Sofosbuvir: A Nucleotide NS5B Inhibitor for the Treatment of Chronic Hepatitis C Infection

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.

Electrochemical sensor based on bio-inspired molecularly imprinted polymer for sofosbuvir detection

The electropolymerized molecularly imprinted polymers (MIP) have enabled the utilization of various functional monomers with superior selective recognition of the target analyte template. Methyldopa is an attractive synthetic dopamine analogue which has phenolic, carboxylic, and aminic functional groups. In this research, methyldopa was exploited to fabricate selective MIPs, for the detection of sofosbuvir (SFB), by a simple electropolymerization step onto a disposable pencil graphite electrode (PGE) substrate. The interaction between methyldopa, as a functional monomer, and a template has been investigated experimentally by UV spectroscopy. A polymethyldopa (PMD) polymer was electrografted onto PGE in the presence of SFB as a template. X-ray photoelectron spectroscopy (XPS), electrochemical impedance spectroscopy (ESI), and cyclic voltammetry (CV) were used for the characterization of the fabricated sensor. Differential pulse voltammetry (DPV) of a ferrocyanide/ferricyanide redox probe was employed to indirectly detect the SFB binding to the MIP cavities. The sensor shows a reproducible and linear response over a dynamic linear range from 1.0 × 10-11 M to 1.0 × 10-13 M of SFB with a limit of detection of 3.1 × 10-14 M. The sensor showed high selectivity for the target drug over structurally similar and co-administered interfering drugs, and this enabled its application to detect SFB in its pharmaceutical dosage form and in spiked human plasma samples.

COVID-19 therapeutics: Clinical application of repurposed drugs and futuristic strategies for target-based drug discovery

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) causes the complicated disease COVID-19. Clinicians are continuously facing huge problems in the treatment of patients, as COVID-19-specific drugs are not available, hence the principle of drug repurposing serves as a one-and-only hope. Globally, the repurposing of many drugs is underway; few of them are already approved by the regulatory bodies for their clinical use and most of them are in different phases of clinical trials. Here in this review, our main aim is to discuss in detail the up-to-date information on the target-based pharmacological classification of repurposed drugs, the potential mechanism of actions, and the current clinical trial status of various drugs which are under repurposing since early 2020. At last, we briefly proposed the probable pharmacological and therapeutic drug targets that may be preferred as a futuristic drug discovery approach in the development of effective medicines.

Hydrogen Bonding (Base Pairing) in Antiviral Activity

Base pairing based on hydrogen bonding has, since its inception, been crucial in the antiviral activity of arabinosyladenine, 2'-deoxyuridines (i.e., IDU, TFT, BVDU), acyclic nucleoside analogues (i.e., acyclovir) and nucleoside reverse transcriptase inhibitors (NRTIs). Base pairing based on hydrogen bonding also plays a key role in the mechanism of action of various acyclic nucleoside phosphonates (ANPs) such as adefovir, tenofovir, cidofovir and O-DAPYs, thus explaining their activity against a wide array of DNA viruses (human hepatitis B virus (HBV), human immunodeficiency (HIV) and human herpes viruses (i.e., human cytomegalovirus)). Hydrogen bonding (base pairing) also seems to be involved in the inhibitory activity of Cf1743 (and its prodrug FV-100) against varicella-zoster virus (VZV) and in the activity of sofosbuvir against hepatitis C virus and that of remdesivir against SARS-CoV-2 (COVID-19). Hydrogen bonding (base pairing) may also explain the broad-spectrum antiviral effects of ribavirin and favipiravir. This may lead to lethal mutagenesis (error catastrophe), as has been demonstrated with molnutegravir in its activity against SARS-CoV-2.

Regulatory Role of Ribonucleotide Reductase Subunit M2 in Hepatocyte Growth and Pathogenesis of Hepatitis C Virus

Hepatitis C virus (HCV) frequently causes chronic infection in the human liver, which may progress to advanced hepatic fibrosis, cirrhosis, and hepatocellular carcinoma. HCV primarily infects highly differentiated quiescent hepatocytes and can modulate cell cycle-regulatory genes and proliferation pathways, which ultimately contribute to persistent infection and pathogenesis. On the other hand, several studies have shown differential regulation of HCV RNA and viral protein expression levels, depending on the proliferation state of hepatocytes and the phase of the cell cycle. HCV typically requires factors provided by host cells for efficient and persistent viral replication. Previously, we found that HCV infection upregulates the expression of ribonucleotide reductase subunit M2 (RRM2) in quiescent hepatocytes. RRM2 is a rate-limiting protein that catalyzes de novo synthesis of deoxyribonucleotide triphosphates, and its expression is highly regulated during various phases of the cell cycle. RRM2 functions as a pro-viral factor essential for HCV RNA synthesis, but its functional role in HCV-induced liver diseases remains unknown. Here, we present a comprehensive review of the role of the hepatocyte cell cycle, in correlation with RRM2 expression, in the regulation of HCV replication. We also discuss the potential relevance of this protein in the pathogenesis of HCV, particularly in the development of hepatocellular carcinoma.

Direct-acting antiviral retreatment patterns for hepatitis C

BACKGROUND: Despite the strong efficacy of direct-acting antivirals (DAAs) against the hepatitis C virus, many patients require a second regimen of DAA treatment. However, limited research exists to characterize rates of retreatment across different DAA agents or potential factors that may increase retreatment risk. OBJECTIVE: To characterize patterns and predictors of DAA retreatment among a large, generalizable, commercially insured US population of patients. METHODS: Using the IBM MarketScan Commercial Claims and Encounters data source, this retrospective cohort study examined retreatment patterns among patients receiving DAAs between 2013 and 2019. Descriptive statistics were used to compare patient characteristics predictive of retreatment risk and to examine rates of retreatment in patients initiating different DAA treatments. RESULTS: Among 31,553 DAA users, a total of 1,017 (3.2%) required DAA retreatment. Among the 1,017 patients re-treated, 44 (4.3%) received a third treatment regimen and 2 patients received a fourth treatment regimen. The average total cost for a retreatment regimen was $109,683, with patient out-of-pocket costs totaling $1,287 Patients requiring retreatment had higher rates of hypertension (32.0% vs 26.7%; P < 0.001), diabetes (16.9% vs 11.9%; P < 0.001), coagulopathy (9.9% vs 4.5%; P < 0.001), deficiency anemia (11.1% vs 7.4%; P < 0.001), alcohol abuse (3.3% vs 2.3%; P = 0.038), prior liver transplantation (3.4% vs 2.3%; P = 0.024), and hepatocellular carcinoma (6.1% vs 1.9%; P < 0.001) compared with patients not requiring retreatment. CONCLUSIONS: Although uncommon, some patients receiving DAAs require a second regimen of DAA treatment at substantial cost to both health plans and patients. These patients tend to have more comorbidities and markers of hepatic disease severity. Patients with high retreatment risk may benefit from careful monitoring for occurrences of retreatment.

