NS5A Inhibitor Research Articles

Real-World Experiences with the Combination Treatment of Ledipasvir plus Sofosbuvir for 12 Weeks in HCV Genotype 1-Infected Japanese Patients: Achievement of a Sustained Virological Response in Previous Users of Peginterferon plus Ribavirin with HCV NS3/4A Inhibitors.

The aim of this study was to characterize the treatment response and serious adverse events of ledipasvir plus sofosbuvir therapies in Japanese patients infected with hepatitis C virus (HCV) genotype 1 (GT1). This retrospective study analyzed 240 Japanese HCV GT1 patients treated for 12 weeks with 90 mg of ledipasvir plus 400 mg of sofosbuvir daily. Sustained virological response at 12 weeks post-treatment (SVR12) was achieved in 236 of 240 (98.3%) patients. Among treatment-naïve patients, SVR12 was achieved in 136 of 138 (98.6%) patients, and among treatment-experienced patients, SVR12 was achieved in 100 of 102 (98.0%) patients. In patients previously treated with peginterferon plus ribavirin with various HCV NS3/4A inhibitors, 100% SVR rates (25/25) were achieved. Two relapsers had HCV NS5A resistance-associated variants (RAVs), but no HCV NS5B-S282 was observed after they relapsed. We experienced two patients with cardiac events during treatment. In conclusion, combination of ledipasvir plus sofosbuvir for 12 weeks is a potential therapy for HCV GT1 patients. Caution is needed for HCV NS5A RAVs, which were selected by HCV NS5A inhibitors and cardiac adverse events.

In Vitro Antiviral Activity and Resistance Profile of the Next-Generation Hepatitis C Virus NS5A Inhibitor Pibrentasvir.

ABSTRACTPibrentasvir (ABT-530) is a novel and pan-genotypic hepatitis C virus (HCV) NS5A inhibitor with 50% effective concentration (EC50) values ranging from 1.4 to 5.0 pM against HCV replicons containing NS5A from genotypes 1 to 6. Pibrentasvir demonstrated similar activity against a panel of chimeric replicons containing HCV NS5A of genotypes 1 to 6 from clinical samples. Resistance selection studies were conducted using HCV replicon cells with NS5A from genotype 1a, 1b, 2a, 2b, 3a, 4a, 5a, or 6a at a concentration of pibrentasvir that was 10- or 100-fold over its EC50 for the respective replicon. With pibrentasvir at 10-fold over the respective EC50, only a small number of colonies (0.00015 to 0.0065% of input cells) with resistance-associated amino acid substitutions were selected in replicons containing genotype 1a, 2a, or 3a NS5A, and no viable colonies were selected in replicons containing NS5A from other genotypes. With pibrentasvir at 100-fold over the respective EC50, very few colonies (0.0002% of input cells) were selected by pibrentasvir in genotype 1a replicon cells while no colonies were selected in other replicons. Pibrentasvir is active against common resistance-conferring substitutions in HCV genotypes 1 to 6 that were identified for other NS5A inhibitors, including those at key amino acid positions 28, 30, 31, or 93. The combination of pibrentasvir with HCV inhibitors of other classes produced synergistic inhibition of HCV replication. In summary, pibrentasvir is a next-generation HCV NS5A inhibitor with potent and pan-genotypic activity, and it maintains activity against common amino acid substitutions of HCV genotypes 1 to 6 that are known to confer resistance to currently approved NS5A inhibitors.

Elbasvir/Grazoprevir: A Review in Chronic HCV Genotypes 1 and 4.

