Efficacy and safety of dihydroorotate dehydrogenase (DHODH) inhibitors "leflunomide" and "teriflunomide" in Covid-19: A narrative review

Crosstalk among proximal tubular cells, macrophages, and fibroblasts in acute kidney injury: single-cell profiling from the perspective of ferroptosis

The link between ferroptosis, a form of cell death mediated by iron and acute kidney injury (AKI) is recently gaining widespread attention. However, the mechanism of the crosstalk between cells in the pathogenesis and progression of acute kidney injury remains unexplored. In our research, we performed a non-negative matrix decomposition (NMF) algorithm on acute kidney injury single-cell RNA sequencing data based specifically focusing in ferroptosis-associated genes. Through a combination with pseudo-time analysis, cell-cell interaction analysis and SCENIC analysis, we discovered that proximal tubular cells, macrophages, and fibroblasts all showed associations with ferroptosis in different pathways and at various time. This involvement influenced cellular functions, enhancing cellular communication and activating multiple transcription factors. In addition, analyzing bulk expression profiles and marker genes of newly defined ferroptosis subtypes of cells, we have identified crucial cell subtypes, including Egr1 + PTC-C1, Jun + PTC-C3, Cxcl2 + Mac-C1 and Egr1 + Fib-C1. All these subtypes which were found in AKI mice kidneys and played significantly distinct roles from those of normal mice. Moreover, we verified the differential expression of Egr1, Jun, and Cxcl2 in the IRI mouse model and acute kidney injury human samples. Finally, our research presented a novel analysis of the crosstalk of proximal tubular cells, macrophages and fibroblasts in acute kidney injury targeting ferroptosis, therefore, contributing to better understanding the acute kidney injury pathogenesis, self-repairment and acute kidney injury-chronic kidney disease (AKI-CKD) progression.

Potent Dual Polymerase/Exonuclease Inhibitory Activities of Antioxidant Aminothiadiazoles Against the COVID-19 Omicron Virus: A Promising In Silico/In Vitro Repositioning Research Study

Recently, natural and synthetic nitrogenous heterocyclic antivirals topped the scene as first choices for the treatment of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and their accompanying disease, the coronavirus disease 2019 (COVID-19). Meanwhile, the mysterious evolution of a new strain of SARS-CoV-2, the Omicron variant and its sublineages, caused a new defiance in the continual COVID-19 battle. Hitting the two principal coronaviral-2 multiplication enzymes RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN) synchronously using the same ligand is a highly effective novel dual pathway to hinder SARS-CoV-2 reproduction and stop COVID-19 progression irrespective of the SARS-CoV-2 variant type since RdRps and ExoNs are widely conserved among all SARS-CoV-2 strains. Herein, the present computational/biological study screened our previous small libraries of nitrogenous heterocyclic compounds, searching for the most ideal drug candidates predictably able to efficiently act through this double approach. Theoretical filtration gave rise to three promising antioxidant nitrogenous heterocyclic compounds of the 1,3,4-thiadiazole type, which are CoViTris2022, Taroxaz-26, and ChloViD2022. Further experimental evaluation proved for the first time, utilizing the in vitro anti-RdRp/ExoN and anti-SARS-CoV-2 bioassays, that ChloViD2022, CoViTris2022, and Taroxaz-26 could effectively inhibit the replication of the new virulent strains of SARS-CoV-2 with extremely minute in vitro anti-RdRp and anti-SARS-CoV-2 EC50 values of 0.17 and 0.41 μM for ChloViD2022, 0.21 and 0.69 μM for CoViTris2022, and 0.23 and 0.73 μM for Taroxaz-26, respectively, transcending the anti-COVID-19 drug molnupiravir. The preliminary in silico outcomes greatly supported these biochemical results, proposing that the three molecules potently strike the key catalytic pockets of the SARS-CoV-2 (Omicron variant) RdRp's and ExoN's vital active sites. Moreover, the idealistic pharmacophoric hallmarks of CoViTris2022, Taroxaz-26, and ChloViD2022 molecules relatively make them typical dual-action inhibitors of SARS-CoV-2 replication and proofreading, with their highly flexible structures open for various kinds of chemical derivatization. To cut it short, the present pivotal findings of this comprehensive work disclosed the promising repositioning potentials of the three 2-aminothiadiazoles, CoViTris2022, Taroxaz-26, and ChloViD2022, to successfully interfere with the crucial biological interactions of the coronaviral-2 polymerase/exoribonuclease with the four principal RNA nucleotides, and, as a result, cure COVID-19 infection, encouraging us to rapidly start the three drugs' broad preclinical/clinical anti-COVID-19 evaluations.

Unveiling the Antiviral Capabilities of Targeting Human Dihydroorotate Dehydrogenase against SARS-CoV-2

The urgent need for effective treatments against emerging viral diseases, driven by drug-resistant strains and new viral variants, remains critical. We focus on inhibiting the human dihydroorotate dehydrogenase (HsDHODH), one of the main enzymes responsible for pyrimidine nucleotide synthesis. This strategy could impede viral replication without provoking resistance. We evaluated naphthoquinone fragments, discovering potent HsDHODH inhibition with IC50 ranging from 48 to 684 nM, and promising in vitro anti-SARS-CoV-2 activity with EC50 ranging from 1.2 to 2.3 μM. These compounds exhibited low toxicity, indicating potential for further development. Additionally, we employed computational tools such as molecular docking and quantitative structure-activity relationship (QSAR) models to analyze protein-ligand interactions, revealing that these naphthoquinones exhibit a protein binding pattern similar to brequinar, a potent HsDHODH inhibitor. These findings represent a significant step forward in the search for effective antiviral treatments and have great potential to impact the development of new broad-spectrum antiviral drugs.

