Schering-Plough Initiates Phase III Studies with Vicriviroc in Treatment- Experienced HIV Patients

Schering-Plough Corporation (NYSE: SGP) today [September 17, 2007] announced that it has initiated two large Phase III clinical studies with vicriviroc, its investigational CCR5 antagonist, administered once-daily as a single 30 mg tablet in combination with an optimized background therapy that must include a protease inhibitor boosted by ritonavir in adult treatment-experienced HIV patients with R5-type virus only.

Vicriviroc is a next-generation extracellular inhibitor of HIV infection designed to block entry of infectious virions into uninfected CD4 cells via antagonism of the CCR5 co-receptor.

The vicriviroc Phase III clinical program builds upon previous studies in HIV treatment-experienced patients, including a Phase II study (ACTG 5211) in which vicriviroc demonstrated potent and sustained viral suppression through 48 weeks of therapy.[1]

The two Phase III studies, known as VICTOR-E3 and VICTOR-E4 (Vicriviroc in Combination Treatment with an Optimized Antiretroviral Therapy Regimen in HIV-Infected Treatment-Experienced Subjects), will evaluate the virologic benefit of adding vicriviroc 30 mg once daily to an optimized background therapy compared to a control group receiving new optimized background therapy alone.

The studies will also evaluate the safety and tolerability of vicriviroc compared to placebo. The optimized background therapy must include at least two drugs that are active, based on susceptibility testing.

Patients coinfected with hepatitis C may be included in the studies and there are no exclusions of commonly prescribed drugs or need for dose adjustments based on the known vicriviroc drug-drug interaction profile.

The studies will enroll approximately 375 patients each at more than 160 sites in North America, South America, Europe, Australia, and South Africa.

"As a next-generation HIV entry inhibitor, vicriviroc has the potential to benefit a broad range of patients by offering a potent, sustained viral response and a single once-daily dose in combination with optimized background therapy," said Robert J. Spiegel, M.D., chief medical officer and senior vice president, Schering-Plough Research Institute. "There is an urgent need for new antiretroviral agents with novel mechanisms of action, and we look forward to the further clinical evaluation of vicriviroc in these large global studies."

About the VICTOR-E3 and VICTOR-E4
Phase III Studies

VICTOR-E3 and VICTOR-E4 are identically designed, randomized, double-blind, placebo-controlled, parallel group, multicenter studies of vicriviroc in adult treatment-experienced patients infected with CCR5-tropic HIV virus (no detectable CXCR4-tropic or dual/mixed CCR5/CXCR4-tropic virus at screening).

The primary efficacy endpoint of the studies will be the proportion of patients with plasma HIV-1 RNA less than 50 copies/mL at week 48. Key secondary endpoints, each measured at 48 weeks, include the proportion of patients with less than 400 copies/mL of plasma HIV-1 RNA, mean change from baseline in plasma HIV-1 RNA (log10 copies/mL) and mean change from baseline CD4+ count. All efficacy endpoints will also be evaluated at week 24.

Patients in VICTOR-E3 and VICTOR-E4 must have documented resistance to at least two of the three antiretroviral drug classes (NRTI, NNRTI or PI) or 6 months or more of experience with at least two of the following: one NRTI, one NNRTI or two PIs (excluding low-dose ritonavir); and must have plasma HIV-1 RNA levels above 1000 copies/mL.

The optimized background therapy must include a protease inhibitor boosted by ritonavir and at least two drugs that are active, based on susceptibility testing. The optimized background therapy will be chosen by the investigator based on results of drug susceptibility tests performed at screening, patient history of prior antiretroviral drug use and drug toxicity.

The VICTOR-E3 and VICTOR-E4 studies will also evaluate the safety and tolerability of vicriviroc compared to placebo, each given in combination with an optimized background therapy. An independent, external Data Safety Monitoring Board (DSMB) will review study data on a regular basis to assure continued safety of the participants.

For more information about the VICTOR-E3 and VICTOR-E4 clinical studies, please visit ClinicalTrials.com:

http://www.clinicaltrials.gov/ct/show/NCT00474370

and

http://www.clinicaltrials.gov/ct/show/NCT00523211.