NS5A inhibitor, daclatasvir, for the treatment of chronic hepatitis C virus infection

Therapeutic Intervention of Serine Protease Inhibitors against Hepatitis C Virus

Hepatitis C virus (HCV) is a globally prevalent and hazardous disorder that is responsible for inducing several persistent and potentially fatal liver diseases. Current treatment strategies offer limited efficacy, often accompanied by severe and debilitating adverse effects. Consequently, there is an urgent and compelling need to develop novel therapeutic interventions that can provide maximum efficacy in combating HCV while minimizing the burden of adverse effects on patients. One promising target against HCV is the NS3-4A serine protease, a complex composed of two HCV-encoded proteins. This non-covalent heterodimer is crucial in the viral life cycle and has become a primary focus for therapeutic interventions. Although peginterferon, combined with ribavirin, is commonly employed for HCV treatment, its efficacy is hampered by significant adverse effects that can profoundly impact patients' quality of life. In recent years, the development of direct-acting antiviral agents (DAAs) has emerged as a breakthrough in HCV therapy. These agents exhibit remarkable potency against the virus and have demonstrated fewer adverse effects when combined with other DAAs. However, it is important to note that there is a potential for developing resistance to DAAs due to alterations in the amino acid position of the NS3-4A protease. This emphasizes the need for ongoing research to identify strategies that can minimize the emergence of resistance and ensure long-term effectiveness. While the combination of DAAs holds promise for HCV treatment, it is crucial to consider the possibility of drug-drug interactions. These interactions may occur when different DAAs are used concurrently, potentially compromising their therapeutic efficacy. Therefore, carefully evaluating and monitoring potential drug interactions are vital to optimize treatment outcomes. In the pursuit of novel therapeutic interventions for HCV, the field of computational biology and bioinformatics has emerged as a valuable tool. These advanced technologies and methodologies enable the development and design of new drugs and therapeutic agents that exhibit maximum efficacy, reduced risk of resistance, and minimal adverse effects. By leveraging computational approaches, researchers can efficiently screen and optimize potential candidates, accelerating the discovery and development of highly effective treatments for HCV, treatments.

Molecular Mechanisms of Resistance to Direct-Acting Antiviral (DAA) Drugs for the Treatment of Hepatitis C Virus Infections

Hepatitis C virus (HCV) is a hepatotropic virus that affects millions of human lives worldwide. Direct-acting antiviral (DAA) regimens are the most effective HCV treatment option. However, amino acid substitution-dependent resistance to DAAs has been a major challenge. This study aimed to determine the increasing risk of DAA resistance due to substitutions in DAA target non-structural proteins (NS3/4A, NS5A, and NS5B). Using a Sequence Retrieval System (SRS) at the virus pathogen resource (ViPR/BV-BRC), n = 32763 target protein sequences were retrieved and analyzed for resistance-associated amino acid substitutions (RAASs) by the Sequence Feature Variant Type (SFVT) antiviral-resistance assessment modeling tool. Reference target protein sequences with 100% identity were retried from UniProt following NCBI BLAST. The types and locations of RAASs were identified and visualized by AlphaFold and PyMol. Linux-r-base/R-studio was used for the data presentation. Multi-drug-resistant variants of NS3/4A in genotype 1 (n = 9) and genotype 5 (n = 5) along with DAA-specific NS3/4A, NS5A, and NS5B variants were identified pan-genotypically. A total of 27 variants (RAASs) of all the targets were identified. Fourteen genotype 1-specific substitutions: V1196A, V1158I, D1194A/T/G, R1181K, T1080S, Q1106R, V1062A, S1148G, A1182V, Y2065N, M2000T, and L2003V were identified. The most frequent substitutions were V1062L and L2003M, followed by Q2002H. L2003V, Q2002H, M2000T, Y2065N, and NL2003M of NS5A and L2003M of NS5B conferred resistance to daclatasvir. S2702T NS5B was the sofosbuvir-resistant variant. D1194A NS3/4A was triple DAA (simeprevir, faldaprevir, and asunaprevir) resistant. The double-drug resistant variants R1181K (faldaprevir and asunaprevir), A1182V and Q1106K/R (faldaprevir and simeprevir), T1080S (faldaprevir and telaprevir), and single drug-resistant variants V1062L (telaprevir), D1194E/T (simeprevir), D1194G (asunaprevir), S1148A/G (simeprevir), and Q1106L (Boceprevir) of NS3/4A were determined. The molecular phenomenon of DAA resistance is paramount in the development of HCV drug candidates. RAASs in NS3, NS5A, and NS5B reduce the susceptibility to DAAs; therefore, continuous RAAS-dependent resistance profiling in HCV is recommended to minimize the probability of DAA therapeutic failure.

Three Smart and Original Spectrophotometric Data Processing Ratio Techniques for Resolving the Partial Overlapped Spectra of the Binary Antiviral Mixture Daclatasvir/Sofosbuvir: Application to Combined Dosage Form Darvoni® Tablets

BACKGROUND

The combination of Daclatasvir (DCV) and sofosbuvir (SFV) is now widely used as an ideal treatment for hepatitis C virus infection. For this purpose, simple, sensitive, rapid and smart spectrophotometric methods were developed and validated for the determination of these drugs in their combined dosage form.

OBJECTIVE

Development οf smart, sensitive, cheap spectrοphοtοmetric methοds fοr determinatiοn (DCV) and (SFV) in their combined dosage.

