Orally available nucleoside analog UMM-766 provides protection in a murine model of orthopox disease.

Although smallpox has been eradicated, other orthopoxviruses continue to be a public health concern as exemplified by the ongoing Mpox (formerly monkeypox) global outbreak. While medical countermeasures (MCMs) previously approved by the Food and Drug Administration for the treatment of smallpox have been adopted for Mpox, previously described vulnerabilities coupled with the questionable benefit of at least one of the therapeutics during the 2022 Mpox outbreak reinforce the need for identifying and developing other MCMs against orthopoxviruses. Here, we screened a panel of Merck proprietary small molecules and identified a novel nucleoside inhibitor with potent broad-spectrum antiviral activity against multiple orthopoxviruses. Efficacy testing of a 7-day dosing regimen of the orally administered nucleoside in a murine model of severe orthopoxvirus infection yielded a dose-dependent increase in survival. Treated animals had greatly reduced lesions in the lung and nasal cavity, particularly in the 10 µg/mL dosing group. Viral levels were also markedly lower in the UMM-766-treated animals. This work demonstrates that this nucleoside analog has anti-orthopoxvirus efficacy and can protect against severe disease in a murine orthopox model.IMPORTANCEThe recent monkeypox virus pandemic demonstrates that members of the orthopoxvirus, which also includes variola virus, which causes smallpox, remain a public health issue. While currently FDA-approved treatment options exist, risks that resistant strains of orthopoxviruses may arise are a great concern. Thus, continued exploration of anti-poxvirus treatments is warranted. Here, we developed a template for a high-throughput screening assay to identify anti-poxvirus small-molecule drugs. By screening available drug libraries, we identified a compound that inhibited orthopoxvirus replication in cell culture. We then showed that this drug can protect animals against severe disease. Our findings here support the use of existing drug libraries to identify orthopoxvirus-targeting drugs that may serve as human-safe products to thwart future outbreaks.

Effect of interferon therapy on quality of life in patients with chronic hepatitis B.

Interferon therapy is the most effective treatment for achieving clinical cure in chronic hepatitis B (CHB) patients. However, the treatment outcomes of interferon therapy are uncertain, multiple side effects can occur during treatment, and the treatment is expensive. Although these characteristics may affect patients' quality of life, research examining this topic is limited. We used a cross-sectional design to examine 100 CHB patients receiving interferon, 100 receiving nucleoside/nucleotide analogues, and 87 receiving non-antiviral treatment. Characteristic information, the Hepatitis B Quality of Life Instrument, Connor Davidson Resilience Scale, and Work Productivity and Activity Impairment Questionnaire were used to collect information. We found that quality of life in the interferon treatment group was higher than that in the non-antiviral treatment and nucleoside/nucleotide analogue treatment groups (p < 0.05). The factors influencing quality of life were resilience, presenteeism, hair loss, and antiviral treatment (p < 0.05). Although interferon therapy has some potential side effects, the results suggested that it did not negatively affect quality of life. Overall, interferon therapy did not have a major impact on CHB patients' daily lives and work.

A modified nucleoside O6-methyl-2'-deoxyguanosine-5'-triphosphate exhibits anti-glioblastoma activity in a caspase-independent manner.

Resistance to temozolomide (TMZ), the frontline chemotherapeutic agent for glioblastoma (GBM), has emerged as a formidable obstacle, underscoring the imperative to identify alternative therapeutic strategies to improve patient outcomes. In this study, we comprehensively evaluated a novel agent, O6-methyl-2'-deoxyguanosine-5'-triphosphate (O6-methyl-dGTP) for its anti-GBM activity both in vitro and in vivo. Notably, O6-methyl-dGTP exhibited pronounced cytotoxicity against GBM cells, including those resistant to TMZ and overexpressing O6-methylguanine-DNA methyltransferase (MGMT). Mechanistic investigations revealed that O6-methyl-dGTP could be incorporated into genomic DNA, disrupting nucleotide pools balance, and inducing replication stress, resulting in S-phase arrest and DNA damage. The compound exerted its anti-tumor properties through the activation of AIF-mediated apoptosis and the parthanatos pathway. In vivo studies using U251 and Ln229 cell xenografts supported the robust tumor-inhibitory capacity of O6-methyl-dGTP. In an orthotopic transplantation model with U87MG cells, O6-methyl-dGTP showcased marginally superior tumor-suppressive activity compared to TMZ. In summary, our research, for the first time, underscores the potential of O6-methyl-dGTP as an effective candidate against GBM, laying a robust scientific groundwork for its potential clinical adoption in GBM treatment regimens.

