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PREDICTORS OF A FAVORABLE RESPONSE TO ALPHA INTERFERON THERAPY FOR HEPATITIS C
TREATMENT OF CHRONIC HEPATITIS C
1089-3261/99 $8.00
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PREDICTORS OF A FAVORABLE RESPONSE TO ALPHA INTERFERON THERAPY FOR HEPATITIS C Eleanor Barnes, BSc, MRCP George Webster, BSc, MRCP, Simon Whalley, BMedSci, MRCP, and Geoffrey Dusheiko FCP(SA), FRCP, FRCP(Edin)
PREDICTIVE FACTORS FOR SUCCESSFUL INTERFERON THERAPY
Alpha interferon (IFN-a) alone and, more recently, IFN-a in combination with ribavirin are the only treatments that to date have been shown to be effective for the treatment of chronic hepatitis C virus (HCV) infection.*,7, 33 Large placebo-controlled trials have shown that only 15% to 20% of patients receiving IFN-a alone and 40% of patients receiving combination therapy can be expected to achieve a sustained virological response.2, Given these modest response rates, the side effects of treatment with IFN-a and the difficulties in administering IFNa by injection, it is important to consider selecting, if possible, those patients who are likely to respond to treatment. During the last decade, more than 35 controlled trials have published the results obtained with IFN-a, and many of these trials have identified predictive factors. The most important appear to be pretreat-
From the Department of Medicine, Division of Hepatology, Royal Free and University College School of Medicine, London, United Kingdom
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ment serum HCV RNA concentrations, pretreatment histology, and HCV genotype. Other factors that have been identified are 1. Drug regimen Dose greater than 3 million units (MU) three times a week Prolonged duration of treatment 2. An early response to IFN measured by alanine aminotransferase (ALT) and HCV RNA 3. Virus determinants Low level of circulating virus Genotype 2 or 3 Low number of quasispecies Multiple mutations in the interferon sensitivity determining region (NS5A) 4. Biochemical and histologic factors Elevated ALT level Absence of fibrosis and cirrhosis Low levels of hepatic iron 5. Negative HIV status 6. Demographic factors Age less than 40 years Female gender History of injection drug use Unknown source of infection Race 7. Short duration of infection
It is important at the outset to recognize the limitations of these predictive factors. Most data have been derived from the earlier trials of 6 months treatment with IFN-a monotherapy, and care must be taken in extrapolating these data to patients receiving combination therapy treatment or longer courses of IFN-a. Also, the earlier studies were conducted before HCV RNA testing was available and, therefore, looked only at the biochemical response. Hepatitis C virus RNA measurements have not been standardized, and concentrations may fluctuate spontaneously. The assay used to measure HCV RNA has become increasingly sensitive. Finally, definitions of treatment endpoints have been inconsistent. Despite these limitations, predictive factors have several clinical applications. Determining Treatment Algorithms
Although individual pretreatment predictive factors have a limited application, combinations of these factors may be useful. Davis et a1 applied an algorithm retrospectively to a large database of patients with chronic hepatitis C who had received standard doses of IFN-a6; this algorithm excluded patients with cirrhosis, genotype 1, or a high level of viremia from treatment. Although excluding these patients would
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have increased the response rate among those treated significantly and would have cut overall costs considerably, this strategy would, in theory, have denied treatment to 60% of the patients who in fact achieved a sustained response. The disappointing results of algorithms to date should not deter future attempts to identify an algorithm that can be usefully applied and thereby prevent patients from undergoing inconvenient and futile treatments. Doing so will be particularly challenging with constantly evolving treatment regimens.
Counseling Although predictive factors are not presently accurate enough to exclude patients from treatment, they do allow the clinician to give patients some idea of the likelihood of response to treatment based on the results of large controlled trials and thus to make a more informed decision regarding treatment.
Future Studies Predictive factors aid in study design, allowing randomization to be balanced for recognized predictive factors. Predictive factors also help investigators identify groups of patients who may benefit from alternative treatment regimens and so to plan future studies. For example, patients with genotype 1 or patients whose ALT levels remain elevated after 12 weeks of therapy may require higher drug doses or alternative treatment strategies.
Definitions
In this article the following definitions are used: End-of-treatment response (ETR) was previously known as complete response and is defined as normalization of ALT (end-oftreatment biochemical response) or loss of HCV RNA (end-oftreatment virological response) detected by polymerase chain reaction (PCR) at the end of treatment. Sustained response (SR) is defined as the normalization of ALT (sustained biochemical response), or loss of HCV RNA (sustained virologic response) detected by PCR 6 months after the end of treatment. No response (NR) is defined as the failure to normalize ALT or to lose HCV RNA detected by PCR by the end of treatment.
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THE RESPONSE TO INTERFERON AND THE DURATION AND DOSE OF TREATMENT
During the last decade, clinical trials have attempted to establish the optimum dose and duration of IFN-a monotherapy required for a sustained virologic response. It is probable, however, given the recently published reports of improved response rates, that many patients will now be offered IFN-a in combination with ribavirin as initial therapy? 42 The optimum dosage and duration of IFN therapy may be different for IFN monotherapy than for IFN given in combination with ribavirin. Better results seen with longer courses and higher doses of IFN need to be weighed against the disadvantages of the added inconvenience and cost of prolonged treatment and the inevitable increase in side effects seen with higher doses. Direct interstudy comparisons are difficult, and the results must approached cautiousIy because of the differences in study populations, particularly in terms of genotype, pretreatment RNA levels, degree of pretreatment fibrosis, and the differing types of IFN used.
Monotherapy
Large, placebo-controlled trials for hepatitis C using IFN-a monotherapy were first published in 1989.2, These trials clearly demonstrated that 50% of patients who achieved a biochemical ETR relapsed within 6 months of stopping treatment. These trials also established that IFN given at a dose of 3 million units (MU) three times a week for 6 months resulted in a SR of 23% and that lower doses (2 MU or 1 MU three times a week) given for 6 months resulted in lower SR (loo/, and 15%, respectively).Recently published response rates after 6 months treatment have been even lower than this; in the IFN-a monotherapy arm (231 patients, 72% genotype 1) of the recently published combination trials with ribavirin and IFN, the SR rate in patients treated for 6 months was only 69'0.~~ The therapeutic benefit of higher doses of IFN-a have been studied. Lindsay et a1 showed no increase in response rates at 12 weeks with doses of IFN higher than three times a week (eg., 5 MU or 10 MU three times a week). Although there was a marginal increase in the SR rate after 6 months of treatment at these higher doses, the side effects were difficult for patients to tolerate.25 Several meta-analyses of the numerous clinical trials published during the last decade have attempted to derive the optimum dose and duration of treatment needed to achieve a SR.6,41 Poynard analyzed 17 trials comparing different IFN regimens and 16 trials comparing IFN with There was a significant dose effect (6 MU versus 3 MU three times a week) at 12 months, but not at 6 months of treatment, with an increase in the SR of 17%.There was also a duration effect (12 months
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versus 6 months) at both the 3 MU (increase in SR of 16%) and the 6 MU dosages (increase in SR of 20%). This analysis concluded that the best efficacy/risk ratio favored the regimen of 3 MU three times a week for 12 months. The National Institutes of Health Consensus Development Conference provided an analysis of the responses to different types of IFN-Ix.*~ A meta-analysis of all 32 available randomized clinical trials of interferon alpha-2b (IFN-aw2b) published between 1986 and 1997 using doses of at least 2 MU three times a week for 24 weeks concluded that extended therapy for 12 to 24 months resulted in a significant improvement in SR compared with 6 months (27% versus 14%) and that doses above 3 MU three times a week resulted in a modest improvement of SR (28% versus 190/,).An analysis of interferon alpha-2a (IFN-a2a) trials suggested that the combination of longer periods of treatment and induction using higher initial doses significantly improved the SR. The optimum regimen of interferon alpha-nl (IFN-anl) has also been shown to be 3 MU three times a week for 12 months and produces SR equivalent to the best found with other alpha interferons. Both pulsed dosing (a 3-month course of IFN, followed by 6 months of no treatment and then by another 3-month course of IFN) and escalation in therapy when responses at standard doses are not obtained have 44 been shown to be ineffective treatment strategies.36, Direct study comparisons of IFN monotherapies are difficult, but the regimen that has been adopted by most clinicians is to begin a trial of treatment with IFN-a at a dose of 3 MU three times a week and, if a biochemical or virological response is observed after 12 weeks of therapy, to continue treatment for at least 12 months in total. There is a trend for patients with genotype 1 with or hepatic fibrosis to respond better to higher doses. The same treatment regimen may not be optimal for all patients, and future therapy may be individually tailored, based on such factors as genotype and degree of fibrosis. Interferon alphacon-1 (consensus interferon, IFN-a con-1) at a dose of 9 k g may induce a greater reduction in HCV RNA titres during treatment than IFN-a2b and slightly higher, albeit still unsatisfactory, sustained virologic response rates have been observed with IFN-a con-1 in patients with higher HCV RNA concentrations and genotype l.23Pegylated alpha interferons are under investigation. Preliminary data suggest that relatively high initial virological response rates are obtained, pointing to an enhanced antiviral effect of the sustained-delivery of alpha interferons. Combination Therapy
Ribavirin is a synthetic nucleoside analogue with in vitro action against RNA and DNA viruses. When given alone to patients with chronic hepatitis C, it decreases serum ALT concentration but has little antiviral effect.", l2 In 1998, the first major trials using IFN-a in combination with