METHODS

Ratio subtraction (RS) and amplitude modulation (AM) and mean centering spectrophotometric methods were established and validated for the estimation of sofosbuvir (SFV) in existence of daclatasvir without previous separation, utilizing unified regression equation.

RESULTS

A linearity limit of 2.5-25.0 µg/mL was confirmed for the direct measurement of daclatasvir at 316 nm (because there is no interference from sofosbuvir). Linearity was confirmed over a concentration limit of 10.0-80.0 µg/mL for sofosbuvir. The current methods were established as stated by the ICH recommendations and by testing synthetic mixtures of both drugs, the specificity was examined. They were tested on their tablet dosage form and good recovery was obtained.

CONCLUSIONS

The current methods were tested on their tablet dosage form and good recovery was obtained. A statistical study has been established among the current ratio approaches and a published methods and there was no apparent statistical variation was obtained.

HIGHLIGHTS

Both antiviral agents can be quantified in existence of each other by the current methods, which is a great time and cost-saving valor of the developed methods. This valor is even more important in the case of the combined dosage form (Darvoni® tablets) to the pharmaceutical market.

Additional Inhibition of Wnt/β-Catenin Signaling by Metformin in DAA Treatments as a Novel Therapeutic Strategy for HCV-Infected Patients

Chronic hepatitis C virus (HCV) infection causes hepatocellular carcinoma (HCC). Although HCV clearance has been improved by the advent of direct-acting antiviral agents (DAA), retrospective studies have shown that the risk of subsequent HCC, while considerably decreased compared with active HCV infection, persists after DAA regimens. However, either the mechanisms of how chronic HCV infection causes HCC or the factors responsible for HCC development after viral eradication in patients with DAA treatments remain elusive. We reported an in vitro model of chronic HCV infection and determined Wnt/β-catenin signaling activation due to the inhibition of GSK-3β activity via serine 9 phosphorylation (p-ser9-GSK-3β) leading to stable non-phosphorylated β-catenin. Immunohistochemical staining demonstrated the upregulation of both β-catenin and p-Ser9-GSK-3β in HCV-induced HCC tissues. Chronic HCV infection increased proliferation and colony-forming ability, but knockdown of β-catenin decreased proliferation and increased apoptosis. Unexpectedly, Wnt/β-catenin signaling remained activated in chronic HCV-infected cells after HCV eradication by DAA, but metformin reversed it through PKA/GSK-3β-mediated β-catenin degradation, inhibited colony-forming ability and proliferation, and increased apoptosis, suggesting that DAA therapy in combination with metformin may be a novel therapy to treat HCV-associated HCC where metformin suppresses Wnt/β-catenin signaling for HCV-infected patients.

Paediatric hepatitis C virus infection and its treatment: Present, past, and future

Hepatitis C virus (HCV) infection is a major cause of chronic liver disease in the world. It is a challenging medico-social problem in the paediatric population. High HCV infection rates are reported in low and middle incomes countries. From the health economic point of view treatment of hepatitis C virus (HCV) with subsequent virus eradication is very effective as it eliminates the long-term sequelae of untreated or maltreated HCV. In this review we summarize the updates and highlight the historical approach of treatment of chronic HCV infection in children in the new era of directly acting antiviral (DAA) agents.

A Stability-Indicating UPLC Method for the Determination of Potential Impurities and Its Mass by a New QDa Mass Detector in Daclatasvir Drug Used to Treat Hepatitis C Infection

A stability-indicating ultraperformance liquid chromatographic method has been developed for the quantitative determination of degradation products and process-related impurities of daclatasvir in a pharmaceutical dosage form. Chromatographic separation was achieved on a polar Waters ACQUITY BEH phenyl 100 × 2.1 mm, 1.7-μm column using the gradient program consisting of mobile phase A: 0.03 M sodium perchlorate with 0.002 M of 1-octanesulfonic acid sodium salt (pH 2.5 buffer) and mobile phase B: 0.03 M sodium perchlorate with 0.02 M of 1-octanesulfonic acid sodium salt (pH 2.5 buffer) with acetonitrile in the ratio of 20:80% v/v. A flow rate of 0.4 mL/min is maintained under ultraviolet detection at 305 nm. The run time was 15 min, within which daclatasvir, its related impurities and unknown degradants were well resolved. The method was found to produce symmetric and sharp peaks with good separation between process-related impurities and degradation impurities. Samples were subjected to hydrolysis (acid and base), oxidative, photolytic and thermal stress conditions to prove the stability-indicating nature of the method. The unknown degradation products were identified by PDA/QDa mass detector. This mass spectrum reveals protonated molecular ion peaks [M + H]+ at m/z DP1-582.4 in acid and base hydrolyses and m/z DP2-778.5 in peroxide hydrolysis. The method was validated in terms of specificity, precision, linearity, accuracy, limit of detection, limit of quantification and robustness as per ICH guidelines.

