Synthesis of LAVR-289, a new [(Z)-3-(acetoxymethyl)-4-(2,4-diaminopyrimidin-6-yl)oxy-but-2-enyl]phosphonic acid prodrug with pronounced antiviral activity against DNA viruses.

New acyclic pyrimidine nucleoside phosphonate prodrugs with a 4-(2,4-diaminopyrimidin-6-yl)oxy-but-2-enyl]phosphonic acid skeleton (O-DAPy nucleobase) were prepared through a convergent synthesis by olefin cross-metathesis as the key step. Several acyclic nucleoside 4-(2,4-diaminopyrimidin-6-yl)oxy-but-2-enyl]phosphonic acid prodrug exhibited in vitro antiviral activity in submicromolar or nanomolar range against varicella zoster virus (VZV), human cytomegalovirus (HCMV), human herpes virus type 1 (HSV-1) and type 2 (HSV-2), and vaccinia virus (VV), with good selective index (SI). Among them, the analogue 9c (LAVR-289) proved markedly inhibitory against VZV wild-type (TK+) (EC50 0.0035 µM, SI 740) and for thymidine kinase VZV deficient strains (EC50 0.018 µM, SI 145), with a low morphological toxicity in cell culture at 100 µM and acceptable cytostatic activity resulting in excellent selectivity. Compound 9c exhibited antiviral activity against HCMV (EC50 0.021 µM) and VV (EC50 0.050 µM), as well as against HSV-1 (TK-) (EC50 0.0085 µM). Finally, LAVR-289 (9c) deserves further (pre)clinical investigations as a potent candidate broad-spectrum anti-herpesvirus drug.

Broad-Spectrum Antiviral Activity of the Amphibian Antimicrobial Peptide Temporin L and Its Analogs.

The COVID-19 pandemic has evidenced the urgent need for the discovery of broad-spectrum antiviral therapies that could be deployed in the case of future emergence of novel viral threats, as well as to back up current therapeutic options in the case of drug resistance development. Most current antivirals are directed to inhibit specific viruses since these therapeutic molecules are designed to act on a specific viral target with the objective of interfering with a precise step in the replication cycle. Therefore, antimicrobial peptides (AMPs) have been identified as promising antiviral agents that could help to overcome this limitation and provide compounds able to act on more than a single viral family. We evaluated the antiviral activity of an amphibian peptide known for its strong antimicrobial activity against both Gram-positive and Gram-negative bacteria, namely Temporin L (TL). Previous studies have revealed that TL is endowed with widespread antimicrobial activity and possesses marked haemolytic activity. Therefore, we analyzed TL and a previously identified TL derivative (Pro3, DLeu9 TL, where glutamine at position 3 is replaced with proline, and the D-Leucine enantiomer is present at position 9) as well as its analogs, for their activity against a wide panel of viruses comprising enveloped, naked, DNA and RNA viruses. We report significant inhibition activity against herpesviruses, paramyxoviruses, influenza virus and coronaviruses, including SARS-CoV-2. Moreover, we further modified our best candidate by lipidation and demonstrated a highly reduced cytotoxicity with improved antiviral effect. Our results show a potent and selective antiviral activity of TL peptides, indicating that the novel lipidated temporin-based antiviral agents could prove to be useful additions to current drugs in combatting rising drug resistance and epidemic/pandemic emergencies.

The Broad-Spectrum Antiviral Potential of the Amphibian Peptide AR-23.

Viral infections represent a serious threat to the world population and are becoming more frequent. The search and identification of broad-spectrum antiviral molecules is necessary to ensure new therapeutic options, since there is a limited availability of effective antiviral drugs able to eradicate viral infections, and consequently due to the increase of strains that are resistant to the most used drugs. Recently, several studies on antimicrobial peptides identified them as promising antiviral agents. In detail, amphibian skin secretions serve as a rich source of natural antimicrobial peptides. Their antibacterial and antifungal activities have been widely reported, but their exploitation as potential antiviral agents have yet to be fully investigated. In the present study, the antiviral activity of the peptide derived from the secretion of Rana tagoi, named AR-23, was evaluated against both DNA and RNA viruses, with or without envelope. Different assays were performed to identify in which step of the infectious cycle the peptide could act. AR-23 exhibited a greater inhibitory activity in the early stages of infection against both DNA (HSV-1) and RNA (MeV, HPIV-2, HCoV-229E, and SARS-CoV-2) enveloped viruses and, on the contrary, it was inactive against naked viruses (PV-1). Altogether, the results indicated AR-23 as a peptide with potential therapeutic effects against a wide variety of human viruses.

