key: cord-0994255-xqp9b1fp
authors: El‐Shimy, Ismail A.; Mohamed, Mahmoud M. A.; Hasan, Syed Shahzad; Hadi, Muhammad A.
title: Targeting host cell proteases as a potential treatment strategy to limit the spread of SARS‐CoV‐2 in the respiratory tract
date: 2020-12-23
journal: Pharmacol Res Perspect
DOI: 10.1002/prp2.698
sha: 9a4638dd5a61b20822ef26f1aeb02b40dbaffa68
doc_id: 994255
cord_uid: xqp9b1fp

As the death toll of Coronavirus disease 19 (COVID‐19) continues to rise worldwide, it is imperative to explore novel molecular mechanisms for targeting SARS‐CoV‐2. Rather than looking for drugs that directly interact with key viral proteins inhibiting its replication, an alternative and possibly add‐on approach is to dismantle the host cell machinery that enables the virus to infect the host cell and spread from one cell to another. Excellent examples of such machinery are host cell proteases whose role in viral pathogenesis has been demonstrated in numerous coronaviruses. In this review, we propose two therapeutic modalities to tackle SARS‐CoV‐2 infections; the first is to transcriptionally modulate the expression of cellular proteases and their endogenous inhibitors and the second is to directly inhibit their enzymatic activity. We present a nonexhaustive collection of clinically investigated drugs that act by one of these mechanisms and thus represent promising candidates for preclinical in vitro testing and hopefully clinical testing in COVID‐19 patients.

homotrimers that are integrated into the viral envelope giving rise to its characteristic corona-shaped structure. 3 It possesses a large ectodomain, a small transmembrane domain, and a short endodomain.

Like all class I viral fusion proteins, the S protein ectodomain is divided into two functional domains: S1 domain which binds to host cell receptors and S2 domain which mediates the fusion between the viral envelope and the host cell membrane. In order for the fusion machinery of the S2 domain to be active, the S protein has to undergo proteolytic processing by a variety of host cell protease enzymes that are able to cleave its ectodomain at a number of specific sites ( Figure 1B) . Two of these cleavage sites have been well characterized in SARS-CoV-1, namely the S1/S2 site at the boundary between these two domains and the S2' site which exists within the S2 domain itself 4 ( Figure 1A ). Likewise, a multibasic cleavage site at the S1/S2 boundary has been characterized in the SARS-CoV-2 S protein. 5 It is worth to mention that these protease-catalyzed cleavage events can take place on the cell surface before viral entry into its host cell, inside endosomes during viral entry and in the cytosol during viral protein synthesis by the infected cell. This is why host cell proteases are believed to play a pivotal role in the pathogenesis of many human coronaviruses as well as other pneumotropic viruses such as influenza.