Interleukin 28B Polymorphism as a Predictor of Sustained Virological Response to Sofosbuvir-Based Therapy for Hepatitis C Virus Patients

In various genome-wide correlation studies, interleukin (IL)28B gene polymorphism has been strongly correlated with both the therapeutic and spontaneous mediated clearance of hepatitis C virus (HCV). Therefore, this study aimed to evaluate the genotype and allele frequency distributions of IL28B (rs12979860) in patients with chronic hepatitis C and assess the IL28B polymorphisms as predictors of sustained virological response to SOF-based therapy for HCV in Egyptian patients. This retrospective case-control study was conducted on 54 chronic HCV patients who completed treatment with SOF/DCV ± RBV for 12 weeks and responded to treatment with SVR12 (the responder group) as a control group, and 54 chronic HCV patients who completed treatment with SOF/DCV ± RBV for 12 weeks and did not respond to treatment and failed to achieve SVR12 (the non-responder group) as a case group. The CC genotype frequency of IL-28B (rs12979860) was greater in the responder group (51.9%). In contrast, the TT genotype frequency was higher in the non-responder group (48.1%) (p < 0.001), and the T allele significantly increased the risk of non-responses by 3.13 fold. Therefore IL-28B (rs12979860) SNP could be used as a genetic predictor of sustained virological response to SOF+DCV ± RBV-based HCV treatment in Egyptian patients.

Sofosbuvir/velpatasvir for the treatment of hepatitis C in pediatric patients

Introduction: Sofosbuvir/velpatasvir is a combination of direct-acting antivirals with pangenotypic activity for treatment of chronic hepatitis C virus infection. It was approved in 2020 for use in children aged 6-17 years and in June 2021 by the United States Food and Drug Administration for the age group 3-5 years.Areas covered: A literature search of PUBMED and EMBASE was conducted on April 30th and updated on June 10th. Other citations were identified in references of available literature and from ClinicalTrials.gov. The aim of the present research was to outline and discuss the pharmacokinetics, clinical efficacy, tolerability and safety of sofosbuvir/velpatasvir, exploring its actual and potential use in children and adolescents with chronic hepatitis C virus infection.Expert opinion: Five combinations of direct-acting antivirals, of whom three with pangenotypic activity, are now approved for children. No major differences in efficacy and safety profile have been described. Limited access to treatment still is a major issue, especially in low and middle-income countries.

Interferon lambda 4 gene polymorphisms as a predicting tool of response to hepatitis C virus genotype 4 patients treated with Sofosbuvir and Ribavirin

The relation between interferon lambda 4 gene (IFNL4) and direct acting antiviral (DAA) regimens in hepatitis C virus (HCV) infected patients is not clear. So, a single nucleotide polymorphisms (SNP) of IFNL4 gene genotypes and its relationship with Sofosbuvir (SOF) and Ribavirin (RBV) treatment response is under consideration. This study aims to investigate the relation between IFNL4 polymorphisms and clearance of HCV genotype 4 for HCV patients. Hence, the appropriate drug can be chosen for each patient. SNP genotyping assay for IFNL4 which formerly known as IL28B (rs368234815) was examined for genomic DNA. The DNA was extracted from whole blood of one hundred patients who documented to have infection with chronic HCV genotype 4 (positive PCR) and treated with SOF and RBV. Patients were diagnosed, previously, as HCV genotype 4 and classified according to drug response into two groups (responders, non-responders). All samples were compared with 50 of non-infected (negative PCR) people (control group). The TT/TT homozygous represents 48% of patients and 66% of non-infected people while the homozygous ∆G/∆G is 21% and 12%, respectively. There is significance to IFNL4 genotypes for the treatment response with the probability value p < 0.001. The percentages of the appearance of genotypes TT/TT, TT/∆G and ∆G/∆G for responders were 60%, 28% and 12%, respectively. There is no significance for gender, age, ALT and PLC to treatment response to SOF and RBV, while INR has.

Sofosbuvir plus ribavirin is tolerable and effective even in elderly patients 75-years-old and over

BACKGROUND

Although clinical use of sofosbuvir plus ribavirin has been approved for patients infected with genotype 2 hepatitis C virus, patients ≥ 75-years-old have not been included in previous clinical trials.

AIM

To evaluate the real-world safety and efficacy of sofosbuvir plus ribavirin for elderly patients (≥ 75-years-old) compared to nonelderly patients, we conducted a post-marketing prospective cohort study.

METHODS

We treated 265 patients with genotype 2 hepatitis C virus using standard approved doses of sofosbuvir (400 mg/d) plus ribavirin adjusted by body weight, administered orally for 12 wk.

RESULTS

Sustained virological response rates for the overall cohort, patients < 65-years-old, ≥ 65-years-old but < 75-years-old, and ≥ 75-years-old were 97% (258/265), 98% (93/95), 97% (84/87), and 98% (81/83), respectively (P = 0.842). Logistic regression analyses identified history of hepatocellular carcinoma treatment and alpha-fetoprotein as factors significantly associated with sustained virological response. Alpha-fetoprotein was the only independent factor identified. Sustained virological response rate was significantly lower for patients with hepatocellular carcinoma treatment (91%) than for patients without history of hepatocellular carcinoma treatment (98%, P = 0.004). One patient (0.4%) discontinued treatment due to drug-induced pneumonia. Dose reduction or interruption of ribavirin was required for 12.1% (32/265) of patients because of anemia, including 7.7% (14/182) of patients < 75-years-old and 21.7% (18/83) of patients ≥ 75-years-old (P = 0.002).