Comparative study of six sequential spectrophotometric methods for quantification and separation of ribavirin, sofosbuvir and daclatasvir: An application on Laboratory prepared mixture, pharmaceutical preparations, spiked human urine, spiked human plasma, and dissolution test

In accordance with International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines, six novel, simple and precise sequential spectrophotometric methods were developed and validated for the simultaneous analysis of Ribavirin (RIB), Sofosbuvir (SOF), and Daclatasvir (DAC) in their mixture without prior separation steps. These drugs are described as co-administered for treatment of Hepatitis C virus (HCV). HCV is the cause of hepatitis C and some cancers such as liver cancer (hepatocellular carcinoma) and lymphomas in humans. These techniques consisted of several sequential steps using zero, ratio and/or derivative spectra. DAC was first determined through direct spectrophotometry at 313.7 nm without any interference of the other two drugs while RIB and SOF can be determined after ratio subtraction through five methods; Ratio difference spectrophotometric method, successive derivative ratio method, constant center, isoabsorptive method at 238.8 nm, and mean centering of the ratio spectra (MCR) at 224 nm and 258 nm for RIB and SOF, respectively. The calibration curve is linear over the concentration ranges of (6-42), (10-70) and (4-16) μg/mL for RIB, SOF, and DAC, respectively. This method was successfully applied to commercial pharmaceutical preparation of the drugs, spiked human urine, and spiked human plasma. The above methods are very simple methods that were developed for the simultaneous determination of binary and ternary mixtures and so enhance signal-to-noise ratio. The method has been successfully applied to the simultaneous analysis of RIB, SOF, and DAC in laboratory prepared mixtures. The obtained results are statistically compared with those obtained by the official or reported methods, showing no significant difference with respect to accuracy and precision at p = 0.05.

Long-term follow-up of clinical trial patients treated for chronic HCV infection with daclatasvir-based regimens

BACKGROUND & AIMS

Daclatasvir has achieved high sustained virologic response (SVR) rates in diverse hepatitis C virus (HCV) populations. This study evaluated the long-term efficacy and safety of daclatasvir-based regimens administered during clinical studies.

METHODS

Patients enrolled within 6 months of parent study completion or protocol availability at the study sites. The primary objective was durability of SVR at follow-up Week 12 (SVR12). Secondary objectives included analysing HCV sequences in non-responders or responders who relapsed, and characterization of liver disease progression.

RESULTS

Between 24 February 2012 and 17 July 2015, this study enrolled and began following 1503 recipients of daclatasvir-based regimens (follow-up cut-off, 13 October 2015); 60% were male, 18% aged ≥65 years, 87% had genotype-1a (42%) or -1b (45%) infection, and 18% had cirrhosis. Median follow-up from parent study follow-up Week 12 was 111 (range, 11-246) weeks. 1329/1489 evaluable patients were SVR12 responders; 1316/1329 maintained SVR until their latest visit. Twelve responders relapsed by (n = 9) or after (n = 3) parent study follow-up Week 24; one was reinfected. Relapse occurred in 3/842 (0.4%) and 9/487 (2%) responders treated with interferon-free or interferon-containing regimens, respectively. Hepatic disease progression and new hepatocellular carcinoma were diagnosed in 15 and 23 patients, respectively. Among non-responders, emergent non-structural protein-5A (NS5A) and -3 (NS3) substitutions were replaced by wild-type sequences in 27/157 (17%) and 35/47 (74%) patients, respectively.

CONCLUSIONS

SVR12 was durable in 99% of recipients of daclatasvir-based regimens. Hepatic disease progression and new hepatocellular carcinoma were infrequent. Emergent NS5A substitutions persisted longer than NS3 substitutions among non-responders.

Investigation of anti-Hepatitis C virus, sofosbuvir and daclatasvir, in pure form, human plasma and human urine using micellar monolithic HPLC-UV method and application to pharmacokinetic study

Simultaneous determination of sofosbuvir (SOF), and daclatasvir (DAC) in their dosage forms, human urine and human plasma using simple and rapid micellar high performance liquid chromatographic method coupled with UV detection (HPLC-UV) had been developed and validated. These drugs are described as co-administered for treatment of Hepatitis C virus (HCV). HCV is the cause of Hepatitis C and some cancers such as liver cancer (hepatocellular carcinoma) and lymphomas in humans. Separation and quantitation were carried out on anonyx™ C₈ monolithic (100 × 4.6 mm (i.d.) analytical column maintained at 25 °C. The mobile phase consisted of 0.1 M sodium dodecyl sulfate (SDS) solution containing 20% (V/V) n-propanolol and 0.3% (V/V) triethylamine and pH was adjusted to 6.5 using 0.02 M phosphoric acid, respectively. The retention times of SOF and DAC were 4.8 min, and 6.5 min, respectively. Measurements were made at flow rate of 0.5 mL/min with injection volume of 20 μL and ultraviolet (UV) detection at 226 nm. Linearity of SOF and DAC was obtained over concentration ranges of 50-400, and 40-400 ng/mL, respectively in pure form, 60-300 and 50-300 ng/mL, respectively for human plasma and over 50-400, and 40-400 ng/mL, respectively for human urine with correlation coefficient >0.999. The proposed method demonstrated excellent intra- and inter-day precision and accuracy. The suggested method was applied for determination of the drugs in pure, dosage form, and in real human plasma, real human urine and drug-dissolution test of their tablets. The obtained results have been statistically compared to reported method to give a conclusion that there is no significant differences.

Fibrosing Cholestatic Hepatitis C After Liver Transplantation: Therapeutic Options Before and After Introduction of Direct-Acting Antivirals: Our Experience and Literature Review

BACKGROUND

Cirrhosis caused by hepatitis C is the most common indication for liver transplantation. The most aggressive form of hepatitis C virus (HCV) relapse after liver transplantation is fibrosing cholestatic hepatitis C, which can be observed in 2% to 15% of recipients.

