Cysteine focused covalent inhibitors against the main protease of SARS-CoV-2

Recent advances in the design of small molecular drugs with acrylamides covalent warheads

In the development of covalent inhibitors, acrylamides warhead is one of the most popular classes of covalent warheads. In recent years, researchers have made different structural modifications to acrylamides warheads, resulting in the creation of fluorinated acrylamide warheads and cyano acrylamide warheads. These new warheads exhibit superior selectivity, intracellular accumulation, and pharmacokinetic properties. Additionally, although ketoamide warheads have been applied in the design of covalent inhibitors for viral proteins, it has not received sufficient attention. Combined with the studies in kinase inhibitors and antiviral drugs, this review presents the structural features and the progression of acrylamides warheads, offering a perspective on future research and development in this field.

Discovery and characterization of naturally occurring covalent inhibitors of SARS-CoV-2 Mpro from the antiviral herb Ephedra

The Chinese herb Ephedra (also known as Mahuang) has been extensively utilized for the prevention and treatment of coronavirus-induced diseases, including coronavirus disease 2019 (COVID-19). However, the specific anti-SARS-CoV-2 compounds and mechanisms have not been fully elucidated. The main protease (Mpro) of SARS-CoV-2 is a highly conserved enzyme responsible for proteolytic processing during the viral life cycle, making it a critical target for the development of antiviral therapies. This study aimed to identify naturally occurring covalent inhibitors of SARS-CoV-2 Mpro from Ephedra and to investigate their covalent binding sites. The results demonstrated that the non-alkaloid fraction of Ephedra (ENA) exhibited a potent inhibitory effect against the SARS-CoV-2 Mpro effect, whereas the alkaloid fraction did not. Subsequently, the chemical constituents in ENA were identified, and the major constituents' anti-SARS-CoV-2 Mpro effects were evaluated. Among the tested constituents, herbacetin (HE) and gallic acid (GA) were found to inhibit SARS-CoV-2 Mpro in a time- and dose-dependent manner. Their combination displayed a significant synergistic effect on this key enzyme. Additionally, various techniques, including inhibition kinetic assays, chemoproteomic methods, and molecular dynamics simulations, were employed to further elucidate the synergistic anti-Mpro mechanisms of the combination of HE and GA. Overall, this study deciphers the naturally occurring covalent inhibitors of SARS-CoV-2 Mpro from Ephedra and characterizes their synergistic anti-Mpro synergistic effect, providing robust evidence to support the anti-coronavirus efficacy of Ephedra.

Inhibitors of SARS-CoV-2 Main Protease (Mpro) as Anti-Coronavirus Agents

The main protease (Mpro) of SARS-CoV-2 is an essential enzyme that plays a critical part in the virus's life cycle, making it a significant target for developing antiviral drugs. The inhibition of SARS-CoV-2 Mpro has emerged as a promising approach for developing therapeutic agents to treat COVID-19. This review explores the structure of the Mpro protein and analyzes the progress made in understanding protein-ligand interactions of Mpro inhibitors. It focuses on binding kinetics, origin, and the chemical structure of these inhibitors. The review provides an in-depth analysis of recent clinical trials involving covalent and non-covalent inhibitors and emerging dual inhibitors targeting SARS-CoV-2 Mpro. By integrating findings from the literature and ongoing clinical trials, this review captures the current state of research into Mpro inhibitors, offering a comprehensive understanding of challenges and directions in their future development as anti-coronavirus agents. This information provides new insights and inspiration for medicinal chemists, paving the way for developing more effective Mpro inhibitors as novel COVID-19 therapies.

Recent advances towards natural plants as potential inhibitors of SARS-Cov-2 targets

CONTEXT

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is still ongoing and currently the most striking epidemic disease. With the rapid global spread of SARS-CoV-2 variants, new antivirals are urgently needed to avert a more serious crisis. Inhibitors from traditional medicines or natural plants have shown promising results to fight COVID-19 with different mechanisms of action.

OBJECTIVES

To provide comprehensive and promising approaches to the medical community in the fight against this epidemic by reviewing potential plant-derived anti-SARS-CoV-2 inhibitors.