CONCLUSION

Although ribavirin dose reduction or interruption was required with advanced age, sofosbuvir plus ribavirin appears tolerable and highly effective even in patients ≥ 75-years-old.

Drug repurposing of pyrimidine analogs as potent antiviral compounds against human enterovirus A71 infection with potential clinical applications

Enterovirus A71 (EV-A71) is one of the aetiological agents for the hand, foot and mouth disease (HFMD) in young children and a potential cause of neurological complications in afflicted patients. Since its discovery in 1969, there remains no approved antiviral for EV-A71 and other HFMD-causing enteroviruses. We set out to address the lack of therapeutics against EV-A71 by screening an FDA-approved drug library and found an enrichment of hits including pyrimidine antimetabolite, gemcitabine which showed 90.2% of inhibition on EV-A71 infection. Gemcitabine and other nucleoside analogs, LY2334737 and sofosbuvir inhibition of EV-A71 infection were disclosed using molecular and proteomic quantification, and in vitro and in vivo efficacy evaluation. Gemcitabine displayed a significant reduction of infectious EV-A71 titres by 2.5 logs PFU/mL and was shown to target the early stage of EV-A71 viral RNA and viral protein synthesis process especially via inhibition of the RNA dependent RNA polymerase. In addition, the drug combination study of gemcitabine's synergistic effects with interferon-β at 1:1 and 1:2 ratio enhanced inhibition against EV-A71 replication. Since gemcitabine is known to metabolize rapidly in vivo, other nucleoside analogs, LY2334737 and sofosbuvir conferred protection in mice against lethal EV-A71 challenge by potentially reducing the death rate, viral titers as well on virus-induced pathology in the limb muscle tissue of mice. Additionally, we found that gemcitabine is competent to inhibit other positive-sense RNA viruses of the Flaviviridae and Togaviridae family. Overall, these drugs provide new insights into targeting viral factors as a broad-spectrum antiviral strategy with potential therapeutic value for future development and are worthy of potential clinical application.

Successful sofosbuvir lead-in monotherapy for the treatment of hepatitis C virus (HCV) infection in a pregnant woman living with HIV

A 30-year-old woman living with HIV was diagnosed with genotype 2b hepatitis C virus (HCV) infection during the second trimester of her pregnancy. She had achieved virologic suppression on an HIV protease inhibitor-based regimen and had recurrent genital herpes simplex virus infection managed with antivirals. Given the risk of perinatal transmission of HCV and to avoid performing a caesarean section, after multidisciplinary consultations and consideration of the limited data on safety on HCV direct-acting antivirals (DAAs) in pregnancy, she consented to and was successfully treated with a 6-week lead-in course of sofosbuvir (SOF) alone followed by a 6-week course of SOF and velpatasvir postpartum. This resulted in cure of her HCV infection. The neonate tested negative for HCV at birth and was healthy without birth defects 2 years postdelivery. Our case highlights a successful HCV treatment approach in a pregnant woman with newer DAAs.

Quick and Sensitive UPLC-ESI-MS/MS Method for Simultaneous Estimation of Sofosbuvir and Its Metabolite in Human Plasma

A simple, fast and highly sensitive RP-UPLC-MS/MS method was developed and validated for the simultaneous determination of sofosbuvir (SR) and its metabolite GS331007 in human plasma using ketotifen as an internal standard (IS). The separation was achieved on Acquity UPLC BEH C₁₈ (50 × 2.1 mm, i.d. 1.7 µm, Waters, USA) column using acetonitrile:5 mM ammonium formate:0.1% formic acid (85:15:0.1% v/v/v) as a mobile phase at a flow rate of 0.35 mL/min in an isocratic elution. The Xevo TQD UPLC-MS/MS was operated under the multiple-reaction monitoring mode using positive electrospray ionization. Extraction with dichloromethane was used in the sample preparation. Method validation was performed as per the Food and Drug Administration (FDA) guidelines and the calibration curves of the proposed method were found to be linear in the range of 1–1000 ng/mL for SR and in the range of 10–1500 ng/mL for its metabolite (GS331007) with an elution time of 1.83 min. All validation parameters were within the acceptable range according to the bioanalytical methods validation guidelines. Furthermore, the obtained results of matrix effects indicate that ion suppression or enhancement from human plasma components was negligible under the optimized conditions. The proposed method can be applied in high-throughput analysis required for pharmacokinetic and bioequivalence studies in human samples.

Determination of sofosbuvir with two co-administered drugs; paracetamol and DL-methionine by two chromatographic methods. Application to a pharmacokinetic study

AIM

Two rapid and sensitive chromatographic methods have been developed and validated for simultaneous analysis of sofosbuvir (SOF) in rat plasma with two co-administered drugs, paracetamol (PAR) and DL-methionine (MET).

MATERIALS & METHODS

The first method relied on using TLC-densitometry with a developing system consisted of chloroform: methanol: glacial acetic acid: formic acid in the ratio of 9.5: 1: 1.5: 0.5, by volume. The studied analytes and the internal standard naphazoline hydrochloride were scanned at 210 nm. The second method was HPLC method, whereas the analytes and the internal standard cinnarizine were separated on XTerra^® HPLC RP C18 column using gradient elution mode and a mobile phase consisted of methanol: 0.1% aqueous TEA at pH 3 adjusted with orthophosphoric acid at 210 nm.

RESULTS

The TLC-densitometry method showed linearity over concentration ranges of 160-3000 ng/band for SOF and PAR, 300-3000 ng/band for MET, but HPLC method was linear and validated over concentration ranges of 150-5000 ng/ml for SOF, 300-5000 ng/ml for both PAR and MET.

CONCLUSION

All validation parameters met the acceptance criteria according to US FDA guidelines. Pharmacokinetic study was successfully applied and proved the possibility of co-administration of SOF with PAR and MET.

