Repositioning salicylanilide anthelmintic drugs to treat adenovirus infections

Dietary oxyclozanide influences antioxidant enzyme activities and damages DNA in Galleria mellonella (Lepidoptera: Pyralidae)

Oxyclozanide (OXY) is an anthelmintic widely used in the treatment of flatworm infection and fasciolosis. It also has antiadenovirus, antibiofilm, antifungal, and antibacterial activities. Various chemicals have been suggested as alternative chemicals in insect pest management. Here, the oxidative and genotoxic effects of OXY on 7th instars, pupae and adults of the model organism Galleria mellonella (Linnaeus) (Lepidoptera: Pyralidae) were examined. First-instar larvae were reared on 0.003, 0.03, 0.3, and 1.5 g OXY per 100 g artificial diets. Compared with all tested OXY concentrations and controls without OXY, dietary OXY led to increased antioxidant capacity and genotoxic effects. Concentrations of malondialdehyde, an oxidative stress marker, were significantly increased in adults of larvae reared on OXY-charged diets at 0.3 and 1.5 g/100 g compared to the adult control group. We also recorded a significant increase in the genotoxic test data (Tail length, Tail DNA %, Tail moment) at the same stages and concentrations. We recorded significant increases in glutathione-S-transferase, superoxide dismutase (SOD) and glutathione peroxidase activities in larvae fed high OXY concentrations. SOD and catalase activities were also significantly increased at the concentration of 0.03 g/100 g of OXY in the pupal and adult stages. Cytochrome P450 monooxygenase activity was significantly increased at the highest concentration of OXY in the larval and pupal stages. Also, our regression analysis indicates a correlation between the markers of oxidative stress, antioxidant enzymes and comet parameters. These data indicate that OXY induces oxidative stress and antioxidative enzyme response.

Molecular insights and promise of oncolytic virus based immunotherapy

Discovering a therapeutic that can counteract the aggressiveness of this disease's mechanism is crucial for improving survival rates for cancer patients and for better understanding the most different types of cancer. In recent years, using these viruses as an anticancer therapy has been thought to be successful. They mostly work by directly destroying cancer cells, activating the immune system to fight cancer, and expressing exogenous effector genes. For the treatment of tumors, oncolytic viruses (OVs), which can be modified to reproduce only in tumor tissues and lyse them while preserving the healthy non-neoplastic host cells and reinstating antitumor immunity which present a novel immunotherapeutic strategy. OVs can exist naturally or be created in a lab by altering existing viruses. These changes heralded the beginning of a new era of less harmful virus-based cancer therapy. We discuss three different types of oncolytic viruses that have already received regulatory approval to treat cancer as well as clinical research using oncolytic adenoviruses. The primary therapeutic applications, mechanism of action of oncolytic virus updates, future views of this therapy will be covered in this chapter.

Inhibition of adenovirus transport from the endosome to the cell nucleus by rotenone

Regardless of the clinical impact of human adenovirus (HAdV) infections in the healthy population and its high morbidity in immunosuppressed patients, a specific treatment is still not yet available. In this study, we screened the CM1407 COST Action's chemical library, comprising 1,233 natural products to identify compounds that restrict HAdV infection. Among them, we identified rotenolone, a compound that significantly inhibited HAdV infection. Next, we selected four isoflavonoid-type compounds (e.g., rotenone, deguelin, millettone, and tephrosin), namely rotenoids, structurally related to rotenolone in order to evaluate and characterized in vitro their antiviral activities against HAdV and human cytomegalovirus (HCMV). Their IC50 values for HAdV ranged from 0.0039 µM for rotenone to 0.07 µM for tephrosin, with selective indices ranging from 164.1 for rotenone to 2,429.3 for deguelin. In addition, the inhibition of HCMV replication ranged from 50% to 92.1% at twice the IC50 concentrations obtained in the plaque assay for each compound against HAdV. Our results indicated that the mechanisms of action of rotenolone, deguelin, and tephrosin involve the late stages of the HAdV replication cycle. However, the antiviral mechanism of action of rotenone appears to involve the alteration of the microtubular polymerization, which prevents HAdV particles from reaching the nuclear membrane of the cell. These isoflavonoid-type compounds exert high antiviral activity against HAdV at nanomolar concentrations, and can be considered strong hit candidates for the development of a new class of broad-spectrum antiviral drugs.

