivirals identified to date. Furthermore, important parameters for further development that is, drug properties including efficacy, specificity and stability, pre-clinical animal testing, and combinational drug therapy will be discussed.

Will Hydroxychloroquine Still Be a Game-Changer for COVID-19 by Combining Azithromycin?

Recent small-scale clinical trials have shown promising results in the use of hydroxychloroquine, an FDA approved anti-malaria drug, for the treatment of COVID-19. However, large scale, randomized and double-blind clinical trials are needed to confirm the safety and efficacy of hydroxychloroquine in COVID-19 patients. Here, we review the progress of using hydroxychloroquine or chloroquine as anti-viral agents, failed clinical trials of chloroquine in treatment of dengue virus and influenza infection, and especially the mechanism of azithromycin in inhibiting viral replication, so as to shed light on the ongoing clinical trials and further researches of hydroxychloroquine on SARS-CoV-2 infected patients.

A systematic review on use of aminoquinolines for the therapeutic management of COVID-19: Efficacy, safety and clinical trials

Recent global outbreak of the pandemic caused by coronavirus (COVID-19) emphasizes the urgent need for novel antiviral therapeutics. It can be supplemented by utilization of efficient and validated drug discovery approaches such as drug repurposing/repositioning. The well reported and clinically used anti-malarial aminoquinoline drugs (chloroquine and hydroxychloroquine) have shown potential to be repurposed to control the present pandemic by inhibition of COVID-19. The review elaborates the mechanism of action, safety (side effects, adverse effects, toxicity) and details of clinical trials for chloroquine and hydroxychloroquine to benefit the clinicians, medicinal chemist, pharmacologist actively involved in controlling the pandemic and to provide therapeutics for the treatment of COVID-19 infection.

The possible mechanisms of action of 4-aminoquinolines (chloroquine/hydroxychloroquine) against Sars-Cov-2 infection (COVID-19): A role for iron homeostasis?

The anti-malarial drugs chloroquine (CQ) and primarily the less toxic hydroxychloroquine (HCQ) are currently used to treat autoimmune diseases for their immunomodulatory and anti-thrombotic properties. They have also been proposed for the treatment of several viral infections, due to their anti-viral effects in cell cultures and animal models, and, currently, for the treatment of coronavirus disease 2019 (COVID-19), the pandemic severe acute respiratory syndrome caused by coronavirus 2 (Sars-Cov-2) infection that is spreading all over the world. Although in some recent studies a clinical improvement in COVID-19 patients has been observed, the clinical efficacy of CQ and HCQ in COVID-19 has yet to be proven with randomized controlled studies, many of which are currently ongoing, also considering pharmacokinetics, optimal dosing regimen, therapeutic level and duration of treatment and taking into account patients with different severity degrees of disease. Here we review what is currently known on the mechanisms of action of CQ and HCQ as anti-viral, anti-inflammatory and anti-thrombotic drugs and discuss the up-to-date experimental evidence on the potential mechanisms of action of CQ/HCQ in Sars-Cov2 infection and the current clinical knowledge on their efficacy in the treatment of COVID-19 patients. Given the role of iron in several human viral infections, we also propose a different insight into a number of CQ and HCQ pharmacological effects, suggesting a potential involvement of iron homeostasis in Sars-Cov-2 infection and COVID-19 clinical course.

Treatment of COVID 19-Repurposing drugs commonly used in dermatology

For the last two decades, the outbreaks of diseases caused by coronaviruses and intermittent worldwide public health emergences have reminded us that they still represent a severe threat to global health. The recent outbreak of corona virus disease 19 (COVID‐19) highlighted the urgent need for effective treatment, and initiated rapid search for therapies, able to counter the most severe disease effects. Many aspects of COVID‐19 pathogenesis are unknown, but complex interplay of direct viral damage and immune response dysregulation is underline. Intensive research is undergoing for therapeutic targets of virus and high‐efficiency and low toxicity targeted drugs. There is no available specific antiviral treatment of this disease, therefore repurposing of drugs already available for the treatment of other viral and autoimmune diseases has been a part of research efforts. Well known anti‐inflammatory properties of chloroquine and hydroxychloroquine, agents widely used in dermatology, made them potential candidates for the treatment of COVID‐19. We review pathogenesis and clinical characteristic of COVID‐19, as well as treatment options that have been under evaluation in past several months. In addition, we focus more on chloroquine and hydroxychloroquine, their pharmacological properties, clinical utility, and current recommendations for their use in COVID‐19.

