Structure-based inhibitor design and repurposing clinical drugs to target SARS-CoV-2 proteases

SARS-CoV-2, the coronavirus responsible for the current COVID-19 pandemic, encodes two proteases, 3CLpro and PLpro, two of the main antiviral research targets. Here we provide an overview of the structures and functions of 3CLpro and PLpro and examine strategies of structure-based drug designing and drug repurposing against these proteases. Rational structure-based drug design enables the generation of potent and target-specific antivirals. Drug repurposing offers an attractive prospect with an accelerated turnaround. Thus far, several protease inhibitors have been identified, and some candidates are undergoing trials that may well prove to be effective antivirals against SARS-CoV-2.

Efficacy of current treatments against hepatitis C virus

It is estimated that currently, in the world, approximately 3% of the population has chronic hepatitis, the hepatitis C virus is the etiological agent most related to the development of this pathology. The diversity of genotypes (7) and quasi-species of HCV, due to its high mutation rate, interferes with an effective humoral immunity. The aim of this work is precisely to evoke those usual drugs used in HCV therapy, as well as cutting-edge drugs. The goal of treatment is the eradication of HCV infection. One strategy offered by the WHO is to eradicate the virus in at-risk populations. Alternatives to the previously used treatment with interferon and ribavirin are shown in this paper; protease inhibitors and other targets have now been developed to make eradication of the virus more effective.

Potent protease inhibitors of deadly lagoviruses: rabbit hemorrhagic disease virus and European brown hare syndrome virus

Rabbit hemorrhagic disease (RHD) and European brown hare syndrome (EBHS) are highly contagious diseases caused by lagoviruses in the Caliciviridae family and mainly affect rabbits and hares, respectively. These infectious diseases are associated with high mortality and a serious threat to domesticated (farmed and pet) and wild rabbits and hares, including endangered species such as Riparian brush rabbits. In the US, only isolated cases of RHD had been reported until Spring 2020. However, RHD caused by RHD type 2 virus (RHDV2) was unexpectedly reported in April 2020 in New Mexico and has subsequently spread to several US states infecting wild rabbits and hares. Since it is almost impossible to control and eradicate the virus from wild animals, it is highly likely RHD will become endemic in the US. Vaccines are available for RHD, however, there is no specific treatment for these deadly diseases. RHDV and EBHSV encode a 3C-like protease (3CLpro), which is essential for virus replication and a promising target for antiviral drug development. We have previously generated focused small molecule libraries of 3CLpro inhibitors and demonstrated the in vitro potency and in vivo efficacy of some protease inhibitors against viruses that encode 3CLpro including caliciviruses and coronaviruses. Here we established the enzyme assay and cell-based assays for these uncultivable viruses to determine the in vitro activity of 3CLpro inhibitors, including GC376, a protease inhibitor being developed for feline infectious peritonitis, and identified potent inhibitors of RHDV1 and 2 and EBHSV. In addition, structure-activity relationship study and homology modelling of the 3CLpros and inhibitors revealed that lagoviruses share similar structural requirements for 3CLpro inhibition with other caliciviruses.

A proteomics informed by transcriptomics insight into the proteome of Ornithodoros erraticus adult tick saliva

Background The argasid tick Ornithodoros erraticus is the main vector of tick-borne human relapsing fever (TBRF) and African swine fever (ASF) in the Mediterranean Basin. The prevention and control of these diseases would greatly benefit from the elimination of O. erraticus populations, and anti-tick vaccines are envisaged as an effective and sustainable alternative to chemical acaricide usage for tick control. Ornithodoros erraticus saliva contains bioactive proteins that play essential functions in tick feeding and host defence modulation, which may contribute to host infection by tick-borne pathogens. Hence, these proteins could be candidate antigen targets for the development of vaccines aimed at the control and prevention of O. erraticus infestations and the diseases this tick transmits. The objective of the present work was to obtain and characterise the proteome of the saliva of O. erraticus adult ticks as a means to identify and select novel salivary antigen targets. Methods A proteomics informed by transcriptomics (PIT) approach was applied to analyse samples of female and male saliva separately using the previously obtained O. erraticus sialotranscriptome as a reference database and two different mass spectrometry techniques, namely liquid chromatography–tandem mass spectrometry (LC–MS/MS) in data-dependent acquisition mode and sequential window acquisition of all theoretical fragment ion spectra MS (SWATH-MS). Results Up to 264 and 263 proteins were identified by LC–MS/MS in the saliva of O. erraticus female and male ticks, respectively, totalling 387 non-redundant proteins. Of these, 224 were further quantified by SWATH-MS in the saliva of both male and female ticks. Quantified proteins were classified into 23 functional categories and their abundance compared between sexes. Heme/iron-binding proteins, protease inhibitors, proteases, lipocalins and immune-related proteins were the categories most abundantly expressed in females, while glycolytic enzymes, protease inhibitors and lipocalins were the most abundantly expressed in males. Ninety-seven proteins were differentially expressed between the sexes, of which 37 and 60 were overexpressed in females and males, respectively. Conclusions The PIT approach demonstrated its usefulness for proteomics studies of O. erraticus, a non-model organism without genomic sequences available, allowing the publication of the first comprehensive proteome of the saliva of O. erraticus reported to date. These findings confirm important quantitative differences between sexes in the O. erraticus saliva proteome, unveil novel salivary proteins and functions at the tick–host feeding interface and improve our understanding of the physiology of feeding in O. erraticus ticks. The integration of O. erraticus sialoproteomic and sialotranscriptomic data will drive a more rational selection of salivary candidates as antigen targets for the development of vaccines aimed at the control of O. erraticus infestations and the diseases it transmits. Graphical Abstract

