Sofosbuvir and ABT-450: Terminator of hepatitis C virus?

Effect of Sofosbuvir Administration and Its Withdrawal on the Submandibular Salivary Gland of Adult Male Albino Rats: A Histological and Ultra-Structural Study

BACKGROUND:

Sofosbuvir (SOF) was approved in 2013 as a part of first-line treatment for hepatitis C virus (HCV); it has activity against all genotypes with extrahepatic adverse effects have recently arisen.

AIM:

Investigating sofosbuvir-induced alterations in the rat submandibular salivary gland (SMSG).

METHODS:

A group of 80 adult albino rats weighing about ± 150 gm were used in the experiment. The rats were divided into 3 groups: Group I (control group) received distilled water, Group II (experimental group) divided into 2 subgroups and received SOF 40 mg/kg/day dissolved in distilled water for 1 and 3 months and Group III (recovery group) allowed for 1 month of recovery after SOF withdrawal. All animals were sacrificed; the SMSG was dissected, and specimens were examined histologically and ultra-structurally.

RESULTS:

Compared to Group I, Group II subgroup (1) showed acinar and ductal vacuolisation, discontinuity of the epithelial lining associated with retained secretion and congested blood vessels. These changes were found to be exaggerated in the subgroup (2) accompanied by acinar and ductal shrinkage, interstitial oedema, haemorrhage, chronic inflammatory cells infiltration and loss of gland compactness. Amelioration of the histological changes was detected in Group III after SOF withdrawal. The ultrastructural examination confirmed these histological results.

CONCLUSION:

SOF had induced apparent alterations in the structure and ultrastructure of SMSG. The SOF-induced alterations were time-dependent, attributed mainly to mitochondrial toxicity and partially ameliorated by its withdrawal.

Unexpected Response Profiles Seen in Hepatitis C Virus-Infected Patients Treated with Sofosbuvir Plus Ribavirin: Five Case Reports

Direct-acting antivirals (DAAs) have been proved as potent agents in the new era of Hepatitis C therapeutics. DAA has evolved to prove highly efficacious treatment rates and sustained virological response in hepatitis C virus (HCV)-treated patients and has shown minimal side effects, but in this study, we reported five cases that showed unusual response toward the use of DAA. The diagnosis was an unusual response of abruptly high viral titers and liver function tests (LFTs) in patients who received DAA combination therapy. The patients received sofosbuvir (400 mg) and ribavirin for 6 months. Although 6-month long recommended DAA combination therapy with ribavirin cleared HCV after 6 months, during the treatment period, five patients experienced unusually and unexpectedly high viral loads and LFTs level in the middle of therapy tenure and then sudden decline of viral titers after completion of treatment. This is the first study to describe the unusual response shown by patients treated with sofosbuvir-based combined therapy that experienced abrupt and marked rise in viral loads during the initial months of treatment followed by sudden elimination of virus during last 2 months of treatment. Although satisfactory response to DAA is well reported, clinicians and policy makers should deliberate upon the exceptions and ensure the proper implementation of International guidelines with modifications according to this population, if necessary.

Effectiveness of Sofosbuvir, Ribavirin and PEG-IFNα-2a in the Treatment of Naïve Egyptian Patients With Chronic Hepatitis C Virus Genotype 4

BACKGROUND

Egypt is one of the largest epidemic areas of hepatitis C virus (HCV) in the world. Its prevalent genotype is 4 with a majority of subtype 4a. In 2013, the Food and Drug Administration approved a new direct-acting antiviral drug (sofosbuvir) to treat patients with chronic HCV infection. In Egypt, the patients are already being treated with sofosbuvir in conjunction with ribavirin and pegylated interferon alfa-2a (PEG-IFNα-2a) for 12 weeks since 2015. The present study was planned to explain the efficacy of this treatment regimen against the HCV genotype 4a in Egyptian patients and its pretreatment predictive factors of virological response.

METHODS

In this population-based study, serum samples were biochemically analyzed and the HCV RNA levels were quantified. The direct sequencing and bioinformatics analysis were utilized to investigate the mutation of the core protein.

RESULTS

The sustained virological response (SVR) and non-SVR were 72% and 16% respectively, but the nonvirological response was only 12% following the treatment regimen. The multivariable analysis recognized viral (level of viremia and substitution of aa70) and host-related factors (age, alanine aminotransferase and aspartate aminotransferase levels) affecting the virological response in patients infected with high viral load of HCV 4a.

