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Hepatitis C Virus (HCV) and HIV/HCV Coinfection: A Critical Review of Research and Treatment
Volume I: Clinical Science

V. Hepatitis C Treatment

July 2004

Summary

The current standard of treatment for hepatitis C virus (HCV) is a combination of two drugs: pegylated interferon and ribavirin. The virological response rate, treatment duration, and ribavirin dose vary according to several prognostic factors: genotype, baseline HCV RNA (viral load), race, body weight, age, and liver histology. In one study, 48 weeks of pegylated interferon plus ribavirin led to treatment responses ranging from 47% to 82% (Hadziyannis 2004). Overall, approximately 50% of those treated for hepatitis C will achieve a sustained virological response (SVR), meaning that no virus is detected in the bloodstream six months after completing treatment. Whether or not an SVR is equivalent to a "cure" is a controversial matter. Treatment may be beneficial for individuals who do not achieve an SVR; some have an improvement in liver condition or a stabilization of disease progression, although the durability and clinical benefits of these improvements are unknown at present.

The decision to treat hepatitis C is a complex one. The current guidelines recommend treatment for individuals with the greatest risk of developing cirrhosis (NIH 2002). The rationale for treatment is less clear-cut for members of understudied populations. Pivotal treatment trials excluded children; the elderly; individuals with renal disease; individuals with mild or advanced liver disease; liver transplant recipients; hemophiliacs; individuals with psychiatric co-morbidities; and active drug and alcohol users. Therefore, few data exist about safety and efficacy of treatment in these populations. Studies have shown that treatment is less effective for African Americans, although the reasons for diminished efficacy are not clear. The potential benefits of treatment must be carefully weighed against the side effects, which range from uncomfortable to debilitating, and in rare instances are life-threatening. Interventions are available to minimize side effects, but more research is needed to improve the tolerability of HCV treatment. Questions about dosing and duration of therapy remain as well.

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Other key concerns related to HCV therapy include access to treatment and quality of care. Treating HCV is costly; a year of therapy (not including medications to ameliorate side effects) may cost up to $40,000. Treatment is rarely available to incarcerated persons, despite a shockingly high prevalence of hepatitis C among prisoners. Hepatitis C is also prevalent among people with significant co-morbidities, including drug and alcohol addiction and mental illness; these individuals require multidisciplinary care. Primary care providers often lack adequate information about the diagnosis, care, and treatment of hepatitis C. Finally, alternative and complementary therapies, although widely used, have not been adequately researched.

Although results from three large trials of pegylated interferon plus ribavirin are available, people weighing the potential benefits of HCV treatment against considerable side effects are still without a simple answer to the key question: "Will this work for me?" An algorithm that considers individual prognostic factors (genotype and baseline HCV viral load, liver histology, baseline liver enzyme levels, age, sex, and race) does shed some light on the likelihood of achieving a sustained virological response, yet people with hepatitis C, clinicians, researchers, and advocates continue to seek information on optimal treatment and side effect management strategies while awaiting better therapies.

For information about treatment of HCV in HIV-coinfected individuals, see Chapter VII, HCV Treatment in HIV/HCV Coinfection.

Who Needs Treatment?

If the natural history of hepatitis C infection followed an identical and predictable course in each infected individual, and HCV treatment were universally efficacious, had minimal side effects and were not exceedingly costly, the question of whom to treat would become moot. Active drug users, liver transplant recipients, people with decompensated cirrhosis, HIV and/or HBV coinfection, mental illness, and other significant co-morbidities have been excluded from these trials. HCV treatment may indeed be less effective and less tolerable for those who need it most. Despite improved treatment efficacy, the side effects remain problematic. For some individuals, they may be insurmountable. The cost of combination treatment -- up to $40,000 per year, not including other agents often used for side effects management -- creates an additional barrier to treatment for many who need it.

The National Institute of Health's 2002 Consensus Statement on the Management of Hepatitis C (NIH 2002) recommends that hepatitis C treatment be offered to:

Patients with an increased risk of developing cirrhosis. These patients are characterized by detectable HCV RNA levels higher than 50 IU/mL, a liver biopsy with portal or bridging fibrosis, and at least moderate inflammation and necrosis. The majority also have persistently elevated ALT values. In some patient populations, the risks and benefits of therapy are less clear and should be determined on an individual basis or in the context of clinical trials.

The decision to treat chronic hepatitis C is more complex for people with normal or only slightly elevated ALT values (less than two times the upper limit of normal) and symptomatic mild liver disease; individuals with advanced liver disease; those with kidney disease; the elderly; and children. More research is necessary to guide treatment decisions in these populations.

Hepatitis C Treatment: Pegylated Interferon and Ribavirin

The standard of care for treatment of HCV is a combination of two drugs: pegylated interferon alfa (taken as injections) and ribavirin (taken in pill or capsule form; a liquid form of ribavirin for pediatric use has been approved by FDA). The course of treatment may be 24 or 48 weeks, depending on the HCV genotype.

Pegylated Interferon

Interferons are cytokines (chemical messengers) that are naturally produced by white blood cells to help fight infections and inhibit abnormal tissue growth in the body. Interferon (IFN) has antiviral and immunomodulatory effects. Different types of recombinant interferon -- alfa, beta, and consensus -- have been used to treat hepatitis C. Interferon alfa-2a and interferon alfa-2b have been used to treat hepatitis C since 1989 (Davis 1989; Di Bisceglie 1989). The only difference between these two interferons is the amino acid at position 23, which is lysine in alfa-2a and arginine in alfa-2b. Pegylation -- the attachment of a nontoxic molecule called polyethylene glycol -- keeps interferon in the bloodstream longer and at more constant levels, thus increasing the efficacy of interferon treatment while reducing the frequency of injections (Perry 2002; Reddy 2001; Zeuzem 2000). Two forms of pegylated interferon have been approved by FDA for treatment of chronic HCV: pegylated interferon alfa-2a (Pegasys®), which uses a large (40kd) branched molecule of polyethylene glycol, and pegylated interferon alfa-2b (Peg-Intron®), which uses a smaller (12kd) linear molecule of polyethylene glycol. Attachment of the PEG molecule extends the half-life of Peg-Intron® to approximately 40 hours (compared to 3.6 hours for the parent molecule); the mean half-life of Pegasys® is 80 hours, with a range from 50 to 140 hours (compared to a mean of 5.1 hours for the parent molecule). Pegylated interferon alfa-2a is given at a fixed dose and is premixed; pegylated interferon alfa-2b is dosed according to weight and must be reconstituted with sterile water before administration (the manufacturer has developed a pre-filled dosing pen to simplify the process). The most commonly reported side effects of interferon are fatigue and flulike symptoms. Other side effects include hematologic toxicities and depression. Side effects may range from uncomfortable to debilitating; in rare instances, they may be life-threatening.

Ribavirin

Ribavirin (RBV) belongs to the family of nucleoside analogs (a class of drugs also used to treat HIV, although ribavirin has no effect against HIV). By itself, ribavirin is ineffective against hepatitis C, but when it is used in combination with interferon, the combination is more effective than interferon monotherapy (Di Bisceglie 1995; McHutchison 1998; Poynard 1998). It has been speculated that ribavirin may force hepatitis C virus into "error catastrophe" by increasing mutation of hepatitis C until it can no longer replicate (Cameron 2001; Crotty 2002; Graci 2002). Ribavirin is available under the name of Copegus® (Roche), Rebetol® (Schering), and from compounding pharmacies. It is also available as a generic. Ribavirin may be given at a fixed dose based on efficacy by genotype, or dosing may be weight-based. The most frequently reported side effect of ribavirin is hemolytic anemia, which is usually reversible.

The combination of pegylated interferon and ribavirin is the most effective hepatitis C treatment to date. Approximately half of those treated will achieve a sustained virological response (DiBisceglie 2002; Fried 2002a; Glue 2000; Manns 2001).

Assessing Responses to Hepatitis C Treatment: EVR, ETR, and SVR

Treatment for HCV can be evaluated by virological, histological, and biochemical responses, and at different time points: early, at the end of treatment, and six months after completion of treatment.

  • Virological response is defined as either undetectable or significantly decreased HCV RNA.

  • Histological response refers to an improvement in the condition of liver tissue, assessed by a better-than-baseline histological grade (amount of disease activity) in a post-treatment biopsy.

  • A biochemical response reflects liver enzyme (alanine aminotransferase (ALT) and aspartate aminotransferase (AST)) levels that have decreased to within the normal range at the end of treatment, or for at least six months after completion of treatment.

  • An early virological response (EVR) is defined as either a 2 log10 drop (a decrease in viral load by an order of 100; for example, decreasing from 2,000,000 to 20,000 copies) in HCV RNA, or undetectable HCV RNA twelve weeks after initiating treatment.

