Peptidomimetic inhibitors of TMPRSS2 block SARS-CoV-2 infection in cell culture

Development of ketobenzothiazole-based peptidomimetic TMPRSS13 inhibitors with low nanomolar potency

TMPRSS13, a member of the Type II Transmembrane Serine Proteases (TTSP) family, is involved in cancer progression and in respiratory virus cell entry. To date, no inhibitors have been specifically developed for this protease. In this study, a chemical library of 65 ketobenzothiazole-based peptidomimetic molecules was screened against a proteolytically active form of recombinant TMPRSS13 to identify novel inhibitors. Following an initial round of screening, subsequent synthesis of additional derivatives supported by molecular modelling revealed important molecular determinants involved in TMPRSS13 inhibition. One inhibitor, N-0430, achieved low nanomolar affinity towards TMPRSS13 activity in a cellular context. Using a SARS-CoV-2 pseudovirus cell entry model, we further demonstrated the ability of N-0430 to block TMPRSS13-dependent entry of the pseudovirus. The identified peptidomimetic inhibitors and the molecular insights into their potency gained from this study will aid in the development of specific TMPRSS13 inhibitors.

LL-37 Inhibits TMPRSS2-Mediated S2' Site Cleavage and SARS-CoV-2 Infection but Not Omicron Variants

Continual evolution of SARS-CoV-2 spike drives the emergence of Omicron variants that show increased spreading and immune evasion. Understanding how the variants orientate themselves towards host immune defence is crucial for controlling future pandemics. Herein, we demonstrate that human cathelicidin LL-37, a crucial component of innate immunity, predominantly binds to the S2 subunit of SARS-CoV-2 spike protein, occupying sites where TMPRSS2 typically binds. This binding impedes TMPRSS2-mediated priming at site S2' and subsequent membrane fusion processes. The mutation N764K within S2 subunit of Omicron variants reduces affinity for LL-37 significantly, thereby diminishing binding capacity and inhibitory effects on membrane fusion. Moreover, the early humoral immune response enhanced by LL-37 is observed in mice against SARS-CoV-2 spike but not Omicron BA.4/5 spike. These findings reveal the mechanism underlying interactions amongst LL-37, TMPRSS2 and SARS-CoV-2 and VOCs, and highlight the distinct mutation for Omicron variants to evade the fusion activity inhibition by host innate immunity.

Structural basis of TMPRSS11D specificity and autocleavage activation

Transmembrane Protease, Serine-2 (TMPRSS2) and TMPRSS11D are human proteases that enable SARS-CoV-2 and Influenza A/B virus infections, but their biochemical mechanisms for facilitating viral cell entry remain unclear. We show these proteases spontaneously and efficiently cleave their own zymogen activation motifs, activating their broader protease activity on cellular substrates. We determine TMPRSS11D co-crystal structures with a native and an engineered activation motif, revealing insights into its autocleavage activation and distinct substrate binding cleft features. Leveraging this structural data, we develop nanomolar potency peptidomimetic inhibitors of TMPRSS11D and TMPRSS2. We show that a broad serine protease inhibitor that underwent clinical trials for TMPRSS2-targeted COVID-19 therapy, nafamostat mesylate, was rapidly cleaved by TMPRSS11D and converted to low activity derivatives. In this work, we develop mechanistic insights into human protease viral tropism and highlight both the strengths and limitations of existing human serine protease inhibitors, informing future drug discovery efforts targeting these proteases.

Exploring TMPRSS2 Drug Target to Combat Influenza and Coronavirus Infection

Respiratory viral infections, including influenza and coronaviruses, present significant health risks worldwide. The recent COVID-19 pandemic highlights the urgent need for novel and effective antiviral agents. The host cell protease, transmembrane serine protease 2 (TMPRSS2), facilitates viral pathogenesis by playing a critical role in viral invasion and disease progression. This protease is coexpressed with the viral receptors of angiotensin-converting enzyme 2 (ACE2) for SARS-CoV-2 in the human respiratory tract and plays a significant role in activating viral proteins and spreading. TMPRSS2 activates the coronavirus spike (S) protein and permits membrane fusion and viral entry by cleaving the virus surface glycoproteins. It also activates the hemagglutinin (HA) protein, an enzyme necessary for the spread of influenza virus. TMPRSS2 inhibitors can reduce viral propagation and morbidity by blocking viral entry into respiratory cells and reducing viral spread, inflammation, and disease severity. This review examines the role of TMPRSS2 in viral replication and pathogenicity. It also offers potential avenues to develop targeted antivirals to inhibit TMPRSS2 function, suggesting a possible focus on targeted antiviral development. Ultimately, the review seeks to contribute to improving public health outcomes related to these viral infections.