Therapeutic potential of salicylamide derivatives for combating viral infections

Since time immemorial human beings have constantly been fighting against viral infections. The ongoing and devastating coronavirus disease 2019 pandemic represents one of the most severe and most significant public health emergencies in human history, highlighting an urgent need to develop broad-spectrum antiviral agents. Salicylamide (2-hydroxybenzamide) derivatives, represented by niclosamide and nitazoxanide, inhibit the replication of a broad range of RNA and DNA viruses such as flavivirus, influenza A virus, and coronavirus. Moreover, nitazoxanide was effective in clinical trials against different viral infections including diarrhea caused by rotavirus and norovirus, uncomplicated influenza A and B, hepatitis B, and hepatitis C. In this review, we summarize the broad antiviral activities of salicylamide derivatives, the clinical progress, and the potential targets or mechanisms against different viral infections and highlight their therapeutic potential in combating the circulating and emerging viral infections in the future.

Discovery of rafoxanide as a novel agent for the treatment of non-small cell lung cancer

Non-small cell lung cancer (NSCLC), which accounts for approximately 85% of all lung cancer cases, is associated with a poor outcome. Rafoxanide is an anthelmintic drug that inhibits tumor growth in certain malignancies. However, its impact on NSCLC remains unknown. In this study, we examined the effect of rafoxanide on NSCLC and dissected the underlying mechanism. The results showed that rafoxanide significantly inhibited the growth, invasion, and migration of NSCLC cells. Besides, rafoxanide can induce NSCLC cell apoptosis and cell cycle arrest in a dose-dependent manner. RNA-seq analysis revealed that genes associated with endoplasmic reticulum stress (ER) stress responses were activated. Mechanistically, we found Rafoxanide can induce ER stress and activate the unfolded protein response (UPR). Apoptosis was activated by excessive ER stress, and autophagy was activated to partially alleviate ER stress. In vivo, we found that rafoxanide inhibited the growth of A549 and H1299 xenograft mouse models without severe side effects. Collectively, the present study indicates that rafoxanide may be a candidate drug for the treatment of NSCLC.

Study of Biological Activities and ADMET-Related Properties of Salicylanilide-Based Peptidomimetics

A series of eleven benzylated intermediates and eleven target compounds derived from salicylanilide were tested against Staphylococcus aureus ATCC 29213 and Enterococcus faecalis ATCC 29212 as reference strains and against three clinical isolates of methicillin-resistant S. aureus (MRSA) and three isolates of vancomycin-resistant E. faecalis. In addition, the compounds were evaluated against Mycobacterium tuberculosis H37Ra and M. smegmatis ATCC 700084. The in vitro cytotoxicity of the compounds was assessed using the human monocytic leukemia cell line THP-1. The lipophilicity of the prepared compounds was experimentally determined and correlated with biological activity. The benzylated intermediates were found to be completely biologically inactive. Of the final eleven compounds, according to the number of amide groups in the molecule, eight are diamides, and three are triamides that were inactive. 5-Chloro-2-hydroxy-N-[(2S)- 4-(methylsulfanyl)-1-oxo-1-{[4-(trifluoromethyl)phenyl]amino}butan-2-yl]benzamide (3e) and 5-chloro-2-hydroxy-N-[(2S)-(4-methyl-1-oxo-1-{[4-(trifluoromethyl)phenyl]amino)pentan-2-yl)benzamide (3f) showed the broadest spectrum of activity against all tested species/isolates comparable to the used standards (ampicillin and isoniazid). Six diamides showed high antistaphylococcal activity with MICs ranging from 0.070 to 8.95 μM. Three diamides showed anti-enterococcal activity with MICs ranging from 4.66 to 35.8 μM, and the activities of 3f and 3e against M. tuberculosis and M. smegmatis were MICs of 18.7 and 35.8 μM, respectively. All the active compounds were microbicidal. It was observed that the connecting linker between the chlorsalicylic and 4-CF3-anilide cores must be substituted with a bulky and/or lipophilic chain such as isopropyl, isobutyl, or thiabutyl chain. Anticancer activity on THP-1 cells IC50 ranged from 1.4 to >10 µM and increased with increasing lipophilicity.