  • An end-of-treatment response (ETR) means that an individual has no detectable HCV RNA in the bloodstream upon completion of treatment; many studies report ETR. While providing useful data, ETR should not be confused with the more robust SVR, as some individuals relapse during the six-month period between ETR and SVR reports. The rate of ETR is always higher than the rate of SVR.

  • A sustained virological response (SVR) occurs when an individual has undetectable HCV RNA six months after completing HCV treatment. Many consider an SVR to be a cure or at least an indication of long-term remission, though this is controversial. One study found no detectable HCV RNA in the serum of five individuals who had achieved SVR ten years earlier (Lau 1998), while two studies reported relapse rates among 9% to 12% of sustained virological responders after five years of follow-up (Pradat 2003; Veldt 2003).

  • A non-responder is someone who does not have a significant reduction in HCV RNA levels (<2 log10) after a specified interval of treatment (usually 24 weeks), or who has a significant decrease in HCV RNA, but never becomes HCV-RNA- undetectable during treatment. Some non-responders may have improved liver histology after treatment (Shiffman 1997).

  • Not all individuals with an end-of-treatment response will maintain a sustained virological response; individuals with an ETR, but not an SVR are referred to as relapsers.

Long-Term Follow-Up of Sustained Virological Responders

Reports of the durability of sustained virological responses to HCV treatment vary. Early reports may have overestimated the proportion of sustained virological responders who remained virus-free years later. Older, less sensitive assays may have failed to detect low levels of viremia, thus some may have initially been misclassified as sustained virological responders. Others may have been reinfected. Very low levels of replication-competent hepatitis C have been discovered in blood from 11 individuals up to five years after they achieved SVR (Pham 2004). Corresponding liver biopsy samples were not available; the impact of low-level, replicating HCV on the liver histology of these sustained virological responders is unknown. Long-term follow-up of sustained virological responders treated with standard and pegylated interferon-based regimens is needed.

Table 1. Number and Percent of Sustained Virological Responders 3.5-10 Years Later
Table 1. Number and Percent of Sustained Virological Responders 3.5-10 Years Later

Care for Hepatitis C

When I went back for the [HCV test] results, ... she offered almost no information at all about the virus, explaining that she "just doesn't see it" in her surgery, and handed me a brochure produced in 1991, which said that there was little in the way of treatment, that the prognosis was not good. ... All of this was simply untrue in 2000, but I did not know that then.

-- Lisa Waller
Medical Journal of Australia

Provider Education

Not all primary care physicians are well educated about hepatitis C. Consequently, their patients receive suboptimal care and inaccurate information despite recent medical advances in hepatitis C diagnostics and treatment. In 1999, Shehab and colleagues released their landmark survey of practice patterns of primary care physicians in the management of hepatitis C. The survey included an assessment of general knowledge of hepatitis C and clinical vignettes. The surveys were completed and returned by 33% (404/1,233) of physicians in a large HMO in Michigan. Birth from a mother with hepatitis C was ranked as a significant risk factor for hepatitis C infection by 80%; 20% thought that a blood transfusion in the United States after 1994 presented a significant risk; and 8% thought that casual household contact with an HCV-infected person presented a significant risk for acquiring hepatitis C. Only 2% had read the Consensus Development Conference Statement. Most respondents agreed to liver biopsy and interferon treatment if recommended by a gastroenterologist, but 72% either overestimated the response rate to interferon therapy or did not know what the response rate was (Shehab 1999).

Shehab and colleagues published results from a national survey in 2001 that assessed provider knowledge of risk factors for hepatitis C, attitudes about HCV testing, and actual management of patients with HCV. Completed surveys were received from 39% (1,412/4,000) of primary care providers across the United States. Although more than 90% were aware of the most common risk factors for hepatitis C, only 59% asked all of their patients about their risk factors for hepatitis C. Only 70% tested patients who had disclosed being at risk for hepatitis C infection, and a quarter of survey respondents did not know which treatment to recommend for hepatitis C (Shehab 2001).

Another group of researchers assessed the care received by patients with hepatitis C from an integrated medical delivery system in Philadelphia in which approximately 855 physicians provide medical care at 108 sites to about 500,000 patients. Surveys were sent to 222 physicians; 172 responses were analyzed. In addition, the medical charts of 186 individuals with hepatitis C were reviewed. Although ALT testing was frequently ordered as a part of routine medical care, 34% of physicians reported that they did not order HCV antibody testing for patients with elevated ALT levels. HCV antibody testing was ordered by only 21% of physicians with patients who disclosed parenteral (injecting) risk factors. Seventy-nine percent did not routinely test these patients for HCV. Screening for HCV antibodies was more frequently offered by physicians with practices in affluent, mostly white suburban areas; this is concerning because HCV is prevalent among African Americans and individuals with low socioeconomic status (M. J. Alter 1992).

There were substantial gaps between physicians' survey responses and the information from medical charts of 186 hepatitis C patients. Although 79% (147/186) of the HCV patients had elevated ALT levels, only 55% (102/186) had been seen by a gastroenterologist. According to their survey responses, physicians indicated that they referred 75% of HCV patients to specialty care. Only three individuals (2%) had been vaccinated against hepatitis A; only six (3%) had been vaccinated against hepatitis B (Nicklin 1999).

Figure 1. Physician-Reported Biopsy Recommendation vs. Documentation of Biopsy on Chart
Figure 1. Physician-Reported Biopsy Recommendation vs. Documentation of Biopsy on Chart

In 2003, Shehab and colleagues published another survey of the diagnosis and management of hepatitis C among patients of primary care clinics. They reviewed medical records from three groups of 229 individuals. Members of group one were HCV-antibody-positive, members of group two were HCV-antibody-negative, and members of group three had never been tested. Hepatitis C testing was initiated by the physician for just 16% (37/229) of group one and for just 10% (22/229) of group two. In group three, only 1% (2/229) had documented evidence of having had a discussion about hepatitis C with their physician. Although a majority (77%) of group one patients with detectable HCV RNA and elevated liver enzymes were referred to specialty care, almost half (40%; 24/59) of those biposied were diagnosed with bridging fibrosis or cirrhosis (Shehab 2003). These data underscore the importance of timely provider-initiated discussion of, and screening for, hepatitis C.

Guidelines for the management of persons with hepatitis C are extremely valuable. They must, however, be accompanied by initiatives for provider education to ensure the identification of and optimal care for individuals with hepatitis C.

Prognostic Factors

Coinfection with HIV

See Chapter VII, HCV Treatment in HIV/HCV Coinfection.

Genotype

Genotype is the strongest predictor of response to treatment. Genotypes 1 and 4 do not respond to treatment as well as genotypes 2 and 3, regardless of the type of interferon used (Berg 2003; Fried 2002a; S. Lee 2002; McHutchison 1998; Poynard 1998). In their meta-analysis of data from three trials of pegylated interferon alfa-2a, Lee and colleagues found a non-1 genotype to be the strongest independent predictor of SVR (OR, 4.11; 95% CI, 2.90-5.86; P=0.0001) (S. Lee 2002). A 24-week course of treatment for individuals with genotypes 2 and 3 appears to be sufficient; a 48-week course of treatment is recommended for individuals with genotypes 1 and 4 (Di Bisceglie 2002; Hadziyannis 2004).

Genotype 3 does not appear to be as sensitive to treatment as genotype 2 (Mangia 2004: Zeuzem 2003). Zeuzem and colleagues treated 224 individuals with HCV-2 or HCV-3 with 1.5 µg/kg of pegylated interferon alfa-2b plus weight-based rivavirin (800 to 14,000 mg/day) for 24 weeks. Overall, 81% achieved sustained virological response, but SVR rates were lower in those with genotype 3 (79% [143/182]) than in genotype 2 (93% [39/42]). Relapse rates were higher in genotype 3 (14% vs. 7% in genotype 2). The difference in response rates may be attributed in part to steatosis and high baseline viral load. Steatosis was significantly more prevalent in genotype 3 (P=0.003), and it was associated with a high baseline viral load (P=0.001). Steatosis of <5% was significantly associated with SVR (P=0.015) (Zeuzem 2003).

Genotype 4 may be more responsive to treatment than genotype 1. Sustained virological response rates from two studies that used 48 weeks of pegylated interferon plus ribavirin have ranged from 40% to 61% (Esmat 2003; Hassan 2003).

