European AIDS activists are opposing the start of a drug-dosing trial of an anti-HIV drug under development by Pfizer. Their American counterparts do not share those concerns; they fear that the action may delay development of the next class of drugs.

The drug in question is UK-427,857, recently given the name maraviroc. It is an entry inhibitor in pill form that blocks HIV’s use of the CCR5 coreceptor in gaining access to and infecting cells. Fuzeon (T-20) is the only drug currently available in this class and it must be injected twice a day.

Members of the European AIDS Treatment Group (EATG) claim that the trial design “is unnecessarily putting people with HIV and with severe immune suppression at risk” because the entry criteria are so broad. They say it puts patients at unnecessary risk for progressing to AIDS.

“It is totally unacceptable to treat naive patients with severe immune suppression and high viral loads with a drug combination containing an investigational drug whose potency and ideal dose are still unknown,” charged Swiss activist David Haerry.

Regulatory authorities have had a mixed response. Pfizer has withdrawn the trial from sites in France, Germany and Spain, but it is continuing in Belgium, Italy, Switzerland, the United Kingdom and the U.S.

Bob Huff, editor of GHMC Treatment Issues, said the ethical concerns are based on individual beliefs about ethics and not on a careful consideration of the specifics of the drug and the science. In fact, the regulatory agencies have assumed their responsibilities and decided to approve the current trial design, he said, even after considering the objections.

Huff believes this has turned into an unfortunate test of power between the EATG and Pfizer.

Huff said there has been a great deal of discussion about the EATG position on the U.S. AIDS Treatment Activists Coalition (ATAC) drug development listserv. Members of EATG are on that listserv but he says they “have not participated in the debate and have failed to represent the complexities to this issue in their statement” to the press.

“Potentially very helpful new drugs and classes of drugs must be tested in the populations for which they will be used,” said Jules Levin, executive director of the National AIDS Treatment Advocacy Project. “That’s the way drugs are developed.

She added, “It’s unfortunate they [EATG] took their position and acted upon it without discussing it all with American activist groups. Their actions delay the start of Phase III trials in certain European countries, which is not good for the patients in those countries.”

Huff expects that the broader impact in slowing development of the drug will not be significant, “unless it spreads,” and enrollment of patients in other countries is deferred. It is possible that enrollment slots in the trial will be shifted to other countries.

Perhaps the greatest fear for some AIDS advocates is that actions such as this will make drug companies less willing to work with the community, or put resources into developing drugs to treat HIV.