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SARS-CoV-2 is the viral pathogen causing the COVID19 global pandemic. Consequently, much research has gone into the development of pre-clinical assays for the discovery of new or repurposing of FDA-approved therapies. Preventing viral entry into a host cell would be an effective antiviral strategy. One mechanism for SARS-CoV-2 entry occurs when the spike protein on the surface of SARS-CoV-2 binds to an ACE2 receptor followed by cleavage at two cut sites (“priming”) that causes a conformational change allowing for viral and host membrane fusion. This fusion event is proceeded by release of viral RNA within the host cell. TMPRSS2 has an extracellular protease domain capable of cleaving the spike protein to initiate membrane fusion. Additionally, knock-out studies in mice have demonstrated reduced infection in the absence of TMPRSS2 with no detectable physiological impact; thus, TMPRSS2 is an attractive target for therapeutic development. A validated inhibitor of TMPRSS2 protease activity would be a valuable tool for studying the impact TMPRSS2 has in viral entry and potentially be an effective antiviral therapeutic. To enable inhibitor discovery and profiling of FDA-approved therapeutics, we describe an assay for the biochemical screening of recombinant TMPRSS2 suitable for high throughput application. We demonstrate effectiveness to quantify inhibition down to subnanomolar concentrations by assessing the inhibition of camostat, nafamostat and gabexate, clinically approved agents in Japan for pancreatitis due to their inhibition of trypsin-like proteases. Nafamostat and camostat are currently in clinical trials against COVID19. The rank order potency for the three inhibitors is: nafamostat (IC50 = 0.27 nM), camostat (IC50 = 6.2 nM) and gabexate (IC50 = 130 nM). Further profiling of these three inhibitors against a panel of proteases provides insight into selectivity and potency.

Coronavirus disease 2019 (COVID-19) is a disease that causes fatal disorders including severe pneumonia. To develop a therapeutic drug for COVID-19, a model that can reproduce the viral life cycle and evaluate the drug efficacy of anti-viral drugs is essential. In this study, we established a method to generate human bronchial organoids (hBO) from commercially available cryopreserved human bronchial epithelial cells and examined whether they could be used as a model for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) research. Our hBO contain basal, club, ciliated, and goblet cells. Angiotensin-converting enzyme 2 (ACE2), which is a receptor for SARS-CoV-2, and transmembrane serine proteinase 2 (TMPRSS2), which is an essential serine protease for priming spike (S) protein of SARS-CoV-2, were highly expressed. After SARS-CoV-2 infection, not only the intracellular viral genome, but also progeny virus, cytotoxicity, pyknotic cells, and moderate increases of the type I interferon signal could be observed. Treatment with camostat, an inhibitor of TMPRSS2, reduced the viral copy number to 2% of the control group. Furthermore, the gene expression profile in SARS-CoV-2-infected hBO was obtained by performing RNA-seq analysis. In conclusion, we succeeded in generating hBO that can be used for SARS-CoV-2 research and COVID-19 drug discovery.Graphical abstract

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has spread worldwide and caused widespread devastation. In the absence of definitive therapy, symptomatic management remains the standard of care. Repurposing of many existing drugs, including several anti-viral drugs, is being attempted to tackle the COVID-19 pandemic. However, most of them have failed to show significant benefit in clinical trials. An attractive approach may be to target host proteases involved in SARS-CoV-2 pathogenesis. The priming of the spike (S) protein of the virus by proteolytic cleavage by the transmembrane serine protease-2 (TMPRSS2) is necessary for the fusion of the virus to the host cell after it binds to its receptor angiotensin converting enzyme-2 (ACE2). There are other proteases with varying spatiotemporal locations that may be important for viral entry and subsequent replication inside the cells, and these include trypsin, furin and cathepsins. In this report, we have discussed the tentative therapeutic role of inhibitors of TMPRSS2, cathepsin, trypsin, furin, plasmin, factor X and elastase in infection caused by SARS-CoV-2. Both available evidence, as well as hypotheses, are discussed, with emphasis on drugs which are approved for other indications such as bromhexine, ammonium chloride, nafamostat, camostat, tranexamic acid, epsilon amino-caproic acid, chloroquine, ulinastatin, aprotinin and anticoagulant drugs. Simultaneously, novel compounds being tested and problems with using these agents are also discussed.

The unprecedented coronavirus SARS-CoV-2 outbreak at Wuhan, China caused acute respiratory infection to humans. There is no precise vaccine/therapeutic agents available to combat the COVID-19 disease. Some repurposed drugs are saving the life of diseased, but the complete cure is relatively less. Several drug targets have been reported to inhibit the SARS-CoV-2 virus infection, in that TMPRSS2 (Transmembrane protease serine 2) is one of the potential targets, inhibiting this protease stops the virus entry into the host human cell. Camostat mesylate, nafamostat and leupeptin are the drugs, in which the first two drugs are being used for COVID-19 and leupeptin also tested. To consider these as repurposed drugs for COVID-19, it is essential to understand their binding affinity and stability with TMPRSS2. In the present study, we performed the molecular docking and molecular dynamics (MD) simulation for the three molecules with the TMPRSS2. The docking study reveals that leupeptin molecule strongly binds with TMPRSS2 protein than the other two drug molecules. The RMSD and RMSF values of MD simulations shows, leupeptin and the amino acids of TMPRSS2 are very stable than the other molecules. Furthermore, leupeptin forms interactions with the key amino acids of TMPRSS2 and the same have been maintained during the MD simulations. This structural and dynamical information is useful to evaluate these drugs to be used as repurposed drugs, however, the strong binding profile of leupeptin with TMPRSS2, suggests, it may be considered as a repurposed drug for COVID-19 after clinical trial.

