Hepatology Department, National Liver Institute, Shebeen El-Kom, Egypt.
Abstract
INTRODUCTION: Chronic hepatitis C is associated with many extrahepatic manifestations that impact and impair the quality of life. Hepatitis Cvirus (HCV) infection has a high prevalence in Egypt and carries with the diagnosis many social impacts and stigmatization correlates that further impair social function. This might negatively impact patients and their sexual function. Sexuality and sexual function have not been studied well in patients with HCV, especially in women.
AIM: To investigate sexual dysfunction in Egyptian women with chronic hepatitis C.
MAIN OUTCOME MEASURES: Female Sexual Function Index (FSFI) scores of patients with hepatitis C, both total and for individual domains, were compared with those of controls.
METHODS: The self-administered FSFI questionnaire was completed by 112 sexually active female patients with chronic hepatitis C without liver cirrhosis prior to initiation of therapy by pegylated interferon and ribavirin. Their results were compared to those of 225 age- and socioeconomic class-matched sexually active healthy females.
RESULTS: Significantly more patients than controls had questionnaire scores below the threshold of female sexual dysfunction (FSD) (79% vs. 21%, P < 0.05), and the mean total score for the patients was significantly lower than that for controls (19.54 ± 6.2 vs. 28.43 ± 4.9 P < 0.001). The patients' scores in all domains of the questionnaire were significantly lower than those of the controls.
CONCLUSION: Chronic hepatitis C negatively impacts female sexual function, affecting all domains of the sex cycle; this warrants further studies and needs to be addressed as part of a comprehensive therapy plan to improve patients' quality of life. Elshimi E, Morad W, Mohamad NE, Shebl N, and Waked I. Female sexual dysfunction among Egyptian patients with chronic hepatitis C. J Sex Med **;**:**-**.
1 Department of Hepato-Gastroenterology, Kaohsiung Chang Gung Memorial Hospital and Chang Gung University College of Medicine , Kaohsiung, Taiwan .
Abstract
Low-dose oral interferon could exert immune-modulating effects in human. We conducted a clinical trial to investigate the efficacy of oral interferon-alpha in preventing hepatitis C relapse. Totally 169 genotype 1b chronic hepatitis C patients having achieved end-of-therapy virological clearance were randomized to receive interferon-alpha lozenge 500 IU/day (n=59), 1,500 IU/day (n=53), or placebo (n=57) for 24 weeks. Overall, no significant differences were found for the relapse rates in the 3 groups (P>0.05). However, in patients with fibroindex 1.4-1.7, relapse occurred in 1/12 (8.3%) 500 IU-group patients versus 9/21 (42.9%) patients of the other groups (P=0.05). In 158 patients receiving at least 4 weeks of oral interferon, significantly higher platelet count was found at the end of trial in the 500 IU group (P=0.003). In thrombocytopenic patients, a significantly expedited recovery of platelet count was found in the 500 IU group (P=0.002). No drug-related severe adverse events were reported. In conclusion, at 500 IU/day, oral interferon exerted a borderline suppression effect of virological relapse in chronic hepatitis C patients with mild liver fibrosis. Additionally, it significantly expedited platelet count recovery after the end of peginterferon therapy.
PMID: 24237300 [PubMed - as supplied by publisher]
New Zealand Liver Transplant Unit, Auckland City Hospital, Auckland, New Zealand. Electronic address: edgane@adhb.govt.nz.
Abstract
BACKGROUND & AIMS: We evaluated an all-oral regimen comprising the nucleotide polymerase inhibitor sofosbuvir with the NS5A inhibitor ledipasvir or the NS5B non-nucleoside inhibitor GS-9669 in patients with genotype 1 hepatitis C virus (HCV) infection.
METHODS: A total of 113 patients were enrolled. Sofosbuvir (400 mg once daily) and ledipasvir (90 mg once daily) plus ribavirin were given for 12 weeks to treatment-naïve patients (n=25) and those who did not respond to previous therapy (prior null responders, n=9). Sofosbuvir and GS-9669 (500 mg once daily) plus ribavirin were given for 12 weeks to treatment-naïve patients (n=25) and prior null responders (n=10). Additionally, prior null responders with cirrhosis were randomly assigned to groups given a fixed-dose combination of sofosbuvir and ledipasvir, with ribavirin (n=9) or without ribavirin (n=10). Finally, a group of treatment-naïve patients received sofosbuvir, ledipasvir, and ribavirin for 6 weeks (n=25). The primary efficacy endpoint was sustained virologic response 12 weeks after therapy (SVR12).
RESULTS: SVR12 was achieved by 25/25 (100%) of treatment-naïve patients receiving sofosbuvir, ledipasvir, and ribavirin and 23/25 (92%) of those receiving sofosbuvir, GS-9669, and ribavirin. Of treatment-naïve patients receiving 6 weeks of sofosbuvir, ledipasvir, and ribavirin, 17/25 (68%) achieved SVR12. All non-cirrhotic prior null responders receiving 12 weeks of sofosbuvir along with another direct-acting antiviral agent plus ribavirin achieved SVR12-9/9 (100%) of those receiving sofosbuvir, ledipasvir, and ribavirin and 10/10 (100%) of those receiving sofosbuvir, GS-9669, and ribavirin. Among cirrhotic prior null responders, SVR12 was achieved by 9 (100%) of those receiving sofosbuvir, ledipasvir, and ribavirin and 7 (70%) of those receiving sofosbuvir and ledipasvir without ribavirin. The most common reported adverse events were headache, fatigue, and nausea.
CONCLUSIONS: The combination of sofosbuvir and a second direct-acting antiviral agent is highly effective in treatment-naïve patients with HCV genotype 1 infection and in patients that did not respond to previous treatment.