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ribavirin were published.s,33, 42 These trials have demonstrated a considerable improvement of the virologic SR rate using combination therapy, both in IFN-naive patients and in patients who have previously experienced relapse on IFN monotherapy. The mechanism of action of ribavirin in combination with IFN remains unknown. McHutchinson et a1 randomly assigned 912 patients to IFN-a2b monotherapy at a dose of 3 MU three times a week or the same dose of IFN combined with ribavirin at a dose of 1 to 1.2 g daily, depending on patient weight, for 24 or 48 weeks.33The virologic SR rate was 31% for combination therapy given for 24 weeks, 38% for combination therapy given for 48 weeks, 6% with IFN-a2b alone given for 24 weeks, and 13% with IFN-a2b alone given for 48 weeks. Histological improvement was more common in patients treated with combination therapy. Drug doses needed to be reduced or discontinued because of side effects more often in the group receiving combination therapy than in the group receiving IFN monotherapy. Impressively, it has also been shown that 49% patients who had previously experienced relapse on IFN-a monotherapy responded to 6 months of combination therapy at the above doses.8 These results are very encouraging and will no doubt stimulate further interest in trials of combination therapy for HCV infection. There is considerable interest in induction with high doses of IFNa and ribavirin. However, there are insufficient data to indicate whether the relatively high early response rates will translate into higher sustained response rates. PREDICTION OF A SUSTAINED RESPONSE BY AN EARLY RESPONSE TO TREATMENT Monotherapy It has been consistently shown that patients who achieve a virologic SR with IFN-a monotherapy will have normal ALT levels at 8 to 12 weeks and failure to achieve normal ALT levels within this period indicates that the patient will not respond to further IFN treatment.7 Unfortunately 50% of patients who achieve normal ALT levels within 8 to 12 weeks'will subsequently experience relapse and fail to achieve a SR.*f7 Early loss of HCV RNA has been reported to be a better marker of a virological SR than normalization of the serum ALT. Orito et a1 showed that 17 of 19 patients who achieved a SR after 6 months of treatment with IFN-a (10 MU daily for 2 weeks followed by 10 MU three times a week for 22 weeks) cleared HCV RNA, measured by PCR, at 4 weeks. In contrast, 9 of 19 patients who achieved a SR had normal ALT levels at 4 weeks.39A study of 36 patients treated with 6 months of IFN-a, 6 MU three times a week showed undetectable HCV RNA at 2 weeks in 8 of the 10 patients who achieved a SR but in only 1 of 26 patients who had no response to treatment.20It has been shown that the most effective
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time to measure HCV RNA to predict a SR is 12 weeks into treatment, when loss of HCV RNA accurately predicts biochemical and virological SR in 85% and 91% of patients, respectively, although earlier measurements predicted a SR almost as well.32 It may be that a virologic SR depends not so much on early loss of HCV RNA but rather on the length of time that IFN therapy is continued after HCV RNA becomes undetectable. In support of this hypothesis, prolonged courses of treatment are associated with a SR, but further studies are necessary to confirm this possibility. Combination Therapy
In patients receiving combination therapy, relatively late clearance of HCV RNA from serum is frequently associated with a virological SR, and stopping treatment at 12 weeks because of persistent viremia may not be appropriate. McHutchinson et a1 found that among 51 of 87 patients (59%)who were treated with combination therapy for 48 weeks and who eventually achieved a SR, HCV RNA remained detectable, by sensitive reverse transcription polymerase chain reaction (RT-PCR) until 12 to 24 weeks of therapy. Later viral clearance was also found in 35 of 70 patients (50%) treated with combination therapy for 24 weeks.33In contrast with these findings, Davis et a1 randomly assigned 345 patients, who had previously experienced relapse following IFN-a treatment, to combination treatment or IFN monotherapy and found that all patients who achieved a SR had undetectable HCV RNA levels at 12 weeks.8 PRETREATMENT LEVELS OF HEPATITIS C VIRUS RNA PREDICT RESPONSE TO ALPHA INTERFERON
Lower pretreatment levels of HCV RNA have been shown to predict a sustained response to both IFN-LY monotherapy and to IFN-a in combination with ribavirin. A meta-analysis of 652 patients in 11 placebocontrolled trials showed that pretreatment HCV RNA levels of less than 1 X lo6 genomes/mL resulted in a virological SR in 50.5% of patients treated with IFN-LY compared with only 17.3% of patients whose pretreatment levels were higher than 1 X lo6 genomes/mL. However, the ETR and SR were not significantly different if the analysis was confined to studies using only a single assay technique, or if the HCV RNA level as measured by branched DNA was adjusted for genotype. The positive predictive value of a low HCV RNA level for a virologic SR was only 71%. In the study by McHutchinson et a1 of ribivarin and I F N - L Y combi~~ nation therapy 912 patients were stratified by their pretreatment RNA In all treatment groups, patients with a high pretreatment viral load (> 2 x lo6 copies/mL) had a lower rate of virologic SR than patients with a viral load less than 2 X lo6 copies/mL. Among patients
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with a high viral load, however, the virologic SR was significantly higher in patients treated with combination ribavirin and IFN-a2b therapy than in patients who received IFN-a2b monotherapy. Similarly Davies et a1 randomly assigned 345 patients who had previously experienced relapse after IFN-a2b monotherapy to receive combination IFN-a2b and ribavirin therapy or IFN-a2b monotherapy.s Again, patients with baseline serum HCV RNA levels of less than 2 X lo6 copies/mL were associated with a higher rate of virologic SR in both treatment groups. Patients treated with combination therapy rather than IFN-a2b alone were more likely to have a SR, regardless of their pretreatment RNA level.
GENOTYPE AS A PREDICTIVE FACTOR FOR THE RESPONSE TO INTERFERON
In the United States, as many as 70% of patients with HCV have genotype 1 infection. Patients with genotype l a and l b have been consistently shown to have a poorer response to treatment with both IFN-a monotherapy and IFN-a in combination with ribavirin than patients with genotype 2 or 3.3Or42 In Western Europe, a higher biochemical SR rate has been observed in hepatitis C patients infected with genotype 2 or 3 rather than genotype lj7 In a meta-analysis of 15 studies that reported a SR after IFN-a monotherapy, SR was achieved in 18.1% of 536 patients infected with genotype 1, but 54.9% of the 288 patients infected with genotype 2 or 3 had a SR.6 The predictive value of genotypes other than type 1 for a SR to IFN-a therapy was low (55%), emphasizing the restricted value of genotype as a predictive factor for response to treatment. Interferon-naive patients infected with all HCV genotypes, including type 1, have been shown to achieve a SR more often with combination ribavirin and IFN-a therapy than with IFN monotherapy.32,33 Nonetheless, even with combination therapy, treatment-naive patients infected with HCV genotype 1 are less likely to achieve a SR than patients infected with HCV genotype 2 and 3. In treatment-naive patients infected with HCV genotype 1, treatment with combination therapy for 48 rather than 24 weeks significantly improves the SR (28% versus 16%), but for patients infected with HCV genotypes 2 and 3 treated with Combination therapy, extending treatment for 12 rather than 6 months does not significantly improve the SR. Thus, genotyping could shorten the duration of treatment for treatment-naive patients infected with HCV genotype 2 and 3 and result in a substantial cost savings. Similarly, it has been shown that patients infected with any HCV genotype who have previously experienced relapse on IFN-a alone have an improved SR rate if treated with 24 weeks of combination therapy rather than 24 weeks of IFN-a alone, but patients infected with HCV genotype 1 who have experienced relapse after treatment with IFN-a monotherapy are less likely to achieve a SR than patients with genotype 2 or 3 (30%
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versus 73%, respectively), when treated subsequently with combination therapy.s QUASISPECIES AND THE RESPONSE TO ALPHA INTERFERON THERAPY
The HCV population in an infected individual is composed of heterogeneous but related genomic variants called quasispecies. The genetic complexity is the total number of genetic variants within the quasispecies population. The analysis of the genetic complexity of quasispecies may reveal mechanisms of resistance to antiviral therapy. The determination of IFN-resistant quasispecies may make it possible to predict the efficacy of IFN therapy. A hypervariable region (HVR) has been reported in the NH2-terminal of the E2 envelope gene of the HCV genome, in which marked diversity is found among different HCV isolates. Several studies have found that increased genetic complexity of the HVR is associated with a poor response to IFN-a therapy.17, 23, 36 This region is so variable, however, that no specific sequence correlates with IFN effecti~eness.~~ Multivariate analysis indicates that low genetic complexity of HVRl is an independent parameter predictive of a SR to IFN-a.35740*49 THE INTERFERON SENSITIVITY-DETERMINING REGION
Preliminary studies indicated that various HCV quasispecies might have different sensitivities to IFN-a,34 and thus may contain genomic regions predictive of response to IFN-CY therapy. Studies in Japan first identified a region of the HCV genome where mutations correlated with sensitivity to IFN-a. This putative region, termed the interferon sensitivity-determining region (ISDR), was identified in the carboxy-terminal half of the nonstructural protein 5A (NS5A) gene between codon 2209 and 2248 of HCV-J, a strain of HCV-lb whose complete genomic sequence has been identified. In 84 patients with chronic HCV-lb, after 6 months of IFN-a therapy, a SR did not occur in any of 30 patients whose NS5A 2209-2248 sequence was identical to that of HCV-J (wild type). Five of 38 patients (13%)with one to three changes in NS5A 2209-2248 (intermediate type) had a SR, as did all 16 patients with 4 to 11 amino acid substitutions (mutant type), indicating that the mutant type was significantly associated with a SR to IFN-a.14Interestingly, in the Japanese studies, mutant type ISDR correlated closely with low levels of serum HCV RNA, suggesting that replication may be reduced by these mutations. In a European study of patients with chronic HCV-lb, it was observed that although some sequence variations were found in the NS5A region, no clear differences could be directly correlated with interferon
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~ensitivity.'~Sensitive strains, however, exhibited more amino acid changes than a consensus sequence from all strains. Most of the variations occurred in the carboxy-terminal region, and especially in the previously reported NS5A/V3 region. Moreover, conformational analysis of NS5A by secondary structure prediction allowed the most sensitive strains to be differentiated from resistant ones. It was concluded that regions other than the ISDR were involved in resistance to IFN-a, perhaps through an interaction between NS5A and an IFN-induced protein kinase. In contrast with the Japanese studies, several European studies have shown a low response rate to IFN-a therapy in patients infected with HCV genotype 1. Perhaps the explanation for this poor response to IFNa is the finding that few European patients have four or more amino acid substitutions in the NS5A 2209-2248 region.51 Although the ISDR is of potential biologic interest, analysis of this region can not be recommended for routine clinical practice. PRETREATMENT ALANINE AMINOTRANSFERASE LEVELS AND THE RESPONSE TO INTERFERON
It has been estimated that approximately 25% of patients with chronic HCV (defined as anti-HCV-positive and with HCV RNA detectable by PCR) have persistently normal ALT levels.28These patients are generally asymptomatic but show histologic evidence of chronic hepatitis on biopsyz7Several studies have assessed the virologic characteristics in these patients and have shown that viral load, genotype, and quasispecies complexity are similar to those of patients with elevated ALT 46 In these patients it would appear that the degree of c~ncentration.~~, hepatic inflammation, reflected in the ALT level, is determined at least in part by host immunological responses. The natural history of these patients is not well documented, and long-term prospective studies are required, but it would seem that the development of significant fibrosis in these patients is rare.27 Trials to determine the response to IFN-a have usually excluded patients with normal ALT levels. A few, very small, mostly uncontrolled trials have attempted to determine the response to IFN in these patients.28Overall, the virological SR rate appears to be similar to the results seen in the large trials of IFN-a in patients with high ALT levels. None of these trials has demonstrated histologic improvement with therapy, and, of concern, these patients may develop elevated ALT levels that can persist after treatment has been stopped. Therefore, although IFN-a therapy may induce a virologic response in a few of these patients, treatment may be detrimental to others. Until prospective, large, placebo-controlled trials have been performed using combination therapy and the natural history of disease is better understood, treatment with IFN-a cannot generally be recommended for patients with normal ALT levels.