Here a review concerning drugs used in Italy against Covid-19 and its effects on humans. The main source of information abouttrials is the Italian Government. Relatedlinks are given. From thse links, the names of trials and drugs involved have been obtained.Some information and references about drugs have been collected from other web sites. References to scholar papers and news are also given. Drugs mentioned areTocilizumab, Sarilumab, Siltuximab, Canakinumab, Baricitinib, Methylprednisolone, Selinexor, Hydroxychloroquine, Enoxaparin sodium, Solnatide, Colchicine, Emapalumab, Anakinra, Remdesivir, Camostat, Nafamostat, Ivermectin. &nbsp

There is an urgent need to identify therapeutics for the treatment of Coronavirus diseases 2019 (COVID-19). Although different antivirals are given for the clinical management of SARS-CoV-2 infection, their efficacy is still under evaluation. Here, we have screened existing drugs approved for human use in a variety of diseases, to compare how they counteract SARS-CoV-2-induced cytopathic effect and viral replication in vitro. Among the potential 72 antivirals tested herein that were previously proposed to inhibit SARS-CoV-2 infection, only 18% had an IC50 below 25 μM or 102 IU/mL. These included plitidepsin, novel cathepsin inhibitors, nelfinavir mesylate hydrate, interferon 2-alpha, interferon-gamma, fenofibrate, camostat along the well-known remdesivir and chloroquine derivatives. Plitidepsin was the only clinically approved drug displaying nanomolar efficacy. Four of these families, including novel cathepsin inhibitors, blocked viral entry in a cell-type specific manner. Since the most effective antivirals usually combine therapies that tackle the virus at different steps of infection, we also assessed several drug combinations. Although no particular synergy was found, inhibitory combinations did not reduce their antiviral activity. Thus, these combinations could decrease the potential emergence of resistant viruses. Antivirals prioritized herein identify novel compounds and their mode of action, while independently replicating the activity of a reduced proportion of drugs which are mostly approved for clinical use. Combinations of these drugs should be tested in animal models to inform the design of fast track clinical trials.

Ongoing search for treatment to ease COVID-19 pandemic concentrate on development of a vaccine or medication to prevent and treat this disease. One of the possibilities is developing new antiviral drugs that are aiming at both a virus replication or the host factor(s) that are critical to virus’s replication. Serine proteases, which activate the viral spike glycoproteins and facilitate virus-cell membrane fusions for host cell entry, its replication and spread, are proposed as the potential targets for antiviral drug design. Existing literature is already providing evidence that transmembrane protease serine 2 (TMPRSS2) is one of the promising targets. When inhibited it can slow or stop replication of viruses including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). One of the convincing evidences of the critical role of TMPRSS2 in the coronavirus’s replication was provided by animal study. The replication of influenza viruses was inhibited in TMPRSS2(-/-) knockout mice in comparison to wild type (WT) mice, which developed high mortality rate. Existing inhibitors of TMPRSS2 can be divided into two groups. The first include drugs already approved by FDA or other organizations for treatment of different diseases. That include: Camostat (from Japan, produced by Ono Pharmaceutical), aprotinin (Trasylol, produced by Nordic Group Pharmaceuticals) and rimantadine (Flumadine, produced by Forest Pharmaceuticals, Inc.). Existing in vitro, in vivo and some limited human studies show that this type of drugs limit reproduction of coronaviruses and/or prevented the development of viral pneumonia. One study indicated that combined treatment by aprotinin and rimantadine prevented the development of fatal hemorrhagic viral pneumonia, and protected about 75% animals, when the separate administration of aprotinin or rimantadine induced less protection. The second group includes potential drugs not approved for the human use yet. That include plasminogen activator inhibitor type 1 (PAI-1) and recently developed small molecular inhibitors. PAI-1 is a serine protease inhibitor that regulates physiological breakdown of blood clots by inhibiting of tissue (tPA) and urokinase (uPA) plasminogen activators. But PAI-1 is also an effective inhibitor of various membrane-anchored serine proteases including TMPRSS2. It was reported that PAI-1 inhibited trypsin- and TMPRSS2-mediated cleavage of hemagglutinin and suppressed influenza virus in animals. PAI-1 is human in origin and engineered forms with extended half-life were developed and could be an attractive addition to the existing TMPRSS2 inhibitors. And finally, derivatives of sulfonylated 3-amindinophenylalanylamide were found to inhibit TMPRSS2 with a high affinity and efficiently block the influenza virus propagation in human cells. This paper is intended to provide review on possible or hypothetical beneficial effects of (TMPRSS2) inhibitors as one of options to fight infection with Covid-19.