Metabolic Enzymes in Viral Infection and Host Innate Immunity

Metabolic enzymes are central players for cell metabolism and cell proliferation. These enzymes perform distinct functions in various cellular processes, such as cell metabolism and immune defense. Because viral infections inevitably trigger host immune activation, viruses have evolved diverse strategies to blunt or exploit the host immune response to enable viral replication. Meanwhile, viruses hijack key cellular metabolic enzymes to reprogram metabolism, which generates the necessary biomolecules for viral replication. An emerging theme arising from the metabolic studies of viral infection is that metabolic enzymes are key players of immune response and, conversely, immune components regulate cellular metabolism, revealing unexpected communication between these two fundamental processes that are otherwise disjointed. This review aims to summarize our present comprehension of the involvement of metabolic enzymes in viral infections and host immunity and to provide insights for potential antiviral therapy targeting metabolic enzymes.

Cloning and Characterization of Yak DHODH Gene and Its Functional Studies in a Bisphenol S-Induced Ferroptosis Model of Fetal Fibroblasts

Dihydroorotate dehydrogenase (DHODH) is a rate-limiting enzyme of de novo biosynthesis of pyrimidine. Although the involvement of DHODH in resisting ferroptosis has been successively reported in recent years, which greatly advanced the understanding of the mechanism of programmed cell death (PCD), the genetic sequence of the yak DHODH gene and its roles in ferroptosis are still unknown. For this purpose, we firstly cloned the coding region sequence of DHODH (1188 bp) from yak liver and conducted a characterization analysis of its predictive protein that consists of 395 amino acids. We found that the coding region of the yak DHODH gene presented high conservation among species. Second, the expression profile of the DHODH gene in various yak tissues was investigated using RT-qPCR. The results demonstrated that DHODH was widely expressed in different yak tissues, with particularly high levels in the spleen, heart, and liver. Third, to investigate the involvement of DHODH in regulating ferroptosis in cells, yak skin fibroblasts (YSFs) were isolated from fetuses. And then, bisphenol S (BPS) was used to induce the in vitro ferroptosis model of YSFs. We observed that BPS decreased the cell viability (CCK8) and membrane potential (JC-1) of YSFs in a dose-dependent manner and induced oxidative stress by elevating reactive oxygen species (ROS). Simultaneously, it was evident that BPS effectively augmented the indicators associated with ferroptosis (MDA and BODIPY staining) and reduced GSH levels. Importantly, the co-administration of Ferrostatin-1 (Fer), a potent inhibitor of ferroptosis, significantly alleviated the aforementioned markers, thereby confirming the successful induction of ferroptosis in YSFs by BPS. Finally, overexpression plasmids and siRNAs of the yak DHODH gene were designed and transfected respectively into BPS-cultured YSFs to modulate DHODH expression. The findings revealed that DHODH overexpression alleviated the occurrence of BPS-induced ferroptosis, while interference of DHODH intensified the ferroptosis process in YSFs. In summary, we successfully cloned the coding region of the yak DHODH gene, demonstrating its remarkable conservation across species. Moreover, using BPS-induced ferroptosis in YSFs as the model, the study confirmed the role of the DHODH gene in resisting ferroptosis in yaks. These results offer valuable theoretical foundations for future investigations into the functionality of the yak DHODH gene and the underlying mechanisms of ferroptosis in this species.

Cell-specific genome-scale metabolic modeling of SARS-CoV-2-infected lung to identify antiviral enzymes

Computational systems biology plays a key role in the discovery of suitable antiviral targets. We designed a cell-specific, constraint-based modeling technique for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected lungs. We used the gene sequence of the alpha variant of SARS-CoV-2 to build a viral biomass reaction (VBR). We also used the mass proportion of lipids between the viral biomass and its host cell to estimate the stoichiometric coefficients of viral lipids in the reaction. We then integrated the VBR, the gene expression of the alpha variant of SARS-CoV-2, and the generic human metabolic network Recon3D to reconstruct a cell-specific genome-scale metabolic model. An antiviral target discovery (AVTD) platform was introduced using this model to identify therapeutic drug targets for combating COVID-19. The AVTD platform not only identified antiviral genes for eliminating viral replication but also predicted side effects of treatments. Our computational results revealed that knocking out dihydroorotate dehydrogenase (DHODH) might reduce the synthesis rate of cytidine-5'-triphosphate and uridine-5'-triphosphate, which terminate the viral building blocks of DNA and RNA for SARS-CoV-2 replication. Our results also indicated that DHODH is a promising antiviral target that causes minor side effects, which is consistent with the results of recent reports. Moreover, we discovered that the genes that participate in the de novo biosynthesis of glycerophospholipids and ceramides become unidentifiable if the VBR does not involve the stoichiometry of lipids.

