GlaxoSmithKline last week in a statement to the HIV/AIDS patient community said it has suspended a Phase III trial of the experimental antiretroviral drug aplaviroc after two HIV-positive participants who were taking the drug developed severe liver toxicity, the Wall Street Journal reports. The two participants are among 250 HIV-positive volunteers in the trial -- which has sites in the U.S., Canada and the European Union -- who are newly diagnosed and who have never received treatment for HIV. Neither of the patients died nor required liver transplants. The company discussed the drug's risks with FDA and said it suspended the trial "in the interests of safety," although it was not clear that the liver problems were drug-related, GSK spokesperson Rick Koenig said. Aplaviroc is in a new class of drugs known as entry inhibitors that prevent HIV from entering cells. The treatment-naive patients were receiving aplaviroc in addition to standard HIV treatment, and a control group of 50 volunteers were receiving standard treatment without the experimental drug.

Treatment-Experienced Patients Allowed to Continue
GSK also said it "has taken immediate steps to protect the welfare of patients" involved in other clinical trials of aplaviroc, and it is proceeding with a study of the drug in 20 treatment-experienced patients who have developed resistance to other drugs. Koenig said the liver problems do not necessarily only affect treatment-naive patients but added that the company is allowing the experienced patients to continue with the drugs because their treatment options are limited. The trial also involves a control group of 20 treatment-experienced patients who are receiving standard therapy. GSK said it will not enroll additional participants in the study until it learns more about the liver toxicity side effects. The company also is updating its informed consent form to include information about potential side effects, which continuing volunteers will be required to sign (Chase, Wall Street Journal, 9/19). The suspension of the trial in treatment-naive patients sets GSK back against Pfizer, which is ahead in testing its rival entry inhibitor maraviroc. Schering-Plough also is working on an entry inhibitor. According to industry analysts, an entry inhibitor could be available on the market in 2007 or 2008 and generate sales of $500 million to $700 million annually (Hirschler, Reuters, 9/19).

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