The most rapid path to discovering treatment options for the novel coronavirus SARS-CoV-2 is to find existing medications that are active against the virus. We have focused on identifying repurposing candidates for the transmembrane serine protease family member II (TMPRSS2), which is critical for entry of coronaviruses into cells. Using known 3D structures of close homologs, we created seven homology models. We also identified a set of serine protease inhibitor drugs, generated several conformations of each, and docked them into our models. We used three known chemical (non-drug) inhibitors and one validated inhibitor of TMPRSS2 in MERS as benchmark compounds and found six compounds with predicted high binding affinity in the range of the known inhibitors. We also showed that a previously published weak inhibitor, Camostat, had a significantly lower binding score than our six compounds. All six compounds are anticoagulants with significant and potentially dangerous clinical effects and side effects. Nonetheless, if these compounds significantly inhibit SARS-CoV-2 infection, they could represent a potentially useful clinical tool.

According to the latest research, the novel coronavirus uses the protein angiotensin-converting enzyme 2 (ACE-2) as a receptor for docking to the host cell. Essential for entry is the priming of the spike (S) protein of the virus by host cell proteases. A broadly based team led by infection biologists from the German Primate Centre and with the participation of the Charité Hospital in Berlin, the Hanover Veterinary University Foundation, the BG-UnfallklinikMurnau, the LMU Munich, the Robert Koch Institute and the German Centre for Infection Research wanted to find out how SARS-CoV-2 enters host cells and how this process can be blocked [1]. They have published their findings in the journal "Cell" [1]. The team of scientists was initially able to confirm that SARS-CoV-2 docks to the host cell via the ACE-2 receptor. They also identified Transmembrane serine protease 2 (TMPRSS2) as the cellular protein responsible for entry into the cell [1-3].

The enzymes trypsin, furin and other proprotein-convertasen, cathepsin, transmembrane proteases (TMPRSS) and elastases play a role by the cell entry of Coronaviren (Coronaviridae). The proteases TMPRSS2 and TMPRSS11a, which exist in the respiratory tract richly and become experiment on cell surfaces, promote the entry of SARS-CoV-1-virus. For the TMPRSS-protease TMPRSS11d - also as protease similar to trypsin has confessed of the human respiratory tract - a proteolytic activation of the spike protein was proved by SARS-CoV.

Background: The pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19). COVID-19 may take a severe course, resulting in sepsis, and antivirals are urgently needed to combat the disease. However, at present, only drugs developed against other diseases are available including the Malaria drug hydroxychloroquine but their therapeutic efficacy is unclear. Camostat mesylate, a clinically-proven protease inhibitor for treatment of pancreatitis, was shown to block SARS-CoV-2 entry into lung cells. Whether camostat mesylate dampens COVID-19 induced sepsis and the associated organ failure is unknown. Here we compare clinical courses of critically ill COVID-19 patients treated with either camostat mesylate or hydroxychloroquine. Methods: Eleven COVID-19 patients with organ failure were treated in intensive care unit (ICU) at our institution. Five patients (group 1) received hydroxychloroquine and six patients (group 2) camostat mesylate. Clinical disease status was assessed by Simplified Acute Physiology Score (SAPS) II and Sequential/ Sepsis-related Organ Failure Assessment (SOFA) score at day 1, 3 and 8. Viral load was determined from nasopharyngeal swabs. Findings: Patient age ranged from 45 to 76 years, all but one had histories of chronic disease and cardiovascular risk factors. Median symptomatic period was 2-10 days before being transferred to ICU. No differences in SAPS II scores or SOFA scores were observed upon ICU admission. In group 1, SOFA and SAPS II scores remained elevated (2 patients died) while in group 2 SOFA and SAPS II score decreased from 9 to 4 points (1 patient died). The decline in disease severity for group 2 was paralleled by a decline in inflammatory markers, which was not observed in group 1. The virus load in the nasopharynx was variable between patients, did not correlate with organ failure and no marked differences were observed between groups 1 and 2. Interpretation: The severity of COVID-19 sepsis markedly decreased upon camostat mesylate treatment within a period of 8 days and a similar effect was not observed upon hydroxychloroquine treatment. Camostat mesylate thus warrants further evaluation within randomized clinical studies. Funding Statement: Authors were employed at the University of Gottingen or at the Infection Biology Unit of the German Primate Center (Leibniz Institute for Primate Research). All expenses were covered by publicly funded institutions. Stefan Pohlmann received funding from the German Federal Ministry of Education and Research (BMBF), RAPID Fund (#01KI1723D). Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: Compassionate use was approved by our local ethical committee at the University of Gottingen.

