Important note: Information in this article was accurate in 2007. The state of the art may have changed since the publication date.
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Wall Street Journal - September 22, 2007
Marilyn Chase, marilyn.chase@wsj.com and Mark Schoofs, mark.schoofs@wsj.com
The collapse of the trial leaves Merck & Co., which had spent a decade developing the vaccine, with no remaining prospects in the global hunt for an AIDS immunization. The vaccine was tested in a network funded by the National Institutes of Health.
"We've been kicked in the teeth," said Bruce Walker, a veteran AIDS researcher at Harvard University who wasn't involved in the study. Lawrence Corey, a leader of the NIH-funded HIV Vaccine Trials Network, said he was "mourning."
The results are particularly disappointing because it is widely agreed that only a vaccine could end the epidemic. Last year, more than four million people world-wide contracted HIV, the virus that causes AIDS, and nearly three million died, according to United Nations estimates. Almost 40 million people are currently living with HIV.
But researchers cautioned against overreacting. Merck's vaccine is one of many in or heading into clinical trials, and different types of vaccines are known to stimulate different kinds of immunity. For example, an experimental immunization now in human trials that was developed by the HIV Vaccine Research Center of the NIH had shown more-promising results in monkey trials than did the Merck vaccine.
"It isn't the end of the line," said Mitchell Warren, executive director of the AIDS Vaccine Advocacy Coalition, a New York group advocating prevention. Merck's data "aren't the answers we wanted, but they will help improve our other vaccine candidates."
Tuesday, the trial was stopped early by independent overseers known as the Data & Safety Monitoring Board. Comparing two groups -- those who received the vaccine and those who received a placebo -- the overseers determined there was virtually no statistical difference in infection rates between them, indicating the vaccine wasn't working. Also, the amount of HIV in the blood of those who did get infected, a predictor of how fast a person will get full-blown AIDS, was virtually the same in each group.
The ultimate fear among researchers is that the whole theory underlying the Merck vaccine might be flawed, which, if true, could doom an entire class of experimental vaccines.
Most classical vaccines, such as those against smallpox or polio, stimulate the body to produce antibodies that ward off infection. But stimulating antibodies that neutralize a broad range of HIV strains has been notoriously difficult, so researchers focused on the other arm of the immune system: killer T-cells, which attack and kill cells that HIV has already infected. Such vaccines have been considered less likely to prevent someone from getting infected; instead, it was hoped they would enable an infected person to suppress the virus and so delay, perhaps for many years, the onset of disease.
"Given that this study was the leading edge" of research on T-cell based HIV vaccines, said Mark Feinberg, vice president for medical affairs and health policy in Merck's vaccine division, "there was great disappointment."
"There is nothing on the horizon" at Merck, he said. "We don't have any other vaccine candidates we've identified as promising enough to advance into clinical studies." Dr. Feinberg added that Merck is "committed to finding ways to share information accumulated over two decades to facilitate the broader effort" to develop an AIDS vaccine.
The Merck vaccine did stimulate the immune system's T-cells -- a notable development -- but not in a way that helped infected test subjects control the virus. Now, researchers will try to figure out why.
Merck's shares, reflecting downplayed hopes that such an early vaccine would work, were up 44 cents to $51.82 at 4 p.m. Friday in New York Stock Exchange composite trading.
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Sarah Rubenstein contributed to this article.
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