Niclosamide inhibits hepatitis E virus through suppression of NF-kappaB signalling

Hepatitis E virus (HEV) infection can cause severe acute hepatitis in pregnant women and chronic infection in immunocompromised patients, promoting the development of effective antiviral therapies. In this study, we identified niclosamide, a widely used anthelmintic drug, as a potent inhibitor of HEV replication in a range of subgenomic and full-length HEV models, which are based on human cell lines and liver organoids harbouring genotype 1 and 3 HEV strains. Niclosamide is known to have multiple cellular targets including the inhibition of STAT3 and NFκB signaling pathways. Although HEV activates STAT3, we excluded its involvement in the anti-HEV activity of niclosamide. Interestingly, HEV infection activated NFκB and activation of NFκB promoted viral replication. Consistently, stable silencing of NFκB by lentiviral RNAi inhibited HEV replication. By targeting NFκB signaling, we further revealed its role in mediating the anti-HEV action of niclosamide. These results demonstrated that niclosamide potently inhibits HEV replication by inhibiting NFκB signaling but independent of STAT3. Our findings support the potential of repurposing niclosamide for treating HEV infection.

Oncolytic Virotherapy: From Bench to Bedside

Oncolytic viruses are naturally occurring or genetically engineered viruses that can replicate preferentially in tumor cells and inhibit tumor growth. These viruses have been considered an effective anticancer strategy in recent years. They mainly function by direct oncolysis, inducing an anticancer immune response and expressing exogenous effector genes. Their multifunctional characteristics indicate good application prospects as cancer therapeutics, especially in combination with other therapies, such as radiotherapy, chemotherapy and immunotherapy. Therefore, it is necessary to comprehensively understand the utility of oncolytic viruses in cancer therapeutics. Here, we review the characteristics, antitumor mechanisms, clinical applications, deficiencies and associated solutions, and future prospects of oncolytic viruses.

Niclosamide for Covid-19: bridging the gap

AIM/PURPOSE

Niclosamide (NCL) is an anthelminthic drug, which is widely used to treat various diseases due to its pleiotropic anti-inflammatory and antiviral activities. NCL modulates of uncoupling oxidative phosphorylation and different signaling pathways in human biological processes. The wide-spectrum antiviral effect of NCL makes it a possible candidate for recent pandemic SARS-CoV-2 infection and may reduce Covid-19 severity. Therefore, the aim of the present study was to review and clarify the potential role of NCL in Covid-19.

METHODS

This study reviewed and highlighted the protective role of NCL therapy in Covid-19. A related literature search in PubMed, Scopus, Web of Science, Google Scholar, and Science Direct was done.

RESULTS

NCL has noteworthy anti-inflammatory and antiviral effects. The primary antiviral mechanism of NCL is through neutralization of endosomal PH and inhibition of viral protein maturation. NCL acts as a proton carrier, inhibits homeostasis of endosomal PH, which limiting of viral proliferation and release. The anti-inflammatory effects of NCL are mediated by suppression of inflammatory signaling pathways and release of pro-inflammatory cytokines. However, the major limitation in using NCL is low aqueous solubility, which reduces oral bioavailability and therapeutic serum concentration that reducing the in vivo effect of NCL against SARS-CoV-2.

CONCLUSIONS

NCL has anti-inflammatory and immune regulatory effects by modulating the release of pro-inflammatory cytokines, inhibition of NF-κB /NLRP3 inflammasome and mTOR signaling pathway. NCL has an anti-SARS-CoV-2 effect via interruption of viral life-cycle and/or induction of cytopathic effect. Prospective clinical studies and clinical trials are mandatory to confirm the potential role of NCL in patients with Covid-19 concerning the severity and clinical outcomes.