METHODS

Structural databases such as TCMSP (http://lsp.nwu.edu.cn/tcmsp.php), TCM Database @ Taiwan (http://tcm.cmu.edu.tw/), BATMAN-TCM (http://bionet.ncpsb.org/batman-tcm/) and TCMID (http://www.megabionet.org/tcmid/), as well as PubMed, Sci Finder, Research Gate, Science Direct, CNKI, Web of Science and Google Scholar were searched for relevant articles on TCMs and natural products against SARS-CoV-2.

RESULTS

Seven traditional Chinese medicines formulas have unique advantages in regulating the immune system for treating COVID-19. The plant-derived natural compounds as anti-SARS-CoV-2 inhibitors were identified based on 5 SARS-CoV-2 key proteins, namely, angiotensin-converting enzyme 2 (ACE2), 3 C-like protease (3CLpro), papain-like protease (PLpro), spike (S) protein, and nucleocapsid (N) protein.

CONCLUSIONS

A variety of natural products, such as flavonoids, terpenoids, phenols, and alkaloids, were identified, which could be used as potential SASR-Cov-2 inhibitors. These shed new light on the efficient discovery of SASR-Cov-2 inhibitors from natural products.

Discovery of the covalent SARS-CoV-2 Mpro inhibitors from antiviral herbs via integrating target-based high-throughput screening and chemoproteomic approaches

The main proteases (Mpro ) are highly conserved cysteine-rich proteins that can be covalently modified by numerous natural and synthetic compounds. Herein, we constructed an integrative approach to efficiently discover covalent inhibitors of Mpro from complex herbal matrices. This work begins with biological screening of 60 clinically used antiviral herbal medicines, among which Lonicera japonica Flos (LJF) demonstrated the strongest anti-Mpro effect (IC50  = 37.82 μg/mL). Mass spectrometry (MS)-based chemical analysis and chemoproteomic profiling revealed that LJF extract contains at least 50 constituents, of which 22 exhibited the capability to covalently modify Mpro . We subsequently verified the anti-Mpro effects of these covalent binders. Gallic acid and quercetin were found to potently inhibit severe acute respiratory syndrome coronavirus 2 Mpro in dose- and time- dependent manners, with the IC50 values below 10 µM. The inactivation kinetics, binding affinity and binding mode of gallic acid and quercetin were further characterized by fluorescence resonance energy transfer, surface plasmon resonance, and covalent docking simulations. Overall, this study established a practical approach for efficiently discovering the covalent inhibitors of Mpro from herbal medicines by integrating target-based high-throughput screening and MS-based assays, which would greatly facilitate the discovery of key antiviral constituents from medicinal plants.

Computational study on the mechanisms of inhibition of SARS-CoV-2 Mpro by aldehyde warheads based on DFT

SARS-CoV-2 main protease, Mpro, plays a crucial role in the virus replication cycle, making it an important target for antiviral research. In this study, a simplified model obtained through truncation is used to explore the reaction mechanism of aldehyde warhead compounds inhibiting Mpro at the level of density functional theory. According to the calculation results, proton transfer (P_T)-nucleophilic attack (N_A) is the rate-determining step in the entire reaction pathway. The water molecule that plays a catalytic role occupies the oxyanion hole, which is unfavorable for the aldehyde warhead to approach the Cys145 SH. Through a hypothetical study of substituting the main chain NH with methylene, it is further confirmed that the P_T-N_A is a proton transfer-dominated process accompanied by a nucleophilic attack reaction. In this process, the oxyanion hole serves only to stabilize the aldehyde oxygen anion and therefore does not have a significant impact on the activation free energy barrier of the step. Our research results provide a unique perspective for understanding the covalent inhibition reaction of the Mpro active site. This study also offers theoretical guidance for the design of new Mpro covalent inhibitors.

Docking covalent targets for drug discovery: stimulating the computer-aided drug design community of possible pitfalls and erroneous practices

The continuous approval of covalent drugs in recent years for the treatment of diseases has led to an increased search for covalent agents by medicinal chemists and computational scientists worldwide. In the computational parlance, molecular docking which is a popular tool to investigate the interaction of a ligand and a protein target, does not account for the formation of covalent bond, and the increasing application of these conventional programs to covalent targets in early drug discovery practice is a matter of utmost concern. Thus, in this comprehensive review, we sought to educate the docking community about the realization of covalent docking and the existence of suitable programs to make their future virtual-screening events on covalent targets worthwhile and scientifically rational. More interestingly, we went beyond the classical description of the functionality of covalent-docking programs down to selecting the 'best' program to consult with during a virtual-screening campaign based on receptor class and covalent warhead chemistry. In addition, we made a highlight on how covalent docking could be achieved using random conventional docking software. And lastly, we raised an alert on the growing erroneous molecular docking practices with covalent targets. Our aim is to guide scientists in the rational docking pursuit when dealing with covalent targets, as this will reduce false-positive results and also increase the reliability of their work for translational research.

