The National Institutes of Health (NIH) has decided not to fund full-scale clinical trials of the leading AIDS vaccine. The decision will be announced next week, ScienceNOW has learned. The U.S. military, however, is still planning to go ahead with a trial of a similar vaccine.
According to well-placed sources, NIH's National Institute of Allergy and Infectious Diseases decided to pull the plug when an interim analysis of an ongoing, smaller trial showed that the vaccine failed to elicit strong immune responses against HIV. The vaccine, made by the Franco-German pharmaceutical company Aventis Pasteur, consists of HIV genes stitched into a harmless bird virus, canarypox. The $60 million to $80 million trial involving 11,000 people was planned to begin in the United States, South America, and the Caribbean by the end of this year.
Researchers have long known that the vaccine does little to stimulate production of antibodies, which prevent viruses from infecting cells. But in some people it stimulates production of immunologic warriors called killer cells, which target and destroy cells infected by the virus. The planned trial was designed to test whether this immune response provides any protection from disease. But fewer than 30% of the 330 volunteers in the smaller trial developed these killer cell responses, a fraction too small to provide statistically significant results in the large-scale test.
The U.S. military's AIDS research program has independently decided to stage a large-scale efficacy trial of a one-two punch that combines the Aventis Pasteur vaccine with one containing a genetically engineered version of HIV's surface protein. The second vaccine aims to stimulate antibody production. Col. John McNeil, who heads the military AIDS vaccine program, says the trial should determine whether the vaccine provides any overall protection. But he says it will not have the statistical power to tell which immune responses are most significant--important information for future vaccine development. The trial, which will cost $35 million to $45 million and involve 16,000 people, will take place in Thailand in cooperation with researchers and officials there. If all goes as planned, the trial will start this summer.
Immunologist John Moore, who wrote a commentary in the 24 January issue of Nature that criticized NIH and the Department of Defense for planning "duplicative" trials of the canarypox vaccine, applauds the decision to abort the NIH-funded study. "They have shown excellent judgment after reviewing the scientific data."
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