NPC1-regulated dynamic of clathrin-coated pits is essential for viral entry.

Viruses utilize cellular lipids and manipulate host lipid metabolism to ensure their replication and spread. Therefore, the identification of lipids and metabolic pathways that are suitable targets for antiviral development is crucial. Using a library of compounds targeting host lipid metabolic factors and testing them for their ability to block pseudorabies virus (PRV) and vesicular stomatitis virus (VSV) infection, we found that U18666A, a specific inhibitor of Niemann-Pick C1 (NPC1), is highly potent in suppressing the entry of diverse viruses including pseudotyped severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). NPC1 deficiency markedly attenuates viral growth by decreasing cholesterol abundance in the plasma membrane, thereby inhibiting the dynamics of clathrin-coated pits (CCPs), which are indispensable for clathrin-mediated endocytosis. Significantly, exogenous cholesterol can complement the dynamics of CCPs, leading to efficient viral entry and infectivity. Administration of U18666A improves the survival and pathology of PRV- and influenza A virus-infected mice. Thus, our studies demonstrate a unique mechanism by which NPC1 inhibition achieves broad antiviral activity, indicating a potential new therapeutic strategy against SARS-CoV-2, as well as other emerging viruses.

In vitro effects of bufotenine against RNA and DNA viruses.

Bufotenine, an alkaloid that can be found in plant extracts and skin secretions of amphibians, is reported to have potential antiviral activity. The present study evaluated the antiviral activity of bufotenine against different genetic lineages of rabies virus (RABV, a single-stranded, negative-sense RNA virus), canine coronavirus (CCoV, a positive-sense RNA virus) and two double-stranded DNA viruses (two strains of herpes simplex virus type 1/HSV-1 [KOS and the acyclovir-resistant HSV-1 strain 29R] and canine adenovirus 2, CAV-2). The maximal non-toxic bufotenine concentrations in Vero and BHK-21 cells were determined by MTT assays. The antiviral activity of bufotenine against each virus was assessed by examination of reductions in infectious virus titres and plaque assays. All experiments were performed with and without bufotenine, and the results were compared. Bufotenine demonstrated significant RABV inhibitory activity. No antiviral action was observed against CCoV, CAV-2 or HSV-1. These findings indicate that the antiviral activity of bufotenine is somewhat linked to the particular infectious dose used and the genetic lineage of the virus, although the mechanisms of its effects remain undetermined.

Teriflunomide Inhibits JCPyV Infection and Spread in Glial Cells and Choroid Plexus Epithelial Cells.

Several classes of immunomodulators are used for treating relapsing-remitting multiple sclerosis (RRMS). Most of these disease-modifying therapies, except teriflunomide, carry the risk of progressive multifocal leukoencephalopathy (PML), a severely debilitating, often fatal virus-induced demyelinating disease. Because teriflunomide has been shown to have antiviral activity against DNA viruses, we investigated whether treatment of cells with teriflunomide inhibits infection and spread of JC polyomavirus (JCPyV), the causative agent of PML. Treatment of choroid plexus epithelial cells and astrocytes with teriflunomide reduced JCPyV infection and spread. We also used droplet digital PCR to quantify JCPyV DNA associated with extracellular vesicles isolated from RRMS patients. We detected JCPyV DNA in all patients with confirmed PML diagnosis (n = 2), and in six natalizumab-treated (n = 12), two teriflunomide-treated (n = 7), and two nonimmunomodulated (n = 2) patients. Of the 21 patients, 12 (57%) had detectable JCPyV in either plasma or serum. CSF was uniformly negative for JCPyV. Isolation of extracellular vesicles did not increase the level of detection of JCPyV DNA versus bulk unprocessed biofluid. Overall, our study demonstrated an effect of teriflunomide inhibiting JCPyV infection and spread in glial and choroid plexus epithelial cells. Larger studies using patient samples are needed to correlate these in vitro findings with patient data.

