Recent advances in the treatment of hepatitis C virus infection for special populations and remaining problems.

Hepatitis C virus (HCV) infection is one of the primary causes of liver cirrhosis, hepatocellular carcinoma (HCC), and liver transplantation (LT). The rate of HCV infection is high in patients on hemodialysis and in patients infected with human immunodeficiency virus (HIV). In liver transplant patients with HCV infection, recurrent HCV infection of the transplanted liver is universal and results in rapid liver fibrosis progression. In patients with HCV/HIV coinfection as well, liver fibrosis advances rapidly. Thus, there is an urgent need for prompt HCV infection treatment in these special populations (i.e. HIV/HCV coinfection, HCV infection after LT, and dialysis patients). Interferon (IFN)-based therapy for HCV infection could not achieve a high rate of sustained viral response and could cause severe adverse events in the aforementioned special populations. Direct-acting antivirals (DAAs) have recently been developed, and clinical trials have shown that IFN-free DAA-based therapies are associated with a significantly better safety and therapeutic profile than IFN-based therapies. However, the majority of the initial DAA trials excluded special populations; thus, the efficacy and safety of IFN-free DAA-based therapy in special populations remained to be clearly established. Although recent clinical trials and clinical studies have shown the high efficacy and safety of this therapy even in special populations, several unresolved problems, including emergence of resistance-associated variants after failure to respond to DAAs and HCC occurrence after DAA therapy, still exist. Hence, in this review, we discuss the recent advances in anti-HCV therapy for special populations and the remaining problems regarding this therapy.