CONCLUSIONS

Overall, these results concluded that sofosbuvir with ribavirin and PEG-IFNα-2a are highly efficient in HCV-4a Egyptian patients where a high SVR was achieved (72%). In addition to this, there is a significant association between core protein mutations and treatment outcome predominantly at amino acid position 70 (Arg or Gln).

Generic ledipasvir-sofosbuvir for patients with chronic hepatitis C: A real-life observational study

BACKGROUND & AIMS

Few patients from developing countries can afford brand name direct-acting antiviral agents for treating hepatitis C virus (HCV) infection, and controversy regarding the bioequivalence of generics exists. This study aimed to observe the safety and efficacy of 8 or 12weeks of generic ledipasvir-sofosbuvir with or without ribavirin for Chinese genotype 1b HCV-infected patients.

METHODS

In this open-labelled observational study, 63 cirrhotic (group 1) and 65 non-cirrhotic (group 2) patients were administered generic ledipasvir-sofosbuvir plus 1000-1200mg of ribavirin daily for 12 and 8weeks, respectively; and 64 non-cirrhotic patients (group 3) received ledipasvir-sofosbuvir for 8weeks. The primary efficacy endpoint was undetectable HCV RNA at week 12 (SVR12) after cessation of therapy. Safety and pharmacokinetic data were collected.

RESULTS

One hundred and eighty-seven patients completed treatment, and the latest undetectable HCV RNA was observed in three patients with cirrhosis at week 5 during treatment. Intention-to-treat analysis revealed 96.8% (61/63), 96.9% (63/65), and 96.9% (62/64) of SVR12 rates in groups 1, 2, and 3, respectively. One patient in group 3 relapsed at post-treatment week 4. The regimens were generally well-tolerated. The most common adverse events were fatigue (17.8%), diarrhea (10.9%), and headache (9.9%). Four patients discontinued therapy due to diarrhea and vomiting. One patient from group 2 discontinued treatment on day 29 because of drug-unaffordability; fortunately, she achieved SVR12.

CONCLUSION

This study demonstrated that 8 or 12weeks of generic ledipasvir-sofosbuvir with or without ribavirin are safe and effective for patients with genotype 1b HCV infection.

LAY SUMMARY

The price of Harvoni® has led to restrictions and access limitations in many developing and even developed countries with limited healthcare budgets. Gilead approved generic ledipasvir-sofosbuvir costs far less than Harvoni® and presents a similar cure rate for patients with chronic hepatitis C.

Nidovirus RNA polymerases: Complex enzymes handling exceptional RNA genomes

Coronaviruses and arteriviruses are distantly related human and animal pathogens that belong to the order Nidovirales. Nidoviruses are characterized by their polycistronic plus-stranded RNA genome, the production of subgenomic mRNAs and the conservation of a specific array of replicase domains, including key RNA-synthesizing enzymes. Coronaviruses (26-34 kilobases) have the largest known RNA genomes and their replication presumably requires a processive RNA-dependent RNA polymerase (RdRp) and enzymatic functions that suppress the consequences of the typically high error rate of viral RdRps. The arteriviruses have significantly smaller genomes and form an intriguing package with the coronaviruses to analyse viral RdRp evolution and function. The RdRp domain of nidoviruses resides in a cleavage product of the replicase polyprotein named non-structural protein (nsp) 12 in coronaviruses and nsp9 in arteriviruses. In all nidoviruses, the C-terminal RdRp domain is linked to a conserved N-terminal domain, which has been coined NiRAN (nidovirus RdRp-associated nucleotidyl transferase). Although no structural information is available, the functional characterization of the nidovirus RdRp and the larger enzyme complex of which it is part, has progressed significantly over the past decade. In coronaviruses several smaller, non-enzymatic nsps were characterized that direct RdRp function, while a 3'-to-5' exoribonuclease activity in nsp14 was implicated in fidelity. In arteriviruses, the nsp1 subunit was found to maintain the balance between genome replication and subgenomic mRNA production. Understanding RdRp behaviour and interactions during RNA synthesis and subsequent processing will be key to rationalising the evolutionary success of nidoviruses and the development of antiviral strategies.

Efficacy and Safety of Ledipasvir/Sofosbuvir with and without Ribavirin in Patients with Chronic Hepatitis C Virus Genotype 1 Infection: a meta-analysis

BACKGROUND

The addition of ribavirin (RBV) to the combination treatment of Ledipasvir (LDV) and Sofosbuvir (SOF) remains controversial in the treatment of hepatitis C virus (HCV) infection. We performed a meta-analysis to assess the efficacy and safety of the LDV-SOF with and without RBV in treating HCV genotype 1 patients.

