Non-nucleoside inhibitors of the measles virus RNA-dependent RNA polymerase: synthesis, structure-activity relationships, and pharmacokinetics

N-Heterocycles as Promising Antiviral Agents: A Comprehensive Overview

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

Helical peptides with disordered regions for measles viruses provide new generalized insights into fusion inhibitors

Despite effective vaccines, measles virus (MeV) outbreaks occur sporadically. Therefore, developing anti-MeV agents remains important for suppressing MeV infections. We previously designed peptide-based MeV fusion inhibitors, M1 and M2, that target MeV class I fusion protein (F protein). Here, we developed a novel fusion inhibitor, MEK35, that exerts potent activity against M1/M2-resistant MeV variants. Comparing MEK35 to M1 derivatives revealed that combining disordered and helical elements was essential for overcoming M1/M2 resistance. Moreover, we propose a three-step antiviral process for peptide-based fusion inhibitors: (i) disordered peptides interact with F protein; (ii) the peptides adopt a partial helical conformation and bind to F protein through hydrophobic interactions; and (iii) subsequent interactions involving the disordered region of the peptides afford a peptide-F protein with a high-affinity peptide-F protein interaction. An M1-resistant substitution blocks the second step. These results should aid the development of novel viral fusion inhibitors targeting class I F protein.

Application of Chiral Piperidine Scaffolds in Drug Design

Chiral piperidine scaffolds are prevalent as the common cores of a large number of active pharmaceuticals in medical chemistry. This review outlined the diversity of chiral piperidine scaffolds in recently approved drugs, and also covers the scaffolds in leads and drug candidates. The significance of chiral piperidine scaffolds in drug design is also discussed in this article. With the introduction of chiral piperidine scaffolds into small molecules, the exploration of drug-like molecules can be benefitted from the following aspect: (1) modulating the physicochemical properties; (2) enhancing the biological activities and selectivity; (3) improving pharmacokinetic properties; and (4) reducing the cardiac hERG toxicity. Given above, chiral piperidine-based discovery of small molecules will be a promising strategy to enrich our molecules' library to fight against diseases.

Repurposing an In Vitro Measles Virus Dissemination Assay for Screening of Antiviral Compounds

Measles virus (MV) is a highly contagious respiratory virus responsible for outbreaks associated with significant morbidity and mortality among children and young adults. Although safe and effective measles vaccines are available, the COVID-19 pandemic has resulted in vaccination coverage gaps that may lead to the resurgence of measles when restrictions are lifted. This puts individuals who cannot be vaccinated, such as young infants and immunocompromised individuals, at risk. Therapeutic interventions are complicated by the long incubation time of measles, resulting in a narrow treatment window. At present, the only available WHO-advised option is treatment with intravenous immunoglobulins, although this is not approved as standard of care. Antivirals against measles may contribute to intervention strategies to limit the impact of future outbreaks. Here, we review previously described antivirals and antiviral assays, evaluate the antiviral efficacy of a number of compounds to inhibit MV dissemination in vitro, and discuss potential application in specific target populations. We conclude that broadly reactive antivirals could strengthen existing intervention strategies to limit the impact of measles outbreaks.

Highly Potent Host-Specific Small-Molecule Inhibitor of Paramyxovirus and Pneumovirus Replication with High Resistance Barrier

Multiple enveloped RNA viruses of the family Paramyxoviridae and Pneumoviridae, like measles virus (MeV), Nipah virus (NiV), canine distemper virus (CDV), or respiratory syncytial virus (RSV), are of high clinical relevance. Each year a huge number of lives are lost as a result of these viral infections. Worldwide, MeV infection alone is responsible for over a hundred thousand deaths each year despite available vaccine. Therefore, there is an urgent need for treatment options to counteract these viral infections. The development of antiviral drugs in general stands as a huge challenge due to the rapid emergence of viral escape mutants. Here, we disclose the discovery of a small-molecule antiviral, compound 1 (ZHAWOC9045), active against several pneumo-/paramyxoviruses, including MeV, NiV, CDV, RSV, and parainfluenza virus type 5 (PIV-5). A series of mechanistic characterizations revealed that compound 1 targets a host factor which is indispensable for viral genome replication. Drug resistance profiling against a paramyxovirus model (CDV) demonstrated no detectable adaptation despite prolonged time of investigation, thereby mitigating the rapid emergence of escape variants. Furthermore, a thorough structure-activity relationship analysis of compound 1 led to the invention of 100-times-more potent-derivatives, e.g., compound 2 (ZHAWOC21026). Collectively, we present in this study an attractive host-directed pneumoviral/paramyxoviral replication inhibitor with potential therapeutic application.