Inserm U1052/CNRS UMR5286, Centre de Recherche en Cancérologie de Lyon (CRCL), 151, Cours-Albert-Thomas, 69424 Lyon cedex 03, France; Université Claude-Bernard Lyon 1, 69000 Lyon, France.
Abstract
Chronic hepatitis C is a major cause of cirrhosis and hepatocellular carcinoma. Current therapy based on pegylated-interferon-α (PEG-IFN) and ribavirin (RBV) combination has limited efficacy and is poorly tolerated. Disease progression is highly variable and pre-therapeutic prediction of response to treatment remains difficult. Although viral kinetics proved most useful to monitor duration of therapy, other predictors would be helpful to identify patients with the best chance of subsequent treatment response prior initiation of antiviral therapy (double or triple therapy). The predictive power of IL28B polymorphism is well-recognized and has become the reference biomarker for clinicians in patients treated with double therapy. The combination of serum IP-10 and IL28B SNPs increases predictive value of treatment response. Recently, anti-E1E2 antibodies appear to closely correlate with therapeutic outcome and predict the complete elimination of HCV. They may represent a new relevant prognostic biomarker of double therapy response. Since the introduction of triple therapy including protease inhibitors (telaprevir/boceprevir), the major priority is to help patients who failed on double therapy, and there is now an urgent need for robust pre-therapeutic predictors of response to better select the patients to treat. Indeed, the relevance of IL28B polymorphism and IP-10 serum concentration are limited in triple therapy. Many new drugs are currently under investigation and there is hope that effective and well-tolerated IFN-free regimens may become a part of future therapy. In this context, this will help to identify the most powerful predictive marker and/or to assess the benefit of anti-E1E2 in decision to treat.
Klinik für Gastroenterologie, Hepatologie und Endokrinologie, Zentrum Innere Medizin, Medizinische Hochschule Hannover, Carl-Neuberg-Str. 1, 30625, Hannover, Deutschland.
Abstract
BACKGROUND: In the last 10 years, a dramatic change has occurred in the treatment of chronic viral hepatitis, particularly in the area of hepatitis B and hepatitis C.
OBJECTIVES: Which treatment options of viral hepatitis are scientifically validated and can be recommended for practical use in consideration of current studies on the treatment of viral hepatitis and the German and European guidelines, respectively.
CURRENT DATA: The treatment of chronic hepatitis B continues to be based either on a long-term therapy with nucleos(t)ide analogues or a finite therapy with pegylated interferon alpha (PEG-IFN). Treatment of hepatitis D is also based on PEG-IFN; however, the relapse rate is high. The treatment of hepatitis C is currently based on the combination of PEG-IFN and ribavirin (RBV). To estimate the optimal duration of therapy and dosage, knowledge of previous treatments, genotype, and presence of cirrhosis is crucial. For genotype 1, the first direct acting antiviral drugs were approved in 2011. These drugs led to a significant increase in treatment success. In the upcoming years another dramatic change in the treatment of hepatitis C is anticipated, including an improved side effect profile, increased efficacy, and a greater degree of customization in difficult-to-treat patients. Acute hepatitis E is usually self-limiting, but can become chronic in immunocompromised patients, i.e., after organ transplantation. Reduction of immunosuppression may clear HEV and RBV shows antiviral efficacy.
CONCLUSION: Currently available therapies have a high disease control or chance for cure in hepatitis B and C. In Hepatitis C treatment, a massive change in future therapies is foreseeable. The hepatitis D co-infection remains difficult to treat. For hepatitis E, RBV is a promising off-label treatment option.
PMID: 24258199 [PubMed - as supplied by publisher]
The Fair Pricing Coalition (FPC) today expressed disappointment at the price Janssen Therapeutics set for Olysio (simeprevir), a second generation protease inhibitor (PI) approved by the U.S. Food and Drug Administration on November 22, 2013 for the treatment of chronic hepatitis C (HCV) in genotype 1 patients. Janssen has set the wholesale acquisition cost, (WAC) for a single 12-week course of Olysio at $66,360. Though this is in parity with current HCV PIs, the FPC believes that all HCV drugs are priced too high. The WAC price of Olysio represents only part of the cost of an anti-HCV regimen, including at least $18,000 in WAC costs of interferon and ribavirin, plus the additional cost of the NS3 Q80K polymorphism screening test recommended by the FDA for all patients before initiating Olysio therapy.
“While we are very excited to have more effective and more tolerable treatment options for people living with hepatitis C, we are concerned about the overall cost of treatment,” said FPC HCV Co-Chair Lorren Sandt. “Janssen did price Olysio comparatively with other HCV PIs, but the bar previously had been set too high. We strongly urged Janssen to price Olysio lower than current regimens to help address the overall cost of therapy, which continues to spiral out of control.”
The FPC is gravely concerned about the continued precedent this pricing has on the future of HCV therapy. Industry experts have stated their expectations that Gilead Sciences’ new direct acting antiviral, sofosbuvir, will be approved by the FDA in the next few weeks. While the cost of sofosbuvir is not yet known, patients and doctors may look to combine these therapies (off label), resulting in an expected doubling of the current price of therapy.
“We know that this is just the initial price,” said Sandt. “Other HCV protease inhibitor manufacturers quickly increased prices after their initial 2011 launch. For example, a 12-week course of Vertex’s PI Incivek (telaprevir) had a WAC price of $49,000 at launch, but is now priced at $66,155. We caution Janssen not to continue this unacceptable trend. Treatment is just too costly for the majority of people living with chronic HCV,” concluded Sandt, “and we fear that barriers to patient access will be inevitable as a result.”