METHODS

Double therapy with peg-interferon and ribavirin was characterized by low antiviral response, rapid fibrosis, and frequent graft failure within 1 year after surgery.

RESULTS

Introduction of direct-acting antivirals for HCV treatment allows for more efficient therapy with less adverse reactions, including patients with fibrosing cholestatic hepatitis C.

CONCLUSIONS

We present 4 (2.5%) cases of cholestatic viral hepatitis C recurrence in patients undergoing transplantation between 2006 and 2015 at the Transplantation Institute of Warsaw; during this period, 158 liver transplants were performed in patients with cirrhosis caused by HCV infection.

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.

Dual daclatasvir and sofosbuvir for treatment of genotype 3 chronic hepatitis C virus infection

Chronic hepatitis C virus (HCV) infection is one of the most common etiologies of liver-related mortality throughout the world. Traditionally, therapy has been focused on pegylated interferon in combination with ribavirin, with clinical trials demonstrating that HCV genotype 1 had the lowest response rate (40-50%), while genotype 3 had an intermediate response rate (60-70%). Recently, significant advances have been made with all-oral direct-acting antiviral (DAA) therapy, which have significantly improved cure rates for HCV genotype 1. Accordingly, HCV genotype 3 is now potentially the most difficult to treat. One of the most potent DAA medications is sofosbuvir, a pan-genotypic nucleotide analogue that inhibits the NS5B polymerase of HCV. Daclatasvir, a pan-genotypic inhibitor of the HCV NS5A replication complex, was recently approved in the United States for treatment of HCV genotype 3 in conjunction with sofosbuvir. This combination may provide a powerful tool in the treatment of HCV genotype 3.

Role of ledipasvir/sofosbuvir combination for genotype 1 hepatitis C virus infection

Chronic hepatitis C virus (HCV) infection is one of the most common etiologies of liver-related mortality throughout the world. Among the six HCV genotypes, genotype 1 was significantly more aggressive when utilizing the combination of pegylated interferon and ribavirin, as genotype 1-infected patients had the lowest likelihood of achieving cure (40%-50%) and required twice as long duration of treatment, as compared to genotypes 2 and 3. Recently, however, significant advances have been made with the advent of all-oral direct-acting antiviral agents, which have significantly improved the safety, efficacy, and tolerability of the treatment of HCV genotype 1. Among the available treatments for HCV genotype 1, the combination therapy of ledipasvir/sofosbuvir provides several advantages compared to other regimens, including use of a single-pill regimen, possibility to shorten the duration of treatment to 8 weeks, efficacy in patients exposed to protease inhibitors, safety in decompensated cirrhosis, and potential to avoid ribavirin. In this review, we discuss the pharmacotherapy of the combination of ledipasvir/sofosbuvir therapy and summarize the results of the Phase III clinical trials for this treatment in HCV genotype 1 patients. We will also discuss the data for special populations, including decompensated cirrhosis, human immunodeficiency virus (HIV) coinfected patients, African-Americans, the elderly, and those who failed sofosbuvir-containing regimens.

Hepatitis C virus genotype 3: Meta-analysis on sustained virologic response rates with currently available treatment options

AIM: To address the therapeutic efficacy of various treatment regimens in genotype 3 selecting randomized clinical trials and prospective National Cohort Studies.

METHODS: (1) PEG-INF-based therapy including sofosbuvir (SOF) + RBV for 12 wk vs SOF + RBV 24 wk; (2) SOF + RBV therapy 12 wk/16 wk vs 24 wk; and (3) the role of RBV in SOF + daclatasvir (DCV) and SOF + ledipasvir (LDV) combinations. This meta-analysis provides robust information with the intention of addressing treatment strategy for hepatitis C virus genotype 3.

RESULTS: A combination treatment including SOF + RBV + PEG-IFN for 12 wk notes better SVR than with only SOF + RBV for 12 wk, although its association with more frequent adverse effects may be a limiting factor. Longer duration therapy with SOF + RBV (24 wk) has achieved higher SVR rates than shorter durations (12 or 16 wk). SOF + LDV are not an ideal treatment for genotype 3.

CONCLUSION: Lastly, SOF + DCV combination is probably the best oral therapy option and the addition of RBV does not appear to be needed to increase SVR rates substantially.

Treatment of HCV in Patients who Failed First-Generation PI Therapy: a Review of Current Literature

The addition of the first direct-acting antiviral agents, the NS3 protease inhibitors boceprevir or telaprevir, to peg interferon and ribavirin was a major advance in the treatment of genotype 1 hepatitis C individuals with sustained virological response (SVR) rates of 63-75 %. Those who did not achieve SVR had high rates of resistance-associated variants against NS3 protease domain. Retreatment options for those who have failed first-generation protease inhibitors generally are guided by retreatment with direct-acting antiviral agents from other classes. Phase 2 and phase 3 data have demonstrated that retreatment with 12-24 weeks of a NS5B inhibitor (sofosbuvir) in combination with a NS5a inhibitor (daclatasvir or ledipasvir) with or without ribavirin can achieve SVR at high rates comparable to treatment-naive individuals.