Small-molecule polymerase inhibitor protects non-human primates from measles and reduces shedding

Measles virus (MeV) is a highly contagious pathogen that enters the human host via the respiratory route. Besides acute pathologies including fever, cough and the characteristic measles rash, the infection of lymphocytes leads to substantial immunosuppression that can exacerbate the outcome of infections with additional pathogens. Despite the availability of effective vaccine prophylaxis, measles outbreaks continue to occur worldwide. We demonstrate that prophylactic and post-exposure therapeutic treatment with an orally bioavailable small-molecule polymerase inhibitor, ERDRP-0519, prevents measles disease in squirrel monkeys (Saimiri sciureus). Treatment initiation at the onset of clinical signs reduced virus shedding, which may support outbreak control. Results show that this clinical candidate has the potential to alleviate clinical measles and augment measles virus eradication.

Measles virus is highly contagious and outbreaks occur worldwide. Here the authors show that the orally bioavailable small-molecule polymerase inhibitor ERDRP-0519 prevents measles disease in squirrel monkeys and reduces virus shedding.

Recent advances in the discovery of potent RNA-dependent RNA-polymerase (RdRp) inhibitors targeting viruses

WHO has declared COVID-19 a pandemic, which has affected the whole world and has caused unprecedented social and economic disruption. Since the emergence of the disease, several druggable targets have been suggested including 3-chymotrypsin-like protease (3CLpro), spike, RNA-dependent RNA polymerase (RdRp), and the papain-like protease (PLpro) computational approach. From the beginning, viral replication has been the main focus for any antiviral drug development for viral diseases, including HCV, influenza virus, zika virus, norovirus, measles, dengue virus, and coronaviruses. This review lists the nucleoside, nucleotide, and non-nucleoside RdRp inhibitor analogues of various viral diseases that may be evaluated for drug development to treat COVID-19.

Therapeutic targeting of measles virus polymerase with ERDRP-0519 suppresses all RNA synthesis activity

Morbilliviruses, such as measles virus (MeV) and canine distemper virus (CDV), are highly infectious members of the paramyxovirus family. MeV is responsible for major morbidity and mortality in non-vaccinated populations. ERDRP-0519, a pan-morbillivirus small molecule inhibitor for the treatment of measles, targets the morbillivirus RNA-dependent RNA-polymerase (RdRP) complex and displayed unparalleled oral efficacy against lethal infection of ferrets with CDV, an established surrogate model for human measles. Resistance profiling identified the L subunit of the RdRP, which harbors all enzymatic activity of the polymerase complex, as the molecular target of inhibition. Here, we examined binding characteristics, physical docking site, and the molecular mechanism of action of ERDRP-0519 through label-free biolayer interferometry, photoaffinity cross-linking, and in vitro RdRP assays using purified MeV RdRP complexes and synthetic templates. Results demonstrate that unlike all other mononegavirus small molecule inhibitors identified to date, ERDRP-0519 inhibits all phosphodiester bond formation in both de novo initiation of RNA synthesis at the promoter and RNA elongation by a committed polymerase complex. Photocrosslinking and resistance profiling-informed ligand docking revealed that this unprecedented mechanism of action of ERDRP-0519 is due to simultaneous engagement of the L protein polyribonucleotidyl transferase (PRNTase)-like domain and the flexible intrusion loop by the compound, pharmacologically locking the polymerase in pre-initiation conformation. This study informs selection of ERDRP-0519 as clinical candidate for measles therapy and identifies a previously unrecognized druggable site in mononegavirus L polymerase proteins that can silence all synthesis of viral RNA.