The viral kinetics of hepatitis C during early treatment differ depending on the genotype of HCV (A. U. Neumann 2000; Pawlotsky 2002; Zeuzem 2001). Frequent blood sampling from 12 individuals with HCV genotypes 1a, 1b, 2a, and 2b over the first 14 days of high-dose interferon revealed significant differences. Individuals with genotypes 2a and 2b had larger and more rapid decreases in HCV RNA after 48 hours than those with genotypes 1a and 1b (2.95 log copies/mL vs. 1.65 log copies/mL; t1/2 = 2.0 ± 0.5 hours vs. t1/2 = 3.0 ± 1.0 hours). At the end of 14 days, a significantly larger proportion of individuals with genotypes 2a and 2b had undetectable HCV RNA (P=0.03) (A. U. Neumann 2000). An examination of first and second-phase viral kinetics by genotype and mode of treatment (standard or pegylated interferon monotherapy) revealed more rapid first-phase and second-phase viral decay slopes for non-1 genotypes treated with pegylated interferon (Zeuzem 2001). Pawlotsky and colleagues observed less marked decreases in second-phase viral decay in genotypes 1 and 4 vs. genotype 3. At four weeks of treatment, individuals with genotypes 1 and 4 were less likely to be classified as rapid responders (individuals with decreases ≥0.3 log per week) (Pawlotsky 2002).

Baseline HCV RNA

A low baseline HCV-RNA level (≤2 million copies or ≤800,000 International Units) is a significant predictor of response to treatment. Numerous trials of both standard and pegylated interferon have confirmed that those with low baseline HCV RNA levels have a greater likelihood of achieving SVR (Fried 2002a; Hadziyannis 2002; Manns 2001; Poynard 1998).

The Role of Race/Genetics

In the United States, HCV is most prevalent among African Americans (see Chapter I, Epidemiology of Hepatitis C), who are more likely to be infected with genotype 1 than Whites, Hispanics, or Asian Pacific Islanders (P<0.001) (Blatt 2000; Jacobson 2002; Wiley 2002). It has been observed in several studies that African-Americans have impaired responses to interferon (De Maria 2002; Jeffers 2002; Kinzie 2001; McHutchison 2000; Reddy 1999; Theodore 2003). Results from a study of 472 individuals treated with either consensus interferon or interferon alfa-2b thrice weekly for 24 weeks found markedly poorer responses among African Americans than among Whites, Hispanics, and Asian Americans both during and after therapy. HCV-RNA levels were measured at baseline and weeks 0, 2, 4, 6, 8, 12, 20, 24, 36, 44, and 48. During treatment, HCV-RNA levels during treatment decreased by approximately 2.3 log in Whites vs. decreases of approximately 0.3 log in African Americans. Only 1 African-American participant (2%) achieved an SVR, while 46 white participants (12%), 4 Hispanic participants (10%), and 3 of the Asian-American participants (30%) achieved SVR (Reddy 1999).

Two efforts to increase virological response among African Americans by using high-dose interferon were unsuccessful. In one study, after 24 weeks of therapy, 26% of African Americans had undetectable HCV RNA vs. 60% of Whites (P<0.01). After 48 weeks, response rates among African Americans diminished to 10%, vs. 53% for Whites (P<0.0001) (De Maria 2002). A retrospective analysis of a treatment trial using two doses of interferon alfa-2b (3 MIU thrice weekly or 5 MIU daily) in African-American and white individuals with genotype 1 infections found similar initial responses among those treated with 3 MIU of interferon; however, when HCV-RNA levels on the high, daily-dose regimen were compared, African Americans had slower reductions in HCV RNA than Whites (Theodore 2003).

Data from two large clinical trials suggest that the addition of ribavirin increases virological response rates among African Americans. McHutchison and colleagues examined response rates from two large randomized trials utilizing four different treatment regimens. After 48 weeks of interferon monotherapy, no African-American participants achieved SVR. Adding ribavirin to interferon increased the percentage of African Americans achieving SVR from 0% to 23% (vs. 42% of Whites). Fewer than 4% (53/1744) of all participants were African Americans. Trials are rarely designed to ensure that the demographics of HCV infection in the United States are accurately reflected.

A majority of HCV-infected African Americans have HCV genotype 1 (Blatt 2000). Although genotype 1 infections do not respond to treatment as well as infections with genotypes 2 and 3, the differential response rates among African Americans cannot be attributed solely to genotype. Three treatment trials using standard interferon have reported impaired responses in African Americans with HCV genotype 1 (Kinzie 2001; Reddy 1999; Theodore 2003). Reddy and colleagues found fewer biochemical and virological response rates among African Americans vs. Whites with genotype 1 (6% vs. 34% for biochemical response rates; P=0.001; 6% vs. 22% for virological response rates during therapy; P=0.038). Kinzie and colleagues compared end-of- treatment responses of genotype 1-infected African Americans and Whites, finding that 2% (1/45) of African Americans achieved an ETR vs. 15% (5/33) of Whites (P<0.05) (Kinzie 2001). Although Theodore and colleagues saw similar response rates between African Americans and Whites with genotype 1 infections treated with 3 MIU of interferon thrice weekly, when the dose was increased to 5 MIU daily, Whites were most likely to have an initial response (P<0.001). Conversely, McHutchison and colleagues observed similar response rates among Blacks and Whites with genotype 1 infections (23% and 22%, respectively) in two large clinical trials (McHutchison 2000).

The pivotal studies of pegylated interferon had few African-American participants. Although data from subgroup analyses of these trials are available, the number of non-white participants has been too small to allow confident conclusions.

The efficacy of pegylated interferon alfa-2a plus ribavirin (1,000 mg-1,200 mg/day) has been assessed in 78 non-Hispanic African Americans and 28 non-Hispanic Whites, all with genotype 1 infections. Although sustained virological response rates among African Americans occurred more frequently in this trial than in previous studies, response rates remained greater among non-Hispanic Whites (Jeffers 2003).

Figure 2. Virological Response to Treatment in Non-Hispanic African Americans and Non-Hispanic Whites*
Figure 2. Virological Response to Treatment in Non-Hispanic African Americans and Non-Hispanic Whites*
* Treatment was completed by 63/78 non-Hispanic African Americans and 22/28 non-Hispanic white participants.

Recent evidence suggests that some African Americans who do not achieve SVR may attain histological benefit from HCV treatment, although the durability of the improvement is currently unknown. Cassidy and colleagues evaluated histological responses from paired biopsies of 53/78 African Americans treated with pegylated interferon alfa-2a and ribavirin (1,000-1,200 mg/day) for 48 weeks. SVR was achieved by 32% (17/53) with paired biopsies. Improvement in fibrosis (≥1 point decrease in Knodell fibrosis score) occurred in 29% (5/17) of those who achieved SVR as well as 22% (8/36) of virological non-responders (Cassidy 2003).

There is an urgent need to investigate the contribution of additional genetic, environmental, and other factors to these differential responses, so that interventions to improve virological and histological treatment outcomes among African Americans may be developed.

A retrospective analysis of data from a multicenter HCV treatment trial and a compassionate access program in Australia and New Zealand reported that response to HCV treatment may be different in Southeast Asians. Dev and colleagues analyzed data from 70 Southeast Asian and 50 white individuals with standard interferon alfa-2, using induction/maintenance or regular dosing with 1,000-1,200 mg/day of ribavirin. Those with HCV genotypes 2 and 3 were treated for 24 weeks; all others were treated for 48 weeks. HCV genotypes 7, 8, and 9 -- regarded as new genotypes rather than subtypes of genotype 6 as previously thought (Tokita 1994) -- were present in 33 Southeast Asians and emerged as independent predictors of an SVR (OR, 16.56; 95% CI, 4.16-18.04). SVR was achieved by 79% (26/33) of those with genotypes 7, 8, and 9. Unfortunately, because the sample size was small in this study (33 Southeast Asians with genotype 7, 8, or 9; 7 Southeast Asians and 44 Whites with genotype 1b), it is difficult to tease out the role of genotype vs. that of race. Southeast Asians with genotype 1b were five times as likely as Whites to achieve an SVR (OR, 4.63; 95% CI, 1.9-18.04), and there were no significant differences in treatment response by genotype or regimen among Southeast Asians (Dev 2002).

The duration of treatment may contribute to response rates. In San Jose, California, Nguyen and colleagues analyzed data from 38 Southeast Asians with HCV genotypes 6, 7, 8, and 9 who were treated for 24 weeks with either standard or pegylated interferon plus ribavirin. SVR was achieved by 54% (21/38), a lower rate than that reported in those with genotypes 6, 7, 8, and 9 after 48 weeks of treatment (Dev 2002; Hui 2003). There were no significant differences in response rate by treatment regimen, and the sample size was too small for analysis by genotype (M. H. Nguyen 2003).

It is not clear whether these differences reflect race, geographic diversity among Southeast Asians, genotype, a combination of these factors, or these and other additional factors. Identification of the factor(s) involved with differential responses to treatment may lead to improved treatment outcomes.

Weight

Lower body weight (≤85 kg /187 lbs; Fried and colleagues identified a slightly lower predictive threshold of ≤75 kg/165 lbs) is a known predictor of virological response to HCV treatment, whether standard or pegylated interferon is used (Fried 2002a; S. Lee 2002; Manns 2001).