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PRETREATMENT FIBROSIS OR CIRRHOSIS AND THE RESPONSE TO INTERFERON
Approximately 20% to 30% of patients with HCV infection develop cirrhosis after 20 to 30 years of infection and, although sustained viral clearance with IFN-a will not reverse the degree of fibrosis, it may be worthwhile in arresting disease progression.21Recent reports have also suggested that viral clearance in patients with cirrhosis may reduce the risk of developing hepatocellular carcinoma.15This finding is controversial and is discussed in detail subsequently. Compensated Cirrhosis
Idilman et a1 recently reviewed 26 published studies to assess the response to IFN-a in patients with compensated cirrhosis.21Of the 1315 patients studied, 434 (33%)had histologically documented cirrhosis, and 884 (67%) had chronic hepatitis without cirrhosis. Data on HCV RNA results were limited to 153 patients with cirrhosis and 297 patients without cirrhosis. A virological response occurred in 5% to 10°/~of the patients with cirrhosis, compared with 20% to 35% of patients without cirrhosis. Other studies of IFN-a in combination with ribavirin have included patients with compensated cirrhosis and have shown that these patients have an increased rate of SR when treated with combination therapy compared with IFN monotherapy.8, 42 Poynard et a1 found that patients with septa1fibrosis or cirrhosis showed a decreased response to combination treatment given for either 24 or 48 weeks compared with patients without fibrosis or with portal fibrosis only." Other studies, however, have not identified the presence of fibrosis as a predictive factor for a response to combination treatment.8,33 337
Decompensated Cirrhosis
The efficacy of IFN-a in patients with decompensated cirrhosis is unclear, because these patients have been excluded from prospective, randomized trials. It is known, however, that these patients can experience severe side effects when treated with IFN-a, and thrombocytopenia or leukopenia may preclude therapy. At present, IFN treatment cannot be recommended for these patients, particularly for those who are candidates for transplantation. HEPATIC IRON AND THE RESPONSE TO INTERFERON
Elevated hepatic iron concentration (HIC) is reported in 10% to 29% of patients with chronic HCV infection.36,43 The mechanisms by which
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iron may effect hepatotoxicity in patients with HCV infection are uncertain and controversial, but possibilities include increased lipid peroxidation and oxidative stress, enhanced rates of viral replication, or effects on host imrn~nity.~ The effect of liver iron content on response to IFN-a therapy in patients with chronic HCV infection and the merits of iron depletion are presently under investigation. Liver iron content has been shown to influence the response to IFNa in patients with chronic hepatitis C. In a study of 79 patients with chronic hepatitis, 54 of whom had hepatitis C, the HIC was twice as high in the patients who did not respond to 6 months of IFN-a therapy (43%) compared with patients who had a biochemical ETR or a partial biochemical response (defined as a decrease in ALT of more than 50%) (57Y0).~' In an extension of this work, Olynk et a1 studied 58 patients with chronic hepatitis C, of whom 24 (41%) responded to IFN-a treatment.3s Although HIC was generally in the normal range, and no correlation between iron content and histological stage was seen, mean HIC was significantly higher in patients who did not respond to treatment. Nonresponse to IFN-a was seen in 88% of patients with HIC greater than 1100 pg/g dry weight of liver. The response to IFN-a in patients with HCV and thalassemia major, who usually have significant iron overload caused by multiple transfusions, has also been shown to be inversely related to liver iron content.41 On histological examination, the absence of stainable iron is associated with SR to IFN-a, and the pattern of staining, if present, appears to be important. Deposition of iron in portal endothelial cells has been shown to be a strong predictor of a poor response to treatment.' If high HIC is associated with poor response to IFN-a treatment in patients with chronic HCV infection does iron depletion improve this response? A number of small studies have sought to answer this question. It appears that venesection alone reduces the serum ALT level, but does not affect the HCV RNA level.'O, In a study of the effect of venesection on subsequent response to antiviral therapy, Fong et a1 randomly assigned 38 patients with chronic HCV infection to a course of venesection or to no iron depletion.16All patients then received IFNa therapy for 6 months. Significant reductions in ALT levels were seen after venesection. No significant differences in HCV RNA ETR were seen in the small number of patients studied, but there was a trend towards an improved SR in the venesected group after 6 months of follow-up ( P = 0.07). Five-year follow-up of patients who were maintained as iron deficient after unsuccessful IFN-a therapy has suggested sustained biochemical improvement, slower histologic progression, and possibly a lower frequency of HCC than in the nonvenesected group.19 Evidence that venesection may reduce the frequency of HCC in patients with chronic HCV is preliminary, although iron deposition has been shown to be more frequent in HCV-positive cirrhotic patients with HCC than in cirrhotic patients without HCC.4 Certain conclusions about iron and treatment response in chronic HCV may be drawn. Increased serum and liver markers of iron are
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common in patients with HCV infection, and iron may have an additive role in the hepatotoxicity of HCV. The pathological mechanisms underlying the effects of liver iron in patients with HCV infection are incompletely understood. Liver iron content is inversely associated with response to IFN-a therapy, and this inverse association appears to be independent of histological stage or grade of disease. Finally, iron reduction therapy consistently reduces serum ALT levels in patients with HCV infection, with or without the addition of IFN-a. Clear evidence that venesection improves virological SR is lacking, and thus venesection cannot be recommended at present.
HUMAN IMMUNODEFICIENCY VIRUS INFECTION AND RESPONSE TO INTERFERON
Early studies showed that IFN-a was ineffective in treating patients chronically infected with hepatitis B virus (HBV) who were also infected with HIV.31Discouraged by these early results, trials to determine the response of patients infected with HCV to IFN-a therapy have generally excluded patients with HIV disease; therefore, data on patients with HIV infection are generally limited to small uncontrolled studies. Concurrent infection with HCV and HIV is not uncommon, especially in populations where intravenous drug abuse is the usual mode of transmission of HIV disease. Chronic hepatitis C is reported to cause more severe liver disease and to progress more rapidly to cirrhosis in patients coinfected with HIV.29The life expectancy of patients with HIV disease has dramatically increased recently because of more effective combination therapies against HIV, so that coexistent diseases in HIV patients have become of more concern. The need for effective treatment of HCV in these patients is likely to increase. The lack of efficacy of IFN-a against HBV in patients coinfected with HIV was thought to be related to the absence of an immunomodulatory response.31In patients with chronic hepatitis C, the effect of interferon seems to be at least partly related to a direct antiviral mechanism, so that a beneficial effect in HIV- and HCV-positive patients might be expected. A controlled study by Soriano et a1 assessed the efficacy of IFN-a in 57 patients with HCV infection who were coinfected with HIV but who had CD4 counts above 200/mm3.48The SR rate in these HIVinfected patients was not significantly different from that of the control group of patients without HIV infection (38% versus 47%). A lack of response to IFN-a in the HIV-positive patients was associated with CD4 counts below 500 mm3. Alpha interferon was generally well tolerated in the HIV-positive patients, although during the first 14 weeks of treatment with IFN-a 3 patients experienced a very rapid decline in the CD4 counts that only partially recovered when treatment was stopped.
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Although there may well be a place for IFN-a treatment in patients coinfected with HCV and HIV, more information is required to establish the SR rates for both IFN-a monotherapy and combination therapy, the effects of IFN-a on CD4 cells, and the possible interactive toxicities of IFN-a and ribavirin with antiretroviral therapy. DEMOGRAPHIC FEATURES
Age younger than 40 years, female gender, short duration of infection, and route of infection have been inconsistently identified as factors which predict the response to IFN. In a recent report, Reddy et a1 suggested that response rates may be lower in blacks than in whites or Asians with genotype 1 infection^.^^" SUMMARY
The most consistently identified predictive factors for a response to both IFN-a monotherapy and IFN-a in combination with ribavirin are a low HCV RNA level, the absence of fibrosis, infection with HCV genotype 2 and 3, and a prolonged duration of treatment. In addition, an early response to IFN-a predicts response to IFN-a monotherapy but not necessarily to combination therapy. There does not appear to be any major gain in treating IFN-naive patients with HCV genotype 2 or 3 infection with a combination of IFN-a and ribavirin for longer than 6 months. The identification of these predictive factors has allowed improvement in study design and assessment and may provide a patient with an idea of the likelihood of response, making possible a more informed decision regarding treatment. At present, none of these factors, either alone or in combination, completely predicts response to IFN-a. Thus, individual patients should not be denied treatment on the basis of these factors.
