Debate - Do we need more HCV drugs?

18th International Workshop on Clinical Pharmacology of Antiviral Therapy
14 - 16 June 2017, Chicago, IL, USA
The 18th edition of the meeting has provided a platform for state-of-the-art discussions of current topics fundamental to the optimal use of antiretroviral therapy. Experts have delivered exceptional talks on a variety of topics and young and established researchers have presented their latest research results during oral abstract presentations and poster viewing sessions.

The presentations and video recordings (providing speaker’s permission has been received) will be available in due course at www.infectiousdiseasesonline.com.

Debate: Do we need more HCV Drugs?
Pro Standpoint
Nancy Reau, MD - Rush University Medical Center, USA
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Con Standpoint
Jürgen Rockstroh, MD - University of Bonn, Germany
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Dr. Nancy Reau, MD - Yes

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Juergen Rockstroh - No

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Link to debate provided by Henry E. Chang via Twitter.
18AntiviralPK – Presentation
Session 9: Hepatitis C Virus 

2016/2017 - New HCV two and three drug regimens on their way: what do they promise?

Summary for AASLD 2016 for Hepatitis C - New HCV two and three drug regimens on their way: what do they promise? And what do clinicians need to look out for under DAA combination therapy and beyond SVR?
Jurgen K. Rockstroh M.D., Professor of Medicine University of Bonn, Germany

Jules Levin Executive Director of National AIDS Treatment Advocacy Project (NATAP) recently added this complete summary of AASLD 2016 including links to each study cited in the article. Here is a summary of the topics and introduction with a few links of interest, click here to view the full text article.

Topic Summary
Risk of HBV reactivation after starting DAA therapy
Surveillance for hepatocellular carcinoma (HCC) and risk for HCC after achieving SVR following DAA therapy.
Intravenous drug users and patients on opioid substitution therapy
Patients in the prison setting
HIV/HCV coinfected patients
Patients with renal insufficiency or on hemodialysis
Patients older than 70 years
Patients receiving short treatment durations of 8 week
HCV three drug rescue combinations with licensed drugs
New dual DAA combinations
New three drug combinations

Introduction
At present, besides the Abbvie 3-D regimen, mostly dual hepatitis C (HCV) direct acting antiviral (DAA) combinations which are coformulated as single tablet regimens have become the gold standard for first line treatment of all HCV genotypes. Despite SVR rates on average above 95% there are still attempts in the field to develop three drug combinations (so called triplets) or very potent new dual regimens which may allow shortening of treatment duration and may also add to the antiviral pangenotypic activity of all oral DAA combination therapy. Obviously, even with the currently licensed HCV drugs, three drug combinations may play a role in retreatment of the few patients which experience virological failure under dual DAA-based HCV therapy. Various studies at AASLD this year where devoted to effectiveness and safety of these new three DAA regimens in treatment naïve as well as treatment experienced patients including prior DAA-based treatment failure (1-7). In addition, data on the new and very potent Abbvie dual combination (Glecaprevir (ABT-493)/Pibrentasvir (ABT-530)), again in treatment-naïve, experienced- and prior DAA-failures, was presented (8-10). Another important topic was feedback on safety and effectiveness of various all oral DAA combinations from real-world cohorts including a whole variety of special populations including intravenous drug users, patients on opioid substitution therapy, patients in the prison setting, HIV coinfected, patients with renal insufficiency, patients older than 70 years, patients receiving short treatment durations of 8 week and much more (11-19). As more and more data arises from very diverse patient populations it appears as if no special or hard to treat patient group seems to exist any longer. In the end it really is more about getting access to therapy feasible for some of those more marginalized patient groups. A further important topic was around clinically relevant issues which clinicians who treat HCV need to be aware of, including risk for hepatitis B (HBV) reactivation after starting DAA therapy, as well as the risk for development of hepatocellular cancer (HCC) after achieving SVR (20-24). Although HCV remained to be a widely recognized topic throughout AASLD, it is becoming apparent that other topics in hepatology including NASH, alcoholic hepatitis, hepatitis B, HCC and primary biliary cholangitis are gaining importance and presentation space especially in the late-breaker session. A more intensified discussion on national HCV screening programs, HCV treatment uptake and linkage to care at AASLD would be desirable to politically underline the need to continue the fight to ensure global access of HCV therapies throughout the world.

View full text article with slides over at National AIDS Treatment Advocacy Project (NATAP)

Of Interest
Hepatitis C Hot Topics - Research and News of 2016
Take a look back at the top HCV news stories of 2016. Sit back and review a collection of hepatitis C research articles, guideline updates, conference reports, learning activities, and news from around the web

AbbVie Awaits NDA Approval For Hepatitis C Treatment
Dec. 19, 2016
AbbVie (ABBV), a global biopharmaceutical company, announced that it has submitted a New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for the company's investigational, pan-genotypic regimen of glecaprevir/pibrentasvir (G/P), being evaluated for the treatment of chronic hepatitis C virus (HCV).

Gilead Submits NDA to FDA for Sofosbuvir/Velpatasvir/Voxilaprevir HCV Genotype 1-6
December 8, 2016
Gilead Submits New Drug Application to U.S. Food and Drug Administration for the Investigational Single Tablet Regimen Sofosbuvir/Velpatasvir/Voxilaprevir
- If Approved, SOF/VEL/VOX Would Be the First Once-Daily Single Tablet Regimen Available as a Salvage Therapy for Patients Infected with HCV Genotype 1-6 Who Have Failed Prior Treatment with DAA Regimens Including NS5A Inhibitors -

U.S. prescription drug spending rose 13 percent in 2014: IMS report

U.S. prescription drug spending rose 13 percent in 2014: IMS report
By Bill Berkrot

(Reuters) - U.S. spending on prescription medicines jumped 13 percent to $374 billion in 2014, the biggest percentage increase since 2001, as demand surged for expensive new breakthrough hepatitis C treatments, a report released on Tuesday showed.

Demand for newer cancer and multiple sclerosis treatments, price increases on branded medicines, particularly insulin products for diabetes, and the entry of few new generic versions of big-selling drugs also contributed to the double-digit spending rise in 2014, the report by IMS Health Holdings Inc found.

IMS, a U.S. health care information and technology company, does not foresee a similar U.S. spending jump on prescription medicines this year.

"We certainly expect to see growth in the market size and spending level in 2015, but not at the rate of growth that we're reporting for 2014," said Murray Aitken, executive director of the IMS Institute for Healthcare Informatics, which compiled the report.

"We know that the patent expiry impact will be larger in 2015 than it was last year," he said.

New hepatitis C treatments from Gilead Sciences Inc that virtually guarantee a cure for the liver-destroying virus, with few side effects, led more than 161,000 patients to start treatment in 2014, IMS said. That compares to just 17,000 in 2013, when thousands put off treatment while waiting for the new drugs.

Gilead reported a record-breaking $10.3 billion in first-year sales of Sovaldi as the $1,000-a-pill drug became the poster child for intense criticism of the high cost of new medicines.

The report also noted the large number of so-called orphan drugs that made it to the market in 2014, with the introduction of 18 expensive medicines for rare diseases.

Meanwhile, the entry of new generic versions of branded drugs reduced spending by only about $12 billion in 2014, compared to an impact of about $20 billion the year before and $29 billion in savings in 2012, when cheap generic versions of Pfizer Inc's top-selling cholesterol drug Lipitor began to flood the market.

The lesser savings from generic drugs in 2014 was due in part to U.S. Food and Drug Administration sanctions against India's Ranbaxy that delayed cheap versions of AstraZeneca Plc's blockbuster heartburn drug Nexium.

IMS, which compiles U.S. prescription drug data for the industry, also tracked the impact of the Affordable Care Act on medicine usage, noting a significant rise in prescriptions filled through government Medicaid programs. While those rose by about 17 percent overall, the increase was 25 percent in the 28 states that expanded Medicaid eligibility under ACA.

(Reuters)
(Reporting by Bill Berkrot; Editing by Richard Chang)

On this blog:

Reducing the cost of new hepatitis C drugs
Daclatasvir, Harvoni (ledipasvir/sofosbuvir)/Sovaldi/Viekira Pak.
An index of articles pointing the reader to the current controversy over the high price of Sovaldi, Harvoni (ledipasvir/sofosbuvir) and AbbVie Viekira Pak.

Hepatitis C-Presidio Phase 1a dose-ranging assessment of PPI-668 completed

SAN FRANCISCO -- (BUSINESS WIRE) -- Presidio Pharmaceuticals, Inc. announced today the successful completion of a Phase 1a dose-ranging assessment of PPI-668, a potent, pan-genotypic second-generation hepatitis C virus (HCV) NS5A inhibitor, in healthy volunteers and subsequent advancement to a Phase 1b assessment of the dose-related efficacy in hepatitis C patients.

