Virus Nonstructural Protein 5A Research Articles

Classical swine fever virus non-structural protein 4A recruits dihydroorotate dehydrogenase to facilitate viral replication.

Classical swine fever remains one of the most economically important viral diseases of domestic pigs and wild boar worldwide. dihydroorotate dehydrogenase (DHODH) inhibitors have been shown to suppress the replication of several viruses in vitro and in vivo, but the effects on Pestivirus remain unknown. In this study, three specific DHODH inhibitors, including DHODH-IN-16, BAY-2402234, and Brequinar were found to strongly suppress classical swine fever virus (CSFV) replication. These inhibitors target the host DHODH, depleting the pyrimidine nucleotide pool to exert their antiviral effects. Intriguingly, we observed that the non-structural protein 4A of CSFV induced DHODH to accumulate around the nucleus in conjunction with mitochondria. Moreover, NS4A exhibited a strong interaction with DHODH, enhancing its activity to promote efficient CSFV replication. In conclusion, our findings enhance the understanding of the pyrimidine synthesis in CSFV infection and expand the novel functions of CSFV NS4A in viral replication, providing a reference for further exploration of antiviral targets against CSFV.

Ser235 phosphorylation of hepatitis C virus NS5A is required for NS5A dimerization and drug resistance

Hepatitis C virus (HCV) infection is recognized as a major causative agent of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. HCV non-structural protein 5A (NS5A) is a dimeric phosphoprotein with a hyperphosphorylated form to act as a switch that regulates HCV replication and assembly. NS5A inhibitors have been utilized as the scaffold for combination therapy of direct-acting antiviral agents (DAA). However, the mode of action of NS5A inhibitors is still unclear due to the lack of mechanistic detail regarding NS5A phosphorylation and dimerization in the HCV life cycle. It has been demonstrated that phosphorylation of NS5A at Ser235 is essential for RNA replication of the JFH1 strain. In this report, we found that NS5A phosphomimetic Ser235 substitution (Ser-to-Asp mutation) formed a dimer that was resistant to disruption by NS5A inhibitors as was the NS5A resistance-associated substitution Y93H. Phosphorylation of NS5A at Ser235 residue was required for the interaction of two NS5A-WT molecules in JFH1-based cell culture system but not absolutely required for dimerization of the NS5A-Y93H mutant. Interestingly, HCV nonstructural proteins from the subgenomic replicon NS3-5A was required for NS5A-WT dimerization but not required for NS5A-Y93H dimerization. Our data suggest that spontaneous Ser235 phosphorylation of NS5A and ensuing dimerization account for resistance of the JFH1/NS5A-Y93H mutant to NS5A inhibitors.

ASPP2 binds to hepatitis C virus NS5A protein via an SH3 domain/PxxP motif-mediated interaction and potentiates infection.

Hepatitis C virus (HCV) infects millions of people worldwide and is a leading cause of liver disease. Despite recent advances in antiviral therapies, viral resistance can limit drug efficacy and understanding the mechanisms that confer viral escape is important. We employ an unbiased interactome analysis to discover host binding partners of the HCV non-structural protein 5A (NS5A), a key player in viral replication and assembly. We identify ASPP2, apoptosis-stimulating protein of p53, as a new host co-factor that binds NS5A via its SH3 domain. Importantly, silencing ASPP2 reduces viral replication and spread. Our study uncovers a previously unknown role for ASPP2 to potentiate HCV RNA replication.

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.

Hepatitis C Virus Nonstructural Protein 5A Interacts with Immunomodulatory Kinase IKKε to Negatively Regulate Innate Antiviral Immunity.

Hepatitis C virus (HCV) infection can lead to chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. HCV employs diverse strategies to evade host antiviral innate immune responses to mediate a persistent infection. In the present study, we show that nonstructural protein 5A (NS5A) interacts with an NF-κB inhibitor immunomodulatory kinase, IKKε, and subsequently downregulats beta interferon (IFN-β) promoter activity. We further demonstrate that NS5A inhibits DDX3-mediated IKKε and interferon regulatory factor 3 (IRF3) phosphorylation. We also note that hyperphosphorylation of NS5A mediats protein interplay between NS5A and IKKε, thereby contributing to NS5A-mediated modulation of IFN-β signaling. Lastly, NS5A inhibits IKKε-dependent p65 phosphorylation and NF-κB activation. Based on these findings, we propose NS5A as a novel regulator of IFN signaling events, specifically by inhibiting IKKε downstream signaling cascades through its interaction with IKKε. Taken together, these data suggest an additional mechanistic means by which HCV modulates host antiviral innate immune responses to promote persistent viral infection.

