Some AIDS Advocates Call on Pfizer To Stop Clinical Trial of CCR5 Inhibitor Because of Concerns Over Study Design

Some HIV/AIDS advocates on Tuesday called on the pharmaceutical company Pfizer to stop clinical trials of an experimental CCR5 inhibitor because of concerns that the study's design jeopardizes patient safety, Reuters reports. The European AIDS Treatment Group said the trials to test maraviroc -- previously called UK-427,857 -- put HIV-positive patients at "unnecessary risk" of developing AIDS. The group said the design of the trials offers patients "no safety net" and allows previously untreated HIV-positive people to enroll regardless of their viral load or CD4+ T cell levels, according to Reuters. EATG called the trials "unethical," saying they could endanger patients who need access to "proven" treatments instead of an investigational drug, Reuters reports (Hirschler, Reuters, 4/12). CCR5 inhibitors are part of a new class of antiretroviral drugs that aim to prevent HIV from entering human cells rather than fighting the virus once it has entered cells. CCR5 inhibitors block HIV from docking with a human cell's CCR5 receptor, which is where HIV usually latches onto a cell to enter it. Previous studies have shown that people who lack CCR5 receptors because of genetic mutations rarely contract HIV (Kaiser Daily HIV/AIDS Report, 2/18). "The trial design should be changed or otherwise stopped," EATG Chair Mauro Guarinieri said in a statement, adding, "We demand all concerned regulatory authorities to assume their responsibility and act accordingly." Pfizer "disagreed," saying the study contains "appropriate checks and balances to protect patient safety" while also allowing researchers to explore the drug's future use, according to Reuters.

Background, Trial Details
Pfizer is "in a race" with other pharmaceutical companies to bring to market a CCR5 inhibitor, Reuters reports (Reuters, 4/12). Drug companies GlaxoSmithKline and Schering-Plough also are conducting clinical trials testing CCR5 inhibitors. The compounds developed by GSK in partnership with Schering-Plough have had no harmful side effects in early studies, and the companies hope to file for FDA approval as early as 2007 (Kaiser Daily HIV/AIDS Report, 2/18). According to industry analysts, Pfizer is a "few months ahead" of its competitors, Reuters reports. Pfizer currently is enrolling HIV-positive patients or has approval to start clinical trials in Australia, Belgium, Canada, Italy, Mexico, Netherlands, Switzerland, the United Kingdom and the United States. However, plans to conduct trials in France, Germany and Spain have been suspended over concerns about the study design (Reuters, 4/12).