151
|
Abstract
Despite improvements to treatments for HCV infection, almost half of patients cannot be cured with standard combination therapy (pegylated interferon alpha and ribavirin). The HCV life cycle offers a number of potential targets for molecular therapy, and several specifically targeted antiviral therapies for HCV (STAT-Cs) are in preclinical and clinical stages of development. Evidence to date suggests that monotherapy with any antiviral drug is unlikely to eradicate HCV infection. Combination therapy with interferon and ribavirin is necessary for the augmentation of antiviral drug activity and/or prevention of drug resistance. Results from clinical trials carried out in the past few years on STAT-C agents in combination with standard therapy with peginterferon and ribavirin provide great promise of higher rates of sustained virological response and, potentially, shorter duration of therapy than standard therapy alone achieves. Although pegylated interferon and ribavirin are likely to remain a cornerstone of therapeutic regimens in the short term, combinations of antiviral drugs of different classes, possibly along with novel agents that target host factors and modulate viral replication or augment antiviral defenses, offer the eventual possibility of interferon-free regimens.
Collapse
Affiliation(s)
- Arema A Pereira
- Weill Cornell Medical College, Center for the Study of Hepatitis C, New York, NY 10021, USA
| | | |
Collapse
|
152
|
Keeffe EB, Rossignol JF. Treatment of chronic viral hepatitis with nitazoxanide and second generation thiazolides. World J Gastroenterol 2009; 15:1805-8. [PMID: 19370775 PMCID: PMC2670405 DOI: 10.3748/wjg.15.1805] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Nitazoxanide, the first thiazolide, was originally developed for the treatment of Cryptosporidium parvum. More recently, antiviral activity of nitazoxanide against hepatitis B virus (HBV) and hepatitis C virus was recognized in in vitro systems. These basic studies led to phase II clinical trials that demonstrated the safety and efficacy of nitazoxanide in combination with peginterferon, with or without ribavirin, in the treatment of chronic hepatitis C genotype 4. The sustained virologic response rate was 79% and 80% in two studies, which was higher than the response rate of 50% with the standard of care with peginterferon plus ribavirin. In very preliminary studies of patients with chronic hepatitis B, nitazoxanide suppressed serum HBV DNA and led to loss of hepatitis B e antigen in the majority of patients and hepatitis B surface antigen in approximately a quarter of patients. Randomized controlled studies of naive and nonresponder patients with chronic hepatitis C genotype 1 are underway, new second generation and controlled release thiazolides are being developed, and future studies of patients with chronic hepatitis B are planned.
Collapse
|
153
|
Abstract
BACKGROUND The need for effective treatment for chronic hepatitis C infection has driven the development of novel antiviral agents that target specific steps in the viral replication cycle. AIM To evaluate the current literature concerning investigational agents for chronic hepatitis C virus infection. METHODS Resources used included PubMed, conference proceedings from the American and European Liver Associations' meetings 2005-2008 and the National Institute of Health's clinical trials website (http://www.clinicaltrials.gov). The focus was restricted to investigational agents that have progressed beyond preclinical development. RESULTS Over 50 investigational agents for chronic hepatitis C infection are currently in clinical development. Specifically targeted anti-viral therapy for HCV (STAT-C) shows great promise with NS3/4a protease inhibitors now entering phase 3 programmes. New interferon-alpha and ribavirin formulations aim to optimize anti-viral efficacy yet limit toxicity. Other candidates include novel immunomodulators and therapeutic vaccines. CONCLUSIONS A new era of therapy for chronic hepatitis C beckons, promising increased cure rates with shortened duration of therapy. However, the era will not be without challenges including viral resistance, drug toxicity and the need to optimize combination therapy in the face of a rapidly evolving therapeutic arsenal.
Collapse
Affiliation(s)
- A J V Thompson
- Division of Gastroenterology/Hepatology, Duke Clinical Research Institute, Duke University, Durham, NC 27715, USA
| | | |
Collapse
|
154
|
The octadecyloxyethyl ester of (S)-9-[3-hydroxy-2-(phosphonomethoxy) propyl]adenine is a potent and selective inhibitor of hepatitis C virus replication in genotype 1A, 1B, and 2A replicons. Antimicrob Agents Chemother 2009; 53:2660-2. [PMID: 19289518 DOI: 10.1128/aac.01546-08] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The octadecyloxyethyl (ODE) and hexadecyloxypropyl (HDP) esters of (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine (HPMPA) are potent inhibitors of orthopoxvirus, herpesvirus, human immunodeficiency virus type 1, and hepatitis B virus replication in vitro. HDP and ODE esters of (S)-HPMPA and (R)-HPMPA were evaluated for their activity in hepatitis C virus (HCV) replicon assays using luciferase (1B and 2A replicons) or RNA (1B) quantification. The ODE ester of (S)-HPMPA [ODE-(S)-HPMPA] was the most active compound, with 50% effective concentrations (EC(50)s) in the 0.69 to 1.31 microM range. HDP and ODE esters of (R)-HPMPA were severalfold less active, while (S)-HPMPA and (R)-HPMPA were inactive. In genotype 1A and 1B replicons analyzed by HCV RNA analysis, ODE-(S)-HPMPA was the most active compound, with EC(50)s of 1.8 and 2.1 microM, respectively.