Body mass index -- the ratio of body weight in kilograms to the square of its height in meters -- has been associated with virological and histological response to HCV treatment. Bressler and colleagues retrospectively reviewed data from 253 individuals treated with standard interferon with or without ribavirin. After controlling for age, sex, history of heavy alcohol consumption and cirrhosis at baseline, they found that a body mass index >30 kg/mg2 was an independent predictor of virological non-response to HCV treatment (Bressler 2003). Greater body mass index also has a negative effect on histological response to treatment. In a meta-analysis of data from three HCV treatment trials, Cammá and colleagues reported that obese and overweight individuals were less likely to experience improvement of fibrosis than those with a body mass index ≤30 kg/mg2 (OR, 0.56; 95% CI, 0.35-0.9) (Cammá 2004).

Weight is unique among prognostic factors, since it is the only one that may be modified by the individual. Pegylated interferon alfa-2b is dosed by body weight, as is ribavirin. It is clear that the dose of ribavirin has an impact on treatment outcomes for individuals with HCV genotype 1. The impact of ribavirin dosing on treatment outcomes has been difficult to analyze, because the dose of ribavirin has often been used as a surrogate for body weight. For individuals with HCV genotype 2 or 3, low body surface area and low body weight were the only variables significantly associated with achieving SVR (P=0.005 for low body surface areas; P=0.04 for low body weight) (Berg 2003).

Age and Sex

The likelihood of achieving a sustained virological response is greater in persons under 40 years old, and it continues to decrease with aging (Foster 2003; S. Lee 2002; Manns 2001; Poynard 1998; Poynard 2000). Females are more likely to achieve SVR than males (Manns 2001; Poynard 1998; Poynard 2000). Female sex and body weight are favorable prognostic indicators. Since females are usually smaller than men, a portion of this effect may be attributable to sex. The confluence of youth and sex appears to favor to premenopausal females, although the effect of hormones on response to treatment has not been characterized. If the favorable prognosis for treatment of young women does indeed have a hormonal component, perhaps hormones may be manipulated to increase treatment efficacy in other groups as well.

Cirrhosis

Treatment is contraindicated for individuals with decompensated cirrhosis, due to the risk of hepatic decompensation and death. Individuals with bridging fibrosis or compensated cirrhosis who have an urgent need for HCV treatment do respond to treatment, albeit less frequently than those with less advanced liver disease.

In a prospective, randomized study of standard interferon alfa-2a vs. three doses of pegylated interferon alfa-2a given to 271 individuals individuals with bridging fibrosis or cirrhosis, the greatest virological response rate -- 30% SVR -- was achieved with the highest dose of pegylated interferon (180 µg), although response rates for participants with poor prognostic factors (such as HCV genotype 1 and a high baseline HCV RNA level) receiving the same dose dwindled to 10%. Histological improvements occurred most frequently among those with a virological response (88% vs. 35% for non-responders) (Heathcote 2000).

Unfortunately, most data on the efficacy of pegylated interferon plus ribavirin in cirrhotics come from subgroup analyses from trials that have included only a small number of individuals with bridging fibrosis/compensated cirrhosis.

Steatosis

Hepatic steatosis -- deterioration of liver tissue marked by fat deposits in liver cells -- has been associated with hepatitis C infection, particularly genotype 3a, and linked with fibrosis progression (Castéra 2003; Gochee 2003; Hu 2003; Romero-Gomez 2003; Westin 2002). The presence of steatosis may decrease the probability of achieving SVR (Poynard 2003; Zeuzem 2003).

ALT and GGT Levels

High baseline alanine aminotransferase (ALT) levels and low-to-normal baseline levels of gamma-glutamyl transferase (GGT) are predictors of sustained virological response to HCV treatment (see Chapter IV, Diagnostics) (Berg 2003; S. Lee 2002; Pawlotsky 1996). Lee and colleagues, looking for baseline factors associated with achievement of an SVR, analyzed data from 814 participants in three randomized trials of pegylated interferon and found that pre-treatment ALT >3 times the upper limit of normal (ULN) was independently associated with SVR (OR=2.34; P<0.0001) (S. Lee 2002). In an analysis of clinical, biochemical, histological, and virological characteristics of 260 participants in HCV treatment trials (of pegylated and standard interferons), a low baseline GGT level (P<0.0001), and a high baseline ALT level (P=0.002) were identified as predictors of SVR in individuals with HCV genotype 1 (Berg 2003).

Liver Histology Index

The Knodell Histological Activity Index (HAI; see Chapter IV, Diagnostics) at baseline has been identified as an independent predictor of SVR by an analysis of pooled data from three large, randomized clinical trials of pegylated interferon alfa-2a. A pre-treatment HAI score of >10 was significantly associated with SVR in cirrhotics as well as non-cirrhotics (overall, P=0.0410; for non-cirrhotics, P=0.0268) (S. Lee 2002).

Viral Kinetics

Hepatitis C viral kinetics are steady state; the continuous release of virions is balanced by a constant removal of virions from the bloodstream. The number of newly infected hepatocytes is counterbalanced by the apoptosis of infected hepatocytes. The estimated serum half-life of an HCV virion is between two and three hours (A. U. Neumann 1998). HCV-infected cells have a half-life of 1-70 days (Herrmann 2000).

Initial- and Second-Phase Viral Decay

Neumann and colleagues observed a biphasic decline in HCV by looking at blood samples from 23 HCV-infected individuals at initiation of treatment with interferon. HCV RNA levels remained at baseline for 8.7 ± 2.3 hours; then, an initial-phase decline occurred as interferon began to inhibit the production and release of new virions into the bloodstream. The amount of viral decay ranged from 0.5 to 2.0 log, depending on the dose of interferon. This decline stabilized after 24 to 48 hours of treatment. A less rapid, second-phase decline occurred between day two and day fourteen. During this second phase, interferon continued to block production of HCV, and virions were cleared from the bloodstream. The second-phase decrease in HCV-RNA is not dose-dependent (A. U. Neumann 2000).

Both the initial-phase rapid decline and the slower, second-phase decline in HCV RNA levels may be predictors of response to treatment. Although the second-phase decline has been regarded as the best predictor of SVR, the initial phase decline (at 24 hours after initiation of treatment) may be an important predictor of second-phase decline and, therefore, an early predictor of response to treatment (Carlsson 2002; Jessner 2001; Layden 2002a; Layden 2002b). A retrospective analysis of two studies by Layden and colleagues found strong correlations with lower viral loads at the end of the 24-hour initial-phase decline and more rapid second-phase declines (P<0.001). Individuals with HCV RNA <250,000 copies/mL after the first phase of viral decay were the only ones who achieved sustained virological responses (Layden 2002a). In another study of the predictive value of HCV RNA levels 24 hours after initiation of treatment, Jessner and colleagues observed that individuals with viral load decreases of less than 70% of baseline were likely to be non-responders after 24 weeks of treatment. This would mean that an individual with a baseline viral load of 2,000,000 copies/mL would most likely be a non-responder if his or her viral load remained above 600,000 copies/mL 24 hours after initiating treatment. This approach identified non-responders with a specificity of 100%, a sensitivity of 83%, a positive predictive value of 100%, and a negative predictive value of 77% (Jessner 2001).

More evidence to support the predictive value of 24-hour viral loads comes from Ferenci and colleagues, who observed that those with 12-week EVRs experienced sharper declines in 24-hour viral loads than non-responders. In week-12 responders, 24-hour viral load declines were 1.19 log ± 0.43 (SD), while non-responders had 24-hour viral load declines of 0.55 log ± 0.36 (SD) (Ferenci 2002).

Hopefully, research will identify individuals who are likely to have virological, biochemical, and histological responses early in the course of treatment. Until more information about predictors of biochemical and histological responses in the absence of virological responses is available, treatment decisions based on a 24-hour viral load must be considered premature. Some individuals may see much-needed improvements in liver histology even in the absence of virological response; discontinuing treatment would prevent an opportunity for histological benefit.

Early Stopping Rules

The likelihood of achieving sustained virological response to treatment may be predicted by early virological response after 12 weeks of treatment. Individuals who do not have either an undetectable HCV RNA or a 2-log decrease in HCV RNA are unlikely to have an SVR (Davis 2003b; Castro 2002; Civeira 1999; Fried 2002a; S. Lee 2002; A. U. Neumann 1998; Rosen 2002). Fried and colleagues found that 65% (253/390) of those treated with pegylated interferon alfa-2a plus ribavirin who achieved EVR also achieved SVR. Only 3% (2/63) of the individuals without an EVR had an SVR (Fried 2002a).