Fluorine-Modifications Contribute to Potent Antiviral Activity against Highly Drug-Resistant HIV-1 and Favorable Blood-Brain Barrier (BBB) Penetration Property of Novel Central Nervous System (CNS)-targeting HIV-1 Protease Inhibitors In Vitro .

To date, there are no specific treatment regimens for the HIV-1-related central nervous system (CNS) complications, such as HIV-1-associated neurocognitive disorders (HAND). In the present study, we report that two newly generated CNS-targeting HIV-1 protease inhibitors (PIs), GRL-08513 and GRL-08613, which have P1-3,5- bis -fluorophenyl- or P1- para -monofluorophenyl-ring, and P2-tetrahydropyrano-tetrahydrofuran ( Tp -THF) with a sulfonamide isostere, are potent against wild-type HIV-1s and multiple clinically isolated HIV-1s (EC 50 : 0.0001∼0.0032 μM). As assessed with HIV-1 variants that had been selected in vitro to propagate at 5 μM concentration of each HIV-1 PI (atazanavir, lopinavir, or amprenavir), GRL-08513 and GRL-08613 efficiently inhibited the replication of these highly-PI-resistant variants (EC 50 : 0.003∼0.006 μM). GRL-08513 and GRL-08613 also maintained their antiviral activity against HIV-2 ROD as well as severe multi-drug-resistant clinical HIV-1 variants. Additionally, when we assessed with the in vitro blood-brain barrier (BBB) reconstruction system, GRL-08513 and GRL-08613 showed the most promising properties of CNS-penetration among the evaluated compounds including the majority of FDA-approved cART drugs. In the crystallographic analysis of compound-protease (PR) complexes, it was demonstrated that the Tp -THF rings at the P2 moiety of GRL-08513 and GRL-08613 form robust hydrogen-bond interactions with the active-site of HIV-1 PR. Furthermore, both the P1-3,5- bis -fluorophenyl- and P1- para -monofluorophenyl-rings sustain greater contact surfaces and form stronger van der Waals interactions with PR compared to the case of darunavir-PR complex. Taken together, these results strongly suggest that GRL-08513 and GRL-08613 have favorable features for the patients infected with wild-type/multi-drug-resistant HIV-1s, and might serve as candidates of preventive and/or therapeutic for HAND and other CNS complications.

The Role of Proteases and Serpin Protease Inhibitors in β-Cell Biology and Diabetes

Regulation of the equilibrium between proteases and their inhibitors is fundamental to health maintenance. Consequently, developing a means of targeting protease activity to promote tissue regeneration and inhibit inflammation may offer a new strategy in therapy development for diabetes and other diseases. Specifically, recent efforts have focused on serine protease inhibitors, known as serpins, as potential therapeutic targets. The serpin protein family comprises a broad range of protease inhibitors, which are categorized into 16 clades that are all extracellular, with the exception of Clade B, which controls mostly intracellular proteases, including both serine- and papain-like cysteine proteases. This review discusses the most salient, and sometimes opposing, views that either inhibition or augmentation of protease activity can bring about positive outcomes in pancreatic islet biology and inflammation. These potential discrepancies can be reconciled at the molecular level as specific proteases and serpins regulate distinct signaling pathways, thereby playing equally distinct roles in health and disease development.