Sofosbuvir Suppresses the Genome Replication of DENV1 in Human Hepatic Huh7 Cells.

Dengue virus (DENV) causes dengue fever and dengue hemorrhagic fever, and DENV infection kills 20,000 people annually worldwide. Therefore, the development of anti-DENV drugs is urgently needed. Sofosbuvir (SOF) is an effective drug for HCV-related diseases, and its triphosphorylated metabolite inhibits viral RNA synthesis by the RNA-dependent RNA polymerase (RdRp) of HCV. (2'R)-2'-Deoxy-2'-fluoro-2'-methyluridine (FMeU) is the dephosphorylated metabolite produced from SOF. The effects of SOF and FMeU on DENV1 replication were analyzed using two DENV1 replicon-based methods that we previously established. First, a replicon-harboring cell assay showed that DENV1 replicon replication in human hepatic Huh7 cells was decreased by SOF but not by FMeU. Second, a transient replicon assay showed that DENV1 replicon replication in Huh7 cells was decreased by SOF; however, in hamster kidney BHK-21 cells, it was not suppressed by SOF. Additionally, the replicon replication in Huh7 and BHK-21 cells was not affected by FMeU. Moreover, we assessed the effects of SOF on infectious DENV1 production. SOF suppressed infectious DENV1 production in Huh7 cells but not in monkey kidney Vero cells. To examine the substrate recognition of the HCV and DENV1 RdRps, the complex conformation of SOF-containing DENV1 RdRp or HCV RdRp was predicted using AlphaFold 2. These results indicate that SOF may be used as a treatment for DENV1 infection.

Bemnifosbuvir (BEM, AT-527), a novel nucleotide analogue inhibitor of the hepatitis C virus NS5B polymerase.

INTRODUCTION: Chronic hepatitis C virus (HCV) persists as a public health concern worldwide. Consequently, optimizing HCV therapy remains an important objective. While current therapies are generally highly effective, advanced antiviral agents are needed to maximize cure rates with potentially shorter treatment durations in a broader patient population, particularly those patients with advanced diseases who remain difficult to treat. AREAS COVERED: This review summarizes the in vitro anti-HCV activity, preclinical pharmacological properties of bemnifosbuvir (BEM, AT-527), a novel prodrug that is metabolically converted to AT-9010, the active guanosine triphosphate analogue that potently and selectively inhibits several viral RNA polymerases, including the HCV NS5B polymerase. Results from clinical proof-of-concept and phase 2 combination studies are also discussed. EXPERT OPINION: BEM exhibits potent pan-genotype activity against HCV, and has favorable safety, and drug interaction profiles. BEM is approximately 10-fold more potent than sofosbuvir against HCV genotypes (GT) tested in vitro. When combined with a potent NS5A inhibitor, BEM is expected to be a promising once-daily oral antiviral for chronic HCV infection of all genotypes and fibrosis stages with potentially short treatment durations.

An algorithm for simplified hepatitis C virus treatment with non-specialist care based on nation-wide data from Taiwan.

BACKGROUND: Both European Association for the Study of the Liver (EASL) and American Association for the Study of Liver Diseases and the Infectious Diseases Society of America (AASLD-IDSA) guidelines recommend simplified hepatitis C virus (HCV) treatment with pan-genotypic sofosbuvir/velpatasvir or glecaprevir/pibrentasvir for eligible patients. This observational study used real-world data to assess these regimens' safety in eligible patients and develop an algorithm to identify patients suitable for simplified treatment by non-specialists. METHODS: 7,677 HCV-infected patients from Taiwan Hepatitis C Registry (TACR) who received at least one dose of sofosbuvir/velpatasvir or glecaprevir/pibrentasvir, and fulfilled the EASL/AASLD-IDSA criteria for simplified treatment were analyzed. Multivariate analysis was conducted on patient characteristics and safety data. RESULTS: Overall, 92.8% (7,128/7,677) of patients achieved sustained virological response and only 1.9% (146/7,677) experienced Grades 2-4 laboratory abnormalities in key liver function parameters (alanine aminotransferase, aspartate aminotransferase, and total bilirubin), with only 18 patients (0.23%) experiencing Grades 3-4 abnormalities. Age > 70 years old, presence of hepatocellular carcinoma, total bilirubin > 1.2 mg/dL, estimated glomerular filtration rate < 60 mL/min/1.73 m2, and Fibrosis-4 > 3.25 were associated with higher risks of Grades 2-4 abnormalities. Patients with any of these had an odds of 4.53 times than that of those without in developing Grades 2-4 abnormalities (p < 0.01). CONCLUSIONS: Real-world data from Taiwan confirmed that simplified HCV treatment for eligible patients with pan-genotypic regimens is effective and well tolerated. The TACR algorithm, developed based on this study's results, can further identify patients who can be safely managed by non-specialist care.