Regulation of nucleotide metabolism in cancers and immune disorders

Nucleotides are the foundational elements of life. Proliferative cells acquire nutrients for energy production and the synthesis of macromolecules, including proteins, lipids, and nucleic acids. Nucleotides are continuously replenished through the activation of the nucleotide synthesis pathways. Despite the importance of nucleotides in cell physiology, there is still much to learn about how the purine and pyrimidine synthesis pathways are regulated in response to intracellular and exogenous signals. Over the past decade, evidence has emerged that several signaling pathways [Akt, mechanistic target of rapamycin complex I (mTORC1), RAS, TP53, and Hippo-Yes-associated protein (YAP) signaling] alter nucleotide synthesis activity and influence cell function. Here, we examine the mechanisms by which these signaling networks affect de novo nucleotide synthesis in mammalian cells. We also discuss how these molecular links can be targeted in diseases such as cancers and immune disorders.

Promising Experimental Anti-SARS-CoV-2 Agent "SLL-0197800": The Prospective Universal Inhibitory Properties against the Coming Versions of the Coronavirus

Isoquinoline derivatives having some nucleosidic structural features are considered as candidate choices for effective remediation of the different severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and their following disease, the coronavirus disease 2019 (COVID-19). SLL-0197800 is a recently discovered isoquinoline compound with potential strong universal anticoronaviral activities against SARS-CoV-2 and its previous strains. SLL-0197800 nonspecifically hits the main protease (Mpro) enzyme of the different coronaviruses. Herein in the present study, we tested the probability of the previous findings of this experimental agent to be extended to comprise any coronavirus through concurrently disrupting the mutable-less replication enzymes like the RNA-dependent RNA polymerase (RdRp) protein as well as the 3'-to-5' exoribonuclease (ExoN) protein. The in vitro anti-RdRp/ExoN assay revealed the potent inhibitory activities of SLL-0197800 on the coronaviral replication with minute values of anti-RdRp and anti-RdRp/ExoN EC50 (about 0.16 and 0.27 μM, respectively). The preliminary in silico outcomes significantly supported these biochemical findings. To put it simply, the present important results of these extension efforts greatly reinforce and extend the SLL-0197800's preceding findings, showing that the restraining/blocking actions (i.e., inhibitory activities) of this novel investigational anti-SARS-CoV-2 agent against the Mpro protein could be significantly extended against other copying and multiplication enzymes such as RdRp and ExoN, highlighting the potential use of SLL-0197800 against the coming versions of the homicidal coronavirus (if any), i.e., revealing the probable nonspecific anticoronaviral features and qualities of this golden experimental drug against nearly any coronaviral strain, for instance, SARS-CoV-3.

Advanced virtual screening enables the discovery of a host-targeting and broad-spectrum antiviral agent

We employed an advanced virtual screening (AVS) approach to identify potential inhibitors of human dihydroorotate dehydrogenase (DHODH), a validated target for development of broad-spectrum antivirals. We screened a library of 495118 compounds and identified 495 compounds that exhibited better binding scores than the reference ligands involved in the screening. From the top 100 compounds, we selected 28 based on their consensus docking scores and structural novelty. Then, we conducted in vitro experiments to investigate the antiviral activity of selected compounds on HSV-1 infection, which is susceptible to DHODH inhibitors. Among the tested compounds, seven displayed statistically significant antiviral effects, with Comp 19 being the most potent inhibitor. We found that Comp 19 exerted its antiviral effect in a dose-dependent manner (IC50 = 1.1 μM) and exhibited the most significant antiviral effect when added before viral infection. In the biochemical assay, Comp 19 inhibited human DHODH in a dose-dependent manner with the IC50 value of 7.3 μM. Long-timescale molecular dynamics simulations (1000 ns) revealed that Comp 19 formed a very stable complex with human DHODH. Comp 19 also displayed broad-spectrum antiviral activity and suppressed cytokine production in THP-1 cells. Overall, our study provides evidence that AVS could be successfully implemented to discover novel DHODH inhibitors with broad-spectrum antiviral activity.

Protein structure-based in-silico approaches to drug discovery: Guide to COVID-19 therapeutics

With more than 5 million fatalities and close to 300 million reported cases, COVID-19 is the first documented pandemic due to a coronavirus that continues to be a major health challenge. Despite being rapid, uncontrollable, and highly infectious in its spread, it also created incentives for technology development and redefined public health needs and research agendas to fast-track innovations to be translated. Breakthroughs in computational biology peaked during the pandemic with renewed attention to making all cutting-edge technology deliver agents to combat the disease. The demand to develop effective treatments yielded surprising collaborations from previously segregated fields of science and technology. The long-standing pharmaceutical industry's aversion to repurposing existing drugs due to a lack of exponential financial gain was overrun by the health crisis and pressures created by front-line researchers and providers. Effective vaccine development even at an unprecedented pace took more than a year to develop and commence trials. Now the emergence of variants and waning protections during the booster shots is resulting in breakthrough infections that continue to strain health care systems. As of now, every protein of SARS-CoV-2 has been structurally characterized and related host pathways have been extensively mapped out. The research community has addressed the druggability of a multitude of possible targets. This has been made possible due to existing technology for virtual computer-assisted drug development as well as new tools and technologies such as artificial intelligence to deliver new leads. Here in this article, we are discussing advances in the drug discovery field related to target-based drug discovery and exploring the implications of known target-specific agents on COVID-19 therapeutic management. The current scenario calls for more personalized medicine efforts and stratifying patient populations early on for their need for different combinations of prognosis-specific therapeutics. We intend to highlight target hotspots and their potential agents, with the ultimate goal of using rational design of new therapeutics to not only end this pandemic but also uncover a generalizable platform for use in future pandemics.