In a meta-analysis of data from trials of pegylated interferon alfa-2a, Lee and colleagues found a negative predictive value (NPV) of EVR of 91% at week 4; it increased slightly to 95% at week 8, and rose to 98% at week 12 (a high NPV is used to determine when therapy can be discontinued, because achieving an SVR after completing the full course of treatment is extremely unlikely). The positive predictive value (PPV) of an EVR, according to this meta-analysis, was not as useful for guiding treatment decisions (the higher the PPV, the more likely that an individual may achieve an SVR; a high PPV may encourage people to continue treatment). At week 4, the positive predictive value of EVR was 54%; it decreased to 49% at week 8 and to 46% at week 12 (S. Lee 2002).

Data from an earlier study by McHutchison and colleagues, which used standard interferon (either with or without ribavirin), revealed that detectable HCV RNA at 12 weeks of therapy predicted non-response in 89% of individuals; waiting until 24 weeks to identify non-responders (by detectable HCV RNA) increased this to 99% (McHutchison 2001). It is possible, however, that the regimen of standard interferon used in this study may have influenced the length of time necessary for identifying non-responders. Using a 24 week cutoff for non-response derived from a standard interferon treatment trial may not be applicable to persons treated with pegylated interferon.

In an effort to develop an algorithm for early discontinuation of HCV treatment applicable to both standard and pegylated interferon-based regimens, Berg and colleagues analyzed data from 209 individuals enrolled in five different HCV treatment protocols. Pre-treatment virological, histological, biochemical, and clinical parameters were examined for their importance in predicting SVR. Participants received 24 or 48 weeks of treatment. Treatment included ribavirin (dose of 800 -1,200 mg/day), with the exception of 19 individuals who received pegylated interferon alfa-2a monotherapy. Regimens included two different induction/maintenance strategies with standard interferon alfa-2a, thrice weekly standard interferon (alfa-2a and alfa-2b), and two pegylated interferon-based regimens -- alfa-2b (Peg-Intron®) and alfa-2a (Pegasys®). HCV RNA testing was performed on stored serum samples at baseline and after 4 and 12 weeks of treatment.

The predictive thresholds for baseline HCV RNA, baseline ALT and baseline GGT levels, and HCV RNA levels at week 4 and week 12 were identified; week 12 cutoff values were used for the algorithm. At week 12, the NPV of HCV RNA ≤30,000 IU/mL was 100%; positive predictive value was 64.8%. There were no significant differences in the applicability of these thresholds by treatment regimen.

The algorithm proposed by Berg and colleagues recommends discontinuation of treatment at week 12 if HCV RNA is >30,000 IU/mL, or if there has been less than a 2-log (99%) decrease in HCV RNA from baseline. If HCV RNA is between 30,000 and 35,000 IU/mL, repeat testing is recommended. For those with HCV RNA below the threshold of discontinuation, a qualitative HCV RNA test should be performed at 24 weeks; if HCV RNA is detectable at that time, the algorithm recommends discontinuation of treatment (Berg 2003).

Additional research using viral kinetics to determine early stopping rules is underway. Using data from 127 participants treated with 180 µg/week of pegylated interferon alfa-2a plus 1,000-1,200 mg/day of ribavirin for 48 weeks, Neumann and colleagues worked to identify the earliest reliable time point and decrease in HCV RNA level for predicting sustained virological response. No one achieved an SVR unless their HCV RNA was <5.5 log on treatment day four, or they had a decrease of >0.5 log (approximately a threefold drop) on treatment day seven. These parameters had a negative predictive value of 100% (A. U. Neumann 2003). Prospective studies are needed to validate these and other early stopping rules.

Duration of Treatment

Extending HCV treatment for an additional 24 weeks has been suggested as a strategy to improve treatment outcomes in genotype 1. Drusano and colleagues developed a model to predict SVR after treatment with pegylated interferon alfa-2b, using data from participants in the Manns trial. The model predicted that individuals with genotype 1 would need to have continuously undetectable HCV RNA for at least 32 weeks to achieve a sustained virological response. Since the model found that, on average, it took 30.2 weeks for HCV RNA to become undetectable, the authors suggested that 48 weeks of treatment might be insufficient for genotype 1 (Drusano 2004). Although this model has limits, a prospective investigation could help to identify individuals who might benefit from extended therapy.

However, extending duration of therapy may increase treatment discontinuations rather than sustained virological response rates. Sanchez-Tapias randomized 326 individuals who had detectable HCV RNA after 4 weeks of treatment to either 44 or 68 additional weeks of pegylated interferon alfa-2a plus 800 mg/day of ribavirin, for a total of 48 or 72 weeks of treatment. Although they did not observe an increase in neutropenia or thrombocytopenia with longer treatment, they reported a difference in withdrawal rates by treatment duration (17% vs. 36% in the extended duration group). Sustained virological response rates did not differ significantly by treatment arm (30% for 48 weeks vs. 36% for 72 weeks) (Sanchez-Tapias 2004). The rate of sustained virological responses was not broken out by genotype in this study, so it is difficult to assess the effect of extended treatment on virological responses in genotype 1.

Conversely, a subset of individuals with genotype 2 or genotype 3 may achieve sustained virological responses after less than 24 weeks of treatment. In a randomized, prospective study of 280 individuals with genotype 2 and 3, Mangia and colleagues used HCV RNA level after 4 weeks of treatment to determine duration of treatment for 210/280 individuals; the remaining 70 were treated for 48 weeks. When HCV RNA was undetectable at 4 weeks, treatment was discontinued at 12 weeks. Those with detectable HCV RNA at week 4 were treated for a total of 24 weeks. SVR was achieved more frequently among those treated for 12 weeks than 24 or 48 weeks (89.9%, 78.7% and 81.4%, respectively). Relapse rates were lowest after 48 weeks of treatment; they increased from 0-2.5% after 24 weeks of treatment and 10% after 12 weeks of treatment (Mangia). Response rates were greater among those with genotype 2 (82%) than those with genotype 3 (64%), regardless of duration of treatment. This study used a lower dose of pegylated interferon alfa-2b (1.0 µg/kg per week) and a higher dose of ribavirin (1,000-1,200 mg/day) than has been recommended for treatment of genotype 2 and genotype 3 (P-IFN 1.5 µg/kg per week; RBV 800 mg/day). Prospective study of early virological responses with different doses of pegylated interferon and ribavirin will help to clarify optimal regimen and duration of therapy for persons with genotype 2 and genotype 3.

The Difficulty of Comparison

Although study results from trials of each drug have been compared (often by one company or the other, to indicate its product's advantage), there has not been a head-to-head comparison of the safety, efficacy, and tolerability of the two pegylated interferons. Efficacy, safety, and tolerability of each product appear similar, but without a direct comparison we must rely on the experience of clinicians who have used both products. While it is tempting to compare the two, a true comparison is not possible; participant characteristics and treatment regimens differ across studies. The only comparison to date is a small study of hepatitis C viral kinetics during treatment with Pegasys® or Peg-Intron® and ribavirin. A suboptimal dose of Peg-Intron® was used in this study (1.0 µg/kg, the recommended dose for Peg-Intron® monotherapy; 1.5 µg/kg is the recommended dose for combination therapy). The study compared mean week-12 viral loads, finding that those who received Pegasys® had significantly lower viral loads (2.82 log10 vs. 3.87 log10; P<0.01) (Bruno 2002). This information raises questions about the recommended dose for Peg-Intron® monotherapy.

Key Studies of Combination Therapy: Pegylated Interferon Plus Ribavirin

Three pivotal large, randomized clinical trials of pegylated interferon plus ribavirin (with similar inclusion/exclusion criteria) have shown that the combination of pegylated interferon plus ribavirin is the most effective treatment for chronic hepatitis C. Overall sustained virological response rates are often presented as evidence of treatment efficacy in all individuals with chronic hepatitis C although individuals with one or more poor prognostic factors were excluded from these trials.

The Manns Data

Manns and colleagues conducted a large (1,530 person), three-arm study, comparing the safety and efficacy of:

  • Standard interferon alfa-2b (3 MIU, thrice weekly), plus ribavirin dosed at 1,000-1,200 mg/day for 48 weeks;

  • Pegylated interferon alfa-2b (1.5 µg/kg, once weekly), plus ribavirin dosed at 800 mg/day for 48 weeks; and

  • Pegylated interferon alfa-2b (1.5 µg/kg, once weekly for four weeks, then reduced to 0.5 µg/kg), plus ribavirin dosed at 1,000-1,200 mg/day for 48 weeks.

Comparisons across treatment arms are problematic in the Manns study. It is possible that the induction/maintenance arm did not offer its participants a sufficient dose of pegylated interferon, while those in the higher-dose pegylated interferon arm may not have received a sufficient dose of ribavirin. It's as if someone tried to bake three cakes: one with a proper proportion of known ingredients (but using inferior flour), one with not quite enough baking powder, another with not quite enough flour -- and then looked to see if the cakes rose nonetheless.