The Phase 1a dose-ranging assessment of PPI-668 was conducted with 32 healthy volunteers in New Zealand. The trial was a randomized, double-blind, placebo-controlled assessment of the safety and pharmacokinetics of three oral doses of PPI-668, initially assessed as single doses and subsequently as a multi-day regimen, in which the highest PPI-668 dose was given once daily for five successive days. The trial results indicated that all dose regimens of PPI-668 were well-tolerated. There were no serious or severe clinical adverse events, no patterns of treatment-related adverse events or laboratory abnormalities, and all subjects completed the trial successfully.

Pharmacokinetic (PK) analyses of subjects’ plasma samples in the Phase 1a trial indicated that substantial blood levels of PPI-668 were rapidly and consistently achieved and dose proportional. PPI-668 plasma concentrations were orders of magnitude above those shown to inhibit HCV replication in vitro and were maintained at predicted effective concentrations for more than 24 hours. These PK results support once-daily dosing for PPI-668 in future studies. Also important was the observation that in the 5-day multi-dose regimen, steady-state PK was achieved rapidly (by Day 2), with no evidence of subsequent accumulation or changes in the clearance profile of PPI-668.

“These first clinical data for PPI-668 indicate excellent tolerance in healthy subjects for up to five days,” said Nathaniel A. Brown, M.D., Presidio’s Chief Medical Officer. “Equally important, the pharmacokinetic profile of PPI-668 is very encouraging, suggesting that effective plasma concentrations can be obtained with relatively low, once-daily doses of PPI-668 - which will facilitate co-formulation of PPI-668 with other HCV antivirals in future combination therapies for hepatitis C.”

Patient screening for the Phase 1b evaluation of PPI-668 in hepatitis C patients has begun in New Zealand and the United States and will soon include Australia. Dosing of the first cohort of hepatitis C patients will begin this week. Presidio expects to have results regarding the antiviral efficacy of PPI-668 in HCV patients in the second quarter of 2012.

In a second HCV research program focused on inhibitors of the HCV NS5B polymerase, Presidio has discovered a lead chemical series of non-nucleosidic NS5B inhibitors with potent activity against all major HCV genotypes. Preclinical profiling is ongoing with a goal of nominating a candidate for clinical development in the coming months.

With its novel NS5A and NS5B inhibitors, Presidio’s objective is to provide two complementary HCV antivirals that will be appropriate for broad use in optimized future combination therapies for patients with HCV infection. Presidio anticipates that such therapies will have a convenient oral dosing regimen (once or twice daily), will exhibit rapid pan-genotypic efficacy and will be well-tolerated.

ABOUT HEPATITIS C AND NS5A INHIBITORS

Chronic hepatitis C is a persistent, potentially progressive inflammatory liver disease caused by chronic infection with the hepatitis C virus (HCV). Worldwide there are an estimated 130 to 170 million persons with chronic HCV infection. There are 7 major genotypes (strains) of HCV, which have differing geographic distributions. Globally, about 40-60% of patients are infected with HCV genotype-1, with the remaining patients infected with HCV genotypes 2 through 7.

Patients with advanced hepatitis C can develop potentially fatal liver failure or liver cancer, and hepatitis C is estimated to account for over 350,000 deaths per year worldwide (WHO estimate). The current standard-of-care treatment for hepatitis C in the United States, for patients with HCV genotype-1 infection, is combined administration of pegylated-interferon, ribavirin, and first-generation HCV protease inhibitors. This multi-drug treatment is characterized by incomplete efficacy for HCV genotype-1 patients, variations in efficacy according to patients’ underlying human genetic factors, no established efficacy for patients infected with other HCV genotypes, substantial tolerance issues, and dosing inconveniences. Thus, there is a continuing need for more consistently effective and better tolerated HCV inhibitors that can be orally administered in future combination therapies for hepatitis C patients worldwide, regardless of HCV genotype, patient genetic factors, or disease stage.

Inhibitors of the HCV NS5A protein represent an exciting, relatively new class of HCV inhibitors that, when optimized, exhibit potent activity across all HCV genotypes, with a mechanism that is distinct from other classes of HCV antivirals, which commonly target the HCV protease or polymerase. PPI-668 is a novel, optimized, second-generation HCV NS5A inhibitor, which exhibits highly potent and selective activity against all HCV genotypes in replicon assays, with favorable toxicology and pharmacology profiles in preclinical assessments.

ABOUT PRESIDIO

Presidio Pharmaceuticals, Inc. is a San Francisco-based clinical stage specialty pharmaceutical company dedicated to the discovery and development of small-molecule antiviral therapeutics for hepatitis C virus (HCV). For more information, please visit our website at: www.presidiopharma.com.

Source

New targets for antiviral therapy of chronic hepatitis C

New targets for antiviral therapy of chronic hepatitis C

Liver International

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Special Issue: Proceedings of the 5th Paris Hepatitis Conference. International Conference of the Management of Patients with Viral Hepatitis: Special Edition Hepatitis C

Volume 32, Issue Supplement s1, pages 9–16, February 2012

Keywords

• cyclophilin A;
• direct acting antiviral (DAA);
• miR-122;
• NS3 protease;
• NS5A protein;
• NS5B RNA-dependent RNA polymerase;
• phosphatidylinositol-4-kinase III alpha;
• STAT-C;
• sustained viral response

Abstract

1. Top of page
2. Abstract
3. Hepatitis C virus genome organization and replication cycle
4. Cell culture systems supporting self-replicating hepatitis C virus RNAs
5. Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)
6. Concluding remarks
7. Acknowledgements
8. Conflicts of interest
9. References

Until recently, chronic hepatitis C caused by persistent infection with the hepatitis C virus (HCV) has been treated with a combination of pegylated interferon-alpha (PEG-IFN) and ribavirin (RBV). This situation has changed with the development of two drugs targeting the NS3/4A protease, approved for combination therapy with PEG-IFN/RBV for patients infected with genotype 1 viruses. Moreover, two additional viral proteins, the RNA-dependent RNA polymerase (residing in NS5B) and the NS5A protein have emerged as promising drug targets and a large number of antivirals targeting these proteins are at different stages of clinical development. Although this progress is very promising, it is not clear whether these new compounds will suffice to eradicate the virus in an infected individual, ideally by using a PEG-IFN/RBV-free regimen, or whether additional compounds targeting other factors that promote HCV replication are required. In this respect, host cell factors have emerged as a promising alternative. They reduce the risk of development of antiviral resistance and they increase the chance for broad-spectrum activity, ideally covering all HCV genotypes. Work in the last few years has identified several host cell factors used by HCV for productive replication. These include, amongst others, cyclophilins, especially cyclophilinA (cypA), microRNA-122 (miR-122) or phosphatidylinositol-4-kinase III alpha. For instance, cypA inhibitors have shown to be effective in combination therapy with PEG-IFN/RBV in increasing the sustained viral response (SVR) rate significantly compared to PEG-IFN/RBV. This review briefly summarizes recent advances in the development of novel antivirals against HCV.

Chronic hepatitis C is a main risk factor for the development of serious liver disease including cirrhosis and hepatocellular carcinoma [1, 2]. An estimated 130–180 million people are persistently infected with the causative agent, the hepatitis C virus (HCV) that was molecularly cloned about 22 years ago [3]. With the implementation of blood tests to exclude HCV-containing samples, the incidence of HCV has dropped tremendously. However, most infections are asymptomatic and therefore diagnosed either by chance or at a time when chronic liver disease has already developed. Because of its high genetic variability, HCV is classified into seven different genotypes [4], which are predictive for successful therapy: infections with genotype 2 and 3 viruses are treated with a combination of pegylated interferon-alpha (PEG-IFN) with ribavirin (RBV) leading to a sustained viral response (SVR), i.e. absence of viral RNA 6 months or more after cessation of therapy) of about 85%. Although success rates are much lower in case of infections with genotype 1 and 4 viruses, the recent approval of the first HCV-specific directly acting antivirals (DAA) that are given in a triple combination with PEG-IFN/RBV has increased cure rates in genotype 1 naïve patients from around 55% to around 75%, at least under conditions of standardized clinical trials [5]. Given the large number of additional DAA that are currently being tested in clinical trials, it is expected that this number will increase further. Moreover, serious efforts are being made to develop an IFN-free therapy to reduce the numerous side effects caused by the systemic administration of this cytokine. This review briefly summarizes the molecular aspects of the viral prime targets including host cell factors that are required for efficient HCV replication.