From N-0385 to N-0920: Unveiling a Host-Directed Protease Inhibitor with Picomolar Antiviral Efficacy against Prevalent SARS-CoV-2 Variants

The worldwide spread of new SARS-CoV-2 variants emphasizes the need to diversify existing therapeutic strategies. TMPRSS2, a host protease crucial for SARS-CoV-2 entry, has garnered significant research attention as a potential target for therapeutic intervention. Here, we optimized N-0385, a previously reported TMPRSS2 ketobenzothiazole-based peptidomimetic inhibitor, by screening 135 derivatives for target affinity and antiviral potency. Among the top candidates, N-0695 exhibited low nanomolar Ki values against three TTSPs associated with respiratory virus entry: TMPRSS2, matriptase, and TMPRSS13. Notably, N-0920 demonstrated exceptional potency in reducing SARS-CoV-2 variants EG.5.1 and JN.1 entry in Calu-3 cells, representing the first in cellulo picomolar inhibitor with EC50 values of 300 and 90 pM, respectively. Additionally, molecular modeling provided insights into the binding interactions between the compounds and their targets. This study underscores the effectiveness of our screening approach in refining an existing peptidomimetic scaffold to enhance selectivity and antiviral activity.

Optimizing the pharmacokinetics and selectivity of TMPRSS2 inhibitors

Since 2019, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has undergone significant genomic mutations, contributing to resistance against existing 2019 coronavirus disease (COVID-19) treatments. In a previous study, we identified N-0385, a potent host-directed inhibitor of transmembrane serine protease 2 (TMPRSS2), which has therapeutic efficacy towards SARS-CoV-2 infection. However, in further evaluation of its preclinical druggability, N-0385 displayed unfavorable pharmacokinetic properties, including high bioavailability (99 %) following intranasal (IN) administration. This can lead to substantial systemic exposure and potential adverse effects due to off-target interactions. Here, we designed a library of peptidomimetic compounds with P3 site modifications on an optimized scaffold. We sought to maintain sub-nanomolar potency against TMPRSS2 (Kis < 2 nM), reduce pseudovirus infection, while addressing the lack of selectivity and excessive lung uptake. Notably, inhibitor 9, which contains Asp at the P3 position, achieved a two-fold increase in TMPRSS2 inhibitory potency (Ki = 0.13 ± 0.03 nM), a >700-fold selectivity over Factor Xa (FXa), and showed superior selectivity against other proteases (matriptase, transmembrane serine protease 6 (TMPRSS6), thrombin, furin, and tPA). Despite concerns about the role of FXa in the coagulation cascade, compound 9 had no impact on coagulation or thrombolysis 2 h after in vitro treatment. In the air-liquid interface (ALI) model of the lung epithelium, compound 9 displayed a 1.5-fold decrease in permeability compared to N-0385 and demonstrated sustained stability in lungs (11 h) and plasma (13 h). Taken together, our data demonstrate that continued optimization of this type of inhibitors will lead to improved therapeutics for the treatment of SARS-CoV-2 infection by IN administration.

Ligand-Based Design of Selective Peptidomimetic uPA and TMPRSS2 Inhibitors with Arg Bioisosteres

Trypsin-like serine proteases are involved in many important physiological processes like blood coagulation and remodeling of the extracellular matrix. On the other hand, they are also associated with pathological conditions. The urokinase-pwlasminogen activator (uPA), which is involved in tissue remodeling, can increase the metastatic behavior of various cancer types when overexpressed and dysregulated. Another member of this protease class that received attention during the SARS-CoV 2 pandemic is TMPRSS2. It is a transmembrane serine protease, which enables cell entry of the coronavirus by processing its spike protein. A variety of different inhibitors have been published against both proteases. However, the selectivity over other trypsin-like serine proteases remains a major challenge. In the current study, we replaced the arginine moiety at the P1 site of peptidomimetic inhibitors with different bioisosteres. Enzyme inhibition studies revealed that the phenylguanidine moiety in the P1 site led to strong affinity for TMPRSS2, whereas the cyclohexylguanidine derivate potently inhibited uPA. Both inhibitors exhibited high selectivity over other structurally similar and physiologically important proteases.

Optimization of Ketobenzothiazole-Based Type II Transmembrane Serine Protease Inhibitors to Block H1N1 Influenza Virus Replication

Human influenza viruses cause acute respiratory symptoms that can lead to death. Due to the emergence of antiviral drug-resistant strains, there is an urgent requirement for novel antiviral agents and innovative therapeutic strategies. Using the peptidomimetic ketobenzothiazole protease inhibitor RQAR-Kbt (IN-1, aka N-0100) as a starting point, we report how substituting P2 and P4 positions with natural and unnatural amino acids can modulate the inhibition potency toward matriptase, a prototypical type II transmembrane serine protease (TTSP) that acts as a priming protease for influenza viruses. We also introduced modifications of the peptidomimetics N-terminal groups, leading to significant improvements (from μM to nM, 60 times more potent than IN-1) in their ability to inhibit the replication of influenza H1N1 virus in the Calu-3 cell line derived from human lungs. The selectivity towards other proteases has been evaluated and explained using molecular modeling with a crystal structure recently obtained by our group. By targeting host cell TTSPs as a therapeutic approach, it may be possible to overcome the high mutational rate of influenza viruses and consequently prevent potential drug resistance.

Current Views About the Link between SARS-CoV-2 and the Liver: Friends or Foe?