Identification and characterization of Sofosbuvir-resistant mutations of hepatitis C virus genotype 3a replicon.

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease worldwide. Among its 8 genotypes (GT), GT3 has a relatively lower sustained virological response to highly effective direct-acting antiviral agents (DAA). Sofosbuvir (SOF), an anti-NS5B polymerase inhibitor, is a core component of many anti-HCV DAA cocktail regimens, and its resistant mutations are rare in clinics because these mutations usually severely impair the NS5B polymerase activity, including a mutation S282T in NS5B, the most frequently reported SOF-resistant mutation. In this study, we selected SOF-resistant variants of a previously developed GT3 subgenomic replicon (PR87A7). Two mutations were identified in the viral genome of SOF-resistant PR87A7 variants, Q606R in nontargeted NS3 and S282T in targeted N5SB. We demonstrated that Q606R could rescue the replication defect of S282T in PR87A7, and the resulting double mutant confers the SOF resistance. Finally, we showed that NS3-606R could not compensate for the replication defect of S282T in other GTs. In conclusion, we identified a novel GT3-specific combination of two mutations that confers SOF resistance. Our result calls for attention to potential mutations that may arise in nontargeted viral proteins during the SOF-based DAA treatment of chronic HCV.

Novel sofosbuvir derivatives against SARS-CoV-2 RNA-dependent RNA polymerase: an in silico perspective.

The human coronavirus, SARS-CoV-2, had a negative impact on both the economy and human health, and the emerging resistant variants are an ongoing threat. One essential protein to target to prevent virus replication is the viral RNA-dependent RNA polymerase (RdRp). Sofosbuvir, a uridine nucleotide analog that potently inhibits viral polymerase, has been found to help treat SARS-CoV-2 patients. This work combines molecular docking and dynamics simulation (MDS) to test 14 sofosbuvir-based modifications against SARS-CoV-2 RdRp. The results reveal comparable (slightly better) average binding affinity of five modifications (compounds 3, 4, 11, 12, and 14) to the parent molecule, sofosbuvir. Compounds 3 and 4 show the best average binding affinities against SARS-CoV-2 RdRp (- 16.28 ± 5.69 and - 16.25 ± 5.78 kcal/mol average binding energy compared to - 16.20 ± 6.35 kcal/mol for sofosbuvir) calculated by Molecular Mechanics Generalized Born Surface Area (MM-GBSA) after MDS. The present study proposes compounds 3 and 4 as potential SARS-CoV-2 RdRp blockers, although this has yet to be proven experimentally.

Construction and characterization of a new hepatitis C virus genotype 6a subgenomic replicon that is prone to render the sofosbuvir resistance.

Hepatitis C virus (HCV) infection remains a challenge to human public health despite the development of highly effective direct-acting antivirals (DAAs). Sofosbuvir (SOF), a key component in most DAA-based anti-HCV cocktail regimens, is a potent viral RNA polymerase (NS5B) inhibitor with a high barrier to drug resistance. The serine-to-threonine mutation at NS5B 282 (S282T) confers the SOF resistance, but severely impairs viral replication in most HCV genotypes (GTs) and cannot be stably maintained after the termination of the SOF-based therapies. In this study, we first developed a new HCV GT-6a subgenomic replicon PR58D6. Next, we selected SOF-resistant PR58D6 variants by culturing the replicon cells in the presence of SOF. Interestingly, unlike many other HCV replicons which require additional mutations to compensate for the S282T-inducing fitness loss, S282T alone in PR58D6 is genetically stable and confers the SOF resistance without significantly impairing viral replication. Furthermore, we showed that amino acid residue at NS5B 74 (R74) and 556 (D556) which are conserved in GT 6a HCV contribute to efficient replication of PR58D6 containing S282T. Finally, we showed that the G556D mutation in NS5B could rescue the replication deficiency of the S282T in JFH1, a GT-2a replicon. In conclusion, we showed that a novel GT-6a HCV replicon may easily render SOF resistance, which may call for attention to potential drug resistance during DAA therapies of HCV GT-6a patients.