Hepatitis C virus genome organization and replication cycle

1. Top of page
2. Abstract
3. Hepatitis C virus genome organization and replication cycle
4. Cell culture systems supporting self-replicating hepatitis C virus RNAs
5. Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)
6. Concluding remarks
7. Acknowledgements
8. Conflicts of interest
9. References

Hepatitis C virus is a small enveloped virus with a single stranded RNA genome of positive polarity belonging to the family Flaviviridae, genus Hepacivirus. Seven different genotypes are known that are differentiated based on a nucleotide sequence diversity of around 35% [4].

The replication cycle of HCV starts with the entry of the virus into its main target cell, the hepatocyte. Viral entry is a highly complex multi-step process initiated by binding of the envelope glycoproteins E1 and E2 to different host cell molecules that either ‘trap’ virus particles on the cell surface (e.g. heparan sulphate, low-density-lipoprotein receptor) or contribute to virus entry (CD81, occludin, scavenger receptor class B type I, claudin) [reviewed in [6]]. Virus spread occurs either via extracellular particles entering cells in a clathrin-dependent manner or via cell-to-cell spread, which appears to have different entry molecule requirements [7, 8, 9, 10]. After genome release into the cytosol, the viral RNA is translated via the internal ribosome entry site (IRES) residing in the 5′ nontranslated region (NTR). Translation generates a polyprotein that is cleaved by viral and cellular proteases into at least 10 different proteins (Fig. 1A). The first third of the genome encodes the proteins that are major constituents of virus particles, i.e. core, E1 and E2, or that are required for assembly and release of infectious particles, i.e. the viroporin p7 and the NS2 protease [11, 12, 13, 14, 15].

Figure 1. (A) A schematic representation of the hepatitis C virus (HCV) genome organization is shown in the top. The 5′ NTR – containing the internal ribosome entry site, IRES – and the 3′ NTR are indicated with thin lines and their proposed secondary structures. The polyprotein is given in orange with borders between the viral proteins indicated by vertical lines. Shown below is the structure of a selectable subgenomic replicon. It is composed of the HCV 5′ NTR containing the IRES, the selectable marker neo encoding for the neomycin phosphotransferase, which for cloning purposes is amino-terminally fused to 16 codons of the core coding region (C), the IRES of the encephalomyocarditis virus (EMCV), which directs translation of the HCV NS3 to NS5B polyprotein, and the 3′ NTR. (B) 3D structures of the three main viral drug targets: NS3/4A, NS5A and NS5B. The left panel shows a ribbon diagram of the crystal structure of full length NS3 in complex with the central NS4A protease activation domain (yellow). The protease (prot) domain (cyan) is located in the left. Side chain atoms of the catalytic triad amino acids (his-57, asp-81, ser-139) are represented as magenta spheres. Subdomains I, II and III of the helicase are coloured in silver, red, and blue respectively. Conserved sequence motifs involved in helicase activity are coloured in green. The blue stick structure represents the C-terminal segment of the helicase domain, which occupies the catalytic site of the protease subdomain. Note the linker that is part of subdomain I (given in silver) connecting the protease and the helicase domain. A ribbon diagram of the NS5A dimer [64] associated to a membrane via the N-terminal amphipathic -helix is shown in the middle panel. The three domains are given. Domains 1 (D1) of the two monomers form an RNA-binding cleft oriented towards the cytosol. D1 is composed of two subdomains (IA and IB); they are coloured in magenta and pink in one monomer and cyan and ice blue in the other monomer respectively. The zinc atoms of the zinc-binding motif in subdomain IA are shown as orange spheres. Domains 2 and 3 are intrinsically unfolded. The panel in the right shows the ribbon diagram of the NS5B RNA-dependent RNA polymerase catalytic domain [65, 66] complexed with UTP (stick structure in yellow) and Mn ions (magenta sphere). The triphosphate moiety of a nucleotide bound to the priming site is indicated by the stick structure in grey. The carboxy-terminal membrane anchor is not shown. The fingers, palm and thumb subdomains are coloured in blue, red and green respectively. The thumb subdomain β-loop contributing to template binding is given in orange. Shown structures are based on the following Protein Data Bank accession codes: 1CU1 for NS3, 1GX6 for NS5B, 1R7E for NS5A N-terminal membrane anchor, and 1ZH1 for D1 structure.

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At least five nonstructural (NS) proteins constitute the HCV replicase [reviewed in [16]]:

1. NS3, a multi-functional enzyme with an amino-terminal serine protease domain and a carboxy-terminal RNA helicase/NTPase domain (Fig. 1B).
2. NS4A, a co-factor of the NS3 protease forming a stable heterodimeric NS3/4A complex (Fig. 1B).
3. NS4B, the presumed central organizer of the HCV replicase complex and a main inducer of intracellular membrane rearrangements.
4. NS5A, an RNA-binding phosphoprotein required both for RNA replication and assembly of infectious virus particles (Fig. 1B).
5. NS5B, the RNA-dependent RNA polymerase catalysing the amplification of the viral RNA genome (Fig. 1B).

The newly synthesized positive-strand RNAs, which are transcribed from negative-strand RNA intermediates, serve as templates for RNA translation or for negative-strand RNA synthesis. Alternatively, positive-strand progeny is used for the assembly of infectious virus particles via a process that is tightly linked to cytosolic lipid droplets and the very-low-density lipoprotein (VLDL) pathway [reviewed in [17]].

Cell culture systems supporting self-replicating hepatitis C virus RNAs

1. Top of page
2. Abstract
3. Hepatitis C virus genome organization and replication cycle
4. Cell culture systems supporting self-replicating hepatitis C virus RNAs
5. Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)
6. Concluding remarks
7. Acknowledgements
8. Conflicts of interest
9. References

It took more than 10 years from the first molecular cloning of the HCV genome up to the establishment of the first robust cell culture system, which was initially based on self-replicating HCV mini-genomes, called replicons [18]. They were derived from a molecular genotype 1b consensus genome by replacing the region encoding core to NS2 by the selectable marker neomycin phosphotransferase (neo) conferring resistance against the cytotoxic drug G418 (Fig. 1A). Synthetic RNA derived from the cloned DNA copy of such a ‘selectable’ replicon was transfected into cells of the human hepatoma cell line Huh7 that were subsequently cultured in G418-containing medium. Only cells in which the replicon amplified to high levels could survive and, indeed, several G418-resistant cell colonies were obtained containing high amounts of viral RNA and proteins. The exceptionally high level RNA replication was attributable to the selection for both more permissive Huh7 cell clones and the accumulation of cell culture adaptive mutations enhancing RNA synthesis [reviewed in [19]]. Owing to its high efficiency, the replicon system became accepted as an important tool to study the molecular mechanisms of HCV RNA replication. Importantly, the replicon system provided the first functional cell-based platform for screening of antiviral agents targeting HCV RNA replication and for validation of compounds directed against recombinant viral enzymes.

The major drawback of the HCV replicon system was its limitation to the intracellular steps of the viral replication cycle whereas production of infectious virus particles could not be achieved [21, 22]. This was because of an interference of replication enhancing mutations with the assembly process of HCV particles [22]. A major breakthrough was therefore the identification of a genotype 2a isolate that was cloned from a patient with fulminant hepatitis and that was replicated to high levels without requiring adaptive mutations [23]. This isolate, designated JFH-1 (an acronym derived from Japanese patient with fulminant hepatitis) supports virus production and cell culture-produced particles that are infectious in vivo[24]. This new HCVcc (cell culture) system thus closes the gaps of the replicon system and recapitulates the complete viral replication cycle that can now by targeted at any step (see Table 1).

Table 1. Hepatitis C virus (HCV) proteins and their use as antiviral drug targets

HCV protein	Function in the HCV replication cycle	Development of inhibitor
Core + 1; mini-cores	?	No
Core	Viral capsid protein; RNA-binding	Yes; pre-clinical
E1	Envelope glycoprotein	Yes; e.g. neutralizing antibodies against E1, and E2; neutralizing antibodies or compounds targeting cellular receptors [reviewed in [6]]
E2	Envelope glycoprotein; receptor binding
p7	Viroporin; assembly and release	Yes; various inhibitors [reviewed in [67]]
NS2	Cysteine protease; assembly	No
NS3	Serine protease; helicase	Yes; multiple compounds including two approved drugs [reviewed in [68]]
NS4A	Co-factor of the NS3 protease	Yes, e.g. ACH-1095 (http://www.achillion.com/HCV-overview)
NS4B	Induction of membrane rearrangements; main organizer of membranous HCV replication complex	Yes; e.g. clemizole [69]
NS5A	RNA replication and assembly	Yes; two inhibitor classes [34, 35]
NS5B	RNA-dependent RNA polymerase	Yes; NI and NNI [reviewed in [70]]

Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)

1. Top of page
2. Abstract
3. Hepatitis C virus genome organization and replication cycle
4. Cell culture systems supporting self-replicating hepatitis C virus RNAs
5. Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)
6. Concluding remarks
7. Acknowledgements
8. Conflicts of interest
9. References

Inhibitors of the NS3/4A protease

As protease inhibitors were successfully developed for treatment of HIV infections, soon after the first molecular cloning of the HCV genome most efforts focused on the development of inhibitors of the HCV NS3 serine-type protease. In spite of its unfavourable overall structural features, especially the rather shallow and solvent-exposed substrate-binding pocket, potent inhibitors could be developed. They were based on the observation that after cleavage the P-side product remains bound in the substrate-binding cleft and causes an auto-inhibition [reviewed in [25]]. Thus, P-side derived peptidic inhibitors were developed, including the macrocyclic tripeptide BILN 2061 that was successfully tested in a clinical trial in 2003. Administration of BILN 2061 to patients infected with HCV genotype 1 for 2 days resulted in an impressive reduction of HCV RNA plasma levels, thus providing proof-of-concept that the NS3/4A protease is a valid drug target [26]. However, owing to toxicity in animals this compound was not pursued further.