Anticipating the price of Olysio, the FPC urged Janssen to expand their access programs to ease the fiscal challenges that patients will face when trying to purchase Olysio. The FPC acknowledges that the Johnson & Johnson Patient Assistance Foundation agreed to expand the eligibility criteria for Olysio from 200% to 500% of the Federal Poverty Level (FPL). While this is a step in the right direction, it is not as generous as the program Vertex established for their PI, which is a maximum household income of $100,000 per year. The FPC also applauds Janssen’s intent to initiate a $25,000 per course of treatment co-pay program for Olysio. Unfortunately, the legal status of such programs for the Qualified Health Plans in the new Affordable Care Act Exchanges remains in question, possibly making Olysio access out of reach for many ACA patients.
“We thank Janssen for responding to our requests to increase the eligibility level of their PAP for Olysio and for developing a generous co-pay assistance program,” said Murray Penner, a member of the FPC. “We know that co-insurance costs will be very high for patients. Despite the access programs Janssen has in place, we are very concerned that the high price of Olysio, coupled with high co-insurance costs for patients, will result in limited access to Olysio.”
The Fair Pricing Coalition (FPC) is a group of community treatment activists advocating for fair and sustainable pricing of HIV and viral hepatitis drugs in the United States. The FPC was formed in 1998, in response to the exploitative pricing of the first HIV drug Retrovir (AZT, zidovudine), the FPC: • negotiates with drug companies prior to price setting of new therapies; • monitors and reports on price increases; • collaborates with government officials and care providers on drug price reduction strategies; • advocates for expansion of industry sponsored assistance programs; • educates our communities on the impact of drug pricing on treatment access; and • organizes grassroots-‐driven media campaigns to prevent or fight against unfair drug pricing practices
As CDC Director, I’ve had the privilege of meeting with nurses, doctors, outreach workers, and people living with HIV in communities across the U.S. and around the world.
As an infectious disease doctor who trained in New York City before treatment for HIV was available, these meetings are always deeply moving. Together we’ve made enormous progress addressing the suffering and death caused by this fearsomely deadly virus.
Today is World AIDS Day, the worldwide reminder that we must all continue the fight against HIV.
This year’s theme, “Shared Responsibility: Strengthening Results for an AIDS-Free Generation,” reflects our global commitment to achieving President Obama’s vision of an AIDS-free generation.
We’ve made remarkable progress since the launch of the U.S. President’s Emergency Plan for AIDS Relief – PEPFAR – in 2003.
In June, CDC, together with our sister PEPFAR implementing agencies, achieved a dramatic milestone: the prevention of HIV infection in one million babies globally over the past ten years.
I will never forget the woman I met in Nigeria holding twin babies in her arms. She said to me, “I’m HIV positive, but my babies are HIV negative because of PEPFAR. Please thank the American people for me.”
New HIV infections are declining globally and life expectancy is rebounding in many countries. Because of PEPFAR, more than 5 million HIV-positive people are working, studying, teaching, learning – contributing to their communities – who would otherwise be dead or dying.
More people than ever are aware of their HIV infection status, and that means more people living with HIV can take steps to stay healthy and protect their partners, including by taking antiretroviral treatment.
The heart of what CDC brings to the fight is our ability to share our science and innovation to build capacity across the globe.
From Atlanta and field offices in more than 50 countries, we work alongside our host country and international partners. We have 1,800 people working in the field, the vast majority hired from the local communities. They provide technical assistance, consultation, mentoring, and training in Asia, South America, Africa, and the Caribbean. It’s a huge footprint that makes a real difference across the globe.
We’re helping build systems with the essential components of public health: laboratories, surveillance systems, trained staff, and data systems that can monitor projects and programs, not only for progress, but to ensure maximum impact.
It’s building capacity from the inside out.
In the United States, efforts to curb the HIV/AIDS pandemic through testing, education, prevention, care, and treatment are bolstered by new evidence that antiviral treatment greatly reduces risk of spread of HIV.
On this World AIDS Day, CDC continues to bring the best prevention and treatment tools at our disposal to the communities that need them most.
We’re closer today than ever to reaching the goal of an AIDS-free generation, and that’s reason to celebrate. But more importantly, it’s reason to dedicate ourselves even more to scaling up what works to stop the HIV/AIDS pandemic.
Look everyone I can't get the cure.the reason is I was a victim of real bad child abuse when I was a baby.and the rest I don't remember but I was told years later that I was adopted for one and abused very badly that I spent most child hood years in the hospital and that I had a major surgery.and they had to give me a transfusion not knowing the blood was tainted with hepatitis c.I didn't find out till years later when I donated blood and I got the letter saying I have hepatitis c.after all the years of asking I was told it was from that surgery I had as a baby in the early 70s.and now I have seizures and real bad anxiety all do to left sided brain damage.
December 1 is World AIDS Day. At NIDA, we always stress the principle that drug abuse treatment is AIDS prevention, because of the close links that exist between drug abuse and the spread of HIV. Injection drug use alone contributed to more than 7% of new infections in 2011, although the population of people who use drugs by any route who are also HIV-positive is much higher. Drug use goes hand-in-hand with various behaviors besides needle-sharing that place individuals at risk for HIV infection, such as unprotected sex.
A new study by researchers in Vancouver, British Columbia shows that, beyond the benefits of drug addiction treatment in HIV prevention, it also supports HIV treatment. Drug users face numerous unique challenges that contribute to poorer outcomes from HIV infection. The Canadian study found that, in the absence of financial and other barriers preventing access to antiretroviral therapy (ART) regimens, opioid-dependent individuals engaged in methadone maintenance therapy (MMT) were less likely to discontinue ART than those not engaged in MMT and were more likely to achieve suppressed viral loads.
This study shows that investment in drug treatment improves a crucial step in the HIV Care Continuum: helping people stay in care—since HIV treatment is a lifelong process until a cure is found. By treating drug dependence, a person is benefiting not only from a lifestyle free of illicit drug use but from one that is less compromised by HIV because remaining on ART will be more likely. The benefits of delivering addiction treatment to HIV-positive drug users could also extend to the community, by reducing the likelihood of HIV transmission to others.