Mitophagy induced by classical swine fever virus nonstructural protein 5A promotes viral replication

The classical swine fever virus (CSFV) is one of the most harmful pathogens of swine and causes considerable economic loss. Mitophagy is a selective form of autophagy that degrades damaged mitochondria by combining with lysosomes. Previous studies have been reported that CSFV infection can induce mitophagy, but which effector protein is responsible for this process remains unclear. Herein, we revealed here that the CSFV nonstructural protein 5A (NS5A) plays a critical role in inducing cellular mitophagy. Specifically, the expression of CSFV NS5A in the PK-15 cells induces membrane potential loss and mitochondrial fission, and the quantities of mitophagosomes, the expression of Parkin and PINK1 were significantly increased compared with mock cells. Intriguingly, we found that Parkin-overexpression promotes CSFV propagation. Furthermore, the expression level of reactive oxygen species (ROS) was increased by CSFV NS5A protein, while NS5A-induced mitophagy correlated with the quantity of ROS production. In summary, our results reveal a new function of NS5A in inducing cellular mitophagy and broaden our understanding of the mechanism of CSFV-induced mitophagy, which may provide a new way to develop an antiviral strategy.

A simple and sensitive HPLC-FL method for bioanalysis of velpatasvir, a novel hepatitis C virus NS5A inhibitor, in rat plasma: Investigation of factors determining its oral bioavailability

Velpatasvir is a novel inhibitor of hepatitis C virus nonstructural protein 5A that received US Food and Drug Administration approval for the treatment of patients with chronic hepatitis C virus genotypes 1–6. In the present study, a sensitive bioanalytical method for velpatasvir was developed using high-performance liquid chromatography coupled with a fluorescence detector system, which was applied to elucidate the factors determining the oral bioavailability and disposition of velpatasvir. This method offered sufficient sensitivity, with a lower limit of quantification of 0.5 ng/mL, which is comparable to previously reported methods using liquid chromatography coupled with tandem mass spectrometry. Velpatasvir exhibited low oral bioavailability, moderate intestinal permeability, and significant biliary excretion in rats. It was also found to be significantly metabolized in the liver, with a low-to-moderate extraction ratio; however, its intestinal metabolism and enterohepatic circulation did not occur. Thus, our present results demonstrate that the oral bioavailability of velpatasvir is primarily dependent on gut absorption and hepatic first-pass metabolism. The fractions of velpatasvir dose unabsorbed from the gut and eliminated by the liver before reaching the systemic circulation following oral administration were estimated to be 32.8%–58.6% and 4.74%–30.54% of the oral dose, respectively. To our knowledge, this is the first systematic study to investigate the contributory roles of biopharmaceutical and pharmacokinetic factors on the oral bioavailability of velpatasvir, together with a new bioanalytical method for velpatasvir.

Japanese Encephalitis Virus NS4A Protein Interacts with PTEN-Induced Kinase 1 (PINK1) and Promotes Mitophagy in Infected Cells.

ABSTRACTThe nonstructural protein 4A (NS4A) of flaviviruses has been implicated as a “central organizer” of the membrane-bound replication complex during virus replication. However, its role in the host responses to virus infection is not understood. Using the yeast-two-hybrid library screen, we identified a multitude of host proteins interacting with the Japanese encephalitis virus (JEV) NS4A protein. Several of these interacting proteins are known to localize to the mitochondria. One of these proteins was PTEN-induced kinase 1 (PINK1), a serine/threonine-protein kinase known for its role in mitophagy. Here, we demonstrate the JEV-NS4A localization to the mitochondria and its interaction with PINK1 in Huh7 cells during JEV infection. The JEV-infected cells showed an enhanced mitophagy flux with a concomitant decline in the mitochondrial mass. We present data showing that JEV-NS4A alone was sufficient to induce mitophagy. Interference with mitochondrial fragmentation and mitophagy resulted in reduced virus propagation. Overall, our study provides the first evidence of mitochondrial quality control dysregulation during JEV infection, largely mediated by its NS4A protein.IMPORTANCE The JEV-infected mammalian cells show an enhanced mitophagy flux with a concomitant decline in the mitochondrial mass. We show that the NS4A protein of JEV localized to the mitochondria and interacted with PINK1 in Huh7 cells during infection with the virus and demonstrate that JEV-NS4A alone is sufficient to induce mitophagy. The study provides the first evidence of mitochondrial quality control dysregulation during JEV infection, largely mediated by its NS4A protein.

