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1.
Nat Chem ; 15(7): 998-1005, 2023 07.
Article in English | MEDLINE | ID: covidwho-2324972

ABSTRACT

γ-Amino acids can play important roles in the biological activities of natural products; however, the ribosomal incorporation of γ-amino acids into peptides is challenging. Here we report how a selection campaign employing a non-canonical peptide library containing cyclic γ2,4-amino acids resulted in the discovery of very potent inhibitors of the SARS-CoV-2 main protease (Mpro). Two kinds of cyclic γ2,4-amino acids, cis-3-aminocyclobutane carboxylic acid (γ1) and (1R,3S)-3-aminocyclopentane carboxylic acid (γ2), were ribosomally introduced into a library of thioether-macrocyclic peptides. One resultant potent Mpro inhibitor (half-maximal inhibitory concentration = 50 nM), GM4, comprising 13 residues with γ1 at the fourth position, manifests a 5.2 nM dissociation constant. An Mpro:GM4 complex crystal structure reveals the intact inhibitor spans the substrate binding cleft. The γ1 interacts with the S1' catalytic subsite and contributes to a 12-fold increase in proteolytic stability compared to its alanine-substituted variant. Knowledge of interactions between GM4 and Mpro enabled production of a variant with a 5-fold increase in potency.


Subject(s)
Amino Acids , COVID-19 , Amino Acids/chemistry , Antiviral Agents/chemistry , Carboxylic Acids , Peptides/chemistry , Protease Inhibitors/chemistry , Protease Inhibitors/pharmacology , Protein Conformation , SARS-CoV-2/metabolism
2.
J Chem Inf Model ; 63(9): 2866-2880, 2023 05 08.
Article in English | MEDLINE | ID: covidwho-2303112

ABSTRACT

SARS-CoV-2 is the causative agent of COVID-19 and is responsible for the current global pandemic. The viral genome contains 5 major open reading frames of which the largest ORF1ab codes for two polyproteins, pp1ab and pp1a, which are subsequently cleaved into 16 nonstructural proteins (nsp) by two viral cysteine proteases encoded within the polyproteins. The main protease (Mpro, nsp5) cleaves the majority of the nsp's, making it essential for viral replication and has been successfully targeted for the development of antivirals. The first oral Mpro inhibitor, nirmatrelvir, was approved for treatment of COVID-19 in late December 2021 in combination with ritonavir as Paxlovid. Increasing the arsenal of antivirals and development of protease inhibitors and other antivirals with a varied mode of action remains a priority to reduce the likelihood for resistance emerging. Here, we report results from an artificial intelligence-driven approach followed by in vitro validation, allowing the identification of five fragment-like Mpro inhibitors with IC50 values ranging from 1.5 to 241 µM. The three most potent molecules (compounds 818, 737, and 183) were tested against SARS-CoV-2 by in vitro replication in Vero E6 and Calu-3 cells. Compound 818 was active in both cell models with an EC50 value comparable to its measured IC50 value. On the other hand, compounds 737 and 183 were only active in Calu-3, a preclinical model of respiratory cells, showing selective indexes twice as high as those for compound 818. We also show that our in silico methodology was successful in identifying both reversible and covalent inhibitors. For instance, compound 818 is a reversible chloromethylamide analogue of 8-methyl-γ-carboline, while compound 737 is an N-pyridyl-isatin that covalently inhibits Mpro. Given the small molecular weights of these fragments, their high binding efficiency in vitro and efficacy in blocking viral replication, these compounds represent good starting points for the development of potent lead molecules targeting the Mpro of SARS-CoV-2.


