African Americans and Hepatitis C: background on Schering controversy

We'll be providing some additional context and perspectives on the controversy surrounding Schering-Plough's initial exclusion of African Americans from its phase II study of SCH 503034, a new hepatitis C protease inhibitor (see previous post).  Today, here's some background on African Americans and hepatitis C, focusing on epidemiology and response to treatment.

What do we know about African Americans and hepatitis C?

Epidemiology: African Americans have a higher rate of hepatitis C than other racial/ethnic groups – 3.0% of African Americans have been infected with hepatitis C, twice as high as the rate among whites.  Hepatitis C prevalence is highest among black males ages 45-49: an alarming 17.9% have been infected, according to statistics from the Centers for Disease Control and Prevention (CDC), a federal agency.  Though African Americans make up roughly 12% of the U.S. population, they account for an estimated 22% of all people with chronic hepatitis C in the country.

Treatment: Hepatitis C treatment is much less effective in African Americans compared to other racial/ethnic groups.  Part of the decreased success of treatment is linked to genotype – among people with chronic hepatitis C, roughly 90% of African Americans have genotype 1, the strain of hepatitis C least responsive to interferon-based treatment, compared to about 70% of whites.  However, even among people with genotype 1, African Americans are less likely to respond to treatment than whites.

Initial studies of pegylated interferon/ribavirin treatment did not enroll enough African Americans to draw meaningful conclusions about difference in response by race/ethnicity.  However, three major trials specifically designed to compare treatment responses between whites and African Americans confirmed that treatment success rates* were about twice as high in whites (39-52%) vs. African Americans (19-26%), even when all study participants had genotype 1.

The reasons for African Americans’ decreased responsiveness to interferon-based treatment remain under investigation.  Speculation centers on possible genetic differences that influence immune responses, since interferon is believed to operate in part by strengthening the immune system’s ability to fight hepatitis C.  Some differences between whites and African Americans in patterns of immune response to hepatitis C have been described, though their relevance to treatment outcomes is not clear.

* Treatment success is defined as a sustained virologic response (SVR) – when hepatitis C remains undetectable 6 months after the end of treatment.

For references, click on the link below.