Figure 3. Sustained Virological Responses by Treatment Regimen
Figure 3. Sustained Virological Responses by Treatment Regimen

Figure 4. Sustained Virological Response by Genotype
Figure 4. Sustained Virological Response by Genotype

Figure 5. Sustained Virological Response by Liver Histology
Figure 5. Sustained Virological Response by Liver Histology

The probability of achieving an SVR increased with the higher doses of ribavirin and pegylated interferon (OR, 1.7; P=0.002). When weight-based dosing of ribavirin was taken into account, the estimated effect of high-dose (vs. lower dose) pegylated interferon was larger (OR, 1.7); however, post hoc analysis used ribavirin dose as a proxy for, rather than a reflection of, body weight. (Weight-based dosing of ribavirin has been correlated with greater response rates in many studies of RBV plus standard or pegylated interferon.) Unfortunately, these data led to the approval of Peg-Intron® with a recommended daily dose of 800 mg of ribavirin, which may be suboptimal for some individuals. Higher doses of ribavirin are recommended in the European Union (1,000 mg daily for individuals who weigh less than 75 kg (165 lbs) and 1,200 mg daily for individuals who weigh 75 kg or more), but statistically significant prospective data on the efficacy of weight-based ribavirin are not yet available.

Overall, SVR occurred most frequently with the higher dose of pegylated interferon (54% vs. 47% for the other two dosing arms). In the same higher dose arm, 42% of those with genotype 1 and 42% of those with a high baseline viral load (>2 million) achieved SVR.

Possessing genotype 1 and a high baseline viral load substantially influenced the response to treatment. When response rates are broken out by baseline viral load and genotype, significant differences by baseline viral load among those with genotype 1 emerge. Only 30% of those with a high baseline viral load achieved SVR after treatment with pegylated interferon 1.5 µg/kg plus 800 mg of RBV, while 68% with low baseline viral loads achieved SVR. Among those with genotype 1/high baseline viral load, there was virtually no difference in response by regimen (30% for P-IFN vs. 29% for standard IFN). While the package insert includes this data, the study did not include this analysis, which is relevant for the majority of people in the United States contemplating HCV treatment.

Figure 6. Response by Genotype, Baseline HCV RNA Level, and Treatment Regimen
Figure 6. Response by Genotype, Baseline HCV RNA Level, and Treatment Regimen

The Manns study did not address questions about the optimal duration of therapy for each HCV genotype. All participants received 48 weeks of therapy, which may have been longer than necessary for those with genotype 2 or genotype 3. A year before the Manns study was published, Poynard and colleagues, based on their analysis of data from 1,744 treatment-naive persons in two large trials, suggested discontinuation of treatment (standard interferon plus ribavirin) for individuals with HCV genotype 2 or genotype 3 who had undetectable HCV RNA after completing 24 weeks of therapy. They found that 82% of those with HCV genotype 2 or genotype 3 who were HCV-RNA-undetectable after 24 weeks of therapy achieved SVR. If therapy was continued for an additional 24 weeks, the rate of SVR rose by only 2% (Poynard 2000). A look at the Manns data broken out by genotypes 2 and 3 shows very little difference by treatment regimen. It is difficult to tell whether the similarities in response between the lower-dose pegylated interferon arm and the standard interferon arm are a consequence of an insufficient dose of pegylated interferon, differing baseline HCV RNA levels within genotypes, or other prognostic factors.

Figure 7. Sustained Virological Response Rate by Treatment Regimen and Genotype
Figure 7. Sustained Virological Response Rate by Treatment Regimen and Genotype

Figure 8. Sustained Virological Response Rate by Treatment Regimen and Baseline Viral Load*
Figure 8. Sustained Virological Response Rate by Treatment Regimen and Baseline Viral Load*
* High viral titer, >2 million; low viral titer, ≤2 million

Figure 9. Sustained Virological Response Rate by Treatment Regimen and Liver Histology
Figure 9. Sustained Virological Response Rate by Treatment Regimen and Liver Histology

Although many did not achieve a sustained virological response, histological improvement was observed in all treatment groups. Histological improvement occurred most frequently with SVR; 90% of those who achieved an SVR also had improvement in liver histology. Some degree of histological improvement (ranging from -0.8 to -1.3) was seen in 44% of non-responders. About 20% of each treatment group had improvement of fibrosis (defined as a decrease of at least one in the Knodell HAI score). However, without long-term follow up, it is not possible to assess the durability and clinical impact of such improvements in relapsers and non-responders.

Dose reductions due to neutropenia occurred in 18% of those on high-dose pegylated interferon vs. 8% on standard interferon. Only 1% discontinued treatment because of neutropenia. Dose modifications were more frequent with pegylated interferon/high-dose ribavirin than with standard interferon/high-dose ribavirin arm (49% vs. 34%), mostly due to neutropenia.

Table 2. Adverse Events By Treatment Regimen
Table 2. Adverse Events By Treatment Regimen

Adverse events were clustered in five groups: flulike symptoms, gastrointestinal symptoms, psychiatric symptoms, respiratory symptoms, and dermatological symptoms. The adverse events reported in this chart occurred in at least 10% of study participants. The number of individuals experiencing more than one adverse event was not provided.

Table 3. Treatment Discontinuations and Dose Reductions for Adverse Events
Table 3. Treatment Discontinuations and Dose Reductions for Adverse Events

Discontinuation rates were similar across arms (13% from the pegylated interferon arm and 14% from the standard interferon arm).

The Fried Data

Fried and colleagues conducted a large, international trial, in which 1,121 individuals with chronic HCV were randomized into one of three treatment arms:

  • Pegylated interferon alfa-2a,180 µg once weekly, plus ribavirin 1,000-1,200 mg/day for 48 weeks;

  • Pegylated interferon alfa-2a, 180 µg once weekly, plus placebo for 48 weeks; or

  • Standard interferon alfa-2b, 3 MIU thrice weekly, plus ribavirin 1,000-1,200 mg/day for 48 weeks.

Figure 10. End-of-Treatment and Sustained Virological Responses by Regimen

The label of Copegus® (Roche's ribavirin) breaks out SVR data by genotype.

Figure 11. Sustained Virological Responses by Regimen and Genotype

Figure 12. Sustained Virological Response Rate by Regimen and Genotype: High Baseline HCV RNA

Figure 13. Sustained Virological Response Rate by Regimen and Genotype: Low Baseline HCV RNA

Figure 14. Sustained Virological Response Rate: Genotype 4 and Cirrhosis
Figure 14. Sustained Virological Response Rate: Genotype 4 and Cirrhosis
* Data not broken out by baseline viral load.
** Data not broken out by baseline viral load or genotype.

Duration of therapy by genotype was not addressed in this study, nor were questions about optimal dosing of pegylated interferon and ribavirin, although interesting information emerged about SVR and dose modifications. The rate of SVR among individuals with early virological responses in the P-IFN/RBV arm was 75%. When the authors looked at early virological responders from the same arm that had significant dose reductions (of at least 20% in doses of both drugs), the rate of SVR only dropped to 67%. Further exploration of the safety and efficacy of lower doses of pegylated interferon alfa-2a (150 µg or 135 µg) is needed.

Aside from a greater frequency of neutropenia and thrombocytopenia, adverse events from the pegylated interferon arm were similar to those in the standard interferon arm. People on pegylated interferon had fewer flulike symptoms and less frequent depression than those on standard interferon.

Table 4. Dose Modifications Due to Laboratory Abnormalities*
Table 4. Dose Modifications Due to Laboratory Abnormalities*
* Laboratory abnormalities also included elevations of alanine aminotransferase levels (not shown).

Table 5. Discontinuations for Laboratory Abnormalities and Adverse Events
Table 5. Discontinuations for Laboratory Abnormalities and Adverse Events

There were three deaths in this trial (due to hypertensive heart disease, drowning, and liver cancer), none considered to be related to treatment.

The Hadziyannis Data

Hadziyannis and colleagues took a closer look at ribavirin dosing and duration of therapy by genotype in a multinational, randomized, four-arm study of 1,284 individuals with chronic hepatitis C. Participants received a fixed dose of pegylated interferon alfa-2a (180 µg once weekly) for either 24 or 48 weeks, with ribavirin doses of either 800mg/day or 1,000-1,200 mg/day. The four arms of the study were:

  • Arm one: pegylated interferon alfa-2a, 180 µg once weekly, plus 800 mg/day of ribavirin for 24 weeks;

  • Arm two: pegylated interferon alfa-2a, 180 µg once weekly, plus 1,000-1,200 mg/day of ribavirin for 24 weeks;

  • Arm three: pegylated interferon alfa-2a, 180 µg once weekly, plus 800 mg/day of ribavirin for 48 weeks; and

  • Arm four: pegylated interferon alfa-2a, 180 µg once weekly, plus 1,000-1,200 mg/day of ribavirin for 48 weeks.