Anticonvulsant effect of equilibrative nucleoside transporters 1 inhibitor in a mouse model of Dravet syndrome.

There are limited therapeutic options for patients with Dravet syndrome (DS). The equilibrative nucleoside transporters 1 (ENT1) mediate both the influx and efflux of adenosine across the cell membrane exerted beneficial effects in the treatment of epilepsy. This study aimed to evaluate the anticonvulsant effect of the ENT1 inhibitor in an animal model of DS (Scn1aE1099X/+ mice). J7 (5 mg/kg) treatment was efficacious in elevating seizure threshold in Scn1aE1099X/+ mice after hyperthermia exposure. Moreover, the J7 treatment significantly reduced the frequency of spontaneous excitatory post-synaptic currents (sEPSCs, ~35% reduction) without affecting the amplitude in dentate gyrus (DG) granule cells. Pretreatment with the adenosine A1 receptor (A1R) antagonist, DPCPX, abolished the J7 effects on sEPSCs. These observations suggest that the J7 shows an anticonvulsant effect in hyperthermia-induced seizures in Scn1aE1099X/+ mice. This effect possibly acts on presynaptic A1R-mediated signaling modulation in granule cells.

Liver Carcinogenesis Suppression in Chronic Hepatitis B in the Nucleoside Analogues Era.

There is a strong association between the distribution of Hepatitis B virus (HBV) carriers and the incidence of hepatocellular carcinoma (HCC). About 60% of HCC in Japan is caused by viral hepatitis. Ten to 15 percent of hepatitis virus-related HCCs derive from HBV. Recently, antiviral therapy against HBV has developed, and interferon therapy and nucleos(t)ide analogues (NAs) are currently the standard of care. NAs exhibit antiviral activity by inhibiting DNA polymerase and suppressing HBV replication. NAs are highly effective in suppressing HBV-DNA and improving alanine aminotransferase. The long-term treatment goal for chronic hepatitis B is HB surface antigen (HBsAg) loss. However, the number of patients who achieve HBsAg loss by NA (i.e., functional cure) is low and there have been cases of HCC incidence during (or after) NA therapy. In this article, we review the efficacy of NA therapy in suppressing HBV-derived carcinogenesis.

The Application of Prodrugs as a Tool to Enhance the Properties of Nucleoside Reverse Transcriptase Inhibitors.

Antiretroviral Therapy (ART) is an effective treatment for human immunodeficiency virus (HIV) which has transformed the highly lethal disease, acquired immunodeficiency syndrome (AIDS), into a chronic and manageable condition. However, better methods need to be developed for enhancing patient access and adherence to therapy and for improving treatment in the long term to reduce adverse effects. From the perspective of drug discovery, one promising strategy is the development of anti-HIV prodrugs. This approach aims to enhance the efficacy and safety of treatment, promoting the development of more appropriate and convenient systems for patients. In this review, we discussed the use of the prodrug approach for HIV antiviral agents and emphasized nucleoside reverse transcriptase inhibitors. We comprehensively described various strategies that are used to enhance factors such as water solubility, bioavailability, pharmacokinetic parameters, permeability across biological membranes, chemical stability, drug delivery to specific sites/organs, and tolerability. These strategies might help researchers conduct better studies in this field. We also reported successful examples from the primary therapeutic classes while discussing the advantages and limitations. In this review, we highlighted the key trends in the application of the prodrug approach for treating HIV/AIDS.

Repurposing nucleoside reverse transcriptase inhibitors (NRTIs) to slow aging.