Pharmacodynamic and pharmacokinetic evaluation of the combination of daclatasvir/sofosbuvir/ribavirin in the treatment of chronic hepatitis C

INTRODUCTION

The combination of daclatasvir (DCV), sofosbuvir (SOF), and ribavirin (RBV) is a direct-acting antiviral (DAA) regimen for the treatment of hepatitis C virus (HCV) infection. The inclusion of newer effective DAAs such as SOF and DCV with high efficacy and excellent tolerance introduced a new scenario in HCV infection therapy: high rates of sustained virological response (SVR), shorter therapies, less toxicity, and interferon-free treatments. This combination was approved for the treatment of HCV in treatment-naive or treatment-experienced patients with chronic HCV genotype 1 or 3 infection. Areas covered: This review summarizes the pharmacokinetics, pharmacodynamics, efficacy, and safety of DCV plus SOF and RBV therapy in the treatment of HCV infection. The topics include data regarding drug absorption, distribution, metabolism, excretion, and antiviral activity strategies, such as clinical dose selection and treatment duration. Expert opinion: This combination, taken orally with or without food, has an excellent pharmacokinetic and pharmacodynamic profile. DAC/SOF/RBV achieves very high rates of SVR in treatment-naive and treatment-experienced patients with chronic HCV infection, including difficult-to-treat patients such as those with compensated cirrhosis, post-transplant recurrence, or HIV-1 co-infection.

Sofosbuvir/Velpatasvir/Voxilaprevir: A Pan-Genotypic Direct-Acting Antiviral Combination for Hepatitis C

OBJECTIVES

To review the efficacy and safety of sofosbuvir/velpatasvir/voxilaprevir in the treatment of hepatitis C virus (HCV) infection.

DATA SOURCES

A literature search through PubMed was conducted (August 2010 to August 2017) using the terms GS-9857, voxilaprevir, and NS3/4A protease inhibitor.

STUDY SELECTION/DATA EXTRACTION

Studies of sofosbuvir/velpatasvir/voxilaprevir were identified.

DATA SYNTHESIS

Sofosbuvir/velpatasvir/voxilaprevir is indicated for adult patients with chronic HCV without cirrhosis or with compensated cirrhosis who have (1) genotype 1 through 6 and have previously been treated with an NS5A inhibitor or (2) genotype 1a or 3 and have previously been treated with sofosbuvir without an NS5A inhibitor. POLARIS-1 demonstrated that sofosbuvir/velpatasvir/voxilaprevir for 12 weeks was highly effective in patients with HCV genotype 1 through 6 who had prior exposure to an NS5A inhibitor. POLARIS-2 failed to demonstrate that sofosbuvir/velpatasvir/voxilaprevir for 8 weeks was noninferior to sofosbuvir/velpatasvir for 12 weeks in patients with HCV genotype 1 through 6 who had no prior exposure to direct-acting antivirals (DAAs). POLARIS-3 demonstrated that sofosbuvir/velpatasvir/voxilaprevir for 8 weeks was as effective as sofosbuvir/velpatasvir for 12 weeks in patients with HCV genotype 3 and compensated cirrhosis who had no prior exposure to DAAs. POLARIS-4 demonstrated that sofosbuvir/velpatasvir/voxilaprevir was as effective as sofosbuvir/velpatasvir for 12 weeks in patients with HCV genotype 1 through 3 who had prior exposure to DAAs but not an NS5A inhibitor. The most common adverse reactions were headache, fatigue, diarrhea, and nausea.

CONCLUSIONS

Sofosbuvir/velpatasvir/voxilaprevir is safe and effective to treat HCV in patients who have previously been treated with DAAs.

Ginsenoside Rg3 restores hepatitis C virus-induced aberrant mitochondrial dynamics and inhibits virus propagation

Hepatitis C virus (HCV) alters mitochondrial dynamics associated with persistent viral infection and suppression of innate immunity. Mitochondrial dysfunction is also a pathologic feature of direct-acting antiviral (DAA) treatment. Despite the high efficacy of DAAs, their use in treating patients with chronic hepatitis C in interferon-sparing regimens occasionally produces undesirable side effects such as fatigue, migraine, and other conditions, which may be linked to mitochondrial dysfunction. Here, we show that clinically prescribed DAAs, including sofosbuvir, affect mitochondrial dynamics. To counter these adverse effects, we examined HCV-induced and DAA-induced aberrant mitochondrial dynamics modulated by ginsenoside, which is known to support healthy mitochondrial physiology and the innate immune system. We screened several ginsenoside compounds showing antiviral activity using a robust HCV cell culture system. We investigated the role of ginsenosides in antiviral efficacy, alteration of mitochondrial transmembrane potential, abnormal mitochondrial fission, its upstream signaling, and mitophagic process caused by HCV infection or DAA treatment. Only one of the compounds, ginsenoside Rg3 (G-Rg3), exhibited notable and promising anti-HCV potential. Treatment of HCV-infected cells with G-Rg3 increased HCV core protein-mediated reduction in the expression level of cytosolic p21, required for increasing cyclin-dependent kinase 1 activity, which catalyzes Ser616 phosphorylation of dynamin-related protein 1. The HCV-induced mitophagy, which follows mitochondrial fission, was also rescued by G-Rg3 treatment.

CONCLUSION

G-Rg3 inhibits HCV propagation. Its antiviral mechanism involves restoring the HCV-induced dynamin-related protein 1-mediated aberrant mitochondrial fission process, thereby resulting in suppression of persistent HCV infection. (Hepatology 2017;66:758-771).