In addition to its role in the treatment of pancreatitis, the serine protease inhibitor nafamostat exhibits a retinal protective effect. However, the exact mechanisms underlying this effect are unknown. In this study, the neuroprotective effects of nafamostat and its orally active derivative sepimostat against excitotoxicity were further characterised in vitro and in vivo. In primary rat cortical neurons, nafamostat completely suppressed N-methyl-D-aspartate (NMDA)-induced cell death. Intravitreal injection of nafamostat and sepimostat protected the rat retina against NMDA-induced degeneration, whereas the structurally related compounds, gabexate and camostat, did not. The neuroprotective effects of nafamostat and the NR2B antagonist ifenprodil were remarkably suppressed by spermidine, a naturally occurring polyamine that modulates the NR2B subunit. Both nafamostat and sepimostat inhibited [3H]ifenprodil binding to fractionated rat brain membranes. Thus, nafamostat and sepimostat may exert neuroprotective effects against excitotoxic retinal degeneration through NMDA receptor antagonism at the ifenprodil-binding site of the NR2B subunit.

Trypsin is the major serine protease responsible for intestinal protein digestion. An inhibitor, camostat (CS), reduced weight gain, hyperglycemia, and dyslipidemia in obese rats; however, the mechanisms for these are largely unknown. We reasoned that CS creates an apparent dietary protein restriction, which is known to increase hepatic fibroblast growth factor 21 (FGF21). Therefore, metabolic responses to CS and a gut-restricted CS metabolite, FOY-251, were measured in mice. Food intake, body weight, blood glucose, branched-chain amino acids (LC/MS), hormone levels (ELISA), liver pathology (histology), and transcriptional changes (qRT-PCR) were measured in ob/ob, lean and diet-induced obese (DIO) C57BL/6 mice. In ob/ob mice, CS in chow (9–69 mg/kg) or FOY-251 (46 mg/kg) reduced food intake and body weight gain to a similar extent as pair-fed mice. CS decreased blood glucose, liver weight, and lipidosis and increased FGF21 gene transcription and plasma levels. In lean mice, CS increased liver FGF21 mRNA and plasma levels. Relative to pair feeding, FOY-251 also increased plasma FGF21 and induced liver FGF21 and integrated stress response (ISR) transcription. In DIO mice, FOY-251 (100 mg/kg po) did not alter peak glucose levels but reduced the AUC of the glucose excursion in response to an oral glucose challenge. FOY-251 increased plasma FGF21 levels. In addition to previously reported satiety-dependent (cholecystokinin-mediated) actions, intestinal trypsin inhibition engages non-satiety-related pathways in both leptin-deficient and DIO mice. This novel mechanism improves metabolism by a liver-integrated stress response and increased FGF21 expression levels in mice. NEW & NOTEWORTHY Trypsin inhibitors, including plant-based consumer products, have long been associated with metabolic improvements. Studies in the 1980s and 1990s suggested this was due to satiety hormones and caloric wasting by loss of protein and fatty acids in feces. This work suggests an entirely new mechanism based on the lower amounts of digested protein available in the gut. This apparent protein reduction may cause beneficial metabolic adaptation by the intestinal-liver axis to perceived nutrient stress.

Transmembrane serine protease TMPRSS2 activates the spike protein of highly pathogenic human coronaviruses such as severe acute respiratory syndrome-related coronavirus (SARS-CoV) and Middle East respiratory syndrome-related coronavirus (MERS-CoV). In vitro, activation induces virus-cell membrane fusion at the cell surface. However, the roles of TMPRSS2 during coronavirus infection in vivo are unclear. Here, we used animal models of SARS-CoV and MERS-CoV infection to investigate the role of TMPRSS2. Th1-prone C57BL/6 mice and TMPRSS2-knockout (KO) mice were used for SARS-CoV infection, and transgenic mice expressing the human MERS-CoV receptor DPP4 (hDPP4-Tg mice) and TMPRSS2-KO hDPP4-Tg mice were used for MERS-CoV infection. After experimental infection, TMPRSS2-deficient mouse strains showed reduced body weight loss and viral kinetics in the lungs. Lack of TMPRSS2 affected the primary sites of infection and virus spread within the airway, accompanied by less severe immunopathology. However, TMPRSS2-KO mice showed weakened inflammatory chemokine and/or cytokine responses to intranasal stimulation with poly(I·C), a Toll-like receptor 3 agonist. In conclusion, TMPRSS2 plays a crucial role in viral spread within the airway of murine models infected by SARS-CoV and MERS-CoV and in the resulting immunopathology. IMPORTANCE Broad-spectrum antiviral drugs against highly pathogenic coronaviruses and other emerging viruses are desirable to enable a rapid response to pandemic threats. Transmembrane protease serine type 2 (TMPRSS2), a protease belonging to the type II transmembrane serine protease family, cleaves the coronavirus spike protein, making it a potential therapeutic target for coronavirus infections. Here, we examined the role of TMPRSS2 using animal models of SARS-CoV and MERS-CoV infection. The results suggest that lack of TMPRSS2 in the airways reduces the severity of lung pathology after infection by SARS-CoV and MERS-CoV. Taken together, the results will facilitate development of novel targets for coronavirus therapy.

