Hep C Treatment: Comparing the Pegylated Interferons
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Today’s standard treatment for chronic Hepatitis C is a combination of pegylated interferon and ribavirin. While the prescription might seem straightforward, there are actually two different kinds of pegylated interferon – pegylated interferon alfa-2a and pegylated interferon alfa-2b. A general review of their differences and what experts say about their comparison will help those with chronic Hepatitis C better understand the pegylated interferon debate.
What is Pegylated Interferon?
By attaching a protective barrier called polyethylene glycol (PEG) to interferon, pegylated interferon can survive in the body longer than the un-pegylated form, thus reducing dosing frequency. While regular interferon is injected three times a week, pegylated interferon is generally taken once a week. There are two types of pegylated interferons – peg-interferon alfa-2a and alfa-2b. The major difference between the two is how they are dosed:
- 2a – The dose of pegylated interferon alfa-2a (Pegasys) is the same for all patients, regardless of weight or size.
- 2b – The dosing of pegylated interferon alfa-2b (PegIntron) is based on an individual’s weight.
Which Pegylated Interferon is Better?
While there is no other currently approved therapy for chronic Hepatitis C, there is uncertainty among doctors, scientists and patients as to which pegylated interferon is supreme. An overview of the studies evaluating the pegylated interferons has provided conflicting results:
- In the August 2006 Journal of Hepatology, a small Argentine study compared the pharmacokinetics, pharmacodynamics, and antiviral activity of Pegasys and PegIntron in participants with chronic Hepatitis C genotype 1. The researchers found that patients receiving PegIntron had greater decreases in HCV viral load after eight weeks of therapy, despite lower levels of interferon in the blood of these participants. Interestingly, this trial was sponsored by Schering-Plough, the manufacturer of PegIntron.
- At the 38th annual Digestive Disease Week in May 2007, Roche announced results of a small study demonstrating that all patients who discontinued treatment with PegIntron and ribavirin due to adverse events within the first 12 weeks were able to complete 12 weeks of treatment with Pegasys and ribavirin. The researchers concluded that Pegasys may be an option for those who are unable to tolerate the side effects of PegIntron.
- Three studies presented at the 43rd European Association for the Study of Liver Diseases (EASL) held in Milan, Italy in April of 2008 showed that Pegasys had a better cure rate for Hepatitis C than PegIntron. The results of two Italian and one German trial demonstrated that when the dosage of ribavirin was kept at a constant, the cure rate for Hepatitis C was greater in those treated with Pegasys than Pegintron.
- Also presented at the 43rd EASL were the results of the IDEAL (Individualized Dosing Efficacy vs. flat dosing to assess optimal pegylated interferon therapy) trial sponsored by Schering-Plough. Over 3,000 participants with Hepatitis C genotype 1 were recruited. While relapse after the end of treatment was lower for participants receiving PegIntron, the end of treatment response was higher with participants taking Pegasys. In total, the IDEAL results demonstrated a similar sustained virologic response, safety and tolerability between the two pegylated interferons. This study is being criticized by experts because those receiving Pegasys received a different starting dose of ribavirin than those on PegIntron. In addition, ribavirin dose reduction protocol for side effects was not uniformly administered between these two treatment arms.
- Published in the August 8, 2006 issue of the Journal of Viral Hepatitis, researchers from Oregon performed an adjusted indirect analysis of trials comparing dual therapy with Pegasys or PegIntron versus dual therapy with non-pegylated interferon. After analyzing 16 trials for sustained virological response and withdrawal due to side effect rates, no statistically significant differences between dual therapy with pegylated interferon alfa-2a and dual therapy with pegylated interferon alfa-2b were found. Despite their apparent similarity, the study authors stated, “Because estimates are imprecise, our results also do not rule out a clinically significant difference. Head-to-head trials are needed to verify the results of indirect analyses and provide additional guidance on optimal treatment choices.”
While logic might lead one to assume that a dosage customized for each individual would deliver safer and more effective results, the data does not completely support this view. The conflicting evidence already in existence clearly indicates that more adequately funded, large, impartial, well-designed studies comparing the two pegylated interferons are needed. Since the differences between Pegasys and PegIntron appear to be negligible, those doing combination therapy for the first time have little reason to be concerned about which pegylated interferon their physician has prescribed.
References:
http://www.bio-medicine.org/medicine-technology/Data-Suggest-that-
Pegasys-May-be-an-Option-in-Hepatitis-C-Patients-0AUnable-to-Tolerate
-Peg-Intron-700-1/, Data Suggest that Pegasys May be an Option in Hepatitis C Patients Unable to Tolerate Peg-Intron, Retrieved August 17, 2008, Bio-Medicine, May 2007.
http://www.hivandhepatitis.com/hep_c/news/2008/071808_a.html, Comparison of the Pegylated Interferons Pegasys and PegIntron for Treatment of Chronic Hepatitis C: Analysis of 16 Randomized Trials, Retrieved August 16, 2008, hivandhepatitis.com, July 2008.
http://www.hivandhepatitis.com/2006roberts/hcv/080906_c.html, Comparison of Pegasys vs Peg-Intron for Treatment of Chronic Hepatitis C, Liz Highleyman, Retrieved August 16, 2008, hivandhepatitis.com, August 2006.
http://www.medicalnewstoday.com/articles/105492.php, Final Results Of Ideal Study Presented At Annual Meeting Of The European Association For The Study Of The Liver (EASL), Retrieved August 16, 2008, MediLexicon International Ltd., April 2008.
http://www.natap.org/2008/HCV/011408_02.htm, IDEAL Study COMMENTARY- Doug Dieterich MD A Healthy Dose of Curiosity Clinical trial results require careful interpretation, Douglas T. Dieterich, MD, Retrieved August 16, 2008, Liver Health Today, January-March 2008.
http://www.ncbi.nlm.nih.gov/pubmed/18482285, Pegylated interferons for chronic hepatitis C virus infection: an indirect analysis of randomized trials, Chou R, et al, Retrieved August 16, 2008, Journal of Viral Hepatitis, August 2008.
http://www.pegasys.com/about-pegasys/what-is-pegasys.aspx, What is Pegasys?, Retrieved August 16, 2008, Hoffman-La Roche Inc., 2008.
http://www.roche.com/inv-update-2008-04-28c, Investor Update, Retrieved August 17, 2008, F. Hoffman-La Roche, April 2008.
http://www.thebody.com/content/art5176.html, HCV Treatment and Monitoring Guide, Retrieved August 16, 2008, The Body, August 2003.