Validated spectrophotometric and chromatographic methods for analysis of the recently approved hepatitis C antiviral combination ledipasvir and sofosbuvir

This work describes five simple and reliable spectrophotometric and chromatographic methods for analysis of hepatitis C antiviral binary mixture of ledipasvir (LPV) and sofosbuvir (SBV). Method I is based on the use of A_max and derivative spectrophotometry with the zero-crossing technique where LPV was determined using its A_max and ¹D amplitudes at 324 and 338nm respectively, while SBV was determined by measuring the ¹D amplitudes at 276nm. Method II involves the application of the ratio spectra derivative spectrophotometry. For LPV, 12μg/mL SBV was used as divisor and the ¹DD amplitudes at 239.8nm were plotted against LPV concentrations; while by using 10μg/mL LPV, the amplitudes at 279.2nm were found proportional to SBV concentrations. Method III depends on ratio-difference measurement where the peak to trough amplitudes between 229.2 and 268.4nm were measured and correlated to LPV concentration. Similarly, the amplitudes between 268.6 and 229.2nm in the SBV ratio spectra were recorded. For method IV, the two compounds were separated using HPTLC sheets of silica gel and a mobile phase composed of chloroform-methanol (94:6) followed by densitometric measurement of LPV and SBV spots at 331 and 267nm respectively. Method V depends on HPLC-DAD. Effective chromatographic separation was achieved using Thermohypersil C8 column (4.6×250mm, 5μm) with a mobile phase consisting of 0.01M sodium dihydrogen phosphate (pH 2.5) and methanol (20:80) at a flow rate 1.2mL/min and detection at 332 and 262nm for LPV and SBV respectively. Analytical performance of the developed methods was validated according to the ICH guidelines with respect to linearity, ranges, precision, accuracy, detection and quantification limits. The validated methods were successfully applied to the simultaneous analysis of LPV and SBV in mixtures of different proportions and their combined tablet dosage form.

The unexpected structures of hepatitis C virus envelope proteins

Hepatitis C virus (HCV) envelope proteins are essential not only for maintaining the viral life cycle, but also for evading the host's immune response and in clinical intervention. A thorough understanding of HCV envelope proteins depends on the availability of detailed structural information. Two crystal structures of the E2 core portion and of the E2 ectodomain, and one structure of the N-terminus of E1 ectodomain have shed new light on the complexity of HCV envelope proteins. In addition, the full-length E1-E2 complex has recently been modeled. The present review focuses on these advancements, introduces the recently solved structures and their biological implications and proposes novel ideas for studying the full-length E1-E2 complex.

Effectiveness of ledipasvir/sofosbuvir in real-world patients with chronic hepatitis C: a collaborative treatment approach

The effectiveness of ledipasvir/sofosbuvir (LDV/SOF) in routine use in clinical practice for the management of chronic hepatitis C virus (HCV) has not been well described. Data with prior agents suggest that management of HCV using an interprofessional approach in clinical practice is associated with better outcomes. This single-centre, prospective, observational cohort study evaluated patients treated with LDV/SOF for 8, 12 or 24 weeks as part of the standardized interprofessional treatment protocol at Novant Health Infectious Diseases Specialists. Eighty-four patients treated with LDV/SOF were evaluated; of these, 97.5% and 91.7% of patients achieved a sustained virological response (SVR) in the per-protocol analysis and the intention-to-treat analysis, respectively. Two patients were not cured after relapse of HCV. No patients required LDV/SOF discontinuation and all patients completed the appropriate treatment duration. The majority (56%) of patients reported no adverse effects and all adverse effects that were reported were mild. The most commonly reported adverse effects were headache and fatigue. SVR and tolerability rates were similar to those seen in the clinical trials. LDV/SOF was associated with a successful translation from the clinical trial setting to clinical practice. A collaborative treatment approach should be considered in the management of HCV.

Pharmacokinetic drug evaluation of velpatasvir plus sofosbuvir for the treatment of hepatitis C virus infection

INTRODUCTION

The fixed-dose combination therapy of sofosbuvir (SOF) plus velpatasvir (VEL) is the first pangenotypic, direct-acting antiviral (DAA), single-treatment regimen (STR) for the treatment of hepatitis C virus (HCV) infection to be commercialized. It is approved for the treatment of HCV genotypes 1, 2, 3, 4, 5, and 6. Following approval in 2016, new pharmacokinetic and pharmacodynamic data were reported, which led to important clinical applications. Areas covered: This review provides a summary of the pharmacokinetics, pharmacodynamics, efficacy and safety of SOF/VEL therapy for treatment of HCV infection. The topics covered include data regarding the drug's absorption, distribution, metabolism, excretion and antiviral activity strategies, such as clinical dose selection and treatment duration. Expert opinion: This novel combination therapy containing 400 mg of SOF plus 100 mg of VEL, taken orally, once daily, with or without food, has an excellent pharmacokinetic and pharmacodynamic profile. SOF/VEL achieved very high rates of sustained virological response in treatment-naive and treatment-experienced patients with chronic HCV genotype 1-6 infection, including those with compensated cirrhosis or HIV-1 co-infection.

What is the role of sofosbuvir in treating hepatitis C infection?

Sofosbuvir, a nucleotide polymerase inhibitor, was approved in 2013 for treating hepatitis C infection in adults. This article reviews the use of sofosbuvir in combination with ribavirin with or without pegylated interferon.

Sofosbuvir/Velpatasvir: The First Pangenotypic Direct-Acting Antiviral Combination for Hepatitis C

OBJECTIVES

To review the pharmacology, efficacy, and safety of sofosbuvir/velpatasvir in the treatment of patients with hepatitis C virus (HCV) infection.

DATA SOURCES

A literature search through PubMed was conducted (June 2008 to August 2016) using the terms GS-5816, velpatasvir, and sofosbuvir. References from retrieved articles and the prescribing information were reviewed for any additional material.

STUDY SELECTION/DATA EXTRACTION

The literature search was limited to human studies published in English. Phase I, II, and III studies of sofosbuvir/velpatasvir for HCV were identified.

DATA SYNTHESIS

Sofosbuvir/velpatasvir is indicated for adult patients with chronic HCV genotype 1 through 6. It is given without ribavirin in patients with or without compensated cirrhosis and with ribavirin in patients who have decompensated cirrhosis. The ASTRAL-1 study demonstrated that sofosbuvir 400 mg plus velpatasvir 100 mg for 12 weeks was effective at achieving high sustained virological response (SVR₁₂) rates in patients with HCV genotype 1, 2, 4, 5, or 6. The ASTRAL-2 and ASTRAL-3 studies demonstrated that the same regimen was effective at achieving high SVR₁₂ rates in patients with HCV genotype 2 or 3. The ASTRAL-4 study demonstrated that the same regimen plus ribavirin was effective at achieving high SVR₁₂ rate in patients with decompensated cirrhosis. The most common adverse reactions (≥10% of patients) associated with sofosbuvir/velpatasvir were headache and fatigue.