We have done much to reduce the spread of HIV, but there are still approximately 50,000 new HIV infections each year, and at the end of 2010, an estimated 872,990 people in the United States were living with an HIV diagnosis. World AIDS Day is an occasion to renew our commitment to reducing the scourge of AIDS and curbing the spread of HIV. The Canadian study is a reminder that drug addiction treatment is an intrinsic part of those goals.
At the 1992 Freddie Mercury Tribute Concert, my grandmother, Elizabeth Taylor, gave some simple and on-point sexual advice: "Straight sex, gay sex, bisexual sex: use a condom -- whoever you are."
It might seem a bit unusual to hear your grandma reminding you (and a packed stadium) that if you're getting laid, use a condom. But she was always blunt -- and someone who spoke straight from her heart.
Since her death, I've been striving to continue on the path that my grandmother helped to establish in the fight against HIV/AIDS. Last year I helped to start a Los Angeles branch of genCURE, a youth-oriented division of amfAR (which she helped to form in 1985), and over the last few months, I have been working closely with the support-based Elizabeth Taylor AIDS Foundation (ETAF) that she started in 1991.
At 27 years old, I've noticed that many of my friends don't seem to regard HIV/AIDS as a major concern in their lives. This is bewildering considering that here in the U.S. the CDC counts 20-24 year olds as the largest group of new infections and young adults and teens between 13 and 29 as comprising over 35 percent of new infections across all age groups. Of course, my age group is not uniquely at risk of infection. Persons of every age, background, sexuality, everywhere in the world, can be at risk. There are approximately 35 million people living with HIV around the world (WHO), with over a million here in the U.S., a fifth of whom do not realize they are positive (aids.gov).
So now, 25 years after the first World AIDS Day in 1988, I'm writing to reiterate the same fundamental call to awareness and action that World AIDS Day was founded upon and to which my grandmother was dedicated. I'm asking my friends and peers, young and old, gay and straight -- anyone who is reading this -- to engage in the individual responsibilities that we all share in the global fight against HIV/AIDS.
In 1986 the US Surgeon General C Everett Koop released a report on AIDS in which he recommended condom use, testing to know one's HIV status and avoiding sharing needles as individual ways of stopping transmission of the virus. These basic principles aren't new but they are worth repeating year after year and generation after generation.
Get tested if you could have been exposed to anything that puts you at risk of HIV infection. The importance of getting tested is eloquently summarized in this brief video produced by Portland, Oregon-based Cascade AIDS Project, which is funded in part by ETAF. As the video clearly states: "one in five people who have HIV don't know they have it, but when they do know, they are 70 percent less likely to pass HIV to their partners, and if they take medication, use protection, and stay in care, then transmission rates can drop by up to 96 percent."
To expand upon that: If you are in an exclusive and trusting relationship and don't want to use protection, get tested together. I have friends who entered into exclusive relationships and began having unprotected sex because both parties thought (or claimed) themselves to be negative. They later learned, too late, that one of the partners had actually been positive and had transmitted the virus.
At the Freddie Mercury tribute concert I mentioned earlier, my grandma went on to give some more good advice: "If you share drugs, don't share a needle." She stood behind that advice by personally funding 59 syringe exchange programs since 1992. According to the Lower East Side Harm Reduction Center in Manhattan, to which ETAF has been providing funding since 1999, the transmission rate among injection drug users in New York State has plummeted from over 50 percent in 1992 to about 5 percent as of 2008. That exceptional drop in transmission speaks volumes to the importance of using clean syringes if you are using injection drugs.
ETAF and amfAR have helped to save countless lives around the world. Such organizations are imperative in our communal response to HIV/AIDS. Our individual actions are too.
If you engage in sexual or drug-related activities, it doesn't matter whether you identify them as being "high risk" or "low risk," because either way, you can be at risk. So, I'm writing now to simply say: please be careful. Demonstrate responsibility to yourself and those with whom you might share yourself. It is through such individual responsibility that we can each participate in the international fight against HIV/AIDS, and work towards ending the pandemic one step at a time.
Currently, hepatitis C virus (HCV) infection is considered a serious health-care problem all over the world. A good number of direct-acting antivirals (DAAs) against HCV infection are in clinical progress including NS3-4A protease inhibitors, RNA-dependent RNA polymerase inhibitors, and NS5A inhibitors as well as host targeted inhibitors. Two NS3-4A protease inhibitors (telaprevir and boceprevir) have been recently approved for the treatment of hepatitis C in combination with standard of care (pegylated interferon plus ribavirin). The new therapy has significantly improved sustained virologic response (SVR); however, the adverse effects associated with this therapy are still the main concern. In addition to the emergence of viral resistance, other targets must be continually developed. One such underdeveloped target is the helicase portion of the HCV NS3 protein. This review article summarizes our current understanding of HCV treatment, particularly with those of NS3 inhibitors.
1. Introduction
In the mid-1970s, it was noticed that supply of blood was contaminated with an unidentified agent causing posttransfusion non-A, non-B hepatitis [1]. This unknown infectious agent struck intravenous drug users and blood transfusion recipients. The offender agent identified in 1989 was hepatitis C virus (HCV) and the first sequences of HCV were reported [2]. HCV is one of the leading agents that cause liver failure, and hepatocellular carcinoma and is the most relevant reason for liver transplantation. HCV infects about 3% of the world population; 130–200 million people are estimated to be chronically infected globally. Alarming news is that 350,000 people worldwide die from HCV-related disease every year [3]. For more than 20 years, HCV has been taking the attention of the health professionals, and now, well recognized that HCV is actually a major global health problem. Recently, health professionals determined the worldwide prevalence of HCV in comparison with HIV. The global prevalence of HCV estimates is 400,000 chronically infected subjects in Australia and Oceania, 14 million in the United States of America, 16 million in the Middle East, 17.5 million in Europe, 28 million in Africa, and 83 million in Asia [4]. Therefore, novel and effective inventions with fewer adverse effects are required for the prevention and control of HCV. The main goal of this review article is to be updated with the current treatments of HCV, putting an emphasis on the HCV NS3 protease and NS3 helicase inhibitors.