Repurposing drugs already approved in the clinic to be used off-label as geroprotectors, compounds that combat mechanisms of aging, are a promising way to rapidly reduce age-related disease incidence in society. Several recent studies have found that a class of drugs-nucleoside reverse transcriptase inhibitors (NRTIs)-originally developed as treatments for cancers and human immunodeficiency virus (HIV) infection, could be repurposed to slow the aging process. Interestingly, these studies propose complementary mechanisms that target multiple hallmarks of aging. At the molecular level, NRTIs repress LINE-1 elements, reducing DNA damage, benefiting the hallmark of aging of 'Genomic Instability'. At the organellar level, NRTIs inhibit mitochondrial translation, activate ATF-4, suppress cytosolic translation, and extend lifespan in worms in a manner related to the 'Loss of Proteostasis' hallmark of aging. Meanwhile, at the cellular level, NRTIs inhibit the P2X7-mediated activation of the inflammasome, reducing inflammation and improving the hallmark of aging of 'Altered Intercellular Communication'. Future development of NRTIs for human aging health will need to balance out toxic side effects with the beneficial effects, which may occur in part through hormesis.

Molecular and functional profiling of chemotolerant cells unveils nucleoside metabolism-dependent vulnerabilities in medulloblastoma.

Chemotherapy resistance is considered one of the main causes of tumor relapse, still challenging researchers for the identification of the molecular mechanisms sustaining its emergence. Here, we setup and characterized chemotherapy-resistant models of Medulloblastoma (MB), one of the most lethal pediatric brain tumors, to uncover targetable vulnerabilities associated to their resistant phenotype. Integration of proteomic, transcriptomic and kinomic data revealed a significant deregulation of several pathways in resistant MB cells, converging to cell metabolism, RNA/protein homeostasis, and immune response, eventually impacting on patient outcome. Moreover, resistant MB cell response to a large library of compounds through a high-throughput screening (HTS), highlighted nucleoside metabolism as a relevant vulnerability of chemotolerant cells, with peculiar antimetabolites demonstrating increased efficacy against them and even synergism with conventional chemotherapeutics. Our results suggest that drug-resistant cells significantly rewire multiple cellular processes, allowing their adaptation to a chemotoxic environment, nevertheless exposing alternative actionable susceptibilities for their specific targeting.

Air pollution impede ALT normalization in chronic hepatitis B patients treated with nucleotide/nucleoside analogues.

Biochemical response is an important prognostic indicator in chronic hepatitis B (CHB) patients receiving nucleotide/nucleoside analogues (NAs). However, the effects of air pollution in alanine aminotransferase (ALT) normalization remain elusive. This longitudinal study recruited 80 hepatitis B e antigen-negative CHB patients who received NAs. ALT levels were measured during the first year of anti-hepatitis B virus therapy. Normal ALT levels were defined as <19 U/L for females and <30 U/L for males, and the risk factors associated with ALT abnormalities were analyzed. The daily estimations of air pollutants (particulate matter ≤2.5 µm in diameter (PM2.5), nitrogen dioxide, ozone (O3), and benzene) were aggregated into the mean estimation for the previous month based on the date of recruitment (baseline) and 1 year later. Sixteen patients (20.0%) had a baseline ALT > 40 U/L; overall, 41 (51.6%) had an abnormal ALT (≥19 U/L for females and ≥ 30 U/L for males). After 1 year of NA therapy, 75 patients (93.8%) had undetectable hepatitis B virus DNA levels. Mean post-treatment ALT levels were significantly lower than mean pretreatment levels (21.3 vs 30.0 U/L, respectively; P < .001). The proportion of patients with a normal ALT was also significantly higher after versus before treatment (71.2% vs 51.2%, respectively; P = .001). The strongest factors associated with ALT abnormality after 1 year of NA treatment were body mass index (odds ratio [OR], 1.28; 95% confidence interval [CI], 1.05-1.54; P = .01) and ozone level (OR, 1.11; 95% CI, 1.02-1.22; P = .02). Among hepatitis B e antigen-negative CHB patients with relatively low viral loads, 1 year of NA treatment improved ALT levels after the adjustment for confounding factors and increased the proportion of patients with normal ALT levels. Air pollution affects the efficacy of ALT normalization.