The emergence of the novel coronavirus and the pandemic resulting from its spread have led to significant negative impacts on health, economy, relationships, and others. Particularly in the field of hospital care, the need for a greater number of patients has led to a breakdown of the system. Gastrointestinal manifestations are common in SARS-COV 2 patients, while 10% of those who are sick exhibit symptoms only from gastrointestinal without any manifestation on the part of the respiratory tract. The main manifestations are nausea, vomiting, diarrhoea, and anorexia. It is also interesting to note that biochemical liver disorder is a frequent finding and is associated with a worse prognosis and higher probability admission to intensive care. It was also observed that RNA from the virus was found in the stool several days after the tests came back negative pulmonary secretions, while rectal swab virus detection methods were used with a lower but comparable sensitivity to that of nasal swabs. Gastrointestinal symptoms in SARS-COV 2 infection are common and their search should be part of the initial diagnosis approach and have a connection with the gut microbiota dysbiosis and this can lead to an alteration of the gut/liver axis.

Bacterial Proteases as Potentially Exploitable Modulators of SARS-CoV-2 Infection: Logic from the Literature, Informatics, and Inspiration from the Dog

(1) Background: The COVID-19 pandemic left many intriguing mysteries. Retrospective vulnerability trends tie as strongly to odd demographics as to exposure profiles, genetics, health, or prior medical history. This article documents the importance of nasal microbiome profiles in distinguishing infection rate trends among differentially affected subgroups. (2) Hypothesis: From a detailed literature survey, microbiome profiling experiments, bioinformatics, and molecular simulations, we propose that specific commensal bacterial species in the Pseudomonadales genus confer protection against SARS-CoV-2 infections by expressing proteases that may interfere with the proteolytic priming of the Spike protein. (3) Evidence: Various reports have found elevated Moraxella fractions in the nasal microbiomes of subpopulations with higher resistance to COVID-19 (e.g., adolescents, COVID-19-resistant children, people with strong dietary diversity, and omnivorous canines) and less abundant ones in vulnerable subsets (the elderly, people with narrower diets, carnivorous cats and foxes), along with bioinformatic evidence that Moraxella bacteria express proteases with notable homology to human TMPRSS2. Simulations suggest that these proteases may proteolyze the SARS-CoV-2 spike protein in a manner that interferes with TMPRSS2 priming.

Omicsynin B4 potently blocks coronavirus infection by inhibiting host proteases cathepsin L and TMPRSS2

The emergence of SARS-CoV-2 variants represents a major threat to public health and requires identification of novel therapeutic agents to address the unmet medical needs. Small molecules impeding viral entry through inhibition of spike protein priming proteases could have potent antiviral effects against SARS-CoV-2 infection. Omicsynin B4, a pseudo-tetrapeptides identified from Streptomyces sp. 1647, has potent antiviral activity against influenza A viruses in our previous study. Here, we found omicsynin B4 exhibited broad-spectrum anti-coronavirus activity against HCoV-229E, HCoV-OC43 and SARS-CoV-2 prototype and its variants in multiple cell lines. Further investigations revealed omicsynin B4 blocked the viral entry and might be related to the inhibition of host proteases. SARS-CoV-2 spike protein mediated pseudovirus assay supported the inhibitory activity on viral entry of omicsynin B4 with a more potent inhibition of Omicron variant, especially when overexpression of human TMPRSS2. Moreover, omicsynin B4 exhibited superior inhibitory activity in the sub-nanomolar range against CTSL, and a sub-micromolar inhibition against TMPRSS2 in biochemical assays. The molecular docking analysis confirmed that omicsynin B4 fits well in the substrate binding sites and forms a covalent bond to Cys25 and Ser441 in CTSL and TMPRSS2, respectively. In conclusion, we found that omicsynin B4 may serve as a natural protease inhibitor for CTSL and TMPRSS2, blocking various coronavirus S protein-driven entry into cells. These results further highlight the potential of omicsynin B4 as an attractive candidate as a broad-spectrum anti-coronavirus agent that could rapidly respond to emerging variants of SARS-CoV-2.

S Protein, ACE2 and Host Cell Proteases in SARS-CoV-2 Cell Entry and Infectivity; Is Soluble ACE2 a Two Blade Sword? A Narrative Review

Since the spread of the deadly virus SARS-CoV-2 in late 2019, researchers have restlessly sought to unravel how the virus enters the host cells. Some proteins on each side of the interaction between the virus and the host cells are involved as the major contributors to this process: (1) the nano-machine spike protein on behalf of the virus, (2) angiotensin converting enzyme II, the mono-carboxypeptidase and the key component of renin angiotensin system on behalf of the host cell, (3) some host proteases and proteins exploited by SARS-CoV-2. In this review, the complex process of SARS-CoV-2 entrance into the host cells with the contribution of the involved host proteins as well as the sequential conformational changes in the spike protein tending to increase the probability of complexification of the latter with angiotensin converting enzyme II, the receptor of the virus on the host cells, are discussed. Moreover, the release of the catalytic ectodomain of angiotensin converting enzyme II as its soluble form in the extracellular space and its positive or negative impact on the infectivity of the virus are considered.