Discovery and characterization of the covalent SARS-CoV-2 3CLpro inhibitors from Ginkgo biloba extract via integrating chemoproteomic and biochemical approaches

BACKGROUND

The 3C-like proteases (3CL^pros) are cysteine-rich homodimeric proteins and can be covalently modified by numerous natural and synthetic compounds, which in turn, block the proteolytic activity or the formation of enzymatically active dimeric forms. Although herbal medicines have been widely used to treat COVID-19, identification of the key herbal constituents that can covalently modify the 3CL^pros in β-coronaviruses (CoVs) remains a big challenge.

AIMS

To construct a comprehensive approach for efficient discovering the covalent SARS-CoV-2 3CL^pro inhibitors from herbal medicines. To decipher the key anti-SARS-CoV-2 3CL^pro constituents in Ginkgo biloba extract 50 (GBE50) and to study their anti-SARS-CoV-2 3CL^pro mechanisms.

METHODS

SARS-CoV-2 3CL^pro inhibition assay including time-dependent inhibition assays and inactivation kinetic analyses were conducted using a fluorescence-based biochemical assay. The constituents in GBE50 were analyzed by UHPLC-Q-Exactive Orbitrap HRMS. The peptides modified by herbal constituents were characterized by using nanoLC-MS/MS.

RESULTS

Following testing the anti-SARS-CoV-2 3CL^pro effects of 104 herbal medicines, it was found that Ginkgo biloba extract 50 (GBE50) potently inhibited SARS-CoV-2 3CL^pro in dose- and time-dependent manners. A total of 38 constituents were identified from GBE50 by UHPLC-Q-Exactive Orbitrap HRMS, while 26 peptides modified by 18 constituents were identified by chemoproteomic profiling. The anti-SARS-CoV-2 3CL^pro effects of 18 identified covalent inhibitors were then validated by performing time-dependent inhibition assays. The results clearly demonstrated that most tested constituents showed time-dependent inhibition on SARS-CoV-2 3CL^pro, while gallocatechin and sciadopitysin displayed the most potent anti-SARS-CoV-2 3CL^pro effects.

CONCLUSION

Collectively, GBE50 and some constituents in this herbal product could strongly inhibit SARS-CoV-2 3CL^pro in dose- and time-dependent manner. Gallocatechin and sciadopitysin were identified as potent SARS-CoV-2 3CL^pro inhibitors, which offers promising lead compounds for the development of novel anti-SARS-CoV-2 drugs.

In Silico Design of New Dual Inhibitors of SARS-CoV-2 MPRO through Ligand- and Structure-Based Methods

The viral main protease is one of the most attractive targets among all key enzymes involved in the life cycle of SARS-CoV-2. Considering its mechanism of action, both the catalytic and dimerization regions could represent crucial sites for modulating its activity. Dual-binding the SARS-CoV-2 main protease inhibitors could arrest the replication process of the virus by simultaneously preventing dimerization and proteolytic activity. To this aim, in the present work, we identified two series' of small molecules with a significant affinity for SARS-CoV-2 M^PRO, by a hybrid virtual screening protocol, combining ligand- and structure-based approaches with multivariate statistical analysis. The Biotarget Predictor Tool was used to filter a large in-house structural database and select a set of benzo[b]thiophene and benzo[b]furan derivatives. ADME properties were investigated, and induced fit docking studies were performed to confirm the DRUDIT prediction. Principal component analysis and docking protocol at the SARS-CoV-2 M^PRO dimerization site enable the identification of compounds 1b,c,i,l and 2i,l as promising drug molecules, showing favorable dual binding site affinity on SARS-CoV-2 M^PRO.

