Predicting the therapeutic response in patients with chronic hepatitis C: the role of viral kinetic studies

Peter Ferenci*

Department of Internal Medicine IV, Gastroenterology and Hepatology, University of Vienna, Waehringer Guertel 18–20, A 1090 Vienna, Austria


    Abstract
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 Abstract
 Introduction
 Background
 Viral kinetics as a...
 Impact of adherence on...
 References
 
A substantial proportion of patients infected with hepatitis C virus (HCV) genotype 1 still does not respond to pegylated interferon-alfa/ribavirin (IFN/RBV) therapy. Factors which identify potential non-responders are needed to limit exposure to drugs in patients unlikely to benefit from treatment and to save health care resources. Host predictive factors have a low negative predictive value. In contrast, viral factors have a high precision in predicting outcome of therapy. Viral kinetics are the basis for the study of response of therapy. The decrease in viral load within 24 h after administration of a single test dose of conventional IFN reflects the IFN-sensitivity of the virus strain and predicts the outcome of conventional IFN/RBV therapy even before treatment with a specificity of 100% and a sensitivity of 83%. In contrast to conventional IFN, the two available PEG-IFN preparations differ considerably in how they suppress viral replication, and cut-off values have to be prospectively established separately for each drug. Patients without an early virological response (HCV-RNA either undetectable or decrease by >=2 log10 after 12 weeks) (EVR), do not achieve a sustained virological response (SVR; negative predictive value: 97–98%). Thus, in the absence of an EVR, treatment should be stopped. The outcome of PEG-IFN alfa-2a/RBV combination therapy is dependent on the rapidity of the virological response. Patients who become HCV-RNA negative after 4 weeks have the best chance of achieving an SVR. The rapidity of viral elimination may be a useful guide to tailoring the length of treatment in patients with an EVR.

Keywords: HCV, therapy, outcome prediction


    Introduction
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 Abstract
 Introduction
 Background
 Viral kinetics as a...
 Impact of adherence on...
 References
 
In the 15 years since characterization of the hepatitis C virus (HCV),1 understanding of the natural history of chronic hepatitis C has greatly expanded, and more effective therapeutic strategies have been developed. Sustained virological response (SVR) rates have been improved from >20% of patients treated for 48 weeks with conventional interferon (IFN) alfa, to {approx}40% of patients treated with the combination of IFN alfa-2b plus ribavirin,2,3 and 54–61% of patients treated with a pegylated IFN and ribavirin,46 the current treatment of choice.7 As a substantial proportion of patients do not respond to treatment, especially those infected with HCV genotype 1, much work remains to be done to optimize treatment for chronic hepatitis C.


    Background
 Top
 Abstract
 Introduction
 Background
 Viral kinetics as a...
 Impact of adherence on...
 References
 
The study of HCV dynamics is rooted in models developed to describe HIV infection,8 and has been facilitated by the development of sensitive and specific quantitative assays for HCV-RNA. Changes in viral load over time reflect changes in the production and/or elimination of the virus and allow the assessment of the ability of the infected host to clear the virus spontaneously and to respond to antiviral therapy.

The first line of host defence is the activation of multiple signalling cascades to produce cytokines that stimulate immune responses. To establish a chronic infection, the virus must bypass host defence mechanisms. IFNs are the most important components of the innate host defence. The interaction between HCV envelope protein E2 and double-stranded RNA-activated protein kinase (PKR) may be one mechanism by which HCV circumvents the antiviral effect of IFN.912 IFN regulatory factors (IRF) -3 and -7 are major regulators of IFN production.13 IRF-3 is directly activated after virus infection and stimulates the expression of alpha/beta IFN early in infection;14 IRF-7 amplifies the expression of other IFN genes in later stages of infection.15 A serine protease associated with the NS3/4 protein of HCV inhibits IRF-3 activation,16 and thereby IFN production. The interference of HCV with IFN activation and signalling results in IFN-resistant virus strains which are unlikely to respond to IFN-based therapies.