Dual computational and biological assessment of some promising nucleoside analogs against the COVID-19-Omicron variant

Nucleoside analogs/derivatives (NAs/NDs) with potent antiviral activities are now deemed very convenient choices for the treatment of coronavirus disease 2019 (COVID-19) arisen by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. At the same time, the appearance of a new strain of SARS-CoV-2, the Omicron variant, necessitates multiplied efforts in fighting COVID-19. Counteracting the crucial SARS-CoV-2 enzymes RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN) jointly altogether using the same inhibitor is a quite successful new plan to demultiplicate SARS-CoV-2 particles and eliminate COVID-19 whatever the SARS-CoV-2 subtype is (due to the significant conservation nature of RdRps and ExoNs in the different SARS-CoV-2 strains). Successive in silico screening of known NAs finally disclosed six different promising NAs, which are riboprine/forodesine/tecadenoson/nelarabine/vidarabine/maribavir, respectively, that predictably can act through the planned dual-action mode. Further in vitro evaluations affirmed the anti-SARS-CoV-2/anti-COVID-19 potentials of these NAs, with riboprine and forodesine being at the top. The two NAs are able to effectively antagonize the replication of the new virulent SARS-CoV-2 strains with considerably minute in vitro anti-RdRp and anti-SARS-CoV-2 EC₅₀ values of 189 and 408 nM for riboprine and 207 and 657 nM for forodesine, respectively, surpassing both remdesivir and the new anti-COVID-19 drug molnupiravir. Furthermore, the favorable structural characteristics of the two molecules qualify them for varied types of isosteric and analogistic chemical derivatization. In one word, the present important outcomes of this comprehensive dual study revealed the anticipating repurposing potentials of some known nucleosides, led by the two NAs riboprine and forodesine, to successfully discontinue the coronaviral-2 polymerase/exoribonuclease interactions with RNA nucleotides in the SARS-CoV-2 Omicron variant (BA.5 sublineage) and accordingly alleviate COVID-19 infections, motivating us to initiate the two drugs' diverse anti-COVID-19 pharmacological evaluations to add both of them betimes in the COVID-19 therapeutic protocols.

Optimization of CRISPR-Cas system for clinical cancer therapy

Cancer is a genetic disease caused by alterations in genome and epigenome and is one of the leading causes for death worldwide. The exploration of disease development and therapeutic strategies at the genetic level have become the key to the treatment of cancer and other genetic diseases. The functional analysis of genes and mutations has been slow and laborious. Therefore, there is an urgent need for alternative approaches to improve the current status of cancer research. Gene editing technologies provide technical support for efficient gene disruption and modification in vivo and in vitro, in particular the use of clustered regularly interspaced short palindromic repeats (CRISPR)-Cas systems. Currently, the applications of CRISPR-Cas systems in cancer rely on different Cas effector proteins and the design of guide RNAs. Furthermore, effective vector delivery must be met for the CRISPR-Cas systems to enter human clinical trials. In this review article, we describe the mechanism of the CRISPR-Cas systems and highlight the applications of class II Cas effector proteins. We also propose a synthetic biology approach to modify the CRISPR-Cas systems, and summarize various delivery approaches facilitating the clinical application of the CRISPR-Cas systems. By modifying the CRISPR-Cas system and optimizing its in vivo delivery, promising and effective treatments for cancers using the CRISPR-Cas system are emerging.

A first in man study to evaluate the safety, pharmacokinetics and pharmacodynamics of RP7214, a dihydroorotate dehydrogenase inhibitor in healthy subjects

Dihydroorotate dehydrogenase (DHODH) is a mitochondrial enzyme that is essential for pyrimidine de novo synthesis. Rapidly growing cancer cells and replicating viruses are dependent on host cell nucleotides, the precursors of which are provided by DHODH. Hence, DHODH becomes an ideal target for pharmacological intervention. RP7214 is a potent and selective inhibitor of human DHODH and has shown antiviral and antileukaemic activity in preclinical studies. This paper describes the phase I study that evaluated the safety and pharmacokinetics of single and multiple ascending doses (SAD and MAD) and the food effect of RP7214 in healthy volunteers (HVs). The study was a randomized, double-blind, placebo-controlled trial of single dose (100, 200 and 400 mg QD), multiple doses (200 and 400 mg BID for 7 days) and a food effect study at a single dose of 200 mg. A total of 18, 12 and 12 HVs were enrolled in the SAD, MAD and food effect parts of the study, respectively. RP7214 was well tolerated at all dose levels. There were 20 treatment-emergent adverse events (TEAEs) reported, out of which most were mild to moderate in severity while three TEAEs were grade ≥3. RP7214 showed accumulation on multiple dosing. Steady-state concentrations were reached within about 3-6 days. The mean plasma half-life at steady-state was 12.8 hours (9.9-15.3). Food did not impact the absorption of RP7214. Inhibition of DHODH, as evidenced by increased dihydroorotate levels, was observed, confirming target engagement. The high systemic exposure with a favourable safety profile shows potential for the development of RP7214 in SARS-CoV-2 and acute myeloid leukaemia (NCT04680429).

