Interferon is a genetically engineered product originally licensed in 1986 to treat hairy cell leukemia. It is a copy of a protein found naturally in low levels in the human body. (“Recombinant” refers to a technique that takes a DNA molecule from one organism, manipulates it genetically, and puts it into another organism.) It was approved by the US FDA Feb. 25, 1991, to treat hepatitis C. The product, alpha interferon, is the first effective treatment against this form of hepatitis, which affects an estimated 150,000 Americans each year. According to the manufacturer’s (Schering-Plough) literature for using Interferon in the treatment of Hepatitis C: 3 million units per dose, 3 times a week has a sustained response rate of about 12%.
(Note: This FAQ uses “alpha,” although some companies use the term “alfa” with their interferon products, and have them patented this way.)
Besides hairy cell leukemia and hepatitis C, alpha interferon is licensed for treatment of AIDS-related Kaposi’s sarcoma and genital warts.
Treatment: Interferon has been approved for chronic HCV. Patients are selected for therapy on the basis of persistently abnormal liver function (blood) tests, rather than on the presence or absence of symptoms. It’s not known what should be done for patients with mild chronic HCV infection; since some patients with mild disease can go on to develop cirrhosis, therapy with Rebetron (Intron A plus ribavirin) used to be recommended, but Schering’s Pegetron and Roche’s Pegasys (interferon alpha 2a) have now been approved. They have proven to be superior products.
Alpha interferon seems to work better the sooner it is used after infection. However, in many cases of hepatitis C the symptoms get worse again when the treatment is stopped.
Patients with genotype 1 are usually treated for 12 months. Those with other genotypes are treated for only 6 months. The treatment is expensive. Many patients also suffer side effects, such as flu-like symptoms, a reduction in the number of disease fighting white blood cells, and a decreased number of platelets in the blood. Platelets are needed for blood clotting.
Factors most closely associated with response to interferon are: 1) absence of fibrosis or cirrhosis in the pre-treatment liver biopsy; 2) HCV genotype other than 1; 3) lower RNA levels in the blood (e.g., less than 2 million/ml); 4) shorter duration of infection (which often isn’t known).