Here, the focus is on protease enzymes that have been implicated in the proteolytic activation of SARS-CoV-1 and 2 S proteins since both strains were shown to be very similar in terms of genomic sequence homology, infection mechanism and ensuing pathology. 8 These enzymes include trypsin, elastase, thermolysin, cathepsin B, cathepsin L, transmembrane serine proteases (TMPRSS), plasmin, and factor Xa. All of these proteases were reported to cleave the S protein in vitro at the S1/S2 or S2' sites or both. 9 Of particular importance is TMPRSS2 which was shown to associate with ACE2, a host cell receptor for SARS-CoV-1, and form complexes that improve viral entry at the cell surface. 10 Recently, SARS-CoV-2 was also shown to utilize the same ACE2 F I G U R E 1 An illustration of the two cleavage sites of the Spike (S) proteins of SARS-CoV-1 and SARS-CoV-2 and the host cell proteases that can possibly cleave them. (A) Schematic representation of SARS-CoV-1 S protein with its functional domains (RBD, receptor binding domain; RBM, receptor binding motif; TD, transmembrane domain) and its two proteolytic cleavage sites (S1/S2, S2′). Amino acid sequences around the two protease recognition sites (red) are indicated for both S proteins of SARS-CoV-1 and SARS-CoV-2 (asterisks indicate conserved residues). Arrowheads indicate the cleavage site. (copied with permission from Figure 1A by Hoffmann and colleagues 6 ). (B) A table listing host cell proteases that are reported to cleave S proteins of coronaviruses together with their subcellular locations, classification according to the Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-IUBMB) and their common recognition sequences with the cleavage site indicated by a downward arrow. Amino acid residues on the N-terminal end of the cleavage site are designated P1, P2, P3,...etc, while those on the C-terminal end are designated P1', P2', P3',...etc "X" denotes any amino acid residue, "hydrophobic" denotes Ala, Val, Leu, Ile, Phe, Trp or Tyr, "aromatic" denotes Phe, Trp, His or Tyr and "positive" denotes Lys, Arg or His 7 (A) (B) F I G U R E 2 A diagram illustrating the different drug candidates, their targets and mechanisms of action. Host cell proteases depicted here are reported to proteolytically cleave the S protein of coronaviruses which is an essential step to initiate the fusion process between viral and epithelial cell membranes. Three categories of drugs are described; drugs that downregulate the expression of protease enzymes, drugs that directly inhibit their enzymatic activity, and drugs that upregulate the expression of endogenous protease inhibitors. All elements used in this illustration come from the Reactome icon library (https://react ome. org/icon-lib). Protein structures of host cell proteases and protease inhibitors were obtained from UniProt knowledgebase (https:// www.unipr ot.org/) and Protein Data Bank (https://www.rcsb.org/). Abbreviations: TMPRSS, transmembrane serine protease; HDAC, histone deacetylase; HAI-1, hepatocyte growth factor activator inhibitor type 1 receptor for entry and TMPRSS2 protease activity to prime its S protein 6 ( Figure 2 ). In addition, the host cell protease furin was shown to cleave the SARS-CoV-2 S protein at the S1/S2 site which is an essential event for spike-driven viral entry into lung cells. 5 Moreover, the endosomal cysteine proteases cathepsin B and L were found to participate in processing SARS-CoV-1 and 2 S proteins enabling them to be primed even in the absence of TMPRSS2 activity. 6, 11 Beside proteases, host cells are equipped with a collection of natural protease inhibitors that control the activity of many of the above-mentioned proteolytic enzymes such as alpha1 antitrypsin (AAT) which inhibits trypsin and elastase and hepatocyte growth factor activator inhibitor type 1 (HAI-1) and type 2 (HAI-2) which regulate activities of transmembrane serine proteases including TMPRSS2. 12 Interestingly, HAI-2 was reported to inhibit influenza virus H1N1 infection in cell culture, and its administration showed protective effects in a mouse model of influenza. 13 This has been attributed to its effective inhibition of the proteolytic cleavage of influenza virus hemagglutinin (HA) which is another class I viral fusion protein that shares many common features with the coronavirus S protein. Similar to the S protein, HA is synthesized as an intact precursor that gets cleaved by host cell proteases giving rise to two functional subunits HA1 and HA2.

HA1 resembles the S1 domain of S protein where it binds to sialic acid receptors on the host cell surface, while HA2-just as the S2 domain-contains a fusion peptide that gets exposed upon cleavage initiating the fusion process between viral and host cell membranes. 9 Beside HAI-1 and HAI-2, the serine protease inhibitor, plasminogen activator inhibitor 1 (PAI-1) was likewise shown to inhibit HA cleavage and prevent H1N1 influenza virus replication both ex vivo and in vivo. 14 In light of what is known so far about proteases and their inhibitors, two treatment approaches are proposed to control SARS-CoV-2 infections. The first approach is to use transcriptional suppressors that downregulate the expression of protease enzymes on the gene level or alternatively transcriptional activators that enhance the expression of the naturally occurring protease inhibitors.

The second approach is to target host cell proteases directly through the use of small-molecule compounds or proteins that are known to inhibit their enzymatic activity. In this review, we discuss these two approaches and present a number of drug candidates that act by one or more of these mechanisms, and as such have a great potential for clinical use to limit viral infectivity and spread.

One obvious limitation of these targeting approaches is the fact that host cells are equipped with a wide range of proteolytic enzymes-as discussed above-that were found to cleave coronavirus S protein. Targeting one specific enzyme with an inhibiting molecule may not be sufficient to stop viral spread due to the abundance of other proteases. Despite this drawback, it is obvious at least from a number of in vitro and in vivo studies that cleavage of S protein by specific proteases appears to be more important for viral pathogenicity than by others and that inhibiting one of these enzymes can significantly block viral entry into its host cells. One particular example is TMPRSS2 where its inhibition in human lung cell lines clearly blocked their infection with SARS-CoV-2 in vitro. 6 The same concept applies to other kinds of viruses that possess class I viral fusion proteins as influenza A where inhibition of trypsin-like serine proteases using the naturally occurring protease inhibitors HAI-2 and PAI-1 displayed antiviral activity both in vitro and in vivo. 13, 14 Furthermore, combination antiprotease therapy targeting more than one protease enzyme simultaneously is another possibility to enhance the antiviral activity of such drugs. Some drug combinations with acceptable safety profiles are discussed below to serve this purpose.