Repurposing of well-known medications as antivirals: hydroxychloroquine and chloroquine - from HIV-1 infection to COVID-19

INTRODUCTION

Chloroquine (CQ) and hydroxychloroquine (HCQ) originally were prescribed for prevention or treatment of malaria, but now successfully are used in several rheumatologic diseases. In addition, in recent decades considering their immunomodulatory effects, high tolerably, and low cost, they are evaluated for various viral infections from HIV to COVID-19.

AREAS COVERED

In this review, we tried to summarize all available studies on HCQ and CQ efficacy for management of viral infections and the probable mechanisms of action. The data were collected by searching 'Hydroxychloroquine,' 'Chloroquine,' 'Viral infection,' and names of various viral infections in PubMed/MEDLINE, Scopus, and Google Scholar databases from commencement to June 2020. Out of 95 search results, 74 most relevant works were gathered.

EXPERT OPINION

HCQ/CQ showed acceptable efficacy in HIV especially as an adjuvant treatment beside routine HAART. However, for some viral infections such as ZIKA, EBOLA, SARS-CoV, and MERS-CoV, human studies are lacking. In the COVID-19 pandemic, in vitro and preliminary human studies showed encouraging findings. However, later well-designed trials and retrospective studies with large sample size not only reported non-significant efficacy but also showed more cardiac adverse reactions. Alkalinization of acid vesicles is the most important mechanism of action.

Current Perspective of Antiviral Strategies against COVID-19

COVID-19 was declared a pandemic by the World Health Organization on March 11, 2020. This novel coronavirus disease, caused by the SARS-CoV-2 virus, has resulted in severe and unprecedented social and economic disruptions globally. Since the discovery of COVID-19 in December 2019, numerous antivirals have been tested for efficacy against SARS-CoV-2 in vitro and also clinically to treat this disease. This review article discusses the main antiviral strategies currently employed and summarizes reported in vitro and in vivo efficacies of key antiviral compounds in use.

SARS-CoV-2, ACE2, and Hydroxychloroquine: Cardiovascular Complications, Therapeutics, and Clinical Readouts in the Current Settings

The rapidly evolving coronavirus disease 2019 (COVID-19, caused by severe acute respiratory syndrome coronavirus 2- SARS-CoV-2), has greatly burdened the global healthcare system and led it into crisis in several countries. Lack of targeted therapeutics led to the idea of repurposing broad-spectrum drugs for viral intervention. In vitro analyses of hydroxychloroquine (HCQ)'s anecdotal benefits prompted its widespread clinical repurposing globally. Reports of emerging cardiovascular complications due to its clinical prescription are revealing the crucial role of angiotensin-converting enzyme 2 (ACE2), which serves as a target receptor for SARS-CoV-2. In the present settings, a clear understanding of these targets, their functional aspects and physiological impact on cardiovascular function are critical. In an up-to-date format, we shed light on HCQ's anecdotal function in stalling SARS-CoV-2 replication and immunomodulatory activities. While starting with the crucial role of ACE2, we here discuss the impact of HCQ on systemic cardiovascular function, its associated risks, and the scope of HCQ-based regimes in current clinical settings. Citing the extent of HCQ efficacy, the key considerations and recommendations for the use of HCQ in clinics are further discussed. Taken together, this review provides crucial insights into the role of ACE2 in SARS-CoV-2-led cardiovascular activity, and concurrently assesses the efficacy of HCQ in contemporary clinical settings.