2. HCV Translation and Polyprotein Processing
HCV belongs to the founding member Hepacivirus genus of the family Flaviviridae [2, 5]; it is a positive sense single-stranded RNA virus with seven genotypes and more than 90 different subtypes [6]. The viral genome is 9600 nucleotides (nt) in length, which contains a 5′-nontranslated region (NTR) with an internal ribosome entry site (IRES), 3′-NTR and encode a single polyprotein containing 3000 amino acids, and is positioned between 5′-NTR and 3′-NTR. The translation of the polyprotein is initiated by an internal ribosome entry site (IRES) present at the 5′-NTR [7]. Unlike eukaryotic mRNA, HCV genome which lacks a 5′ cap translation depends on IRES that directly binds with 40S ribosomal subunits, inducing conformational changes in the 40S subunits [8]. The IRES-40S complex then recruits eukaryotic initiation factor (eIF) 3 and the ternary complex of Met-tRNA-eIF2-GTP to form a noncanonical 48S intermediate before a kinetic slow transition to the translationally active 80S complex [9, 10]. Once the formation of initiation complex takes place, the genome of HCV is translated to produce a large polyprotein that undergoes proteolytic cleavages with specific viral and cellular proteases to form 10 individual viral proteins, each of which has specific functions in viral life cycle (Figure 1). The N-terminal one-third of the polyprotein encodes the virion structural proteins; the core protein (C) forms the viral nucleocapsid and envelopes glycoproteins E1 and E2, involved in receptor binding required for viral entry into the hepatocyte [11]. A small integral membrane protein, p7, functions as an ion channel [12, 13]. The remaining portion of the genome encodes 6 important nonstructural (NS) proteins: NS2, NS3, NS4A, NS4B, NS5A, and NS5B, which coordinate the intracellular processes of the viral life cycle. Host endoplasmic reticulum (ER) derived signal peptidase cleavages the mature structural proteins among the junctions C/E1, E1/E2, and E2/p7. Signal peptide peptidase releases core from E1 signal peptide. The p7/NS2 junction is also cleaved by signal peptidase within the NS region. Two viral enzymes, the NS2 autoprotease and the NS3-4A serine protease, are involved further in the proteolytic processing of NS proteins. The NS2 autoprotease cleaves at the NS2/3 site, whereas the NS3-4A serine protease, which requires the NS4A protein as cofactor for functioning properly, cleaves at all downstream junctions. Another small protein that encodes HCV genome is called F (frame shift) or ARFP (alternative reading frame protein), but its precise roles in viral life cycle are unknown [14].
Figure 1: HCV genome and polyprotein processing. (a) Open arrow, closed arrows, closed circle, and open circles indicated signal peptide peptidase, signal peptidase, NS2 autoprotease, and NS3-4A serine protease cleavage site(s), respectively. (b) This figure was drawn by UCSF Chimera (http://www.cgl.ucsf.edu/chimera/), a software program for visualizing molecules, with the structural data from Protein Data Bank (PDB) ID 3O8R. Each domain of NS3 was color-coded. Both blue and purple represent helicase core domain, and green and yellow indicate C-terminal region and protease domain, respectively. ADP and RNA were drawn in red as ligands.
3. The Functions of HCV NS3 Proteins
NS3 is a multifunctional protein (amino acids 1–631) with serine protease activity at the N-terminal (aa 1–180) and a nucleoside-triphosphatase- (NTPase-) dependent RNA helicase activity (NS3 NTPase/helicase) at the C-terminal (aa 181–631). Both enzyme activities have been well defined and high-resolution structures have been solved [15]. The C-terminus of NS3 encodes a DExH/D-box RNA helicase. NS3 helicase hydrolyzed NTP as an energy source to unwind double-stranded RNA in a 3′ to 5′ direction during replication of viral genomic RNA [16]. Structural analysis of NS3 revealed the unidirectional translocation and proposed a new function of NS3 as translocase, considering feasible strategies for developing specific inhibitors to block the action of NS3 helicase [17]. The activity of NS3 helicase can be regulated by interactions between the serine protease and helicase domains of NS3 [18,19], indicating that these two enzyme activities may be somehow coordinated during replication. The function of the HCV helicase is unknown; it has been shown that without functional helicase domains, HCV cannot replicate in cells. It may be involved in the initiation of RNA synthesis on the HCV genome RNA, which contains stable 3′-terminal secondary structure in dissociation of nascent RNA strands from their template during RNA synthesis or in displacement of proteins or other trans-acting factors from the RNA genome. It has been now well recognized that both activities of NS3 protein are required for the replication of virus; they are considered as attractive target sites for the development of direct-acting antivirals (DAAs) therapies. NS5B is the viral RNA-dependent RNA polymerase [20], another promising anti-HCV target site. NS5A is a phosphoprotein specifically [21] capable of interacting with the 3′-NTR of the HCV genome [22], other nonstructural proteins [23], and numerous cellular proteins [24, 25]. NS5A also functions in virus assembly [26, 27]. NS4B is an integral membrane protein that is required for the assembly of the “membranous web,” the organelle used for RNA replication [28, 29]. NS4A is a cofactor for NS3 that directs the localization of NS3 and modulates its enzymatic activities [30].