Randomization was stratified by genotype and viral titer (low vs. high: below or at least 2 million copies). Individuals with genotype 1/high viral load were randomized 1 to 1 to 4 to 4 (10%, 10%, 40%, 40%). Individuals with a non-1 genotype and a low viral titer were randomized 1 to 1.5 to 1 to 1.5 (20%, 30%, 20%, 30%). Due to this randomization scheme, the results of this trial are comparable only within a particular genotype and viral load stratum; the overall virological response across arms does not reflect a purely random distribution of baseline characteristics.

Table 6. Randomization and Allocation Table
Table 6. Randomization and Allocation Table

Table 7. Baseline Characteristics
Table 7. Baseline Characteristics

Data were analyzed by modified intention-to-treat, including everyone who received at least one dose of medication (1284/1311), rather than everyone who was enrolled. Individuals who did not achieve a week-24 virological response were offered the option of treatment discontinuation.

Most participants were white males (65% male; 89% white). Roche is sponsoring another trial (the National Institutes of Health's Study of Viral Resistance to Anti-Viral Therapy [Virahep-C]) that will evaluate response to treatment among African Americans. Unfortunately, the number of African Americans with genotype non-1 infections enrolled in this trial was too small to draw any conclusions about dosing, duration, and the likelihood of achieving SVR in this group.

Figure 15. Sustained Virological Response Rate in Genotype 1 by Regimen, Treatment Duration, and Baseline Viral Load
Figure 15. Sustained Virological Response Rate in Genotype 1 by Regimen, Treatment Duration, and Baseline Viral Load
* High viral titer is >2 million copies; low viral titer is ≤2 million copies.

The Hadziyannis data is especially relevant to most people in the United States, where genotype 1 is predominant. Forty-eight weeks of treatment with weight-based dosing of ribavirin yielded the highest rate of sustained virological responses for individuals with genotype 1, regardless of baseline viral load.

Figure 16. Sustained Virological Response Rate in Genotypes 2 and 3 by Regimen, Treatment Duration, and Baseline Viral Load
Figure 16. Sustained Virological Response Rate in Genotypes 2 and 3 by Regimen, Treatment Duration, and Baseline Viral Load

Response rates for HCV genotypes 2 and 3 did not differ significantly by regimen or duration of treatment . For people with genotype-2 and genotype-3 infections, 24 weeks of treatment and a lower ribavirin dose appear to be as effective as a 48-week course of treatment and a higher ribavirin dose. There were fewer severe adverse events and discontinuations among those who received 24 weeks of therapy with the lower dose of ribavirin. This is good news for people with HCV genotypes 2 and 3.

Figure 17. Sustained Virological Response Rate in Genotype 1 by Regimen, Treatment Duration, and Baseline Liver Histology
Figure 17. Sustained Virological Response Rate in Genotype 1 by Regimen, Treatment Duration, and Baseline Liver Histology

Figure 18. Sustained Virological Response Rate in Genotype 2 and 3 by Regimen, Treatment Duration, and Baseline Liver Histology
Figure 18. Sustained Virological Response Rate in Genotype 2 and 3 by Regimen, Treatment Duration, and Baseline Liver Histology

Here, HCV genotype remains a significant prognostic factor among individuals with bridging fibrosis or cirrhosis, although the sample size was small. Among those with genotype 2 or 3 and serious liver damage, neither duration of treatment nor dose of ribavirin had a significant impact on SVR. In genotype 1, the highest rate of SVR was achieved with both the greater duration of treatment and the higher of ribavirin. Unfortunately, no data on changes in liver histology were available.

Other interesting information emerged about treatment response and toxicities based on geographic region. There were 441 participants in the U.S. and 843 non-U.S. participants (from Australia, Belgium, Brazil, Canada, Denmark, Finland, France, Germany, Greece, Ireland, Italy, Mexico, the Netherlands, New Zealand, Norway, Portugal, Spain, Sweden, Taiwan, and the UK). Participants in the U.S. experienced more treatment-related toxicities and achieved SVR less frequently than did non-U.S. participants (FDA 2002).

Table 8. Prognostic Factors in U.S. and Non-U.S. Participants
Table 8. Prognostic Factors in U.S. and Non-U.S. Participants

The difference in response rates may be attributed in part to a greater proportion of poor prognostic factors among U.S. participants. However, HCV genotype 1 in the U. S. may be a different entity than non-U.S. genotype 1, since there can be substantial genetic diversity among strains within a genotype (see Chapter IV, Diagnostics). It is possible that genotype 1 infections in the U.S. may respond differently to treatment than genotype 1 infections in other parts of the world.

This study did not resolve questions about optimal dosing of pegylated interferon. Initially, a fixed dose of pegylated interferon was given to all participants. Treatment-related hematologic abnormalities were managed by dose modification rather than through administration of hematopoietic growth factors. Overall, more than 30% of those receiving 48 weeks of therapy modified or omitted at least one dose of pegylated interferon.

Table 9. Pegylated Interferon and Ribavirin Dose Modifications by Study Arm
Table 9. Pegylated Interferon and Ribavirin Dose Modifications by Study Arm

Adverse events reported by 20% of those who received at least one dose of study medications, from most to least common, included flulike symptoms, insomnia, irritability, hair loss, itching, depression and skin inflammation.

Table 10. Severe and Serious Adverse Events (SAEs)
Table 10. Severe and Serious Adverse Events (SAEs)
* Two deaths were unrelated to therapy (both drug overdoses). Of the two therapy-related deaths, one was caused by septicemia associated with neutropenia, and one by suicide.

Table 11. Treatment Withdrawals By Study Arm
Table 11. Treatment Withdrawals By Study Arm

Pegylated Interferon Monotherapy

Although combination therapy with ribavirin is considered to be the current standard of care for the treatment of chronic hepatitis C, ribavirin may be contraindicated for some individuals who still need to treat their HCV. Ribavirin has caused birth defects and death in exposed animal fetuses at doses as low as one-twentieth of those recommended for human beings. Consequently, it is contraindicated for men and women who are planning a pregnancy; pregnant women and their sexual partners; and breast-feeding women.

For those engaging in procreative sex, the use of two forms of contraception during treatment and for six months after completion of treatment is recommended. Ribavirin is contraindicated for persons with severe renal impairment (creatinine clearance of <50 mL/min); individuals with a history of significant or unstable cardiac disease; individuals with hemoglobinopathies (e.g., sickle-cell anemia, thalassemia major); autoimmune hepatitis; advanced hepatic decompensation (before or during treatment); and anyone allergic to ribavirin.

Little is known about the safety and efficacy of ribavirin in transplant recipients and individuals with HIV/HBV/HCV infection. More data are needed on safety and efficacy of ribavirin in persons under 18 years of age. Roche's pediatric safety and efficacy study of Pegasys® with and without Copegus® is expected to open in mid-2004; final data will not be available for several years. Schering has not performed pharmacokinetic evaluations of ribavirin in this population. Little is known about the response to ribavirin in geriatric individuals, as there have been so few study participants over 65 years of age, nor have there been pharmacokinetic evaluations of ribavirin in the elderly. Clearly, data concerning safety, efficacy and pharmacokinetics are needed in these populations.

Results from two large randomized, controlled trials of treatment-naive individuals established the efficacy of pegylated interferon monotherapy is superior to that of standard interferon monotherapy (Lindsay 2001; Zeuzem 2000). These studies provide a wealth of data on the dosing, efficacy, side effects and adverse events of pegylated interferon therapy.

The Zeuzem Data

Zeuzem and colleagues compared pegylated interferon monotherapy to standard interferon monotherapy in a study of 531 individuals randomized to receive either:

  • Six million units of standard interferon alfa-2a thrice weekly for 12 weeks, continuing on a lower dose of three million units thrice weekly for 36 weeks (total course of therapy: 48 weeks); or

  • Pegylated interferon alfa-2a (Pegasys®) 180 µg once weekly for 48 weeks.

Figure 19. End-of-Treatment Response, Sustained Virological Response, and Biochemical Response by Treatment Regimen
Figure 19. End-of-Treatment Response, Sustained Virological Response, and Biochemical Response by Treatment Regimen
* P=0.001 for comparison of pegylated interferon vs. standard at 48 and 72 weeks, as well as for sustained biochemical response.

Figure 20. Histological Response at Week 72 from Paired Biopsy Specimens* by HAI.
Figure 20. Histological Response at Week 72 from Paired Biopsy Specimens* by HAI.
* A subgroup of 351 (66%) participants had paired baseline and post-treatment liver biopsies (184 received pegylated interferon and 167 received standard interferon). Biopsies were evaluated with the Knodell Histological Activity Index (HAI).