Use of integrase inhibitors vs protease inhibitors is associated with improved HIV viral suppression.

BACKGROUND: Current guidelines for antiretroviral therapy in pregnancy include the use of a dual-nucleoside reverse transcriptase inhibitor with either an integrase strand transfer inhibitor or a ritonavir-boosted protease inhibitor, although there is no designation of which is the preferred option. OBJECTIVE: This study aimed to compare viral suppression at delivery among patients on dual-nucleoside reverse transcriptase inhibitors combined with either an integrase strand transfer inhibitor or a protease inhibitor. A hypothesis was made that the incidence of viral suppression is higher with the use of a dual-nucleoside reverse transcriptase inhibitor backbone combined with an integrase strand transfer inhibitor than with the use of a dual-nucleoside reverse transcriptase inhibitor backbone combined with a protease inhibitor. STUDY DESIGN: This study was an observational study of pregnant patients living with HIV who received prenatal care and delivered after 20 weeks of gestation at an urban safety net hospital. All pregnant patients with HIV were referred to a centralized clinic for HIV counseling, medication management, and prenatal care. Antiretroviral therapy was continued or initiated according to protocols based on national guidance. Among patients on a dual-nucleoside reverse transcriptase inhibitor backbone combined with integrase strand transfer inhibitor vs protease inhibitor at delivery, we compared the demographics and HIV disease characteristics, including year of diagnosis, viral load, and antiretroviral therapy class. The outcome of interest was viral suppression at delivery, defined as a viral load of <50 copies/mL. RESULTS: From January 2011 to December 2021, 604 patients on dual-nucleoside reverse transcriptase inhibitor met the inclusion criteria, including 411 patients (68%) on protease inhibitor and 193 patients (32%) on integrase strand transfer inhibitor at delivery. Demographic distribution was similar, and prenatal care was initiated at 12 weeks of gestation. Among the integrase strand transfer inhibitor group, 101 (17%) were on antiretroviral therapy at initiation of prenatal care compared with 169 (28%) in the protease inhibitor group. At delivery, the frequency of viral load suppression was higher among those on an integrase strand transfer inhibitor (147/193 [76%]) than among those on a protease inhibitor (275/411 [67%]) (odds ratio, 1.59; 95% confidence interval, 1.08-2.33). Among those with a detectable virus, quantitative viral load was not different. During the study period, the use of a protease inhibitor decreased, whereas the use of an integrase strand transfer inhibitor increased. CONCLUSION: Among pregnant patients living with HIV, viral suppression was more common among those on a dual-nucleoside reverse transcriptase inhibitor backbone combined with integrase strand transfer inhibitor than among those on a dual-nucleoside reverse transcriptase inhibitor backbone protease inhibitor at delivery. Our results support the use of dual-nucleoside reverse transcriptase inhibitor with integrase strand transfer inhibitor as a first-line antiretroviral therapy regimen in pregnancy.

[Impact of nucleosides analogues and nucleotide analogues on the outcomes related to chronic hepatitis B based on non-antiviral effects].

Nucleoside analogues and nucleotide analogues can not only achieve long-term viral suppression in the treatment of most CHB patients but also have a positive impact on other CHB therapeutic goals and an improved prognosis. A certain difference can be observed in the impact of nucleotide analogues such as TDF and TAF and nucleoside analogues such as ETV on the clinical outcomes of CHB. Studies on the mechanism of action indicate that apart from inhibiting the direct antiviral effects of HBV reverse transcriptase, these two categories of drugs exhibit distinct impacts on immune-related signaling pathways, gene expression, genome stability, and other non-antiviral mechanisms. This article reviews the evidence on the potential non-antiviral mechanism of action of nucleoside analogues and nucleotide analogues and proposes a preliminary explanation for the observation trend of nucleotide analogues having a comparative advantage in clinical outcomes in CHB patients based on the latest research advancement.

