Pegylated Interferon

Pegylated Interferon

Anyone would prefer to take a drug just once a week, as opposed to three times a week or daily. Pegylation is a process that involves attaching a large substance - known as polyethylene glycol (PEG) to a protein. In the case pegylated-interferon (PEG-interferon) PEG is attached to interferon. This enables it to stay in the body longer. By using the process of pegylation, the frequency with which interferon is required to be injected is reduced from the three times per week to once per week. Since pegylated interferon stays in the body longer, than regular interferon, the hepatitis C virus is suppressed longer than with regular interferon. This results in improved response rates – that is, long-term eradication of HCV occurs more frequently than with standard interferon.

Two pegylated interferons are currently FDA approved- PEG-Intron (pegylated interferon alfa 2b) and PEGASYS (pegylated interferon alfa 2a). PEG-Intron is manufactured by Schering-Plough and was FDA approved in January 2001. The dose of PEG-Intron is determined by a patient’s weight. Weekly dosages typically range from 100-150 micrograms. The medication is administered once a week via injection. In October 2003, The FDA approved the first ever pen delivery system for administration of PEG-Intron. It is known as the REDIPEN. This disposable single-dose delivery system is much easier to use, and is more convenient, than the former administration technique (which involved mixing a specific dose of saline (sterile water) with a specific dose of PEG-Intron via the traditional vial and syringe method). PEGASYS is manufactured by Hoffman-La Roche and was FDA approved in October 2002. The weekly dose of PEGASYS is 180 micrograms and is independent of a person’s weight. Long-term response rates are similar for the two types of pegylated interferon.

The two types of peginterferon differ in the type of PEG molecule that is attached to interferon. PEG-Intron uses a straight small molecule of PEG, while PEGASYS uses a large rounded molecule of PEG. However, results appear to be similar for the two types of pegylated interferon. Approximately 24 percent of treatment-naive people who take either form of pegylated interferon for a period of 48 weeks demonstrate sustained virological response- that is, their HCVRNA is nondetectable (less than 50 IU/mL) six months after completion of therapy.

Studies are currently being conducted on pegylated-Infergen (consensus interferon) a product manufactured by Intermune.

Pegylated Interferon in Combination with Ribavirin

In August 2001, PEG-Intron was FDA approved for use in combination with ribavirin (ribavirin is marketed by Schering-Plough under the name Rebetol). In December 2002, PEGASYS was approved by the FDA to be taken in combination with ribavirin (ribavirin is marketed by Roche under the name Copegus). Combination therapy with peginterferon and ribavirin is the most effective treatment for patients with chronic hepatitis C. Long-term response rates appear to be similar for the two combinations of pegylated interferon and ribavirin. Schering-Plough has initiated a study aimed at comparing the efficacy and safety of the Peg-Intron’s individualized weight-based dosing versus flat (that is, non-weight-based) dosing of Pegasys. The results of this trial, named the IDEAL trial are eagerly anticipated.

Long-term sustained response occurs in approximately 54-56 percent of people who take either form of pegylated interferon combined with ribavirin for 48 weeks. Response rates, dosage of ribavirin and length of therapy vary with HCV genotype as follows:

Genotype 1. Sustained response in people with genotype 1 ranges from 42-44 percent. Treatment should last for 48 weeks, using ribavirin at a daily dose of 1000-1200mg.

Genotypes 2 and 3. Sustained response in people with genotype 2 and 3 ranges from 78-80 percent. Treatment should last at least 24 weeks. However, people who have severe scarring or cirrhosis (as per liver biopsy specimens) should be treated for 48 weeks. A daily dosage of 800mg ribavirin may be used.

Genotype 4, 5, and 6. Studies on people with genotypes 4,5, and 6 are limited. However, it appears that response rates are similar to those with genotype 1. Therefore 48 weeks of therapy using ribavirin at a daily dose of 1000-1200mg is recommended.

Melissa Palmer, MD is the author of " Dr. Melissa Palmer's Guide of Hepatitis and Liver Disease". (Published 2004. Penguin Putnam).

The office of Melissa Palmer, M.D. is located at:

1097 Old Country Road Suite 104

Plainview, N.Y 11803

To arrange an appointment with Dr. Palmer, call

(516) 939-2626

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