4. Current Treatment for HCV Infection
A combination of pegylated interferon and ribavirin is still the only choice for the treatment of hepatitis C. Depending on the genotypes, this standard of care (SOC) increased the sustained virologic response (SVR) and defined the HCV RNA levels undetectable in the blood 24 weeks posttreatment, from ~5% to ~40–80%. In HCV genotype 1 infected patients, those with high viral loads, mostly null responders or relapsers, the SOC treatment with pegylated interferon plus ribavirin for 48 weeks achieves 50% SVR [31–35]. On the other hand, the SOC treatment with pegylated interferon plus ribavirin for 24 weeks up to 80% achieves SVR in the HCV genotype 2 infected patients. However, current SOC is associated with severe side effects including rash, nausea, anemia, and depression.
The preventive measures against HCV include the development of HCV vaccine which may be one good idea. This is a challenging job because HCV has a great ability to change its amino acid and evade the immune response, which is-10 fold higher than HIV [3]. The development of HCV vaccine is now in progress [36]. In 2011, the US Food and Drug Administration approved two new antivirals, boceprevir and telaprevir, which was a milestone in HCV research. They inhibit an important viral protein, the NS3-4A protease. The drugs are designed in such a way that specifically attack HCV genotype 1, which is considered one of the most prevalent genotypes, accounting for about 60% of global infections, and the least responsive to current treatment. This new standard of care, a combination of boceprevir or telaprevir with peg-IFN plus ribavirin, has been approved for elimination of HCV infection in the USA, Europe, and Japan [37–40].
Anti-HCV DAAs can be classified into several categories: (1) HCV NS3-4A serine protease inhibitors, (2) HCV NS3 NTPase/helicase inhibitors, (3) HCV NS5B polymerase inhibitors, (4) HCV NS5A inhibitors, and others.
4.1. HCV NS3 Protease Inhibitors
HCV NS3-4A protease inhibitors (NS3-4A PIs) are classified into two groups. (1) The first generations PIs (boceprevir and telaprevir) are the linear α-ketoamide derivatives. These two inhibitors formed a covalent bond with the active site of the enzyme in a reversible way. Boceprevir and telaprevir are considered the first two DAAs that come to the HCV drug market, and are approved by FDA for the treatment of HCV genotype 1 infected patients as triple therapy with conventional approaches. (2) The second generations of PIs are mostly linear and macrocyclic noncovalent inhibitors of the NS3-4A enzyme. To date, both generations of PIs are highly potent inhibitors of the NS3-4A enzyme. It is known that the advantages of the second generations of PIs over the first generations are their convenience and improved side effects profile. As the resistance mutations are crucial issues in HCV therapy, unfortunately, they share the same basic resistance mutations that are generated by the first generations of PIs. Only two exceptional drugs, MK-5272 and ACH-2684, do not share the same resistance mutations, are now in clinical investigations (Table 1). ABT-450/r with potent clinical effects achieved SVR through 36 weeks of posttreatment observation, raising the possibility to treat hepatitis C with interferon-free regimens in HCV genotype 1 infected patients [41]. Simeprevir (TMC435) is being under investigated macrocyclic noncovalent NS3-4A protease inhibitor that is currently in Phase III clinical development. Clinical data showed that the addition of TMC435 to the SOC significantly increased the SVR [42]. Faldaprevir (BI 201335) is an inhibitor of HCV NS3-4A protease and is undergoing Phase III clinical trials [43, 44]. The major pharmacologic properties of clinically developed NS3-4A protease inhibitors are summarized in Table 2.
Table 1:Current HCV NS3-4A protease inhibitors/drugs in pipeline (/r means boosted by ritonavir).
Mechanism
Inhibitor name
Genotypic coverage
Daily dosing
Company
Status
Reversible covalent inhibitor
Incivek (telaprevir, VX-950)
1
Three times
Vertex
Approved
Victrelis (boceprevir, SCH503034)
1
Three times
Merck
Approved
Noncovalent inhibitor
ABT-450/r
1
Once
Abbott
Phase III
Simeprevir (TMC435)
1, 2, 5, and 6
Once
Janssen
Phase III
Faldaprevir (BI201335)
1
Once
Boehringer Ingelheim
Phase III
Danoprevir (RG7227)
1
Twice
Genentech
Phase II
Vaniprevir (MK-7009)
1
Twice
Merck
Phase II
MK-5172
1, 2
Once
Merck
Phase II
Asunaprevir (BMS-650032)
1, 4
Once
Bristol-Myers Squibb
Phase II
ACH-1625
1
Once
Achillion
Phase II
GS-9256
1
Twice
Gilead
Phase II
ACH-2684
1, 3
Once
Achillion
Phase II
GS-9451
1a, 1b
Once
Gilead
Phase II
Narlaprevir/r
1
Once
Merck
Phase II
IDX320
1, 1b, 3a, and 4a
Once
Idenix
Phase II
Table 2:Pharmacologic properties of direct-acting anti-HCV agents in clinical development, modified by Liang and Ghany [71].
Property
NS3-4A protease inhibitors
Efficacy
High
Genotypic coverage
Narrow (second generation drugs have broader coverage)
Probability of drug resistance
High
Side effects
Substantial
Drug-drug interactions
Substantial
Currently, many NS3 protease inhibitors with various combinations of NS5A and polymerase inhibitors, with or without ribavirin, are being clinically investigated. For example, a study of the protease inhibitor asunaprevir in combination with the NS5A inhibitor daclatasvir, administered for genotype 1a or 1b infected patients, showed the eradication of the virus in 4 out of 11 patients (36%) [45]. Another report, which used the same regimen but only in patients with genotype 1b infection, achieved SVR 90% [46]. These two studies clearly demonstrated the effects of HCV subtype on the response to a regimen that consists entirely of direct-acting antiviral agents. Therefore, it may be feasible to treat HCV without interferon or ribavirin.