Novel betulin dicarboxylic acid ester derivatives as potent antiviral agents: Design, synthesis, biological evaluation, structure-activity relationship and in-silico study.

The search for new methods of antiviral therapy is primarily focused on the use of substances of natural origin. In this context, a triterpene compound, betulin 1, proved to be a good starting point for derivatization. Thirty-eight betulin acid ester derivatives were synthetized, characterized, and tested against DNA and RNA viruses. Several compounds exhibited 4- to 11-fold better activity against Enterovirus E (compound 5 EC50: 10.3 µM) and 3- to 6-fold better activity against Human alphaherpesvirus 1 (HHV-1; compound 3c EC50: 17.2 µM). Time-of-addition experiments showed that most of the active compounds acted in the later steps of the virus replication cycle (e.g., nucleic acid/protein synthesis). Further in-silico analysis confirmed in-vitro data and demonstrated that interactions between HHV-1 DNA polymerase and the most active compound, 3c, were more stable than interactions with the parent non-active betulin 1.

From Recoding to Peptides for MHC Class I Immune Display: Enriching Viral Expression, Virus Vulnerability and Virus Evasion.

Many viruses, especially RNA viruses, utilize programmed ribosomal frameshifting and/or stop codon readthrough in their expression, and in the decoding of a few a UGA is dynamically redefined to specify selenocysteine. This recoding can effectively increase viral coding capacity and generate a set ratio of products with the same N-terminal domain(s) but different C-terminal domains. Recoding can also be regulatory or generate a product with the non-universal 21st directly encoded amino acid. Selection for translation speed in the expression of many viruses at the expense of fidelity creates host immune defensive opportunities. In contrast to host opportunism, certain viruses, including some persistent viruses, utilize recoding or adventitious frameshifting as part of their strategy to evade an immune response or specific drugs. Several instances of recoding in small intensively studied viruses escaped detection for many years and their identification resolved dilemmas. The fundamental importance of ribosome ratcheting is consistent with the initial strong view of invariant triplet decoding which however did not foresee the possibility of transitory anticodon:codon dissociation. Deep level dynamics and structural understanding of recoding is underway, and a high level structure relevant to the frameshifting required for expression of the SARS CoV-2 genome has just been determined.

Evaluation of A-azepano-triterpenoids and related derivatives as antimicrobial and antiviral agents.

A series of semisynthetic triterpenoids with A-ring azepano- and A-seco-fragments as well as hydrazido/hydrazono-substituents at C3 and C28 has been synthesized and evaluated for antimicrobial activity against key ESKAPE pathogens and DNA viruses (HSV-1, HCMV, HPV-11). It was found that azepanouvaol 8, 3-amino-3,4-seco-4(23)-en derivatives of uvaol 21 and glycyrrhetol-dien 22 as well as azepano-glycyrrhetol-tosylate 32 showed strong antimicrobial activities against MRSA with MIC ≤ 0.15 µM that exceeds the effect of antibiotic vancomycin. Azepanobetulinic acid cyclohexyl amide 4 exhibited significant bacteriostatic effect against MRSA (MIC ≤ 0.15 µM) with low cytotoxicity to HEK-293 even at a maximum tested concentration of >20 µM (selectivity index SI 133) and may be considered a noncytotoxic anti-MRSA agent. Azepanobetulin 1, azepanouvaol 8, and azepano-glycyrrhetol 15 showed high potency towards HCMV (EC50 0.15; 0.11; 0.11 µM) with selectivity indexes SI50 115; 136; 172, respectively. The docking studies suggest the possible interactions of the leading compounds with the molecular targets.

Antiviral Activity Exerted by Natural Products against Human Viruses.

