Hepatitis C genotype 6: A concise review and response-guided therapy proposal.

Hepatitis C genotype 6 is endemic in Southeast Asia [prevalence varies between 10%-60% among all hepatitis C virus (HCV) infection], as well as also sporadically reported outside the area among immigrations. The diagnosis of HCV genotype can be inaccurate with earlier methods of genotyping due to identical 5'-UTR between genotype 6 and 1b, hence the newer genotyping methods with core sequencing are preferred. Risk factors and clinical course of HCV genotype 6 do not differ considerably from other genotypes. Treatment outcome of HCV genotype 6 with a combination of pegylated interferon and ribavirin is superior to genotype 1, and nearly comparable to genotype 3, with expected sustained virological response (SVR) rates of 60%-90%. Emerging data suggests that a shorter course 24-wk treatment is equally effective as a standard 48-wk treatment, particularly for those patients who attained undetectable HCV RNA at week 4 (RVR). In addition, baseline and on-treatment predictors of response used for other HCV genotypes appear effective with genotype 6. Although some pan-genotypic direct-acting antivirals have completed phase II/III studies (sofosbuvir and simeprevir) with clinical benefit demonstrated in small number of patients with genotype 6, broad availability of these agents in Southeast Asia may not be expected in the near future. While awaiting the newer therapy, response-guided therapy seems appropriate for patients with HCV genotype 6. Patients with RVR (representing > 70% of patients) are suitable for 24-wk treatment with expected SVR rates > 80%. Patients without RVR and/or those with poor response predictors may benefit from 48 wk of therapy, and a detectable HCV RNA at week 12 (with no early virological response) serves as a stopping rule. This treatment scheme is likely to have a major economic impact on HCV therapy, particularly in Southeast Asia, wherein treatment can be truncated securely in the majority of patients with HCV genotype 6.