As described above, two NS3 protease inhibitors have recently been approved: boceprevir (SCH 503034) and telaprevir (VX-950). Their use in combination with PEG-IFN/RBV increases SVR to around 75% in naïve patients infected with genotype 1 virus. However, these drugs also cause side effects such as rash and anaemia leading, e.g. in case of telaprevir in around 15% of cases to discontinuation of therapy [27]. Moreover, these first generation DAA require rather complex treatment regimens such as strict time schemes when the drug must be taken (three times a day every 7–9 h), or a high load of pills, thus reducing adherence.

A main problem of the recently approved DAA telaprevir and boceprevir is the rapid selection for drug resistant HCV variants, which is a particular concern for patients with poor response to PEG-IFN/RBV [27, 28]. Importantly, several of these mutations confer cross resistance to other protease inhibitors [reviewed in [29]]. For instance, the following resistance mutations have been reported with telaprevir (numbers in parenthesis refer to fold shift of the IC₅₀ of the mutant as compared to the wild type): V36A/M/C (3.5- to 7-fold); T54A/S (6- to 12-fold); R155K/T/Q (8.5- to 11-fold); V36A/M + R155K/T (57- to 71-fold); A156V/T (74- to 410-fold); and V36A/M+A156V/T (>781-fold) [reviewed in [29]]. Interestingly, in case of R155K, only one nucleotide change is required for this amino acid substitution with genotype 1a, although two nucleotide changes are required with genotype 1b. This explains why the R155K variant is frequently found in treated patients with a genotype 1a virus infection whereas in genotype 1b patients this variant is virtually absent.

As shown with the R155K mutation, which drastically reduces replication capacity when introduced into a subgenomic replicon, resistance mutations often impair viral fitness [30]. However, during therapy second site mutations are selected that restore fitness, explaining why the R155K primary mutation is frequently found in association with V36M in case of genotype 1a viruses. Obviously proper management protocols have to be established to monitor HCV drug resistance. Moreover, guidelines have been drafted that recommend strict stop rules in case of patients with viral breakthrough and (proven) adherence to therapy. The main concern is the selection for highly replication competent variants that are resistant to the used drug. These variants are probably persistent for a very long time and therefore difficult to eradicate. Moreover, in principle these variants can be transmitted to other individuals thus acquiring a drug resistant isolate.

Inhibitors of the NS5B RNA-dependent RNA polymerase

Another important drug target for development of DAA is the NS5B RNA-dependent RNA polymerase (Fig. 1B). Inhibitors of this enzyme can be classified into two groups: Nucleosidic inhibitors (NI) and non-nucleosidic inhibitors (NNI). NIs are nucleotide analogues and incorporated by the NS5B polymerase into the nascent RNA. Owing to the lack of a proper 3′ OH-group that is used as acceptor for the 5′ phosphate group of the incoming NTP, incorporated NIs cause chain termination. As the active site of the polymerase is highly conserved between different genotypes, NIs are likely to act across different genotypes. NIs also have a high genetic resistance barrier and only a few resistance mutations were found in vitro. For example, the resistant variant S282T was selected in cells treated with the NI RG7128. The position of this amino acid substitution is in close vicinity to the catalytic site of the NS5B polymerase and is conserved across all genotypes with the exception of the genotype 4a isolate ED43 [reviewed in [31]]. Importantly, the resistance mutation S282T causes a dramatic loss of viral fitness without having much effect on drug activity. It is therefore unlikely that this mutation will be selected in patient populations. Indeed, resistance was not observed in patients treated with RG7128 monotherapy for 2 weeks [32]. Several NIs are currently under development in phase II clinical trials (e.g. RG7128 by Roche and Pharmasset; PSI-7977 by Pharmasset; IDX184 by Idenix). Moreover, because of the superior resistance profile, a clinical trial has been started by combining two NIs with or without RBV to determine whether or not PEG-IFN-free therapy is possible using NIs alone.

In contrast to NI, NNIs of the NS5B polymerase have a low genetic resistance barrier. Substances of this class bind to one of at least four allosteric sites within NS5B leading to inhibition of the enzyme and thus a block of viral RNA synthesis. Because of their rather low clinical efficacy and the rapid selection for resistant variants, the clinical use of NNIs may be limited. Nevertheless, several NNIs are currently being tested in phase II clinical trials and it remains to be determined what role this class of compounds might play in the future [reviewed in [33]].

Inhibitors of the NS5A replicase protein

Attributable to its poorly characterized role in HCV RNA replication and the lack of enzymatic activity, NS5A has long been neglected as a primary drug target. However, by using replicon-based screens and subsequent intensive chemical refinements of primary hits, a highly active compound (BMS-790052) characterized by its symmetric structure was identified [34]. This compound has an amazingly high potency with antiviral efficacy in the picomolar range. In fact, it has been calculated that one inhibitor molecule can block 10–100 NS5A molecules, arguing that BMS-790052 might exert a ‘dominant negative’ phenotype. This high potency was well recapitulated in a phase I clinical trial with chronic hepatitis C patients; a single application of 100 mg BMS-790052 reduced viral load around 1000-fold within 24 h after application [34].

The mode of action of this drug class is unknown and is an area of intense research [34, 35, 36]. Biochemical studies suggest that the compound directly binds to NS5A and resistance analyses have identified mutations in domain I of NS5A, arguing for direct inhibition of NS5A function(s) (Fig. 1B). However, because of the multiple roles of this protein in the HCV replication cycle and the numerous cellular interaction partners, viral replication might be indirectly blocked, e.g. by inhibiting an interaction with an important host cell factor. Alternatively, oligomeric complexes might form within an infected cell and binding of the compound to one NS5A molecule may disturb formation of such a large complex, which would explain the dominant negative phenotype of the compound. The NS5A inhibitors, like NNIs and NS3 protease inhibitors, cause rapid selection for antiviral resistance. Several resistance mutations have been identified residing either in domain 1 (e.g. Y93H/C/W) or in the linker region connecting the amino-terminal amphipathic -helix with domain 1 [35]. Although some of these mutations reduce the antiviral efficacy of BMS-790052 around 1800-fold (Y93C) or even 3400-fold (L31V), because of the extremely high potency of this compound, the EC₅₀ is still in the nanomolar range even for these resistance mutations.

Inhibitors targeting host cell factors required for hepatitis C virus replication

As HCV is an obligate intracellular parasite, its replication relies heavily on the host cell environment. Thus, cell factors promoting HCV replication (so-called ‘dependency’ factors) are an alternative target for antiviral therapy. It is assumed that cellular targets might be superior, because they should lower the risk for selection of resistance mutants. Moreover, host cell factors are well conserved and therefore, drugs interfering with such factors should be active across different genotypes.

The most advanced cellular drug targets for therapy of chronic hepatitis C are cyclophilin A (CypA) and micro-(mi)RNA-122. Cyclophilins are molecular chaperones catalysing the cis-trans isomerization of proline residues and are therefore called peptidyl-prolyl cis-trans-isomerases (PPIases). Seven different Cyp isoforms have been identified in humans. Pharmacological inhibition of cyclophilins by the immunosuppressive drug cyclosporine A (CsA), causes profound inhibition of HCV replication [37]. The underlying mechanism by which cyclophilins contribute to viral replication is still not known. It is assumed that CypA binds to NS5A and might induce a conformational change leading to an activation of the viral replicase [38, 39, 40, 41]. There is also evidence that CypA might also be required for NS2 folding or activity, but this remains to be determined [38, 42].

