The product was administered in once-daily doses in combination with an optimized ritonavir-boosted antiretroviral regimen.
Vicriviroc is an extracellular inhibitor of HIV infection designed to block entry of infectious virions into uninfected CD4 cells via antagonism of the CCR5 co-receptor. Schering-Plough says these results represent the longest follow-up data reported to date for any CCR5 antagonist.
At 48 weeks, patients in the 10mg and 15mg vicriviroc treatment groups achieved a median decrease in viral load of 1.92 and 1.44 and a median increase in CD4 cell count of 130 and 96 from baseline, respectively. More patients in the vicriviroc groups had undetectable virus at 48 weeks compared to those in the placebo group (57/37% and 43/27% vs. 14/11% respectively). Fewer patients in the vicriviroc groups experienced virological failure compared to those in the placebo group (27 and 33% vs. 86% respectively).
In the study, there was no significant difference in grade three or four side affects across the vicriviroc and placebo groups. In total, eight patients randomized to vicriviroc and two patients randomized to placebo developed malignancies. No cases of seizure were reported.
“New antiviral agents with novel mechanisms of action and unique resistance profiles are urgently needed for this challenging patient population, and we look forward to the further clinical evaluation of vicriviroc in combination with antiretroviral regimens,” said Roy Gulick, principal investigator and professor, Weill Medical College of Cornell University, New York, who presented the data.