A fixed-dose combination tablet comprising the hepatitis C virus (HCV) NS5A inhibitor elbasvir and the HCV NS3/4A protease inhibitor grazoprevir (elbasvir/grazoprevir; Zepatier™) was recently approved for the treatment of chronic HCV genotype 1 and 4 infection in the EU and the USA. In phase III trials, 12 or 16weeks of treatment with once-daily elbasvir/grazoprevir (fixed-dose tablet or as individual agents), taken with or without ribavirin, generally provided high rates of sustained virological response at 12weeks (SVR12) in treatment-naive and -experienced adult patients with chronic HCV genotype 1a, 1b or 4 infection, including those with or without compensated cirrhosis, HIV co-infection, inherited blood disorders or chronic kidney disease or patients receiving opioid agonist therapy or of Japanese origin. Elbasvir/grazoprevir was generally well tolerated. Thus, elbasvir/grazoprevir, with or without ribavirin, represents an effective new option for the treatment of adults with chronic HCV genotype 1 and 4 infection, including a number of difficult-to-treat populations.

Glecaprevir and pibrentasvir yield high response rates in patients with HCV genotype 1–6 without cirrhosis

Hepatitis C virus (HCV) therapy that is highly efficacious, pangenotypic, with a high barrier to resistance and short treatment duration is desirable. The efficacy and safety of 8- and 12-week treatments with glecaprevir (ABT-493; NS3/4A protease inhibitor) and pibrentasvir (ABT-530; NS5A inhibitor) were evaluated in non-cirrhotic patients with chronic HCV genotype 1-6 infection. SURVEYOR-I and SURVEYOR-II were phase II, open-label, multicenter, dose-ranging trials including patients with chronic HCV genotype 1-6 infection who were either previously untreated or treated with pegylated interferon plus ribavirin. Patients received once-daily glecaprevir plus pibrentasvir at varying doses with or without ribavirin for 8 or 12weeks. The primary efficacy endpoint was the percentage of patients with a sustained virologic response at post-treatment week 12 (SVR12). Of the 449 patients who received varying doses of glecaprevir plus pibrentasvir, 25%, 29%, 39%, and 8% had HCV genotype 1, 2, 3, and 4-6 infection, respectively. Twelve-week treatment achieved SVR12 in 97-100%, 96-100%, 83-94%, and 100% in genotypes 1, 2, 3, and 4-6, respectively. Eight-week treatment with 300mg glecaprevir plus 120mg pibrentasvir in genotype 1-, 2-, or 3-infected patients yielded 97-98% SVR12 with no virologic failures. Three (0.7%) patients discontinued treatment due to adverse events; most events were mild (grade 1) in severity. No post-nadir alanine aminotransferase elevations were observed. Glecaprevir plus pibrentasvir was well tolerated and achieved high sustained virologic response rates in HCV genotypes 1-6-infected patients without cirrhosis following 8- or 12-week treatment durations. The combination of direct-acting antivirals glecaprevir and pibrentasvir comprise a once-daily, all-oral, pangenotypic treatment for HCV genotype 1-6 infection. This article describes results from two phase II trials investigating a range of doses at treatment durations of 8 or 12weeks in 449 patients without cirrhosis. Efficacy of the optimal dose, as determined by rates of sustained virologic response at post-treatment week 12, ranged from 92%-100%; treatment was well tolerated and significant laboratory abnormalities were rare. clinicaltrials.gov Identifiers: NCT02243280 and NCT02243293. http://www.clinicaltrials.gov/show/NCT02243280, http://www.clinicaltrials.gov/show/NCT01939197.

Daclatasvir and asunaprevir for genotype 1b chronic hepatitis C patients with chronic kidney disease