CONCLUSIONS

Sofosbuvir/velpatasvir is safe and effective to treat HCV genotypes 1, 2, 3, 4, 5, and 6 in patients with or without compensated cirrhosis. The addition of ribavirin is recommended in patients with decompensated cirrhosis.

Curing the historically incurable: treatment success with ledipasvir/sofosbuvir for chronic hepatitis C virus in a heavily treatment-experienced individual

WHAT IS KNOWN AND OBJECTIVE

Significant progression in the treatment of chronic hepatitis C virus has been made with the introduction of direct-acting antivirals (DAAs). However, limited data are available for the retreatment of individuals who have failed multiple prior DAAs.

CASE DESCRIPTION

We report a single case of an individual who was unsuccessfully treated with five prior hepatitis C virus treatment regimens including simeprevir plus sofosbuvir who was successfully cured after treatment with ledipasvir/sofosbuvir.

WHAT IS NEW AND CONCLUSION

Ledipasvir/sofosbuvir may be an option for treating patients who have failed multiple prior DAA regimens; however, further research is warranted.

Interferon-Free Treatments for Chronic Hepatitis C Genotype 1 Infection

Hepatitis C virus (HCV) infection affects as many as 185 million people globally, many of whom are chronically infected and progress over time to cirrhosis, decompensated liver disease, hepatocellular carcinoma, and eventually death without a liver transplant. In the United States, HCV genotype 1 constitutes about 75% of all infections. While interferon and ribavirin therapy was the cornerstone of treatment for many years, interferon-free treatments have become the standard of care with the emergence of new direct-acting agents, resulting in more effective treatment, shorter duration of therapy, better tolerability, lower pill burden, and ultimately better adherence. This review will summarize the evidence for the currently available combination therapies as well as emerging therapies in phase 3 trials for treatment of HCV genotype 1.

Daclatasvir: A NS5A Replication Complex Inhibitor for Hepatitis C Infection

OBJECTIVES

To review the pharmacology, efficacy, and safety of daclatasvir in the treatment of patients with chronic hepatitis C virus (HCV) infection.

DATA SOURCES

A literature search through EMBASE and PubMed was conducted (January 1966 to August 2015) using the terms BMS-790052, daclatasvir, and hepatitis C. References from retrieved articles were reviewed for any additional material. Additionally, the new drug application and prescribing information were retrieved.

STUDY SELECTION/DATA EXTRACTION

The literature search was limited to human studies published in English. Phase 1, 2, and 3 studies describing the pharmacology, pharmacokinetics, efficacy, and safety of daclatasvir for HCV were identified.

DATA SYNTHESIS

Daclatasvir, a nonstructural 5A protein inhibitor, combined with sofosbuvir, is indicated for adult patients with chronic HCV genotype 3 regardless of treatment or cirrhosis status. The phase III ALLY-3 trial (n = 152) demonstrated that daclatasvir taken once daily with sofosbuvir for 12 weeks was effective at achieving sustained virological response (SVR) rates in treatment-naïve (97%) and treatment-experienced (94%) patients without cirrhosis. Patients with cirrhosis had significantly lower SVR rates (58 and 69%, respectively). The most common adverse drug events associated with daclatasvir and sofosbuvir in ALLY-3 were headache (20%), fatigue (19%), and nausea (12%).

CONCLUSIONS

Daclatasvir, when combined with sofosbuvir, is an effective agent to treat HCV genotype 3, with SVR rates above 90% for patients without cirrhosis who are treatment naïve or experienced. SVR rates for treatment-naïve or -experienced patients with cirrhosis are not as robust (58%-69%).

Evaluation of a rapid method for the simultaneous quantification of ribavirin, sofosbuvir and its metabolite in rat plasma by UPLC-MS/MS

A rapid and sensitive ultra performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method for the determination of ribavirin, sofosbuvir and its metabolite GS-331007 in rat plasma was established. The analytes and the internal standard (midazolam) were separated on an Acquity UPLC BEH C18 chromatography column (2.1mm×50mm, 1.7μm) using gradient elution with a mobile phase of acetonitrile and 0.1% formic acid in water at a flow rate of 0.4mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode to monitor the precursor-to-product ion transitions of m/z 245.1→113.1 for ribavirin, m/z 530.3→243.1 for sofosbuvir, m/z 261.5→113.1 for GS-331007 and m/z 326.2→291.1 for midazolam (IS) using a positive electrospray ionization interface. The method was validated over a concentration range of 5-1000ng/mL for ribavirin, 10-2000ng/mL for sofosbuvir and 10-2000ng/mL for GS-331007. Total time for each chromatograph was 3.0min. The intra- and inter-day precision and accuracy of the quality control samples at low, medium, and high concentration levels exhibited relative standard deviations (RSD) <10.0% and the accuracy values ranged from -10.6% to 11.6%. The method was successfully applied to a pharmacokinetic study of ribavirin, sofosbuvir and GS-331007 in rats.

Drug Authorization for Sofosbuvir/Ledipasvir (Harvoni) for Chronic HCV Infection in a Real-World Cohort: A New Barrier in the HCV Care Cascade

BACKGROUND

New treatments for hepatitis C (HCV) infection hold great promise for cure, but numerous challenges to diagnosing, establishing care, and receiving therapy exist. There are limited data on insurance authorization for these medications.

MATERIALS AND METHODS

We performed a retrospective chart review of patients receiving sofosbuvir/ledipasvir (SOF/LED) from October 11-December 31, 2014 to determine rates and timing of drug authorization. We also determined predictors of approval, and those factors associated with faster decision and approval times.