Background: The trans-membrane protease serine 2 (TMPRSS2) is essential for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cell entry and infection. Efficacy and safety of TMPRSS2 inhibitors in patients with coronavirus disease 2019 (Covid-19) have not been evaluated in randomized trials.Methods: We conducted an investigator-initiated, double-blind, randomized, placebo-controlled multicenter trial in patients hospitalized with confirmed SARS-CoV-2 infection from April 4, to December 31, 2020. Within 48 h of admission, participants were randomly assigned in a 2:1 ratio to receive the TMPRSS2 inhibitor camostat mesilate 200 mg three times daily for 5 days or placebo. The primary outcome was time to discharge or clinical improvement measured as ≥2 points improvement on a 7-point ordinal scale. Other outcomes included 30-day mortality, safety and change in oropharyngeal viral load.Findings: 137 patients were assigned to receive camostat mesilate and 68 to placebo. Median time to clinical improvement was 5 days (interquartile range [IQR], 3 to 7) in the camostat group and 5 days (IQR, 2 to 10) in the placebo group ( P = 0·31). The hazard ratio for 30-day mortality in the camostat compared with the placebo group was 0·82 (95% confidence interval [CI], 0·24 to 2·79; P = 0·75). The frequency of adverse events was similar in the two groups. Median change in viral load from baseline to day 5 in the camostat group was -0·22 log 10 copies/mL ( p Interpretation: Under this protocol, camostat mesilate treatment was not associated with increased adverse events during hospitalization for Covid-19 and did not affect time to clinical improvement, progression to ICU admission or mortality. ClinicalTrials.gov Identifier: NCT04321096. EudraCT Number: 2020-001200-42.

The novel SARS-CoV-2 infection responsible for the COVID-19 pandemic is expected to have an adverse effect on the progression of multiple cancers, including prostate cancer, due to the ensuing cytokine storm associated oncogenic signaling. A better understanding of the host cell factors and their regulators will help identify potential therapies to block SARS-CoV-2 infection at an early stage and thereby prevent cancer progression. Host cell infection by SARS-CoV-2 requires the binding of the viral spike S protein to ACE2 receptor and priming by the serine protease TMPRSS2—encoded by a well-known androgen response gene and highly expressed in patients diagnosed with prostate cancer. Epidemiologic data showing increased severity and mortality of SARS-CoV-2 disease in men suggest a possible role for androgen in the transcriptional activation of ACE2 and TMPRSS2 in the lungs and other primary infection sites. Here, by performing in vivo castration in mice, RT-PCR, immunoblotting, Co-IP, and pseudovirus infection assays in multiple cell lines, we present evidence for the transcriptional regulation of TMPRSS2 and ACE2 by androgen, their endogenous interaction, as well as a novel combination of drugs in blocking viral infection. In adult male mice, castration led to a significant loss in the expression of ACE2 and TMPRSS2 at the transcript and protein levels in the lung, heart, and small intestine. Intriguingly, castrated mice displayed a substantial increase in ACE2 in the kidney, which could potentially be due to the low blood pressure resulting from androgen deprivation. Endogenous TMPRSS2 and ACE2 were found to be physically interacting, as observed by reciprocal immunoprecipitation followed by immunoblotting. Importantly, along with full-length zymogen form, a prominent novel small isoform of TMPRSS2 was found to be associated with ACE2 in lung and prostate cells. In an overexpression system, camostat—a serine protease inhibitor specific to TMPRSS2—inhibited the cleavage of spike S, suggesting a direct role of this serine protease in priming the viral spike S protein, a prerequisite for an active infection. Furthermore, a combination of camostat, antiandrogen, and epigenetic drugs at sublethal concentrations blocked SARS-CoV-2 pseudovirus infection in multiple cell types. Together, our preclinical data provide a strong rationale for clinical evaluation of TMRPSS2 inhibitors, antiandrogens, and epigenetic drug combinations along with antiviral drug remdesivir as early as clinically possible to prevent progression to pneumonia and multiorgan failure as a result of hyperinflammatory responses in COVID-19 patients. Citation Format: Qu Deng, Reyaz Ur Rasool, Ramakrishnan Natesan, Irfan A. Asangani. Therapeutic targeting of TMPRSS2 and ACE2 as a potential strategy to combat COVID-19 [abstract]. In: Proceedings of the AACR Virtual Meeting: COVID-19 and Cancer; 2020 Jul 20-22. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(18_Suppl):Abstract nr S01-01.