Collapse
|
155
|
|
156
|
Rossignol JF, Elfert A, El-Gohary Y, Keeffe EB. Improved virologic response in chronic hepatitis C genotype 4 treated with nitazoxanide, peginterferon, and ribavirin. Gastroenterology 2009; 136:856-62. [PMID: 19135998 DOI: 10.1053/j.gastro.2008.11.037] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 11/07/2008] [Accepted: 11/13/2008] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Sustained virologic response (SVR) rates of 50%-60% have been achieved in patients with chronic hepatitis C genotype 4 treated with peginterferon plus ribavirin. The safety and efficacy of nitazoxanide plus peginterferon alfa-2a, with or without ribavirin, were evaluated in a randomized controlled trial at 2 centers in Egypt. METHODS Previously untreated patients with chronic hepatitis C and genotype 4 infection were assigned randomly to groups that were given standard of care (peginterferon alfa-2a and ribavirin for 48 weeks, n = 40), nitazoxanide monotherapy for 12 weeks followed by nitazoxanide plus peginterferon alfa-2a for 36 weeks (n = 28), or nitazoxanide monotherapy for 12 weeks followed by nitazoxanide plus peginterferon alfa-2a and ribavirin for 36 weeks (n = 28). Therapeutics included nitazoxanide (500 mg) twice daily, peginterferon alfa-2a (180 microg) once weekly, and weight-based ribavirin (1000-1200 mg/day). RESULTS The percentages of rapid virologic response (RVR), defined as undetectable HCV RNA at week 4 of combination therapy, and SVR were significantly higher in patients given the triple therapy compared with the standard of care (64% vs 38%, P = .048; and 79% vs 50%, P = .023; respectively). Patients given nitazoxanide plus peginterferon alfa-2a had intermediate rates of RVR (54%) and SVR (61%). Adverse events were similar across treatment groups except for higher rates of anemia in the groups receiving ribavirin. CONCLUSIONS The combination of nitazoxanide, peginterferon alfa-2a, and ribavirin increased the percentages of patients with RVR and SVR, compared with patients given peginterferon plus ribavirin, without an increase in adverse events.
Collapse
|
157
|
Meanwell NA, Kadow JF, Scola PM. Chapter 20 Progress towards the Discovery and Development of Specifically Targeted Inhibitors of Hepatitis C Virus. ANNUAL REPORTS IN MEDICINAL CHEMISTRY 2009. [DOI: 10.1016/s0065-7743(09)04420-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
|
158
|
Rossignol JF, Keeffe EB. Thiazolides: a new class of drugs for the treatment of chronic hepatitis B and C. Future Microbiol 2008; 3:539-45. [PMID: 18811238 DOI: 10.2217/17460913.3.5.539] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Nitazoxanide, the first thiazolide, was originally developed for the treatment of Cryptosporidium parvum. The antiviral activity of nitazoxanide was discovered by serendipity in patients with AIDS who were treated for cryptosporidial diarrhea and had HBV or HCV co-infection. In preliminary open-label studies of patients with chronic hepatitis B, nitazoxanide suppressed serum HBV DNA and led to loss or seroconversion of hepatitis B e antigen in the majority of patients, as well as hepatitis B surface antigen in approximately a quarter of patients. In Phase II studies of patients with chronic hepatitis C genotype 4, nitazoxanide combined with peginterferon alfa-2a, with or without ribavirin, increased the sustained virologic response rate to 79-80 versus 50% with peginterferon plus ribavirin standard of care. Randomized, controlled studies of naive and nonresponder patients with chronic hepatitis C genotype 1 and patients with chronic hepatitis B are underway, and new second generation thiazolides are being developed.