To evaluate the efficacy and safety of daclatasvir and asunaprevir combined therapy in genotype 1b chronic hepatitis C patients with non-dialysis chronic kidney disease (CKD). In a multicenter collaborative study, 249 patients received 60mg daclatasvir (NS5A inhibitor) once a day and 100mg of asunaprevir (NS3/4A protease inhibitor) twice a day for 24weeks between September 2014 and September 2015 and were subjected to this analysis. Virological response and adverse events in non-dialysis patients with CKD (stage 3-5, excluding 5D: dialysis), which was defined as estimated glomerular filtration rate <60mL/min/1.73m2 , were compared with those in patients without CKD. Overall, the rates of rapid viral response, end-of-treatment response, and sustained virological response (SVR) were 76.7%, 91.2%, and 86.3%, respectively. Among 55 patients with CKD, the rapid viral response, end-of-treatment response, and SVR rates were 76.4%, 87.3%, and 83.6%, respectively. Among 194 patients without CKD, they were 76.8, 92.3, and 87.1%, respectively. There were no significant differences in the virological response rates between the two groups (P = 0.999, 0.282, and 0.509, respectively). The baseline estimated glomerular filtration rate did not affect the achievement of SVR. The incidence of adverse events in patients with and without CKD were 21.8% and 13.9%, respectively (not significant, P = 0.142). The efficacy and safety of daclatasvir and asunaprevir combined therapy in genotype 1b chronic hepatitis C patients with non-dialysis CKD are not inferior to those in patients without CKD.

Efficacy of 8 Weeks of Sofosbuvir, Velpatasvir, and Voxilaprevir in Patients With Chronic HCV Infection: 2 Phase 3 Randomized Trials

Patients with chronic hepatitis C virus (HCV) infection have high rates of sustained virologic response (SVR) after 12 weeks of treatment with the nucleotide polymerase inhibitor sofosbuvir combined with the NS5A inhibitor velpatasvir. We assessed the efficacy of 8 weeks of treatment with sofosbuvir and velpatasvir plus the pangenotypic NS3/4A protease inhibitor voxilaprevir (sofosbuvir-velpatasvir-voxilaprevir). In 2 phase 3, open-label trials, patients with HCV infection who had not been treated previously with a direct-acting antiviral agent were assigned randomly to groups given sofosbuvir-velpatasvir-voxilaprevir for 8 weeks or sofosbuvir-velpatasvir for 12 weeks. POLARIS-2, which enrolled patients infected with all HCV genotypes with or without cirrhosis, except patients with genotype 3 and cirrhosis, was designed to test the noninferiority of 8 weeks of sofosbuvir-velpatasvir-voxilaprevir to 12 weeks of sofosbuvir-velpatasvir using a noninferiority margin of 5%. POLARIS-3, which enrolled patients infected with HCV genotype 3 who had cirrhosis, compared rates of SVR in both groups with a performance goal of 83%. In POLARIS-2, 95% (95% confidence interval [CI], 93%-97%) of patients had an SVR to 8 weeks of sofosbuvir-velpatasvir-voxilaprevir; this did not meet the criterion to establish noninferiority to 12 weeks of sofosbuvir-velpatasvir, which produced an SVR in 98% of patients (95% CI, 96%-99%; difference in the stratum-adjusted Mantel-Haenszel proportions of -3.2%; 95% CI, -6.0% to -0.4%). The difference in the efficacy was owing primarily to a lower rate of SVR (92%) among patients with HCV genotype 1a infection receiving 8 weeks of sofosbuvir-velpatasvir-voxilaprevir. In POLARIS-3, 96% of patients (95% CI, 91%-99%) achieved an SVR in both treatment groups, which was significantly superior to the performance goal. Overall, the most common adverse events were headache, fatigue, diarrhea, and nausea; diarrhea and nausea were reported more frequently by patients receiving voxilaprevir. In both trials, the proportion of patients who discontinued treatment because of adverse events was low (range, 0%-1%). In phase 3 trials of patients with HCV infection, we did not establish that sofosbuvir-velpatasvir-voxilaprevir for 8 weeks was noninferior to sofosbuvir-velpatasvir for 12 weeks, but the 2 regimens had similar rates of SVR in patients with HCV genotype 3 and cirrhosis. Mild gastrointestinal adverse events were associated with treatment regimens that included voxilaprevir. ClinicalTrials.gov numbers: POLARIS-2, NCT02607800; and POLARIS-3, NCT02639338.