Graphical abstract, Coronavirus Disease 2019 (COVID-19) caused by the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is associated with a crude case fatality rate of about 0.5-10% depending on locality. A few clinically approved drugs, such as remdesivir, chloroquine, hydroxychloroquine, nafamostat, camostat, and ivermectin, exhibited anti-SARS-CoV-2 activity in vitro and/or in a small number of patients. However, their clinical use may be limited by anti-SARS-CoV-2 50% maximal effective concentrations (EC50) that exceeded their achievable peak serum concentrations (Cmax), side effects, and/or availability. To find more immediately available COVID-19 antivirals, we established a two-tier drug screening system that combines SARS-CoV-2 enzyme-linked immunosorbent assay and cell viability assay, and applied it to screen a library consisting 1528 FDA-approved drugs. Cetilistat (anti-pancreatic lipase), diiodohydroxyquinoline (anti-parasitic), abiraterone acetate (synthetic androstane steroid), and bexarotene (antineoplastic retinoid) exhibited potent in vitro anti-SARS-CoV-2 activity (EC50 1.13-2.01µM). Bexarotene demonstrated the highest Cmax:EC50 ratio (1.69) which was higher than those of chloroquine, hydroxychloroquine, and ivermectin. These results demonstrated the efficacy of the two-tier screening system and identified potential COVID-19 treatments which can achieve effective levels if given by inhalation or systemically depending on their pharmacokinetics.

Background Serine proteases act through the proteolytic cleavage of the hemagglutinin (HA) of influenza viruses for the entry of influenza virus into cells, resulting in infection. However, the inhibitory effects of serine protease inhibitors on influenza virus infection of human airway epithelial cells, and on their production of inflammatory cytokines are unclear. Methods Primary cultures of human tracheal epithelial cells were treated with four types of serine protease inhibitors, including camostat, and infected with A/Sendai-H/108/2009/(H1N1) pdm09 or A/New York/55/2004(H3N2). Results Camostat reduced the amounts of influenza viruses in the supernatants and viral RNA in the cells. It reduced the cleavage of an influenza virus precursor protein, HA0, into the subunit HA1. Camostat also reduced the concentrations of the cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-α in the supernatants. Gabexate and aprotinin reduced the viral titers and RNA levels in the cells, and aprotinin reduced the concentrations of TNF-α in the supernatants. The proteases transmembrane protease serine S1 member (TMPRSS) 2 and HAT (human trypsin-like protease: TMPRSS11D), which are known to cleave HA0 and to activate the virus, were detected at the cell membrane and in the cytoplasm. mRNA encoding TMPRSS2, TMPRSS4 and TMPRSS11D was detectable in the cells, and the expression levels were not affected by camostat. Conclusions These findings suggest that human airway epithelial cells express these serine proteases and that serine protease inhibitors, especially camostat, may reduce influenza viral replication and the resultant production of inflammatory cytokines possibly through inhibition of activities of these proteases.

Camostat mesilate is in widespread clinical use mainly to treat chronic pancreatitis, and drug-induced lung injury has not been previously reported. However, pulmonary infiltration with peripheral blood eosinophilia appeared after taking camostat mesilate for ten days. The histological findings showed eosinophilic infiltration into the alveolar space and interstitum, and drug lymphocyte stimulation test of peripheral blood was positive. Both peripheral blood eosinophilia and pulmonary involvements improved two weeks later with the cessation of this drug. To the best of our knowledge, this case is the first report of camostat mesilate-induced acute eosinophilic pneumonia.

Gemäß der Overfill-Hypothese wird die Volumenretention beim nephrotischen Syndrom durch die proteolytische Aktivierung des epithelialen Natriumkanals ausgelöst. Dabei scheinen aberrant filtrierte Serinproteasen, wie beispielsweise Plasmin, eine entscheidende Rolle zu spielen. Ziel dieser Arbeit war es, die Serinproteasen im Urin nephrotischer Mäuse zu hemmen und die Tiere dadurch vor einer Natrium- und Wasserretention zu schützen. Dazu wurde zunächst die Entwicklung charakteristischer klinischer und laborchemischer Veränderungen im proteinurischen Mausmodell untersucht und die Tiere anschließend mit den Serinproteaseinhibitoren Aprotinin, Camostat und Tranexamsäure behandelt. Auf die einmalige Injektion von Doxorubicin entwickelten sich zwei unterschiedliche nephropathische Verlaufsformen. Bei der Form mit nephrotischer Proteinurie (> 120 mg/mg crea) präsentierte sich das Vollbild des nephrotischen Syndroms mit massiver Gewichtszunahme, Hypoproteinämie, Hyperlipidämie und ausgeprägter Natriumretention. Bei Entwicklung einer nichtnephrotischen Proteinurie (< 120 mg/mg crea) waren diese charakteristischen Parameter deutlich milder ausgeprägt. Die Serinproteaseaktivität im Urin stieg bei beiden Formen innerhalb der ersten zehn Tage massiv an. Die Behandlung der Mäuse erfolgte durch die subkutane Implantation von Inhibitor-Pellets. Durch Aprotinin konnte die Gewichtszunahme verhindert, die Natriumausscheidung normalisiert und die Serinproteaseaktivität im Urin nahezu vollständig inhibiert werden. Die Applikation von Camostat und Tranexamsäure hatten keinen Effekt auf diese Parameter. In dieser Arbeit konnte gezeigt werden, dass die Volumenretention im experimentellen nephrotischen Syndrom der Maus mit einer übermäßigen Plasminausscheidung und Natriumretention einhergeht. Durch die Behandlung mit dem Serinproteaseinhibitor Aprotinin konnten Natriumretention und Gewichtszunahme effektiv verhindert werden. Diese Ergebnisse implizieren, dass aberrant filtrierte Serinproteasen im Urin eine kausale Bedeutung für die Entwicklung der Natrium- und Volumenretention beim nephrotischen Syndrom haben.