Viral infections are responsible for several chronic and acute diseases in both humans and animals. Despite the incredible progress in human medicine, several viral diseases, such as acquired immunodeficiency syndrome, respiratory syndromes, and hepatitis, are still associated with high morbidity and mortality rates in humans. Natural products from plants or other organisms are a rich source of structurally novel chemical compounds including antivirals. Indeed, in traditional medicine, many pathological conditions have been treated using plant-derived medicines. Thus, the identification of novel alternative antiviral agents is of critical importance. In this review, we summarize novel phytochemicals with antiviral activity against human viruses and their potential application in treating or preventing viral disease.

Phenoxazine nucleoside derivatives with a multiple activity against RNA and DNA viruses.

Emerging and re-emerging viruses periodically cause outbreaks and epidemics all over the world, eventually leading to global events such as the current pandemic of the novel SARS-CoV-2 coronavirus infection COVID-19. Therefore, an urgent need for novel antivirals is crystal clear. Here we present the synthesis and evaluation of an antiviral activity of phenoxazine-based nucleoside analogs divided into three groups: (1) 8-alkoxy-substituted, (2) acyclic, and (3) carbocyclic. The antiviral activity was assessed against a structurally and phylogenetically diverse panel of RNA and DNA viruses from 25 species. Four compounds (11a-c, 12c) inhibited 4 DNA/RNA viruses with EC50 ≤ 20 µM. Toxicity of the compounds for the cell lines used for virus cultivation was negligible in most cases. In addition, previously reported and newly synthesized phenoxazine derivatives were evaluated against SARS-CoV-2, and some of them showed promising inhibition of reproduction with EC50 values in low micromolar range, although accompanied by commensurate cytotoxicity.

Aptamers for Anti-Viral Therapeutics and Diagnostics.

Viral infections cause a host of fatal diseases and seriously affect every form of life from bacteria to humans. Although most viral infections can receive appropriate treatment thereby limiting damage to life and livelihood with modern medicine and early diagnosis, new types of viral infections are continuously emerging that need to be properly and timely treated. As time is the most important factor in the progress of many deadly viral diseases, early detection becomes of paramount importance for effective treatment. Aptamers are small oligonucleotide molecules made by the systematic evolution of ligands by exponential enrichment (SELEX). Aptamers are characterized by being able to specifically bind to a target, much like antibodies. However, unlike antibodies, aptamers are easily synthesized, modified, and are able to target a wider range of substances, including proteins and carbohydrates. With these advantages in mind, many studies on aptamer-based viral diagnosis and treatments are currently in progress. The use of aptamers for viral diagnosis requires a system that recognizes the binding of viral molecules to aptamers in samples of blood, serum, plasma, or in virus-infected cells. From a therapeutic perspective, aptamers target viral particles or host cell receptors to prevent the interaction between the virus and host cells or target intracellular viral proteins to interrupt the life cycle of the virus within infected cells. In this paper, we review recent attempts to use aptamers for the diagnosis and treatment of various viral infections.

Curcumin as an Antiviral Agent.

Curcumin, the primary curcuminoid compound found in turmeric spice, has shown broad activity as an antimicrobial agent, limiting the replication of many different fungi, bacteria and viruses. In this review, we summarize recent studies supporting the development of curcumin and its derivatives as broad-spectrum antiviral agents.

Nucleoside analogs assisted with Chinese compound prescription in treating hepatic fibrosis of chronic hepatitis B patients: A protocol of systematic review and meta-analysis.