Therapeutic-oligonucleotides activated by nucleases (TOUCAN): A nanocarrier system for the specific delivery of clinical nucleoside analogues.

Nucleoside analogues have been in clinical use since 1960s and they are still used as the first therapeutic option for several cancers and viral infections, due to their high therapeutic efficacy. However, their wide clinical acceptance has been limited due to their high toxicity and severe side effects to patients. Herein, we report on a nanocarrier system that delivers nucleosides analogues in a target-specific manner, making nucleoside-based therapeutics safer and with the possibility to be used in other human conditions. This system, named, Therapeutic OligonUCleotides Activated by Nucleases" (TOUCAN) combines: i) the recognition power of oligonucleotides as substrates, ii) the use of nucleases as enzymatic biomarkers and iii) the clinical efficacy of nucleoside analogues, in a single approach. As a proof-of-concept, we report on a TOUCAN that is activated by a specific nuclease produced by bacteria and releases a therapeutic nucleoside, floxuridine. We demonstrate, for the first time, that, by incorporating a therapeutic nucleoside analogue into oligonucleotide probes, we can specifically inhibit bacterial growth in cultures. In this study, Staphylococcus aureus was selected as the targeted bacteria and the TOUCAN strategy successfully inhibited its growth with minimal inhibitory concentration (MIC) values ranging from 0.62 to 40 mg/L across all tested strains. Moreover, our results indicate that the intravenous administration of TOUCANs at a dose of 20 mg/kg over a 24-h period is a highly effective method for treating bacterial infections in a mouse model of pyomyositis. Importantly, no signs of toxicity were observed in our in vitro and in vivo studies. This work can significantly impact the current management of bacterial infections, laying the grounds for the development of a different class of antibiotics. Furthermore, it can provide a safer delivery platform for clinical nucleoside therapeutics in any human conditions, such as cancer and viral infection, where specific nuclease activity has been reported.

Nucleoside-based anticancer drugs: Mechanism of action and drug resistance.

Nucleoside-based drugs, recognized as purine or pyrimidine analogs, have been potent therapeutic agents since their introduction in 1950, deployed widely in the treatment of diverse diseases such as cancers, myelodysplastic syndromes, multiple sclerosis, and viral infections. These antimetabolites establish complex interactions with cellular molecular constituents, primarily via activation of phosphorylation cascades leading to consequential interactions with nucleic acids. However, the therapeutic efficacy of these agents is frequently compromised by the development of drug resistance, a continually emerging challenge in their clinical application. This comprehensive review explores the mechanisms of resistance to nucleoside-based drugs, encompassing a wide spectrum of phenomena from alterations in membrane transporters and activating kinases to changes in drug elimination strategies and DNA damage repair mechanisms. The critical analysis in this review underlines complex interactions of drug and cell and also guides towards novel therapeutic strategies to counteract resistance. The development of targeted therapies, novel nucleoside analogs, and synergistic drug combinations are promising approaches to restore tumor sensitivity and improve patient outcomes.

Baseline serum HBV RNA is associated with the risk of hepatitis flare after stopping nucleoside analog therapy in HBeAg-negative participants.

