This leads to cell death. PKR usually interacts with double strands of DNA and normally regulates transcription at the protein level. In 1989, studies showed effectiveness. The toxicity of ribavirin is high and leads to among other things, hemolytic anemia due to the build up and concentration of red blood cells. IFN is also very poorly tolerated and leads to nausea, vomiting, etc.
Therapy is more effective when a robust immune response to virus is available.
Some hepatitis C patients need constant therapy - when treated, ALT and HCV RNA lowers, but when not treated both rebounds. Even during treatment, some patients do experience a viral breakthrough and the virus flares up. ALT levels could be affected by other viruses or diseases and is not always an HCV marker, but ALT was the only marker available for hepatitis C at the time. A liver biopsy is also taken to visually assess the liver for cell death, necrosis, etc. Understanding the molecular biology of hepatitis C helps lead to better therapies.