The early host defence can be investigated in patients acutely infected with HCV. Recently, 12 patients with acute hepatitis C were investigated.17 Although there was no difference in HCV-RNA titres at the onset of symptoms, HCV-RNA levels declined rapidly and continuously in patients who experienced spontaneous viral clearance but remained constant or increased after the onset of symptoms in those who did not clear the virus.17 In contrast to patients developing chronic hepatitis C, patients clearing the virus spontaneously have a vigorous cellular immune response to HCV.18,19 The mean time from exposure to the virus, and from the onset of symptoms, to HCV-RNA negativity was 77 and 35 days, respectively. Thus, repeated quantification of HCV-RNA levels identified patients not needing antiviral therapy.


    Viral kinetics as a tool to predict response to antiviral therapy in chronic hepatitis C
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 Abstract
 Introduction
 Background
 Viral kinetics as a...
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HCV-RNA levels in untreated patients with chronic hepatitis C do not vary over time20 and do not correlate with alanine aminotransferase (ALT) levels and liver histology,21 suggesting that a dynamic equilibrium exists in which virion production is balanced by viral elimination.20 IFN-based therapies reduce HCV levels by blocking viral replication, inhibiting release of virions and inducing immune clearance of infected cells.

Viral kinetics on treatment with conventional IFN

The initial biphasic decline in HCV-RNA can only be studied if IFN is continuously present (i.e. on daily IFN). The first decline in HCV-RNA levels is steep and becomes apparent within 24 h after the initiation of treatment and is the result of a blockade of virion production and release. The slope is dose-related over a range of 3–10 million units (MU) of conventional IFN alfa.22,23 Since it reflects the sensitivity of the virus strain to conventional IFN, it may predict the outcome of therapy even before treatment. A decrease of <70% in HCV-RNA levels within 24 h of a single 5 MU test dose of conventional IFN alfa correlated with non-response to a 48 week course of IFN alfa and ribavirin in patients infected with HCV genotype 1 or 4, with a specificity of 100% and a sensitivity of 83%.22,2426 The test is rarely used in the clinical setting. The greatest impact of IFN sensitivity testing is in clinical studies where it allows one to stratify patients to obtain homogenous study groups. It may also be of value if the indication for initiation of antiviral combination therapy is debatable.

The second elimination phase is slower and reflects immune-mediated clearance of HCV-infected cells. The slope of this phase is correlated with the probability of achieving a sustained virological response (SVR).27

Ribavirin increases SVR rates by an as yet unidentified mechanism. Ribavirin does not enhance the first or second viral elimination phases; however, a third elimination phase became apparent in some patients treated with peginterferon alfa-2a and ribavirin, but not in those treated with peginterferon alfa-2a alone.28 The slope of this phase was correlated with SVR rates, a phenomenon interpreted to represent enhanced degradation of infected cells.28

IFN sensitivity varies with HCV genotypes. The slope of the first phase decline is steeper in patients infected with HCV genotypes 2 or 3 than genotype 1.27,29 This correlates with the difference in SVR rates between these subgroups. Also the second phase response is steeper in patients harbouring HCV genotypes 2 or 3.27 The latter finding may explain why viral eradication may be accomplished in 24 weeks in these patients, whereas a full 48 week course of treatment is needed in patients infected with HCV genotype 1.5

Viral kinetic studies may explain why lower SVR rates are found in patients of African-American heritage compared with the overall population.30

Viral kinetics on treatment with pegylated IFNs

When conventional IFN alfa is administered on a thrice-weekly schedule, HCV-RNA levels fluctuate in concert with serum concentrations of the drug.27,31 Administering the drug on a daily basis dampens the fluctuations and provides more sustained suppression of HCV-RNA levels. Pegylated IFNs were developed, in part, to improve the pharmacokinetic properties of IFN and to allow for extended dosing intervals. The difference in pharmacokinetic properties between the two commercially available pegylated IFNs [Peginterferon alfa-2a (PEGASYS, Roche) and pegylated IFN alfa-2b (Pegintron, Schering Plough)] is reflected in distinct viral kinetics.