Mechanisms involved in liver damage resolution after hepatitis C virus clearance

Abstract Worldwide, the hepatitis C virus (HCV) infection is a leading etiology of cirrhosis and hepatocellular carcinoma (HCC). The main complications of chronic HCV infection are fibrosis, cirrhosis and HCC. Nowadays, there are several options accessible for HCV treatment, such as direct-acting antiviral agents (DAAs), including HCV protease inhibitors, polymerase inhibitors, and NS5A inhibitors. Once the virus is eliminated after the specific antiviral treatments, patients should try to re-establish their metabolic functions efficiently from an environment where there was great cellular destruction. Another goal for the liver can range from fibrosis to decompensate cirrhosis. For this reason, upon the use of DAAs therapy, assuming that SVR is reached, the use of antifibrotic drugs is increasing in order to improve liver regeneration by decreasing fibrotic tissue generated by HCV. Liver fibrosis is defined as the excessive accumulation of extracellular matrix proteins because of the interaction of a number of different cell types, among them hepatic stellate cells. Once the causative agent of damage is removed, the progression of liver disease is attenuated. However, if the patient has an advanced state of fibrosis or cirrhosis, hepatic regeneration becomes a challenge where numerous known and unknown cellular mechanisms are involved. Fortunately, there are drugs that facilitate this process of reversion, however, it is still not clear that conditions favor the success of this regression.

Long-term persistence of HCV NS5A resistance-associated substitutions after treatment with the HCV NS5A inhibitor, ledipasvir, without sofosbuvir.

Data on persistence of NS5A resistance-associated substitutions (RASs) may have implications for resistance testing approaches and selection of initial and retreatment strategies. Long-term persistence of NS5A RASs in HCV genotype (GT) 1 infected subjects (n=76) who did not achieve sustained virological response after receiving ledipasvir (LDV) without sofosbuvir (SOF) and were subsequently enrolled in an ongoing 3-year follow-up registry study was investigated by population or deep sequencing. Of the 76 subjects enrolled, 67 and 9 subjects had GT1a and GT1b infection, respectively. At pretreatment, NS5A RASs were detected in 14% of subjects (11/76) by population sequencing, with three subjects having >1 RAS. All RASs that were detected at pretreatment persisted and were observed at the 96 week visit in the follow-up study (FU96). For the remaining subjects with no detectable RASs at pretreatment, RASs were detected in 98% (63/64) of subjects at virological failure in the parent study and persisted at detectable levels through FU96 in 86% of subjects by deep sequencing (1% cutoff). However, a decline in the quasispecies frequency of most RASs and the number of RASs per subject was observed over time. Phenotypic analysis demonstrated that the majority of NS5A RASs confer similar levels of resistance to LDV and daclatasvir. The majority of NS5A RASs can persist at detectable levels for >96 weeks post-treatment in subjects who failed treatment with regimens containing an NS5A inhibitor without SOF, suggesting relatively high fitness of NS5A RASs even in the absence of drug pressure.

Direct acting anti-hepatitis C virus drugs: Clinical pharmacology and future direction

Chronic hepatitis C virus (HCV) infection is a leading cause of chronic liver disease. The introduction of direct acting antiviral agents (DAAs) for its treatment represents a major advance in terms of sustained virologic response (SVR) rates and adverse effect profiles. Mechanistically, DAAs inhibit specific HCV non-structural proteins (NS) that are vital for its replication. Boceprevir, telaprevir, simeprevir, asunaprevir, grazoprevir and paritaprevir are NS3/4A inhibitors. Ombitasvir, ledipasvir, daclatasvir, elbasvir and velpatasvir are NS5A inhibitors. Sofosbuvir and dasabuvir are NS5B inhibitors. Currently, a combination of two or more DAAs is the corner stone for the treatment of HCV infection. However, the success of DAA therapy is facing several challenges, including the potential of drug-drug interactions and resistant variance. Moreover, the shortage of relevant clinical pharmacological data and drug interaction regarding DAA is a clinical concern. The present review discusses the clinical pharmacology of DAAs with special emphasis on drug-drug interaction.

Synthesis and evaluation of novel HCV replication inhibitors.