TMPRSS2 gene expression is known to be activated by the androgen receptor. [15] [16] [17] For this reason, drugs that block this receptor are believed to interfere with TMPRSS2 expression resulting in its downregulation. In line with this, enzalutamide (an androgen receptor antagonist), estradiol, and the phytoestrogen genistein were recently reported to downregulate the expression of TMPRSS2 using RNA sequencing data derived from human prostate, breast, and endometrial cancer cell lines. 18 On the other hand, testosterone and metribolone (a synthetic androgen) were shown to significantly increase its expression in human prostate cancer cells. Consistent with these findings, treatment of prostate cancer cell lines with enzalutamide again resulted in reduced TMPRSS2 mRNA expression measured by real-time quantitative polymerase chain reaction (qPCR). 19 Moreover, fulvestrant (an estrogen receptor antagonist) was found to upregulate TMPRSS2 expression in a breast cancer cell line using single-cell RNA sequencing data. 18 Notably, the authors demonstrated that genes that were highly correlated with TMPRSS2 expression in RNA sequencing data obtained from human lung tissues were significantly enriched for androgen and estrogen response hallmark genes. This provides sound evidence that androgen and estrogen receptors are important transcriptional regulators of TMPRSS2 gene in human lung cells. It is worth mentioning here that estrogen receptor signaling played a protective role in female mice infected with SARS-CoV-1 where ovariectomy or treating the mice with an estrogen receptor antagonist led to increased mortality. 20 Moreover, there is a growing body of evidence suggesting that male sex is a predisposing factor to COVID-19. One possible mechanism that could contribute to this predisposition is the increased expression of transmembrane serine proteases, particularly TMPRSS2, in response to male sex hormones. 21, 22 Regarding their clinical utility, both enzalutamide and estradiol have a well-established clinical profile making them suitable for trial in COVID-19 patients. Enzalutamide is clinically approved for treatment of patients with castration-resistant prostate cancer and metastatic castration-sensitive prostate cancer. 23 The most common adverse effects associated with its use are peripheral edema, hyperglycemia, hyponatremia, hypermagnesemia, upper respiratory tract infection, asthenia, back pain, disturbed bowel movement, and arthralgia. 23 On the other hand, oral administration of estrogen and its synthetic derivatives has long been used for contraception and treatment of menopause-related conditions such as vaginal atrophy and osteoporosis. 24 Adverse effects of systemic estradiol include vaginal hemorrhage, edema, headache, gastrointestinal discomfort, mastalgia, deep vein thrombosis, and nasopharyngitis. 25, 26 Given such toxicity profiles, we propose that enzalutamide can be used at an oral daily dose of 160 mg in male patients especially those with a compelling indication as prostate cancer. Likewise, estradiol combined with a progestin can be administered at an oral daily dose of 1-2 mg to female patients.

5-alpha reductase inhibitors are another class of drugs that influence intracellular androgen signaling and are clinically used to treat conditions with excessive androgen production such as benign prostatic hyperplasia and male pattern hair loss. 27 By inhibiting 5-alpha reductase enzyme, these drugs prevent the conversion of testosterone to the more active dihydrotestosterone and hence attenuate androgen-mediated cellular responses. 27 This in turn can lead to a reduction in the expression of androgen-regulated genes including TMPRSS2. Indeed, treatment with the clinically approved inhibitor dutasteride was found to reduce TMPRSS2 expression in microdissected prostate epithelial tumor tissues as measured by both gene expression microarrays and real-time PCR. 28 This drug also significantly decreased TMPRSS2 staining in the neoplastic prostate epithelium. With regard to its safety, dutasteride is generally well tolerated and causes no serious adverse effects. Its use is associated with decreased libido, ejaculation disorder, and erectile dysfunction, however, these effects are usually mild and decrease over time. 29 In terms of applicability to COVID-19 patients, we propose this drug can be used at an oral daily dose of 0.5 mg. However, it is important to mention that it is contraindicated in pregnant women or women who may become pregnant due to potential risk to a male fetus. 30 

HDAC inhibitors are compounds that inhibit histone deacetylase enzyme which catalyzes the removal of acetyl groups from both histone and nonhistone proteins including transcription factors.

