There are over 170 million people worldwide infected with the hepatitis C virus. Chronic carriers are at risk of developing liver cirrhosis and/or liver cancer. In the United States, nearly 4 million people are infected with HCV, resulting in 10,000 to 12,000 deaths annually. The number of people diagnosed with chronic HCV is expected to increase fourfold from 1990 to 2015. It is predicted that deaths from HCV will surpass those of AIDS in the United States by 2010, at which time the global HCV market is forecasted to be approximately $6 billion.

In the United States, monotherapy with interferon-alpha and combination therapy with interferon-alpha and the ribonucleoside analog ribavirin are the two different regimens currently approved as therapy for chronic hepatitis C. Treatment with interferon-alpha alone or combination with ribavirin has limited effectiveness. The use of interferon-based therapy for the treatment of HCV can be further limited by frequent side effects, injectable administration and poor patient tolerance and adherence. Many patients receiving interferon can experience influenza-like symptoms, fatigue and depression. Ribavirin can be problematic for patients with pre-existing anemia, kidney problems or heart disease.