Quantitative prediction model for affinity of drug-target interactions based on molecular vibrations and overall system of ligand-receptor

Background

The study of drug–target interactions (DTIs) affinity plays an important role in safety assessment and pharmacology. Currently, quantitative structure–activity relationship (QSAR) and molecular docking (MD) are most common methods in research of DTIs affinity. However, they often built for a specific target or several targets, and most QSAR and MD methods were based either on structure of drug molecules or on structure of receptors with low accuracy and small scope of application. How to construct quantitative prediction models with high accuracy and wide applicability remains a challenge. To this end, this paper screened molecular descriptors based on molecular vibrations and took molecule-target as a whole system to construct prediction models with high accuracy-wide applicability based on dissociation constant (Kd) and concentration for 50% of maximal effect (EC50), and to provide reference for quantifying affinity of DTIs.

Results

After comprehensive comparison, the results showed that RF models are optimal models to analyze and predict DTIs affinity with coefficients of determination (R²) are all greater than 0.94. Compared to the quantitative models reported in literatures, the RF models developed in this paper have higher accuracy and wide applicability. In addition, E-state molecular descriptors associated with molecular vibrations and normalized Moreau-Broto autocorrelation (G3), Moran autocorrelation (G4), transition-distribution (G7) protein descriptors are of higher importance in the quantification of DTIs.

Conclusion

Through screening molecular descriptors based on molecular vibrations and taking molecule-target as whole system, we obtained optimal models based on RF with more accurate-widely applicable, which indicated that selection of molecular descriptors associated with molecular vibrations and the use of molecular-target as whole system are reliable methods for improving performance of models. It can provide reference for quantifying affinity of DTIs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-021-04389-w.

Niclosamide encapsulated in mesoporous silica and geopolymer: A potential oral formulation for COVID-19

COVID-19 is a rapidly evolving emergency, for which there have been no specific medication found yet. Therefore, it is necessary to find a solution for this ongoing pandemic with the aid of advanced pharmaceutics. What is proposed as a solution is the repurposing of FDA approved drug such as niclosamide (NIC) having multiple pathways to inactivate the SARS-CoV-2, the specific virion that induces COVID-19. However, NIC is hardly soluble in an aqueous solution, thereby poor bioavailability, resulting in low drug efficacy. To overcome such a disadvantage, we propose here an oral formulation based on Tween 60 coated drug delivery system comprised of three different mesoporous silica biomaterials like MCM-41, SBA-15, and geopolymer encapsulated with NIC molecules. According to the release studies under a gastro/intestinal solution, the cumulative NIC release out of NIC-silica nanohybrids was found to be greatly enhanced to ~97% compared to the solubility of intact NIC (~40%) under the same condition. We also confirmed the therapeutically relevant bioavailability for NIC by performing pharmacokinetic (PK) study in rats with NIC-silica oral formulations. In addition, we discussed in detail how the PK parameters could be altered not only by the engineered porous structure and property, but also by interfacial interactions between ion-NIC dipole, NIC-NIC dipoles and/or pore wall-NIC van der Waals in the intra-pores of silica nanoparticles.

Exploring the selectivity of guanine scaffold in anticancer drug development by computational repurposing approach

Drug repurposing is one of the modern techniques used in the drug discovery to find out the new targets for existing drugs. Insilico methods have a major role in this approach. We used 60 FDA approved antiviral drugs reported in the last 50 years to screen against different cancer cell receptors. The thirteen compounds selected after virtual screening are analyzed for their druggability based on ADMET parameters and found the selectivity of guanine derivatives-didanosine, entecavir, acyclovir, valganciclovir, penciclovir, ganciclovir and valacyclovir as suitable candidates. The pharmacophore model, AARR, suggested based on the common feature alignment, shows that the two fused rings as in guanine and two acceptors-one from keto-oxygen (A5) and other from the substituent attached to nitrogen of imidazole ring (A4) give the druggability to the guanine derivatives. The NBO analysis on N9 is indicative of charge distribution from the ring to substituents, which results in delocalization of negative character in most of the ligands. The molecular dynamics simulations also pointed out the importance of guanine scaffold, which stabilizes the ligands inside the binding pocket of the receptor. All these results are indicative of the selectivity of guanine scaffold in anticancer drug development, especially as PARP1 inhibitors in breast, ovarian and prostate cancer. As these seven molecules are already approved by FDA, we can safely go for further preclinical trials.