Protein tyrosine kinase Abl promotes hepatitis C virus particle assembly via interaction with viral substrate activator NS5A

Previously, we reported that knockdown of Abl protein tyrosine kinase by shRNA or pharmacological inhibition suppresses particle assembly of J6/JFH1 strain–derived hepatitis C virus (HCV) in Huh-7.5 cells. However, the detailed mechanism by which Abl regulates HCV replication remained unclear. In this study, we established Abl-deficient (Abl−) cells through genome editing and compared HCV production between Abl− cells expressing WT or kinase-dead Abl and parental Huh-7.5 cells. Our findings revealed that Abl expression was not required from the stages of virus attachment and entry to viral gene expression; however, the kinase activity of Abl was necessary for the assembly of HCV particles. Reconstitution experiments using human embryonic kidney 293T cells revealed that phosphorylation of Tyr412 in the activation loop of Abl was enhanced by coexpression with the viral nonstructural protein 5A (NS5A) and was abrogated by the substitution of NS5A Tyr330 with Phe (Y330F), suggesting that NS5A functions as a substrate activator of Abl. Abl–NS5A association was also attenuated by the Y330F mutation of NS5A or the kinase-dead Abl, and Abl Tyr412 phosphorylation was not enhanced by NS5A bearing a mutation disabling homodimerization, although the association of Abl with NS5A was still observed. Taken together, these results demonstrate that Abl forms a phosphorylation-dependent complex with dimeric NS5A necessary for viral particle assembly, but that Abl is capable of complex formation with monomeric NS5A regardless of tyrosine phosphorylation. Our findings provide the foundation of a molecular basis for a new hepatitis C treatment strategy using Abl inhibitors.

Mitophagy Induced by Classical Swine Fever Virus Nonstructural Protein 5A Promotes Viral Replication

Mitophagy Induced by Classical Swine Fever Virus Nonstructural Protein 5A Promotes Viral Replication

Hepatitis C Virus Nonstructural 5A Protein Interacts with Telomere Length Regulation Protein: Implications for Telomere Shortening in Patients Infected with HCV.

Hepatitis C virus (HCV) is a major cause of chronic liver disease and is highly dependent on cellular proteins for viral propagation. Using protein microarray analysis, we identified 90 cellular proteins as HCV nonstructural 5A (NS5A) interacting partners, and selected telomere length regulation protein (TEN1) for further study. TEN1 forms a heterotrimeric complex with CTC and STN1, which is essential for telomere protection and maintenance. Telomere length decreases in patients with active HCV, chronic liver disease, and hepatocellular carcinoma. However, the molecular mechanism of telomere length shortening in HCV-associated disease is largely unknown. In the present study, protein interactions between NS5A and TEN1 were confirmed by immunoprecipitation assays. Silencing of TEN1 reduced both viral RNA and protein expression levels of HCV, while ectopic expression of the siRNA-resistant TEN1 recovered the viral protein level, suggesting that TEN1 was specifically required for HCV propagation. Importantly, we found that TEN1 is re-localized from the nucleus to the cytoplasm in HCV-infected cells. These data suggest that HCV exploits TEN1 to promote viral propagation and that telomere protection is compromised in HCV-infected cells. Overall, our findings provide mechanistic insight into the telomere shortening in HCV-infected cells.

Autophagy Induced by the N-Terminus of the Classic Swine Fever Virus Nonstructural Protein 5A Protein Promotes Viral Replication.