Inhibition of these deacetylation reactions alters the compactness of the chromatin structure and the transcriptional regulation of many genes that control the cell cycle, proliferation, and apoptosis. 31 For this reason, HDAC inhibitors have been used as anticancer drugs. Among the genes whose expression is altered by HDAC inhibition are those encoding the serine protease inhibitors HAI-1 and HAI-2. By querying the connectivity map (CMAP) drug perturbation signatures, 32 we found that the classical HDAC inhibitors apicidin and trichostatin A increased the expression of SPINT1 and SPINT2 genes which encode HAI-1 and HAI-2, respectively, in human lung cancer cell lines as measured by L1000 gene expression assay. Similarly, a number of second-generation HDAC inhibitors (vorinostat, panobinostat, and mocetinostat) were found to increase the expression of one of these two genes or both in the same cell lines.

In the matter of clinical relevance, vorinostat and panobinostat are both clinically approved for treatment of T-cell lymphoma and multiple myeloma, respectively. In terms of safety, the most common adverse effects associated with vorinostat are fatigue, nausea, diarrhea, thrombocytopenia, anorexia, and dysgeusia. Pulmonary embolism, anemia, and squamous cell carcinoma of the skin are more severe toxicities that were reported in less than 5% of patients. 33, 34 Similarly, panobinostat use is linked to asthenia, fatigue, and diarrhea, however, it is also associated with pneumonia, peripheral neuropathy and the more serious myelosuppression which manifests as thrombocytopenia, neutropenia, and lymphopenia. 35 Given the blood toxicity profiles of these drugs, we give them less priority for clinical investigation in COVID-19 despite their seemingly desirable effects on host cell proteases as we believe their risk-benefit ratio does not favor their use.

Long known for their positive inotropic effect, cardiac glycosides have been used for managing patients with cardiac muscle failure for a very long time. However, because of their narrow therapeutic index and relatively high risk of toxicity associated with their prolonged use, their clinical indications are now restricted. 36 Interestingly, these compounds may still provide some benefits for patients with coronavirus infections. By examining a large collection of RNA sequencing data, Wang and colleagues showed that digitalislike compounds including digoxin and proscillaridin A markedly reduced expression of the endosomal cathepsins B and L in human thyroid cancer cells. 37 This effect can limit S protein processing and priming in the endosomal compartments of infected host cells.

Digoxin use has long been associated with gastrointestinal adverse effects, visual disturbances, and cardiovascular toxicity including cardiac arrhythmia, tachycardia, and heart block. 38 Despite its potential for cardiovascular toxicity, we suggest that digoxin can be tested in COVID-19 patients at an oral daily dose of less than 0.125 mg such that its serum concentration is kept below 1 ng/mL.

At such low concentration, digoxin is not only associated with minimal adverse effects, but also exerts beneficial hemodynamic, neurohormonal, and clinical effects in patients with congestive heart failure and other cardiovascular diseases. 39 Accordingly, we encourage testing digoxin in COVID-19 patients with preexisting cardiovascular conditions such as heart failure.

Elastase and other serine proteases released from neutrophils at inflammation sites are believed to play an important role in the patho- 

This alpha globulin glycoprotein is one of the most widely known members of the SERPIN superfamily of serine protease inhibitors.

It is mainly synthesized in the liver by hepatocytes and released into the bloodstream. It is also synthesized by the pancreas, lung alveolar cells, vascular endothelium, and intestinal epithelium. 48 Genetic deficiency of AAT leads to a wide range of pathologies affecting mainly the lungs, liver, and blood vessels. 48 AAT possesses anti-inflammatory, immunomodulatory, and anti-infection activity. It promotes tissue repair and protects tissues from damage induced by proteolytic enzymes released from inflammatory cells. 48 Equally important, AAT inhibits the activity of trypsin and elastase which are known to cleave and activate the S protein of SARS-CoV-1 9 and possibly also SARS-CoV-2. Similar to HNE inhibitors, these properties make AAT a promising candidate for managing COVID-19 patients. 49 Like sivelestat, the toxicity profile of AAT therapy should not limit its use in COVID-19 patients. The most common adverse reactions are typical of intravenous infusion of proteins and include fever, chills, urticaria, nausea, vomiting, and fatigue. 50 Dyspnea, anaphylactic reactions, and exacerbation of heart failure were also reported in patients receiving AAT therapy, however, incidence of these events was rather low. 50 Accordingly, intravenous infusion of AAT at a dose of 60 mg/kg weekly is proposed as another preventative measure that can protect against ARDS and reduce mortality in hospitalized COVID-19 patients.