RESULTS

Of 174 patients prescribed HCV therapy during this period, 129 requests were made for SOF/LED, of whom 100 (77.5%) received initial approval, and an additional 17 patients (13.9%) ultimately received approval through the appeals process. Faster approval times were seen in patients with Child-Pugh Class B disease (14.4 vs. 24.7 days, p = 0.048). A higher proportion of patients were initially approved in those with Medicare/Medicaid coverage (92.2% vs. 71.4%, p = 0.002) and those with baseline viral load ≥ 6 million IU/mL (84.1% vs. 62.5%, p = 0.040). Linear regression modeling identified advanced fibrosis, high Model of End Stage Liver Disease (MELD) score, and female gender as significant predictors of shorter decision and approval times. On logistic regression, Medicare/Medicaid coverage (OR 5.96, 95% CI 1.66-21.48) and high viral load (OR 4.52, 95% CI 1.08-19.08) were significant predictors for initial approval.

CONCLUSIONS

Early analysis of real-world drug authorization outcomes between October-December 2014 reveals that nearly one in four patients are initially denied access to SOF/LED upon initial prescription, although most patients are eventually approved through appeal, which delays treatment initiation. Having Medicare/Medicaid and advanced liver disease resulted in a higher likelihood of approval as well as earlier decision and approval times. More studies are needed to determine factors resulting in higher likelihood of denial and to evaluate approval rates and times after implementation of restrictive prior authorization guidelines.

Safety analysis of sofosbuvir and ledipasvir for treating hepatitis C

INTRODUCTION

The approval of sofosbuvir (SOF), a nucleotide analogue NS5B polymerase inhibitor, and ledipasvir (LDV), a NS5A inhibitor, marked a new chapter in IFN and ribavirin-free treatment of hepatitis C virus (HCV). This drug reduces adverse events associated with IFN therapy.

AREAS COVERED

The purpose of this paper is to evaluate the safety and efficacy of LDV/SOF. Clinical trials illustrating safety and efficacy of LDV/SOF are reviewed and compared to other IFN and ribavirin-free treatment options available.

EXPERT OPINION

In trials enrolling more than 3000 patients, LDV/SOF is well tolerated with a good safety and side-effect profile in diverse cohorts, including previous direct-acting antiviral (DAA) treatment failures, liver transplant recipients, decompensated cirrhosis and HIV/HCV co-infection. As with all DAAs, the potential for drug-drug interactions must be carefully evaluated, as demonstrated by recent post-marketing reports of symptomatic bradycardia when LDV/SOF is co-administered with amiodarone. Currently, dose recommendations cannot be given for patients with advanced renal disease. Trials in this population are ongoing, more study is warranted. When surveying the DAA regimens available, efficacy, safety and tolerability of LDV/SOF is comparable or better, and LDV/SOF provides an option with convenient single-tablet, once daily, ribavirin-free dosing with relatively few significant drug-drug interactions.

HIV and HCV Medications in End-Stage Renal Disease

Human immunodeficiency virus (HIV) infection and hepatitis C virus (HCV) infection affect populations worldwide. With the availability of over 35 Food and Drug Administration approved medications for treatment of HIV, the morbidity and mortality associated with HIV has greatly improved. On the other hand, treatment options for HCV have been limited until very recently. While the use of protease inhibitors (such as boceprevir and telaprevir) has become standard of care for treatment of hepatitis C in the general population, data for individuals with impaired kidney function, particularly those on dialysis, are extremely limited. Use of medications in dialysis patients can be challenging given the dose adjustments that must be made for renally cleared molecules, and potentially increased impact of adverse effects such as anemia. Recommendations for dosing of marketed therapies for HIV and HCV are reviewed.

Drug Interactions With Direct-Acting Antivirals for Hepatitis C: Implications for HIV and Transplant Patients

OBJECTIVE

Review pharmacokinetics of new direct-acting antivirals (DAAs) for hepatitis C (HCV) infection and interactions with concomitant immunosuppressant and antiretroviral therapies (ART).

DATA SOURCES

MEDLINE (1948-January 2015), EMBASE (1964-January 2015), International Pharmaceutical Abstracts (1970-January 2015), Google, and Google Scholar were searched combining the terms simeprevir, sofosbuvir, ledipasvir, daclatasvir, paritaprevir, ABT-450, ombitasvir, dasabuvir, pharmacokinetics, drug interaction, drug metabolism, HIV, antiretroviral, immunosuppressant, transplant. Articles, conference proceedings, abstracts, and product monographs were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Literature on pharmacokinetic or pharmacodynamic interactions with DAAs and immunosuppressants or ART was considered for inclusion. Pertinent information was extracted and summarized in the review. In the absence of data, pharmacokinetic and pharmacodynamic principles were used to predict the likelihood of interactions.

DATA SYNTHESIS

DAA pharmacokinetics are reviewed and drug interaction data are presented with provision of management strategies. Fixed-dose combination paritaprevir/ritonavir/ombitasvir plus dasabuvir is most susceptible to drug interactions with immunosuppressants and ART mainly due to the influence of ritonavir on multiple enzymes. Simeprevir is also prone to drug interactions because of cytochrome P450(CYP) 3A4, CYP1A2, P-glycoprotein, and OATP1 involvement and is not recommended for use in combination with several HIV antiretrovirals (ARVs). Close therapeutic drug monitoring of calcineurin inhibitors is required with concomitant simeprevir. Few clinically significant interactions are expected with sofosbuvir or ledipasvir. Limited data suggest that daclatasvir may be coadministered with immunosuppressants but requires dose adjustments with certain ARVs.

CONCLUSIONS

None of the DAAs are completely free of drug interactions. Awareness and management of drug interactions is critical to optimize outcomes and minimize adverse effects in these patient populations.

Dasabuvir : a new direct antiviral agent for the treatment of hepatitis C

INTRODUCTION

Treatment of hepatitis C virus (HCV) infection with direct-acting antivirals (DAAs) has revolutionized the care of infected patients. Among these novel compounds are non-nucleoside analogs, which bind viral RNA-dependent RNA polymerase resulting in a conformational change inhibiting RNA synthesis.

AREAS COVERED

Efficacy and tolerability of treatment regimens containing the non-nucleoside analog polymerase inhibitor dasabuvir (ABT-333).