The Intergeneration Long-Lasting Consequences of Pre-Conceptional Exposure to Sofosbuvir on the Ovarian Tissues of F1 Offspring: Experimental Study on Rats.

Sofosbuvir (SOF), a nucleos(t)ide polymerase inhibitor, has been used during the past decade for mass treatment of viral hepatitis C in endemic countries like Egypt, increasing the exposure of women at childbearing age to SOF. This study investigated the long-lasting consequences of the pre-conceptional exposure of young female rats to SOF on the ovarian tissues of F1 offspring and explored the possible molecular mechanisms of these intergenerational effects at various levels. The study was conducted on young female rats that were divided into control group and SOF-exposed group at a dose of 4 mg/kg/day for three months. After that, pregnancy was induced in both groups by mating with healthy male rats. After delivery, the female neonates were followed for 4 months, and the ovarian tissues were collected to assess the studied parameters. Pre-conceptional exposure to SOF affected the ovarian functions of F1 offspring through modulation of estrogen receptors, ovarian Kiss1 and its receptor, increased lipid peroxidation marker, DNA oxidation marker, and redox-sensitive nuclear factor kappa B, and decreased nuclear erythroid-2-related factor 2, mitochondrial function, and biogenesis. SOF affected the ovarian function of the F1 offspring by inducing oxidative stress and inflammation, leading to the modulation of mitochondrial functions and biogenesis.

CD4/CD8 Ratio could be predictor of burden hepatocellular carcinoma in Egyptian chronic hepatitis C after combined sofosbuvir and daclatasvir therapy.

Background: During the first years of the use of direct acting Hepatitis C antiviral drugs (DAAS), several studies reported a possible correlation between this new era of treatment and an increased risk of Hepatocellular carcinoma (HCC). Its development could possibly be favored by the changes in the immunological milieu and the different cellular behavior after eradication of HCV infection with them. For this reason, this study aimed to address the immunological effect of DAAS. Subject & methods: Prospective paired -sample design, carried out on 90 naïve chronically infected HCV patients before and after receiving a combination therapy of sofosbuvir; at a dose of 400 mg once daily and daclatasvir; at a dose of 60 mg once daily for 12 weeks and follow up for one year. immunological tests including: total T cell count, T helper cell count, T cytotoxic cell count and natural killer cell count in peripheral blood through (CD3, CD3/CD4, CD3/CD8 and CD56 respectively) by Fluorochrome monoclonal antibodies labelled with specific dyes through Multiparameter, FACSCanto ™ II flow cytometer (Becton Dickinson, USA). Result: Concerning the immunological changes, total T cells (CD3+), Natural killer cells showed non-significant decrease at end of therapy while significant decrease in T helper cells (CD3+CD4+) T cytotoxic cells (CD3+CD8+) compared to pre-treatment value. Long follow up revealed 26.6% developed focal HCC, in more addition, multivariate analysis show CD4/CD8 ratio could be predictor as well as sex for early development of HCC after combined DAAS therapy. Conclusion: HCV treatment by DAAS produces significant decrease in T helper, T cytotoxic cells in CHC patients at the end of therapy. 26.6% developed focal HCC with independent CD4/CD8 predictor for burden malignancy. Further large extended population study is needed for clarify this concern.

An insight into the hepatoprotective role of Velpatasvir and Sofosbuvir per se and in combination against carbon tetrachloride-induced hepatic fibrosis in rats.