Estimating the cost-effectiveness of daclatasvir plus asunaprevir in difficult to treat Japanese patients chronically infected with hepatitis C genotype 1b

AIM

Standard of care for chronic hepatitis C in Japan is currently a pegylated interferon (IFN)-α + ribavirin (PR)-based regimen, notably associated with efficacy and tolerability issues. The advent of novel direct-acting antivirals (DAA) has provided more efficacious and better tolerated treatments. This study investigated the cost-effectiveness of the daclatasvir + asunaprevir (DCV + ASV) DAA regimen in patients infected with hepatitis C virus (HCV) genotype 1b who had previously not responded to or were ineligible for IFN-containing regimens.

METHODS

A cost-utility analysis using an established Markov model compared DCV + ASV with simeprevir + PR (SMV + PR), telaprevir + PR (TVR + PR) and no treatment using Japanese-specific model inputs, with costs and utility values discounted at 2%. A cohort of patients was simulated until death and predicted quality-adjusted life-years (QALY) and costs were estimated. A subgroup analysis of patients with no DCV resistance was conducted.

RESULTS

In all scenarios, DCV + ASV was predicted to be dominant over the comparator; namely, DCV + ASV was associated with increased QALY gains and decreased cost. In patients treated during the chronic hepatitis C stage, cost reductions were ¥1 057 288-2 619 206, and in patients treated during the compensated cirrhosis (CC) stage, reductions were ¥1 032 224-2 531 930. QALY gains were 0.749-2.609 and 0.874-3.043, respectively. Results improved when considering the subgroup of patients without DCV resistance.

CONCLUSION

Cost-effectiveness conclusions are similar for patients treated in the chronic hepatitis C and CC disease stages, with DCV + ASV expected to be cost-saving versus standard of care in Japan for patients with HCV genotype 1b patients who have failed prior therapy or are IFN-ineligible/intolerant.

Duplication of the V3 domain in hepatitis C virus (1b) NS5A protein: Clonal analysis and physicochemical properties related to hepatocellular carcinoma occurrence

BACKGROUND

Hepatitis C virus non-structural protein 5A is known to play a role in development of hepatocellular carcinoma (HCC) via interactions with host cell pathways.

OBJECTIVES

Hepatitis C virus genotype 1b strains presenting a wide insertion of 31 amino acids in the non-structural protein 5A V3 domain (V3 DI) were studied to determine whether this V3-like additional domain (V3 DII) was associated with HCC occurrence.

STUDY DESIGN

Seventy-four patients' sera were screened for V3 DII presence regarding clinical status.

RESULTS

Three strains with duplicated V3 were detected among patients with progression to HCC (n=28), two strains among patients with liver cirrhosis (Ci, n=27) and none among patients with chronic hepatitis (Chr, n=19). Phylogenetic trees built from V3 DI and V3 DII sequences indicated that the latter clustered separately. In between-group clonal analysis, V3 DII sequences from the HCC group were found to be more distant from HCV-J than V3 DI sequences (p<0.0001). Between-group comparisons showed significant differences in genetic distances from HCV-J, in HCC V3 DI and HCC V3 DII compared to Ci V3 DI and Ci V3 DII sequences (p<0.0001). HCC V3 DII domain and its junction with V3 DI exhibited higher Shannon entropy values and enrichment in disorder-promoting residues.

CONCLUSIONS

Taken together, our results suggest that V3 DII evolution may differ in strains associated with HCC occurrence. The presence of an intrinsically "disordered" V3 duplicate may alter the NS5A protein network. Further investigations are necessary to elucidate the potential impact of V3 duplication in the context of carcinogenesis.

Hepatitis C Virus: Current and Evolving Treatments for Genotypes 2 and 3

Hepatitis C virus (HCV) genotypes 2 and 3 have previously been classified as easy-to-treat genotypes, because sustained virologic responses (SVRs) up to 80% have been achieved with 24-week peginterferon and ribavirin. More detailed studies have shown differences between HCV genotypes 2 and 3, indicating that genotype 3 has become the most difficult-to-treat genotype. With new drugs, new challenges are emerging regarding relapse rates, the role of ribavirin, and optimal duration of therapy. Sofosbuvir remains the backbone of genotype 3 therapy, whereas this drug is not an option in patients with creatinine clearance lower than 30 mL/min.

Review article: the efficacy and safety of daclatasvir in the treatment of chronic hepatitis C virus infection

BACKGROUND

The treatment of hepatitis C virus (HCV) has evolved dramatically after the introduction of direct acting anti-virals. NS5A protein plays an important role in HCV replication and is an attractive target for drug development.

AIM

To review clinical studies on the efficacy and safety of direct-acting anti-virals regimens containing daclastavir, an NS5A inhibitor, in the treatment of chronic hepatitis C.

METHODS

A Medline search was undertaken to identify relevant literature using search terms including 'daclatasvir', 'HCV treatment' and 'NS5A inhibitors'. Furthermore, we scanned abstracts presented at the recent international meetings in liver disease, viral hepatitis and infectious disease, as well as the reference lists of the review articles to identify publications not retrieved by electronic searches.

RESULTS

Daclatasvir is the first-in-class HCV NS5A inhibitor that has been demonstrated in Phase I-III trials to have a potent anti-viral effect and clinical efficacy across multiple HCV genotypes (GT). Daclastavir is generally safe and well tolerated, with a low barrier to resistance and low potential for drug-drug interaction. When Daclastavir is added to PEG-IFN/RBV platform, sustained virological response (SVR) rates are increased significantly compared with PEG-IFN/RBV alone. The all-oral combination of Daclastavir/asunaprevir (ASV; protease inhibitor) has high SVR rates against GT1b, but less activity against GT1a. Dual combination of Daclastavir/Sofosbuvir (SOF; nucleotide polymerase inhibitor) and triple combination of Daclastavir/ASV/beclabuvir (BCV; non-nucleoside polymerase inhibitor) have demonstrated >90% SVR rates in both treatment naïve and treatment-experienced patients with GT1. Furthermore, Daclastavir/SOF combination has also demonstrated up to 90% SVR rates in patients with GT3, and in those with human immunodeficiency virus coinfection, cirrhosis and post-transplant HCV recurrence with any GT. Daclastavir/ASV/BCV has primarily demonstrated near 100% SVR rates in patients with GT4.

