PEG-interferon alpha (PEG-IFN 2a and 2b, or PEG-IFN alpha), in combination with ribavirin, is used to treat Hepatitis C Virus (HCV) infection. IFNL3 (also known as IL28B) is a member of the type 3 IFN-alpha family, which are induced by viruses and inhibit HCV replication in vitro. Genetic variants in IFNL3 are associated with increased response (higher sustained virological response rate) to PEG-interferon alpha/ribavirin combination therapy and clearance of HCV. In 2011, the protease inhibitors boceprevir and telaprevir were approved to treat HCV genotype 1 infection in many countries, including the United States and those in the European Union, and are now included in HCV combination therapy. IFNL3 genotype predicts response to this combination therapy and also predicts eligibility for shorter duration of therapy. Guidelines regarding the clinical use of PEG-interferon alpha containing regimens based on IFNL3 genotype have been published in Clinical Pharmacology and Therapeutics by the Clinical Pharmacogenetics Implementation Consortium (CPIC) and are available on the PharmGKB website. [from
PharmGKB]