Schering-Plough Launches Phase III Trials of Experimental Antiretroviral Vicriviroc

Pharmaceutical company Schering-Plough on Monday announced that it has launched two Phase III trials of its experimental antiretroviral drug vicriviroc, Reuters reports (Pierson, Reuters, 9/17). Schering-Plough in August 2006 reported that people taking vicriviroc in a study experienced more lasting decreases in HIV viral levels and rises in CD4+ T cells, compared with a group of people taking a placebo. Five of 90 people taking vicriviroc developed cancer during the study, compared with two of 28 people in the placebo group, which raised concerns about the treatment's link to malignancy. Vicriviroc is in a drug class known as CCR5 inhibitors (Kaiser Daily HIV/AIDS Report, 8/18/06). Schering-Plough said each international Phase III trial will involve 375 participants. The new trials will combine vicriviroc with other antiretroviral treatments, including two protease inhibitors, Reuters reports. The Phase III trials follow a 48-week study in which vicriviroc exhibited "potent and sustained viral suppression" among participants whose virus had not been controlled by prior treatments, the company said.

According to the research firm Cowen, a monitoring committee in early 2006 cited reports of five illnesses -- including four cases of lymphoma and one case of stomach cancer -- among vicriviroc recipients in a Phase II study. The committee said it could not conclude that the tumors resulted from the treatment. Patients in the trial were notified of the cancer but were permitted to continue with the study. According to an abstract of a two-year follow-up study of the participants that was scheduled to be presented Tuesday at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy in Chicago, vicriviroc was potent and durable against HIV and was generally well tolerated, Reuters reports. The study detected no drug-related new lymphomas, liver problems or heart attacks among people who had taken it for an average of more than three years (Reuters, 9/17).

"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," Robert Spiegel, chief medical officer and senior vice president of the Schering-Plough Research Institute, said, adding, "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" (Schering-Plough release, 9/17).