The mononegavirus order contains major established and recently emerged human pathogens. Despite the threat to human health, antiviral therapeutics directed against this order remain understudied. The mononegavirus polymerase complex represents a promising drug target due to its central importance for both virus replication and viral mitigation of the innate host antiviral response. In this study, we have mechanistically characterized a clinical candidate small-molecule MeV polymerase inhibitor. The compound blocked all phosphodiester bond formation activity, a unique mechanism of action unlike all other known mononegavirus polymerase inhibitors. Photocrosslinking-based target site mapping demonstrated that this class-defining prototype inhibitor stabilizes a pre-initiation conformation of the viral polymerase complex that sterically cannot accommodate template RNA. Function-equivalent druggable sites exist in all mononegavirus polymerases. In addition to its direct anti-MeV impact, the insight gained in this study can therefore serve as a blueprint for indication spectrum expansion through structure-informed scaffold engineering or targeted drug discovery.

Antiviral Drug Targets of Single-Stranded RNA Viruses Causing Chronic Human Diseases

Ribonucleic acid (RNA) viruses associated with chronic diseases in humans are major threats to public health causing high mortality globally. The high mutation rate of RNA viruses helps them to escape the immune response and also is responsible for the development of drug resistance. Chronic infections caused by human immunodeficiency virus (HIV) and hepatitis viruses (HBV and HCV) lead to acquired immunodeficiency syndrome (AIDS) and hepatocellular carcinoma respectively, which are one of the major causes of human deaths. Effective preventative measures to limit chronic and re-emerging viral infections are absolutely necessary. Each class of antiviral agents targets a specific stage in the viral life cycle and inhibits them from its development and proliferation. Most often, antiviral drugs target a specific viral protein, therefore only a few broad-spectrum drugs are available. This review will be focused on the selected viral target proteins of pathogenic viruses containing single-stranded (ss) RNA genome that causes chronic infections in humans (e.g. HIV, HCV, Flaviviruses). In the recent past, an exponential increase in the number of available three-dimensional protein structures (>150000 in Protein Data Bank), allowed us to better understand the molecular mechanism of action of protein targets and antivirals. Advancements in the in silico approaches paved the way to design and develop several novels, highly specific small-molecule inhibitors targeting the viral proteins.

Advances in Antiviral Therapy for Subacute Sclerosing Panencephalitis

Subacute sclerosing panencephalitis (SSPE) is a late-onset, intractable, and fatal viral disease caused by persistent infection of the central nervous system by a mutant strain of the measles virus. Ribavirin intracerebroventricular therapy has already been administered to several SSPE patients in Japan based on fundamental and clinical research findings from our group, with positive therapeutic effects reported in some patients. However, the efficacy of this treatment approach has not been unequivocally established. Hence, development of more effective therapeutic methods using new antiviral agents is urgently needed. This review describes the current status of SSPE treatment and research, highlighting promising approaches to the development of more effective therapeutic methods.

Anno 2021: Which antivirals for the coming decade?

Despite considerable progress in the development of antiviral drugs, among which anti-immunodeficiency virus (HIV) and anti-hepatitis C virus (HCV) medications can be considered real success stories, many viral infections remain without an effective treatment. This not only applies to infectious outbreaks caused by zoonotic viruses that have recently spilled over into humans such as severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), but also ancient viral diseases that have been brought under control by vaccination such as variola (smallpox), poliomyelitis, measles, and rabies. A largely unsolved problem are endemic respiratory infections due to influenza, respiratory syncytial virus (RSV), and rhinoviruses, whose associated morbidity will likely worsen with increasing air pollution. Furthermore, climate changes will expose industrialized countries to a dangerous resurgence of viral hemorrhagic fevers, which might also become global infections. Herein, we summarize the recent progress that has been made in the search for new antivirals against these different threats that the world population will need to confront with increasing frequency in the next decade.