The inhibition of replicons by CsA on one hand, and the strong immunosuppressive effect of this drug on the other hand, led to the development of CsA analogues that retained CypA binding, but lost binding to calcineurin, which is responsible for the immuno-suppressive effect. One of these derivatives, DEBIO-025 (alisporivir) has shown great promise in clinical trials in combination with PEG-IFN/RBV [43, 44]. Moreover, a recent pilot study with genotype 3-infected patients suggests that even short-term monotherapy might be sufficient to achieve SVR [45].

In hepatocytes, the accumulation of unfolded proteins in the endoplasmic reticulum (ER) causes ER stress and the unfolded protein response (UPR), mediated by the ER-resident stress sensors ATF-6, IRE1 and PERK. UPR-responsive genes are involved in the fate of ER-stressed cells. Cells carrying HCV subgenomic replicons exhibit in vitro ER stress and suggest that HCV inhibits the UPR. In vivo, liver from patients with untreated CHC exhibit in vivo hepatocyte ER stress and activation of the three UPR sensors without apparent induction of UPR-responsive genes [46]. This lack of gene induction may be explained by the inhibiting action of HCV per se (as suggested by in vitro studies) and/or by our finding of the localized nature of hepatocyte ER stress. Autophagy is a regulated process that can be involved in the elimination of intracellular microorganisms and in antigen presentation. Some in vitro studies have shown an altered autophagic response in HCV-infected hepatocytes. In vivo, autophagy is altered in hepatocytes from CHC patients, likely caused by a blockade of the last step of the autophagic process [47].

It has been reported that the addition of an inhibitor of cyclophilins, cyclosporine A, reduced the activity of autophagy induced by nutrition starvation [48]. Interestingly, Ke et al. described a new role of autophagy in the regulation of innate immunity during HCV infection [49]. HCV may encode an NS3/4A independent activity that triggers autophagy to limit the production of IFNB. Therefore, cyclophilin inhibitors might act as a potent anti-autophagy agent and limit both inhibition of innate antiviral response and HCV replication [50].

MicroRNAs (miRNAs) are a class of small non coding RNA molecule of 20–22 nucleotides that control gene expression by targeting mRNAs for transcriptional repression or cleavage. They are involved in the regulation of crucial cellular mechanisms such as development, cell differentiation, proliferation and apoptosis. The importance of the miRNAs machinery in HCV replication has been recently described in various studies [reviewed in [51]].

Recently, micro-(mi)R-122 was identified as an essential HCV dependency factor [52]. Expression of this micro-RNA is liver-specific. Its mode of action is still under debate, but miR-122 appears to promote HCV replication in several ways. First, it was shown to enhance HCV RNA translation by enhancing the association of ribosomes with the viral RNA at an early initiation stage [53]; second, it may mask the 5′ triphosphate end of the HCV genome, thus impairing recognition by intracellular RNA sensors such as RIG-I [54, 55]; third, miR-122 promotes RNA replication by an as yet unknown mechanism. Importantly, studies in the chimpanzee animal model demonstrated proof-of-concept that sequestration of miR-122 with chemically modified antagonists dampens HCV replication indicating that miRNAs might be a novel therapeutic target [56].

Another, more recently identified HCV dependency factor is phosphatidylinositol 4-kinase type III- (PI4KIII-) that has been identified in several independent siRNA-based screenings [9, 57, 58, 59, 60]. It was shown that PI4KIII- is required for structural integrity of the membranous HCV replication complex. The enzyme is recruited to the sites of viral replication via an interaction with domain I of NS5A triggering an activation of PI4KIII-, which in turn leads to a massive accumulation of PI4-phosphate at intracellular membranes where HCV RNA replication occurs [57, 61]. Pharmacological inhibition of PI4KIII- results in’a massive decrease of HCV RNA replication making this kinase a promising target for therapeutic intervention.

Concluding remarks

1. Top of page
2. Abstract
3. Hepatitis C virus genome organization and replication cycle
4. Cell culture systems supporting self-replicating hepatitis C virus RNAs
5. Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)
6. Concluding remarks
7. Acknowledgements
8. Conflicts of interest
9. References

The ideal future therapy of chronic hepatitis C should fulfil at least four criteria. First, it should be IFN-free to reduce side effects and contraindications; second, it should impose a high barrier of drug resistance; third, it should require only short treatment duration; forth, SVR should be as high as possible, ideally greater than 90%. Initial clinical studies have shown that IFN-free therapy is possible in principle [62, 63]. Gane and colleagues have conducted a clinical trial (INFORM-1) based on a combination of two DAA: [1] RG7128, a NI with a high resistance barrier and [2] Danoprevir, a protease inhibitor with a low resistance barrier [62]. Patients infected with genotype 1 viruses were treated for 14 days and showed a marked decrease in viral load. Viral breakthrough could not be detected. The combination therapy was well-tolerated by patients and discontinuation was not observed. Together with other clinical data this study shows great promise that IFN-free therapy of chronic hepatitis C is not a fiction, but might become reality in the not too distant future.

Acknowledgements

1. Top of page
2. Abstract
3. Hepatitis C virus genome organization and replication cycle
4. Cell culture systems supporting self-replicating hepatitis C virus RNAs
5. Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)
6. Concluding remarks
7. Acknowledgements
8. Conflicts of interest
9. References

We are grateful to Francois Penin for providing the 3D structures shown in Figure 1B. Work in the authors’ laboratory was supported by the Deutsche Forschungsgemeinschaft, FOR1202, TP1 and the European Union, European Training Network on (+)RNA Virus Replication and Antiviral Drug Development (EUVIRNA), grant number: 264286.

Conflicts of interest

1. Top of page
2. Abstract
3. Hepatitis C virus genome organization and replication cycle
4. Cell culture systems supporting self-replicating hepatitis C virus RNAs
5. Specifically targeted antiviral therapy for hepatitis C virus (STAT-C)
6. Concluding remarks
7. Acknowledgements
8. Conflicts of interest
9. References

The authors have not declared any conflicts of interests.

References

Watch-The Coming of Age of Direct Anti-Viral Agents for HCV

For many patients with Hepatitis C, direct anti-viral agents offer a potential cure. Marion Peters, MD discusses advances in this treatment.

Series: "UCSF Transplant Update" [1/2012] [Health and Medicine] [Professional Medical Education] [Show ID: 23242]

Market Update-The Quest For The Ideal Hepatitis C Therapy

The Hepatitis C Market: Biotech’s Version of the Daytona 500

Luke Timmerman12/12/11

Biotech rivalries are sometimes a bit like boxing matches, where you have two lone fighters vying for the prize. But the hepatitis C market is turning into a battle royal that’s more wide open and unpredictable, with all the competitive maneuvering, surprise crashes, and comebacks you might expect from the Daytona 500.

The medical advances in hepatitis C have been dizzying this year, especially in what it means in terms of multi-billion dollar business implications. The safest thing to say is that there’s plenty of good news for patients this year, but that shareholders in the major hepatitis C drug developers had better hold on tight as a new standard of care gets established.

Some commentators figured that Gilead Sciences (NASDAQ: GILD), the world’s biggest maker of HIV drugs, had essentially locked up the dominant position in this new drug class through its $11 billion acquisition last month of Princeton, NJ-based Pharmasset (NASDAQ: VRUS). But it’s still too soon for anyone to declare victory over the wily and fast-mutating virus that causes hepatitis C. Given the way drug development is going now, it’s possible we could have dueling antiviral drug cocktails that cure almost 100 percent of patients within five years. And before we get there, we’re going to see some fascinating chess moves—and probably a few surprising collaborations—from companies like Vertex Pharmaceuticals, Merck, Roche, Johnson & Johnson, Bristol-Myers Squibb, and Abbott Laboratories, as well as several smaller biotech startups like Alpharetta, GA-based Inhibitex (NASDAQ: INHX).

The Pharmasset compound that prompted Gilead to write such a big check, PSI-7977, is “certainly not a panacea, not the lone answer,” says Kleanthis Xanthopoulos, the CEO of San Diego-based Regulus Therapeutics, and the co-founder of another hepatitis C drug developer, Anadys Pharmaceuticals.

Xanthopoulos says Gilead was “taken to the cleaners,” and that the hepatitis C market is still up for grabs. “It’s going to take some time before people figure out how it plays out,” he says. The Pharmasset drug “is a powerful player, but you will need other direct-acting antivirals. You want to go to a 100 percent cure rate. I can guarantee the Pharmasset compound isn’t going to do it alone.”

Hepatitis C has never really captured big headlines in the U.S., as it has never benefitted from massive awareness boosting campaigns that have supported research for, say, HIV, or breast cancer. But hepatitis C has clearly emerged as one of the biggest opportunities in pharmaceuticals over the past few years. There are more than 3 million people in the U.S., and an estimated 170 million worldwide, with this liver infection that can lead to cirrhosis and liver cancer. Most people have never bothered to get treated, partly because the infection takes years to fully wreak havoc. The other reason is the standard of care with a combination of drugs—pegylated interferon alpha and ribavirin—causes flu-like symptoms that last for almost a year, and usually cures only 30-40 percent of patients. Essentially, most people figure the treatment is worse than the disease.