Design, synthesis and in vitro biological evaluation of a novel class of anti-adenovirus agents based on 3-amino-1,2-propanediol

Nowadays there is not an effective drug for the treatment of infections caused by human adenovirus (HAdV) which supposes a clinical challenge, especially for paediatric and immunosuppressed patients. Here, we describe the design, synthesis and biological evaluation as anti-adenovirus agents of a new library (57 compounds) of diester, monoester and triazole derivatives based on 3-amino-1,2-propanediol skeleton. Seven compounds (17, 20, 26, 34, 44, 60 and 66) were selected based on their high anti-HAdV activity at low micromolar concentration (IC₅₀ from 2.47 to 5.75 µM) and low cytotoxicity (CC₅₀ from 28.70 to >200 µM). In addition, our mechanistic assays revealed that compounds 20 and 44 might be targeting specifically the HAdV DNA replication process, and compound 66 would be targeting HAdV E1A mRNA transcription. For compounds 17, 20, 34 and 60, the mechanism of action seems to be associated with later steps after HAdV DNA replication.

Potential COVID-19 Therapeutic Agents and Vaccines: An Evidence-Based Review

Since the early days of 2020, the severe acute respiratory syndrome coronavirus 2 pandemic has become a global health concern. Currently, some therapies and vaccines have received US Food and Drug Administration approval or emergency use authorization for the management of coronavirus disease 2019. According to the pathophysiology of the disease, several medications have been evaluated in different clinical conditions of the disease. Evidence-based reviewing and categorizing these medications can guide the clinicians to select the proper medications according to each patient's condition. Therefore, we performed this review to categorize the coronavirus disease 2019 potential therapeutics and vaccines.

Heat Shock Protein 90 Chaperones E1A Early Protein of Adenovirus 5 and Is Essential for Replication of the Virus

Adenovirus infections tend to be mild, but they may pose a serious threat for young and immunocompromised individuals. The treatment is complicated because there are no approved safe and specific drugs for adenovirus infections. Here, we present evidence that 17-(Allylamino)-17-demethoxygeldanamycin (17-AAG), an inhibitor of Hsp90 chaperone, decreases the rate of human adenovirus 5 (HAdV-5) replication in cell cultures by 95%. 17-AAG inhibited the transcription of early and late genes of HAdV-5, replication of viral DNA, and expression of viral proteins. 6 h after infection, Hsp90 inhibition results in a 6.3-fold reduction of the newly synthesized E1A protein level without a decrease in the E1A mRNA level. However, the Hsp90 inhibition does not increase the decay rate of the E1A protein that was constitutively expressed in the cell before exposure to the inhibitor. The co-immunoprecipitation proved that E1A protein interacted with Hsp90. Altogether, the presented results show, for the first time. that Hsp90 chaperones newly synthesized, but not mature, E1A protein. Because E1A serves as a transcriptional co-activator of adenovirus early genes, the anti-adenoviral activity of the Hsp90 inhibitor might be explained by the decreased E1A level.

Emerging antiviral therapeutics for human adenovirus infection: Recent developments and novel strategies

Human adenoviruses (HAdV) are ubiquitous human pathogens that cause a significant burden of respiratory, ocular, and gastrointestinal illnesses. Although HAdV infections are generally self-limiting, pediatric and immunocompromised individuals are at particular risk for developing severe disease. Currently, no approved antiviral therapies specific to HAdV exist. Recent outbreaks underscore the need for effective antiviral agents to treat life-threatening infections. In this review we will focus on recent developments in search of potential therapeutic agents for controlling HAdV infections, with a focus on those targeting post-entry stages of the virus replicative cycle.

Discovery of a Small Molecule Inhibitor of Human Adenovirus Capable of Preventing Escape from the Endosome

Human adenoviruses (HAdVs) display a wide range of tissue tropism and can cause an array of symptoms from mild respiratory illnesses to disseminated and life-threatening infections in immunocompromised individuals. However, no antiviral drug has been approved specifically for the treatment of HAdV infections. Herein, we report our continued efforts to optimize salicylamide derivatives and discover compound 16 (JMX0493) as a potent inhibitor of HAdV infection. Compound 16 displays submicromolar IC₅₀ values, a higher selectivity index (SI > 100) and 2.5-fold virus yield reduction compared to our hit compound niclosamide. Moreover, unlike niclosamide, our mechanistic studies suggest that the antiviral activity of compound 16 against HAdV is achieved through the inhibition of viral particle escape from the endosome, which bars subsequent uncoating and the presentation of lytic protein VI.