Synthesis, Crystal Structures and Anticancer Studies of Morpholinyldithiocarbamato Cu(II) and Zn(II) Complexes

Cu(II) and Zn(II) morpholinyldithiocarbamato complexes, formulated as [Cu(MphDTC)₂] and [Zn(μ-MphDTC)₂(MphDTC)₂], where MphDTC is morpholinyldithiocarbamate were synthesized and characterized by elemental analysis, spectroscopic techniques and single-crystal X-ray crystallography. The molecular structure of the Cu(II) complex revealed a mononuclear compound in which the Cu(II) ion was bonded to two morpholinyl dithiocarbamate ligands to form a four-coordinate distorted square planar geometry. The molecular structure of the Zn(II) complex was revealed to be dinuclear, and each metal ion was bonded to two morpholinyl dithiocarbamate bidentate anions, one acting as chelating ligand, the other as a bridge between the two Zn(II) ions. The anticancer activity of the morpholinyldithiocarbamate ligand, Cu(II) and Zn(II) complexes were evaluated against renal (TK10), melanoma (UACC62) and breast (MCF7) cancer cells by a Sulforhodamine B (SRB) assay. Morpholinyldithiocarbamate was more active than the standard drug parthenolide against renal and breast cancer cell lines, and [Zn(μ-MphDTC)₂(MphDTC)₂] was the most active complex against breast cancer. The copper(II) complex had a comparable activity with the standard against renal and breast cancer cell lines but showed an enhanced potency against melanoma when compared to parthenolide.

Measles Resurgence and Drug Development

Measles caused an estimated minimum of one million fatalities annually before vaccination. Outstanding progress towards controlling the virus has been made since the measles vaccine was introduced, but reduction of measles case-fatalities has stalled at around 100,000 annually for the last decade and a 2019 resurgence in several geographical regions threatens some of these past accomplishments. Whereas measles eradication through vaccination is feasible, a potentially open-ended endgame of elimination may loom. Other than doubling-down on existing approaches, is it worthwhile to augment vaccination efforts with antiviral therapeutics to solve the conundrum? This question is hypothetical at present, since no drugs have yet been approved specifically for the treatment of measles, or infection by any other pathogen of the paramyxovirus family. This article will consider obstacles that have hampered anti-measles and anti-paramyxovirus drug development, discuss MeV-specific challenges of clinical testing, and define drug properties suitable to address some of these problems.

Formal Deoxygenative Hydrogenation of Lactams Using PNHP-Pincer Ruthenium Complexes under Nonacidic Conditions

A formal deoxygenative hydrogenation of amides to amines with RuCl₂(NHC)(PN^HP) (NHC = 1,3-dimethylimizadol-2-ylidene, PN^HP = bis(2-diphenylphosphinoethyl)amine) is described. Various secondary amides, especially NH-lactams, are reduced with H₂ (3.0-5.0 MPa) to amines at a temperature range of 120-150 °C with 1.0-2.0 mol % of PN^HP-Ru catalysts in the presence of Cs₂CO₃. This process consists of (1) deaminative hydrogenation of secondary amides to generate primary amines and alcohols, (2) dehydrogenative coupling of the transient amines with alcohols to generate imines, and (3) hydrogenation of imines to give the formally deoxygenated secondary amine products.

Measles Encephalitis: Towards New Therapeutics

Measles remains a major cause of morbidity and mortality worldwide among vaccine preventable diseases. Recent decline in vaccination coverage resulted in re-emergence of measles outbreaks. Measles virus (MeV) infection causes an acute systemic disease, associated in certain cases with central nervous system (CNS) infection leading to lethal neurological disease. Early following MeV infection some patients develop acute post-infectious measles encephalitis (APME), which is not associated with direct infection of the brain. MeV can also infect the CNS and cause sub-acute sclerosing panencephalitis (SSPE) in immunocompetent people or measles inclusion-body encephalitis (MIBE) in immunocompromised patients. To date, cellular and molecular mechanisms governing CNS invasion are still poorly understood. Moreover, the known MeV entry receptors are not expressed in the CNS and how MeV enters and spreads in the brain is not fully understood. Different antiviral treatments have been tested and validated in vitro, ex vivo and in vivo, mainly in small animal models. Most treatments have high efficacy at preventing infection but their effectiveness after CNS manifestations remains to be evaluated. This review describes MeV neural infection and current most advanced therapeutic approaches potentially applicable to treat MeV CNS infection.