Subject(s)
Antiviral Agents , COVID-19 , Humans , Antiviral Agents/pharmacology , Antiviral Agents/chemistry , SARS-CoV-2 , Artificial Intelligence , Protease Inhibitors/pharmacology , Protease Inhibitors/chemistry , Molecular Docking Simulation
3.
Nat Commun ; 14(1): 1545, 2023 03 20.
Article in English | MEDLINE | ID: covidwho-2274434

ABSTRACT

The main protease from SARS-CoV-2 (Mpro) is responsible for cleavage of the viral polyprotein. Mpro self-processing is called maturation, and it is crucial for enzyme dimerization and activity. Here we use C145S Mpro to study the structure and dynamics of N-terminal cleavage in solution. Native mass spectroscopy analysis shows that mixed oligomeric states are composed of cleaved and uncleaved particles, indicating that N-terminal processing is not critical for dimerization. A 3.5 Å cryo-EM structure provides details of Mpro N-terminal cleavage outside the constrains of crystal environment. We show that different classes of inhibitors shift the balance between oligomeric states. While non-covalent inhibitor MAT-POS-e194df51-1 prevents dimerization, the covalent inhibitor nirmatrelvir induces the conversion of monomers into dimers, even with intact N-termini. Our data indicates that the Mpro dimerization is triggered by induced fit due to covalent linkage during substrate processing rather than the N-terminal processing.


Subject(s)
Coronavirus 3C Proteases , SARS-CoV-2 , Antiviral Agents , Protease Inhibitors/pharmacology , SARS-CoV-2/enzymology , Coronavirus 3C Proteases/chemistry
4.
J Med Chem ; 66(4): 2663-2680, 2023 02 23.
Article in English | MEDLINE | ID: covidwho-2252997

ABSTRACT

Nirmatrelvir (PF-07321332) is a nitrile-bearing small-molecule inhibitor that, in combination with ritonavir, is used to treat infections by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Nirmatrelvir interrupts the viral life cycle by inhibiting the SARS-CoV-2 main protease (Mpro), which is essential for processing viral polyproteins into functional nonstructural proteins. We report studies which reveal that derivatives of nirmatrelvir and other Mpro inhibitors with a nonactivated terminal alkyne group positioned similarly to the electrophilic nitrile of nirmatrelvir can efficiently inhibit isolated Mpro and SARS-CoV-2 replication in cells. Mass spectrometric and crystallographic evidence shows that the alkyne derivatives inhibit Mpro by apparent irreversible covalent reactions with the active site cysteine (Cys145), while the analogous nitriles react reversibly. The results highlight the potential for irreversible covalent inhibition of Mpro and other nucleophilic cysteine proteases by alkynes, which, in contrast to nitriles, can be functionalized at their terminal position to optimize inhibition and selectivity, as well as pharmacodynamic and pharmacokinetic properties.


Subject(s)
Antiviral Agents , COVID-19 , Coronavirus 3C Proteases , Nitriles , SARS-CoV-2 , Viral Protease Inhibitors , Humans , Antiviral Agents/pharmacology , Cysteine/chemistry , SARS-CoV-2/metabolism , Viral Nonstructural Proteins/metabolism , Viral Protease Inhibitors/pharmacology
5.
Acta Crystallogr D Struct Biol ; 78(Pt 6): 752-769, 2022 Jun 01.
Article in English | MEDLINE | ID: covidwho-1874079

ABSTRACT

In macromolecular crystallography, radiation damage limits the amount of data that can be collected from a single crystal. It is often necessary to merge data sets from multiple crystals; for example, small-wedge data collections from micro-crystals, in situ room-temperature data collections and data collection from membrane proteins in lipidic mesophases. Whilst the indexing and integration of individual data sets may be relatively straightforward with existing software, merging multiple data sets from small wedges presents new challenges. The identification of a consensus symmetry can be problematic, particularly in the presence of a potential indexing ambiguity. Furthermore, the presence of non-isomorphous or poor-quality data sets may reduce the overall quality of the final merged data set. To facilitate and help to optimize the scaling and merging of multiple data sets, a new program, xia2.multiplex, has been developed which takes data sets individually integrated with DIALS and performs symmetry analysis, scaling and merging of multi-crystal data sets. xia2.multiplex also performs analysis of various pathologies that typically affect multi-crystal data sets, including non-isomorphism, radiation damage and preferential orientation. After the description of a number of use cases, the benefit of xia2.multiplex is demonstrated within a wider autoprocessing framework in facilitating a multi-crystal experiment collected as part of in situ room-temperature fragment-screening experiments on the SARS-CoV-2 main protease.