Vertex Pharmaceuticals changed the equation back in May. The company won FDA approval for a direct antiviral drug, a protease inhibitor called telaprevir (Incivek), that is added to the usual two-drug combo regimen. By adding the Vertex drug, researchers saw the cure rate boom to almost 80 percent of patients, while cutting the treatment time with the other drugs in half. The Vertex drug also significantly raised the cure rate for patients who failed to respond to prior rounds of therapy.

Vertex looked golden for a while, as its stock soared above $55 a share, sending its market value above $10 billion. Analysts were raving about how Vertex smashed sales expectations in its first few months on the market, and started turning profitable in just its second quarter of selling the drug. Waves of patients were suddenly showing up at doctors’ offices to get treatment for hepatitis C, now that the odds of a cure were so much higher.

But important as the Vertex advance has been, researchers have made it clear that this story isn’t over. The ultimate goal is to get rid of interferon, and its side effects, so that physicians can count on some combination of direct antivirals that can be taken as oral pills. That might include Vertex’s drug in combination with others, or might not.

So that’s why Vertex, and other companies, have feverishly been looking to mix and match various hepatitis C drugs. It’s all part of a quest to come up with the ideal combo that can raise the bar on cure rates, minimize side effects, and maximize convenience.

While people on Wall Street like to embrace a simple storyline with clear winners and losers, the hepatitis C virus is one tricky adversary. Like HIV, it has a tendency to mutate and develop resistance capabilities, whenever scientists throw a new antiviral drug against it. So there isn’t likely to be a single magic bullet. The most likely route to success is with a combination of two, three, or maybe four antiviral drugs that attack the virus from different angles, making it much harder for the bug to mutate and escape one drug.

As Steve Worland, the CEO of San Diego-based Anadys Pharmaceuticals, put it in a guest editorial for Xconomy in September, there are at least four important categories of hepatitis C antivirals. There are protease inhibitors on the market like Vertex’s drug and Merck’s boceprevir (Victrelis). There are nucleotide polymerase inhibitors like Pharmasset’s PSI-7977 and a rival drug called mericitabine from Roche. There are non-nucleotide polymerase inhibitors in the works from Abbott Laboratories, Vertex, and Anadys (which Roche acquired this fall for $230 million.) And Bristol-Myers Squibb is betting on another kind of compound, an NS5A inhibitor. (You could also count microRNA therapies, which Santaris Pharma and Regulus are working on at earlier stages of development.)

Just this year, we’ve seen some fascinating jockeying for position. Drug companies often don’t like to test combinations of experimental drugs together in clinical trials, because when side effects emerge, people often like to point the finger at the other guy’s drug. And who wants to divvy up the profits with some other pharma giant when you have the whole thing yourself?

But with hepatitis C, the market opportunity is so big, and the variety of drugs to attack it is so broad, that pharma companies have set aside those concerns just to get a piece of the action. We’ve already seen Merck and Roche form a partnership to co-market Victrelis against the leading drug on the market from Vertex. Gilead just shelled out the breathtaking sum of $11 billion for Pharmasset, even though the smaller company’s lead compound still has to navigate the third and final phase of clinical trials required for FDA approval. Bristol-Myers Squibb and Johnson & Johnson have teamed up in an interesting new collaboration. Roche, through internal efforts and acquisitions, has sought to put all the pieces of the puzzle together under one roof—a protease inhibitor, a nucleotide polymerase inhibitor, a non-nucleotide polymerase inhibitor.

Nobody knows which compounds will match up best together, which ones will be too toxic in combination, or even how many antivirals will be needed to raise the cure rate. But it’s worth noting that Vertex raised the bar very high, by getting cure rates up to around 80 percent. Doctors are certainly eager to get rid of the nasty interferon part of the regimen, but they will only do that when a new regimen can do at least as well on cure rates. And any of these drugs can be derailed by somewhat mild side effects, since the bar on safety is set quite high already.

It might be relatively safe and simple to declare Gilead/Pharmasset the winners in this market, but this race isn’t even close to over. There are 200 laps in the Daytona 500, and in the hepatitis C race, I’d say we’re at about lap 50. There are going to be some fascinating strategic maneuvers, and maybe even a spectacular crash or two, before somebody zooms in under the checkered flag.

Blog Updates;

Novel Interferon-Free Hepatitis C Regimen Promising

Audio-Interferon-Free Regimens for Hepatitis C: Are We There Yet?

Hepatitis News Ticker-Boceprevir Case Study

Today @NATAP

Boceprevir Case Study -

Case Scenario

A 52-year-old male executive who is asymptomatic is evaluated for abnormal liver biochemical tests. The aspartate aminotransferase level is 138 U/L, and the alanine aminotransferase level is 164 U/L; the bilirubin, alkaline phosphatase, and albumin levels and the complete blood counts are normal. The international normalized ratio is 1.1, and the serum creatinine level is 0.9 mg/dL. The hepatitis C virus (HCV) RNA level is 1,600,000 IU/mL, and the genotype is 1B. The patient has read about boceprevir and wants to know whether he is a candidate for treatment with this drug. He also wants to know whether he really requires liver biopsy before the initiation of treatment.

Will you use boceprevir in this patient? How will you determine whether he is responding to the drug, how long will you give him the medication, and how will you monitor him for side effects? How will you determine that treatment-related anemia is related to boceprevir and is not related to ribavirin? Which side effects of boceprevir will warrant the discontinuation of treatment? Will your approach vary with the genotype for the interleukin-28 (IL-28) polymorphism?..Continue Reading..

PSI-7977 400 mg with PEG/RBV Provides 93% SVR Across HCV GT 1, 2 and 3 - (12/05/11)

NS5A HCV Drug Study Results, Genotypic and phenotypic analysis of variants resistant to hepatitis C virus nonstructural protein 5A replication complex inhibitor BMS-790052 in Humans: In Vitro and In Vivo Correlations - (12/05/11)

Surveillance for hepatocellular carcinoma: A standard of care, not a clinical option - editorial - (12/05/11)

Ultrasonographic surveillance of hepatocellular carcinoma in cirrhosis: A randomized trial comparing 3- and 6-month periodicities - (12/05/11)

Feasibility of conducting a randomized control trial for liver cancer screening: Is a randomized controlled trial for liver cancer screening feasible or still needed? 'informed patients prefer surveillance' - (12/05/11)

The green tea polyphenol, epigallocatechin-3-gallate, inhibits hepatitis C virus entry - (12/05/11)

AASLD: Lack of Effect of the Nucleotide Analog Polymerase Inhibitor PSI-7977 on Methadone PK and PD - (12/05/11)

AASLD: PSI-7977 Has No Effect on QTcF Intervals at Therapeutic or Supratherapeutic Doses - (12/05/11)

hepDART: PSI-7977 400 mg with PEG/RBV Provides 93% SVR Across HCV GT 1, 2 and 3 (12/05/11)

hepDART: PSI-7977 with PEG/RBV Elicits Rapid Declines in HCV RNA in Patients with HCV GT-4 and GT-6 (12/05/11)

View all updates @ NATAP Here


Update @ Medscape

Bile Acid Retention and Antiviral Response in Chronic HCV
How do bile acids potentially alter the effectiveness of antiviral drugs in the treatment of hepatitis C?
Journal of Viral Hepatitis, December 2011

Discussion Only
Click Here For Full Text

In hepatitis C-infected patients, sustained response (SVR) to antiviral therapy with PEG-interferon and ribavirin depends on both viral and host characteristics.^[4] Besides HCV genotype and baseline viral load as viral factors, several patient-based factors are related to reduced response rates including age, gender, ethnicity, coinfection with human immunodeficiency virus, liver cirrhosis, obesity and alcohol intake.^[4] Baseline clinicochemical parameters and viral dynamics during therapy can help to predict the patients probability of response.^[5] Previous observations in small and heterogenous HCV populations with different, inferior treatment regimens indicate that accumulation of bile acids, particularly in combination with elevated ferritin levels, may be a negative prognostic marker to predict sustained virus response.^[8,9] Recently, in vitro studies demonstrated an activation of HCV replication by bile acids via a FXR-dependent mechanism.^[6,7] Consequently, the present study investigated the effects of bile acid levels and a related gene polymorphism in a large and well-defined cohort of hepatitis C patients who were invariably treated with a standard PEG-interferon/ribavirin regimen. This work analysing a combination of two large cohorts presents several new findings: (i) A slight but significant difference in the frequency of the ABCB11 1331CC genotype in patients with CHC compared to healthy subjects may be a hint towards a potential causal role of increased hepatocellular bile acids as a host factor to develop HCV chronicity. (ii) Regarding standard PEG-interferon/ribavirin treatment, bile acid levels >8 μm affect the response to antiviral treatment only in genotype 2/3 patients, whereas elevated GGT levels selectively predict non-SVR in the genotype 1 subgroup. (iii) In contrast to in vitro studies, no effect of bile acid levels on HCV viral load can be observed in vivo.