Hepatitis C is a global health issue. Hepatitis C Virus (HCV) induces fibrosis by redox reactions, which involve the deposition of collagen in extracellular matrix (ECM). This study aimed to examine the antifibrotic effect of direct-acting antivirals; Sofosbuvir and Velpatasvir, per se and in combination against carbon tetrachloride (CCl4)-induced fibrosis in rats. Carbon tetrachloride (intraperitoneal; 0.5 ml/kg) twice weekly for six weeks was used to induce hepatic fibrosis in rats. After two weeks of CCl4, oral administration of Sofosbuvir (20 mg/kg/d) and Velpatasvir (10 mg/kg/d) was administered to rats for the last four weeks. Liver function tests (LFTs), renal function tests (RFTs), oxidative stress markers, and the levels of TNF-a, NF-κB, and IL-6 were measured through ELISA and western blotting at the end of the study. CCl4 significantly ameliorated the values of RFTs, LFTs and lipid profiles in the diseased group, which were normalized by the SOF and VEL both alone and in combination. These drugs produced potent antioxidant effects by significantly increasing antioxidant enzymes. From the histopathology of hepatic tissues of rats treated with drugs, the antifibrotic effect was further manifested, which showed suppression of hepatic stellate cells (HSCs) in treated rats, as compared to the disease control group. The antifibrotic effect was further demonstrated by significantly decreasing the levels of TNF-a, NF-κB and IL-6 in serum and hepatic tissues of treated rats as compared to the disease control group. Sofosbuvir and Velpatasvir alone and in combination showed marked inhibition of fibrosis in the CCl4-induced non-HCV rat model, which was mediated by decreased levels of TNF-a/NF-κB and the IL-6 signaling pathway. Thus, it can be concluded that Sofosbuvir and Velpatasvir might have an antifibrotic effect that appears to be independent of their antiviral activity.

The pre-conception maternal exposure to Sofosbuvir affects the mitochondrial biogenesis in prenatal fetal tissues: Experimental study on rats.

BACKGROUND: Hepatitis C virus (HCV) infection is a global public health problem and Egypt has the highest HCV prevalence worldwide. Hence, global efforts target to eliminate HCV by 2030. Sofosbuvir is a nucleotide analogue inhibitor of HCV polymerase essential for viral replication. Animal studies prove that Sofosbuvir metabolites cross the placenta and are excreted in the milk of nursing animals. We aimed to investigate the possible effects of preconception maternal exposure to Sofosbuvir on mitochondrial biogenesis in prenatal fetal liver, skeletal muscle, and placental tissues. METHODS: The study was conducted on 20 female albino rats divided into a control group receiving a placebo and an exposed group receiving 4 mg/kg orally/day for 3 months of Sofosbuvir. At the end of the treatment period, pregnancy was induced in both groups by mating with healthy male rats overnight. At gestational day 17, all pregnant female rats were sacrificed. Each fetus was dissected to obtain the fetal liver, skeletal muscle, and placental tissues. RESULTS: The results of our study indicated that the exposure of young female rats to Sofosbuvir affects pregnancy outcomes. Fetal liver and muscle showed lower mitochondrial DNA-copy number (mtDNA-CN) by about 24% and 29% respectively, peroxisome proliferator-activated receptor-gamma coactivator-1 alpha and its downstream targets; nuclear respiratory factor-1 and mitochondrial transcription factor A. While the placental tissues showed different patterns, particularly elevated in mtDNA-CN by about 43%. CONCLUSIONS: The study provides preliminary evidence of the detrimental effects of Sofosbuvir on the pregnancy outcomes of the exposed females and may impair the placental and fetal organs' development. These effects may be mediated through modulating mitochondrial homeostasis and functions.

Fitness-Dependent, Mild Mutagenic Activity of Sofosbuvir for Hepatitis C Virus.

The concept of a mild mutagen was coined to describe a minor mutagenic activity exhibited by some nucleoside analogues that potentiated their efficacy as antiretroviral agents. In the present study, we report the mild mutagen activity of sofosbuvir (SOF) for hepatitis C virus (HCV). Serial passages of HCV in human hepatoma cells, in the presence of SOF at a concentration well below its cytotoxic concentration 50 (CC50) led to pre-extinction populations whose mutant spectra exhibited a significant increase of C→U transitions, relative to populations passaged in the absence of SOF. This was reflected in an increase in several diversity indices that were used to characterize viral quasispecies. The mild mutagenic activity of SOF was largely absent when it was tested with isogenic HCV populations that displayed high replicative fitness. Thus, SOF can act as a mild mutagen for HCV, depending on HCV fitness. Possible mechanisms by which the SOF mutagenic activity may contribute to its antiviral efficacy are discussed.

Emergence of resistance-associated variants during sofosbuvir treatment in chronically infected hepatitis E patients.