EXPERT OPINION

Dasabuvir-containing regimens achieve high rates of sustained virologic response in HCV genotype 1a and 1b-infected patients when combined with other DAAs, namely paritaprevir (ABT-450), ritonavir and ombitasvir (ABT-267). In the populations studied, dasabuvir seems to be well tolerated and safe. The major limitations of this novel drug are its genotype-restricted activity, the necessity to include ribavirin for HCV genotype 1a and the emergence of resistance if not combined with other DDAs.

Fixed-dose combination of sofosbuvir and ledipasvir for the treatment of chronic hepatitis C genotype 1

INTRODUCTION

The recent October 2014 approval of the fixed dose combination (FDC) of the NS5B polymerase inhibitor sofosbuvir (SOF) and the NS5A inhibitor ledipasvir (LDV) for the treatment of treatment-naive and -experienced HCV genotype 1a/1b (HCV-1) has marked a new era of IFN and ribavirin free treatment for chronic hepatitis C. SOF/LDV combination is approved for 12 weeks in treatment-naive patients with and without cirrhosis. For treatment-experienced patients, it is approved for 12 weeks in patients without cirrhosis but for 24 weeks in patients with cirrhosis. A shorter 8-week course of treatment can be considered for treatment-naive patients who have pretreatment HCV RNA of < 6 million IU/ml and do not have cirrhosis.

AREAS COVERED

The purpose of this synopsis is to review the pharmacotherapy and results of pivotal clinical trials for SOF/LDV as the current standard-of-care for HCV-1 patients. We also briefly discuss emerging data with SOF/LDV for certain special populations. Preliminary data is also emerging for HCV genotypes non-1, but their discussion is beyond the scope of this synopsis. The review was done based on data from Phase I, II and III published studies as well as data presented at major national and international meetings.

EXPERT OPINION

The FDC of LDV (90 mg) and SOF (400 mg) has a sustained virologic response of approximately 96% when given as a once-a-day pill for 3 months to both treatment-naive and -experienced HCV-1 patients with the exception of prior null responders with cirrhosis. The latter group of patients also achieves high sustained virologic response of 95% but with therapy for 24 weeks. In addition, emerging data suggest that this FDC regimen may be effective in the treatment of HCV-1 co-infected patients with HIV, HCV-1 and -4, patients with cirrhosis and hepatic decompensation and those with post-liver transplant HCV recurrence.

Assessing safety and efficacy of sofosbuvir for the treatment of hepatitis C

INTRODUCTION

IFN-free regimens with direct antiviral agents (DAAs) against hepatitis C virus (HCV) are likely to greatly expand patients' access and response to hepatitis C therapy, while safety and tolerability of treatments seem substantially improved. Sofosbuvir (SOF), a NS5B nucleotide polymerase inhibitor with pan-genotypic activity and a high-barrier to resistance, has been approved by FDA and EMA in an all oral combination therapy for chronic hepatitis C with ribavirin (RBV) alone, or in combination with either pegylated interferon/RBV or other DAAs.

AREAS COVERED

This paper provides an overview of SOF-based therapy in chronic hepatitis C as it emerges from the published clinical trials. Data on special populations are included (i.e., decompensated patients, patients on liver transplant waiting lists, patients with renal impairment). The data has been analyzed according to the different HCV-genotypes and comprehensively covers both safety and efficacy treatment profiles.

EXPERT OPINION

Clinical trials have highlighted the safety and efficacy of SOF-based regimens, leading to the rapid approval of this therapy and its incorporation in the recommendations of the international societies on treatment of HCV infection. However, additional data are still needed to optimize both combination therapies' efficacy and duration in some categories of patients who have been under-represented in the registration trials.

Ledipasvir-sofosbuvir: interferon-/ribavirin-free regimen for chronic hepatitis C virus infection

OBJECTIVES

To review the pharmacology, efficacy, and safety of ledipasvir-sofosbuvir for the treatment of chronic hepatitis C virus (HCV).

DATA SOURCES

A literature search through clinicaltrials.gov, EMBASE, and PubMed was conducted (January 1966 to October 2014) using the terms ledipasvir, sofosbuvir, GS-5885, and GS-7977. References from retrieved articles and abstracts presented at recent meetings were reviewed for any additional material. The prescribing information was also reviewed.

STUDY SELECTION/DATA EXTRACTION

Phase 1, 2, and 3 human and animal studies describing the pharmacology, pharmacokinetics, efficacy, and safety of ledipasvir and sofosbuvir for HCV were identified.

DATA SYNTHESIS

Ledipasvir-sofosbuvir, a fixed-dose combination (FDC) tablet inhibiting nonstructural (NS) 5A and 5B proteins, without peginterferon and ribavirin is indicated for adult patients with genotype 1 HCV infection who are treatment naïve or experienced, with or without cirrhosis. Pivotal trials (n = 1952) have demonstrated that once-daily administration of ledipasvir-sofosbuvir for 12 or 24 weeks is effective at achieving sustained virological response (SVR) rates (94%-99%) in treatment-naïve patients (12 weeks), treatment-experienced patients without cirrhosis (12 weeks), and treatment-experienced patients with cirrhosis (24 weeks). Treatment-naïve patients without cirrhosis and baseline viral levels of less than 6 million IU/mL may be considered for 8 weeks of treatment. The most common adverse drug events (ADEs) associated with ledipasvir-sofosbuvir include headache, fatigue, insomnia, nausea, and diarrhea.

CONCLUSIONS

Ledipasvir-sofosbuvir is the first interferon- and ribavirin-free FDC agent that has SVR rates much greater than 94%, with minimal ADEs, for the treatment of chronic HCV genotype 1 in naïve and treatment-experienced patients.

HCV E2 core structures and mAbs: something is still missing

The lack of structural information on hepatitis C virus (HCV) surface proteins has so far hampered the development of effective vaccines. Recently, two crystallographic structures have described the core portion (E2c) of E2 surface glycoprotein, the primary mediator of HCV entry. Despite the importance of these studies, the E2 overall structure is still unknown and, most importantly, several biochemical and functional studies are in disagreement with E2c structures. Here, the main literature will be discussed and an alternative disulfide bridge pattern will be proposed, based on unpublished human monoclonal antibody reactivity. A modeling strategy aiming at recapitulating the available structural and functional studies of E2 will also be proposed.