Although classic swine fever virus (CSFV) infection has been reported to induce autophagy, the specific induced mechanism remains unrevealed. Nonstructural protein 5A (NS5A) of CSFV is a multiphosphorylated protein with multiple functions to regulate viral replication and the host cell immune responses. Herein, we demonstrated that CSFV NS5A could induce cellular autophagy and promote viral replication. In the current study, we showed that NS5A expression significantly increased the levels of autophagy-related genes (ATGs), including light chain 3 (LC3), ATG5, and Beclin 1; conversely, degradation of P62/sequestosome 1 (SQSTM1) was observed by Western blotting. The number of autophagy-like vesicles was also obviously increased in NS5A-expressing cells, as analyzed by transmission electron microscopy (TEM). Furthermore, we observed the co-localization of the NS5A and LC3 proteins by confocal immunofluorescence analysis. Direct binding of NS5A to the autophagy-related LC3 protein was confirmed by coimmunoprecipitation in vivo and by a GST pulldown assay in vitro. Through segmentation and point mutation research on the NS5A protein, we found that the N-terminal region and the phosphorylation of amino acids 81 and 92 of the NS5A protein were essential for inducing autophagy. Finally, we demonstrated that the LC3 protein had a positive effect on CSFV replication. These findings emphasize a previously unascertained interaction relationship between NS5A and LC3 in the autophagy process. Furthermore, our research revealed a new role of CSFV NS5A, particularly its N-terminal amino acids serine 81 and serine 92, as a critical regulator of CSFV-induced autophagy and have significance for extending our understanding of the CSFV-autophagy interplay.

Development of a Synthesis Process for a Novel HCV NS5A Inhibitor, Emitasvir

A new approach to the synthesis of Emitasvir (DAG181), a small molecule hepatitis C virus (HCV) nonstructural protein 5A (NS5A) inhibitor, is described. Enantioselective enzymatic desymmetrization ...

Association between interleukin 28B polymorphism and sustained virological response to sofosbuvir plus daclatasvir in chronic hepatitis C genotype 4 Egyptian patients

Sofosbuvir has been approved as the first nonstructural protein 5Bpolymerase inhibitor with pan-genotypic activity against the hepatitis C (HCV) virus. Daclatasvir is a first-in-class hepatitis C virus nonstructural protein 5A replication complex inhibitor. We aimed to evaluate the usefulness of the reference single nucleotide polymorphism (rs12979860) interleukin 28B (CC genotype) for predicting sustained virological response to sofosbuvir plus daclatasvir in Egyptian patients infected with HCV-4. Samples were collected at week zero. One hundred and thirty-one patients who reached the end of treatment (at week 12) were divided into three groups, according to their interleukin 28B genotype: Group A included 31 patients (CC genotype), group B included 79 patients (CT genotype) and group C had 21 patients (TT genotype). All patients received treatment for 3months in the form of sofosbuvir plus daclatasvir with ribavirin (in case of cirrhotic patients) or without ribavirin (in case of non-cirrhotic patients). Sustained virological response rate was significantly higher in patients with IL28B (CC genotype) vs. (non-CC genotype) (100 vs.88%) (p<0.0001).These patients also showed lower rates of post-treatment relapse and non-response, compared with the CT and TT patients (0% vs. (7.59% and 28.5%, respectively) (p<0.0001). Also, patients with CC genotype showed higher sustained virological response than non-CC genotypes on both cirrhotic (100% vs. 68.75%) and non-cirrhotic patients (100% vs. 91.66%) (p≤0.0001). Our results suggest that IL28B genotype contributes to the prediction of response to sofosbuvir plus daclatasvir.

Berberis lyceum and Fumaria indica: in vitro cytotoxicity, antioxidant activity, and in silico screening of their selected phytochemicals as novel hepatitis C virus nonstructural protein 5A inhibitors

