FDA Approves AIDS Vaccine Trial
By LAURAN NEERGAARD AP Medical Writer
WASHINGTON (AP) -- The Food and Drug Administration has granted a California company permission to begin the largest test yet of a possible vaccine to prevent infection by the virus that causes AIDS.
There's no guarantee the vaccine will work, and many U.S. scientists are highly skeptical because it's based on a concept that the National Institutes of Health shelved in 1994.
But the three-year trial of VaxGen Inc.'s AIDSvax, which will include 5,000 American volunteers at high risk for catching the AIDS virus and 2,500 high-risk people in Thailand, should at least settle long debate about this approach.
''My own feeling is that it's unlikely this is going to be a protective vaccine,'' said Dr. Arthur Amman, a well-known AIDS specialist with the American Foundation for AIDS Research. ''But to answer the question, you've almost got to do the study.''
An anti-AIDS vaccine would train the human immune system to ward off infection with HIV, the AIDS virus. Some 25 potential vaccines have been tried in people worldwide. Until now none has advanced to the larger-scale testing, known as a Phase III trial, allowed for AIDSvax.
VaxGen, the producer, is optimistic. It contends AIDSvax is an improved version of the controversial gp120 vaccine, because the company added another strain of HIV protection to the original shot.
Smaller tests of AIDSvax showed 99.5 percent of vaccinated people produced strong levels of antibodies, immune system cells that can target and kill infection, explained VaxGen chief operating officer Daniel T. Reiner.
Beginning the first Phase III trial of a possible vaccine ''is a watershed event,'' said Dr. Seth Berkley of the International AIDS Vaccine Initiative, a new nonprofit group pushing development of a vaccine.
By allowing large-scale testing, the FDA did not say that AIDSvax will work -- just that it is safe enough to attempt.
Early vaccine research focused on producing antibodies. But many scientists now believe antibodies alone won't work. They also want a vaccine to create lymphocytes, another important immune system cell. Newer vaccine candidates now in Phase II testing are considered highly promising for both protections. These include vaccines made from DNA, or the genetic code of the virus, and a French attempt using canarypox.
Others want to vaccinate people with live but weakened portions of the HIV virus, much like a polio vaccine works. The FDA is considering that request.
VaxGen's approach is to engineer copies of gp120, the outer coating of the HIV virus, to force people's immune systems to ward off the two most common subtypes of HIV. There are two formulations, one with the most common U.S. subtypes and one that contains the most common strains in Southeast Asia.
In the early 1990s, the NIH, California-based Genentech Inc. and several other companies attempted a gp120 vaccine made from just one HIV subtype. In 1994, the NIH decided the vaccine was too weak to justify further study, and most scientists shelved it.
But Dr. Donald Francis, the Centers for Disease Control and Prevention doctor who helped uncover AIDS in the early 1980s, thought gp120 still could work. In 1996, he worked with Genentech to cofound VaxGen, raised $27 million and added a new subtype to the shots in hopes of boosting its protection.
''Whether that's going to be sufficient is anybody's guess,'' said Dr. Mark Feinberg, an Emory University immunologist formerly with NIH's Office of AIDS Research. ''This is the beginning of the evaluation of HIV vaccines for efficacy. It is certainly not the end of the story.''
VaxGen will begin recruiting U.S. volunteers next month in Chicago, Denver, Los Angeles, Philadelphia and St. Louis and will add other cities later in the year. The company is hunting people who do not have HIV but are at high risk for catching it, such as women who have HIV-infected partners and homosexual men.
In Thailand, vaccine volunteers will come from methadone clinics, because people who use injecting drugs like heroin are at particular risk of getting HIV.
Some people will get the vaccine and others a placebo, but both groups will get intensive HIV education to alert them to the dangers of sharing drug needles and the need for safe sex, VaxGen's Reiner said.
''We're going to caution and counsel and warn as strongly as we can,'' he said.
(PROFILE (CO:Genentech Inc; TS:GNE; IG:MTC;) (CAT:Business;) (CAT:Medical;) )
AP-NY-06-03-98 1753EDT
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