4.2. HCV NS3 NTPase/Helicase Inhibitors
The structure of the NS3 helicase is also available and well characterized. However, the developments of NS3 helicase inhibitors have been slow. This target is traditionally difficult as evidenced by the fact that no helicase inhibitors have been approved for clinical use. The main issue might be toxicity because the motor domains of HCV helicase are conserved to that of cellular proteins. As a result, more attention should be given to find inhibitors that bind sites rather than the conserved regions of cellular enzymes without affecting cellular ATPases or GTPases. Recently, a good number of high-throughput screening systems (HTS) have been developed to screen potential inhibitors that specifically inhibit essential activities of NS3. Many world renowned laboratories are engaged to study the helicase portion of NS3 as a possible HCV drug target over the last 17 years. Several studies have revealed that NS3 is essential for viral replication, both in whole animal and replicon model [47, 48]. Mutations in HCV RNA are unable to replicate in subgenomic replicons, which further validates the necessities of NS3 helicase in viral life cycle. NS3 helicase has unique property that plays a more complex role in viral replication. NS3 helicase unwinds both double-stranded DNA and duplex RNA, but typically most helicases do not unwind both. It is known that there is no DNA stage in HCV replication and replication occurs outside the nucleus; the biological importance of the NS3 helicase’s ability to unwind DNA remains elucidate.
The ATP and RNA binding sites are the most promising targets on HCV. To the best of our knowledge, very limited numbers of small molecules have been reported in the literature over the past years and fewer structure-activity relationships data are available. Because NS3 helicase seems to key cellular motor proteins, monitoring ATP hydrolysis is the early screening assays to screen potential inhibitors that yielded few specific hits. However, recent screens of small chemical libraries through HTS have identified some valuable compounds that inhibit HCV catalyzed DNA unwinding, NTPase-dependent RNA helicase, and RNA binding ability, some of which also prevent HCV replicon in cells. Major NS3 helicase inhibitors with their helicase inhibitory activity employing both DNA or RNA substrate and ATPase activities are discussed in Table 3.
Table 3:Inhibitory effects of some NS3 helicase inhibitors.
Halogenated benzimidazoles and benzotriazoles such as dichloro(ribofuranosyl) benzotriazole (DRBT) and tetrabromobenzotriazole (TBBT) both inhibit HCV helicase catalyzed DNA unwinding with IC50of 1.5 and 20 μM, respectively. When employing RNA substrate, only TBBT inhibits RNA unwinding with IC50 of 60 μM [49]. In another report, the efficacies of TBBT and DRBT were tested in four different HCV genotype 1b replicon systems. Depending on the cell line, TBBT inhibits HCV replicons with IC50 ranging from 40 to 65 μM and DRBT inhibits HCV replicons with IC50 ranging from 10 to 53 μM [50].
Soluble blue HT inhibits NS3 catalyzed DNA unwinding with an IC50 of 40 μM [51]. After several rounds of structural refinement, discovered one of the soluble blue HT derivatives, compound 12, which is a good anti-HCV agent with an IC50 of 10.1 μM and EC50 value of 2.72 μM against HCV NS3 catalyzed DNA unwinding and replicon Ava.5/Huh-7 cells, respectively [51].
Ring-expanded “fat” nucleosides (RENs) inhibit HCV and related Flavivirus helicase, including the West Nile virus (WNV) and Japanese encephalitis virus (JEV). They catalyzed HCV DNA unwinding with IC50 in the 7–11 μM range and HCV helicase catalyzed RNA unwinding with IC50 of 5.5–12 μM. In this paper, RENs demonstrated different selectivity profiles between the viral enzymes [52].
Another nucleoside, the compound 4 (4-carbamoyl-5-[4,6-diamino-2,5-dihydro-1,3,5-triazin-2-yl]imidazole-1-β-D-ribofuranoside), inhibits helicase catalyzed DNA unwinding against WNV and HCV with IC50 of 23 and 37 μM, respectively, but it had no effect on helicase catalyzed RNA unwinding. It was a surprise that no activity was observed against the NTPase/helicase of either DENV or JEV irrespective of whether RNA or a DNA substrate was employed [53].
QU663 inhibits HCV helicase catalyzed DNA unwinding with a <?XML:NAMESPACE PREFIX = "[default] http://www.w3.org/2000/svg" NS = "http://www.w3.org/2000/svg" /> of 750 nM, competing with the nucleic acid substrate without affecting ATPase function, even at high concentrations. Docking studies showed that by interacting with the putative binding site QU663 induced a similar conformational shift [54].
Small peptide inhibitor, 14 amino acid-long peptide (p14), revealed a basic amino acid stretch corresponding to motif VI of HCV, WNV, and JEV of NTPase/helicase. This peptide inhibited the HCV unwinding activity of the enzyme with an IC50 of 0.2 μM employing DNA substrate. The order of inhibitory effects was HCV > WNV > JEV. The binding of the peptides does not interfere with the NTPase activity of the enzymes [55].
Tropolone derivatives have been screened as inhibitors of HCV helicase catalyzed DNA unwinding. The derivative of tropolone, called 3,7-dibromo-5 morpholinomethyltropolone (DBMTr), acts with an IC50of 17.6 μM. It has no effect on HCV helicase catalyzed ATP hydrolysis [56] nor HCV helicase catalyzed RNA unwinding [57]. The authors also mentioned that DBMTr might be developed as potent inhibitor of the HCV helicase due to its low toxicity to yeast cells [56].
Acridone derivatives have also been screened as inhibitors of HCV helicase catalyzed DNA unwinding with IC50 between 1.5 and 20 μM. These compounds also inhibit replication of HCV (EC50 1–10 μM) and are not particularly toxic to cells [58, 59].
