Schering-Plough yesterday said it has stopped a Phase II trial of its investigational anti-HIV drug, vicriviroc, plus GlaxoSmithKline’s Combivir (lamivudine plus zidovudine) in treatment-naive patients after detectable virus resurfaced during late stages of the therapy. In contrast, participants given the gold standard of Combivir plus Bristol-Myers Squibb’s Sustiva (efavirenz) saw their viral load remain at undetectable levels.

The 92-patient study, which was initiated in 2004 in centres across Europe and Canada, was terminated after a recommendation from an independent Data Safety Monitoring

Board. Patients will continue to receive vicriviroc until they can be switched to an alternative treatment regimen, said Schering-Plough, adding that a second fully-enrolled study in treatment-experienced patients will continue under the auspices of the US National Institutes for Health-sponsored AIDS Clinical Trials Group.

Said Robert Spiegel, chief medical officer and senior vice president of medical affairs, Schering-Plough Research Institute: “We will continue to evaluate the potential use of vicriviroc in combination with other treatment regimens, including those used in the treatment-naive patient population.”

Vicriviroc is a CCR5 antagonist that works by blocking entry of the virus into human cells. Because of its long metabolic half-life (time in the body before excretion), vicriviroc is likely to be a once-daily offering.