This paper deals with various aspects of oral insulin delivery system. Insulin is used for the treatment of diabetes mellitus, which is characterized by the elevated glucose level (above the normal range) in the blood stream, that is, hyperglycemia. Oral route of administration of any drug is the most convenient route. Development of oral insulin is still under research. Oral insulin will cause the avoidance of pain during the injection (in subcutaneous administration), anxiety due to needle, and infections which can be developed. Different types of enzyme inhibitors, like sodium cholate, camostat, mesilate, bacitracin, leupeptin, and so forth, have been used to prevent insulin from enzymatic degradation. Subcutaneous route has been used for administration of insulin, but pain and itching at the site of administration can occur. That is why various alternative routes of insulin administration like oral route are under investigation. In this paper authors summarized advancement in insulin delivery with their formulation aspects.

The Middle East respiratory syndrome coronavirus (MERS-CoV) utilizes host proteases for virus entry into lung cells. In the current study, Vero cells constitutively expressing type II transmembrane serine protease (Vero-TMPRSS2 cells) showed larger syncytia at 18 h after infection with MERS-CoV than after infection with other coronaviruses. Furthermore, the susceptibility of Vero-TMPRSS2 cells to MERS-CoV was 100-fold higher than that of non-TMPRSS2-expressing parental Vero cells. The serine protease inhibitor camostat, which inhibits TMPRSS2 activity, completely blocked syncytium formation but only partially blocked virus entry into Vero-TMPRSS2 cells. Importantly, the coronavirus is thought to enter cells via two distinct pathways, one mediated by TMPRSS2 at the cell surface and the other mediated by cathepsin L in the endosome. Simultaneous treatment with inhibitors of cathepsin L and TMPRSS2 completely blocked virus entry into Vero-TMPRSS2 cells, indicating that MERS-CoV employs both the cell surface and the endosomal pathway to infect Vero-TMPRSS2 cells. In contrast, a single camostat treatment suppressed MERS-CoV entry into human bronchial submucosal gland-derived Calu-3 cells by 10-fold and virus growth by 270-fold, although treatment with both camostat and (23,25)- trans -epoxysuccinyl- l -leucylamindo-3-methylbutane ethyl ester, a cathepsin inhibitor, or treatment with leupeptin, an inhibitor of cysteine, serine, and threonine peptidases, was no more efficacious than treatment with camostat alone. Further, these inhibitors were not efficacious against MERS-CoV infection of MRC-5 and WI-38 cells, which were derived from lung, but these characters differed from those of mature pneumocytes. These results suggest that a single treatment with camostat is sufficient to block MERS-CoV entry into a well-differentiated lung-derived cell line.

Protease-antiprotease imbalance and oxidative stress are considered to be major pathophysiological hallmarks of severe obstructive lung diseases including chronic obstructive pulmonary disease (COPD) and cystic fibrosis (CF), but limited information is available on their direct roles in the regulation of pulmonary phenotypes. Here, we utilized βENaC-transgenic (Tg) mice, the previously established mouse model of severe obstructive lung diseases, to produce lower-mortality but pathophysiologically highly useful mouse model by backcrossing the original line with C57/BL6J mice. C57/BL6J-βENaC-Tg mice showed higher survival rates and key pulmonary abnormalities of COPD/CF, including mucous hypersecretion, inflammatory and emphysematous phenotypes and pulmonary dysfunction. DNA microarray analysis confirmed that protease- and oxidative stress-dependent pathways are activated in the lung tissue of C57/BL6J-βENaC-Tg mice. Treatments of C57/BL6J-βENaC-Tg mice with a serine protease inhibitor ONO-3403, a derivative of camostat methylate (CM), but not CM, and with an anti-oxidant N-acetylcystein significantly improved pulmonary emphysema and dysfunction. Moreover, depletion of a murine endogenous antioxidant vitamin C (VC), by genetic disruption of VC-synthesizing enzyme SMP30 in C57/BL6J-βENaC-Tg mice, exaggerated pulmonary phenotypes. Thus, these assessments clarified that protease-antiprotease imbalance and oxidative stress are critical pathways that exacerbate the pulmonary phenotypes of C57/BL6J-βENaC-Tg mice, consistent with the characteristics of human COPD/CF.

Many studies clearly demonstrate inhibition of dietary fat preference by exogenous enterostatins in rodents. However, what role endogenous enterostatin, if any, may play in the regulation of fat intake is not clear. To this end, we examined whether there is a relationship between plasma enterostatin (VPDPR)-like immunoreactivity and fat preference. Additionally, since enterostatin is a product of tryptic cleavage of procolipase, we examined the effect of camostat, a protease inhibitor known to inhibit trypsin and other proteases, on dietary fat preference and plasma enterostatin concentration. The results of these studies show that while there was a significant inverse relationship between plasma enterostatin and fat preference, the effect of camostat on fat preference or plasma enterostatin concentration was not clear.