The extent of viral suppression mirrors serum levels of pegylated IFN alfa-2b. This drug has a terminal elimination half-life (t1/2) of {approx}40 h in patients with chronic hepatitis C, and serum concentrations generally fall below the limit of detection before the end of the 1 week dosing interval.32 Viral kinetic studies have revealed an association between the decrease in serum drug concentrations and a rebound in serum HCV-RNA levels.33,34 The decrease in HCV-RNA levels was dose-related in patients infected with HCV genotype 1; patients treated with 3 µg/kg of pegylated IFN alfa-2b had lower HCV-RNA levels at 24 and 48 h than those who received a 0.5 µg/kg dose (P < 0.001). Nonetheless, a significant rebound in HCV-RNA levels was observed in both groups.33 The rebound in HCV-RNA levels occurred between 48 and 72 h after once weekly administration of pegylated IFN alfa-2b. A similar rebound in HCV-RNA levels was observed in patients infected with HCV genotype 1 who were treated with pegylated IFN alfa-2b, 1.0 µg/kg per week, but was abrogated by twice-weekly administration of the same dose.34 Formann et al.34 measured serum levels of the drug and, similar to the results of a previous pharmacokinetic study,32 serum concentrations of pegylated IFN alfa-2b fell to below the limit of detection when the drug was administered once weekly, but remained relatively stable when given twice weekly. Taken together these results demonstrate that, when administered once weekly, serum concentrations of pegylated IFN alfa-2b decrease to the point at which HCV-RNA replication resumes and viral rebound occurs. The optimal regimen of the drug would presumably involve twice weekly administration of a higher dose, at least during a short induction phase.33,34

Peginterferon alfa-2a has a t1/2 of {approx}80 h and plasma levels of the drug are sustained with little peak-to-trough fluctuation. Thus, when given at the approved dose, 180 µg once weekly, suppression of HCV-RNA replication is generally maintained throughout the 1 week dosing interval. The viral kinetics and predictive value of IFN sensitivity testing differ between peginterferon alfa-2a and conventional IFN alfa. In patients infected with HCV genotype 1, the viral decline during the first 2 weeks of treatment with peginterferon alfa-2a 180 µg once weekly was somewhat lower than that reported for conventional IFN alfa.35 However, the viral rebound typical of alternate day administration of conventional IFN alfa or weekly administration of pegylated IFN alfa-2b was observed only in a minority of patients during treatment with peginterferon alfa-2a.35 The log change in HCV-RNA levels 24 h after the first dose of peginterferon alfa-2a was similar in those identified as responders and non-responders (log change in HCV-RNA >0.8 and <0.8, respectively) by sensitivity testing with conventional IFN alfa. Moreover, 50% of those identified as likely non-responders by IFN sensitivity testing had a virological response after 24 weeks of treatment with the combination of peginterferon alfa-2a and ribavirin.35 Thus, peginterferon alfa-2a may overcome predicted unresponsiveness to conventional IFN.

Clinical application of viral kinetics in the treatment of patients with chronic hepatitis C

Viral kinetics has a practical application in the management of patients with chronic hepatitis C (Figure 1). Very few patients without an early virological response (EVR), defined as undetectable HCV-RNA or >=2 log10 decrease in HCV-RNA levels after 12 weeks of combination therapy, achieve an SVR (negative predictive value: 97–98%). For this reason, HCV-RNA levels should be routinely measured after 12 weeks and, in the absence of an EVR, treatment should be stopped.7 This strategy limits exposure to drugs in patients unlikely to benefit from treatment and saves health care resources. As with conventional IFN/ribavirin combination therapy,36 the outcome of combination therapy with peginterferon alfa-2a and ribavirin is highly dependent on the rapidity of the virological response. Patients who become HCV-RNA negative after 4 weeks have the best chance of achieving a sustained virological response. It may be hypothesized that to decrease the frequency of relapse in the remaining patients, treatment longer than 48 weeks may be required.37



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Figure 1. Proposed model for predicting the duration of combination therapy with peginterferon alfa-2a and ribavirin.