In previous genetic studies, the common ABCB11 1331T>C polymorphism has been associated with increased susceptibility for cholestatic diseases including ICP and drug-induced cholestasis.^{[11,12,17,19]} Recently, comprehensive analysis of ABCB11 missense mutations and single-nucleotide polymorphisms demonstrated aberrant pre-mRNA splicing and protein processing/function as a cause for significant deficiency of BSEP.^[20] Particularly, the ABCB11 1331T>C polymorphism which is encountered in about half of the Caucasian population has been associated with reduced expression levels of the mature BSEP protein.^{[11,12,17,20]} However, in this study, mean bile acid levels in patients with CHC carrying the 1331CC genotype were only marginally elevated. This finding reflects the fact that bile acid retention is mostly caused by the coincidence of acquired factors such as hepatic inflammation in addition to genetic predisposition.

In line with observations from other cohorts,^[8,9] patients with CHC experiencing SVR had significantly lower bile acid concentrations than those with non-SVR. Owing to the large number of patients in our study, significant differences in therapy response according to bile acid levels could be detected for a combined HCV genotype 2/3 subgroup and with marginal statistical significance also for genotype 1 patients (Fig. 1). To investigate the discriminatory power of bile acid reference values for the prediction of treatment outcome, bile acid levels were categorized in normal (≤8 μm) vs elevated (>8 μm) with significant differences in SVR for HCV genotype 2 and 3 patients (P = 0.002) and marginal significance for genotype 1 (P = 0.058) (Fig. 2). ROC analysis indicates a fairly good sensitivity and specificity for bile acid levels of >8 μm to predict sustained virus response (AUC = 0.80) in these patients. Multivariate analysis demonstrates a significant increase in SVR for HCV-patients with normal bile acid levels irrespective of the HCV genotype (OR 1.66 for all HCV genotypes; OR 2.54 for HCV-2/3) while an association between SVR and presence of the ABCB11 1331C allele was only detectable in the subgroup of HCV genotype 2 and 3 infected patients (OR 2.94) but not for genotype 1 (Fig. 4; Table 2). The influence of bile acids and the ABCB11 genotype on SVR appears to be independent from the IL28B rs12979860 genotype because the former significantly affects SVR only HCV genotypes 2 and 3 while the latter exclusively influences genotype 1.^[22] All results of the combined genotype 2/3 group could be confirmed in a subgroup analysis for HCV genotype 3 patients alone, whereas this analysis was impossible for HCV genotype 2 because of the limited number of nonresponders (n = 4) in this subgroup.

The molecular mechanism by which bile acids affect SVR to antiviral therapy in the patient is still unknown. As one potential pathophysiological explanation, bile acids may interfere with the antiviral effect of interferon in vivo similarly to in vitro findings in GS4.1 and HG23 cells using the replicon system.^[6,7] Yet in vitro data from the replicon system regarding increased HCV RNA levels in response to bile acids have to be interpreted with respect to inherent genotype-specific differences in replication efficiency.^[6,7] The underlying mechanism is not necessarily FXR-dependent, because bile acids may also activate MAPK pathways through TGR5, a G protein–coupled membrane receptor for bile acids,^[23] thus increasing intracellular cAMP levels and inhibiting the activation of signal transducer and activator of transcription 1 (STAT1) by type I interferons. In fact, bile acid-mediated down-regulation of STAT1 has been described as essential for porcine enteric calicivirus replication.^[24] Recent HCV-human protein interactome analysis revealed HCV core interaction with several proteins involved in the Jak/STAT pathway thereby explaining interferon-α resistance.^[25]

Comparing patients with chronic HCV infection and healthy individuals discloses a slight but still significant difference in the frequency of the ABCB11 1331CC genotype within these groups. This finding fuels the speculation that increased bile acid levels may play a causal role for a susceptibility to develop chronic HCV infection because of an impaired endogenous interferon response during the acute phase of infection. These findings are also in line with an established negative effect of bile acids on interferon signalling and the induction of proteins involved in the antiviral activity in cell culture studies.^[26] The assumption that bile acids rather influence the interferon response than the viral replication itself is also supported by the absent correlation of viral RNA load and bile acid levels in this study (Figure S3).

Although differences in response to interferon therapy between HCV genotypes have been described extensively,^[1,3,4] only very few data on distinctions with regard to viral biology in vivo exist. The strong association of bile acids with interferon response in patients with HCV genotype 2 and 3 but only weaker in genotype 1 clearly highlights the complexity of host–virus interaction, and obvious differences between HCV genotype 1 and genotype 2/3 biology both warranting more genotype-directed study in the future.

In this context, the fact that elevated GGT has been identified as a predictor for negative therapy outcome only in HCV genotype 1 patients is remarkable, because no such association can be observed for genotype 2 and 3 (Fig. 3). Our data are in line with a recent study identifying low GGT levels as predictor for SVR in patients with HCV genotypes 1, 4 and 6 infection in contrast to those with genotypes 2 and 3^[5] and highlight again biological differences within different genotypes. One reason for non-SVR in HCV genotype 1–infected patients with increased GGT levels may consist in the fact that increased serum GGT concentration is associated with nonalcoholic steatosis but interestingly not with cholestasis in patients with CHC.^[27] Such a link is further supported by the recent DITTO trial.^[21,28] Interestingly, steatosis negatively affected the final outcome of treatment mainly in patients infected with HCV genotype non-3 in this study. From our data, it is attractive to speculate that particularly HCV genotype 3 response is modulated by cholestasis with bile acid retention, whereas HCV genotype 1 response is negatively altered by steatosis and associated conditions such as redox stress.

In summary, we show that bile acids may play a role as a host factor affecting response to antiviral therapy in HCV genotype 2/3, whereas only weak association was found for HCV genotype 1 patients. In contrast to the results of previous in vitro studies, no effect of bile acid levels on viral load could be observed.

Hepatitis A, B Susceptibility High in Patients on Methadone
Coinfection with hepatitis C carries extra risks; the high rates underscore the need to vaccinate those in drug treatment programs.

Medscape Medical News, December 2, 2011

In The News


Over 200 test positive for hepatitis C virus

2011-12-03 09:20:12 GMT2011-12-03 17:20:12
(Beijing Time) Xinhua English

HEFEI, Dec. 3 (Xinhua) -- More than 200 villagers, many of them children, have been found infected with hepatitis C virus (HCV) in east and central China over the past two weeks, with the reuse of old needles by a rural clinic suspected as the cause.

From Nov. 17 to Dec. 1, 105 people from the Dancheng township of Woyang county in the eastern province of Anhui tested positive for the disease, a spokesman with the Woyang Health Bureau said Saturday.

But no serious cases have been reported, he said.

Earlier, 104 people in the neighboring Maqiao township of Yongcheng city in central province of Henan had also tested positive for the virus, and six of them had been confirmed as HCV patients.

Investigators are focusing on a doctor at a privately-run village clinic in Maqiao. Wu Wenyi, 60, is suspected of causing the infection by reusing old needles.

Local residents said Wu, a village doctor for four decades, seldom changed needles, and is known as the "miracle doctor" for his ability to alleviate patients' fever and diarrhea through injections and a few tablets.

HCV is mainly transmitted through contact with infected blood. It can also spread through sex, and from mother to baby during delivery. The infection may lead to liver cancer.

HIV

Research Yields Insights About HIV-Related Headaches

Released: 12/6/2011 8:00 AM EST

Source: University of Mississippi

Newswise — OXFORD, Miss. – A University of Mississippi study of headaches among HIV patients is being hailed as a critical step to improving treatment and reducing unnecessary medical costs among sufferers.

The paper, "Headache among Patients with HIV Disease: Prevalence, Characteristics, and Associations," is being published in a forthcoming issue of the journal Headache and is already available online at http://onlinelibrary.wiley.com/doi/10.1111/j.1526-4610.2011.02025.x/abstract.

The study, which is attracting broad interest in the medical and mental health communities, was conducted as part of a doctoral dissertation by UM psychology alumnus Kale Kirkland while working in the Headache Research and Treatment laboratory under Todd Smitherman, assistant professor of psychology. The study was conducted in conjunction with clinicians from the University of Alabama Health Center in Montgomery.