Development of an allosteric inhibitor class blocking RNA elongation by the respiratory syncytial virus polymerase complex

Respiratory syncytial virus (RSV) represents a significant health threat to infants and to elderly or immunocompromised individuals. There are currently no vaccines available to prevent RSV infections, and disease management is largely limited to supportive care, making the identification and development of effective antiviral therapeutics against RSV a priority. To identify effective chemical scaffolds for managing RSV disease, we conducted a high-throughput anti-RSV screen of a 57,000-compound library. We identified a hit compound that specifically blocked activity of the RSV RNA-dependent RNA polymerase (RdRp) complex, initially with moderate low-micromolar potency. Mechanistic characterization in an in vitro RSV RdRp assay indicated that representatives of this compound class block elongation of RSV RNA products after initial extension by up to three nucleotides. Synthetic hit-to-lead exploration yielded an informative 3D quantitative structure-activity relationship (3D-QSAR) model and resulted in analogs with more than 20-fold improved potency and selectivity indices (SIs) of >1,000. However, first-generation leads exhibited limited water solubility and poor metabolic stability. A second optimization strategy informed by the 3D-QSAR model combined with in silico pharmacokinetics (PK) predictions yielded an advanced lead, AVG-233, that demonstrated nanomolar activity against both laboratory-adapted RSV strains and clinical RSV isolates. This anti-RSV activity extended to infection of established cell lines and primary human airway cells. PK profiling in mice revealed 34% oral bioavailability of AVG-233 and sustained high drug levels in the circulation after a single oral dose of 20 mg/kg. This promising first-in-class lead warrants further development as an anti-RSV drug.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Synthesis and Pharmacological Activities of Pyrazole Derivatives: A Review

Pyrazole and its derivatives are considered a pharmacologically important active scaffold that possesses almost all types of pharmacological activities. The presence of this nucleus in pharmacological agents of diverse therapeutic categories such as celecoxib, a potent anti-inflammatory, the antipsychotic CDPPB, the anti-obesity drug rimonabant, difenamizole, an analgesic, betazole, a H2-receptor agonist and the antidepressant agent fezolamide have proved the pharmacological potential of the pyrazole moiety. Owing to this diversity in the biological field, this nucleus has attracted the attention of many researchers to study its skeleton chemically and biologically. This review highlights the different synthesis methods and the pharmacological properties of pyrazole derivatives. Studies on the synthesis and biological activity of pyrazole derivatives developed by many scientists around the globe are reported.

Design, synthesis and DNA-binding study of some novel morpholine linked thiazolidinone derivatives

The emergence of multiple drug resistance amongst bacterial strains resulted in many clinical drugs to be ineffective. Being vulnerable to bacterial infections any lack in the development of new antimicrobial drugs could pose a serious threat to public health. Here we report design and synthesis of a novel class of morpholine linked thiazolidinone hybrid molecules. The compounds were characterized by FT-IR, NMR and HRMS techniques. Susceptibility tests showed that most of the synthesized molecules were highly active against multiple bacterial strains. Compound 3f displayed MIC values which were better than the standard drug for most of the tested strains. DNA being a well defined target for many antimicrobial drugs was probed as possible target for these synthetic molecules. DNA-binding study of 3f with sm-DNA was probed through UV-vis absorption, fluorescence quenching, gel electrophoresis and molecular docking techniques. The studies revealed that compound 3f has strong affinity towards DNA and binds at the minor groove. The docking studies revealed that the compound 3f shows preferential binding towards A/T residues.