The clotting protein factor Xa is a serine protease that is derived from the hydrolysis of its precursor factor X which takes place via two principal pathways. 51 The first is the extrinsic pathway which occurs at the surface of a damaged endothelium and macrophages and involves activation of factor X by factor VII/VIIa in association with a membrane-bound cofactor, tissue factor (TF). The second is the intrinsic pathway in which factor X is activated on the platelet surface by a membrane-bound tenase complex comprising factor IXa, its cofactor factor VIIIa, and calcium ions. Factor Xa then activates prothrombin to thrombin eventually leading to blood clotting.

In the context of SARS-CoV-1 infections, factor Xa was found to cleave the viral S protein at the S1/S2 boundary and promote entry into host cells. 52 Hence, drugs that act as inhibitors of factor Xa are considered protective against S protein priming and viral entry.

Three factor Xa inhibitors (rivaroxaban, apixaban, and edoxaban) are now approved as novel oral anticoagulants and can be used as a replacement for the vitamin K antagonist warfarin. 53 Given that COVID-19-associated coagulopathy (CAC) has been reported in several studies, 54 Note: Indications denoted by * are FDA approved and those denoted by † are currently under investigation. Information concerning clinical indications and available routes of administration was obtained from the DrugBank online database (https://www.drugb ank.com/). **All clinical trial information for the drug candidates was obtained from ClinicalTrials.gov, number of clinical trials and their identifiers are specified whenever applicable (https://clini caltr ials.gov/, accessed 17 November 2020).

can act by a dual mechanism; by inhibiting viral entry and preventing CAC. 65 

An additional set of small molecule and protein inhibitors of serine proteases, especially TMPRSS2, have been thoroughly reviewed. 66 Of particular importance are the two TMPRSS2 inhibitors camostat and nafamostat mesilate. Camostat has shown remarkable in vitro in mouse models. [69] [70] [71] It was also recently shown that camostat can block SARS-CoV-2 entry into human lung cancer cells and therefore constitutes a potential therapeutic option. 6 Interestingly, nafamostat was found to be more effective than camostat in blocking MERS-CoV entry and replication in host cells. 72 Another specific TMPRSS2 inhibitor with great potential is the mucolytic agent bromhexine hydrochloride 73 whose high safety profile makes it an ex- (Table 1 ). In addition to TMPRSS2 inhibitors, the endosomal cathepsin L inhibitor teicoplanin is considered a potential antibiotic for treating secondary bacterial infections associated with SARS-CoV-2. The adverse effects most frequently associated with teicoplanin treatment are local and hypersensitivity reactions, such as itching and drug fever; anaphylactic reactions including the "red man syndrome" are uncommon. Teicoplanin is also less likely than vancomycin to cause nephrotoxicity, especially when administered in combination with an aminoglycoside. 91-93

As discussed earlier, combinatorial protease-targeting therapy is propounded to tackle the problem of redundancy of host cell proteases that can process and activate coronavirus S protein.

Targeting more than one protease enzyme using a drug combination is likely to be more effective in combating viral spread than inhibiting just a single enzyme. We propose here a number of protease-targeting drug combinations that we believe would provide potential therapeutic benefit for hospitalized COVID- Dexamethasone (which inhibits cathepsins B and L 83,84 ) can be added to these combinations once the patient develops a severe respiratory deficit and requires oxygen support since this drug has already been shown to reduce mortality in this particular clinical scenario. 97 Another potential candidate to add to such combinations is the oral secretolytic agent bromhexine hydrochloride which showed inhibitory activity against TMPRSS2 and is generally safe to use. 73 [111] [112] [113] [114] [115] [116] Most of the trials are of small sample size and show either no benefit or only a mild reduction in time to symptoms resolution with low certainty. 117 A recent large-sized trial showed that lopinavir-ritonavir combination has no significant effect on the 28-day mortality, duration of hospital stay, risk of progression to invasive mechanical ventilation or death. 115 Consequently, the evidence available so far does not support the use of lopinavir-ritonavir combination for treating hospitalized COVID-19 patients.

Taken together, the results of all these clinical trials of antiviral drugs clearly emphasize the need for alternative approaches to treat SARS-CoV-2 infections. One such approach discussed extensively in this review is targeting host cell protease enzymes, which we believe is worth exploring.