Novel Investigational Anti-SARS-CoV-2 Agent Ensitrelvir "S-217622": A Very Promising Potential Universal Broad-Spectrum Antiviral at the Therapeutic Frontline of Coronavirus Species

Lately, nitrogenous heterocyclic antivirals, such as nucleoside-like compounds, oxadiazoles, thiadiazoles, triazoles, quinolines, and isoquinolines, topped the therapeutic scene as promising agents of choice for the treatment of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and their accompanying ailment, the coronavirus disease 2019 (COVID-19). At the same time, the continuous emergence of new strains of SARS-CoV-2, like the Omicron variant and its multiple sublineages, resulted in a new defiance in the enduring COVID-19 battle. Ensitrelvir (S-217622) is a newly discovered orally active noncovalent nonpeptidic agent with potential strong broad-spectrum anticoronaviral activities, exhibiting promising nanomolar potencies against the different SARS-CoV-2 variants. S-217622 effectively and nonspecifically hits the main protease (M^pro) enzyme of a broad scope of coronaviruses. Herein, in the present computational/biological study, we tried to extend these previous findings to prove the universal activities of this investigational agent against any coronavirus, irrespective of its type, through synchronously acting on most of its main unchanged replication enzymes/proteins, including (in addition to the M^pro), e.g., the highly conserved RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN). Biochemical evaluation proved, using the in vitro anti-RdRp/ExoN bioassay, that S-217622 can potently inhibit the replication of coronaviruses, including the new virulent strains of SARS-CoV-2, with extremely minute in vitro anti-RdRp and anti-RdRp/ExoN half-maximal effective concentration (EC₅₀) values of 0.17 and 0.27 μM, respectively, transcending the anti-COVID-19 drug molnupiravir. The preliminary in silico results greatly supported these biochemical results, proposing that the S-217622 molecule strongly and stabilizingly strikes the key catalytic pockets of the SARS-CoV-2 RdRp's and ExoN's principal active sites predictably via the nucleoside analogism mode of anti-RNA action (since the S-217622 molecule can be considered as a uridine analog). Moreover, the idealistic druglikeness and pharmacokinetic characteristics of S-217622 make it ready for pharmaceutical formulation with the expected very good clinical behavior as a drug for the infections caused by coronaviruses, e.g., COVID-19. To cut it short, the current critical findings of this extension work significantly potentiate and extend the S-217622's previous in vitro/in vivo (preclinical) results since they showed that the striking inhibitory activities of this novel anti-SARS-CoV-2 agent on the M^pro could be extended to other replication enzymes like RdRp and ExoN, unveiling the possible universal use of the compound against the next versions of the virus (i.e., disclosing the nonspecific anticoronaviral properties of this compound against almost any coronavirus strain), e.g., SARS-CoV-3, and encouraging us to rapidly start the compound's vast clinical anti-COVID-19 evaluations.

Strong Dual Antipolymerase/Antiexonuclease Actions of Some Aminothiadiazole Antioxidants: A Promising In-Silico/In-Vitro Repurposing Research Study against the COVID-19 Omicron Virus (B.1.1.529.3 Lineage)

Currently, nitrogen-containing heterocyclic virucides take the lead as top options for treating the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections and their escorting disease, the coronavirus disease 2019 (COVID-19). But unfortunately, the sudden emergence of a new strain of SARS-CoV-2, the Omicron variant and its lineages, complicated matters in the incessant COVID-19 battle. Goaling the two paramount coronaviral-2 multiplication enzymes RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN) at synchronous times using single ligand is a quite effective new binary avenue to restrain SARS-CoV-2 reproduction and cease COVID-19 progression irrespective of the SARS-CoV-2 strain type, as RdRps and ExoNs are vastly conserved in all SARS-CoV-2 strains. The presented in-silico/in-vitro research winnowed our own small libraries of antioxidant nitrogenous heterocyclic compounds, inspecting for the utmost convenient drug candidates expectedly capable of effectively working through this dual tactic. Computational screening afforded three promising compounds of the antioxidant 1,3,4-thiadiazole class, which were named ChloViD2022, Taroxaz-26, and CoViTris2022. Subsequent biological examination, employing the in-vitro anti-RdRp/anti-ExoN and anti-SARS-CoV-2 assays, exclusively demonstrated that ChloViD2022, CoViTris2022, and Taroxaz-26 could efficiently block the replication of the new lineages of SARS-CoV-2 with considerably minute anti-RdRp and anti-SARS-CoV-2 EC50 values of about 0.18 and 0.44 μM for ChloViD2022, 0.22 and 0.72 μM for CoViTris2022, and 0.25 and 0.78 μM for Taroxaz-26, in the order, overtaking the standard anti-SARS-CoV-2 drug molnupiravir. These biochemical findings were optimally presupported by the results of the prior in-silico screening, suggesting that the three compounds might potently hit the catalytic active sites of the virus's RdRp and ExoN enzymes. Furthermore, the perfect pharmacophoric features of ChloViD2022, Taroxaz-26, and CoViTris2022 molecules make them typical dual inhibitors of SARS-CoV-2 replication and proofreading, with their relatively flexible structures eligible for diverse forms of chemical modification. In sum, the current important results of this thorough research work exposed the interesting repurposing potential of the three 2-amino-1,3,4-thiadiazole ligands, ChloViD2022, Taroxaz-26, and CoViTris2022, to effectively conflict with the vital biointeractions between the coronavirus's polymerase/exoribonuclease and the four essential RNA nucleotides, and, accordingly, arrest COVID-19 disease, persuading the relevant investigators to quickly begin the three agents' comprehensive preclinical and clinical anti-COVID-19 assessments.