CONCLUSION

Daclastavir-containing regimens, with or without PEG-IFN, have shown promising results in clinical trials, and present an excellent treatment option for those with chronic HCV and for multiple genotypes.

Psychiatric and substance use disorders co-morbidities and hepatitis C: Diagnostic and treatment implications

Chronic hepatitis C virus (HCV) viral infection is the most common blood-borne viral infection and approximately 2%-3% of the world’s population or 170-200 million people are infected. In the United States as many as 3-5 million people may have HCV. Psychiatric and substance use disorders (SUDs) are common co-morbid conditions found in people with HCV and are factors in predisposing people to HCV infection. Also, these co-morbidities are reasons that clinicians exclude people from antiviral therapy in spite of evidence that people with HCV and co-morbid psychiatric and SUD can be safely and effectively treated. Furthermore, the neuropsychiatric side effects of interferon (IFN), until recently the mainstay of antiviral therapy, have necessitated an appreciation and assessment of psychiatric co-morbidities present in people with HCV. The availability of new medications and IFN-free antiviral therapy medication combinations will shorten the duration of treatment and exposure to IFN and thus decrease the risk of neuropsychiatric side effects. This will have the consequence of dramatically altering the clinical landscape of HCV care and will increase the number of eligible treatment candidates as treatment of people with HCV and co-morbid psychiatric and SUDs will become increasingly viable. While economically developed countries will rely on expensive IFN-free antiviral therapy, less developed countries will likely continue to use IFN-based therapies at least until such time as IFN-free antiviral medications become generic. The current manuscript discusses the efficacy and viability of treating HCV in people with psychiatric and SUDs comorbidities, the treatment of the neuropsychiatric side effects of IFN -based therapies and the impact of new medications and new treatment options for HCV that offer the promise of increasing the availability of antiviral therapy in this vulnerable population.

Novel benzidine and diaminofluorene prolinamide derivatives as potent hepatitis C virus NS5A inhibitors

Our study describes the discovery of a series of highly potent hepatitis C virus (HCV) NS5A inhibitors based on symmetrical prolinamide derivatives of benzidine and diaminofluorene. Through modification of benzidine, l-proline, and diaminofluorene derivatives, we developed novel inhibitor structures, which allowed us to establish a library of potent HCV NS5A inhibitors. After optimizing the benzidine prolinamide backbone, we identified inhibitors embedding meta-substituted benzidine core structures that exhibited the most potent anti-HCV activities. Furthermore, through a battery of studies including hERG ligand binding assay, CYP450 binding assay, rat plasma stability test, human liver microsomal stability test, and pharmacokinetic studies, the identified compounds 24, 26, 27, 42, and 43 are found to be nontoxic, and are expected to be effective therapeutic anti-HCV agents.

HIV-1, HCV and alcohol in the CNS: potential interactions and effects on neuroinflammation

Approximately 25% of the HIV-1 positive population is also infected with HCV. The effects of alcohol on HIV-1 or HCV infection have been a research topic of interest due to the high prevalence of alcohol use in these infected patient populations. Although it has long been known that HIV-1 infects the brain, it has only been a little more than a decade since HCV infection of the CNS has been characterized. Both viruses are capable of infecting and replicating in microglia and increasing the expression of proinflammatory cytokines and chemokines, including IL-6 and IL-8. Investigations focusing on the effects of HIV-1, HCV or alcohol on neuroinflammation have demonstrated that these agents are capable of acting through overlapping signaling pathways, including MAPK signaling molecules. In addition, HIV-1, HCV and alcohol have been demonstrated to increase permeability of the blood-brain barrier. Patients infected with either HIV-1 or HCV, or those who use alcohol, exhibit metabolic abnormalities in the CNS that result in altered levels of n-acetyl aspartate, choline and creatine in various regions of the brain. Treatment of HIV/HCV co-infection in alcohol users is complicated by drug-drug interactions, as well as the effects of alcohol on drug metabolism. The drug-drug interactions between the antiretrovirals and the antivirals, as well as the effects of alcohol on drug metabolism, complicate existing models of CNS penetration, making it difficult to assess the efficacy of treatment on CNS infection.

Current status and emerging challenges in the treatment of hepatitis C virus genotypes 4 to 6

Hepatitis C virus (HCV) genotypes 4, 5 and 6 are mainly present in Africa, the Middle East and Asia and they have been less extensively studied with respect to epidemiology, natural disease history and therapeutic endpoints. Response rates to a 48-wk combined peginterferon/ribavirin treatment range to 40%-69% for HCV 4, 55%-60% for HCV 5 and 60%-90% for HCV 6. Response-guided schedules are recommended to optimize the outcomes of peginterferon/ribavirin treatment in HCV 4 and, in form of preliminary data, for HCV 6, but no data are yet available to support such an individualization of therapy for HCV 5. Recently, the direct-acting antivirals (DAAs) with pan-genotypic activities simeprevir, sofosbuvir and daclatasvir have been recommended in triple regimens with peginterferon/ribavirin for the treatment of HCV genotypes 4 to 6 infections. In the future, DAA-based interferon-free therapies are awaited to drastically improve treatment outcomes in HCV. However, efforts to improve treatment outcomes with peginterferon/ribavirin should continue, as the HCV 4-6 infected population is mainly based in resource-limited settings with restricted access to the costly DAAs.