Facts and Myths: Efficacies of Repurposing Chloroquine and Hydroxychloroquine for the Treatment of COVID-19

The emergence of coronavirus disease 2019 (COVID-19) is caused by the 2019 novel coronavirus (2019-nCoV). The 2019-nCoV first broke out in Wuhan and subsequently spread worldwide owing to its extreme transmission efficiency. The fact that the COVID-19 cases and mortalities are reported globally and the WHO has declared this outbreak as the pandemic, the international health authorities have focused on rapid diagnosis and isolation of patients as well as search for therapies able to counter the disease severity. Due to the lack of known specific, effective and proven therapies as well as the situation of public-health emergency, drug repurposing appears to be the best armour to find a therapeutic solution against 2019-nCoV infection. Repurposing anti-malarial drugs and chloroquine (CQ)/ hydroxychloroquine (HCQ) have shown efficacy to inhibit most coronaviruses, including SARS-CoV-1 coronavirus. These CQ analogues have shown potential efficacy to inhibit 2019-nCoV in vitro that leads to focus several future clinical trials. This review discusses the possible effective roles and mechanisms of CQ analogues for interfering with the 2019-nCoV replication cycle and infection.

A review on possible modes of action of chloroquine/hydroxychloroquine: repurposing against SAR-CoV-2 (COVID-19) pandemic

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Chloroquine (CQ) has diverse modes of action against viral infections.

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CQ may interfere with SARS-CoV-2 attachment to the host ACE2 receptor.

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CQ may hamper the STING pathway to attenuate the pro-inflammatory response.

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Hydroxychloroquine (HCQ) might be a logical approach in the treatment of SARS-CoV-2 infection.

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Large clinical trials are needed before clinical recommendations of HCQ against COVID-19.

Chloroquine (CQ) and its analogue hydroxychloroquine (HCQ) have long been used worldwide as frontline drugs for the treatment and prophylaxis of human malaria. Since the first reported cases in Wuhan, China, in late December 2019, humans have been under threat from coronavirus disease 2019 (COVID-19) caused by the novel coronavirus SARS-CoV-2 (previously known as 2019-nCoV), subsequently declared a pandemic. While the world is searching for expedited approval for a vaccine, which may be only preventative and not a cure, physicians and country leaders are considering several concerted clinical trials suggesting that the age-old antimalarial drugs CQ/HCQ could be a potent therapeutic against COVID-19. Based on accumulating scientific reports, here we highlight the possible modes of action of CQ/HCQ that could justify its use against viral infections. Considering the global health crisis of the COVID-19 pandemic, the option of repurposing old drugs, e.g. CQ/HCQ, particularly HCQ, for the treatment of SARS-CoV-2 infection could be a good choice. CQ/HCQ has diverse modes of action, including alteration of the acidic environment inside lysosomes and late endosomes, preventing endocytosis, exosome release and phagolysosomal fusion, and inhibition of the host cytokine storm. One or more diverse mechanisms might work against viral infections and reduce mortality. As there is no cure for COVID-19, clinical testing of HCQ is urgently required to determine its potency against SARS-CoV-2, as this is the currently available treatment option. There remains a need to find other innovative drug candidates as possible candidates to enter clinical evaluation and testing.

Therapeutic use of chloroquine and hydroxychloroquine in COVID-19 and other viral infections: A narrative review

The rapidly spreading Coronavirus Disease (COVID-19) pandemic, caused by the severe acute respiratory syndrome coronavirus (SARS-CoV-2), represents an unprecedented serious challenge to the global public health community. The extremely rapid international spread of the disease with significant morbidity and mortality made finding possible therapeutic interventions a global priority. While approved specific antiviral drugs against SARS-CoV-2 are still lacking, a large number of existing drugs are being explored as a possible treatment for COVID-19 infected patients. Recent publications have re-examined the use of Chloroquine (CQ) and/or Hydroxychloroquine (HCQ) as a potential therapeutic option for these patients. In an attempt to explore the evidence that supports their use in COVID-19 patients, we comprehensively reviewed the previous studies which used CQ or HCQ as an antiviral treatment. Both CQ and HCQ demonstrated promising in vitro results, however, such data have not yet been translated into meaningful in vivo studies. While few clinical trials have suggested some beneficial effects of CQ and HCQ in COVID-19 patients, most of the reported data are still preliminary. Given the current uncertainty, it is worth being mindful of the potential risks and strictly rationalise the use of these drugs in COVID-19 patients until further high quality randomized clinical trials are available to clarify their role in the treatment or prevention of COVID-19.

New insights on the antiviral effects of chloroquine against coronavirus: what to expect for COVID-19?