Berberis lyceum and Fumaria indica are two Pakistani indigenous herbal medicines used to treat liver infections, including hepatitis C virus (HCV). This study aimed to evaluate the cytotoxicity, and antioxidant activity of these plant extracts and computationally screen their selected phytoconstituents as HCV NS5A inhibitors. The viability of HepG2 cells was assessed 24 h and 48 h post-treatment using colorimetric and dye exclusion methods. Antioxidant properties were examined by the 2,2-diphenyl-1-picrylhydrazyl (DPPH), reducing power, and total antioxidant capacity assays. Seventeen known phytochemicals identified from each plant were docked into the active binding site of HCV NS5A protein. The top hit ligands were analyzed for their druglikeness properties and the indices of absorption, distribution, metabolism, elimination, and toxicity (ADMET). The results showed that both plant extracts were non-toxic (CC50 > 200 µg/ml). The IC50 values of DPPH-radical scavenging activity were 51.02 ± 0.94 and 62.91 ± 1.85 µg/ml for B. lyceum and F. indica, respectively. They also exhibited reducing power and total antioxidant capacity.The phytochemicals were identified as potent HCV NS5A inhibitors with good druglikeness and ADMET properties. Six of the docked phytochemicals exhibited higher binding scores (-17.9 to −19.2 kcal/mol) with HCV NS5A protein than the standard drug, daclatasvir (-17.2 kcal/mol). Molecular dynamics (MD) simulation confirmed the stability of two compounds, berbamine and paprafumine at 100 ns with active site of HCV NS5A protein. The identified compounds through molecular docking and MD simulation could have potential as HCV NS5A inhibitor after further validation. Communicated by Ramaswamy H. Sarma

Phytochemical analysis of Berberis lyceum methanolic extract and its antiviral activity through the restoration of MAPK signaling pathway modulated by HCV NS5A

Objective: To evaluate the antiviral activity and phytochemicals of selected plant extracts and their effect on the mitogen-activated protein kinase (MAPK) signaling pathway modulated by hepatitis C virus (HCV) nonstructural protein 5A (NS5A). Methods: A total of ten plant extracts were initially screened for their toxicities against HepG2 cells. The non-toxic plants were tested for their inhibitory effect on the expression of HCV NS5A at both mRNA and protein levels using real-time PCR and Western blotting assays, respectively. The differential expression of the genes associated with MAPK pathway in the presence of NS5A gene and plant extract was measured through real-time PCR. Subsequently, the identification of secondary metabolites was carried out by phytochemical and HPLC analysis. Results: The phytochemical profiling of Berberis lyceum revealed the presence of alkaloids, phenols, saponins, tannins, flavonoids, carbohydrates, terpenoids, steroids, and glycosides. Similarly, quercetin, myricetin, gallic acid, caffeic acid, and ferulic acid were identified through HPLC analysis. The methanolic extract of Berberis lyceum strongly inhibited HCV RNA replication with an IC50 of 11.44 µg/mL. RT-PCR and Western blotting assays showed that the extract reduced the expression of HCV NS5A in a dose- dependent manner. Berberis lyceum extract also attenuated NS5A- induced dysregulation of the MAPK signaling pathway. Conclusions: Our findings suggest that Berberis lyceum extract strongly inhibits HCV propagation by reducing HCV NS5A- induced perturbation of MAPK signaling.

Population Pharmacokinetic Analysis of Yimitasvir in Chinese Healthy Volunteers and Patients With Chronic Hepatitis C Virus Infection.

Yimitasvir is a novel, oral hepatitis C virus (HCV) non-structural protein 5A inhibitor for the treatment of chronic HCV genotype 1 infection. The objective of this analysis was to develop a population pharmacokinetic model of yimitasvir in Chinese healthy volunteers and HCV infection patients. The model was performed using data from 219 subjects across six studies. Nonlinear mixed effects models were developed using Phoenix NLME software. The covariates were evaluated using a stepwise forward inclusion (p < 0.01) and then a backward exclusion procedure (p < 0.001). A two-compartment model with sequential zero-first order absorption and first-order elimination reasonably described yimitasvir pharmacokinetics (PK). The apparent oral clearance and central volume of distribution were 13.8 l·h−1 and 188 l, respectively. The bioavailability (F) of yimitasvir decreased 12.9% for each 100 mg dose increase. Food was found to affect absorption rate (Ka) and F. High-fat meal decreased Ka and F by 90.9% and 38.5%, respectively. Gender and alanine aminotransferase were identified as significant covariates on apparent oral clearance. Female subjects had lower clearance than male subjects. Zero-order absorption duration was longer in healthy volunteers (2.17 h) than that in patients (1.43 h). The population pharmacokinetic model described yimitasvir PK profile well. Food decreased Ka and F significantly, so it was recommended to take yimitasvir at least 2 h before or after a meal. Other significant covariates were not clinically important.