Discovery of Novel Substituted N-(4-Amino-2-chlorophenyl)-5-chloro-2-hydroxybenzamide Analogues as Potent Human Adenovirus Inhibitors

An effective therapy for human adenovirus (HAdV) infections in immunocompromised patients and healthy individuals with community-acquired pneumonia remains an unmet medical need. We herein reported a series of novel substituted N-(4-amino-2-chlorophenyl)-5-chloro-2-hydroxybenzamide analogues as potent HAdV inhibitors. Compounds 6, 15, 29, 40, 43, 46, 47, and 54 exhibited increased selectivity indexes (SI > 100) compared to the lead compound niclosamide, while maintaining sub-micromolar to low micromolar potency against HAdV. The preliminary mechanistic studies indicated that compounds 6 and 43 possibly target the HAdV DNA replication process, while compounds 46 and 47 suppress later steps of HAdV life cycle. Notably, among these derivatives, compound 15 showed improved anti-HAdV activity (IC₅₀ = 0.27 μM), significantly decreased cytotoxicity (CC₅₀ = 156.8 μM), and low in vivo toxicity (maximum tolerated dose = 150 mg/kg in hamster) as compared with niclosamide, supporting its further in vivo efficacy studies for the treatment of HAdV infections.

Drugs, host proteins and viral proteins: how their promiscuities shape antiviral design

The reciprocal nature of drug specificity and target specificity implies that the same is true for their respective promiscuities. Protein promiscuity has two broadly different types of footprint in drug design. The first is relaxed specificity of binding sites for substrates, inhibitors, effectors or cofactors. The second involves protein-protein interactions of regulatory processes such as signal transduction and transcription, and here protein intrinsic disorder plays an important role. Both viruses and host cells exploit intrinsic disorder for their survival, as do the design and discovery programs for antivirals. Drug action, strictly speaking, always relies upon promiscuous activity, with drug promiscuity enlarging its scope. Drug repurposing searches for additional promiscuity on the part of both the drug and the target in the host. Understanding the subtle nuances of these promiscuities is critical in the design of novel and more effective antivirals.

Adenovirus infection and disease in recipients of hematopoietic cell transplantation

PURPOSE OF REVIEW

To provide an update on risk factors associated with adenovirus (ADV) infection in patients after hematopoietic cell transplant (HCT) and on options for ADV monitoring and treatment in the setting of HCT.

RECENT FINDINGS

Among patients undergoing HCT, ADV infection continues to be more common amongst those receiving a T-cell-depleted or graft other than from a matched-related donor. Among children undergoing HCT, reactivation in the gastrointestinal tract appears to be the most common source, and the virus is detectable by quantitative PCR in the stool before it is detectable in the blood. Thus, screening for the virus in the stool of these children may allow for preemptive therapy to reduce mortality. Brincidofovir, although still not approved by any regulatory agency, remains a potential agent for preemptive therapy and for salvage in cases not responding to cidofovir. Rapidly generated off-the-shelf virus-specific T cells may facilitate adoptive cell therapy in populations with a special need and previously not eligible for adoptive cell therapy, such as cord blood recipients.

SUMMARY

ADV infection continues to adversely affect survival in HCT recipients. Screening stool in children and preemptive therapy may reduce mortality. Brincidofovir and adoptive T-cell therapy remain potential options for treatment.

In vitro co-infection by cytomegalovirus improves the antiviral activity of ganciclovir against human adenovirus