References 1. Barton AL, Banner BF, Cable EE, et al: Distribution of iron in the liver predicts the response of chronic hepatitis C infection to interferon therapy. A m J Clin Pathol 103419-424, 1995 2. DiBisceglie A, Martin P, Kassianides C, et al: Recombinant interferon alpha therapy for chronic hepatitis C. N Engl J Med 321:1506-1510, 1989 3. Bonkovsky HL, Banner BF, Rothman AL: Iron and chronic viral hepatitis. Hepatology 25:759-768, 1997 4. Chapoutot C, Laurent C, Ramos J, et a1 Significant correlation between liver iron deposition and hepatocellular carcinoma in patients with viral C cirrhosis: Study of 104 patients. Hepatology 28248, 1998 5. Clemente MG, Congia M, Lai ME, et al: Effect of iron overload on the response to
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recombinant interferon-alpha treatment in transfusion-dependent patients with thalassaemia major and chronic hepatitis C. J Pediatr 125:123-128, 1994 6. Davis G, Lau J: Factors predictive of a beneficial response to therapy of hepatitis C. Hepatology 26(suppl 1):112S127S, 1997 7. Davis GL, Balart LA, Schiff ER, et al: Treatment of chronic hepatitis C with recombinant Interferon Alfa. N Engl J Med 321:1501-1506, 1989 8. Davis G, Esteban-Mur R, Mustgi V, et al: Interferon alfa-2b alone or in combination with ribavirin for the treatment of relapse of chronic hepatitis C. N Engl J Med 339~1493-1499,1998 9. Di Bisceglie AM, Axiotis CA, Hoofnagle JH, et a1 Measurements of iron status in patients with chronic hepatitis. Gastroenterology 102:2108-2113, 1992 10. Di Bisceglie AM, Bonkovsky H, Krawit E, et al: Iron reduction therapy in chronic hepatitis C. Hepatology 26:214A, 1997 11. Di Bisceglie AM, Conjeevaram HS, Fried MW, et al: Ribavirin as therapy for chronic hepatitis C: A randomised, double blind placebo controlled trial. Ann Intern Med 123:897-903, 1995 12. Dusheiko G, Main J, et a1 Ribavirin treatment for patients with chronic hepatitis C: Results of a placebo controlled study. J Hepatol 25:591-598, 1996 13. Duverlie G, Khorsi H, Castelain S, et a1 Sequence analysis of the NS5A protein of European hepatitis C virus l b isolates and relation to interferon sensitivity. J Gen Virol 7911373-1381, 1998 14. Enemoto N, Sakuma I, Asakina Y, et a 1 Comparison of full length sequences of interferon sensitive and resistant hepatitis C virus lb. J Clin Invest 96224-230, 1995 15. Fattovivich G, Giustina G, Degos F, et a1 Effectiveness of interferon-alpha on incidence of hepatocellular carcinoma and decompensation in European patients with cirrhosis type C. J Hepatol 27201-205, 1997 16. Fong T-L, Han SH, Tsai N C-S, et a 1 A pilot randomized, controlled trial of the effect of iron depletion on long-term response to a-interferon in patients with chronic hepatitis C. J Hepatol 28:369-374, 1998 17. Gonzalez-Peralta RP,Liu WZ, Davis GL, et a1 Modulation of hepatitis C virus quasispecies heterogeneity by interferon-alpha and ribavirin therapy. J Viral Hepat 4:99106, 1997 18. Hayashi H, Takikawa T, Nishimura N, et a1 Improvements of serum aminotransferase levels after phlebotomy in patients with chronic hepatitis C and excess hepatic iron. Gastroenterology 89:986-988, 1994 19. Hayashi H, Wakusawa S, Takikawa T, et al: Long term effect of iron removal on chronic hepatitis C. Hepatology 26:215A, 1997 20. Hino K, Okuda M, Korishi T, et al: Serial assay of hepatitis C virus RNA in serum for predicting response to IFN alpha therapy. Dig Dis Sci 40:14-20, 1995 21. Idilman R, Maria N, Colantoni A, et al: Interferon treatment for cirrhotic patients with chronic hepatitis C. J Viral Hepat 4:81-91, 1997 22. Kanazawa Y, Hayashi N, Mita E, et al: Influence of viral quasispecies on effectiveness of interferon therapy in chronic hepatitis C patients. Hepatology 20:1121-1130, 1994 23. Keeffe EB, Hollinger FB, Bailey R, et a1 Therapy of hepatitis C: Consensus interferon trials. Hepatology 26:101%107S, 1997 24. Koizumi K, Enomoto N, Kurosaki M, et a 1 Diversity of quasispecies in various disease stages of chronic hepatitis C virus infection and its significance in interferon treatment. Hepatology 2230-35, 1995 25. Lindsay L, Davis G, Schiff E, et al: Response to higher doses of interferon alpha-2b in patients with chronic hepatitis C: A randomized Multicenter Trial. Hepatology 24:1034-1040, 1996 26. Management of Hepatitis C. Hepatology 26(suppl 1):15-1565, 1997 27. Marcellin P, Levy S, Benhamou J, et al: Management of the asymptomatic HCV carrier with normal ALT levels. Viral Hepatitis Review 2:227-283, 1996 28. Marcellin P, Levy S, Eringer S: Therapy of hepatitis C: Patients with normal aminotransferase levels. Hepatology 26(suppl 1):133%136S, 1997 29. Martin P, Di Bisceglie AM, Kassiandes C, et al: Rapidly progressive non-A non-B hepatitis in patients with HIV infection. Gastroenterology 971559-1561, 1989
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30. Martinot-Peignoux M, Marcellin P, Pouteau M, et al: Pre-treatment serum hepatitis C virus RNA and genotype are the main and independent prognostic factors of SR to interferon a-therapy in chronic hepatitis C. Hepatology 221050-1056, 1995 31. Mcdonald JA, Caruso L, Karayannis P, et al: Diminished responsiveness of male homosexual chronic hepatitis B virus carriers with HTLV-111 antibodies to recombinant alpha-interferon. Hepatology 7719-723, 1987 32. McHutchinson J, Sedghi-Vaziri A, et a1 Is there an optimal time to measure quantitative HCV RNA to predict outcome following IFN treatment for chronic HCV infection? [abstract 3561. Hepatology AASLD abstracts:920, 1996 33. McHutchinson JD, Gordon SC,Schiff E, et al: Interferon alfa-2b alone or in combination with ribavirin as initial treatment for chronic hepatitis C. N Engl J Med 339:14851491, 1998 34. Mizokami M, Lau JY, Suzuki K, et a1 T. Differential sensitivity of hepatitis C virus quasispecies to interferon-alpha therapy. J Hepatol 21:884-886, 1994 35. Nakazawa T, Kato N, Ohkoshi S, et a1 Characterization of the 5' noncoding and structural region of the hepatitis C virus genome from patients with non-A, nonB hepatitis responding differently to interferon treatment. J Hepatol20623429, 1994 36. Negro F, Balsi M, Mondardini A, et a1 Continuous versus intermittent therapy for chronic hepatitis C with recombinant interferon 2a. Gastroenterology 107479485,1994 37. Okada S, Akahane Y, Suzuki H, et a1 The degree of variability in the amino terminal region of the E2/NSl protein of hepatitis C virus correlates with responsiveness to interferon therapy in viremic patients. Hepatology 16619624,1992 38. Olynyk JK, Reddy KR, Di Bisceglie AM, et al: Hepatic iron concentration as a predictor of response to interferon alpha therapy in chronic hepatitis C. Gastroenterology 1081104-1109, 1995 39. Orito E, Mizokami M, Suzuki K, et al: Loss of serum HCV RNA at week 4 of interferon alpha therapy is associated with more favourable long term response in patients with chronic hepatitis C. J Med Virol46:109-115, 1995 40. Pawlotsky JM, Pellerin M, Bouvier M, et al: Genetic complexity of the hypervariable region 1 (HVR1) of hepatitis C virus (HCV): Influence on the characteristics of the infection and responses to interferon alfa therapy in patients with chronic hepatitis C. J Med Virol54256-264,1998 41. Poynard T, Leroy V, Cohard M, et al: Meta-analysis of interferon randomized trials in the treatment of hepatitis C: Effects of dose and duration. Hepatology 24778-787,1996 42. Poynard T, Marcellin P, Lee S, et al: Randomised trial of interferon 2b plus ribavirin for 48 weeks or for 24 weeks versus interferon 2b plus placebo for 48 weeks for treatment of chronic infection with hepatitis C virus. Lancet 352:1426-1432, 1998 42a. Reddy R, Hoofnagle JH, Tong MJ, et al: Low rates of response to interferon in African Americans with chronic hepatitis C. Hepatology 28:497, 1998 43. Riggio 0, Montagnese F, Fiore P, et a1 Iron overload in patients with chronic viral hepatitis: How common is it? Am J Gastroenterol92:1298-1301, 1997 44. Ryff J-C: Usefulness of interferon for treatment of hepatitis C. J Hepatol 22(suppl 1):101-109, 1995 45. Shakil A, Conry-Cantelina C, Alter H, et al: Volunteer blood donors with antibodies to hepatitis C virus. Ann Intern Med 22413-417,1995 46. Shindo M, Arai K, Sokawa Y, et al: The virological and histological states of antihepatitis C positive subjects with normal liver biochemical values. Hepatology 22:41% 425, 1995 47. Simmonds P, Mellor J, Craxi A, et al: Epidemiological, clinical and therapeutic associations of hepatitis C types in western European patients. J Hepatol24517-524,1996 48. Soriano V, Garcia-Samaniego J, Bravo R, et a1 Efficacy and safety of a-interferon treatment for chronic hepatitis C in HIV-infected patients. J Infect 31:9-13, 1995 49. Toyoda H, Kumada T, Nakano S, et al: Quasispecies nature of hepatitis C virus and response to alpha interferon: Significance as a predictor of direct response to interferon. J Hepatol266-13,1997 50. Van Thiel DH, Friedlander L, Fagiuola S, et al: Response to interferon a therapy is influenced by the iron content of the liver. J Hepatol20410-415, 1994
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51 Zeuzem S, Lee JH, Roth W K Mutations in the nonstructural 5A gene of European hepatitis C virus isolates and response to interferon alfa [see comments]. Hepatology 25:740-744, 1997
Address reprint requests to Eleanor Barnes, BSc, MRCP 10th Floor Royal Free Hospital Pond Street London "3 United Kingdom
1089-3261/99 $8.00
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PREDICTORS OF A FAVORABLE RESPONSE TO ALPHA INTERFERON THERAPY FOR HEPATITIS C Eleanor Barnes, BSc, MRCP George Webster, BSc, MRCP, Simon Whalley, BMedSci, MRCP, and Geoffrey Dusheiko FCP(SA), FRCP, FRCP(Edin)
PREDICTIVE FACTORS FOR SUCCESSFUL INTERFERON THERAPY
Alpha interferon (IFN-a) alone and, more recently, IFN-a in combination with ribavirin are the only treatments that to date have been shown to be effective for the treatment of chronic hepatitis C virus (HCV) infection.*,7, 33 Large placebo-controlled trials have shown that only 15% to 20% of patients receiving IFN-a alone and 40% of patients receiving combination therapy can be expected to achieve a sustained virological response.2, Given these modest response rates, the side effects of treatment with IFN-a and the difficulties in administering IFNa by injection, it is important to consider selecting, if possible, those patients who are likely to respond to treatment. During the last decade, more than 35 controlled trials have published the results obtained with IFN-a, and many of these trials have identified predictive factors. The most important appear to be pretreat-
From the Department of Medicine, Division of Hepatology, Royal Free and University College School of Medicine, London, United Kingdom
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ment serum HCV RNA concentrations, pretreatment histology, and HCV genotype. Other factors that have been identified are 1. Drug regimen Dose greater than 3 million units (MU) three times a week Prolonged duration of treatment 2. An early response to IFN measured by alanine aminotransferase (ALT) and HCV RNA 3. Virus determinants Low level of circulating virus Genotype 2 or 3 Low number of quasispecies Multiple mutations in the interferon sensitivity determining region (NS5A) 4. Biochemical and histologic factors Elevated ALT level Absence of fibrosis and cirrhosis Low levels of hepatic iron 5. Negative HIV status 6. Demographic factors Age less than 40 years Female gender History of injection drug use Unknown source of infection Race 7. Short duration of infection