The thiazolpiperazinyl derivative compound 23 inhibits the helicase activity with an IC50 of 110 μM, using DNA substrate. None of the compounds were able to inhibit the NS3 NTPase activity. Testing in the subgenomic HCV replication, it exhibited EC50 of 3 μg/μL and CC50 > 50 μg/μL [60].
1-N,4-N-bis[4-(1H-Benzimidazol-2-yl)phenyl]benzene-1,4-dicarboxamide, designed as (BIP)2B, is a potent and selective inhibitor of HCV NS3 helicase, which inhibits unwinding reaction regardless of DNA or RNA substrate, but not ATP hydrolysis without RNA or at saturated level of RNA. (BIP)2B inhibited NS3 helicase from HCV genotypes 1a, 1b, 2a, and 3a. Evidence presented here shows that it directly and specifically binds to NS3 protein [61].
Other new tropolone derivatives, compounds 2, 6, and 7, inhibit HCV catalyzed DNA unwinding (IC50= 3.4–17.8 μM). They are also effective in RNA replication (EC50 = 32.0–46.9 μM) and exhibit the lowest cytotoxicity. The derivatives 2 and 7 have been shown to be resistant mutants. The effects of the compound 2 plus IFN-γ and compound 2 plus ribavirin combinations were evaluated in cell culture, indicating that both combinations result in an additive effect with a very slight tendency to synergy [62]. The tetrahydroacridinyl derivative 3a is the most potent inhibitor reported to date ( nM). It did not show inhibition towards the ATPase activity of NS3 up to 100 μM [63].
Manoalide was originally identified as an inhibitor of phospholipase A2, but later it was reported that it inhibits HCV NS3 helicase activity with RNA substrate (IC50 = 15 μM). In addition, it inhibits the NS3 ATPase and RNA binding to NS3. A direct interaction between manoalide and NS3 was presented to explain the inhibition of NS3 activities through the structural change upon its binding [64].
The commercially available dye thioflavine S is identified as the most potent inhibitor of NS3 catalyzed DNA and RNA unwinding. After separating into their active components, P4 inhibits unwinding, subgenomic replication with IC50 of 2 and 10 μM, respectively, and was not toxic [65].
SG1-23-1, isolated from ethyl acetate extract from marine feather star, Alloeocomatella polycladia, exhibits the strongest inhibition of NS3 helicase activity using RNA substrate (IC50 = 11.7 μg/mL). Interestingly, the extract inhibits interaction between NS3 and RNA but not ATPase of NS3. Moreover, it also inhibits the RNA replication with EC50 of 23 to 44 μg/mL [66].
Four LOPACs Sigma’s library of pharmacologically active compounds (ATA, AG 538, NF 023, and Suramin) were identified. All but AG 538 have the ability to unwind DNA (IC50 = 0.6–3.7 μM) and RNA (IC50 = 0.8–8.9 μM). All but NF 023 inhibited replication of subgenomic HCV replicons (EC50 = 18–98 μM). Unfortunately, none of these inhibitors were specific to NS3 helicase [67].
Recently, it has been reported that an ethyl acetate extract from marine sponge Amphimedon sp., called C-29EA, inhibits both protease (IC50 = 10.9 μg/mL) and helicase (IC50 = 18.9 μg/mL) activities of HCV, but not ATPase activity. Importantly, it has been shown that the highest inhibition on viral replication is derived from genotypes 1b and 2a with EC50 values of 1.5 and 24.9 μg/mL, respectively [68].
Psammaplin A (PsA) has antibacterial and antitumor activity and also inhibits a wide range of enzymes reported to date. PsA has the ability to inhibit HCV helicase catalyzed RNA unwinding (IC50 = 17 μM) in addition to ATPase and RNA binding activity. PsA inhibited the subgenomic viral replication derived from genotype 1b and genotype 2a, with EC50 6.1 and 6.3 μM, respectively [69].
Cholesterol sulfate might be a potential inhibitor of HCV NS3 helicase, with IC50 of 1.7 μM using RNA substrate. However, it exerted no ATPase and serine protease activity. A structure-activity study revealed that anion binding and hydrophobic region in NS3 may be targets of cholesterol sulfate [70].
Despite the great efforts, no potent and selective NS3 helicase inhibitors have been entered for clinical use. However, some good candidates, for example, soluble blue HT derivative, compound 12 [51], QU663 [54], and acridone derivatives [58, 59] have been identified to be suitable for further development as NS3 helicase inhibitors. It is not a surprise to imagine that NS3 helicase inhibitors will dominate HCV research in the near future.
5. Conclusions and Future Remarks
The direct-acting antiviral agents (DAAs), particularly NS3 protease inhibitors, telaprevir and boceprevir, which were approved in combination with current SOC (peg-IFN and ribavirin) for the treatment of HCV infection that significantly increased SVR, have opened a new window in HCV therapy. However, the side effects associated with this new therapy are a questionable maker. Anemia is the most frequent adverse effects with either telaprevir or boceprevir. They also exhibit strong inhibitory effect against an important drug metabolism enzyme, cytochrome P4503A4 (CYP3A4) resulting in the development of drug-drug interactions. In addition to drug resistance, the efficacies of these inhibitors differ significantly between HCV genotypes. It is well known that IFN itself has significant side effects. Another important issue arises with their short half-life and frequent dosing. With the advent of different small classes of DAAs, the future aim is to introduce an IFN-free regimen, oral cocktails of DAAs. The proof-of-concept studies presented some promising data confirming that the achievements of SVR without introducing IFN may be feasible. Thus, the combination of host and viral targeted inhibitors could be an attractive strategy in maximizing antiviral efficacy.
Conflict of Interests
The authors declare that they have no conflict of interests.
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