C 型 肝炎ウイルスの抗ウイルス療法

Abstract

Hepatitis C virus (HCV) is a major cause of chronic hepatitis, liver cirrhosis and liver cancer. Previously, the consensus strategy against HCV infection was interferon mono-therapy. Now, pegylated interferon (PEG-IFN) with ribavirin combination therapy for 24-48 weeks is used against chronic hepatitis C and can achieve a sustained viral response (SVR) in about 50% of patients with genotype 1b and high viral loads. The number of elderly Japanese patients with chronic hepatitis C has increased compared to that in western countries. The efficacy of IFN therapy for elderly patients with genotype 1 and high viral titers is lower than in young patients, because the side effects of combination therapy with PEG-IFN and ribavirin are pronounced with a reduction in blood count. To avoid discontinuation of therapy and overcome the low SVR in elderly patients, ribavirin dosing, based on the total clearance of ribavirin (CL/F), may be considered to be increasingly valuable. Approximately 25% of HCV carriers have normal ranges of serum alanine amino transferase (ALT). The rate of SVR in patients with persistently normal serum ALT (PNALT) is almost as same as that in HCV carriers, in terms of IFN therapy. This evidence suggests that patients with PNALT should be considered for IFN therapy. Novel treatment options currently in development are focused on inhibition of HCV-specific enzymes, NS3 protease and NS5B polymerase, and several drugs have entered clinical trials. Now, patients with HCV and liver cirrhosis can be given IFN therapy, except in the case of genotype 1b and high viral loads. This therapy should contribute to an improvement in the prognosis. It would appears that interferon will remain an element of anti-HCV therapy for the immediate future, although new regimens will be necessary for advanced combination therapy. It is hoped that new forms of interferon that are more effective, less toxic, and more convenient can be developed.