It is important at the outset to recognize the limitations of these predictive factors. Most data have been derived from the earlier trials of 6 months treatment with IFN-a monotherapy, and care must be taken in extrapolating these data to patients receiving combination therapy treatment or longer courses of IFN-a. Also, the earlier studies were conducted before HCV RNA testing was available and, therefore, looked only at the biochemical response. Hepatitis C virus RNA measurements have not been standardized, and concentrations may fluctuate spontaneously. The assay used to measure HCV RNA has become increasingly sensitive. Finally, definitions of treatment endpoints have been inconsistent. Despite these limitations, predictive factors have several clinical applications. Determining Treatment Algorithms
Although individual pretreatment predictive factors have a limited application, combinations of these factors may be useful. Davis et a1 applied an algorithm retrospectively to a large database of patients with chronic hepatitis C who had received standard doses of IFN-a6; this algorithm excluded patients with cirrhosis, genotype 1, or a high level of viremia from treatment. Although excluding these patients would
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have increased the response rate among those treated significantly and would have cut overall costs considerably, this strategy would, in theory, have denied treatment to 60% of the patients who in fact achieved a sustained response. The disappointing results of algorithms to date should not deter future attempts to identify an algorithm that can be usefully applied and thereby prevent patients from undergoing inconvenient and futile treatments. Doing so will be particularly challenging with constantly evolving treatment regimens.
Counseling Although predictive factors are not presently accurate enough to exclude patients from treatment, they do allow the clinician to give patients some idea of the likelihood of response to treatment based on the results of large controlled trials and thus to make a more informed decision regarding treatment.
Future Studies Predictive factors aid in study design, allowing randomization to be balanced for recognized predictive factors. Predictive factors also help investigators identify groups of patients who may benefit from alternative treatment regimens and so to plan future studies. For example, patients with genotype 1 or patients whose ALT levels remain elevated after 12 weeks of therapy may require higher drug doses or alternative treatment strategies.
Definitions
In this article the following definitions are used: End-of-treatment response (ETR) was previously known as complete response and is defined as normalization of ALT (end-oftreatment biochemical response) or loss of HCV RNA (end-oftreatment virological response) detected by polymerase chain reaction (PCR) at the end of treatment. Sustained response (SR) is defined as the normalization of ALT (sustained biochemical response), or loss of HCV RNA (sustained virologic response) detected by PCR 6 months after the end of treatment. No response (NR) is defined as the failure to normalize ALT or to lose HCV RNA detected by PCR by the end of treatment.
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THE RESPONSE TO INTERFERON AND THE DURATION AND DOSE OF TREATMENT
During the last decade, clinical trials have attempted to establish the optimum dose and duration of IFN-a monotherapy required for a sustained virologic response. It is probable, however, given the recently published reports of improved response rates, that many patients will now be offered IFN-a in combination with ribavirin as initial therapy? 42 The optimum dosage and duration of IFN therapy may be different for IFN monotherapy than for IFN given in combination with ribavirin. Better results seen with longer courses and higher doses of IFN need to be weighed against the disadvantages of the added inconvenience and cost of prolonged treatment and the inevitable increase in side effects seen with higher doses. Direct interstudy comparisons are difficult, and the results must approached cautiousIy because of the differences in study populations, particularly in terms of genotype, pretreatment RNA levels, degree of pretreatment fibrosis, and the differing types of IFN used.
Monotherapy
Large, placebo-controlled trials for hepatitis C using IFN-a monotherapy were first published in 1989.2, These trials clearly demonstrated that 50% of patients who achieved a biochemical ETR relapsed within 6 months of stopping treatment. These trials also established that IFN given at a dose of 3 million units (MU) three times a week for 6 months resulted in a SR of 23% and that lower doses (2 MU or 1 MU three times a week) given for 6 months resulted in lower SR (loo/, and 15%, respectively).Recently published response rates after 6 months treatment have been even lower than this; in the IFN-a monotherapy arm (231 patients, 72% genotype 1) of the recently published combination trials with ribavirin and IFN, the SR rate in patients treated for 6 months was only 69'0.~~ The therapeutic benefit of higher doses of IFN-a have been studied. Lindsay et a1 showed no increase in response rates at 12 weeks with doses of IFN higher than three times a week (eg., 5 MU or 10 MU three times a week). Although there was a marginal increase in the SR rate after 6 months of treatment at these higher doses, the side effects were difficult for patients to tolerate.25 Several meta-analyses of the numerous clinical trials published during the last decade have attempted to derive the optimum dose and duration of treatment needed to achieve a SR.6,41 Poynard analyzed 17 trials comparing different IFN regimens and 16 trials comparing IFN with There was a significant dose effect (6 MU versus 3 MU three times a week) at 12 months, but not at 6 months of treatment, with an increase in the SR of 17%.There was also a duration effect (12 months
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versus 6 months) at both the 3 MU (increase in SR of 16%) and the 6 MU dosages (increase in SR of 20%). This analysis concluded that the best efficacy/risk ratio favored the regimen of 3 MU three times a week for 12 months. The National Institutes of Health Consensus Development Conference provided an analysis of the responses to different types of IFN-Ix.*~ A meta-analysis of all 32 available randomized clinical trials of interferon alpha-2b (IFN-aw2b) published between 1986 and 1997 using doses of at least 2 MU three times a week for 24 weeks concluded that extended therapy for 12 to 24 months resulted in a significant improvement in SR compared with 6 months (27% versus 14%) and that doses above 3 MU three times a week resulted in a modest improvement of SR (28% versus 190/,).An analysis of interferon alpha-2a (IFN-a2a) trials suggested that the combination of longer periods of treatment and induction using higher initial doses significantly improved the SR. The optimum regimen of interferon alpha-nl (IFN-anl) has also been shown to be 3 MU three times a week for 12 months and produces SR equivalent to the best found with other alpha interferons. Both pulsed dosing (a 3-month course of IFN, followed by 6 months of no treatment and then by another 3-month course of IFN) and escalation in therapy when responses at standard doses are not obtained have 44 been shown to be ineffective treatment strategies.36, Direct study comparisons of IFN monotherapies are difficult, but the regimen that has been adopted by most clinicians is to begin a trial of treatment with IFN-a at a dose of 3 MU three times a week and, if a biochemical or virological response is observed after 12 weeks of therapy, to continue treatment for at least 12 months in total. There is a trend for patients with genotype 1 with or hepatic fibrosis to respond better to higher doses. The same treatment regimen may not be optimal for all patients, and future therapy may be individually tailored, based on such factors as genotype and degree of fibrosis. Interferon alphacon-1 (consensus interferon, IFN-a con-1) at a dose of 9 k g may induce a greater reduction in HCV RNA titres during treatment than IFN-a2b and slightly higher, albeit still unsatisfactory, sustained virologic response rates have been observed with IFN-a con-1 in patients with higher HCV RNA concentrations and genotype l.23Pegylated alpha interferons are under investigation. Preliminary data suggest that relatively high initial virological response rates are obtained, pointing to an enhanced antiviral effect of the sustained-delivery of alpha interferons. Combination Therapy
Ribavirin is a synthetic nucleoside analogue with in vitro action against RNA and DNA viruses. When given alone to patients with chronic hepatitis C, it decreases serum ALT concentration but has little antiviral effect.", l2 In 1998, the first major trials using IFN-a in combination with
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ribavirin were published.s,33, 42 These trials have demonstrated a considerable improvement of the virologic SR rate using combination therapy, both in IFN-naive patients and in patients who have previously experienced relapse on IFN monotherapy. The mechanism of action of ribavirin in combination with IFN remains unknown. McHutchinson et a1 randomly assigned 912 patients to IFN-a2b monotherapy at a dose of 3 MU three times a week or the same dose of IFN combined with ribavirin at a dose of 1 to 1.2 g daily, depending on patient weight, for 24 or 48 weeks.33The virologic SR rate was 31% for combination therapy given for 24 weeks, 38% for combination therapy given for 48 weeks, 6% with IFN-a2b alone given for 24 weeks, and 13% with IFN-a2b alone given for 48 weeks. Histological improvement was more common in patients treated with combination therapy. Drug doses needed to be reduced or discontinued because of side effects more often in the group receiving combination therapy than in the group receiving IFN monotherapy. Impressively, it has also been shown that 49% patients who had previously experienced relapse on IFN-a monotherapy responded to 6 months of combination therapy at the above doses.8 These results are very encouraging and will no doubt stimulate further interest in trials of combination therapy for HCV infection. There is considerable interest in induction with high doses of IFNa and ribavirin. However, there are insufficient data to indicate whether the relatively high early response rates will translate into higher sustained response rates. PREDICTION OF A SUSTAINED RESPONSE BY AN EARLY RESPONSE TO TREATMENT Monotherapy It has been consistently shown that patients who achieve a virologic SR with IFN-a monotherapy will have normal ALT levels at 8 to 12 weeks and failure to achieve normal ALT levels within this period indicates that the patient will not respond to further IFN treatment.7 Unfortunately 50% of patients who achieve normal ALT levels within 8 to 12 weeks'will subsequently experience relapse and fail to achieve a SR.*f7 Early loss of HCV RNA has been reported to be a better marker of a virological SR than normalization of the serum ALT. Orito et a1 showed that 17 of 19 patients who achieved a SR after 6 months of treatment with IFN-a (10 MU daily for 2 weeks followed by 10 MU three times a week for 22 weeks) cleared HCV RNA, measured by PCR, at 4 weeks. In contrast, 9 of 19 patients who achieved a SR had normal ALT levels at 4 weeks.39A study of 36 patients treated with 6 months of IFN-a, 6 MU three times a week showed undetectable HCV RNA at 2 weeks in 8 of the 10 patients who achieved a SR but in only 1 of 26 patients who had no response to treatment.20It has been shown that the most effective