BACKGROUND AND AIMS: Chronic HEV infections remain a serious problem in immunocompromised patients, as specifically approved antiviral drugs are unavailable. In 2020, a 24-week multicenter phase II pilot trial was carried out, evaluating the nucleotide analog sofosbuvir by treating nine chronically HEV-infected patients with sofosbuvir (Trial Number NCT03282474). During the study, antiviral therapy reduced virus RNA levels initially but did not lead to a sustained virologic response. Here, we characterize the changes in HEV intrahost populations during sofosbuvir treatment to identify the emergence of treatment-associated variants. APPROACH AND RESULTS: We performed high-throughput sequencing on RNA-dependent RNA polymerase sequences to characterize viral population dynamics in study participants. Subsequently, we used an HEV-based reporter replicon system to investigate sofosbuvir sensitivity in high-frequency variants. Most patients had heterogenous HEV populations, suggesting high adaptability to treatment-related selection pressures. We identified numerous amino acid alterations emerging during treatment and found that the EC 50 of patient-derived replicon constructs was up to ~12-fold higher than the wild-type control, suggesting that variants associated with lower drug sensitivity were selected during sofosbuvir treatment. In particular, a single amino acid substitution (A1343V) in the finger domain of ORF1 could reduce susceptibility to sofosbuvir significantly in 8 of 9 patients. CONCLUSIONS: In conclusion, viral population dynamics played a critical role during antiviral treatment. High population diversity during sofosbuvir treatment led to the selection of variants (especially A1343V) with lower sensitivity to the drug, uncovering a novel mechanism of resistance-associated variants during sofosbuvir treatment.

Differential activity of nucleotide analogs against tick-borne encephalitis and yellow fever viruses in human cell lines.

With no approved antiviral therapies, the continuous emergence and re-emergence of tick-borne encephalitis virus (TBEV) and yellow fever virus (YFV) is a rising concern. We performed head-to-head comparisons of the antiviral activity of available nucleos(t)ide analogs (nucs) using relevant human cell lines. Eight existing nucs inhibited TBEV and/or YFV with differential activity between cell lines and viruses. Remdesivir, uprifosbuvir and sofosbuvir were the most potent drugs against TBEV and YFV in liver cells, but they had reduced activity in neural cells, whereas galidesivir retained uniform activity across cell lines and viruses. Ribavirin, valopicitabine, molnupiravir and GS-6620 exhibited only moderate antiviral activity. We found antiviral activity for drugs previously reported as inactive, demonstrating the importance of using human cell lines and comparative experimental assays when screening the activity of nucs. The relatively high antiviral activity of remdesivir, sofosbuvir and uprifosbuvir against TBEV and YFV merits further investigation in clinical studies.

Characterization of multi-DAA resistance using a novel hepatitis C virus genotype 3a infectious culture system.

BACKGROUND AND AIMS: The high HCV infection cure rates achieved with direct-acting antiviral (DAA) treatments could be compromised in the future by the emergence of antiviral resistance. Thus, it is essential to understand the viral determinants that influence DAA resistance, which is most prevalent in genotype 3. We aimed at studying how resistance to protease-, NS5A-, and NS5B-inhibitors influences the activities of glecaprevir/pibrentasvir, sofosbuvir/velpatasvir, and sofosbuvir/velpatasvir/voxilaprevir in cell culture, and how the HCV genome adapts to selective pressure by successive rounds of treatment failure. APPROACH AND RESULTS: A previously developed in vivo infectious cDNA clone of strain S52 (genotype 3a) was adapted to efficiently replicate and propagate in human hepatoma cells (Huh7.5) using 31 adaptive substitutions. DAA escape experiments resulted in the selection of S52 variants with decreased drug susceptibility (resistance), which was linked to the emergence of known resistance-associated substitutions (RASs). NS5A-inhibitor resistance was sufficient to promote treatment failure with double-DAA but not triple-DAA regimens. Enhanced viral fitness associated with the selection of sofosbuvir resistance accelerated escape from DAAs. After serial DAA treatment failure, HCV genetic evolution led to a complex genome-wide network of substitutions, some of which coevolved with known RASs. CONCLUSIONS: Baseline NS5A-RAS can compromise the efficacy of double-DAA pangenotypic regimens for HCV genotype 3, and enhanced viral fitness can accelerate treatment failure. Persistence of RASs after successive treatment failure is facilitated by the remarkable evolutionary capacity and plasticity of the HCV genome. Proof-of-concept for the potential development of multi-DAA resistance is shown.

Antiviral Treatment Failures After Transplantation of Organs From Donors With Hepatitis C Infection: A Report of 4 Cases.