Adverse events, dose reductions, and discontinuations were similar across arms. The adverse events reported in Table 12 occurred in at least 10% of study participants.

Table 12. Adverse Events by Treatment Regimen
Table 12. Adverse Events by Treatment Regimen

Table 13. Dose Modifications and Discontinuations
Table 13. Dose Modifications and Discontinuations
* Some individuals had adverse events and laboratory abnormalities.

The Lindsay Data

In a study of 159 individuals with chronic hepatitis C, Lindsay and colleagues compared three different doses of pegylated interferon alfa-2b (Peg-Intron®) to a fixed dose of standard interferon. Participants were randomized to one of four arms:

  • Pegylated interferon alfa-2b, 0.5 µg/kg once weekly;

  • Pegylated interferon alfa-2b, 1.0 µg/kg once weekly;

  • Pegylated interferon alfa-2b, 1.5 µg/kg once weekly; or

  • Standard interferon alfa-2b, 3 MIU thrice weekly.

Virological responses at the end of treatment were significantly greater in those who received the two higher doses of pegylated interferon (1.0 and 1.5 µg/kg). Responses through week 48 were dose-dependent; by week 72, the discrepancy in response rates between the two higher doses disappeared, due to high rates of post-treatment relapse. The authors attributed this discrepancy to two factors: higher relapse rates for those with genotype 1 who were treated with 1.5 µg/kg vs.1.0 µg/kg (66% (57/87) and 46% (23/50) respectively; P=0.025); and a greater proportion of participants with genotype 1 in the 1.5 µg/kg arm (73% vs. 67% for the other two arms; P=0.09). Relapse rates among participants with genotypes 2 and 3 were similar (36% in the 1.0 µg/kg arm and 38% in the 1.5 µg/kg arm).

Figure 21. End-of-Treatment Response Rate and Sustained Virological Response Rate
Figure 21. End-of-Treatment Response Rate and Sustained Virological Response Rate
* P=0.01 for P-IFN 0.5.
** P≤0.001 for P-IFN 1.0 and P-IFN 1.5 at ETR and for SVR.

Figure 22. Sustained Virological Response by Dose and Formulation of Interferon, Baseline HCV RNA and Genotype
Figure 22. Sustained Virological Response by Dose and Formulation of Interferon, Baseline HCV RNA and Genotype

Paired liver biopsy specimens were available from 61% (744/1219) of study participants. The proportion of individuals with a histological response to treatment, as well as the degree of improvement, was similar across all arms (47% to 50%; mean decreases of -1.2 to -1.8 by the Knodell Histologic Activity Index). Although histological improvement was more frequent among those with an SVR (77% to 90%), 33% to 46% of relapsers and 31% to 41% of non-responders achieved histological improvement.

Table 14. Histological Response by Knodell HAI Scoring System: Mean Changes from Baseline
Table 14. Histological Response by Knodell HAI Scoring System: Mean Changes from Baseline

It is encouraging that a percentage of virological and biochemical relapsers and non-responders were able to achieve some degree of improvement in liver histology from pegylated interferon monotherapy, although longer follow-up is needed to assess the durability and clinical value of such improvements.

Although the virological response rates seen with pegylated interferons are an improvement over standard interferon, the side effects are still considerable.

Table 15. Adverse Events by Treatment Regimen
Table 15. Adverse Events by Treatment Regimen

Leukocyte, neutrophil, and platelet counts decreased in all arms initially, stabilized after the first few weeks of treatment, and returned to baseline after treatment. Dose reductions for neutropenia occurred more frequently in the 1.5 µg/kg arm (5% vs. 2-3%).

Dose reductions for thrombocytopenia occurred more frequently in the pegylated interferon arms (2-3% vs. 0.3% for standard interferon). Dose reductions occurred most frequently with the two higher doses of pegylated interferon. Discontinuations were similar across the pegylated interferon arms (9-11%), and higher than those in the standard interferon arm (6%) (Lindsay 2001).

Table 16. Discontinuations and Dose Reductions by Dose and Formulation of IFN
Table 16. Discontinuations and Dose Reductions by Dose and Formulation of IFN

Unresolved Dosing Issues: The Formann Data

The rationale for recommending a different dose of pegylated interferon alfa-2b (Peg-Intron®) for monotherapy (1.0 µg/kg) than that for use in combination with ribavirin (1.5 µg/kg) is unclear. Formann and colleagues randomized 20 individuals to receive 1.0 µg/kg of Peg-Intron® either once or twice weekly for four weeks. Blood levels of Peg-Intron® were below the level of detection by day seven in all but one of the once-weekly dosing group. Those who were randomized to receive twice-weekly dosing had constantly detectable levels of drug. Throughout the four-week induction period, members of the once-weekly group had higher levels of HCV RNA. Viral loads appeared to increase as drug levels decreased. At day 28, 5/10 of the twice-weekly dosing group had undetectable HCV RNA vs. 3/10 of the once-weekly dosing group (Formann 2002). This has raised concern about the recommended dose of 1.0 µg/kg Peg-Intron® for monotherapy; it may be suboptimal.

The Reddy Data

Pegylated interferon alfa-2a (Pegasys®) is not dosed by weight. Dosing for subsequent clinical trials of pegylated interferon alfa-2a was determined by Reddy and colleagues in a dose-ranging study completed by 122 of 159 original participants. The high discontinuation rates in the 180 and 270 µg arms (22% and 20%, respectively) may be attributable to the original protocol design, which initially did not allow dose modifications. Dose modification guidelines were not instituted until several months after the study opened (Reddy 2001).

Participants were randomized to receive either:

  • Pegylated interferon alfa-2a, 45 µg once weekly, for 48 weeks;

  • Pegylated interferon alfa-2a, 90 µg once weekly, for 48 weeks;

  • Pegylated interferon alfa-2a, 180 µg once weekly, for 48 weeks;

  • Pegylated interferon alfa-2a, 270 µg once weekly, for 48 weeks; or

  • Standard interferon alfa-2a, 3 MIU thrice weekly, for 48 weeks.

End-of-treatment and week-72 virological response rates were significantly greater in the pegylated interferon dosing arms of 90, 180, and 270 µg.

Figure 23. End of Treatment Response, Sustained Virological Response, and Week-72 Biochemical Response by Dose and Formulation of IFN
Figure 23. End of Treatment Response, Sustained Virological Response, and Week-72 Biochemical Response by Dose and Formulation of IFN
All P values are vs. IFN; * P=0.009 for P-IFN 90 µg vs. IFN; ** P=0.006 P-IFN 180 µg vs. IFN; *** P=0.004 P-IFN 270 µg vs. IFN.

Figure 24. Sustained Virological Response by HCV Genotype and Dose and Formulation of IFN
Figure 24. Sustained Virological Response by HCV Genotype and Dose and Formulation of IFN

The standard interferon arm included more individuals with HCV genotype-1 infections, as well as a higher mean HCV RNA and a slightly larger proportion of participants with bridging fibrosis, which may have contributed to its poorer response rate. In addition, the difference in SVR between the 90 µg arm and the 180 µg arm was relatively narrow. It is unclear whether this may be attributed to a larger proportion of individuals with favorable prognostic factors in the 90 µg arm (genotype non-1 infections, lower baseline HCV RNA levels, and fewer individuals with bridging fibrosis) or because the efficacy of the 90 µg and the 180 µg doses may be roughly equivalent. No further increase in efficacy was observed with the highest dose of pegylated interferon.

Overall, improvements in liver histology (based on paired biopsy samples from a proportion of participants) were similar across groups, but median improvements were greatest in the arm receiving pegylated interferon 180 µg (-3.0). Histological response rates among virological non-responders ranged from 42% to 60% in the pegylated interferon arms vs. 55% in the standard interferon arm.

Table 17. Adverse Events by Dose and Formulation of IFN*
Table 17. Adverse Events by Dose and Formulation of IFN*

* The adverse events listed were seen in at least 10% of study participants.

Table 18. Discontinuations by Dose of and Formulation of IFN
Table 18. Discontinuations by Dose of and Formulation of IFN

The highest-dose (270 µg) arm had a greater incidence of dose modification because of laboratory abnormalities or adverse events than did the 180 µg group (53% vs. 31%). It is unfortunate that the investigators did not consider using a dose of 135 µg. Offering this dose may have resulted in fewer adverse events, dose modifications, and treatment discontinuations while offering efficacy similar to that of the 180 µg dose. Data from a dose-ranging study comparing the efficacy of pegylated interferon alfa-2a 180 µg to 135 µg (using standard interferon as a comparator) found that both doses yielded an SVR of 28% (vs. 11% for standard interferon), although histological improvement occurred more frequently in the 180 µg arm (58% vs. 48%) (Pockros 2001).





This article was provided by Treatment Action Group.
 

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