Collapse
|
159
|
|
160
|
Rossignol JF, Kabil SM, El-Gohary Y, Elfert A, Keeffe EB. Clinical trial: randomized, double-blind, placebo-controlled study of nitazoxanide monotherapy for the treatment of patients with chronic hepatitis C genotype 4. Aliment Pharmacol Ther 2008; 28:574-80. [PMID: 18616643 DOI: 10.1111/j.1365-2036.2008.03781.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
BACKGROUND Nitazoxanide, licensed in the US for treatment of Cryptosporidium parvum and Giardia lamblia, inhibits hepatitis C virus replication in replicon systems. AIM To evaluate the safety and efficacy of nitazoxanide monotherapy for the treatment of chronic hepatitis C. METHODS This multicentre, randomized, double-blind, placebo-controlled study randomized 50 adult patients with chronic hepatitis C genotype 4 at three centres in Egypt to nitazoxanide 500 mg tablet or placebo twice daily for 24 weeks. Patients were followed up every 4 weeks during treatment and for 24 weeks after therapy. RESULTS Seven of 23 patients (30.4%) in the nitazoxanide group achieved undetectable serum HCV RNA compared to 0 of 24 in the placebo group during therapy (P = 0.004). Each of the seven responders had baseline HCV RNA levels < or =400 000 IU/mL. Six of the seven virological responders were followed up for 24 weeks after the end of treatment, and four patients (17.4% of 23 treated) had a sustained virological response. Adverse events were similar in the nitazoxanide and placebo groups. CONCLUSION Nitazoxanide monotherapy is safe and effective in achieving sustained virological response in a modest number of patients with chronic hepatitis C genotype 4, particularly in patients with low baseline serum HCV RNA levels.
Collapse
Affiliation(s)
- J F Rossignol
- The Romark Institute for Medical Research, Tampa, FL, and Division of Gastroenterology and Hepatology, Department of Medicine, Stanford University School of Medicine, Stanford, CA, USA
| | | | | | | | | |
Collapse
|
161
|
Potential for hepatitis C virus resistance to nitazoxanide or tizoxanide. Antimicrob Agents Chemother 2008; 52:4069-71. [PMID: 18710916 DOI: 10.1128/aac.00078-08] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nitazoxanide and its primary metabolite, tizoxanide, inhibit hepatitis C virus (HCV) replication in HCV replicon systems. To study the potential for resistance, we subjected Huh7 cells harboring HCV replicons to serial passage in 250 muM G418 and increasing concentrations of nitazoxanide or tizoxanide. Passage of the replicon-containing cell lines in either compound resulted in increases in the 50% effective concentrations (EC(50)s) (7- to 13-fold), EC(90)s (14- to 36-fold), and 50% cytotoxic concentrations (2- to 4-fold) of both compounds. Serial passage in either compound did not alter the susceptibility of HCV replicons to ribavirin or 2'-C-methylcytidine. Interestingly, serial passage in nitazoxanide or tizoxanide resulted in increased sensitivity to alpha interferon 2b: EC(50)s and EC(90)s were reduced three- and eightfold, respectively. Replicons isolated from these cell lines had no greater ability to confer tizoxanide resistance, or increased susceptibility to alpha interferon, than replicons isolated from the parental cell line that had not previously been exposed to nitazoxanide or tizoxanide. These findings are indicative of a cell-mediated activity differing from that of other anti-HCV drugs but complementary with interferon and are consistent with the enhanced response rates observed clinically when nitazoxanide is combined with pegylated interferon therapy. Finally, unlike data for other compounds in advanced clinical development for HCV, these data are consistent with resistance in HCV replicon-containing cell lines conferred by changes in the host and not by mutations in the virus.
Collapse
|
162
|
|
163
|
Polyak SJ. Resistance of HBV and HCV to antiviral therapies. Future Virol 2008. [DOI: 10.2217/17460794.3.3.221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Stephen J Polyak
- University of Washington, Department of Laboratory Medicine, Virology 359690, 325 9th Avenue, Seattle, WA 98104, USA
| |
Collapse
|
164
|
De Clercq E, Field HJ. Antiviral Chemistry & Chemotherapy's Current Antiviral Agents FactFile 2008 (2nd Edition): RNA Viruses. ACTA ACUST UNITED AC 2008; 19:63-74. [DOI: 10.1177/095632020801900204] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Among the RNA viruses, other than the retroviruses (that is, HIV), which are dealt with separately in the current FactFile, the most important targets for the development of antiviral agents at the moment are the orthomyxoviruses (that is, influenza), the hepaciviruses (that is, hepatitis C virus [HCV]) and, to a lesser extent, the picornaviruses. Although the uncoating inhibitors amantadine and rimantadine were the first known inhibitors of influenza A, the neuraminidase inhibitors oseltamivir, zanamivir and peramivir have now become the prime antiviral drugs for the treatment of influenza A and B virus infections. For HCV infections, standard treatment consists of the combination of pegylated interferon-α with ribavirin, but several other antivirals targeted at specific viral functions such as the HCV protease and/or polymerase may be expected to soon take an important share of this important market. Still untapped is the potential of a variety of uncoating inhibitors, as well as protease and/or polymerase inhibitors against the wide spectrum of picornaviruses. While ribavirin has been available for 35 years as a broad-spectrum anti-RNA virus agent, relatively new and unexplored is favipiravir (T-705) accredited with activity against influenza as well as flaviviruses, bunyaviruses and arenaviruses.
Collapse
Affiliation(s)
| | - Hugh J Field
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| |
Collapse
|