Human adenovirus (HAdV) infection has an important clinical impact in the immunosuppressed population and is associated with high morbidity and mortality rates. The lack of a specific, safe and effective antiviral treatment against HAdV makes necessary the search for new therapeutic options. The aim of this study was to evaluate the in vitro activity of ganciclovir (GCV) against HAdV in co-infection by human cytomegalovirus (HCMV) and HAdV in cellular cultures. Quantitative real-time polymerase chain reaction (qPCR) was used to measure HAdV and HCMV DNA replication efficiency in monocultures and in co-infection situations in the presence of both cidofovir (CDV) and GCV. The effects of GCV and CDV were also evaluated in a burst assay (used to measure the production of virus particles) for both viruses, alone and in combination. GCV decreased by 1-log the HAdV DNA replication efficiency in co-infection with HCMV compared with its activity in HAdV monoculture. The burst assay showed that the reductions in virus yield in the presence of GCV were higher for HCMV and co-infection than for HAdV in monoculture (145.2±35.5- vs. 116.4±27.3- vs. 23.0±10.0-fold, respectively, P<0.05). The improved anti-HAdV activity of GCV during co-infection may be because of the more efficient phosphorylation of GCV by the HCMV protein kinase, UL97. Patients treated with GCV as pre-emptive therapy for HCMV infection may be considered as low-risk for developing HAdV infections; however, further evaluations are required to confirm these results.

Broad Spectrum Antiviral Agent Niclosamide and Its Therapeutic Potential

The recent outbreak of coronavirus disease 2019 (COVID-19) highlights an urgent need for therapeutics. Through a series of drug repurposing screening campaigns, niclosamide, an FDA-approved anthelminthic drug, was found to be effective against various viral infections with nanomolar to micromolar potency such as SARS-CoV, MERS-CoV, ZIKV, HCV, and human adenovirus, indicating its potential as an antiviral agent. In this brief review, we summarize the broad antiviral activity of niclosamide and highlight its potential clinical use in the treatment of COVID-19.

Broad Spectrum Antiviral Agent Niclosamide and Its Therapeutic Potential

The recent outbreak of coronavirus disease 2019 (COVID-19) highlights an urgent need for therapeutics. Through a series of drug repurposing screening campaigns, niclosamide, an FDA-approved anthelminthic drug, was found to be effective against various viral infections with nanomolar to micromolar potency such as SARS-CoV, MERS-CoV, ZIKV, HCV, and human adenovirus, indicating its potential as an antiviral agent. In this brief review, we summarize the broad antiviral activity of niclosamide and highlight its potential clinical use in the treatment of COVID-19.

Antiviral Effects of Novel 2-Benzoxyl-Phenylpyridine Derivatives

Coxsackievirus B3 (CVB3) is the most common cause of acute and chronic viral myocarditis, primarily in children, while human adenovirus infections represent a significant cause of morbidity and mortality worldwide, in people of all ages. A series of novel 2-benzoxyl-phenylpyridine derivatives were evaluated for their potential antiviral activities against CVB3 and adenovirus type 7 (ADV7). Preliminary assays indicated that some of these compounds exhibited excellent antiviral effects on both CVB3 and ADV7 viruses; they could effectively inhibit virus-induced cytopathic effects, reduce viral progeny yields, and had similar or superior antiviral activities compared with the control drug, ribavirin. Further, these compounds targeted the early stages of CVB3 replication in cells, including viral RNA replication and protein synthesis, rather than inactivating the virus directly, inhibiting virus adsorption/entry, or affecting viral release from cells. Our data demonstrate that the tested 2-benzoxyl-phenylpyridine derivatives are effective inhibitors of CVB3 and ADV7, raising the possibility that these compounds might be feasible candidates for anti-viral agents.

Structure-Activity Relationship Studies on Diversified Salicylamide Derivatives as Potent Inhibitors of Human Adenovirus Infection

The effective treatment of adenovirus (HAdV) infections in immunocompromised patients still poses great challenges. Herein, we reported our continued efforts to optimize a series of salicylamide derivatives as potent inhibitors of HAdV infection. Of these, nine compounds (11, 13, 14, 17, 20, 58, 60, 62, and 70) showed significantly improved anti-HAdV activities with nanomolar to submicromolar IC₅₀ values and high selectivity indexes (SI > 100), indicating better safety windows, compared to those of the lead compound niclosamide. Our mechanistic assays suggest that compounds 13, 62, and 70 exert their activities in the HAdV entry pathway, while compounds 14 and 60 likely target the HAdV DNA replication, and 11, 17, 20, and 58 inhibit later steps after DNA replication. Given the broad anti-viral activity profile of niclosamide, these derivatives may also offer therapeutic potential for other viral infections.