Subject(s)
COVID-19 , Crystallography, X-Ray , Data Analysis , Humans , Macromolecular Substances/chemistry , SARS-CoV-2
6.
Cell Chem Biol ; 28(12): 1795-1806.e5, 2021 12 16.
Article in English | MEDLINE | ID: covidwho-1599513

ABSTRACT

Designing covalent inhibitors is increasingly important, although it remains challenging. Here, we present covalentizer, a computational pipeline for identifying irreversible inhibitors based on structures of targets with non-covalent binders. Through covalent docking of tailored focused libraries, we identify candidates that can bind covalently to a nearby cysteine while preserving the interactions of the original molecule. We found âˆ¼11,000 cysteines proximal to a ligand across 8,386 complexes in the PDB. Of these, the protocol identified 1,553 structures with covalent predictions. In a prospective evaluation, five out of nine predicted covalent kinase inhibitors showed half-maximal inhibitory concentration (IC50) values between 155 nM and 4.5 µM. Application against an existing SARS-CoV Mpro reversible inhibitor led to an acrylamide inhibitor series with low micromolar IC50 values against SARS-CoV-2 Mpro. The docking was validated by 12 co-crystal structures. Together these examples hint at the vast number of covalent inhibitors accessible through our protocol.


Subject(s)
Drug Design , Protein Kinase Inhibitors/chemistry , SARS-CoV-2/enzymology , Viral Matrix Proteins/antagonists & inhibitors , Acrylamide/chemistry , Acrylamide/metabolism , Binding Sites , COVID-19/pathology , COVID-19/virology , Catalytic Domain , Computational Biology/methods , Databases, Protein , Humans , Inhibitory Concentration 50 , Molecular Docking Simulation , Protein Kinase Inhibitors/metabolism , SARS-CoV-2/isolation & purification , Viral Matrix Proteins/metabolism
7.
Chem Sci ; 12(41): 13686-13703, 2021 Oct 27.
Article in English | MEDLINE | ID: covidwho-1569290

ABSTRACT

The main protease (Mpro) of SARS-CoV-2 is central to viral maturation and is a promising drug target, but little is known about structural aspects of how it binds to its 11 natural cleavage sites. We used biophysical and crystallographic data and an array of biomolecular simulation techniques, including automated docking, molecular dynamics (MD) and interactive MD in virtual reality, QM/MM, and linear-scaling DFT, to investigate the molecular features underlying recognition of the natural Mpro substrates. We extensively analysed the subsite interactions of modelled 11-residue cleavage site peptides, crystallographic ligands, and docked COVID Moonshot-designed covalent inhibitors. Our modelling studies reveal remarkable consistency in the hydrogen bonding patterns of the natural Mpro substrates, particularly on the N-terminal side of the scissile bond. They highlight the critical role of interactions beyond the immediate active site in recognition and catalysis, in particular plasticity at the S2 site. Building on our initial Mpro-substrate models, we used predictive saturation variation scanning (PreSaVS) to design peptides with improved affinity. Non-denaturing mass spectrometry and other biophysical analyses confirm these new and effective 'peptibitors' inhibit Mpro competitively. Our combined results provide new insights and highlight opportunities for the development of Mpro inhibitors as anti-COVID-19 drugs.

9.
Chem Commun (Camb) ; 57(12): 1430-1433, 2021 Feb 15.
Article in English | MEDLINE | ID: covidwho-1387498

ABSTRACT

The main viral protease (Mpro) of SARS-CoV-2 is a nucleophilic cysteine hydrolase and a current target for anti-viral chemotherapy. We describe a high-throughput solid phase extraction coupled to mass spectrometry Mpro assay. The results reveal some ß-lactams, including penicillin esters, are active site reacting Mpro inhibitors, thus highlighting the potential of acylating agents for Mpro inhibition.


