AEGiS-AIDSWeekly: HIV/AIDS: Data from STEP Study Presented at Open Scientific Session Confirm Merck's Investigational HIV Vaccine was not Effective

Important note: Information in this article was accurate in November 2007. The state of the art may have changed since the publication date.

HIV/AIDS: Data from STEP Study Presented at Open Scientific Session Confirm Merck's Investigational HIV Vaccine was not Effective

AIDSWEEKLY Plus; Monday, November 19, 2007
Staff Medical Writers

NewsRx -- In the STEP study, one of two phase II trials of Merck & Co., Inc.'s investigational HIV vaccine (V520), the vaccine was not effective at either preventing infection in volunteers not previously infected with HIV or at reducing viral loads in those study volunteers who became infected with HIV during the trial. Analyses presented today indicate that in those volunteers with pre-existing immunity to the cold virus used as a carrier for synthetic HIV genes in the vaccine, there were more infections in those volunteers who received the vaccine than in those who received placebo. Most of these analyses are considered exploratory in nature, and the reasons for this result are still being studied. The study was co-sponsored by Merck & Co., Inc.; the National Institute of Allergy and Infectious Diseases (NIAID), part of the U.S. National Institutes of Health; and the HIV Vaccine Trials Network (HVTN), which is funded by NIAID (see also HIV/AIDS).

Data from the first, planned interim analysis of STEP in one study population were first reported on Sept. 21, 2007 by the three trial sponsors. New analyses of the data from the entire study population were presented today at a special open scientific meeting of the HVTN. These new analyses are summarized below, and will be available at www.hvtn.org by Nov. 14, 2007. Additional analyses are underway and will be shared as more information becomes available.

The vaccine cannot cause HIV infection. The vaccine was created using a mixture of three components, each made with a replication-defective version of one of the common cold viruses, adenovirus type 5 (Ad5), which served as a carrier, or delivery vector, for three synthetically produced HIV genes.

The current STEP results suggest that those who received the vaccine might have an increased susceptibility to acquiring HIV infection, particularly those volunteers who had higher levels of pre-existing immunity to Ad5 because of prior natural exposure to Ad5. However, there are a number of confounding factors that make it very difficult to draw conclusions about this finding.

All but one infection was in men, primarily in men who reported having sex with other men, so little information is available about the effects of the vaccine in women or in heterosexual men.

Study volunteers are being counseled about the possibility that those who received the vaccine may be more susceptible to developing HIV infection when exposed to HIV.

"The data from this trial are remarkably complex. We are analyzing the data to try to determine if the results are due to immune responses induced by the vaccine, differences in study populations, or some other biological phenomenon we don't yet understand, or simply due to chance," said Keith Gottesdiener, M.D., vice president, Vaccine and Infectious Disease Clinical Research, Merck Research Laboratories. "It will take some time before we understand why the vaccine did not work and why there was a trend toward more cases of infection in volunteers who received the vaccine. We recognize that understanding STEP is important for the study volunteers, investigators and for the entire field of HIV vaccine research, and we remain committed to continuing to thoroughly analyze the data and share it as broadly and as quickly as possible."

"We are enormously grateful to the investigators and volunteers who have dedicated so much of their time and their energy to these trials," said Larry Corey, M.D., principal investigator of the HVTN. "We know the STEP study results are of great importance to our volunteers and to our network of investigators around the world. We may not be able to fully understand the results of STEP until more research is conducted. We are optimistic that this work will provide insight into how to advance the search for an effective HIV vaccine."

Further analyses are being conducted. The trial partners will share the data as it becomes available with the broader scientific community at subsequent scientific meetings and in publications over the next several months. A presentation is scheduled at the Conference on Retroviruses and Opportunistic Infections in Boston in February, 2008.

Summary of Data and Analyses of STEP Presented at HVTN meeting, Nov. 7, 2007

STEP analyses will be available at www.hvtn.org by Nov. 14, 2007.

Keywords: HIV/AIDS, AIDS, Acquired Immunodeficiency Syndrome, Biotechnology, Clinical Trial Research, Common Cold, HIV, Human Immunodeficiency Virus, Merck & Company Inc., Opportunistic Infections, Pharmaceutical Business, Pharmaceutical Company, Vaccines, Viral Load, Virology, Merck & Co. Inc.

This article was prepared by AIDS Weekly editors from staff and other reports.

2007-11-19
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