BOSTON, Nov. 1 /PRNewswire-FirstCall/ -- Schering-Plough Corporation (NYSE:SGP) today reported two data presentations supporting response guided therapy with boceprevir combination therapy in patients with chronic hepatitis C virus (HCV) genotype 1. These retrospective analyses were presented at the American Association for the Study of Liver Diseases (AASLD) Annual Meeting in Boston, Oct. 30-Nov. 3. Boceprevir is an investigational HCV protease inhibitor. Phase III registration studies with boceprevir in treatment-naïve HCV patients and patients who failed prior treatment have been fully enrolled and are expected to be completed in mid-2010. Boceprevir response guided therapy utilizes a unique 4-week lead-in of PEGINTRON(R) (peginterferon alfa-2b) and REBETOL(R) (ribavirin, USP) prior to the addition of boceprevir (800 mg TID) for an additional 24-44 weeks. Response guided therapy is intended to enable the physician to determine the duration of boceprevir combination therapy based on a patient's viral response during treatment. Although baseline characteristics cannot predict which patients may benefit from longer therapy, in-treatment virologic responses appear likely to do so. The lead-in strategy allows for an assessment to define a patient's response to peginterferon and ribavirin alone in this initial 4-week treatment period. Boceprevir Response Guided Therapy in Null Responder Patients The boceprevir Phase II HCV SPRINT-1 study in treatment-naïve patients with HCV genotype 1 had two treatment arms in which patients received a 4-week lead-in followed by the addition of boceprevir for an additional 24 or 44 weeks (n=206). In an oral presentation at AASLD,(1) researchers analyzed results from these two arms to determine SVR rates in patients who had a null response to peginterferon and ribavirin therapy (defined as