Evaluation of a series of nucleoside analogs as effective anticoronaviral-2 drugs against the Omicron-B.1.1.529/BA.2 subvariant: A repurposing research study

Mysterious evolution of a new strain of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the Omicron variant, led to a new challenge in the persistent coronavirus disease 2019 (COVID-19) battle. Objecting the conserved SARS-CoV-2 enzymes RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN) together using one ligand is a successful new tactic to stop SARS-CoV-2 multiplication and COVID-19 progression. The current comprehensive study investigated most nucleoside analogs (NAs) libraries, searching for the most ideal drug candidates expectedly able to act through this double tactic. Gradual computational filtration afforded six different promising NAs, riboprine/forodesine/tecadenoson/nelarabine/vidarabine/maribavir. Further biological assessment proved that riboprine and forodesine are able to powerfully inhibit the replication of the new virulent strains of SARS-CoV-2 with extremely minute in vitro anti-RdRp and anti-SARS-CoV-2 EC₅₀ values of about 0.21 and 0.45 μM for riboprine and about 0.23 and 0.70 μM for forodesine, respectively, surpassing both remdesivir and the new anti-COVID-19 drug molnupiravir. These biochemical findings were supported by the prior in silico data. Additionally, the ideal pharmacophoric features of riboprine and forodesine molecules render them typical dual-action inhibitors of SARS-CoV-2 replication and proofreading. These findings suggest that riboprine and forodesine could serve as prospective lead compounds against COVID-19. Graphical abstract.

ML390 inhibits enterovirus 71 replication by targeting de novo pyrimidine biosynthesis pathway

Enterovirus 71 (EV71), a small, single-stranded, positive-sense RNA virus belonging to the enterovirus genus in the family Picornaviridae, causes hand, foot, and mouth disease. Although EV71 seriously threatens to public health, no effective antiviral drugs are available for treating this disease. In this study, we found that ML390, a dihydroorotate dehydrogenase inhibitor, has potential anti-EV71 activity. ML390 dose-dependently inhibited EV71 replication with IC₅₀ and selectivity index values of 0.06601 μM and 156.5, respectively. Supplementation with the downstream product orotate significantly suppressed the ability of ML390 to inhibit EV71 replication. Moreover, an adequate supply of exogenous uridine and cytosine suppressed the anti-EV71 activity of ML390. Thus, the antiviral activity of ML390 is mediated by the inhibition of the pyrimidine synthesis pathway. In an EV71-infected mouse model, ML390 reduced the load of EV71 in the brain, liver, heart, spleen, front legs, and hind legs, and significantly increased the survival rate of the mice infected by EV71. ML390 shows potential for the treatment of hand, foot, and mouth disease caused by EV71 infection.

Forodesine and Riboprine Exhibit Strong Anti-SARS-CoV-2 Repurposing Potential: In Silico and In Vitro Studies

Lately, nucleos(t)ide antivirals topped the scene as top options for the treatment of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Targeting the two broadly conserved SARS-CoV-2 enzymes, RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN), together using only one shot is a very successful new tactic to stop SARS-CoV-2 multiplication irrespective of the SARS-CoV-2 variant type. Herein, the current studies investigated most nucleoside analogue (NA) libraries, searching for the ideal drug candidates expectedly able to act through this double tactic. Gradual computational filtration gave rise to six different promising NAs along with their corresponding triphosphate (TP) nucleotides. The subsequent biological assessment proved for the first time that, among the six NAs, riboprine and forodesine are able to hyperpotently inhibit the replication of the Omicron strain of SARS-CoV-2 with extremely low in vitro anti-RdRp, anti-ExoN, and anti-SARS-CoV-2 EC50 values of about 0.18, 0.28, and 0.40 μM for riboprine and about 0.20, 0.31, and 0.65 μM for forodesine, respectively, surpassing remdesivir and molnupiravir. The significant probability that both compounds may also act as prodrugs for their final TP nucleotides in vivo pushed us to examine the same activities for forodesine-TP and riboprine-TP. Both nucleotides similarly displayed very promising results, respectively, which are much better than those for the two reference TP nucleotides, GS-443902 and β-d-N4-hydroxycytidine 5'-TP (NHC-TP). The prior in silico data supported these biochemical findings, suggesting that riboprine and forodesine molecules and their expected active TP metabolites strongly hit the key catalytic pockets of the SARS-CoV-2 RdRp's and ExoN's main active sites. In brief, the current important results of this comprehensive study revealed the interesting repurposing potentials of, mainly, the two bioactive nucleosides forodesine and riboprine and their TP nucleotides to effectively shut down the polymerase/exoribonuclease-RNA nucleotide interactions of SARS-CoV-2 and consequently treat COVID-19 infections.

