PI Perspective 33: New Peg-interferon Results

Important note: Information in this article was accurate in August, 2001. The state of the art may have changed since the publication date.

New Peg-interferon Results

Project Inform Perspectives 33 - August, 2001

Encouraging results were recently presented of the pegylated interferon products used in the treatment of hepatitis C (HCV). Pegylated interferon is a form of interferon to which polyethylene glycol (PEG) has been added. Adding PEG stabilizes interferon in the body and helps sustain a more even and long lasting level of the drug. The studies show that this new formulation, when used in combination with ribavirin (Rebetol) is more effective in treating HCV than the standard regimen of regular interferon-alfa combined with ribavirin (Rebetron).

One study showed that about 35% of people who did not benefit from standard Rebetron as first line therapy achieved a virologic response (a reduction in HCV RNA levels) with the combination of peg-interferon alfa-2b (peg-Intron, developed by Schering Plough) and ribavirin after 24 weeks of therapy. Although the preliminary results are encouraging, the usefulness of this combination as second line therapy will not be known until the study is completed.

Another study showed that 61% of the participants, who had not previously received anti-HCV therapy, had a sustained virologic response after 72 weeks of the peg Intron/ribavirin study. More specifically, 48% of people with genotype 1 (the most difficult type of HCV to treat) and 88% of people with genotypes 2 or 3 had a sustained response. The dose of peg-Intron used was 1.5mcg/kg once a week in combination with at least 10.6 mg/kg of ribavirin daily. This represents a very significant improvement in therapy for almost all HCV-infected people.

Peg-Intron is approved by the FDA (Food and Drug Administration) to treat HCV when used alone, but not in combination with ribavirin. It is only modestly effective when used alone. However, the result from the second study supports the use of the combination, for which it is likely to be approved soon.

Results from a study of a different pegylated interferon (Pegasys, developed by Hoffman-La Roche) are also encouraging. This study included 1,121 people who had not previously taken anti-HCV therapies and received the standard interferon/ribavirin combination (Rebetron), Pegasys alone or Pegasys in combination with ribavirin. The dose of Pegasys in this study was 180mcg once a week and the dose of ribavirin was 1,000-1,200mg daily. At the end of the 72-week study the percentage of people with HCV levels below 50 copies/mL were:

	Pegasys alone	Rebetron	Pegasys + ribavirin
Overall Response	30%	45%	56%
Response for genotype 1	21%	37%	46%
Response for genotype 2 or 3	45%	61%	76%

Further analysis of this study found that people who did not have a response by week 12 were highly unlikely to achieve undetectable HCV levels by the end of the study. Additionally, people who were over 80% adherent to their medications were significantly more likely to achieve undetectable HCV levels at study end. Side effects overall were similar between the three groups, although there appeared to be less severe flu-like symptoms and depression among people receiving Pegasys and ribavirin than those on Rebetron.

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