In summary, we emphasize the importance of host cell proteases as potential drug targets for the treatment of SARS-CoV-2 infection and highlight therapeutic mechanisms that have not been sufficiently exploited to impair the virus capacity to spread through its host cells. We present a collection of clinically approved drugs as well as drugs under investigation that either suppress the transcription of proteases or increase the expression of their natural protease inhibitors. We also include drugs that are reported to possess protease inhibitory activity. These are believed to be potential candidates for drug repurposing and immediate preclinical testing in cell line models to verify their efficacy. As many of these candidates have been in clinical use for several years and their safety profiles are well established, we encourage their rapid clinical testing in patients with COVID-19 in combination with antiviral drugs. This would constitute a two-hit approach where not only viral proteins/enzymes necessary for viral replication are targeted but also the host cell machinery that the virus takes advantage of to facilitate its propagation in its infected host.

Key protein targets and ligands in this article are hyperlinked to corresponding entries in http://www.guide topha rmaco logy.

org, the common portal for data from the IUPHAR/BPS Guide to PHARMACOLOGY, 118 and are permanently archived in the Concise

Guide to PHARMACOLOGY 2019/20. 119

None.

IAS and MMAM conceptualized the idea in consultation with MAH.

IAS and MMAM reviewed literature and wrote the initial draft.

MAH and SSH critically reviewed the initial draft and expanded certain sections of the review. All authors contributed to revising the manuscript in view of reviewers' comments. All authors have read and approved the final version for publication.

Data sharing is not applicable to this article as no new data were created or analyzed in this study.

Ismail A. El-Shimy https://orcid.org/0000-0003-0587-5140

Syed Shahzad Hasan https://orcid.org/0000-0002-4058-2215

Muhammad A. Hadi https://orcid.org/0000-0003-0108-7833

COVID-19) outbreak. World Health Organization (WHO)

Covid-19, angiogenesis, and ARDS endotypes

Mechanisms of coronavirus cell entry mediated by the viral spike protein

Activation of the SARS coronavirus spike protein via sequential proteolytic cleavage at two distinct sites

A multibasic cleavage site in the spike protein of SARS-CoV-2 is essential for infection of human lung cells

SARS-CoV-2 cell entry depends on ACE2 and TMPRSS2 and is blocked by a clinically proven protease inhibitor

Handbook of Proteolytic Enzymes

Systematic comparison of two animal-to-human transmitted human coronaviruses: SARS-CoV-2 and SARS-CoV

Host cell proteases: critical determinants of coronavirus tropism and pathogenesis

A transmembrane serine protease is linked to the severe acute respiratory syndrome coronavirus receptor and activates virus entry

Inhibitors of cathepsin L prevent severe acute respiratory syndrome coronavirus entry

Hepatocyte growth factor activator inhibitors (HAI-1 and HAI-2): emerging key players in epithelial integrity and cancer: HAI-1 and HAI-2 in epithelial integrity

Inhibition of influenza virus infection and hemagglutinin cleavage by the protease inhibitor HAI-2

A serpin shapes the extracellular environment to prevent influenza A virus maturation

Regulation of androgen-responsive transcription by the chromatin remodeling factor CHD8

TMPRSS2-ERG expression predicts prostate cancer survival and associates with stromal biomarkers

Prostate cancer stem cells: do they have a basal or luminal phenotype? Horm Cancer

TMPRSS2 transcriptional inhibition as a therapeutic strategy for COVID-19

Acquired resistance to the second-generation androgen receptor antagonist enzalutamide in castration-resistant prostate cancer

Sex-based differences in susceptibility to severe acute respiratory syndrome coronavirus infection

Severe obesity, increasing age and male sex are independently associated with worse in-hospital outcomes, and higher in-hospital mortality

Sex difference and smoking predisposition in patients with COVID-19

Xtandi (enzalutamide)

Estrogens and progestins: background and history, trends in use, and guidelines and regimens approved by the US Food and Drug Administration

Wyeth Laboratories Inc. Alesse (levonorgestrel and ethinyl estradiol)

Food and Drug Administration (FDA) website

An overview on 5α-reductase inhibitors

Variability in the androgen response of prostate epithelium to 5-reductase inhibition: implications for prostate cancer chemoprevention

Adverse effects and safety of 5-alpha reductase inhibitors (Finasteride, Dutasteride): a systematic review

Avodart (dutasteride)

HDAC inhibitors in cancer biology: emerging mechanisms and clinical applications

A next generation connectivity map: L1000 platform and the first 1,000,000 profiles

Vorinostat: a novel therapy for the treatment of cutaneous T-cell lymphoma

Panobinostat: a review in relapsed or refractory multiple myeloma

Novel therapeutic applications of cardiac glycosides

TMPRSS2 transcriptional inhibition as a therapeutic strategy for COVID-19

Digoxin: clinical highlights: a review of digoxin and its use in contemporary medicine