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time to measure HCV RNA to predict a SR is 12 weeks into treatment, when loss of HCV RNA accurately predicts biochemical and virological SR in 85% and 91% of patients, respectively, although earlier measurements predicted a SR almost as well.32 It may be that a virologic SR depends not so much on early loss of HCV RNA but rather on the length of time that IFN therapy is continued after HCV RNA becomes undetectable. In support of this hypothesis, prolonged courses of treatment are associated with a SR, but further studies are necessary to confirm this possibility. Combination Therapy
In patients receiving combination therapy, relatively late clearance of HCV RNA from serum is frequently associated with a virological SR, and stopping treatment at 12 weeks because of persistent viremia may not be appropriate. McHutchinson et a1 found that among 51 of 87 patients (59%)who were treated with combination therapy for 48 weeks and who eventually achieved a SR, HCV RNA remained detectable, by sensitive reverse transcription polymerase chain reaction (RT-PCR) until 12 to 24 weeks of therapy. Later viral clearance was also found in 35 of 70 patients (50%) treated with combination therapy for 24 weeks.33In contrast with these findings, Davis et a1 randomly assigned 345 patients, who had previously experienced relapse following IFN-a treatment, to combination treatment or IFN monotherapy and found that all patients who achieved a SR had undetectable HCV RNA levels at 12 weeks.8 PRETREATMENT LEVELS OF HEPATITIS C VIRUS RNA PREDICT RESPONSE TO ALPHA INTERFERON
Lower pretreatment levels of HCV RNA have been shown to predict a sustained response to both IFN-LY monotherapy and to IFN-a in combination with ribavirin. A meta-analysis of 652 patients in 11 placebocontrolled trials showed that pretreatment HCV RNA levels of less than 1 X lo6 genomes/mL resulted in a virological SR in 50.5% of patients treated with IFN-LY compared with only 17.3% of patients whose pretreatment levels were higher than 1 X lo6 genomes/mL. However, the ETR and SR were not significantly different if the analysis was confined to studies using only a single assay technique, or if the HCV RNA level as measured by branched DNA was adjusted for genotype. The positive predictive value of a low HCV RNA level for a virologic SR was only 71%. In the study by McHutchinson et a1 of ribivarin and I F N - L Y combi~~ nation therapy 912 patients were stratified by their pretreatment RNA In all treatment groups, patients with a high pretreatment viral load (> 2 x lo6 copies/mL) had a lower rate of virologic SR than patients with a viral load less than 2 X lo6 copies/mL. Among patients
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with a high viral load, however, the virologic SR was significantly higher in patients treated with combination ribavirin and IFN-a2b therapy than in patients who received IFN-a2b monotherapy. Similarly Davies et a1 randomly assigned 345 patients who had previously experienced relapse after IFN-a2b monotherapy to receive combination IFN-a2b and ribavirin therapy or IFN-a2b monotherapy.s Again, patients with baseline serum HCV RNA levels of less than 2 X lo6 copies/mL were associated with a higher rate of virologic SR in both treatment groups. Patients treated with combination therapy rather than IFN-a2b alone were more likely to have a SR, regardless of their pretreatment RNA level.
GENOTYPE AS A PREDICTIVE FACTOR FOR THE RESPONSE TO INTERFERON
In the United States, as many as 70% of patients with HCV have genotype 1 infection. Patients with genotype l a and l b have been consistently shown to have a poorer response to treatment with both IFN-a monotherapy and IFN-a in combination with ribavirin than patients with genotype 2 or 3.3Or42 In Western Europe, a higher biochemical SR rate has been observed in hepatitis C patients infected with genotype 2 or 3 rather than genotype lj7 In a meta-analysis of 15 studies that reported a SR after IFN-a monotherapy, SR was achieved in 18.1% of 536 patients infected with genotype 1, but 54.9% of the 288 patients infected with genotype 2 or 3 had a SR.6 The predictive value of genotypes other than type 1 for a SR to IFN-a therapy was low (55%), emphasizing the restricted value of genotype as a predictive factor for response to treatment. Interferon-naive patients infected with all HCV genotypes, including type 1, have been shown to achieve a SR more often with combination ribavirin and IFN-a therapy than with IFN monotherapy.32,33 Nonetheless, even with combination therapy, treatment-naive patients infected with HCV genotype 1 are less likely to achieve a SR than patients infected with HCV genotype 2 and 3. In treatment-naive patients infected with HCV genotype 1, treatment with combination therapy for 48 rather than 24 weeks significantly improves the SR (28% versus 16%), but for patients infected with HCV genotypes 2 and 3 treated with Combination therapy, extending treatment for 12 rather than 6 months does not significantly improve the SR. Thus, genotyping could shorten the duration of treatment for treatment-naive patients infected with HCV genotype 2 and 3 and result in a substantial cost savings. Similarly, it has been shown that patients infected with any HCV genotype who have previously experienced relapse on IFN-a alone have an improved SR rate if treated with 24 weeks of combination therapy rather than 24 weeks of IFN-a alone, but patients infected with HCV genotype 1 who have experienced relapse after treatment with IFN-a monotherapy are less likely to achieve a SR than patients with genotype 2 or 3 (30%
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versus 73%, respectively), when treated subsequently with combination therapy.s QUASISPECIES AND THE RESPONSE TO ALPHA INTERFERON THERAPY
The HCV population in an infected individual is composed of heterogeneous but related genomic variants called quasispecies. The genetic complexity is the total number of genetic variants within the quasispecies population. The analysis of the genetic complexity of quasispecies may reveal mechanisms of resistance to antiviral therapy. The determination of IFN-resistant quasispecies may make it possible to predict the efficacy of IFN therapy. A hypervariable region (HVR) has been reported in the NH2-terminal of the E2 envelope gene of the HCV genome, in which marked diversity is found among different HCV isolates. Several studies have found that increased genetic complexity of the HVR is associated with a poor response to IFN-a therapy.17, 23, 36 This region is so variable, however, that no specific sequence correlates with IFN effecti~eness.~~ Multivariate analysis indicates that low genetic complexity of HVRl is an independent parameter predictive of a SR to IFN-a.35740*49 THE INTERFERON SENSITIVITY-DETERMINING REGION
Preliminary studies indicated that various HCV quasispecies might have different sensitivities to IFN-a,34 and thus may contain genomic regions predictive of response to IFN-CY therapy. Studies in Japan first identified a region of the HCV genome where mutations correlated with sensitivity to IFN-a. This putative region, termed the interferon sensitivity-determining region (ISDR), was identified in the carboxy-terminal half of the nonstructural protein 5A (NS5A) gene between codon 2209 and 2248 of HCV-J, a strain of HCV-lb whose complete genomic sequence has been identified. In 84 patients with chronic HCV-lb, after 6 months of IFN-a therapy, a SR did not occur in any of 30 patients whose NS5A 2209-2248 sequence was identical to that of HCV-J (wild type). Five of 38 patients (13%)with one to three changes in NS5A 2209-2248 (intermediate type) had a SR, as did all 16 patients with 4 to 11 amino acid substitutions (mutant type), indicating that the mutant type was significantly associated with a SR to IFN-a.14Interestingly, in the Japanese studies, mutant type ISDR correlated closely with low levels of serum HCV RNA, suggesting that replication may be reduced by these mutations. In a European study of patients with chronic HCV-lb, it was observed that although some sequence variations were found in the NS5A region, no clear differences could be directly correlated with interferon
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~ensitivity.'~Sensitive strains, however, exhibited more amino acid changes than a consensus sequence from all strains. Most of the variations occurred in the carboxy-terminal region, and especially in the previously reported NS5A/V3 region. Moreover, conformational analysis of NS5A by secondary structure prediction allowed the most sensitive strains to be differentiated from resistant ones. It was concluded that regions other than the ISDR were involved in resistance to IFN-a, perhaps through an interaction between NS5A and an IFN-induced protein kinase. In contrast with the Japanese studies, several European studies have shown a low response rate to IFN-a therapy in patients infected with HCV genotype 1. Perhaps the explanation for this poor response to IFNa is the finding that few European patients have four or more amino acid substitutions in the NS5A 2209-2248 region.51 Although the ISDR is of potential biologic interest, analysis of this region can not be recommended for routine clinical practice. PRETREATMENT ALANINE AMINOTRANSFERASE LEVELS AND THE RESPONSE TO INTERFERON
It has been estimated that approximately 25% of patients with chronic HCV (defined as anti-HCV-positive and with HCV RNA detectable by PCR) have persistently normal ALT levels.28These patients are generally asymptomatic but show histologic evidence of chronic hepatitis on biopsyz7Several studies have assessed the virologic characteristics in these patients and have shown that viral load, genotype, and quasispecies complexity are similar to those of patients with elevated ALT 46 In these patients it would appear that the degree of c~ncentration.~~, hepatic inflammation, reflected in the ALT level, is determined at least in part by host immunological responses. The natural history of these patients is not well documented, and long-term prospective studies are required, but it would seem that the development of significant fibrosis in these patients is rare.27 Trials to determine the response to IFN-a have usually excluded patients with normal ALT levels. A few, very small, mostly uncontrolled trials have attempted to determine the response to IFN in these patients.28Overall, the virological SR rate appears to be similar to the results seen in the large trials of IFN-a in patients with high ALT levels. None of these trials has demonstrated histologic improvement with therapy, and, of concern, these patients may develop elevated ALT levels that can persist after treatment has been stopped. Therefore, although IFN-a therapy may induce a virologic response in a few of these patients, treatment may be detrimental to others. Until prospective, large, placebo-controlled trials have been performed using combination therapy and the natural history of disease is better understood, treatment with IFN-a cannot generally be recommended for patients with normal ALT levels.
