Two studies presented at the 16th Conference on Retroviruses and Opportunistic Infections in Montreal showed no benefit for HIV patients given a cancer drug designed to create immune cells.

While earlier results showed promise, patients treated with Novartis' interleukin-2 (Proleukin) fared no better than patients who did not receive the drug. "As far as I'm concerned, this is the end of interleukin-2 for HIV," said John Bartlett, a Johns Hopkins University AIDS researcher, who was not involved with the studies.

Interleukin-2 is a cytokine, a chemical that occurs naturally in the body and activates the immune system. It is approved to treat skin and kidney cancer. The two trials examined whether it would be of benefit to patients on antiretroviral regimens.

A $65 million, National Institutes of Health-funded study looked at interleukin-2's effect on 4,011 people who began with CD4 levels higher than 300 per cubic millimeter of blood. The second study involved 1,695 patients who started with CD4 counts of 50 to 299. US guidelines recommend treating HIV patients when CD4 levels drop below 350.

While the drug raised immune cell levels in both trials more than researchers expected, death and illness rates were the same in treated and untreated groups, said Marcelo Losso of the Hospital Jose Maria Ramos Mejia in Buenos Aires, who presented the results. In the study of people who began with CD4 counts of more than 300, serious side effects were more common among those who received interleukin-2, he said.

"We could increase CD4 cell levels with the treatment but not improve the outcome," said Bartlett. "Maybe getting them to the highest level possible isn't as important as we thought it was."

Carl Dieffenbach, director of the Division of AIDS at the National Institute of Allergy and Infectious Diseases, said interleukin-2 may encourage the body to make CD4 cells that respond to illnesses other than HIV. "There's something significantly different about the cells that get boosted with interleukin-2," he said. "Interleukin-2 is effective in cancer, and that may tell us something about HIV as a disease and cancer as a disease."