Digoxin in the management of cardiovascular disorders

Neutrophil elastase inhibitors

The role of neutrophil elastase inhibitors in lung diseases

The role of neutrophil elastase in acute lung injury

Elastase-mediated activation of the severe acute respiratory syndrome coronavirus spike protein at discrete sites within the S2 domain

Protease-mediated enhancement of severe acute respiratory syndrome coronavirus infection

Clinical utility of the neutrophil elastase inhibitor sivelestat for the treatment of acute respiratory distress syndrome

Neutrophil elastase inhibitor (sivelestat) may be a promising therapeutic option for management of acute lung injury/acute respiratory distress syndrome or disseminated intravascular coagulation in COVID-19

Neutrophil Elastase Inhibitors: a potential prophylactic treatment option for SARS-CoV-2-induced respiratory complications?

Therapeutic potential of alpha-1 antitrypsin in human disease

In plain sight: the role of alpha-1-antitrypsin in COVID-19 pathogenesis and therapeutics

Safety and efficacy of alpha-1-antitrypsin augmentation therapy in the treatment of patients with alpha-1-antitrypsin deficiency

Overview of the coagulation system

Cleavage of spike protein of SARS coronavirus by protease factor Xa is associated with viral infectivity

Novel oral factor Xa and thrombin inhibitors in the management of thromboembolism

Endothelial cell infection and endotheliitis in COVID-19

Pulmonary vascular endothelialitis, thrombosis, and angiogenesis in covid-19

Current overview on hypercoagulability in COVID-19

Anticoagulation, mortality, bleeding and pathology among patients hospitalized with COVID-19: a single health system study

Or Institute for Research and Education

Identifier NCT04485429, Efficacy Assessment of Methylprednisolone and Heparin in Patients With COVID-19 Pneumonia

Heparins for Thromboprophylaxis in COVID-19 Patients: HETHICO Study in Veneto (HETHICO)

5?term=hepar in&cond=Covid 19&draw=2&rank=4. 2020. 60. Alex Spyropoulos

Prophylactic Or Intermediate Dose Heparin in High Risk COVID-19 Patients

Identifier NCT04505774, Anti-thrombotics for Adults Hospitalized With COVID-19

Identifier NCT04372589, Antithrombotic Therapy to Ameliorate Complications of COVID-19 ( ATTACC )

University of Sao Paulo General Hospital. ClinicalTrials. gov

National Library of Medicine (US). Identifier NCT04487990, CoV-Hep Study: Regional Anticoagulation Modalities in Continuous Venous Venous Hemodialysis in Patients With COVID-19. ClinicalTrials

Identifier NCT04344756, Trial Evaluating Efficacy and Safety of Anticoagulation in Patients With COVID-19 Infection, Nested in the Corimmuno-19 Cohort (CORIMMUNO-COAG)

The procoagulant pattern of patients with COVID-19 acute respiratory distress syndrome

TMPRSS2: a potential target for treatment of influenza virus and coronavirus infections

The serine protease inhibitor camostat inhibits influenza virus replication and cytokine production in primary cultures of human tracheal epithelial cells

Middle east respiratory syndrome coronavirus infection mediated by the transmembrane serine protease TMPRSS2

Protease inhibitors targeting coronavirus and filovirus entry

Evaluation of anti-influenza effects of camostat in mice infected with non-adapted human influenza viruses

Inhibition of lung serine proteases in mice: a potentially new approach to control influenza infection

Identification of nafamostat as a potent inhibitor of middle east respiratory syndrome coronavirus S protein-mediated membrane fusion using the splitprotein-based cell-cell fusion assay

The androgen-regulated protease TMPRSS2 activates a proteolytic cascade involving components of the tumor microenvironment and promotes prostate cancer metastasis

MDCK cells that express proteases TMPRSS2 and HAT provide a cell system to propagate influenza viruses in the absence of trypsin and to study cleavage of HA and its inhibition

Aprotinin aerosol treatment of influenza and paramyxovirus bronchopneumonia of mice

Aprotinin and similar protease inhibitors as drugs against influenza

Cathepsin L-selective inhibitors: a potentially promising treatment for COVID-19 patients

Effects of some antituberculous and anti-leprotic drugs on cathepsins B, H and L

Glycopeptide antibiotics potently inhibit cathepsin L in the late endosome/lysosome and block the entry of ebola virus, Middle East Respiratory Syndrome Coronavirus (MERS-CoV), and Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV)