Mechanistic investigation of SARS-CoV-2 main protease to accelerate design of covalent inhibitors

Targeted covalent inhibition represents one possible strategy to block the function of SARS-CoV-2 Main Protease (M^PRO), an enzyme that plays a critical role in the replication of the novel SARS-CoV-2. Toward the design of covalent inhibitors, we built a covalent inhibitor dataset using deep learning models followed by high throughput virtual screening of these candidates against M^PRO. Two top-ranking inhibitors were selected for mechanistic investigations-one with an activated ester warhead that has a piperazine core and the other with an acrylamide warhead. Specifically, we performed a detailed analysis of the free energetics of covalent inhibition by hybrid quantum mechanics/molecular mechanics simulations. Cleavage of a fragment of the non-structured protein (NSP) from the SARS-CoV-2 genome was also simulated for reference. Simulations show that both candidates form more stable enzyme-inhibitor (E-I) complexes than the chosen NSP. It was found that both the NSP fragment and the activated ester inhibitor react with CYS145 of M^PRO in a concerted manner, whereas the acrylamide inhibitor follows a stepwise mechanism. Most importantly, the reversible reaction and the subsequent hydrolysis reaction from E-I complexes are less probable when compared to the reactions with an NSP fragment, showing promise for these candidates to be the base for efficient M^PRO inhibitors.

Targeting SARS-CoV-2 Main Protease for Treatment of COVID-19: Covalent Inhibitors Structure-Activity Relationship Insights and Evolution Perspectives

The viral main protease is one of the most attractive targets among all key enzymes involved in the SARS-CoV-2 life cycle. Covalent inhibition of the cysteine145 of SARS-CoV-2 MPRO with selective antiviral drugs will arrest the replication process of the virus without affecting human catalytic pathways. In this Perspective, we analyzed the in silico, in vitro, and in vivo data of the most representative examples of covalent SARS-CoV-2 MPRO inhibitors reported in the literature to date. In particular, the studied molecules were classified into eight different categories according to their reactive electrophilic warheads, highlighting the differences between their reversible/irreversible mechanism of inhibition. Furthermore, the analyses of the most recurrent pharmacophoric moieties and stereochemistry of chiral carbons were reported. The analyses of noncovalent and covalent in silico protocols, provided in this Perspective, would be useful for the scientific community to discover new and more efficient covalent SARS-CoV-2 MPRO inhibitors.

Molecular interactions and inhibition of the SARS‐CoV‐2 main protease by a thiadiazolidinone derivative

We report molecular interactions and inhibition of the main protease (M^Pro) of SARS‐CoV‐2, a key enzyme involved in the viral life cycle. By using a thiadiazolidinone (TDZD) derivative as a chemical probe, we explore the conformational dynamics of M^Pro via docking protocols and molecular dynamics simulations in all‐atom detail. We reveal the local and global dynamics of M^Pro in the presence of this inhibitor and confirm the inhibition of the enzyme with an IC₅₀ value of 1.39 ± 0.22 μM, which is comparable to other known inhibitors of this enzyme.

Combined Computational NMR and Molecular Docking Scrutiny of Potential Natural SARS-CoV-2 Mpro Inhibitors

In continuation of the search for potential drugs that inhibit the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), in this work, a combined approach based on the modeling of NMR chemical shifts and molecular docking is suggested to identify the possible suppressors of the main protease of this virus among a number of natural products of diverse nature. Primarily, with the aid of an artificial neural network, the problem of the reliable determination of the stereochemical structure of a number of studied compounds was solved. Complementary to the main goal of this study, theoretical modeling of NMR spectral parameters made it feasible to perform a number of signal reassignments together with introducing some missing NMR data. Finally, molecular docking formalism was applied to the analysis of several natural products that could be chosen as prospective candidates for the role of potential inhibitors of the main protease. The results of this study are believed to assist in further research aimed at the development of specific drugs based on the natural products against COVID-19.