Recently, a novel coronavirus (2019-nCoV), officially known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in China. Despite drastic containment measures, the spread of this virus is ongoing. SARS-CoV-2 is the aetiological agent of coronavirus disease 2019 (COVID-19) characterised by pulmonary infection in humans. The efforts of international health authorities have since focused on rapid diagnosis and isolation of patients as well as the search for therapies able to counter the most severe effects of the disease. In the absence of a known efficient therapy and because of the situation of a public-health emergency, it made sense to investigate the possible effect of chloroquine/hydroxychloroquine against SARS-CoV-2 since this molecule was previously described as a potent inhibitor of most coronaviruses, including SARS-CoV-1. Preliminary trials of chloroquine repurposing in the treatment of COVID-19 in China have been encouraging, leading to several new trials. Here we discuss the possible mechanisms of chloroquine interference with the SARS-CoV-2 replication cycle.

Structure-Based Design of Antivirals against Envelope Glycoprotein of Dengue Virus

Dengue virus (DENV) presents a significant threat to global public health with more than 500,000 hospitalizations and 25,000 deaths annually. Currently, there is no clinically approved antiviral drug to treat DENV infection. The envelope (E) glycoprotein of DENV is a promising target for drug discovery as the E protein is important for viral attachment and fusion. Understanding the structure and function of DENV E protein has led to the exploration of structure-based drug discovery of antiviral compounds and peptides against DENV infections. This review summarizes the structural information of the DENV E protein with regards to DENV attachment and fusion. The information enables the development of antiviral agents through structure-based approaches. In addition, this review compares the potency of antivirals targeting the E protein with the antivirals targeting DENV multifunctional enzymes, repurposed drugs and clinically approved antiviral drugs. None of the current DENV antiviral candidates possess potency similar to the approved antiviral drugs which indicates that more efforts and resources must be invested before an effective DENV drug materializes.

New insights on the antiviral effects of chloroquine against coronavirus: what to expect for COVID-19?

Recently, a novel coronavirus (2019-nCoV), officially known as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), emerged in China. Despite drastic containment measures, the spread of this virus is ongoing. SARS-CoV-2 is the aetiological agent of coronavirus disease 2019 (COVID-19) characterised by pulmonary infection in humans. The efforts of international health authorities have since focused on rapid diagnosis and isolation of patients as well as the search for therapies able to counter the most severe effects of the disease. In the absence of a known efficient therapy and because of the situation of a public-health emergency, it made sense to investigate the possible effect of chloroquine/hydroxychloroquine against SARS-CoV-2 since this molecule was previously described as a potent inhibitor of most coronaviruses, including SARS-CoV-1. Preliminary trials of chloroquine repurposing in the treatment of COVID-19 in China have been encouraging, leading to several new trials. Here we discuss the possible mechanisms of chloroquine interference with the SARS-CoV-2 replication cycle.

Drug repurposing for new, efficient, broad spectrum antivirals

Emerging viruses are a major threat to human health. Recent outbreaks have emphasized the urgent need for new antiviral treatments. For several pathogenic viruses, considerable efforts have focused on vaccine development. However, during epidemics infected individuals need to be treated urgently. High-throughput screening of clinically tested compounds provides a rapid means to identify undiscovered, antiviral functions for well-characterized therapeutics. Repurposed drugs can bypass part of the early cost and time needed for validation and authorization. In this review we describe recent efforts to find broad spectrum antivirals through drug repurposing. We have chosen several candidates and propose strategies to understand their mechanism of action and to determine how resistance to antivirals develops in infected cells.

Decoding the enigma of antiviral crisis: Does one target molecule regulate all?

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IL-6 class switching provides regulation over pro- and anti-inflammatory responses.

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Unregulated IL-6 trans-signaling promotes uncontrolled pro-inflammatory responses.

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ADAM-17 regulates class switching between IL-6 trans- and classical-signaling.

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Selective ADAM-17 blocking restricts overexpression of pro-inflammatory cytokines.

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ADAM-17 may be an antiviral drug target to reduce immunopathology disease severity.