Different interaction profiles of direct-acting anti-hepatitis C virus agents with human organic anion transporting polypeptides

Simeprevir (SMV), asunaprevir (ASV), daclatasvir (DCV), and sofosbuvir (SFV), which are newly developed direct-acting antiviral agents (DAAs) against hepatitis C virus (HCV) infection, are among the key components of anti-HCV regimens. Preclinical studies have identified inhibitory properties for some of these DAAs against organic anion transporting polypeptide 1B (OATP1B) functions. However, their details remain mostly uncharacterized. Because OATP1B1 and OATP1B3 play determinant roles in the pharmacokinetics of various drugs via their uptake into human hepatocytes, it is plausible that the inhibition of these OATP1Bs by a DAA would create a potential risk of drug-drug interaction, which has been an emerging concern in anti-HCV therapy. Accordingly, in the present study, we intended to clarify the inhibitory characteristics of newly developed DAAs toward OATP1B1 and -1B3 functions. The results of our coincubation inhibition assays have shown that all tested DAAs could inhibit OATP1B1 functions and that SMV, ASV, and DCV (to a lesser extent), but not SFV, exhibited long-lasting preincubation inhibitory effects on OATP1B1 functions. It was also found that the preincubation inhibitory effects of SMV and ASV could augment their coincubation inhibition potency. Furthermore, significant, but differential, inhibitory effects of the DAAs on the OATP1B3 function were identified. To summarize, our results clearly show that the newly developed DAAs are newly identified OATP1B1 and OATP1B3 inhibitors with distinctive interaction properties. It is believed that these inhibition profiles will provide essential information to all concerned parties with respect to the clinical significance of DAA-mediated inhibition of OATP1Bs in anti-HCV therapy.

Estimating the Long-Term Clinical and Economic Outcomes of Daclatasvir Plus Asunaprevir in Difficult-to-Treat Japanese Patients Chronically Infected with Hepatitis C Genotype 1b

OBJECTIVES

Japan has one of the highest endemic rates of hepatitis C virus (HCV) infection. Treatments in Japan are currently limited to interferon-alfa-based regimens, which are associated with tolerability and efficacy issues. A novel regimen combining two oral HCV therapies, daclatasvir and asunaprevir (DCV + ASV), has shown favorable results in Japanese patients with chronic genotype 1b HCV infection. Comparisons of clinical and economic outcomes associated with DCV + ASV treatment and current standards of care were investigated.

METHODS

The MOdelling the NAtural histoRy and Cost-effectiveness of Hepatitis cost-effectiveness model projected outcomes in 1000 patients aged 70 years with either chronic hepatitis C or compensated cirrhosis over a lifetime simulation. Japanese-specific disease transition rates were used, and discounting was applied annually at a rate of 2%. Efficacy data for DCV + ASV and telaprevir triple therapy (telaprevir + pegylated interferon-alfa + ribavirin [TVR + pegIFN-α/RBV]) were obtained from a Japanese subgroup analysis found within a global meta-analysis: sustained virological response rates of 74%, 85%, and 87% were reported for null responders (NRs), partial responders (PRs), and interferon-alfa-ineligible/intolerant patients, respectively, treated with DCV + ASV, and rates of 42% and 59% were reported for NRs and PRs, respectively, treated with TVR + pegIFN-α/RBV.

RESULTS

Initiating DCV + ASV treatment in patients in the chronic hepatitis C disease stage resulted in quality-adjusted life-year gains of 0.96 and 0.77 over TVR + pegIFN-α/RBV for NRs and PRs, respectively, and a gain of 2.61 in interferon-alfa-ineligible/intolerant patients over no treatment. Similarly, quality-adjusted life-year gains of 1.11, 0.90, and 3.05 were observed when initiating treatment in patients in the compensated cirrhosis stage. Cumulative lifetime events of decompensated cirrhosis, hepatocellular carcinoma, and liver-related mortality were reduced by up to 66, 115, and 128, respectively, with DCV + ASV treatment.

CONCLUSIONS

There is a lack of successful therapies for patients with HCV who have previously failed to achieve sustained virological response or are ineligible for interferon-alfa-based therapies. Results demonstrate that the provision of an alternative, interferon-alfa-free regimen, such as DCV + ASV, offers significant value in terms of avoiding life-threatening liver complications and increasing patients' quality of life.

Discovery of daclatasvir, a pan-genotypic hepatitis C virus NS5A replication complex inhibitor with potent clinical effect

The discovery and development of the first-in-class hepatitis C virus (HCV) NS5A replication complex inhibitor daclatasvir (6) provides a compelling example of the power of phenotypic screening to identify leads engaging novel targets in mechanistically unique ways. HCV NS5A replication complex inhibitors are pan-genotypic in spectrum, and this mechanistic class provides the most potent HCV inhibitors in vitro that have been described to date. Clinical trials with 6 demonstrated a potent effect on reducing plasma viral load and, in combination with mechanistically orthogonal HCV inhibitors, established the ability to cure even the most difficult infections without the need for immune stimulation. In this Drug Annotation, we describe the discovery of the original high-throughput screening lead 7 and the chemical conundrum and challenges resolved in optimizing to 6 as a clinical candidate and finally we summarize the results of select clinical studies.

