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Merck AIDS Failure Hurts HIV Vaccine Research, U.S. Effort
  By John Lauerman
Nov. 15 (Bloomberg) -- The surprise failure of Merck & Co.'s AIDS vaccine may doom other test projects and force researchers to consider whether a protective shot against HIV is feasible.
Merck halted clinical trials of its vaccine in September, and last week researchers said that a cold virus used in the shot may have made test subjects more likely to catch HIV. The finding may cause the U.S. to cancel a study of a similar vaccine and raises concern about projects at Crucell NV.
The Merck setback means that 25 years into the AIDS epidemic doctors are still far from having a protective vaccine. An international team of scientists has been recruited to determine precisely what went wrong. Meanwhile, leading researchers are re-examining their vaccine strategies, said David Ho, who has studied HIV since the epidemic began.
``It's a giant step backwards,'' Ho, scientific director of the Aaron Diamond AIDS Research Center in New York, said in a telephone interview. ``It calls into question all the vaccines using related strategies that have been leading the field.''
Without a vaccine, the mounting number of HIV patients worldwide, now at 40 million, will be harder than ever to slow, and deaths will continue to increase, said John Bartlett, a Johns Hopkins University AIDS researcher in Baltimore. About 2.9 million people died of AIDS-related illness last year, according to the Geneva-based World Health Organization.
Experimental approaches with vaginal microbicides, which researchers hoped would kill HIV during sex, have also failed.
Another Blow
``This really raises the question of what's next,'' Bartlett said in a telephone interview. ``This is yet another blow to the huge enterprise now being devoted to prevention.''
Merck, based in Whitehouse Station, New Jersey, fell 19 cents to $57.30 in New York Stock Exchange composite trading yesterday. The shares are up 31.4 percent for the year. Crucell fell 20 cents to 12.80 euros in Amsterdam. Its shares are down 33.6 percent this year.
The Merck vaccine wasn't considered by scientists to be a fully protective agent that might end the disease. AIDS researchers agree that their understanding of the virus and how the body's immune system reacts to it aren't advanced enough to produce a preventive shot.
The goal of the study was to see whether people who got the Merck candidate and were later infected would have lower amounts of HIV in their blood. That might delay symptoms and the start of drug treatment, and perhaps interfere with the spread of HIV to other people.
Hopes for the vaccine were dashed when an early look at the results of the study found that more people who got the vaccine caught HIV. Infections were highest among people who began the study with high levels of immunity to the cold virus in the shot, called adenovirus-5.
Genetically Engineered
The HIV Vaccine Trials Network that helped Merck run the study immediately formed a committee to establish whether that had something to do with adenovirus-5, the trial design, the selection of subjects, or pure chance, said Bruce Walker, a Harvard Medical School scientist in Boston leading the panel. Their efforts may be hampered because only small amounts of the study subjects' blood and tissue are available, he said.
Merck said it won't decide how to pursue HIV vaccine research until the analysis is complete.
The failed study ``requires not just Merck but the field overall to consider what is the most promising approach for the future,'' said Mark Feinberg, vice president for medical affairs and policy. ``It's not like there are a whole bunch of promising ideas that one can just shift to next.''
The adenovirus was genetically engineered not to cause colds, and instead to make HIV proteins that would prepare the human immune system to fight a real infection. Scientists are troubled by the potential role it may have played in the vaccine's demise.
`Really Urgent'
Some researchers have said the virus may have spurred immune cells to make more of the proteins that allow HIV's entry.
``This is really urgent right now,'' Walker said in a telephone interview. ``There are a lot of vaccines in the pipeline that are adenovirus-based, and we have to figure out what happened here.''
Crucell's vaccine is designed to avoid immune interactions like the one in the trial, said Jaap Goudsmit, the company's chief science officer. Crucell, based in Leiden, the Netherlands, is developing vaccines against tuberculosis and malaria that use other strains of adenovirus. The company's shares have fallen 5.2 percent since the announcement about the cold virus last week.
Concerns about safety have pushed back a trial of a government-developed vaccine that contains adenovirus. The U.S. National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, will hold a meeting of researchers Dec. 12 to determine whether or how to proceed with the vaccine trial.
`Very Conflicted'
The adenovirus in the government's vaccine is genetically different from the one in the Merck trial, and plays a much smaller role in immunization, said Gary Nabel, director of the Vaccine Research Center at the U.S. National Institutes of Health in Bethesda, Maryland, and the vaccine's developer. The threat of HIV makes it crucial to test the vaccine if possible, he said.
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