Dimer Organization of Membrane‐Associated NS5A of Hepatitis C Virus as Determined by Highly Sensitive 1H‐Detected Solid‐State NMR

AbstractThe Hepatitis C virus nonstructural protein 5A (NS5A) is a membrane‐associated protein involved in multiple steps of the viral life cycle. Direct‐acting antivirals (DAAs) targeting NS5A are a cornerstone of antiviral therapy, but the mode‐of‐action of these drugs is poorly understood. This is due to the lack of information on the membrane‐bound NS5A structure. Herein, we present the structural model of an NS5A AH‐linker‐D1 protein reconstituted as proteoliposomes. We use highly sensitive proton‐detected solid‐state NMR methods suitable to study samples generated through synthetic biology approaches. Spectra analyses disclose that both the AH membrane anchor and the linker are highly flexible. Paramagnetic relaxation enhancements (PRE) reveal that the dimer organization in lipids requires a new type of NS5A self‐interaction not reflected in previous crystal structures. In conclusion, we provide the first characterization of NS5A AH‐linker‐D1 in a lipidic environment shedding light onto the mode‐of‐action of clinically used NS5A inhibitors.

Dimer Organization of Membrane-Associated NS5A of Hepatitis C Virus as Determined by Highly Sensitive 1 H-Detected Solid-State NMR.

The Hepatitis C virus nonstructural protein 5A (NS5A) is a membrane‐associated protein involved in multiple steps of the viral life cycle. Direct‐acting antivirals (DAAs) targeting NS5A are a cornerstone of antiviral therapy, but the mode‐of‐action of these drugs is poorly understood. This is due to the lack of information on the membrane‐bound NS5A structure. Herein, we present the structural model of an NS5A AH‐linker‐D1 protein reconstituted as proteoliposomes. We use highly sensitive proton‐detected solid‐state NMR methods suitable to study samples generated through synthetic biology approaches. Spectra analyses disclose that both the AH membrane anchor and the linker are highly flexible. Paramagnetic relaxation enhancements (PRE) reveal that the dimer organization in lipids requires a new type of NS5A self‐interaction not reflected in previous crystal structures. In conclusion, we provide the first characterization of NS5A AH‐linker‐D1 in a lipidic environment shedding light onto the mode‐of‐action of clinically used NS5A inhibitors.

Efficacy and Safety of All-oral Emitasvir and Sofosbuvir in Patients with Genotype 1b HCV Infections without Cirrhosis

Background and Aims: Emitasvir is a new type of hepatitis C virus (HCV) nonstructural protein 5A (NS5A) inhibitor, and the data of phase 2 trial has shown emitasvir-sofosbuvir to have good safety and tolerance. We conducted this phase 3 trial to further verify the efficacy and safety.Methods: We evaluated the antiviral activity and safety of a 12-week regimen of emitasvir phosphate (100 mg) combined with sofosbuvir (400 mg) once daily in non-cirrhotic patients with genotype 1 HCV infection. The primary endpoint was a sustained virological response at 12 weeks (SVR12) after the end of treatment.Results: Of the 362 patients enrolled in the trial, 39.8% were male, 99.2% had HCV genotype 1b, 0.8% had genotype 1a and 79.8% were treatment-naïve. The average age was 47.2 years. All patients completed the treatment and follow-up. All 3 patients with genotype 1a achieved SVR. Two genotype 1b treatment-naïve patients experienced virologic relapse. The rate of SVR12 was 99.7% (358/359), and SVR24 was 99.4% (357/359) in genotype 1b. Overall, 36.2% had resistance-associated substitutions (RASs) in NS5A and 98.3% had RASs in NS5B at baseline. The RASs at baseline had no effect on the rates of response. Serious adverse events were reported in 16 patients and were not related to emitasvir-sofosbuvir. Most adverse events did not require therapy.Conclusions: The 12 weeks of treatment with emitasvir-sofosbuvir was a highly efficient and safe treatment for a wide range of patients with HCV genotype 1b infection without cirrhosis, who had not been treated or who had been treated with interferon-based regimen previously.