Disease fatality associated with Ebola, SARS-CoV and dengue infections in humans is attributed to a cytokine storm that is triggered by excessive pro-inflammatory responses. Interleukin (IL)-6 acts as a mediator between pro- and anti-inflammatory reactivity by initiating trans- and classical-signaling, respectively. Hence, IL-6 is assumed to provide a target for a broad range of antiviral agents. Available immunosuppressive antivirals are directed to control an often exaggerated pro-inflammatory response that gives rise to complex clinical conditions such as lymphocytopenia. It is known that IL-6, via its soluble receptor (sIL-6R), initiates a pro-inflammatory response while an anti-inflammatory response is triggered by the membrane-bound IL-6 receptor (IL-6R). Future antivirals should thus aim to target the mechanism that regulates switching between IL-6 trans- and classical-signaling. In this review, we propose that the tumour necrosis factor-α converting enzyme ADAM-17 could be the master molecule involved in regulating IL-6 class switching and through this in controlling pro- and anti-inflammatory responses to viral antigenic stimuli. Therefore, ADAM-17 should be considered as a potential target molecule for novel antiviral drug discovery that would regulate host reactivity to infection and thereby limit or prevent fatal outcomes.

Blockade of dengue virus entry into myeloid cells by endocytic inhibitors in the presence or absence of antibodies

Background

Dengue is the most prevalent arthropod-borne viral human disease in tropical and subtropical regions, caused by four dengue virus (DENV) serotypes. In spite of the increasing global incidence, no specific antiviral therapy is available. Cells of the mononuclear phagocyte lineage are the main targets either for direct antibody (Ab)-independent or Ab-mediated human DENV infection, usually associated to the severe forms of disease. Since the virus entry may be a convenient therapeutic alternative, this study aimed to investigate the mode of DENV internalization into myeloid cells in the absence and presence of DENV Ab and evaluate the inhibitory activity of diverse biochemical inhibitors of endocytosis.

Methodology/principal findings

By infectivity assays and quantitative RT-PCR determinations, it was demonstrated that DENV-2 entry into U937 and K562 cells in the absence of Ab was highly inhibited by the early treatment with ammonium chloride, chlorpromazine and dynasore, but it was not affected by methyl-β-cyclodextrin, indicating that DENV-2 utilizes a low pH-dependent, clathrin- and dynamin-mediated endocytic infectious pathway for the direct entry into both human myeloid cells. To study the Ab-mediated entry of DENV, the experimental conditions for enhancement of infection were established by inoculating immune complexes formed with DENV-2 and the Ab 2H2 or 3H5. The internalization of DENV-2-2H2 or DENV-2-3H5 complexes in both myeloid cells was also dependent on acid pH and dynamin but a differential requirement of the clathrin-mediated endocytic route was observed depending on the FcγR involved in the complex uptake: the infection through FcγRII was dependent on clathrin-coated vesicles whereas the internalization pathway mediated by FcγRI was independent of clathrin. This property was not serotype-specific.

Conclusions/significance

DENV entry into myeloid cells in the absence or presence of Ab can be blocked by diverse biochemical inhibitors affecting the cellular factors involved in endocytosis. The identification of the virus-host interactions involved in virus penetration may allow the finding of host-targeted antivirals widely active against diverse pathogenic flaviviruses with similar requirements for virus entry.

Dengue is currently a widespread viral disease transmitted to human by mosquitoes, with very high prevalence in tropical and subtropical regions of América and Asia. Approximately 2.5 billion people are living in endemic areas and it is estimated that 350 million apparent and inapparent infections occur each year. There is no specific antiviral for treatment of dengue patients. On this basis, the search of antiviral agents is an urgent need. Dengue virus (DENV) entry is an attractive alternative for chemotherapeutic intervention since it represents a barrier to block the beginning of infection. We intended to evaluate the antiviral activity of diverse biochemical inhibitors of endocytosis against DENV in human myeloid cells. Results showed that DENV entry into these cells can be blocked by diverse biochemical inhibitors affecting the cellular factors involved in endocytosis such as intravesicular pH, clathrin-coated vesicles and dynamin, although the presence of non neutralizing antibodies, as can occur in secondary human infections, may alter the entry pathway under certain conditions. Then, the blockade of virus entry with host-targeted inhibitors may be a promising strategy for the development of safe antiviral agents with wide spectrum of activity against DENV and other related pathogenic flaviviruses.