The transplantation of organs from donors with hepatitis C virus (HCV) infection into uninfected recipients has expanded the available organ donor pool. With the advancement of direct-acting antivirals (DAAs), high rates of cure among transplant recipients are possible. Although DAAs are highly effective, treatment failure can occur following an appropriate 12-week course of a pan-genotypic regimen. Here we describe 4 kidney transplant recipients of organs from donors with HCV infection (3 with genotype 3, 1 genotype 1a) in whom first-line DAA treatment with either glecaprevir-pibrentasvir or sofosbuvir-velpatasvir was unsuccessful, started 22-35 days after the day of transplantation. All ultimately achieved sustained virologic response with second- or third-line therapy. Post-treatment resistance-associated substitutions were tested and noted to be present in 2 cases. Additionally, antiviral levels were assessed in 2 cases and found to be therapeutic in each. This article explores possible reasons for treatment failure, including medication interactions, bariatric surgery, viral dynamics, and drug resistance.

Saffron extract attenuates Sofosbuvir-induced retinal neurodegeneration in albino rat.

Sofosbuvir is a novel drug candidate for the treatment of hepatitis C viral infection; however, vision loss is one of its growing adverse effects. Saffron is a natural biomolecule with a high antioxidant potential that has been efficiently used in some diseases caused by oxidative stress. This study evaluated Sofosbuvir's neurodegenerative effect on the retina of albino rat and examined the potential protective role of saffron aqueous extract. Twenty-one adult male albino rats were randomly divided into three groups: Control, Sofosbuvir-treated (41.1 mg/kg /day for 6 weeks), and Sofosbuvir + Saffron co-treated groups. Retinal specimens were biochemically analyzed for malondialdehyde (MDA), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) levels. In addition, light and transmission electron microscopic examination, as well as immunohistochemical staining for Caspase-3, COX-2, and GFAP were performed. Sofosbuvir treatment caused a significant increase in retinal MDA, IL-6, and TNF-α levels coupling with a significant decrease in retinal total antioxidant capacity level. Histopathological findings revealed disturbed retinal architecture, detached pigment epithelium, vacuolated photoreceptors, in addition to a significant decrease in the thicknesses of both outer and inner nuclear layers, and the number of ganglionic cells. Ultrastructural examination revealed extensive degenerative changes in all retinal layers. Caspase-3, COX-2, and GFAP immunohistochemical expressions were significantly increased. Meanwhile, concomitant treatment with Saffron significantly improved retinal redox status, inflammation, histological, and ultrastructural parameters. Saffron may protect the retina from the hazardous effects of Sofosbuvir. Saffron could be used as an adjuvant therapy to protect patients receiving Sofosbuvir from retinal damage.

Treatment of hepatitis C in children and adolescents: how far have we reached?

BACKGROUND: Hepatitis C virus (HCV) infection is a global public health problem and also generates a significant case load in children and adolescents. With the introduction of directly acting antivirals (DAA), the treatment and care of HCV-infected patients have progressed significantly. The available treatment options in children are limited, and this review aims to provide an overview of treatment of HCV infection in children and adolescents with the current available DAA regimens. DATA SOURCES: This comprehensive review was undertaken after searching the PubMed/Medline and Embase databases for the available up-to-date literature on pediatric HCV infection and treatment using hepatitis C virus infection/HCV, directly acting antivirals/DAA, natural history, treatment, pediatrics, children, and adolescents as keywords. RESULTS: Combination therapies with highly effective DAA regimes, such as sofosbuvir/ledipasvir, sofosbuvir/velpatasvir, glecaprevir/pibrentasvir, sofosbuvir/daclatasvir, sofosbuvir/ribavirin and others, are available for use in children. Most of the DAA regimens have either received or are pending to receive regulatory approval by different medical/drug agencies for use in children and adolescents. Pan-genotypic regimens are also available in children and adolescents, and these regimens can be used while skipping genotype testing. CONCLUSION: The literature on different DAA regimens for use in children shows that these regimens have higher cure rates with minimal side effects and shorter duration of therapy.

Sofosbuvir and its tri-phosphate metabolite inhibit the RNA-dependent RNA polymerase activity of non-structural protein 5 from the Kyasanur forest disease virus.