METHOD

The electronical databases of PubMed Medline, EMBASE database, Cochrane Central Register of Controlled Trials (CENTRAL) and ClinicalTrials.gov website with registered trials were searched. Eligible studies were randomized controlled trials (RCTs) and prospective cohort studies that assessed the efficacy and safety of LDV-SOF with or without RBV in patients with HCV genotype 1 (GT 1). Two reviewers independently screened studies, extracted data and assessed methodology quality. Review Manager 5.3 software was used to analyze the data.

RESULTS

Seven studies involving 2,626 patients with HCV GT 1 - some of whom had cirrhosis - were included in this meta-analysis. The addition of RBV to LDV- SOF regimen neither significantly improved sustained viral response at 12 weeks (SVR12) after the last dose of treatment (RR=1.00, 95%CI 0.99-1.01, p=0.99) nor decreased virologic breakthrough (RR=1.01, 95%CI 0.14-7.19, p=0.99) and relapse (RR=1.36, 95% CI 0.81-2.29, p=0.24). There was no significant difference in the incidence of discontinuation (RR=0.61, 95%CI 0.25-1.53, p=0.30) between LDV- SOF therapy and LDV- SOF plus RBV. LDV- SOF plus RBV therapy had significantly higher rate of the overall adverse events (RR=0.88, 95%CI=0.84- 0.92, p<0.00001). LDV - SOF therapy had higher incidence of serious adverse events (RR=1.60, 95%CI=1.00-2.56, p=0.05) than LDV-SOF plus RBV.

CONCLUSION

This meta-analysis suggests that LDV-SOF based therapy is a safe and effective treatment for patients with GT 1 HCV. The addition of RBV to LDV-SOF may increase toxicity without achieving improved efficacy. However, due to the relatively small sample sizes and moderate risk of bias of included studies, large-scale and high-quality clinical research is still needed to confirm the results.

Discovery of a Broad-Spectrum Antiviral Compound That Inhibits Pyrimidine Biosynthesis and Establishes a Type 1 Interferon-Independent Antiviral State

Viral emergence and reemergence underscore the importance of developing efficacious, broad-spectrum antivirals. Here, we report the discovery of tetrahydrobenzothiazole-based compound 1, a novel, broad-spectrum antiviral lead that was optimized from a hit compound derived from a cytopathic effect (CPE)-based antiviral screen using Venezuelan equine encephalitis virus. Compound 1 showed antiviral activity against a broad range of RNA viruses, including alphaviruses, flaviviruses, influenza virus, and ebolavirus. Mechanism-of-action studies with metabolomics and molecular approaches revealed that the compound inhibits host pyrimidine synthesis and establishes an antiviral state by inducing a variety of interferon-stimulated genes (ISGs). Notably, the induction of the ISGs by compound 1 was independent of the production of type 1 interferons. The antiviral activity of compound 1 was cell type dependent with a robust effect observed in human cell lines and no observed antiviral effect in mouse cell lines. Herein, we disclose tetrahydrobenzothiazole compound 1 as a novel lead for the development of a broad-spectrum, antiviral therapeutic and as a molecular probe to study the mechanism of the induction of ISGs that are independent of type 1 interferons.

A Complex Network of Interactions between S282 and G283 of Hepatitis C Virus Nonstructural Protein 5B and the Template Strand Affects Susceptibility to Sofosbuvir and Ribavirin

The hepatitis C virus (HCV) RNA-dependent RNA-polymerase NS5B is essentially required for viral replication and serves as a prominent drug target. Sofosbuvir is a prodrug of a nucleotide analog that interacts selectively with NS5B and has been approved for HCV treatment in combination with ribavirin. Although the emergence of resistance to sofosbuvir is rarely seen in the clinic, the S282T mutation was shown to decrease susceptibility to this drug. S282T was also shown to confer hypersusceptibility to ribavirin, which is of potential clinical benefit. Here we devised a biochemical approach to elucidate the underlying mechanisms. Recent crystallographic data revealed a hydrogen bond between S282 and the 2'-hydroxyl of the bound nucleotide, while the adjacent G283 forms a hydrogen bond with the 2'-hydroxyl of the residue of the template that base pairs with the nucleotide substrate. We show that DNA-like modifications of the template that disrupt hydrogen bonding with G283 cause enzyme pausing with natural nucleotides. However, the specifically introduced DNA residue of the template reestablishes binding and incorporation of sofosbuvir in the context of S282T. Moreover, the DNA-like modifications of the template prevent the incorporation of ribavirin in the context of the wild-type enzyme, whereas the S282T mutant enables the binding and incorporation of ribavirin under the same conditions. Together, these findings provide strong evidence to show that susceptibility to sofosbuvir and ribavirin depends crucially on a network of interdependent hydrogen bonds that involve the adjacent residues S282 and G283 and their interactions with the incoming nucleotide and complementary template residue, respectively.