 

    Impact of adherence on treatment response
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 Abstract
 Introduction
 Background
 Viral kinetics as a...
 Impact of adherence on...
 References
 
Patient adherence with combination therapy exerts a significant influence on SVR rates. Missed doses result in a relaxation of antiviral pressure and resumption of viral replication. In a retrospective analysis, patients with adherence rates of >=80% had higher SVR rates than those who were less adherent (i.e. those who consumed <80% of prescribed doses).38 Not surprisingly, the influence of adherence on SVR rates was most marked in patients infected with the more treatment-resistant HCV genotype 1 than in those infected with HCV genotypes 2 or 3. A failure to completely suppress HCV-RNA levels, or an increase in HCV-RNA levels detected by a sensitive and specific assay, may indicate poor adherence to a prescribed regimen, and illustrates the importance of monitoring HCV-RNA levels during treatment.

In summary, viral kinetic studies have provided an explanation for the differential responses according to HCV genotype and allow us to identify patients unlikely to respond to treatment early during therapy. Further research will refine our ability to individualize the dose and duration of therapy for particular patients, especially those infected with HCV genotype 1.


    Footnotes
 
* Tel: +43-1-40400-4741; Fax: +43-1-40400-4735; E-mail: peter.ferenci{at}akh-wien.ac.at Back


    References
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 Impact of adherence on...
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1 . Choo, Q. L., Kuo, G., Weiner, A. J. et al. (1989). Isolation of a cDNA clone derived from a blood-borne non-A, non-B viral hepatitis genome. Science 244, 359–62.[ISI][Medline]

2 . McHutchison, J. G., Gordon, S. C., Schiff, E. R. et al. (1998). Interferon alfa-2b alone or in combination with ribavirin as initial treatment for chronic hepatitis C. Hepatitis Interventional Therapy Group. New England Journal of Medicine 339, 1485–92.[Abstract/Free Full Text]

3 . Poynard, T., Marcellin, P., Lee, S. S. et al. (1998). Randomised trial of interferon alfa2b plus ribavirin for 48 weeks or for 24 weeks versus interferon alfa2b plus placebo for 48 weeks for treatment of chronic infection with hepatitis C virus. Lancet 352, 1426–32.[CrossRef][ISI][Medline]

4 . Fried, M. W., Shiffman, M. L., Reddy, K. R. et al. (2002). Peginterferon alfa-2a plus ribavirin for chronic hepatitis C virus infection. New England Journal of Medicine 347, 975–82.[Abstract/Free Full Text]

5 . Hadziyannis, S. J., Cheinquer, H., T. M., al. e. (2002). Peginterferon alfa-2a (40KD) (PEGASYS) in combination with ribavirin (RBV): efficacy and safety results from a phase III, randomized, double-blind, multicentre study examining effect of duration of treatment and RBV dose. Annals of Internal Medicine 193, in press.

6 . Manns, M. P., McHutchison, J. G., Gordon, S. C. et al. (2001). Peginterferon alfa-2b plus ribavirin compared with interferon alfa-2b plus ribavirin for initial treatment of chronic hepatitis C: a randomised trial. Lancet 358, 958–65.[CrossRef][ISI][Medline]

7 . National Institutes of Health. (2003). Consensus Development Conference Statement: Management of Hepatitis C: 2002—June 10–12, 2002. Hepatology 36, Suppl. 1, S3–20.[CrossRef][ISI]

8 . Perelson, A. S., Neumann, A. U., Markowitz, M. et al. (1996). HIV-1 dynamics in vivo: virion clearance rate, infected cell life-span, and viral generation time. Science 271, 1582–6.[Abstract]

