Although the addition of the HCV NS3/4A protease inhibitors boceprevir and telaprevir to pegylated interferon ( peginterferon ) alfa plus ribavirin has improved sustained virological response ( SVR ) in treatment-naive and treatment-experienced patients infected with hepatitis C virus ( HCV ) genotype 1 , the regimens have a high pill burden and are associated with increased rates and severity of adverse events , such as anaemia and rash .