Identification of a dual acting SARS-CoV-2 proteases inhibitor through in silico design and step-by-step biological characterization

COVID-19 pandemic, starting from the latest 2019, and caused by SARS-CoV-2 pathogen, led to the hardest health-socio-economic disaster in the last century. Despite the tremendous scientific efforts, mainly focused on the development of vaccines, identification of potent and efficient anti-SARS-CoV-2 therapeutics still represents an unmet need. Remdesivir, an anti-Ebola drug selected from a repurposing campaign, is the only drug approved, so far, for the treatment of the infection. Nevertheless, WHO in later 2020 has recommended against its use in COVID-19. In the present paper, we describe a step-by-step in silico design of a small library of compounds as main protease (M^pro) inhibitors. All the molecules were screened by an enzymatic assay on M^pro and, then, cellular activity was evaluated using Vero cells viral infection model. The cellular screening disclosed compounds 29 and 34 as in-vitro SARS-CoV-2 replication inhibitors at non-toxic concentrations (0.32 < EC₅₀ < 5.98 μM). To rationalize these results, additional in-vitro assays were performed, focusing on papain like protease (PL^pro) and spike protein (SP) as potential targets for the synthesized molecules. This pharmacological workflow allowed the identification of compound 29, as a dual acting SARS-CoV-2 proteases inhibitor featuring micromolar inhibitory potency versus M^pro (IC₅₀ = 1.72 μM) and submicromolar potency versus PL^pro (IC₅₀ = 0.67 μM), and of compound 34 as a selective SP inhibitor (IC₅₀ = 3.26 μM).

Application of artificial intelligence in COVID-19 medical area: a systematic review

BACKGROUND

Coronavirus disease 2019 (COVID-19) has caused a large-scale global epidemic, impacting international politics and the economy. At present, there is no particularly effective medicine and treatment plan. Therefore, it is urgent and significant to find new technologies to diagnose early, isolate early, and treat early. Multimodal data drove artificial intelligence (AI) can potentially be the option. During the COVID-19 Pandemic, AI provided cutting-edge applications in disease, medicine, treatment, and target recognition. This paper reviewed the literature on the intersection of AI and medicine to analyze and compare different AI model applications in the COVID-19 Pandemic, evaluate their effectiveness, show their advantages and differences, and introduce the main models and their characteristics.

METHODS

We searched PubMed, arXiv, medRxiv, and Google Scholar through February 2020 to identify studies on AI applications in the medical areas for the COVID-19 Pandemic.

RESULTS

We summarize the main AI applications in six areas: (I) epidemiology, (II) diagnosis, (III) progression, (IV) treatment, (V) psychological health impact, and (VI) data security. The ongoing development in AI has significantly improved prediction, contact tracing, screening, diagnosis, treatment, medication, and vaccine development for the COVID-19 Pandemic and reducing human intervention in medical practice.

DISCUSSION

This paper provides strong advice for using AI-based auxiliary tools for related applications of human diseases. We also discuss the clinicians' role in the further development of AI. They and AI researchers can integrate AI technology with current clinical processes and information systems into applications. In the future, AI personnel and medical workers will further cooperate closely.

Designing potent inhibitors against the multidrug resistance P-glycoprotein

The multidrug transporter P-glycoprotein is an ATP binding cassette (ABC) exporter responsible for resistance to tumor cells during chemotherapy. This study was designed with computational approaches aimed at identifying the best potent inhibitors of P-glycoprotein. Although many compounds have been suggested to inhibit P-glycoprotein, however, their information on bioavailability, selectivity, ADMET properties, and molecular interactions has not been revealed. Molecular docking, ADMET analysis, molecular dynamics, Principal component analysis (PCA), and binding free energy calculations were performed. Two compounds D1 and D2 showed the best docking score against P-glycoprotein and both compounds have 4-thiazolidinone derivatives containing indolin-3 one moiety are novel anti-tumor compounds. ADMET calculation analysis predicted D1 and D2 to have acceptable pharmacokinetic properties. The MD simulation discloses that D1-P-glycoprotein and D2-P-glycoprotein complexes are in stable conformation as apo-form. Hydrophobic amino acid such as phenylalanine plays significant on the interactions of inhibitors. Principal component analysis shows that both complexes are relatively similar variables as apo-form except planarity and Columbo energy profile. In addition, Quantitative Structural Activity Relationship (QSAR) of the ligand candidates were subjected to the principal component analysis (PCA) for pattern recognition. Partial-least-square (PLS) regression analysis was further utilized to model drug candidates' QSAR for subsequent prediction of the binding energy of validated drug candidates. PCA revealed groupings of the drug candidates based on the similarity or differences in drug candidates QSAR. Moreover, the developed PLS regression accurately predicted the values of the binding energy of drug candidates, with low residual error of prediction.Communicated by Ramaswamy H. Sarma.