9 . Gale, M. J. & Katze, M. G. (1998). Molecular mechanisms of interferon resistance mediated by viral-directed inhibition of PKR, the interferon-induced protein kinase. Pharmacology and Therapeutics 78, 29–46.[CrossRef][Medline]

10 . Taylor, D. R., Shi, S. T., Romano, P. R. et al. (1999). Inhibition of the interferon-inducible protein kinase PKR by HCV E2 protein. Science 285, 107–10.[Abstract/Free Full Text]

11 . Paterson, M., Laxton, C. D., Thomas, H. C. et al. (1999). Hepatitis C virus NS5A protein inhibits interferon antiviral activity, but the effects do not correlate with clinical response. Gastroenterology 117, 1187–97.[ISI][Medline]

12 . Heim, M. H., Moradpour, D. & Blum, H. E. (1999). Expression of hepatitis C virus proteins inhibits signal transduction through the Jak-STAT pathway. Journal of Virology 73, 8469–75.[Abstract/Free Full Text]

13 . Sen, G. C. (2001). Viruses and interferons. Annual Review of Microbiology 55, 255–81.[CrossRef][ISI][Medline]

14 . Grandvaux, N., Servant, M. J. & tenOever, B. et al. (2002). Transcriptional profiling of interferon regulatory factor 3 target genes: direct involvement in the regulation of interferon-stimulated genes. Journal of Virology 76, 5532–9.[Abstract/Free Full Text]

15 . Lin, R., Genin, P., Mamane, Y. et al. (2000). Selective DNA binding and association with the CREB binding protein coactivator contribute to differential activation of alpha/beta interferon genes by interferon regulatory factors 3 and 7. Molecular and Cellular Biology 20, 6342–53.[Abstract/Free Full Text]

16 . Foy, E., Wang, C., Sumpter, R. J. et al. (2003). Regulation of interferon regulatory factor-3 by the Hepatitis C virus serine protease. Science 300, 1145–8.[Abstract/Free Full Text]

17 . Hofer, H., Watkins-Riedel, T., Janata, O. et al. (2003). Spontaneous viral clearance in patients with acute hepatitis C can be predicted by repeated measurements of serum viral load. Hepatology 37, 60–4.[CrossRef][ISI][Medline]

18 . Gerlach, J. T., Diepolder, H. M., Zachoval, R. et al. (2003). Acute hepatitis C: high rate of both spontaneous and treatment-induced viral clearance. Gastroenterology 125, 80–8.[CrossRef][ISI][Medline]

19 . Holzmann, H., Aberle, J. H., Steindl-Munda, P. et al. (2003). Virus-specific CD4+ T cell responses in hepatitis C virus-infected patients with different genotypes. Poster presented at 54th Annual Meeting of the American Association for the Study of Liver Disease; October 24–28, 2003; Boston, MA, USA.

20 . Nguyen, T. T., Sedghi-Vaziri, A., Wilkes, L. B. et al. (1996). Fluctuations in viral load (HCV RNA) are relatively insignificant in untreated patients with chronic HCV infection. Journal of Viral Hepatitis 3, 75–8.[ISI][Medline]

21 . Zeuzem, S., Franke, A., Lee, J. H. et al. (1996). Phylogenetic analysis of hepatitis C virus isolates and their correlation to viremia, liver function tests, and histology. Hepatology 24, 1003–9.[ISI][Medline]

22 . Jessner, W., Gschwantler, M., Steindl-Munda, P. et al. (2001). Primary interferon resistance and treatment response in chronic hepatitis C infection: a pilot study. Lancet 358, 1241–2.[CrossRef][ISI][Medline]

23 . Lam, N. P., Neumann, A. U., Gretch, D. R. et al. (1997). Dose-dependent acute clearance of hepatitis C genotype 1 virus with interferon alfa. Hepatology 26, 226–31.[ISI][Medline]

24 . Jessner, W., Gschwantler, M., Formann, E. et al. (2003). Early viral kinetics in chronic hepatitis C virus genotype 4 infection. Paper presented at Digestive Diseases Week; May 17–22, 2003; Orlando, FL, USA.