Kyasanur forest disease is a neglected zoonotic disease caused by a single-stranded RNA-based flavivirus, the incidence of which was first recorded in 1957 in the Southern part of India. Kyasanur forest disease virus is transmitted to monkeys and humans through the infected tick bite of Haemophysalis spinigera. Kyasanur forest disease is a febrile illness, which in severe cases, results in neurological complications leading to mortality. The current treatment regimens are symptomatic and supportive, and no targeted therapies are available for this disease. In this study, we evaluated the ability of FDA-approved drugs sofosbuvir (and its active metabolite) and Dasabuvir to inhibit the RNA-dependent RNA polymerase activity of NS5 protein from the Kyasanur forest disease virus. NS5 protein containing the N-terminal methyl transferase domain and C-terminal RNA-dependent RNA polymerase domain was expressed in Escherichia coli, and RNA-dependent RNA polymerase activity was demonstrated with the purified protein. The RNA-dependent RNA polymerase assay conditions were optimized, followed by the determination of apparent Km,ATP to validate the enzyme preparation. Half maximal-inhibitory concentrations against RNA-dependent RNA polymerase activity were determined for Sofosbuvir and its active metabolite. Dasabuvir did not show detectable inhibition with the tested conditions. This is the first demonstration of the inhibition of RNA-dependent RNA polymerase activity of NS5 protein from the Kyasanur forest disease virus with small molecule inhibitors. These initial findings can potentially facilitate the discovery and development of targeted therapies for treating Kyasanur forest disease.

Daclatasvir as a hepatitis C infection treatment option: an up-to-date evaluation.

INTRODUCTION: Globally, it is estimated that 290,000 patients infected with hepatitis C virus (HCV) died from hepatitis C consequences, including cirrhosis and hepatocellular carcinoma in 2019. Although daclatasvir (DCV), combined with sofosbuvir (SOF), is effective in HCV patients, the new pan-genotypic combinations are considered by many as more cost-effective and successful in eradicating HCV infection. AREAS COVERED: This review discusses the safety, efficacy, and cost-effectiveness of DCV as an HCV treatment option based on real-world studies and pharmacoeconomic evaluations. EXPERT OPINION: Real-life studies suggest that SOF/DCV has acceptable sustained virological response and can be used successfully to manage HCV. Nonetheless, the use of SOF/DCV is limited by the longer treatment duration in genotype (GT)-3 patients and the need for ribavirin (RBV) in treatment-experienced patients which increases the likelihood of adverse effects. DCV is likely to remain as a therapeutic option for the management of GT-1, GT-2, and GT-4 patients in resource limited settings, while GT-3 patients are more likely to benefit from RBV-free direct-acting antiviral combinations such as SOF/velpatasvir for 12 weeks or glecaprevir/pibrentasvir for 8 weeks. The introduction of generics for these new pan-genotypic drugs would likely eliminate the need for SOF/DCV in the near future.

Discovery of SARS-CoV-2 antiviral synergy between remdesivir and approved drugs in human lung cells.

SARS coronavirus 2 (SARS-CoV-2) has caused an ongoing global pandemic with significant mortality and morbidity. At this time, the only FDA-approved therapeutic for COVID-19 is remdesivir, a broad-spectrum antiviral nucleoside analog. Efficacy is only moderate, and improved treatment strategies are urgently needed. To accomplish this goal, we devised a strategy to identify compounds that act synergistically with remdesivir in preventing SARS-CoV-2 replication. We conducted combinatorial high-throughput screening in the presence of submaximal remdesivir concentrations, using a human lung epithelial cell line infected with a clinical isolate of SARS-CoV-2. This identified 20 approved drugs that act synergistically with remdesivir, many with favorable pharmacokinetic and safety profiles. Strongest effects were observed with established antivirals, Hepatitis C virus nonstructural protein 5A (HCV NS5A) inhibitors velpatasvir and elbasvir. Combination with their partner drugs sofosbuvir and grazoprevir further increased efficacy, increasing remdesivir's apparent potency > 25-fold. We report that HCV NS5A inhibitors act on the SARS-CoV-2 exonuclease proofreader, providing a possible explanation for the synergy observed with nucleoside analog remdesivir. FDA-approved Hepatitis C therapeutics Epclusa® (velpatasvir/sofosbuvir) and Zepatier® (elbasvir/grazoprevir) could be further optimized to achieve potency and pharmacokinetic properties that support clinical evaluation in combination with remdesivir.