A Series of Adenosine Analogs as the First Efficacious Anti-SARS-CoV-2 Drugs against the B.1.1.529.4 Lineage: A Preclinical Repurposing Research Study

Given the rapid progression of the coronavirus disease 2019 (COVID-19) pandemic, an ultrafast response was urgently required to handle this major public crisis. To contain the pandemic, investments are required to develop diagnostic tests, prophylactic vaccines, and novel therapies. Lately, nucleoside analog (NA) antivirals topped the scene as top options for the treatment of COVID-19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections. Meanwhile, the continuous generation of new lineages of the SARS-CoV-2 Omicron variant caused a new challenge in the persistent COVID-19 battle. Hitting the two crucial SARS-CoV-2 enzymes RNA-dependent RNA polymerase (RdRp) and 3'-to-5' exoribonuclease (ExoN) collectively together using only one single ligand is a very successful new approach to stop SARS-CoV-2 multiplication and combat COVID-19 irrespective of the SARS-CoV-2 variant type because RdRps and ExoNs are broadly conserved among all SARS-CoV-2 strains. Herein, the current comprehensive study investigated most NAs libraries, searching for the most ideal drug candidates expectedly able to perfectly act through this double tactic. Gradual computational filtration gave rise to six different promising NAs, which are riboprine, forodesine, tecadenoson, nelarabine, vidarabine, and maribavir, respectively. Further biological assessment proved for the first time, using the in vitro anti-RdRp/ExoN and anti-SARS-CoV-2 bioassays, that riboprine and forodesine, among all the six tested NAs, are able to powerfully inhibit the replication of the new virulent strains of SARS-CoV-2 with extremely minute in vitro anti-RdRp and anti-SARS-CoV-2 EC₅₀ values of about 0.22 and 0.49 μM for riboprine and about 0.25 and 0.73 μM for forodesine, respectively, surpassing both remdesivir and the new anti-COVID-19 drug molnupiravir. The prior in silico data supported these biochemical findings, suggesting that riboprine and forodesine molecules strongly hit the key catalytic pockets of the SARS-CoV-2 (Omicron variant) RdRp's and ExoN's main active sites. Additionally, the ideal pharmacophoric features of riboprine and forodesine molecules render them typical dual-action inhibitors of SARS-CoV-2 replication and proofreading, with their relatively flexible structures open for diverse types of chemical derivatization. In Brief, the current important results of this comprehensive study revealed the interesting repurposing potentials of, mainly, the two nucleosides riboprine and forodesine to effectively shut down the polymerase/exoribonuclease-RNA nucleotides interactions of the SARS-CoV-2 Omicron variant and consequently treat COVID-19 infections, motivating us to rapidly begin the two drugs' broad preclinical/clinical anti-COVID-19 bioevaluations, hoping to combine both drugs soon in the COVID-19 treatment protocols.

Targeting Acute Myelogenous Leukemia Using Potent Human Dihydroorotate Dehydrogenase Inhibitors Based on the 2-Hydroxypyrazolo[1,5-a]pyridine Scaffold: SAR of the Aryloxyaryl Moiety

In recent years, human dihydroorotate dehydrogenase inhibitors have been associated with acute myelogenous leukemia as well as studied as potent host targeting antivirals. Starting from MEDS433 (IC50 1.2 nM), we kept improving the structure-activity relationship of this class of compounds characterized by 2-hydroxypyrazolo[1,5-a]pyridine scaffold. Using an in silico/crystallography supported design, we identified compound 4 (IC50 7.2 nM), characterized by the presence of a decorated aryloxyaryl moiety that replaced the biphenyl scaffold, with potent inhibition and pro-differentiating abilities on AML THP1 cells (EC50 74 nM), superior to those of brequinar (EC50 249 nM) and boosted when in combination with dipyridamole. Finally, compound 4 has an extremely low cytotoxicity on non-AML cells as well as MEDS433; it has shown a significant antileukemic activity in vivo in a xenograft mouse model of AML.

COVID-19 among patients with giant cell arteritis: a single-centre observational study from Slovenia

OBJECTIVES

Patients with giant cell arteritis (GCA) represent a fragile population with an increased infection risk. In a recent study, older age, a higher number of comorbidities, higher disease activity and prednisolone ≥ 10 mg/day were associated with worse COVID-19 outcome. We aimed to evaluate the frequency and severity of COVID-19 in a well-defined GCA cohort.

METHODS

We reviewed medical records of histologically and/or by imaging-proven GCA patients diagnosed between September 2011 and February 2020 at our secondary/tertiary centre and followed during the COVID-19 pandemic between March 2020 and February 2022 (24 months). Descriptive statistics were used to explore the studied population.

RESULTS

Of 314 patients with GCA diagnosed for the first time during a 102-month period, 49 patients died before March 2020. Of the remaining 265 patients, 55 (20.8%) patients suffered from a total of 57 SARS-CoV-2 infections. We observed 44 (77.2%) mild and 13 (22.8%) severe COVID-19 episodes (the latter defined as needing hospitalization, death or thrombotic complication). Patients with severe COVID-19 were more likely to have arterial hypertension (12 [92.3%] vs. 25 [56.8%]; p = 0.022), cardiovascular disease (7 [53.8%] vs. 10 [22.7%]; p = 0.043) or obesity (5 [38.5%] vs. 5 [11.4%]; p = 0.038). Neither prednisolone dose 1-5 mg/day (p = 0.483) nor leflunomide use (p = 1.000) was associated with COVID-19 course. There were no significant differences in sex, age, GCA type, GCA disease duration and other comorbidities in patients with mild and severe COVID-19 in our cohort.

CONCLUSION

More than a fifth of our GCA patients had severe COVID-19. Treatment with leflunomide or low doses of glucocorticoids were not associated with severe course in our cohort. Key Points • Treatment with leflunomide or low doses of glucocorticoids were not associated with worse COVID-19 outcome. • Outcomes of COVID-19 improved as the COVID-19 pandemic, prevention and treatment options evolved. • Arterial hypertension, cardiovascular disease or obesity were associated with severe COVID-19.

