Schering-Plough Completes Enrollment of Boceprevir Registration Studies in Treatment-naive and Treatment-experienced HCV Patients

Kenilworth, NJ -- January 27, 2009 -- Schering-Plough Corporation (NYSE: SGP) today reported that it has completed patient enrollment in the boceprevir HCV SPRINT-2 study, a pivotal Phase III study in treatment-naive patients. Together with the HCV RESPOND-2 study, a pivotal Phase III study in patients who failed prior treatment that completed enrollment in November 2008, the company has fully enrolled its registration studies for boceprevir, its lead investigational oral hepatitis C protease inhibitor. A total of more than 1,500 patients were enrolled in these studies at U.S. and international sites.

"We believe boceprevir has the potential to be a first-in-class and best-in-class protease inhibitor for treating chronic hepatitis C," said Thomas P. Koestler, PhD, executive vice president and president, Schering-Plough Research Institute. "We are very encouraged by the boceprevir study results reported to date and look forward to the completion of these registration studies." The company expects to complete the studies in mid-2010.

Schering-Plough previously reported Phase II study results from Part I of the HCV SPRINT-1 study in 595 treatment-naive patients with chronic hepatitis C virus (HCV) genotype 1. In that study, a 48-week boceprevir regimen achieved a 75 percent SVR [sustained virological response] rate in patients who received 4 weeks of PegIntron (peginterferon alfa-2b) and Rebetol (ribavirin, USP) prior to the addition of boceprevir (P/R lead-in, n=103). This represents a near doubling of the 38 percent SVR rate for patients in the control group receiving 48-weeks of PegIntron and Rebetol alone (n=104) (ITT). In a 28-week boceprevir P/R lead-in regimen, the SVR rate was 56 percent (n=103). Importantly, for patients who received the boceprevir P/R lead-in regimen and had rapid virologic response (RVR), defined as undetectable virus (HCV-RNA) in plasma after 4 weeks of boceprevir treatment, SVR was 94 percent in the 48 week regimen (n=66) and 82 percent in the 28-week regimen (n=66). RVR has been shown to be a reliable predictor for achieving SVR.

Treatment discontinuations for boceprevir patients due to viral breakthrough were fewer in the 28- and 48-week lead-in arms (4 and 5 percent, respectively) compared to the no lead-in arms (7 and 12 percent, respectively). Treatment discontinuations due to adverse events were between 9 and 19 percent for patients in the boceprevir arms, compared to 8 percent for the control arm.

Safety data from the HCV SPRINT-1 study showed that the most common adverse events reported in the boceprevir arms were fatigue, anemia, nausea and headache. The incidence of skin adverse events (rash or pruritus) observed in the boceprevir arms was comparable to that seen in the PegIntron and Rebetol control arm.

About the Boceprevir Phase III Registration Studies

The two randomized, double-blind, placebo-controlled registration studies evaluate boceprevir in combination with PegIntron and Rebetol compared to standard of care with PegIntron and Rebetol alone. The HCV SPRINT-2 study evaluates the efficacy of 28- and 48-week regimens of boceprevir (800 mg TID [3 times daily]) in combination with PegIntron (1.5 mcg/kg/week) and Rebetol (600-1400 mg/day) compared to a control of PegIntron and Rebetol alone for 48 weeks in treatment-naive adult patients with chronic HCV genotype 1. The study enrolled a total of 1,099 patients, including 158 African-American/Black patients. The HCV RESPOND-2 study evaluates 36- and 48-week regimens of boceprevir in combination with PegIntron and Rebetol at the same doses as described above compared to a control of PegIntron and Rebetol alone for 48 weeks in adult patients with chronic HCV genotype 1 who failed prior treatment (relapsers and nonresponders) with peginterferon and ribavirin combination therapy. The study enrolled a total of 404 patients. In both studies, RVR criteria at 4 weeks of boceprevir treatment (treatment week 8) is used to determine which boceprevir patients can stop all treatment at 28 weeks (HCV SPRINT-2) or 36 weeks (HCV RESPOND-2).

For more information about these ongoing registration studies, please visit www.clinicaltrials.gov, search term boceprevir.

For the full text of this press release, which includes detailed safety information, as well as links to the full U.S. prescribing information and Medication Guide for PegIntron, see www.schering-plough.com.