"This research is of interest to clinicians and physicians for several reasons," Smitherman said. "Recent research from the U.S. Centers for Disease Control and Prevention shows that, despite the availability of medications that effectively slow disease progression, most Americans with HIV do not have the disease under control. Our study shows that patients with poorly-controlled HIV/AIDS are most prone to suffer also from frequent, severe migraines at rates that far exceed those of the general population."

Specifically, the results of the study show that headache affects one of every two HIV/AIDS patients, but these are not your typical, run-of-the-mill tension headaches.
Approximately 27.5 percent of the patients studied met criteria for "chronic migraine," a rare headache condition in which a person has migraine symptoms – with or without other headaches – for 15 or more days per month. In comparison, only 2 percent of the general population is classified as having chronic migraines.

"This translates into a 13-fold increased risk of chronic migraine among patients with HIV disease," Smitherman said. "The strongest predictor of headache was the severity of HIV disease, such that patients with more advanced disease had more frequent, more severe and more disabling migraines."

This is the first study since the proliferation of highly active antiretroviral therapy, or HAART, medication to demonstrate that having HIV/AIDS portends a very high risk of headache, particularly migraines.

These data highlight how important it is for physicians to regularly monitor CD4 levels, an indicator of immune system functioning, among this population and to pay close attention to headache symptoms among patients with more advanced disease. They also emphasize the importance of adherence to medication regimens among HIV patients.

"The study used a structured diagnostic interview to assess headache symptoms consistent with diagnostic criteria from the International Classification of Headache Disorders among 200 clinic patients in Montgomery, Alabama with HIV or AIDS," Smitherman said. "Patients also completed measures of headache-related disability, and their medical records were reviewed for information about prescribed medications, CD4 cell count, date of HIV diagnosis, possible secondary causes of headache and other relevant medical history."

"We decided to conduct this study due to a lack of research in the area of headaches in the HIV population," Kirkland said. "In general, prior to our study, there was no 'typical' HIV headache.

"With the results from our study, we hope that infectious disease physicians will now be able to discuss with HIV patients what to expect in terms of headaches. This should also help prevent unnecessary medical costs, lessening the need to have expensive procedures – such as MRIs and spinal taps – ordered to rule out opportunistic infections."

HIV-related infections were determined not to be frequent causes of headache among patients in the study, but the authors caution that further studies that include neuroimaging procedures are needed to confirm these findings.

Because the study came from a psychological perspective, Smitherman and Kirkland said they hope to further educate mental health professionals on HIV, which should help improve treatment, given that HIV patients also have increased rates of depression and anxiety.

For more information about the UM Department of Psychology, visit http://www.olemiss.edu/depts/psychology/ or call 662-915-7383.

For more news from the University of Mississippi, go to http://zing.olemiss.edu/

Hope for Future, Fear of Failure on World AIDS Day

A curious emotional amalgam marked this year's World AIDS Day.

On one hand, there is increasing confidence that many of the tools needed to halt the devastating pandemic are either available or will soon be ready.

On the other, there is growing fear that the political and financial will to use those tools is failing.

"The science is beginning to tell us we can end the epidemic," said Mitchell Warren of the New York-based advocacy group AVAC. "Things are falling in to place."

But Warren and others told MedPage Today that global economic uncertainty could mean that the opportunity will be missed.

New 'Lite' Approach Could Save More Lives With Less Money
Jeremy Laurance
(The Independent, London, December 1, 2011)
"A radical approach to delivering antiretroviral drugs to people with HIV to halt the transmission of the virus is being implemented in...Africa, opening the way to treatment for least one million extra patients at no additional cost. The move...comes at a time when the global economic crisis is threatening progress against the pandemic. The project, known as 'Lab-Lite,' is being run in Uganda, Malawi and Zimbabwe and involves monitoring the roll-out of antiretroviral drugs to rural areas, where two-thirds of the population live, without the array of laboratory testing conventionally regarded as necessary. The [money saved can be used for]...purchasing more drugs and treating more patients…Routine laboratory testing every three or four months had been thought essential to monitor toxicity and side effects in people on antiretroviral drugs. But a study…in 2009, showed routine lab testing made little difference to survival after five years…One of the main barriers to people receiving treatment is that they live too far from the nearest hospital for testing. They often have to trek long distances to get drugs, so many drop out."

FYI

Cancer’s next stage: A report from Stanford Medicine magazine

Rosanne Spector on December 5th, 2011

It’s the best of times – and a most precarious time – for cancer research.

The new issue of Stanford Medicine magazine, a special report on cancer, explains that while data and insights pour in as never before, the efforts to prevent, treat and cure cancer are faltering. The big threats? A dysfunctional cancer clinical-trial system, disastrous drug shortages and a health-care system unable to deliver cancer care at an affordable price.

Big Pharma

Merck to invest $1.5 bln for R&D in China

By Tan Ee Lyn

HONG KONG Dec 6 (Reuters) - Merck & Co Inc said on Tuesday that it will establish a new Asian R&D headquarters in Beijing and commit $1.5 billion to research and development in China over the next five years.

In an interview with Reuters in late 2010, the company said it expected emerging markets to make up a bigger part of total revenue in coming years because of an explosion in chronic non-communicable diseases such as diabetes and hypertension.

It said seven countries -- Brazil, China, India, Mexico, Russia, South Korea and Turkey -- were especially important.

By the end of 2010, emerging markets were responsible for about 18 percent of overall global business and that figure was estimated to grow to 25 percent by 2013, the company said.

The United States is Merck's largest market, generating between 40 and 45 percent of revenue.

Healthy You

From Medpage Today

Report: Fish Oil Supplement Quality Spotty
By Michael Smith, North American Correspondent, MedPage Today
Published: December 06, 2011

Fish oil supplements can be a bit fishy in terms of quality, according to Consumer Reports magazine.

In lab tests of 15 major brands, the magazine said, "six fell a bit short on quality."

"In our recent tests, we found that some (supplements) were not as pure as one might think," the magazine's health editor, Ronni Sandroff, said in a statement.

But a spokesman for the Council for Responsible Nutrition, an industry group, said the magazine was putting a "negative spin" on what was really a positive report.

Fish oil supplements are a booming business, largely because of the health benefits associated with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), omega-3 fatty acids that can reduce the risk of heart attacks and strokes.

Consumer Reports tested three lots each of the 15 brands to see if they contained the amount of EPA and DHA that they claimed and also to check on levels of lead, mercury, dioxins, or polychlorinated biphenyls.

The bottom line, the magazine said, is that "all had their labeled amount of EPA and DHA." As well, none of them had contaminant levels that exceed standards set by the U.S. Pharmacopeia (USP), a nongovernmental agency, or by the European Union.

In other words, the products "meet all of their applicable legal and regulatory requirements," said Duffy MacKay, ND, vice-president for scientific and regulatory affairs for the industry group.

The report is actually a positive assessment of the tested products, MacKay told MedPage Today.

The shortfalls the magazine noted include:

Four of the products had at least one sample with PCB levels that could require a warning label under a California consumer law
One product had "elevated levels of compounds that indicate spoilage"
Two samples of another supplement failed a test for pills with enteric coatings, suggesting the coatings might dissolve more quickly than intended, leaving a fishy aftertaste

Consumer Reports quoted the FDA as saying the agency has not taken action against any manufacturer for contaminants because it doesn't see a health risk.

MacKay said the California law cited by the magazine -- Proposition 65 -- is intended to let consumers know what is in products and has "nothing to do with health-related risk."

He noted that the law is "exclusive to California," where he said none of the tested products has been taken off shelves.

MacKay also said the magazine used a test for spoilage that is intended to detect a compound called anisidine, but used it on products that were lemon-flavored.

The addition of the lemon flavoring causes the test to yield a false positive, he said


Off The Cuff

U.K.: Hospital Patients 'More Likely to Die at Weekends'
Nick Triggle
(BBC News, November 28, 2011)
"Research company Dr Foster [found a]…10% spike in deaths compared with weekdays across 147 hospital trusts [in the England]. It said some deaths could have been avoided with better staffing and access to services such as diagnostics. The review also looked at performance overall, warning death rates appeared to be higher than they should be in more than a quarter of trusts. Dr Foster, which works closely with the Department of Health, said its findings needed to be investigated urgently. The data…looked at death rates using four measures -- deaths in hospital, deaths in hospital and within 30 days of discharge, deaths linked to low-risk conditions and deaths after surgery…it was acknowledged that some of the deaths were unavoidable as people who were at the end of life were more likely to be admitted to hospital at the weekend. This is because community services which they would have relied on if they had been close to death during the week would not be available…The report concluded weekend treatment was 'risky.'"

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