Preclinical Antiviral Testing for Dengue Virus Infection in Mouse Models and Its Association with Clinical Studies

At present, there is no licensed antiviral drug against dengue virus (DENV) infection. Mouse models of DENV infection have been widely used for preclinical evaluation of antivirals. However, only in a few instances so far have the data obtained from preclinical mouse model testing been associated with data from clinical studies in humans. In this Review, we focus on the antiviral drugs targeting viral replication that have been tested in animals/humans and discuss how preclinical drug evaluation in suitable mouse/animal models may be more fruitfully used to inform early phase clinical testing.

Crimean-Congo haemorrhagic fever virus: Past, present and future insights for animal modelling and medical countermeasures

Crimean–Congo haemorrhagic fever (CCHF) is a widespread tick‐borne viral zoonosis with a case‐fatality rate ranging from 9% to 50% in humans. Although a licensed vaccine to prevent infection by the CCHF virus (CCHFV) exists, its ability to induce neutralizing antibodies is limited and its efficacy against CCHFV remains undetermined. In addition, controlling CCHF infections by eradication of the tick reservoir has been ineffective, both economically and logistically, and the treatment options for CCHF remain limited. In this review, we first critically discuss the existing animal models to evaluate therapeutics for CCHF. We then review the therapeutic options for CCHF that have been investigated in human cases, followed by investigational drugs that have been evaluated in pre‐clinical studies. We highlight the importance of understanding human prognostic factors in developing an animal model for CCHF that recapitulates hallmarks of human disease and its implication for selecting therapeutic candidates.

Blockade of dengue virus infection and viral cytotoxicity in neuronal cells in vitro and in vivo by targeting endocytic pathways

Dengue virus (DENV) infection in neuronal cells was speculated to trigger neuropathy. Herein, we determined the blockade of DENV infection by targeting endocytic pathways in vitro and in vivo. In DENV-infected mouse brains, we previously showed that viral proteins are expressed in neuronal cells around the hippocampus with accompanying neurotoxicity. DENV caused infection, including entry, double-stranded (ds)RNA replication, protein expression, and virus release, followed by cytotoxicity in the mouse neuronal Neuro-2a cell line. Pharmacologically blocking clathrin-mediated endocytosis of the DENV retarded viral replication. Targeting vacuolar-type H⁺-ATPase (V-ATPase)-based endosomal acidification effectively blocked the DENV replication process, but had no direct effect on viral translation. Blockade of the clathrin- and V-ATPase-based endocytic pathways also attenuated DENV-induced neurotoxicity. Inhibiting endosomal acidification effectively retarded DENV infection, acute viral encephalitis, and mortality. These results demonstrate that clathrin mediated endocytosis of DENV followed by endosomal acidification-dependent viral replication in neuronal cells, which can lead to neurotoxicity.

Inhibition of autophagy limits vertical transmission of Zika virus in pregnant mice

Cao et al. report a new mechanism by which Zika virus maternal-fetal transmission may occur and be limited as autophagy inhibition protects mice from vertical viral transmission. This study suggests that an autophagy-based therapeutic intervention against ZIKV may be warranted.

Zika virus (ZIKV) infection during pregnancy leads to devastating fetal outcomes, including intrauterine growth restriction and microcephaly. Greater understanding of mechanisms underlying ZIKV maternal-fetal transmission is needed to develop new therapeutic interventions. Here, we define an important role for the autophagy pathway in ZIKV vertical transmission. ZIKV infection induced autophagic activity in human trophoblasts and pharmacological inhibition limited ZIKV infectivity. Furthermore, deficiency in an essential autophagy gene, Atg16l1, in mice limited ZIKV vertical transmission and placental and fetal damage and overall improved placental and fetal outcomes. This protection was due to a placental trophoblast cell-autonomous effect of autophagic activity, not to alterations in systemic maternal ZIKV infection. Finally, an autophagy inhibitor, hydroxychloroquine, approved for use in pregnant women, attenuated placental and fetal ZIKV infection and ameliorated adverse placental and fetal outcomes. Our study reveals new insights into the mechanism of ZIKV vertical transmission and suggests that an autophagy-based therapeutic warrants possible evaluation in humans to diminish the risks of ZIKV maternal-fetal transmission.