Efficacious Preclinical Repurposing of the Nucleoside Analogue Didanosine against COVID-19 Polymerase and Exonuclease

Analogues and derivatives of natural nucleosides/nucleotides are considered among the most successful bioactive species of drug-like compounds in modern medicinal chemistry, as they are well recognized for their diverse and efficient pharmacological activities in humans, especially as antivirals and antitumors. Coronavirus disease 2019 (COVID-19) is still almost incurable, with its infectious viral microbe, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continuing to wreak devastation around the world. This global crisis pushed all involved scientists, including drug discoverers and clinical researchers, to try to find an effective and broad-spectrum anti-COVID-19 drug. Didanosine (2′,3′-dideoxyinosine, DDI) is a synthetic inosine/adenosine/guanosine analogue and highly active antiretroviral therapeutic agent used for the treatment of human immunodeficiency virus infection and acquired immunodeficiency syndrome (HIV/AIDS). This potent reverse-transcriptase inhibitor is characterized by proven strong pharmacological effects against the viral genome, which may successfully take part in the effective treatment of SARS-CoV-2/COVID-19. Additionally, targeting the pivotal SARS-CoV-2 replication enzyme, RNA-dependent RNA polymerase (RdRp), is a very successful tactic to combat COVID-19 irrespective of the SARS-CoV-2 variant type because RdRps are broadly conserved among all SARS-CoV-2 strains. Herein, the current study proved for the first time, using the in vitro antiviral evaluation, that DDI is capable of potently inhibiting the replication of the novel virulent progenies of SARS-CoV-2 with quite tiny in vitro anti-SARS-CoV-2 and anti-RdRp EC₅₀ values of around 3.1 and 0.19 μM, respectively, surpassing remdesivir together with its active metabolite (GS-441524). Thereafter, the in silico computational interpretation of the biological results supported that DDI strongly targets the key pocket of the SARS-CoV-2 RdRp main catalytic active site. The ideal pharmacophoric characteristics of the ligand DDI make it a typical inhibiting agent of SARS-CoV-2 multiplication processes (including high-fidelity proofreading), with its elastic structure open for many kinds of derivatization. In brief, the present results further uphold and propose the repurposing potentials of DDI against the different types of COVID-19 and convincingly motivate us to quickly launch its extensive preclinical/clinical pharmacological evaluations, hoping to combine it in the COVID-19 therapeutic protocols soon.

Development of accelerated high-throughput antiviral screening systems for emerging orthomyxoviruses

Bourbon virus (BRBV) is an emerging tick-borne orthomyxovirus that causes severe febrile illness in humans. There are no specific treatments for BRBV disease currently available. Here, we developed a highly accessible and robust, quantitative fluorescence-based BRBV minigenome (MG) system and applied it to high-throughput antiviral drug screening. We demonstrated that human dihydroorotate dehydrogenase (DHODH) inhibitors, hDHODH-IN-4 and brequinar, efficiently reduced BRBV RNA synthesis, and validated these findings using infectious BRBV in vitro. The DHODH inhibitors also exhibited high potency in inhibiting MG activities of other orthomyxoviruses with emerging zoonotic potential, including bat influenza A virus, swine influenza D virus, and Thogoto virus. Our newly developed MG system is a powerful platform for antiviral drug screening across the Orthomyxoviridae family, enabling rapid development and deployment of antivirals against future emerging orthomyxoviruses.

Potent Inhibitory Activities of the Adenosine Analogue Cordycepin on SARS-CoV-2 Replication

Nucleoside analogues are among the most successful bioactive classes of druglike compounds in pharmaceutical chemistry as they are well-known for their numerous effective bioactivities in humans, especially as antiviral and anticancer agents. Coronavirus disease 2019 (COVID-19) is still untreatable, with its causing virus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), continuing to wreak havoc on the ground everywhere. This complicated international situation urged all concerned scientists, including medicinal chemists and drug discoverers, to search for a potent anti-COVID-19 drug. Cordycepin (3′-deoxyadenosine) is a known natural adenosine analogue of fungal origin, which could also be synthetically produced. This bioactive phytochemical compound is characterized by several proven strong pharmacological actions that may effectively contribute to the comprehensive treatment of COVID-19, with the antiviral activities being the leading ones. Some new studies predicted the possible inhibitory affinities of cordycepin against the principal SARS-CoV-2 protein targets (e.g., SARS-CoV-2 spike (S) protein, main protease (M^pro) enzyme, and RNA-dependent RNA polymerase (RdRp) enzyme) based on the computational approach. Interestingly, the current research showed, for the first time, that cordycepin is able to potently inhibit the multiplication of the new resistant strains of SARS-CoV-2 with a very minute in vitro anti-SARS-CoV-2 EC₅₀ of about 2 μM, edging over both remdesivir and its active metabolite GS-441524. The ideal pharmacophoric features of the cordycepin molecule render it a typical inhibitor of SARS-CoV-2 replication, with its flexible structure open for most types of derivatization in the future. Briefly, the current findings further support and suggest the repurposing possibility of cordycepin against COVID-19 and greatly encourage us to confidently and rapidly begin its preclinical/clinical evaluations for the comprehensive treatment of COVID-19.