Direct acting antiviral agents to cure hepatitis C virus (HCV) infection has emerged as the gold standard therapy. Along with protease inhibitors, nucleoside polymerase inhibitors and non-nucleoside polymerase inhibitors, the inhibition of NS5a has proved to be an effective way to treat HCV patients. Here we report on novel HCV NS5a inhibitors which were synthesized and evaluated in the HCV replicon assay. A series of inhibitors were formed by a cycloaddition reaction in parallel to establish new leads and explore the effects of unsymmetrical cap substitution. This led to the identification of several triazoles with picomolar potency in vitro against hepatitis C virus.

Resistance testing for the treatment of chronic hepatitis C with direct acting antivirals: when and for how long?

The need to test for resistance associated substitutions (RAS) has been intensively debated in the past two years. In the absence of pangenotypic combinations, it seems reasonable that, if available, RAS testing in the NS5A gene at baseline for genotypes 1a and 3 may help to avoid overtreatment in terms of ribavirin usage and/or prolonged treatment duration. When patients fail treatment, RAS testing may also be useful to guide the selection of the new regimen, especially for those that need urgent retreatment and that have failed a combination including an NS5A inhibitor. However, there are new drugs in the pipeline that in combination are pangenotypic, very potent and with a high genetic barrier to resistance. In this new scenario, RAS testing may not play such an important role.

Ledipasvir–sofosbuvir for 6 weeks to treat acute hepatitis C virus genotype 1 or 4 infection in patients with HIV coinfection: an open-label, single-arm trial

The latest European Association for the Study of the Liver (EASL) guidelines now recommend that patients with acute hepatitis C virus (HCV) infection should be treated with a combination of sofosbuvir and an NS5A inhibitor for 8 weeks. However, the ideal duration of treatment with interferon-free regimens, particularly in HIV-coinfected individuals, remains unknown. We assessed the efficacy and safety of 6 weeks of ledipasvir-sofosbuvir for acute genotype 1 or 4 HCV in HIV-1-coinfected patients. This open-label, single-arm trial, done in Germany and the UK, included patients with acute HCV genotype 1 or 4 and HIV-1. At screening, patients were either receiving HIV antiretrovirals and had HIV RNA less than 200 copies per mL, or not receiving antiretrovirals and had a CD4 T-cell count of greater than 500 cells per μL. All patients received ledipasvir-sofosbuvir once daily for 6 weeks. The primary efficacy endpoint was the proportion of patients with sustained virological response 12 weeks after the end of treatment (SVR12). This study is registered with ClinicalTrials.gov, number NCT02457611. Between June 11, 2015, and Jan 8, 2016, we enrolled and treated 26 patients. All (100%) were men, 24 (92%) were white, and 25 (96%) were receiving antiretroviral treatment. 19 (73%) had genotype 1a and seven (27%) had genotype 4 HCV. Overall, 20 (77%; 95% CI 56-91) of 26 patients achieved SVR12: 15 (79%) of 19 with genotype 1a, and five (71%) of seven with genotype 4. Of six patients not achieving SVR12, three relapsed, two achieved sustained virological response 4 weeks after the end of treatment but were lost to follow-up, and one was reinfected. The most common adverse events were fatigue (seven participants [27%]), nasopharyngitis (seven [27%]), and headache (six [23%]). No patient discontinued or interrupted therapy due to adverse events. No HIV rebound occurred during the study. The rate of cure with a fixed-dose combination of ledipasvir-sofosbuvir for patients with acute genotype 1 or 4 HCV infection and HIV-1 coinfection is similar to historic rates with interferon-based treatment, but with shorter treatment duration and more favourable safety outcomes. Gilead Sciences.

Ledipasvir plus sofosbuvir as salvage therapy for HCV genotype 1 failures to prior NS5A inhibitors regimens.