Drug targets, mechanisms of drug action, and therapeutics against SARS-CoV-2

The recent outbreak of COVID-19 has affected human lives severely. The human-to-human transmission of this viral disease has become deadly due to the unavailability of COVID-19 specific drugs. Here, an overview of various attempts made to design different therapeutic agents against various structural and non-structural proteins of SARS-CoV-2 has been summarized. Emphasis has been made to highlight the mechanisms of drug action and ways to design better inhibitors of these proteins. The roles of anti-oxidants and vitamins in suppressing COVID-19 are also discussed.

Antiviral phytochemicals as potent inhibitors against NS3 protease of dengue virus

Dengue, a mosquito-borne disease, has appeared as a major infectious disease globally. The virus requires its proteins to replicate and reproduce in the host cell. The NS3 protease converts the polyprotein to functional proteins with the help of the NS2B cofactor. Thus, NS3 protease is a promising target to develop antiviral inhibitors against the dengue virus. A systematic screening including ADMET properties, molecular docking, molecular dynamics (MD) simulation, binding free energy calculation, and QSAR studies is carried out to predict potent inhibitors against the NS3 protease. From the screening of 40 antiviral phytochemicals, ADMET properties analysis was used to screen out ligands that violate ADME rules and have probable toxicity. Cyanidin 3-Glucoside, Dithymoquinone, and Glabridin were predicted to be potent inhibitors against the NS3 protease according to their binding affinity. These ligands showed several noncovalent interactions, including hydrogen bond, hydrophobic interaction, electrostatic interaction, pi-sulfur interactions. The ligand-protein complexes were further scrutinized using 250 ns molecular dynamics simulation. The MM-PBSA binding free energy calculation was conducted to investigate their binding stability in dynamic conditions. The calculated pIC50(mM) value was predicted using the QSAR model with 89.91% goodness of fit. The predicted biologocal activity value for the ligands indicates they might have good potency.

Lead Discovery of SARS-CoV-2 Main Protease Inhibitors through Covalent Docking-Based Virtual Screening

During almost all 2020, coronavirus disease 2019 (COVID-19) pandemic has constituted the major risk for the worldwide health and economy, propelling unprecedented efforts to discover drugs for its prevention and cure. At the end of the year, these efforts have culminated with the approval of vaccines by the American Food and Drug Administration (FDA) and the European Medicines Agency (EMA) giving new hope for the future. On the other hand, clinical data underscore the urgent need for effective drugs to treat COVID-19 patients. In this work, we embarked on a virtual screening campaign against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Mpro chymotrypsin-like cysteine protease employing our in-house database of peptide and non-peptide ligands characterized by different types of warheads acting as Michael acceptors. To this end, we employed the AutoDock4 docking software customized to predict the formation of a covalent adduct with the target protein. In vitro verification of the inhibition properties of the most promising candidates allowed us to identify two new lead inhibitors that will deserve further optimization. From the computational point of view, this work demonstrates the predictive power of AutoDock4 and suggests its application for the in silico screening of large chemical libraries of potential covalent binders against the SARS-CoV-2 Mpro enzyme.

Docking-based virtual screening studies aiming at the covalent inhibition of SARS-CoV-2 MPro by targeting the cysteine 145

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the COVID-19 which has infected millions of people worldwide. The main protease of SARS-CoV-2 (M^Pro) has been recognized as a key target for the development of antiviral compounds. Taking advantage of the X-ray crystal complex with reversible covalent inhibitors interacting with the catalytic cysteine 145 (Cys145), we explored flexible docking studies to select alternative compounds able to target this residue as covalent inhibitors. First, docking studies of three known electrophilic compounds led to results consistent with co-crystallized data validating the method for SARS-CoV-2 M^Pro covalent inhibition. Then, libraries of soft electrophiles (overall 41 757 compounds) were submitted to docking-based virtual screening resulting in the identification of 17 molecules having their electrophilic group close to the Cys145 residue. We also investigated flexible docking studies of a focused approved covalent drugs library including 32 compounds with various electrophilic functional groups. Among them, the calculations resulted in the identification of four compounds, namely dimethylfumarate, fosfomycin, ibrutinib and saxagliptin, able first, to bind to the active site of the protein and second, to form a covalent bond with the catalytic cysteine.