We have shown that vagotomy (VGX) attenuates the reduction of meal size (MS) produced by cholecystokinin (CCK) -8 and -33 and that celiaco-mesenteric ganglionectomy (CMGX) attenuates the prolongation of the intermeal interval (IMI) produced by CCK-33. Here, we report the following novel data. First, by determining the distribution of CCK 1 receptor messenger RNA, which mediates reduction of MS and prolongation of IMI by CCK, in seven regions of the gastrointestinal tract in the adult rat we found that the duodenum contains the highest concentration of this receptor in the gut. Second, based on the previous finding we performed a unique surgical technique known as duodenal myotomy (MYO), which severs all the nerves of the gut wall in the duodenum including vagus, splanchnic and enteric nerves. Third, we determined MS and IMI in duodenal MYO rats in responses to endogenous CCK-58 released by the non-nutrient, trypsin inhibitor, camostat and CCK-8 to test the possibility that the duodenum is the site of action for reduction of MS and prolongation of IMI. We found that, similar to the previous work reported by using CCK-8 and MS, duodenal MYO also blocked reduction of MS by camostat. Forth, duodenal MYO blocked prolongation of IMI by camostat. As such, our current results suggest that the duodenum is the gut site that communicates both feeding signals of endogenous CCK, MS and IMI, with the brain through vagal and splanchnic afferents.

The type II transmembrane protease TMPRSS2 activates the spike (S) protein of severe acute respiratory syndrome coronavirus (SARS-CoV) on the cell surface following receptor binding during viral entry into cells. In the absence of TMPRSS2, SARS-CoV achieves cell entry via an endosomal pathway in which cathepsin L may play an important role, i.e., the activation of spike protein fusogenicity. This study shows that a commercial serine protease inhibitor (camostat) partially blocked infection by SARS-CoV and human coronavirus NL63 (HCoV-NL63) in HeLa cells expressing the receptor angiotensin-converting enzyme 2 (ACE2) and TMPRSS2. Simultaneous treatment of the cells with camostat and EST [(23,25) trans -epoxysuccinyl- l -leucylamindo-3-methylbutane ethyl ester], a cathepsin inhibitor, efficiently prevented both cell entry and the multistep growth of SARS-CoV in human Calu-3 airway epithelial cells. This efficient inhibition could be attributed to the dual blockade of entry from the cell surface and through the endosomal pathway. These observations suggest camostat as a candidate antiviral drug to prevent or depress TMPRSS2-dependent infection by SARS-CoV.

Camostat mesilate (or mesylate) releases endogenous cholecystokinin (CCK) or CCK-58, the only detectable endocrine form of CCK in the rat, and reduces cumulative food intake by activating CCK(1) receptor. However, the literature lacks meal pattern analysis and an appropriate dose-response curve for this peptide. Therefore, the current study determines meal size (MS), intermeal interval (IMI) and satiety ratio (SR) by orogastric gavage of camostat (0, 12.5, 25, 50, 100, 200, 300, 400, 800mg/kg) and compares them to those previously reported by a single dose of CCK-8 (1nmol/kg, i.p), the most utilized form of CCK. We found that camostat (200, 300, 400 and 800mg/kg) and CCK-8 reduced cumulative food intake and the size of the first meal, but only camostat prolonged IMI and increased SR. There was no change in the duration of the first two meals or in rated behaviors such as feeding, grooming, standing and resting in response to camostat and CCK-8, but there was more resting during the IMI in response to camostat. This study provides meal pattern analysis and an appropriate dose-response curve for camostat and CCK-8. Camostat reduces food intake by decreasing MS and prolonging IMI, whereas CCK-8 reduces food intake by reducing only meal size.

The fragmentation patterns of a serine protease inhibitor, camostat, and its degradation product, 4-(4- guanidinobenzoyloxy)phenylacetic acid (GBPA), were for the first time investigated by a triple quadrupole tandem mass spectrometry equipped with an electrospray source (ESI-MS/MS) in positive and/or negative ion mode under collision-induced dissociation (CID). The positive CID spectrum of camostat showed distinctly that the single bond (C-O) cleavage between carbonyl group and oxygen atom of the ester bonds of the compound favorably occurred and then the loss of N,N-dimethylcarbamoylmethyl group was more susceptible than that of guanidine moiety. In the positive ion CID spectrum of GBPA, the initial cleavage between the carbonyl group and oxygen atom of 4-guanidinobenzoyloxy group also occurred, yielding the most abundant fragment ion at m/z 145. On the other hand, the negative CID spectrum of GBPA characteristically showed the occurrence of the most abundant peak at m/z 226 resulting from the sequential neutral losses of CO₂ and HN=C=NH from the parent ion at m/z 312.