There is little information on retreatment efficacy and predictors of the combination of ledipasvir and sofosbuvir (ledipasvir/sofosbuvir) for patients who fail to respond to NS5A inhibitors. NS5A resistance variants are known to persist for long periods after such treatment. Here, we evaluated 54 patients with chronic HCV genotype 1b infection, free of decompensated cirrhosis, and hepatocellular carcinoma, for sustained virological response after 12 weeks (SVR12) of once-daily treatment with 90 mg ledipasvir and 400 mg sofosbuvir. Intention-to-treat analysis showed SVR12 of 70%. Using ultra-deep sequencing, non-responder to ledipasvir/sofosbuvir showed no change in the rates of detection of NS5A and NS5B resistant-variants at re-elevation of viral loads, relative to baseline. According to response to prior treatment, SVR12 rates were 18, 69, 94, and 100% in non response, viral breakthrough, relapse, and discontinuation due to adverse events, respectively. SVR12 rates in non response were significantly lower than those of the others. Multivariate analysis identified response to previous treatment (failure except for non response) and FIB4 index (<3.25) as significant determinants of SVR12. The SVR12 rates were significantly lower in patients with FIB4 index of ≥3.25 and had not responded to prior treatment, relative to others. The specificity, and positive- and negative-predictive values were high for prediction of poor response based on the combination of two predictors. In conclusion, our study indicated that ledipasvir/sofosbuvir is a potentially useful salvage treatment for patients who fail prior NS5A inhibitors-based therapy. Response to prior treatment was an important predictor of retreatment efficacy.

INF-free sofosbuvir-based treatment of post-transplant hepatitis C relapse – a Swedish real life experience

Background: Relapse of hepatitis C virus (HCV) infection after liver transplantation has been universal, and the fibrosis progression faster than in non-transplanted patients. Interferon (IFN)-free treatment with direct antiviral agents (DAA) has improved the treatment outcome dramatically. We here report on the outcome of IFN-free treatment for HCV relapse after liver transplantation in a real life setting in Sweden.Material: In total, 93 patients with a mean age of 60 years (range 32–80) with HCV relapse after liver transplantation were given sofosbuvir-based treatment in combination with a protease inhibitor (simeprevir) or a NS5A inhibitor (daclatasvir or ledipasvir) with or without addition of ribavirin (RBV), or sofosbuvir and RBV only. Treatment was generally given during 24 weeks for advanced fibrosis or cirrhosis cases and 12 weeks for mild fibrosis with fibrosis stage 2 or less. The distribution of genotype 1, 2, 3, 4 in our patients was 58, 7.5, 26.5 and 7.5%, respectively.Results: All recipients reached end-of-treatment response (ETR) with HCV RNA <15 IU/mL. Sustained viral response 12 weeks after treatment cessation (SVR12) was achieved in 91/93 (97.8%) recipients. The SVR12 rates for genotype 1, 2, 3 and 4 were the SVR12 rate were 96, 100, 100 and 100%, respectively (p = .04).Conclusion: It is concluded that IFN-free treatment with DAAs for HCV relapse after liver transplantation is highly effective also in a real life setting and offers cure for most recipients.

Sofosbuvir/velpatasvir regimen promises an effective pan-genotypic hepatitis C virus cure.

Hepatitis C virus (HCV) is a global pandemic, with nearly 200 million infected patients worldwide. HCV is the most common blood-borne infection in the US with numerous health implications including liver fibrosis, cirrhosis, and hepatocellular cancer. Traditional genotype-based HCV therapies with interferon resulted in moderate success in the sustained elimination of viral genome. Recent clinical trials of the once-daily combination tablet of sofosbuvir, a nonstructural (NS) 5B polymerase inhibitor, and velpatasvir, an NS5A inhibitor, demonstrate sustained virologic response rates of about 95%, regardless of prior treatment experience or presence of cirrhosis across all HCV genotypes. Patients reported improvements in general health, fatigue, and emotional and mental well-being after completing combination therapy. The combination treatment is effective, but does need to be administered with caution in patients receiving certain medications or with certain diseases. Herein, we review the safety and efficacy of sofosbuvir/velpatasvir combination regimen for all HCV genotypes.