Using an Old Drug to Target a New Drug Site: Application of Disulfiram to Target the Zn-Site in HCV NS5A Protein

In viral proteins, labile Zn-sites, where Zn(2+) is crucial for maintaining the native protein structure but the Zn-bound cysteines are reactive, are promising drug targets. Here, we aim to (i) identify labile Zn-sites in viral proteins using guidelines established from our previous work and (ii) assess if clinically safe Zn-ejecting agents could eject Zn(2+) from the predicted target site and thus inhibit viral replication. As proof-of-concept, we identified a labile Zn-site in the hepatitis C virus (HCV) NS5A protein and showed that the antialcoholism drug, disulfiram, could inhibit HCV replication to a similar extent as the clinically used antiviral agent, ribavirin. The discovery of a novel viral target and a new role for disulfiram in inhibiting HCV replication will enhance the therapeutic armamentarium against HCV. The strategy presented can also be applied to identify labile sites in other bacterial or viral proteins that can be targeted by disulfiram or other clinically safe Zn-ejectors.

Meta-analysis of the efficacy and safety of sofosbuvir for the treatment of hepatitis C virus infection

BACKGROUND

Hepatitis C virus infection is a worldwide health problem and one of the leading causes of cirrhosis and hepatocellular carcinoma. Recently, sofosbuvir was introduced to the therapeutic arsenal against this virus, thereby paving the way for all-oral regimen. Aims of the review This study aimed to systematically analyze the efficacy and safety of sofosbuvir for the treatment of hepatitis C virus infection.

METHOD

PubMed and EMBASE database searches were conducted using "sofosbuvir" as the search term. Phase III clinical studies retrieved from the two databases and resources posted on the Drug@FDA and ClinicalTrials.gov websites were evaluated with regard to outcomes of the efficacy and safety analyses of the drug.

RESULTS

Eight Phase III clinical studies compared the efficacy and safety of sofosbuvir. When sofosbuvir replaced peginterferon which was used in the previous standard regimen, a superior sustained virologic response, as defined by a viral RNA load less than the lower limit of quantification 12 weeks after cessation of therapy, was obtained (74.3 vs. 66.7%, p < 0.05). The response improved even more (90.8 vs. 66.7%, p < 0.0001) when sofosbuvir was used as an add-on therapy to the standard regimen. The overall odds ratio to achieve the response in the sofosbuvir-containing arm of the eight clinical studies was 3.66 times greater (95% CI 3.00-4.46) than that of the standard regimen arm. During the eight clinical studies, adverse events were observed in 83.61 and 87.22% of the patients in the sofosbuvir and non-sofosbuvir arms, respectively, with the most frequent events being mild central nervous system symptoms such as fatigue, headache, and asthenia.

CONCLUSIONS

Sofosbuvir was safe and effective in the treatment of hepatitis C virus genotype 1, 2, 3, or 4 infections. However, the lack of persistence of the sustained virologic response beyond the study duration and long-term safety concerns need to be addressed in future studies.

Interferon-inducible cholesterol-25-hydroxylase inhibits hepatitis C virus replication via distinct mechanisms

Cholesterol 25-hydroxylase (CH25H) as an interferon-stimulated gene (ISG) has recently been shown to exert broad antiviral activity through the production of 25-hydroxycholesterol (25HC), which is believed to inhibit the virus-cell membrane fusion during viral entry. However, little is known about the function of CH25H on HCV infection and replication and whether antiviral function of CH25H is exclusively mediated by 25HC. In the present study, we have found that although 25HC produced by CH25H can inhibit HCV replication, CH25H mutants lacking the hydroxylase activity still carry the antiviral activity against HCV but not other viruses such as MHV-68. Further studies have revealed that CH25H can interact with the NS5A protein of HCV and inhibit its dimer formation, which is essential for HCV replication. Thus, our work has uncovered a novel mechanism by which CH25H restricts HCV replication, suggesting that CH25H inhibits viral infection through both 25HC-dependent and independent events.

