Taribavirin

Taribavirin (1-b-D-ribofuranosyl-1H-1, 2, 4-triazole-3-carboxamidine) is a synthetic nucleoside (guanosine) analog under development for the treatment of patients with chronic hepatitis C. After oral administration, taribavirin is rapidly absorbed, after which it is readily and extensively taken up by the liver and converted into its active metabolite, ribavirin. As a result, this reduces exposure to red blood cells (RBCs) and increases exposure to the liver, the site of HCV replication.

The introduction of ribavirin accounted for the greatest incremental advance in the treatment of HCV. The combination of ribavirin and peginterferon alfa is currently the standard treatment for chronic hepatitis C. Although this combination treatment is effective in achieving sustained viral responses (SVR) in more than fifty percent of hepatitis C patients, it can be associated with dose-limiting anemia. Adherence to therapy has been shown to play a major role in achieving a sustained viral response (SVR), and hemolytic anemia caused by the accumulation of ribavirin in red blood cells substantially undermines adherence. Most patients started on ribavirin therapy experience a rapid 2-3 g/dL decline in circulating hemoglobin levels during the first four weeks of therapy, and roughly 20-30 percent of patients on combination therapy develop anemia (<10 g/dL). Anemia often prompts ribavirin dose reduction or discontinuation, which may be associated with lower SVRs.