Future Paradigms of HCV Management with Resistance Testing

Following an overview of HCV resistance terminology and epidemiology, approaches to managing hepatitis C virus (HCV) resistance-associated substitutions (RASs) are presented according to the HCV treatment regimen being considered, with a focus primarily on NS5A inhibitor-associated RASs. Research on the impact of HCV RASs has recently focused on identifying specific patient populations most impacted by the presence of baseline RASs. The available treatment regimens each have unique considerations based on viral and patient specific factors. Effective treatment strategies for the retreatment of patients who have failed DAA regimens are now being evaluated. RASs to NS5A inhibitors are the most clinically relevant, particularly in patients with genotypes 1a and 3. The greatest impact of NS5A inhibitor RASs is seen in patients with cirrhosis and/or patients who are treatment experienced. Effective interventions in the setting of resistance include the addition of ribavirin, extension of therapy, and/or selection of alternative HCV treatment regimens. However, the intervention for a given patient will also depend on other factors such as the presence or absence of cirrhosis and the treatment regimen(s) being considered.

Study on the forced degradation behaviour of ledipasvir: Identification of major degradation products using LC–QTOF–MS/MS and NMR

Ledipasvir, a novel NS5A inhibitor is used in the management of hepatitis C virus infections. The drug was subjected to forced degradation studies as per the conditions prescribed in ICH Q1 (R2) guideline. Ledipasvir degraded in hydrolytic (acid, alkaline and neutral) and oxidative stress conditions. The drug was found to be stable in thermal and photolytic conditions. Eight novel degradation products were obtained and were well separated using an HPLC C18 stationary phase (150×4.6mm, 5μm) and mobile phase composed of formic acid/acetonitrile in gradient elution mode. All the degradation products were characterised using tandem mass spectrometry with a time-of-flight analyser and the major degradation products of hydrolytic and oxidative stress were isolated and their structural confirmation was studied using 1H and 13C NMR. A well resolved chromatographic method proposed in this study suggests that the proposed analytical method finds its application as a stability indicating assay method for the drug and can be used in routine analysis.

NS5A resistance-associated substitutions in patients with genotype 1 hepatitis C virus: Prevalence and effect on treatment outcome

The efficacy of NS5A inhibitors for the treatment of patients chronically infected with hepatitis C virus (HCV) can be affected by the presence of NS5A resistance-associated substitutions (RASs). We analyzed data from 35 phase I, II, and III studies in 22 countries to determine the pretreatment prevalence of various NS5A RASs, and their effect on outcomes of treatment with ledipasvir-sofosbuvir in patients with genotype 1 HCV. NS5A gene deep sequencing analysis was performed on samples from 5397 patients in Gilead clinical trials. The effect of baseline RASs on sustained virologic response (SVR) rates was assessed in the 1765 patients treated with regimens containing ledipasvir-sofosbuvir. Using a 15% cut-off, pretreatment NS5A and ledipasvir-specific RASs were detected in 13% and 8% of genotype 1a patients, respectively, and in 18% and 16% of patients with genotype 1b. Among genotype 1a treatment-naïve patients, SVR rates were 91% (42/46) vs. 99% (539/546) for those with and without ledipasvir-specific RASs, respectively. Among treatment-experienced genotype 1a patients, SVR rates were 76% (22/29) vs. 97% (409/420) for those with and without ledipasvir-specific RASs, respectively. Among treatment-naïve genotype 1b patients, SVR rates were 99% for both those with and without ledipasvir-specific RASs (71/72 vs. 331/334), and among treatment-experienced genotype 1b patients, SVR rates were 89% (41/46) vs. 98% (267/272) for those with and without ledipasvir-specific RASs, respectively. Pretreatment ledipasvir-specific RASs that were present in 8-16% of patients have an impact on treatment outcome in some patient groups, particularly treatment-experienced patients with genotype 1a HCV. The efficacy of treatments using NS5A inhibitors for patients with chronic hepatitis C virus (HCV) infection can be affected by the presence of NS5A resistance-associated substitutions (RASs). We reviewed results from 35 clinical trials where patients with genotype 1 HCV infection received treatments that included ledipasvir-sofosbuvir to determine how prevalent NS5A RASs are in patients at baseline, and found that ledipasvir-specific RASs were present in 8-16% of patients prior to treatment and had a negative impact on treatment outcome in subset of patient groups, particularly treatment-experienced patients with genotype 1a HCV.