Teicoplanin potently blocks the cell entry of 2019-nCoV

Cathepsin L promotes vascular intimal hyperplasia after arterial injury

Astaxanthin intake attenuates muscle atrophy caused by immobilization in rats

Modulatory effect of dexamethasone on ornithine decarboxylase activity and gene expression: a possible post-transcriptional regulation by a neutral metalloprotease

Low-dose dexamethasone prevents endotoxaemia-induced muscle protein loss and impairment of carbohydrate oxidation in rat skeletal muscle

Remdesivir and chloroquine effectively inhibit the recently emerged novel coronavirus (2019-nCoV) in vitro

Simulating henipavirus multicycle replication in a screening assay leads to identification of a promising candidate for therapy

Effect of hydroxychloroquine in hospitalized patients with COVID-19: preliminary results from a multi-centre, randomized, controlled trial. medRxiv

Solidarity' clinical trial for COVID-19 treatments

Efficacy of camostat mesilate against dyspepsia associated with non-alcoholic mild pancreatic disease

Continuous regional arterial infusion versus intravenous administration of the protease inhibitor nafamostat mesilate for predicted severe acute pancreatitis: a multicenter, randomized, open-label, phase 2 trial

A risk-benefit assessment of teicoplanin in the treatment of infections

The comparative efficacy and safety of teicoplanin and vancomycin

Comparative efficacy and safety of vancomycin versus teicoplanin: systematic review and meta-analysis

Effect of camostat mesilate on the expression of pancreatitis-associated protein (PAP), p8, and cytokines in rat spontaneous chronic pancreatitis

Camostat mesilate attenuates pancreatic fibrosis via inhibition of monocytes and pancreatic stellate cells activity

Efficacy of camostat mesilate against chronic upper abdominal pain associated with mild chronic pancreatitis

Dexamethasone in hospitalized patients with Covid-19 -preliminary report

Repurposing of the anti-malaria drug chloroquine for Zika Virus treatment and prophylaxis

FDA-approved drug, prevents zika virus infection and its associated congenital microcephaly in mice

Effect of neutrophil elastase inhibitor (Sivelestat Sodium) in the treatment of Acute Lung Injury (ALI) and Acute Respiratory Distress Syndrome (ARDS): a systematic review and meta-analysis

rAAt (dermatological) Arriva/ProMetic

rAAt (inhaled) arriva/hyland immuno

Identifier NCT00287391, Camostat and Artemisia Annua vs Placebo in COVID-19 Outpatients

Identifier NCT04353284, Camostat Mesylate in COVID-19 Outpatients

National Library of Medicine (US). Identifier NCT04524663, Oral Camostat Compared With Standard Supportive Care in Mild COVID-19 Patients (COPS-2002). ClinicalTrials.gov https:// clini caltr ials

Identifier NCT04455815, A Trial Looking at the Use of Camostat to Reduce Progression of Symptoms of Coronavirus (COVID-19) in People Who Have Tested Positive But Are Able to Stay at Home. ClinicalTrials.gov https:// clini caltr ials

Remdesivir in adults with severe COVID-19: a randomised, double-blind, placebo-controlled, multicentre trial

Remdesivir for the treatment of Covid-19-final report

Remdesivir for 5 or 10 Days in Patients with Severe Covid-19

Effect of remdesivir vs standard care on clinical status at 11 days in patients with moderate COVID-19: a randomized clinical trial

A trial of lopinavir-ritonavir in adults hospitalized with severe covid-19

Efficacy and safety of lopinavir/ritonavir or arbidol in adult patients with mild/moderate COVID-19: an exploratory randomized controlled trial

No statistically apparent difference in antiviral effectiveness observed among ribavirin plus interferon-alpha, lopinavir/ritonavir plus interferon-alpha, and ribavirin plus lopinavir/ritonavir plus interferon-alpha in patients with mild to moderate coronavirus disease 2019: results of a randomized, Open-Labeled Prospective Study

Triple combination of interferon beta-1b, lopinavir-ritonavir, and ribavirin in the treatment of patients admitted to hospital with COVID-19: an open-label, randomised, phase 2 trial

Lopinavir-ritonavir in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial

Treating COVID-19 with chloroquine

Drug treatments for covid-19: living systematic review and network meta-analysis

The IUPHAR/BPS Guide to PHARMACOLOGY in 2018: updates and expansion to encompass the new guide to IMMUNOPHARMACOLOGY

THE CONCISE GUIDE TO PHARMACOLOGY 2019/20: enzymes

Targeting host cell proteases as a potential treatment strategy to limit the spread of SARS-CoV-2 in the respiratory tract