Vicriviroc is an investigational CCR5 receptor antagonist currently being evaluated by the NIH-sponsored Adult AIDS Clinical Trials Group (ACTG) in an ongoing phase II clinical study of 118 treatment-experienced HIV patients in the US. Patients who entered this trial were heavily treatment experienced with advanced HIV disease and low CD4 counts.
The ACTG study monitoring committee for this trial has informed the ACTG and Schering-Plough that five cases of malignancy have been observed in patients treated with vicriviroc. The five cases included four patients with lymphoma and one patient with gastric adenocarcinoma (stomach cancer).
The ACTG has concluded that a causal association between vicriviroc and the lymphoma cases could not be established at this time. The ACTG further concluded that, since vicriviroc, at the two highest doses tested, together with an optimized background antiretroviral regimen showed evidence of virologic activity and CD4 count increases, the trial will continue.
Patients and investigators in the trial are immediately being informed of these results. The ACTG is taking additional measures to assure the safety of patients in the trial. These include introducing long-term follow-up and unblinding the patients in order that they and their physicians may make a more informed decision about their treatment options.
Schering-Plough said that it intends to continue to work closely with the ACTG as well as the FDA and other health authorities to fully determine the potential role of vicriviroc in HIV therapy.