Subject(s)
Antiviral Agents/pharmacology , Cysteine Endopeptidases/drug effects , Mass Spectrometry/methods , Protease Inhibitors/pharmacology , SARS-CoV-2/drug effects , beta-Lactams/pharmacology , Acylation , Antiviral Agents/chemistry , COVID-19/virology , Catalytic Domain , High-Throughput Screening Assays , Humans , Molecular Docking Simulation , Molecular Dynamics Simulation , Protease Inhibitors/chemistry , SARS-CoV-2/enzymology , beta-Lactams/chemistry
10.
Sci Rep ; 11(1): 13208, 2021 06 24.
Article in English | MEDLINE | ID: covidwho-1281733

ABSTRACT

Effective agents to treat coronavirus infection are urgently required, not only to treat COVID-19, but to prepare for future outbreaks. Repurposed anti-virals such as remdesivir and human anti-inflammatories such as barcitinib have received emergency approval but their overall benefits remain unclear. Vaccines are the most promising prospect for COVID-19, but will need to be redeveloped for any future coronavirus outbreak. Protecting against future outbreaks requires the identification of targets that are conserved between coronavirus strains and amenable to drug discovery. Two such targets are the main protease (Mpro) and the papain-like protease (PLpro) which are essential for the coronavirus replication cycle. We describe the discovery of two non-antiviral therapeutic agents, the caspase-1 inhibitor SDZ 224015 and Tarloxotinib that target Mpro and PLpro, respectively. These were identified through extensive experimental screens of the drug repurposing ReFRAME library of 12,000 therapeutic agents. The caspase-1 inhibitor SDZ 224015, was found to be a potent irreversible inhibitor of Mpro (IC50 30 nM) while Tarloxotinib, a clinical stage epidermal growth factor receptor inhibitor, is a sub micromolar inhibitor of PLpro (IC50 300 nM, Ki 200 nM) and is the first reported PLpro inhibitor with drug-like properties. SDZ 224015 and Tarloxotinib have both undergone safety evaluation in humans and hence are candidates for COVID-19 clinical evaluation.


Subject(s)
Antiviral Agents/chemistry , COVID-19 Drug Treatment , Coronavirus 3C Proteases/antagonists & inhibitors , Coronavirus Papain-Like Proteases/antagonists & inhibitors , Drug Repositioning , Oligopeptides/chemistry , Cell Line , Humans , Serpins/chemistry , Viral Proteins/chemistry
11.
Nat Commun ; 11(1): 5047, 2020 10 07.
Article in English | MEDLINE | ID: covidwho-841208

ABSTRACT

COVID-19, caused by SARS-CoV-2, lacks effective therapeutics. Additionally, no antiviral drugs or vaccines were developed against the closely related coronavirus, SARS-CoV-1 or MERS-CoV, despite previous zoonotic outbreaks. To identify starting points for such therapeutics, we performed a large-scale screen of electrophile and non-covalent fragments through a combined mass spectrometry and X-ray approach against the SARS-CoV-2 main protease, one of two cysteine viral proteases essential for viral replication. Our crystallographic screen identified 71 hits that span the entire active site, as well as 3 hits at the dimer interface. These structures reveal routes to rapidly develop more potent inhibitors through merging of covalent and non-covalent fragment hits; one series of low-reactivity, tractable covalent fragments were progressed to discover improved binders. These combined hits offer unprecedented structural and reactivity information for on-going structure-based drug design against SARS-CoV-2 main protease.


Subject(s)
Betacoronavirus/chemistry , Cysteine Endopeptidases/chemistry , Peptide Fragments/chemistry , Viral Nonstructural Proteins/chemistry , Betacoronavirus/enzymology , Binding Sites , Catalytic Domain , Coronavirus 3C Proteases , Crystallography, X-Ray , Cysteine Endopeptidases/metabolism , Drug Design , Mass Spectrometry , Models, Molecular , Peptide Fragments/metabolism , Protein Conformation , SARS-CoV-2 , Small Molecule Libraries/chemistry , Small Molecule Libraries/metabolism , Static Electricity , Viral Nonstructural Proteins/metabolism
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