Patients with the AIDS virus got no benefit from a Novartis AG drug that sparks the creation of immune cells to replace those destroyed by the disease.

Two studies, one involving patients with high numbers of immune CD4 cells, and the other involving patients with fewer of the cells, failed to show benefit from the treatment, doctors said today at the Conference on Retroviruses and Opportunistic Infections in Montreal. Novartis sells the interleukin-2 drug as Proleukin to treat cancer.

Researchers believe damage to the body's protective immune system from HIV, the human immunodeficiency virus that causes AIDS, worsens the disease. While earlier results with the drug called interleukin-2 showed promise, treated patients fared no better than those who didn't get it in the latest research.

"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 wasn't involved in the studies, in an interview at the conference. "This entire trial has never quite been able to cross the goal line; it's never been able to show a clinical benefit."

Interleukin-2 is a cytokine, a type of natural body chemical that activates the immune system and is approved to treat skin and kidney cancer. The two trials looked at whether it helped people who were also getting treatment with powerful anti- retroviral drug combinations.

Immune Cell Levels

One study, funded with $65 million from the U.S. National Institutes of Health since 2000, looked at its effect in 4,011 people who began with more than 300 CD4 cells per milliliter of blood. U.S. guidelines recommend treating HIV-infected adults when CD4 cell levels drop to 350 per milliliters of blood.

The second study, which was started by Chiron Corp. before it was bought by Novartis, examined the treatment in 1,695 patients who began with 50 to 299 CD4 cells per milliliter of blood. Chiron gave $18 million to finish the study after 2003, when the company decided to drop it, said James Neaton, a University of Wisconsin researcher who helped administer the two trials.

Treatment raised immune cell levels in both trials more than researchers expected, said Marcelo Losso, an HIV researcher from the Hospital Jose Maria Ramos Mejia in Buenos Aires, who presented the results. Death and illness rates were the same in treated and untreated groups.

Interpretation Difficult

Researchers said the results were difficult to interpret, and that further study of them may improve understanding of the immune system.

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

Interleukin-2 may encourage the body to make CD4 cells that respond to other types of illnesses than HIV, said Carl Dieffenbach, director of the Division of AIDS at the National Institute of Allergy and Infectious Diseases.

"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."

In the study of people who began with more than 300 immune CD4 cells per milliliter of blood, serious side effects were more common among those who received the immune treatment, Losso said.