Organization, Function, and Therapeutic Targeting of the Morbillivirus RNA-Dependent RNA Polymerase Complex

The morbillivirus genus comprises major human and animal pathogens, including the highly contagious measles virus. Morbilliviruses feature single stranded negative sense RNA genomes that are wrapped by a plasma membrane-derived lipid envelope. Genomes are encapsidated by the viral nucleocapsid protein forming ribonucleoprotein complexes, and only the encapsidated RNA is transcribed and replicated by the viral RNA-dependent RNA polymerase (RdRp). In this review, we discuss recent breakthroughs towards the structural and functional understanding of the morbillivirus polymerase complex. Considering the clinical burden imposed by members of the morbillivirus genus, the development of novel antiviral therapeutics is urgently needed. The viral polymerase complex presents unique structural and enzymatic properties that can serve as attractive candidates for druggable targets. We evaluate distinct strategies for therapeutic intervention and examine how high-resolution insight into the organization of the polymerase complex may pave the path towards the structure-based design and optimization of next-generation RdRp inhibitors.

New antiviral approaches for respiratory syncytial virus and other mononegaviruses: Inhibiting the RNA polymerase

Worldwide, respiratory syncytial virus (RSV) causes severe disease in infants, the elderly, and immunocompromised people. No vaccine or effective antiviral treatment is available. RSV is a member of the non-segmented, negative-strand (NNS) group of RNA viruses and relies on its RNA-dependent RNA polymerase to transcribe and replicate its genome. Because of its essential nature and unique properties, the RSV polymerase has proven to be a good target for antiviral drugs, with one compound, ALS-8176, having already achieved clinical proof-of-concept efficacy in a human challenge study. In this article, we first provide an overview of the role of the RSV polymerase in viral mRNA transcription and genome replication. We then review past and current approaches to inhibiting the RSV polymerase, including use of nucleoside analogs and non-nucleoside inhibitors. Finally, we consider polymerase inhibitors that hold promise for treating infections with other NNS RNA viruses, including measles and Ebola.

The paramyxovirus polymerase complex as a target for next-generation anti-paramyxovirus therapeutics

The paramyxovirus family includes major human and animal pathogens, including measles virus, mumps virus, and human respiratory syncytial virus (RSV), as well as the emerging zoonotic Hendra and Nipah viruses. In the U.S., RSV is the leading cause of infant hospitalizations due to viral infectious disease. Despite their clinical significance, effective drugs for the improved management of paramyxovirus disease are lacking. The development of novel anti-paramyxovirus therapeutics is therefore urgently needed. Paramyxoviruses contain RNA genomes of negative polarity, necessitating a virus-encoded RNA-dependent RNA polymerase (RdRp) complex for replication and transcription. Since an equivalent enzymatic activity is absent in host cells, the RdRp complex represents an attractive druggable target, although structure-guided drug development campaigns are hampered by the lack of high-resolution RdRp crystal structures. Here, we review the current structural and functional insight into the paramyxovirus polymerase complex in conjunction with an evaluation of the mechanism of activity and developmental status of available experimental RdRp inhibitors. Our assessment spotlights the importance of the RdRp complex as a premier target for therapeutic intervention and examines how high-resolution insight into the organization of the complex will pave the path toward the structure-guided design and optimization of much-needed next-generation paramyxovirus RdRp blockers.

An orally available, small-molecule polymerase inhibitor shows efficacy against a lethal morbillivirus infection in a large animal model

Measles virus is a highly infectious morbillivirus responsible for major morbidity and mortality in unvaccinated humans. The related, zoonotic canine distemper virus (CDV) induces morbillivirus disease in ferrets with 100% lethality. We report an orally available, shelf-stable pan-morbillivirus inhibitor that targets the viral RNA polymerase. Prophylactic oral treatment of ferrets infected intranasally with a lethal CDV dose reduced viremia and prolonged survival. Ferrets infected with the same dose of virus that received post-infection treatment at the onset of viremia showed low-grade viral loads, remained asymptomatic, and recovered from infection, whereas control animals succumbed to the disease. Animals that recovered also mounted a robust immune response and were protected against rechallenge with a lethal CDV dose. Drug-resistant viral recombinants were generated and found to be attenuated and transmission-impaired compared to the genetic parent virus. These findings may pioneer a path toward an effective morbillivirus therapy that could aid measles eradication by synergizing with vaccination to close gaps in herd immunity due to vaccine refusal.

