Interferon alfa 2a versus Interferon alfa 2b

[MissyMouse]

August 26, 2008 Printer-friendly version 

Hep C Treatment: Comparing the Pegylated Interferons
Learn about the facts on pegylated interferon alfa-2a and pegylated interferon alfa-2b, the standard treatment for chronic Hepatitis C. Comparing and contrasting the pegylated interferons may help better explain a physician’s preference or indifference between the two when treating his or her Hepatitis C patients.

by Nicole Cutler, L.Ac.

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:

1. 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.

2. 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.

3. 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.

4. 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.

5. 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.

[Pancho and Lefty]

Mouse,

The thing I got from reading about the studies was that Schering/P and Roche both want to design a trial that sheds doubt on the efficacy of their competitor's product. With all the money at stake . . . I really doubt an objective comparison will ever be made.

Some heppers are passing around info about the differences in half life between the two. Pegasus (Roche) is said to stay in the system longer.

The Univ or Utah Hospital directed me to Roche. I've always wondered why they thought it would be best for me.

Peace,

Max

[DougV]

Something else to toss out.......

Pegintron tends to be favored for larger people due to the one size fits all approach of pegasys.  Large people as a group probably do not respond to treatment as well as others.  Could be Pegintron is being "penalized" in some studies due to the physical characteristics of the participants. 

And of course don't forget the more even blood serum level of daily injections so just to keep things even more confusing, let's toss in my old favorite Infergen, which didn't even get an honorable mention.

I think the pharmacutical companies are simply hiding the ultimate, the chocolate chip cookie treatment plan for HCV.  'cause after all they don't want the financial gains going to the eggs, milk, and chocolate chip folks.

Doug

[emkins1]

Doug,

Thanks for giving Infergen an honorable mention because it did the trick for me after slogging away at Schering Plough's product twice.

Em

[Snowflake]

Hello,

It been awhile since i read up on the therapies, so i may be alittle off on my numbers. But, the reason i used
the pegylated interferon alfa-2a (Pegasys). Was it had more receptors, like 16, compared to the other at 6.
At the time of TX i started at 96lbs and did fine thoughout treatment. I was alittle worried it being a full 180mg dose. But, i finally reached one full year SVR this July... after falling out of SVR at the first year mark...

TAKE CARE
 Winona

[robin]

How great to read your post, Winona. I think I posted my congrats to you when you got your one year SVR result but I'd like to say again...how great and congrats. Keep your spirits high...robin