BACKGROUND: Chronic hepatitis B is often complicated with different degrees of hepatic fibrosis, which affects the quality of life. Nucleoside analogs are recommended by almost all guidelines in the world for the treatment of chronic hepatitis B. At present, there is no specific and effective chemical and biological agents for hepatic fibrosis. In China, Chinese compound prescription combined with nucleoside analogs have been used to treat hepatic fibrosis of chronic hepatitis B patients in more and more cases, and good results have been achieved. Several Chinese compound prescriptions that have been made into proprietary Chinese medicine for the convenience of use. This article aims to systematically evaluate the efficacy and safety of Chinese medicine compounds assisting nucleoside analogs in the treatment of hepatic fibrosis in chronic hepatitis B patients. METHOD: The following databases will be searched from their inception to September 2019: PubMed, EMBASE, EBSCOhost, The Cochrane Library, China National Knowledge Infrastructure (CNKI), Chinese Biomedical literature Database (CBM), VIP Database, Wanfang Database. Languages are limited to Chinese and English. The study includes randomized controlled trials using Chinese compound prescription combined with entecavir and Chinese compound prescription combined with tenofovir disoproxil fumarate to treat hepatic fibrosis of chronic hepatitis B patients. The primary outcomes including effective rate and biochemical parameters (levels of hyaluronic acid, laminin, pre-type-III collagen and type IV collagen will be tested. Additional outcomes include liver function indexes (levels of alanine aminotransferase, aspartate aminotransferase, total bilirubin) and levels of hepatitis B virus DNA. Stata14.0 software will be used for meta-analysis. RESULT: The efficacy and safety of Chinese compound prescriptions assisting nucleoside analogs for hepatic fibrosis of chronic hepatitis B patients will be assessed from the effective rate, biochemical parameters, liver function indexes, and levels of hepatitis B virus DNA. CONCLUSION: The conclusion of this study will be used to evaluate the efficacy and safety of Chinese compound prescriptions assisting nucleoside analogs in the treatment of hepatic fibrosis of chronic hepatitis B patients, as well as the adjuvant effectiveness of Chinese compound prescriptions in combined therapy. PROSPERO REGISTRATION NUMBER: CRD42020156859.

Quinoxaline Derivatives as Antiviral Agents: A Systematic Review.

BACKGROUND: In recent decades, several viruses have jumped from animals to humans, triggering sizable outbreaks. The current unprecedent outbreak SARS-COV-2 is prompting a search for new cost-effective therapies to combat this deadly pathogen. Suitably functionalized polysubstituted quinoxalines show very interesting biological properties (antiviral, anticancer, and antileishmanial), ensuring them a bright future in medicinal chemistry. OBJECTIVES: Focusing on the promising development of new quinoxaline derivatives as antiviral drugs, this review forms part of our program on the anti-infectious activity of quinoxaline derivatives. METHODS: Study compiles and discusses recently published studies concerning the therapeutic potential of the antiviral activity of quinoxaline derivatives, covering the literature between 2010 and 2020. RESULTS: A final total of 20 studies included in this review. CONCLUSIONS: This review points to a growing interest in the development of compounds bearing a quinoxaline moiety for antiviral treatment. This promising moiety with different molecular targets warrants further investigation, which may well yield even more encouraging results regarding this scaffold.

Ivermectin: a systematic review from antiviral effects to COVID-19 complementary regimen.

Ivermectin proposes many potentials effects to treat a range of diseases, with its antimicrobial, antiviral, and anti-cancer properties as a wonder drug. It is highly effective against many microorganisms including some viruses. In this comprehensive systematic review, antiviral effects of ivermectin are summarized including in vitro and in vivo studies over the past 50 years. Several studies reported antiviral effects of ivermectin on RNA viruses such as Zika, dengue, yellow fever, West Nile, Hendra, Newcastle, Venezuelan equine encephalitis, chikungunya, Semliki Forest, Sindbis, Avian influenza A, Porcine Reproductive and Respiratory Syndrome, Human immunodeficiency virus type 1, and severe acute respiratory syndrome coronavirus 2. Furthermore, there are some studies showing antiviral effects of ivermectin against DNA viruses such as Equine herpes type 1, BK polyomavirus, pseudorabies, porcine circovirus 2, and bovine herpesvirus 1. Ivermectin plays a role in several biological mechanisms, therefore it could serve as a potential candidate in the treatment of a wide range of viruses including COVID-19 as well as other types of positive-sense single-stranded RNA viruses. In vivo studies of animal models revealed a broad range of antiviral effects of ivermectin, however, clinical trials are necessary to appraise the potential efficacy of ivermectin in clinical setting.

Epigenetic and epitranscriptomic regulation of viral replication.