Sofosbuvir: A novel treatment option for chronic hepatitis C infection

Hepatitis C currently infects more than 170 million people around the world, leading to significant morbidity and mortality. The current standard of care for HCV infection, including one of the two protease inhibitors, telaprevir or boceprevir, for 12-32 weeks, along with pegylated interferon alfa-2a (PEG-IFN-α) and ribavirin for up to 48 weeks, is unsatisfactory in many cases, either because of lack of efficacy or because of treatment-related adverse effects. There is an urgent need of new drugs with improved efficacy as well as a safety profile. Sofosbuvir, a recently approved nucleotide analog, is a highly potent inhibitor of the NS5B polymerase in the Hepatitis C virus (HCV), and has shown high efficacy in combination with several other drugs, with and without PEG-INF, against HCV. It offers many advantages due to its high potency, low side effects, oral administration, and high barrier to resistance. The efficacy and safety were demonstrated in many large and well-designed phase 2 and phase 3 clinical trials like NEUTRINO, PROTON, ELECTRON, ATOMIC, COSMOS, FUSION, FISSION, NUCLEAR, POSITRON, and the like. It is generally well-tolerated. Adverse events that occurred include: Headache, insomnia, fatigue, nausea, dizziness, pruritis, upper respiratory tract infections, rash, back pain, grade 1 anemia, and grade 4 lymphopenia; however, the exact safety profile can only be judged when this drug is actually used on a large scale.

[Experience in the management of immunosuppressant treatment with hepatitis C virus protease inhibitors]

INTRODUCTION

Antiviral drugs for the treatment of hepatitis C virus (HCV) infections have a large number of interactions. The aim of this study was to describe the interactions of telaprevir, boceprevir and sofosbuvir with immunosuppressive drugs in liver transplant recipients.

METHODS

A retrospective observational study was performed in liver transplant patients with HCV infection who started treatment with telaprevir, boceprevir or sofosbuvir. Dose, regimens and plasma levels of tacrolimus, cyclosporine and sirolimus before and after antiviral treatment initiation were collected. Average variations in dose, dosing interval and immunosuppressive plasma levels after the start of treatment were calculated.

RESULTS

Thirty-five patients were included. In patients treated with telaprevir (n = 18), the cyclosporine dose was reduced by an average of 59.1% (SD = 14.6%), yielding an average reduction of 14.6% (18.8%) in plasma levels. The dose of tacrolimus was reduced by 34.3% (31.7%), increasing the dosing interval by a mean of 73.4 (38.2) hours. After this variation, tacrolimus levels were increased by an average of 59.7% (89.6%). In patients treated with boceprevir (n = 4), tacrolimus started with a reduction of 18.1% (9.8%) of the initial dose and an average increase in the dosing interval of 12.0 (16.9) hours, showing a mean reduction in plasma levels of 37.7% (21.8%). Sofosbuvir therapy (n = 13) showed no significant variations in immunosuppressive drug levels.

CONCLUSIONS

The interaction of telaprevir and boceprevir with immunosuppressive drugs requires a substantial dose reduction at the beginning of treatment and close monitoring of plasma levels.

NS3 protease inhibitors for treatment of chronic hepatitis C: Efficacy and safety

A new treatment paradigm for hepatitis C is that the treatment must include an existing direct-acting antiviral agent, namely, a protease inhibitor (PI) combined with PEGylated interferon-α and ribavirin. The currently marketed PIs and PIs in clinical trials have different mechanisms of action. The development of new PIs aims for an improved safety profile and higher effectiveness. This article reviews NS3/4A protease inhibitors, focusing on major criteria such as their effectiveness and safety. Specific attention is paid to dosing regimens and adverse event profiles of PIs administered in clinical settings.

New antiviral agents for the treatment of hepatitis C: ABT-450

INTRODUCTION

Hepatitis C virus (HCV) therapy continues to evolve rapidly. ABT-450 is a novel potent inhibitor of the non-structural 3/4A protease that has been studied in combination with several agents, allowing shorter duration of therapy and interferon-free/ribavirin-free all-oral regimens. Preliminary data from studies evaluating these new regimens are impressive with sustained virological response (SVR) rates of 88 - 100% after 12 weeks of therapy in patients with previously untreated HCV genotype 1 infection. SVR rates in treatment-experienced patients are also encouraging.

AREAS COVERED

Efficacy and tolerability of antiviral regimens containing ABT-450 boosted with ritonavir (ABT-450/r). Results from published studies and abstracts from recent meetings are presented.

EXPERT OPINION

Newer direct-acting antiviral agents such as ABT-450 promise effective and durable suppression of HCV with interferon/ribavirin-free all-oral regimens. This agent also allows for shorter duration of treatment and has tolerable side effects. Results of clinical trials including a broader spectrum of individuals with HCV infection are eagerly awaited.