Monitoring structural features, biocompatibility and biological efficacy of gamma-irradiated methotrexate-loaded spray-dried microparticles

In this study, biodegradable and biocompatible gamma irradiated poly-(dl-lactide-co-glycolide) (PLGA) spray-dried microparticles were prepared aiming to improve the efficacy of methotrexate (MTX). The experimental design included three formulations of microparticles containing distinct drug amount (9%, 18%, and 27% w/w) and three distinct gamma irradiation dose (15kGy, 25kGy, and 30kGy). The physicochemical and drug release properties of the microparticles supported their biocompatibility and biological efficacy studies in different cell lines. The irradiation induced slight changes in the spherical shape of the microparticles and the formation of free radicals was dependent on the drug loading. However, the amorphous character, particle size, drug loading, and drug release rate of the microparticles were preserved. The drug release data from all microparticles formulation were evaluated by using four drug kinetic models and by comparison of their similarity factor (f₂). The gamma irradiation did not induce changes in the biocompatibility of PLGA microparticles and in the biological activity of the MTX-loaded microparticles. Finally, the spray-dried MTX-loaded PLGA microparticles enhanced the efficacy of the drug in the human cervical cancer cells (SiHa cell line). This study demonstrated the feasibility of the gamma irradiated spray dried PLGA microparticles for prolonged release of MTX, supporting a promising antitumor-drug delivery system for parenteral (subcutaneous) or pulmonary use.

Targeting endosomal acidification by chloroquine analogs as a promising strategy for the treatment of emerging viral diseases

Emerging viruses such as HIV, dengue, influenza A, SARS coronavirus, Ebola, and other viruses pose a significant threat to human health. Majority of these viruses are responsible for the outbreaks of pathogenic lethal infections. To date, there are no effective therapeutic strategies available for the prophylaxis and treatment of these infections. Chloroquine analogs have been used for decades as the primary and most successful drugs against malaria. Concomitant with the emergence of chloroquine‐resistant Plasmodium strains and a subsequent decrease in the use as antimalarial drugs, other applications of the analogs have been investigated. Since the analogs have interesting biochemical properties, these drugs are found to be effective against a wide variety of viral infections. As antiviral action, the analogs have been shown to inhibit acidification of endosome during the events of replication and infection. Moreover, immunomodulatory effects of analogs have been beneficial to patients with severe inflammatory complications of several viral diseases. Interestingly, one of the successful targeting strategies is the inhibition of HIV replication by the analogs in vitro which are being tested in several clinical trials. This review focuses on the potentialities of chloroquine analogs for the treatment of endosomal low pH dependent emerging viral diseases.

Chloroquine inhibited Ebola virus replication in vitro but failed to protect against infection and disease in the in vivo guinea pig model

Ebola virus (EBOV) is highly pathogenic, with a predisposition to cause outbreaks in human populations accompanied by significant mortality. Owing to the lack of approved therapies, screening programmes of potentially efficacious drugs have been undertaken. One of these studies has demonstrated the possible utility of chloroquine against EBOV using pseudotyped assays. In mouse models of EBOV disease there are conflicting reports of the therapeutic effects of chloroquine. There are currently no reports of its efficacy using the larger and more stringent guinea pig model of infection. In this study we have shown that replication of live EBOV is impaired by chloroquine in vitro. However, no protective effects were observed in vivo when EBOV-infected guinea pigs were treated with chloroquine. These results advocate that chloroquine should not be considered as a treatment strategy for EBOV.

Zika virus infection-the next wave after dengue?

Zika virus was initially discovered in east Africa about 70 years ago and remained a neglected arboviral disease in Africa and Southeast Asia. The virus first came into the limelight in 2007 when it caused an outbreak in Micronesia. In the ensuing decade, it spread widely in other Pacific islands, after which its incursion into Brazil in 2015 led to a widespread epidemic in Latin America. In most infected patients the disease is relatively benign. Serious complications include Guillain-Barré syndrome and congenital infection which may lead to microcephaly and maculopathy. Aedes mosquitoes are the main vectors, in particular, Ae. aegypti. Ae. albopictus is another potential vector. Since the competent mosquito vectors are highly prevalent in most tropical and subtropical countries, introduction of the virus to these areas could readily result in endemic transmission of the disease. The priorities of control include reinforcing education of travellers to and residents of endemic areas, preventing further local transmission by vectors, and an integrated vector management programme. The container habitats of Ae. aegypti and Ae. albopictus means engagement of the community and citizens is of utmost importance to the success of vector control.