25 . Ferenci, P. (2003). Weight based dosing of pegylated interferon-alfa in chronic hepatitis C—just a marketing ‘gag’? Digestive and Liver Disease 35, in press.

26 . Ferenci, P., Gschwantler, M., Laferl, H. et al. (2003). Prospective evaluation of the 24 hour interferon-induced decline in hepatitis C virus genotype 1 load to predict response to peginterferon-alfa2a/ribavirin combination therapy. Abstract. Gastroenterology 124, Suppl. 1, A767.

27 . Zeuzem, S., Herrmann, E., Lee, J. H. et al. (2001). Viral kinetics in patients with chronic hepatitis C treated with standard or peginterferon alpha2a. Gastroenterology 120, 1438–47.[ISI][Medline]

28 . Herrmann, E., Lee, J. H., Marinos, G. et al. (2003). Effect of ribavirin on hepatitis C viral kinetics in patients treated with pegylated interferon. Hepatology 37, 1351–8.[CrossRef][ISI][Medline]

29 . Neumann, A. U., Lam, N. P., Dahari, H. et al. (2000). Differences in viral dynamics between genotypes 1 and 2 of hepatitis C virus. Journal of Infectious Diseases 182, 28–35.[CrossRef][ISI][Medline]

30 . Layden-Almer, J. E., Ribeiro, R. M., Wiley, T. et al. (2003). Viral dynamics and response differences in HCV-infected African American and white patients treated with IFN and ribavirin. Hepatology 37, 1343–50.[CrossRef][ISI][Medline]

31 . Bekkering, F. C., Stalgis, C., McHutchison, J. G. et al. (2001). Estimation of early hepatitis C viral clearance in patients receiving daily interferon and ribavirin therapy using a mathematical model. Hepatology 33, 419–23.[CrossRef][ISI][Medline]

32 . Glue, P., Fang, J. W., Rouzier-Panis, R. et al. (2000). Pegylated interferon-alpha2b: pharmacokinetics, pharmacodynamics, safety, and preliminary efficacy data. Hepatitis C Intervention Therapy Group. Clinical Pharmacology and Therapeutics 68, 556–67.[CrossRef][ISI][Medline]

33 . Buti, M., Sanchez-Avila, F., Lurie, Y. et al. (2002). Viral kinetics in genotype 1 chronic hepatitis C patients during therapy with 2 different doses of peginterferon alfa-2b plus ribavirin. Hepatology 35, 930–6.[CrossRef][ISI][Medline]

34 . Formann, E., Jessner, W., Bennett, L. et al. (2003). Twice weekly administration of peginterferon-alfa-2b improves viral kinetics in patients with chronic hepatitis C genotype 1. Journal of Viral Hepatitis 10, 271–6.[ISI][Medline]

35 . Jessner, W., Stauber, R., Hackl, F. et al. (2003). Early viral kinetics on treatment with pegylated interferon-alpha-2a in chronic hepatitis C virus genotype 1 infection. Journal of Viral Hepatitis 10, 37–42.[CrossRef][ISI][Medline]

36 . Ferenci, P., Brunner, H., Nachbaur, K. et al. (2001). Combination of interferon induction therapy and ribavirin in chronic hepatitis C. Hepatology 34, 1006–11.[CrossRef][ISI][Medline]

37 . Ferenci, P., Fried, M. A., Chaneac, M. (2003). A dynamic model to predict sustained virological response to combination peginterferon alfa-2a (40KD) (PEGASYS®) and ribavirin (COPEGUS®) therapy in patients with chronic hepatitis C. Poster presented at the 54th Annual Meeting of the American Association for the Study of Liver Disease; October 24–28, 2003; Boston, MA, USA.

38 . McHutchison, J. G., Manns, M., Patel, K. et al. (2002). Adherence to combination therapy enhances sustained response in genotype-1-infected patients with chronic hepatitis C. Gastroenterology 123, 1061–9.[CrossRef][ISI][Medline]