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PRETREATMENT FIBROSIS OR CIRRHOSIS AND THE RESPONSE TO INTERFERON
Approximately 20% to 30% of patients with HCV infection develop cirrhosis after 20 to 30 years of infection and, although sustained viral clearance with IFN-a will not reverse the degree of fibrosis, it may be worthwhile in arresting disease progression.21Recent reports have also suggested that viral clearance in patients with cirrhosis may reduce the risk of developing hepatocellular carcinoma.15This finding is controversial and is discussed in detail subsequently. Compensated Cirrhosis
Idilman et a1 recently reviewed 26 published studies to assess the response to IFN-a in patients with compensated cirrhosis.21Of the 1315 patients studied, 434 (33%)had histologically documented cirrhosis, and 884 (67%) had chronic hepatitis without cirrhosis. Data on HCV RNA results were limited to 153 patients with cirrhosis and 297 patients without cirrhosis. A virological response occurred in 5% to 10°/~of the patients with cirrhosis, compared with 20% to 35% of patients without cirrhosis. Other studies of IFN-a in combination with ribavirin have included patients with compensated cirrhosis and have shown that these patients have an increased rate of SR when treated with combination therapy compared with IFN monotherapy.8, 42 Poynard et a1 found that patients with septa1fibrosis or cirrhosis showed a decreased response to combination treatment given for either 24 or 48 weeks compared with patients without fibrosis or with portal fibrosis only." Other studies, however, have not identified the presence of fibrosis as a predictive factor for a response to combination treatment.8,33 337
Decompensated Cirrhosis
The efficacy of IFN-a in patients with decompensated cirrhosis is unclear, because these patients have been excluded from prospective, randomized trials. It is known, however, that these patients can experience severe side effects when treated with IFN-a, and thrombocytopenia or leukopenia may preclude therapy. At present, IFN treatment cannot be recommended for these patients, particularly for those who are candidates for transplantation. HEPATIC IRON AND THE RESPONSE TO INTERFERON
Elevated hepatic iron concentration (HIC) is reported in 10% to 29% of patients with chronic HCV infection.36,43 The mechanisms by which
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iron may effect hepatotoxicity in patients with HCV infection are uncertain and controversial, but possibilities include increased lipid peroxidation and oxidative stress, enhanced rates of viral replication, or effects on host imrn~nity.~ The effect of liver iron content on response to IFN-a therapy in patients with chronic HCV infection and the merits of iron depletion are presently under investigation. Liver iron content has been shown to influence the response to IFNa in patients with chronic hepatitis C. In a study of 79 patients with chronic hepatitis, 54 of whom had hepatitis C, the HIC was twice as high in the patients who did not respond to 6 months of IFN-a therapy (43%) compared with patients who had a biochemical ETR or a partial biochemical response (defined as a decrease in ALT of more than 50%) (57Y0).~' In an extension of this work, Olynk et a1 studied 58 patients with chronic hepatitis C, of whom 24 (41%) responded to IFN-a treatment.3s Although HIC was generally in the normal range, and no correlation between iron content and histological stage was seen, mean HIC was significantly higher in patients who did not respond to treatment. Nonresponse to IFN-a was seen in 88% of patients with HIC greater than 1100 pg/g dry weight of liver. The response to IFN-a in patients with HCV and thalassemia major, who usually have significant iron overload caused by multiple transfusions, has also been shown to be inversely related to liver iron content.41 On histological examination, the absence of stainable iron is associated with SR to IFN-a, and the pattern of staining, if present, appears to be important. Deposition of iron in portal endothelial cells has been shown to be a strong predictor of a poor response to treatment.' If high HIC is associated with poor response to IFN-a treatment in patients with chronic HCV infection does iron depletion improve this response? A number of small studies have sought to answer this question. It appears that venesection alone reduces the serum ALT level, but does not affect the HCV RNA level.'O, In a study of the effect of venesection on subsequent response to antiviral therapy, Fong et a1 randomly assigned 38 patients with chronic HCV infection to a course of venesection or to no iron depletion.16All patients then received IFNa therapy for 6 months. Significant reductions in ALT levels were seen after venesection. No significant differences in HCV RNA ETR were seen in the small number of patients studied, but there was a trend towards an improved SR in the venesected group after 6 months of follow-up ( P = 0.07). Five-year follow-up of patients who were maintained as iron deficient after unsuccessful IFN-a therapy has suggested sustained biochemical improvement, slower histologic progression, and possibly a lower frequency of HCC than in the nonvenesected group.19 Evidence that venesection may reduce the frequency of HCC in patients with chronic HCV is preliminary, although iron deposition has been shown to be more frequent in HCV-positive cirrhotic patients with HCC than in cirrhotic patients without HCC.4 Certain conclusions about iron and treatment response in chronic HCV may be drawn. Increased serum and liver markers of iron are
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common in patients with HCV infection, and iron may have an additive role in the hepatotoxicity of HCV. The pathological mechanisms underlying the effects of liver iron in patients with HCV infection are incompletely understood. Liver iron content is inversely associated with response to IFN-a therapy, and this inverse association appears to be independent of histological stage or grade of disease. Finally, iron reduction therapy consistently reduces serum ALT levels in patients with HCV infection, with or without the addition of IFN-a. Clear evidence that venesection improves virological SR is lacking, and thus venesection cannot be recommended at present.
HUMAN IMMUNODEFICIENCY VIRUS INFECTION AND RESPONSE TO INTERFERON
Early studies showed that IFN-a was ineffective in treating patients chronically infected with hepatitis B virus (HBV) who were also infected with HIV.31Discouraged by these early results, trials to determine the response of patients infected with HCV to IFN-a therapy have generally excluded patients with HIV disease; therefore, data on patients with HIV infection are generally limited to small uncontrolled studies. Concurrent infection with HCV and HIV is not uncommon, especially in populations where intravenous drug abuse is the usual mode of transmission of HIV disease. Chronic hepatitis C is reported to cause more severe liver disease and to progress more rapidly to cirrhosis in patients coinfected with HIV.29The life expectancy of patients with HIV disease has dramatically increased recently because of more effective combination therapies against HIV, so that coexistent diseases in HIV patients have become of more concern. The need for effective treatment of HCV in these patients is likely to increase. The lack of efficacy of IFN-a against HBV in patients coinfected with HIV was thought to be related to the absence of an immunomodulatory response.31In patients with chronic hepatitis C, the effect of interferon seems to be at least partly related to a direct antiviral mechanism, so that a beneficial effect in HIV- and HCV-positive patients might be expected. A controlled study by Soriano et a1 assessed the efficacy of IFN-a in 57 patients with HCV infection who were coinfected with HIV but who had CD4 counts above 200/mm3.48The SR rate in these HIVinfected patients was not significantly different from that of the control group of patients without HIV infection (38% versus 47%). A lack of response to IFN-a in the HIV-positive patients was associated with CD4 counts below 500 mm3. Alpha interferon was generally well tolerated in the HIV-positive patients, although during the first 14 weeks of treatment with IFN-a 3 patients experienced a very rapid decline in the CD4 counts that only partially recovered when treatment was stopped.
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Although there may well be a place for IFN-a treatment in patients coinfected with HCV and HIV, more information is required to establish the SR rates for both IFN-a monotherapy and combination therapy, the effects of IFN-a on CD4 cells, and the possible interactive toxicities of IFN-a and ribavirin with antiretroviral therapy. DEMOGRAPHIC FEATURES
Age younger than 40 years, female gender, short duration of infection, and route of infection have been inconsistently identified as factors which predict the response to IFN. In a recent report, Reddy et a1 suggested that response rates may be lower in blacks than in whites or Asians with genotype 1 infection^.^^" SUMMARY
The most consistently identified predictive factors for a response to both IFN-a monotherapy and IFN-a in combination with ribavirin are a low HCV RNA level, the absence of fibrosis, infection with HCV genotype 2 and 3, and a prolonged duration of treatment. In addition, an early response to IFN-a predicts response to IFN-a monotherapy but not necessarily to combination therapy. There does not appear to be any major gain in treating IFN-naive patients with HCV genotype 2 or 3 infection with a combination of IFN-a and ribavirin for longer than 6 months. The identification of these predictive factors has allowed improvement in study design and assessment and may provide a patient with an idea of the likelihood of response, making possible a more informed decision regarding treatment. At present, none of these factors, either alone or in combination, completely predicts response to IFN-a. Thus, individual patients should not be denied treatment on the basis of these factors.
