A lower dose of PEG-Intron (peginterferon alfa-2b) may be just as effective against hepatitis C virus (HCV) infection as the standard dose of PEG-Intron, according to data announced this week by Schering Plough from their IDEAL study. These results apply only to treatment of HCV in HIV-negative people; low-dose PEG-Intron has not been explored in HIV-positive people, in whom HCV is usually harder to treat.

The IDEAL study randomized 3,070 HIV-negative people with HCV type 1, a hard-to-treat strain of HCV, who had never before been on treatment to one of three groups. One group received the standard dose of PEG-Intron, 1.5 mcg/kg once per week, in combination with Schering Plough’s version of the drug ribavirin, sold as Rebetol. The dose of Rebetol used in this group varied, from 800 to 1,400 mg per day, depending on an individual patient’s weight. The second group received a lower dose of PEG-Intron, 1.0 mcg/kg once per week, also combined with Rebetol based on weight. The third group received Roche’s drug Pegasys (peginterferon alfa-2a) at 180 mcg per week, combined with their version of ribavirin, sold as Copegus, at a dose of either 1,000 or 1,200 mg per day, depending on body weight. All three groups took their treatment regimen for 48 weeks.

The effectiveness of the three different regimens was based on how many people maintained an undetectable HCV viral load for at least six months following the end of their course of treatment, also known as a sustained viral response (SVR).

Based on the results announced by Schering Plough, 40 percent of people who received the standard dose of PEG-Intron plus Rebetol achieved an SVR. This compared with 38 percent of people on the lower dose PEG-Intron plus Rebetol, and 41 percent of people on Pegasys plus Copegas achieving an SVR.

The percentage of people who discontinued treatment due to side effects was also similar among the three groups, with a small advantage in favor of low-dose PEG-Intron. Among those receiving low-dose PEG-Intron, 10 percent discontinued treatment, compared with 13 percent in the higher-dose PEG-Intron and Pegasys groups.

Some media stories have reported that these data, which also gave the number of people whose HCV viral load came back after stopping treatment—called a relapse—prove that both low- and high-dose PEG-Intron were superior to Pegasys. Approximately 32 percent of people on the Pegasys combination experienced a relapse, compared with 24 percent of those receiving standard-dose PEG-Intron and 20 percent receiving low-dose PEG-Intron.

Based on the study design, however, it is not possible to compare PEG-Intron, at either dose, head to head with Pegasys. Writing in the January–March issue of Liver Health Today, Douglas Dieterich, MD, a professor of medicine at Mount Sinai Center in New York and a liver expert, writes, “[This] study enters dangerous territory with the addition of a third group of patients, which is intended to settle the question of which of two competing interferons—Peg-Intron or Pegasys—is ‘better.’ Although touted by the sponsoring company, Schering-Plough, as a head-to-head trial, this is really a misnomer.  IDEAL can't determine which drug is better because patients in the Pegasys (produced by Roche) arm receive a different ribavirin regimen than those in the Peg-Intron arm.  Not only do they receive a different starting dose of ribavirin, but the way ribavirin doses are reduced in the event a patient has side effects is also different.”