Review article: HCV genotype 3 – the new treatment challenge

BACKGROUND

Over the past several years, hepatitis C therapy has been pegylated interferon and ribavirin based. Although protease inhibitor-based therapy has enhanced response rates in genotype 1, the recent advances in therapy have demonstrated a challenge in genotype 3, a highly prevalent infection globally.

AIM

To provide a comprehensive summary of the literature evaluating the unique characteristics and evolving therapies in genotype 3.

METHODS

A structured search in PubMed, the Cochrane Library and EMBASE was performed using defined key words, including only full text papers and abstracts in English.

RESULTS

HCV genotype 3 is more prevalent in Asia and among intra-venous drug users. Furthermore, it interferes with lipid and glucose metabolism, and the natural history involves a more rapid progression of liver disease and a higher incidence of hepatocellular carcinoma (HCC). New therapies with protease inhibitors have focused on genotype 1 largely and have demonstrated enhanced responses, but have limited activity against genotype 3. Thus far, in clinical trials, NS5B and NS5A inhibitors have performed more poorly in genotype 3, while a cyclophilin inhibitor, alisporivir, has shown promise.

CONCLUSIONS

As treatments for HCV have evolved, genotype 3 has become the most difficult to treat. Furthermore, genotype 3 has special characteristics, such as insulin resistance and alterations in lipid metabolism, which may partly explain the lower treatment responses. A great deal of emphasis on advancing therapy is needed in this population that appears to have a more rapid progression of liver disease and a higher incidence of HCC.

Hepatitis C virus NS5A inhibitors and drug resistance mutations

Some direct-acting antiviral agents for hepatitis C virus (HCV), such as telaprevir and boceprevir have been available since 2011. It was reported that HCV NS5A is associated with interferon signaling related to HCV replication and hepatocarcinogenesis. HCV NS5A inhibitors efficiently inhibited HCV replication in vitro. Human studies showed that dual, triple and quad regimens with HCV NS5A inhibitors, such as daclatasvir and ledipasvir, in combination with other direct-acting antiviral agents against other regions of HCV with or without peginterferon/ribavirin, could efficiently inhibit HCV replication according to HCV genotypes. These combinations might be a powerful tool for “difficult-to-treat” HCV-infected patients. “First generation” HCV NS5A inhibitors such as daclatasvir, ledipasvir and ABT-267, which are now in phase III clinical trials, could result in resistance mutations. “Second generation” NS5A inhibitors such as GS-5816, ACH-3102, and MK-8742, have displayed improvements in the genetic barrier while maintaining potency. HCV NS5A inhibitors are safe at low concentrations, which make them attractive for use despite low genetic barriers, although, in fact, HCV NS5A inhibitors should be used with HCV NS3/4A inhibitors, HCV NS5B inhibitors or peginterferon plus ribavirin. This review article describes HCV NS5A inhibitor resistance mutations and recommends that HCV NS5A inhibitors be used in combination regimens potent enough to prevent the emergence of resistant variants.

Hepatitis C virus NS5A replication complex inhibitors: the discovery of daclatasvir

The biphenyl derivatives 2 and 3 are prototypes of a novel class of NS5A replication complex inhibitors that demonstrate high inhibitory potency toward a panel of clinically relevant HCV strains encompassing genotypes 1-6. However, these compounds exhibit poor systemic exposure in rat pharmacokinetic studies after oral dosing. The structure-activity relationship investigations that improved the exposure properties of the parent bis-phenylimidazole chemotype, culminating in the identification of the highly potent NS5A replication complex inhibitor daclatasvir (33) are described. An element critical to success was the realization that the arylglycine cap of 2 could be replaced with an alkylglycine derivative and still maintain the high inhibitory potency of the series if accompanied with a stereoinversion, a finding that enabled a rapid optimization of exposure properties. Compound 33 had EC50 values of 50 and 9 pM toward genotype-1a and -1b replicons, respectively, and oral bioavailabilities of 38-108% in preclinical species. Compound 33 provided clinical proof-of-concept for the NS5A replication complex inhibitor class, and regulatory approval to market it with the NS3/4A protease inhibitor asunaprevir for the treatment of HCV genotype-1b infection has recently been sought in Japan.

Discovery and development of hepatitis C virus NS5A replication complex inhibitors

Lead inhibitors that target the function of the hepatitis C virus (HCV) nonstructural 5A (NS5A) protein have been identified by phenotypic screening campaigns using HCV subgenomic replicons. The demonstration of antiviral activity in HCV-infected subjects by the HCV NS5A replication complex inhibitor (RCI) daclatasvir (1) spawned considerable interest in this mechanistic approach. In this Perspective, we summarize the medicinal chemistry studies that led to the discovery of 1 and other chemotypes for which resistance maps to the NS5A protein and provide synopses of the profiles of many of the compounds currently in clinical trials. We also summarize what is currently known about the NS5A protein and the studies using NS5A RCIs and labeled analogues that are helping to illuminate aspects of both protein function and inhibitor interaction. We conclude with a synopsis of the results of notable clinical trials with HCV NS5A RCIs.