Schering-Plough Corporation reported long-term data with vicriviroc, its investigational extracellular inhibitor of HIV infection, from a Phase 2 study in treatment-experienced HIV-infected patients. This ongoing, open-label extension of the VICTOR-E1 Phase 2 study was designed to provide continued therapy with vicriviroc and to collect safety data. Evidence for sustained viral suppression and CD4 cell count improvement was monitored. After completing 48 weeks of treatment in the double-blind phase of the VICTOR-E1 study, patients (including patients in the placebo arm) were offered open-label vicriviroc 30 mg once daily plus an optimized antiretroviral regimen containing a ritonavir-boosted protease inhibitor. The mean duration of vicriviroc treatment in the open-label phase was 13 months. The results showed that vicriviroc plus optimized background therapy achieved durable virologic suppression and increased CD4 cell counts, and was generally well tolerated over two years of therapy. The virologic effect seen during the double-blind phase of the study was sustained in these patients during open-label vicriviroc treatment, with the percentage of patients achieving undetectable virus increasing over the course of therapy. Importantly, further improvements in CD4 counts were observed with longer vicriviroc therapy, with a mean increase of 50 cells/mm3 from week 48 of the double-blind study to the end of the 96-week period.
Vicriviroc, currently in Phase 3 development, is a CCR5 receptor antagonist designed to prevent the virus from infecting healthy CD4 cells by blocking its predominant entry route, the CCR5 co-receptor. Approximately 50-60 percent of treatment-experienced patients have virus that uses the CCR5 co-receptor.
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