References 1. Barton AL, Banner BF, Cable EE, et al: Distribution of iron in the liver predicts the response of chronic hepatitis C infection to interferon therapy. A m J Clin Pathol 103419-424, 1995 2. DiBisceglie A, Martin P, Kassianides C, et al: Recombinant interferon alpha therapy for chronic hepatitis C. N Engl J Med 321:1506-1510, 1989 3. Bonkovsky HL, Banner BF, Rothman AL: Iron and chronic viral hepatitis. Hepatology 25:759-768, 1997 4. Chapoutot C, Laurent C, Ramos J, et a1 Significant correlation between liver iron deposition and hepatocellular carcinoma in patients with viral C cirrhosis: Study of 104 patients. Hepatology 28248, 1998 5. Clemente MG, Congia M, Lai ME, et al: Effect of iron overload on the response to
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recombinant interferon-alpha treatment in transfusion-dependent patients with thalassaemia major and chronic hepatitis C. J Pediatr 125:123-128, 1994 6. Davis G, Lau J: Factors predictive of a beneficial response to therapy of hepatitis C. Hepatology 26(suppl 1):112S127S, 1997 7. Davis GL, Balart LA, Schiff ER, et al: Treatment of chronic hepatitis C with recombinant Interferon Alfa. N Engl J Med 321:1501-1506, 1989 8. Davis G, Esteban-Mur R, Mustgi V, et al: Interferon alfa-2b alone or in combination with ribavirin for the treatment of relapse of chronic hepatitis C. N Engl J Med 339~1493-1499,1998 9. Di Bisceglie AM, Axiotis CA, Hoofnagle JH, et a1 Measurements of iron status in patients with chronic hepatitis. Gastroenterology 102:2108-2113, 1992 10. Di Bisceglie AM, Bonkovsky H, Krawit E, et al: Iron reduction therapy in chronic hepatitis C. Hepatology 26:214A, 1997 11. Di Bisceglie AM, Conjeevaram HS, Fried MW, et al: Ribavirin as therapy for chronic hepatitis C: A randomised, double blind placebo controlled trial. Ann Intern Med 123:897-903, 1995 12. Dusheiko G, Main J, et a1 Ribavirin treatment for patients with chronic hepatitis C: Results of a placebo controlled study. J Hepatol 25:591-598, 1996 13. Duverlie G, Khorsi H, Castelain S, et a1 Sequence analysis of the NS5A protein of European hepatitis C virus l b isolates and relation to interferon sensitivity. J Gen Virol 7911373-1381, 1998 14. Enemoto N, Sakuma I, Asakina Y, et a 1 Comparison of full length sequences of interferon sensitive and resistant hepatitis C virus lb. J Clin Invest 96224-230, 1995 15. Fattovivich G, Giustina G, Degos F, et a1 Effectiveness of interferon-alpha on incidence of hepatocellular carcinoma and decompensation in European patients with cirrhosis type C. J Hepatol 27201-205, 1997 16. Fong T-L, Han SH, Tsai N C-S, et a 1 A pilot randomized, controlled trial of the effect of iron depletion on long-term response to a-interferon in patients with chronic hepatitis C. J Hepatol 28:369-374, 1998 17. Gonzalez-Peralta RP,Liu WZ, Davis GL, et a1 Modulation of hepatitis C virus quasispecies heterogeneity by interferon-alpha and ribavirin therapy. J Viral Hepat 4:99106, 1997 18. Hayashi H, Takikawa T, Nishimura N, et a1 Improvements of serum aminotransferase levels after phlebotomy in patients with chronic hepatitis C and excess hepatic iron. Gastroenterology 89:986-988, 1994 19. Hayashi H, Wakusawa S, Takikawa T, et al: Long term effect of iron removal on chronic hepatitis C. Hepatology 26:215A, 1997 20. Hino K, Okuda M, Korishi T, et al: Serial assay of hepatitis C virus RNA in serum for predicting response to IFN alpha therapy. Dig Dis Sci 40:14-20, 1995 21. Idilman R, Maria N, Colantoni A, et al: Interferon treatment for cirrhotic patients with chronic hepatitis C. J Viral Hepat 4:81-91, 1997 22. Kanazawa Y, Hayashi N, Mita E, et al: Influence of viral quasispecies on effectiveness of interferon therapy in chronic hepatitis C patients. Hepatology 20:1121-1130, 1994 23. Keeffe EB, Hollinger FB, Bailey R, et a1 Therapy of hepatitis C: Consensus interferon trials. Hepatology 26:101%107S, 1997 24. Koizumi K, Enomoto N, Kurosaki M, et a 1 Diversity of quasispecies in various disease stages of chronic hepatitis C virus infection and its significance in interferon treatment. Hepatology 2230-35, 1995 25. Lindsay L, Davis G, Schiff E, et al: Response to higher doses of interferon alpha-2b in patients with chronic hepatitis C: A randomized Multicenter Trial. Hepatology 24:1034-1040, 1996 26. Management of Hepatitis C. Hepatology 26(suppl 1):15-1565, 1997 27. Marcellin P, Levy S, Benhamou J, et al: Management of the asymptomatic HCV carrier with normal ALT levels. Viral Hepatitis Review 2:227-283, 1996 28. Marcellin P, Levy S, Eringer S: Therapy of hepatitis C: Patients with normal aminotransferase levels. Hepatology 26(suppl 1):133%136S, 1997 29. Martin P, Di Bisceglie AM, Kassiandes C, et al: Rapidly progressive non-A non-B hepatitis in patients with HIV infection. Gastroenterology 971559-1561, 1989
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30. Martinot-Peignoux M, Marcellin P, Pouteau M, et al: Pre-treatment serum hepatitis C virus RNA and genotype are the main and independent prognostic factors of SR to interferon a-therapy in chronic hepatitis C. Hepatology 221050-1056, 1995 31. Mcdonald JA, Caruso L, Karayannis P, et al: Diminished responsiveness of male homosexual chronic hepatitis B virus carriers with HTLV-111 antibodies to recombinant alpha-interferon. Hepatology 7719-723, 1987 32. McHutchinson J, Sedghi-Vaziri A, et a1 Is there an optimal time to measure quantitative HCV RNA to predict outcome following IFN treatment for chronic HCV infection? [abstract 3561. Hepatology AASLD abstracts:920, 1996 33. McHutchinson JD, Gordon SC,Schiff E, et al: Interferon alfa-2b alone or in combination with ribavirin as initial treatment for chronic hepatitis C. N Engl J Med 339:14851491, 1998 34. Mizokami M, Lau JY, Suzuki K, et a1 T. Differential sensitivity of hepatitis C virus quasispecies to interferon-alpha therapy. J Hepatol 21:884-886, 1994 35. Nakazawa T, Kato N, Ohkoshi S, et a1 Characterization of the 5' noncoding and structural region of the hepatitis C virus genome from patients with non-A, nonB hepatitis responding differently to interferon treatment. J Hepatol20623429, 1994 36. Negro F, Balsi M, Mondardini A, et a1 Continuous versus intermittent therapy for chronic hepatitis C with recombinant interferon 2a. Gastroenterology 107479485,1994 37. Okada S, Akahane Y, Suzuki H, et a1 The degree of variability in the amino terminal region of the E2/NSl protein of hepatitis C virus correlates with responsiveness to interferon therapy in viremic patients. Hepatology 16619624,1992 38. Olynyk JK, Reddy KR, Di Bisceglie AM, et al: Hepatic iron concentration as a predictor of response to interferon alpha therapy in chronic hepatitis C. Gastroenterology 1081104-1109, 1995 39. Orito E, Mizokami M, Suzuki K, et al: Loss of serum HCV RNA at week 4 of interferon alpha therapy is associated with more favourable long term response in patients with chronic hepatitis C. J Med Virol46:109-115, 1995 40. Pawlotsky JM, Pellerin M, Bouvier M, et al: Genetic complexity of the hypervariable region 1 (HVR1) of hepatitis C virus (HCV): Influence on the characteristics of the infection and responses to interferon alfa therapy in patients with chronic hepatitis C. J Med Virol54256-264,1998 41. Poynard T, Leroy V, Cohard M, et al: Meta-analysis of interferon randomized trials in the treatment of hepatitis C: Effects of dose and duration. Hepatology 24778-787,1996 42. Poynard T, Marcellin P, Lee S, et al: Randomised trial of interferon 2b plus ribavirin for 48 weeks or for 24 weeks versus interferon 2b plus placebo for 48 weeks for treatment of chronic infection with hepatitis C virus. Lancet 352:1426-1432, 1998 42a. Reddy R, Hoofnagle JH, Tong MJ, et al: Low rates of response to interferon in African Americans with chronic hepatitis C. Hepatology 28:497, 1998 43. Riggio 0, Montagnese F, Fiore P, et a1 Iron overload in patients with chronic viral hepatitis: How common is it? Am J Gastroenterol92:1298-1301, 1997 44. Ryff J-C: Usefulness of interferon for treatment of hepatitis C. J Hepatol 22(suppl 1):101-109, 1995 45. Shakil A, Conry-Cantelina C, Alter H, et al: Volunteer blood donors with antibodies to hepatitis C virus. Ann Intern Med 22413-417,1995 46. Shindo M, Arai K, Sokawa Y, et al: The virological and histological states of antihepatitis C positive subjects with normal liver biochemical values. Hepatology 22:41% 425, 1995 47. Simmonds P, Mellor J, Craxi A, et al: Epidemiological, clinical and therapeutic associations of hepatitis C types in western European patients. J Hepatol24517-524,1996 48. Soriano V, Garcia-Samaniego J, Bravo R, et a1 Efficacy and safety of a-interferon treatment for chronic hepatitis C in HIV-infected patients. J Infect 31:9-13, 1995 49. Toyoda H, Kumada T, Nakano S, et al: Quasispecies nature of hepatitis C virus and response to alpha interferon: Significance as a predictor of direct response to interferon. J Hepatol266-13,1997 50. Van Thiel DH, Friedlander L, Fagiuola S, et al: Response to interferon a therapy is influenced by the iron content of the liver. J Hepatol20410-415, 1994
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51 Zeuzem S, Lee JH, Roth W K Mutations in the nonstructural 5A gene of European hepatitis C virus isolates and response to interferon alfa [see comments]. Hepatology 25:740-744, 1997
Address reprint requests to Eleanor Barnes, BSc, MRCP 10th Floor Royal Free Hospital Pond Street London "3 United Kingdom