Abacavir associated with a poorer response to HCV therapy

HIV/hepatitis C coinfected patients who take abacavir (Ziagen) may be less likely to achieve a sustained virological response to anti-hepatitis C therapy, according to Spanish research presented to the Third International Workshop of HIV and Hepatitis Coinfection in Paris on June 8^th.

The investigators found that patients taking abacavir had lower levels of ribavirin and speculate that the poor hepatitis C treatment outcome could be related to an intracellular interaction between the two drugs.

Investigators in Spain conducted a multicentre, retrospective study including all chronically coinfected patients who started anti-hepatitis C therapy with pegylated interferon and ribavirin between 2002 and 2005.

Data were available on 426 patients. Mean age was 41 years and 81% were taking potent anti-HIV therapy. The harder-to-treat hepatitis C genotypes 1 and 4 were present in 65% of patients and 40% had advanced fibrosis.

A total of 38% of patients achieved a sustained virological response. Factors associated with a poorer treatment outcome in univariate analysis were genotypes 1 and 4 (p = 0.04), higher baseline hepatitis C viral load (p = 0.04), low ribavirin plasma levels at week four (p = 0.03), and taking anti-HIV therapy including AZT (p = 0.03), or abacavir (p = 0.004).

In subsequent multivariate analysis, lack of treatment response was associated with higher hepatitis C viral load at baseline (p

But when the investigators looked at treatment response according to ribavirin levels, abacavir use ceased to be a significant predictor of poor treatment outcome.

The investigators therefore suspect that an intercellular interaction between ribavirin and abacavir could explain their initial results and recommend that patients taking both abacavir and ribavirin should have their levels of ribavirin closely monitored with doses of the drug increased if necessary.