Eukaryotic gene expression is regulated not only by genomic enhancers and promoters, but also by covalent modifications added to both chromatin and RNAs. Whereas cellular gene expression may be either enhanced or inhibited by specific epigenetic modifications deposited on histones (in particular, histone H3), these epigenetic modifications can also repress viral gene expression, potentially functioning as a potent antiviral innate immune response in DNA virus-infected cells. However, viruses have evolved countermeasures that prevent the epigenetic silencing of their genes during lytic replication, and they can also take advantage of epigenetic silencing to establish latent infections. By contrast, the various covalent modifications added to RNAs, termed epitranscriptomic modifications, can positively regulate mRNA translation and/or stability, and both DNA and RNA viruses have evolved to utilize epitranscriptomic modifications as a means to maximize viral gene expression. As a consequence, both chromatin and RNA modifications could serve as novel targets for the development of antivirals. In this Review, we discuss how host epigenetic and epitranscriptomic processes regulate viral gene expression at the levels of chromatin and RNA function, respectively, and explore how viruses modify, avoid or utilize these processes in order to regulate viral gene expression.

An overview of functional nanoparticles as novel emerging antiviral therapeutic agents.

Research on highly effective antiviral drugs is essential for preventing the spread of infections and reducing losses. Recently, many functional nanoparticles have been shown to possess remarkable antiviral ability, such as quantum dots, gold and silver nanoparticles, nanoclusters, carbon dots, graphene oxide, silicon materials, polymers and dendrimers. Despite their difference in antiviral mechanism and inhibition efficacy, these functional nanoparticles-based structures have unique features as potential antiviral candidates. In this topical review, we highlight the antiviral efficacy and mechanism of these nanoparticles. Specifically, we introduce various methods for analyzing the viricidal activity of functional nanoparticles and the latest advances in antiviral functional nanoparticles. Furthermore, we systematically describe the advantages and disadvantages of these functional nanoparticles in viricidal applications. Finally, we discuss the challenges and prospects of antiviral nanostructures. This topic review covers 132 papers and will enrich our knowledge about the antiviral efficacy and mechanism of various functional nanoparticles.

The Comparative Analysis of Antiviral Activity of Native and Modified Fucoidans from Brown Algae Fucus evanescens In Vitro and In Vivo.

The enzymatic depolymerization of fucoidans from brown algae allowed the production of their standardized derivatives with different biological activities. This work aimed to compare the antiviral activities of native (FeF) and modified with enzyme (FeHMP) fucoidans from F. evanescens. The cytotoxicity and antiviral activities of the FeF and FeHMP against herpes viruses (HSV-1, HSV-2), enterovirus (ECHO-1), and human immunodeficiency virus (HIV-1) in Vero and human MT-4 cell lines were examined by methylthiazolyltetrazolium bromide (MTT) and cytopathic effect (CPE) reduction assays, respectively. The efficacy of fucoidans in vivo was evaluated in the outbred mice model of vaginitis caused by HSV-2. We have shown that both FeF and FeHMP significantly inhibited virus-induced CPE in vitro and were more effective against HSV. FeF exhibited antiviral activity against HSV-2 with a selective index (SI) > 40, and FeHMP with SI ˃ 20, when they were added before virus infection or at the early stages of the HSV-2 lifecycle. Furthermore, in vivo studies showed that after intraperitoneal administration (10 mg/kg), both FeF and FeHMP protected mice from lethal intravaginal HSV-2 infection to approximately the same degree (44-56%). Thus, FeF and FeHMP have comparable potency against several DNA and RNA viruses, allowing us to consider the studied fucoidans as promising broad-spectrum antivirals.

Brincidofovir: understanding its unique profile and potential role against adenovirus and other viral infections.

Brincidofovir (BCV) is a lipid conjugate of cidofovir with good oral bioavailability, enabling optimal intracellular levels of the active drug. Lower rates of nephrotoxicity and myelotoxicity make it a favorable alternative. Despite a greater safety profile among pediatric hematopoietic cell transplant recipients, the oral formulation has been associated with increased gastrointestinal toxicity in adult hematopoietic cell transplant recipients. Oral BCV continues to be developed as a countermeasure against smallpox, while a potentially safer intravenous preparation has been out licensed to another company. BCV has demonstrated great in vitro potency against double-stranded DNA viruses, especially adenovirus. Because of its importance for immunocompromised patients, this review aims to evaluate BCV's clinical and safety profile to support its continued development.