BACKGROUND AND AIMS: HBV RNA in peripheral blood reflects HBV cccDNA transcriptional activity and may predict clinical outcomes. The prospective Melbourne HBV-STOP trial studied nucleot(s)ide analog discontinuation in HBeAg-negative non-cirrhotic participants with long-term virological suppression. Ninety-six weeks after stopping treatment, the proportion of participants with virological relapse (HBV DNA > 2000 IU/mL), biochemical relapse (ALT > 2 × ULN and HBV DNA > 2000 IU/mL), or hepatitis flare (ALT > 5 × ULN and HBV DNA > 2000 IU/mL) was 89%, 58%, and 38%, respectively. We evaluated the ability of serum HBV RNA levels to predict these outcomes. APPROACH RESULTS: HBV RNA levels were measured using the Roche cobas 6800/8800 HBV RNA Investigational Assay. Sixty-five participants had baseline and longitudinal off-treatment specimens available for RNA testing. HBV RNA was detectable at baseline in 25% of participants and was associated with a higher risk of biochemical relapse (81% vs. 51%, p value 0.04) and hepatitis flare (63% vs. 31%, p value 0.04). Participants who had undetectable serum HBV RNA as well as HBsAg ≤ 100 IU/mL at baseline were less likely to experience virological relapse (4 of 9, 44%) than participants with detectable HBV RNA and HBsAg level > 100 IU/mL (15/15, 100%; p value 0.0009). Off-treatment levels of HBV RNA were correlated with HBV DNA and were associated with the risk of hepatitis flare. CONCLUSIONS: Serum HBV RNA may be a useful biomarker for guiding clinical decision-making before stopping nucleot(s)ide analog therapy. Baseline HBV RNA and HBsAg levels are associated with the risk of clinical relapse, hepatitis flare, and disease remission off-treatment.

In vitro and in vivo antiplasmodial evaluation of sugar-modified nucleoside analogues.

Drug-resistant Plasmodium falciparum (Pf) infections are a major burden on the population and the healthcare system. The establishment of Pf resistance to most existing antimalarial therapies has complicated the problem, and the emergence of resistance to artemisinin derivatives is even more concerning. It is increasingly difficult to cure malaria patients due to the limited availability of effective antimalarial drugs, resulting in an urgent need for more efficacious and affordable treatments to eradicate this disease. Herein, new nucleoside analogues including morpholino-nucleoside hybrids and thio-substituted nucleoside derivatives were prepared and evaluated for in vitro and in vivo antiparasitic activity that led a few hits especially nucleoside-thiopyranoside conjugates, which are highly effective against Pf3D7 and PfRKL-9 strains in submicromolar concentration. One adenosine derivative and four pyrimidine nucleoside analogues significantly reduced the parasite burden in mouse models infected with Plasmodium berghei ANKA. Importantly, no significant hemolysis and cytotoxicity towards human cell line (RAW) was observed for the hits, suggesting their safety profile. Preliminary research suggested that these thiosugar-nucleoside conjugates could be used to accelerate the antimalarial drug development pipeline and thus deserve further investigation.

Lumicitabine, an orally administered nucleoside analog, in infants hospitalized with respiratory syncytial virus (RSV) infection: Safety, efficacy, and pharmacokinetic results.

Respiratory syncytial virus (RSV) infection is the leading cause of infant hospitalizations and mortality. Lumicitabine, an oral nucleoside analog was studied for the treatment of RSV. The phase 1b and phase 2b studies reported here assessed the safety, pharmacokinetics, and pharmacodynamics of lumicitabine in infants/neonates hospitalized with RSV. In the phase 1b study, infants (≥1 to ≤12 months) and neonates (<28 days) received a single-ascending or multiple-ascending doses (single loading dose [LD] then 9 maintenance doses [MD] of lumicitabine, or placebo [3:1]). In the phase 2b study, infants/children (28 days to ≤36 months old) received lumicitabine 40/20 mg/kg, 60/40 mg/kg LD/MD twice-daily or placebo (1:1:1) for 5 days. Safety, pharmacokinetics, and efficacy parameters were assessed over 28 days. Lumicitabine was associated with a dose-related increase in the incidence and severity of reversible neutropenia. Plasma levels of ALS-008112, the active nucleoside analog, were dose-proportional with comparable mean exposure levels at the highest doses in both studies. There were no significant differences between the lumicitabine groups and placebo in reducing viral load, time to viral non-detectability, and symptom resolution. No emergent resistance-associated substitutions were observed at the RSV L-gene positions of interest. In summary, lumicitabine was associated with a dose-related increase in the incidence and severity of reversible neutropenia and failed to demonstrate antiviral activity in RSV-infected hospitalized infants. This contrasts with the findings of the previous RSV-A adult challenge study where significant antiviral activity was noted, without incidence of neutropenia. Trial registration ClinicalTrials.gov Identifier: NCT02202356 (phase 1b); NCT03333317 (phase 2b).