Population Pharmacokinetic Analysis of Daclatasvir in Subjects with Chronic Hepatitis C Virus Infection.

Daclatasvir is a potent, pangenotypic once-daily hepatitis C virus (HCV) NS5A inhibitor that is approved for the treatment of chronic HCV infection. The objective of this analysis was to characterize the pharmacokinetics of daclatasvir in subjects with chronic HCV infection. A population pharmacokinetic (PPK) model was developed to evaluate effects of covariates on daclatasvir pharmacokinetics in subjects with chronic HCV infection (n=2149 from 11 studies). All significant demographic, laboratory, prognostic and treatment covariates (p<0.05) from univariate screening were included in the full model. The final model was reached by backward elimination (p<0.001) and simulations were performed to further evaluate the effects of covariates on daclatasvir exposures. The plasma pharmacokinetics of daclatasvir was described by a two-compartment model with linear elimination. Absorption was modeled as a zero-order release followed by a first-order absorption into the central compartment. The typical value of apparent clearance (CL/F) was 5.7L/h (1.58% relative standard error [RSE]) and of apparent volume of the central compartment (V c/F) was 58.6L (2.00% RSE). Modest inter-individual variability was estimated for CL/F (35.1%) and V c/F (29.5%). Statistically significant covariates in the final model were sex, race, virus genotype, baseline creatinine clearance, and alanine aminotransferase (ALT) on CL/F and sex, race, and body weight on V c/F. Covariate effects demonstrated a 30% higher area under the plasma concentration-time curve at steady state (AUCss) in female subjects; effects of all other covariates were <16%. The model adequately described the daclatasvir pharmacokinetics and estimated relatively small covariate effects. Considering the exposure range for the therapeutic dose of daclatasvir 60mg once daily and the favorable safety profile, the small difference in exposures due to these covariates is not considered clinically relevant.

Retinoid BMS411 (4-{[(5,5-dimethyl-8-phenyl-5,6-dihydronaphthalen-2-yl) carbonyl] amino} benzoic acid), a potential inhibitor of NS5A protein of hepatitis C virus, a candidate for combined therapy of hepatitis C infection.

Hepatitis C infection is a serious health issue worldwide caused by hepatitis C virus (HCV). There is an urgent need of search for new direct acting antiviral drugs due to the rapid development of drug resistance. The HCV NS5A protein is involved in creating resistance against antiviral therapy and there are also many reports that vitamin A deficiency is associated with non-responsiveness to antiviral treatment in HCV infected patients. So the present in silico study was aimed to find the relation between vitamin A deficiency and the NS5A protein's function in antiviral resistance. Structure of NS5A protein was predicted by using I-Tasser (Interactive Tasser). Previous data on conservative domains and dimer formation were confirmed by using a series of current computational methods. The structure was employed for molecular docking analysis to investigate the interaction of ligand BMS411 (4-[(5,5-dimethyl-8-phenyl-6H-naphthalene-2-carbonyl)amino]benzoic acid), a vitamin A related compound with NS5A protein. Docking analysis showed that retinoid BMS411 can bind to HCV NS5A protein and may act as inhibitor of this protein. The functionally interacting amino acid residues surrounding the ligand molecule were identified and were shown to be involved in the formation of binding pocket. The present study suggests that retinoids may play an important role in the improvement of the outcomes of antiviral therapy against HCV through interaction with NS5A and inhibition of this protein. It is of great importance to check and verify if other retinoids could act as NS5A inhibitors.