Antiviral atropisomers: conformational energy surfaces by NMR for host-directed myxovirus blockers

Biologically active organic molecules characterized by a high single bond torsional barrier generate isolable isomers (atropisomers) and offer a unique stereochemical component to the design of selective therapeutic agents. The present work presents a nanomolar active inhibitor of myxoviruses, which most likely acts by blocking one or more cellular host proteins but also, serendipitously, exhibits axial chirality with an energy barrier of ΔG((++)) ≥30 kcal/mol. The latter has been probed by variable temperature NMR and microwave irradiation and by high level DFT transition state analysis and force field calculations. Full conformational profiles of the corresponding (aR,S) and (aS,S) atropisomers at ambient temperature were derived by conformer deconvolution with NAMFIS (NMR Analysis by Molecular Flexibility In Solution) methodology to generate seven and eight individual conformations, each assigned a % population. An accurate evaluation of a key torsion angle at the center of the molecules associated with a (3)JC-S-C-H coupling constant was obtained by mapping the S-C bond rotation with the MPW1PW91/6-31G-d,p DFT method followed by fitting the resulting dihedral angles and J-values to a Karplus expression. Accordingly, we have developed a complete conformational profile of diastereomeric atropisomers consistent with both high and low rotational barriers. We expect this assessment to assist the rationalization of the selectivity of the two (aR,S) and (aS,S) forms against host proteins, while offering insights into their divergent toxicity behavior.

Synergizing vaccinations with therapeutics for measles eradication

INTRODUCTION

The measles virus is a major human pathogen responsible for approximately 150,000 deaths annually. The disease is vaccine preventable and eradication of the virus is considered feasible, in principle. However, a herd immunity exceeding 95% is required to prevent sporadic viral outbreaks in a population. Declining disease prevalence, combined with public anxiety over the vaccination's safety, has led to increased vaccine refusal, especially in Europe. This has led to the resurgence of measles in some areas.

AREAS COVERED

This article discusses whether synergizing effective measles therapeutics with the measles vaccination could contribute to finally eradicating measles. The authors identify key elements in a desirable drug profile and review current disease management strategies and the state of experimental inhibitor candidates. The authors also evaluate the risk associated with viral escape from inhibition, and consider the potential of measles therapeutics in the management of persistent central nervous system (CNS) viral infection. Finally, the authors contemplate the possible impact of therapeutics in controlling the threat imposed by closely related zoonotic pathogens of the same genus as measles.

EXPERT OPINION

Efficacious therapeutics used for post-exposure prophylaxis of high-risk social contacts of confirmed index cases may aid measles eradication by closing herd immunity gaps; this is due to vaccine refusal or failure in populations with overall good vaccination coverage. The envisioned primarily prophylactic application of measles therapeutics to a predominantly pediatric and/or adolescent population, dictates the drug profile. It also has to be safe and efficacious, orally available, shelf-stable at ambient temperature and amenable to cost-effective manufacturing.

Fatal measles virus infection prevented by brain-penetrant fusion inhibitors

Measles virus (MV) infection causes an acute childhood disease that can include infection of the central nervous system and can rarely progress to severe neurological disease for which there is no specific treatment. We generated potent antiviral peptide inhibitors of MV entry and spreading and MV-induced cell fusion. Dimers of MV-specific peptides derived from the C-terminal heptad repeat region of the MV fusion protein, conjugated to cholesterol, efficiently protect SLAM transgenic mice from fatal MV infection. Fusion inhibitors hold promise for the prophylaxis of MV infection in unvaccinated and immunocompromised people, as well as potential for the treatment of grave neurological complications of measles.