A study that tested a combination of drugs to treat African-American patients infected with the most common form of hepatitis C in the United States, genotype 1, has generated a higher drug response rate than has ever been observed in this population. The multi-center study, which included patients at the University of Maryland Medical Center, found that 26 percent of African Americans in the study with genotype 1 hepatitis C responded to the therapy. This is an improvement over previously reported response rates of 17 percent to 20 percent from smaller, retrospective studies. The results of the study are published in the June issue of Hepatology, the official journal of the American Association for the Study of Liver Diseases.
"Black Americans have been underrepresented in clinical trials testing the effectiveness of antiviral therapy to treat hepatitis C," says Charles D. Howell, M.D., associate professor of medicine at the University of Maryland School of Medicine and a co-author of the study. "Yet hepatitis C is two to three times more common among black Americans than among white Americans."
Hepatitis C, a viral infection carried in the blood, attacks the liver and kills 8,000 to 10,000 people a year. While there are preventive vaccines for hepatitis A and B, no vaccine exists for hepatitis C.
The study, conducted at 11 centers, enrolled a sufficient number of black patients to ensure statistically reliable findings, along with a small number of white patients as a reference group. A total of 78 black patients and 28 white patients were given a combination of two drugs, peginterferon alfa-2a plus ribavirin, for 48 weeks, and then monitored for an additional 24 weeks.
In order to measure the therapy's effectiveness, the researchers looked at the proportion of patients with a sustained virological response, defined as an undetectable level of the hepatitis C virus in the patient's blood after the 24-week follow-up period.
An analysis revealed that 20 of the black patients (26 percent) and 11 of the white patients (39 percent) had achieved the sustained virological response by week 72. Virological response rates in both groups peaked at week 24, although the response was lower in the black group than in the white group at all study visits.
Dr. Howell says the finding of a lower response rate in blacks compared to whites is consistent with previous findings. He says, "It has been known for about six years that there is a difference in response rates between whites and African Americans. What we don't know is why the difference exists."
The study concludes that peginterferon alfa-2a combined with ribavirin is safe. Dr. Howell says that in some cases, blacks seemed to tolerate the therapy better than whites. Further, he says that some blacks whose hepatitis C virus levels remained at a detectable level did show improvement in liver biopsy findings. "This suggests that there may be a potential benefit even for patients who do not develop a sustained virological response," says Dr. Howell, "However, this question requires further study."
Response rates to hepatitis C therapies have been increasing ever since interferon was first used as a treatment in the early 1990s, according to Dr. Howell. Interferon is a protein produced in the body that fights viruses by boosting the immune system. Alpha interferon is a genetically engineered form of the protein that mimics the activity of the naturally occurring protein. In the beginning of interferon studies, about 5 percent of whites with genotype 1 hepatitis C responded to the therapy, but less than 2 percent of blacks responded.
"Today, a process called pegylation keeps interferon active in the body longer," says Dr. Howell. "And pegylated interferon combined with ribavirin is a kind of one-two punch against hepatitis C." But he adds, "In absolute terms, the response rate is lower for African Americans."
Dr. Howell is an investigator in another study that is still underway, the NIH VIRAHEP-C study, designed to determine why there is a difference in treatment response rates between African Americans and whites.
Other researchers in the current study include: Lennox Jeffers, M.D., Miami VA Medical Center; William Cassidy, M.D., Louisiana State University Health Sciences Center; Sylvia Hu, Roche Laboratories, Inc., Nutley, NJ; and K. Rajender Reddy, M.D., University of Pennsylvania.
Funding for the study came from Roche Laboratories, Inc.
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