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Rafoxanide promotes apoptosis and autophagy of gastric cancer cells by suppressing PI3K /Akt/mTOR pathway

Rafoxanide is commonly used as anti-helminthic medicine in veterinary medicine, a main compound of salicylanilide. Previous studies have reported that rafoxanide, as an inhibitor of BRAF V600E mutant protein, inhibits the growth of colorectal cancer, multiple myeloma, and skin cancer. However, its therapeutic effect on gastric cancer (GC) and the potential mechanism has not been investigated. Here, we have found that rafoxanide inhibited the proliferation of GC cells in vitro, arrested the cell cycle in the G0/G1 phase, and promoted apoptosis and autophagy in GC cells. Treatment with specific autophagy inhibitor 3-methyladenine drastically inhibited the apoptotic cell death effect by suppressing the switch from autophagy to apoptosis. Mechanistically, we found that rafoxanide inhibited the growth of GC cells in vitro by inhibiting the activity of the PI3K/Akt/mTOR signaling pathway. This process induced autophagy, which essentially resulted in the apoptosis of GC cells. Results from subcutaneous implanted tumor models in nude mice also indicated that rafoxanide inhibited the growth of GC cells in vivo. Taken together, our findings revealed that rafoxanide inhibited the growth of GC cells both in vitro and vivo, indicating a potential drug candidate for the treatment of GC.

Acute and Subacute Toxicity Assessment of Oxyclozanide in Wistar Rats

Oxyclozanide is an effective anthelmintic and has shown good properties in other ways including anti-adenovirus, anti-biofilm, antifungal, and antibacterial activity. This study aimed to investigate the acute and subacute 28-days repeated dose oral toxicity of an oxyclozanide suspension in Wistar rats. A high oral lethal dose (LD₅₀) of 3,707 mg/kg was observed in the acute toxicity test. During the 28-days time period, no obvious adverse effects or death were detected. Histopathological changes were observed in the heart, liver, and kidney of animals treated with high dose of oxyclozanide. Based on the hematological parameters, there were no statistical differences between the oxyclozanide-treated group and the control group. For biochemistry assays, ALP, AST, GLU, TBIL, GLO, TG, BUN, UA, LDH, and CK were statistically changed in the treatment groups. These data suggested that the LD₅₀ of oxyclozanide was ~3,707 mg/kg body weight (BW), and the lowest observed adverse effect level (LOAEL) of oxyclozanide was at a dose of 74 mg/kg in rats.

Drug development against human adenoviruses and its advancement by Syrian hamster models

The symptoms of human adenovirus infections are generally mild and self-limiting. However, these infections have been gaining importance in recent years because of a growing number of immunocompromised patients. Solid organ and hematopoietic stem cell transplant patients are subjected to severe immunosuppressive regimes and cannot efficaciously eliminate virus infections. In these patients, adenovirus infections can develop into deadly multi-organ disseminated disease. Presently, in the absence of approved therapies, physicians rely on drugs developed for other purposes to treat adenovirus infections. As there is a need for anti-adenoviral therapies, researchers have been developing new agents and repurposing existing ones to treat adenovirus infections. There are several small molecule drugs that are being tested for their efficacy against human adenoviruses; some of these have reached clinical trials, while others are still in the preclinical phase. Besides these compounds, research on immunotherapy against adenoviral infection has made significant progress, promising another modality for treatment. The availability of an animal model confirmed the activity of some drugs already in clinical use while proving that others are inactive. This led to the identification of several lead compounds that await further development. In the present article, we review the current status of anti-adenoviral therapies and their advancement by in vivo studies in the Syrian hamster model.

Overview of Recent Strategic Advances in Medicinal Chemistry

Introducing novel strategies, concepts, and technologies that speed up drug discovery and the drug development cycle is of great importance both in the highly competitive pharmaceutical industry as well as in academia. This Perspective aims to present a "big-picture" overview of recent strategic innovations in medicinal chemistry and drug discovery.

Expanding the activity spectrum of antiviral agents

Broad-spectrum antivirals (BSAs) are agents that inhibit replication of several human viruses. Here, we review 108 approved, investigational, and experimental BSAs, for which safety profiles in humans are available. The most effective and tolerable BSAs could reinforce the arsenal of available antiviral therapeutics pending the results of further pre-clinical and clinical studies.