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PegIntron is a long acting form of interferon that has been available since January 2001. When combined with ribavirin it gives essentially identical results as Pegasys plus ribavirin. It has more severe side effects, and my patients prefer to take Pegasys. One particularly severe adverse reaction that is common with PegIntron and rare with Pegasys is fat necrosis injection reaction. Some of my patients have required surgical removal of several inches of skin and subcutaneous fat because of PegIntron injections. We still use PegIntron in cirrhotic patients who fail Pegasys and Infergen, with a treatment response rate of about 5%. It is a third line drug for us. Infergen also can cause fat necrosis. Pegasys has the interferon tightly bound to polyethylene glycol and this must reduce the irritation to the skin and fat. When Schering designed and executed their PegIntron plus ribavirin registration trial they chose a ribavirin dose of 800 mg per day. They could have used their previous 1,000/1,200 mg dose but they did not. After the study was completed, they decided that higher doses of ribavirin would be better. The registration trial with PegIntron plus ribavirin in genotype one patients with high viral level had poor results. Only 30% had a sustained viral response which was not better than the older Rebetron treatment (29%). This is the largest group of American patients with HCV and 30% is a disappointing number. Dr. Ira Jacobson designed and Schering executed a very large trial that compared the 800 mg ribavirin dose to a higher weight based dose. The higher ribavirin dose group had 3-5% higher sustained response rate than the flat 800 mg dose group. Genotype one patients with either high or low viral level had 34% sustained response rate with the higher ribavirin dose and 29% with the 800 mg dose. These are disappointing success rates. African American patients and heavy patients were the subgroups who benefited the most from the higher ribavirin dose.
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