HIV Vaccine Trial Shows Promise for First Time, Study Shows

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HIV Vaccine Shows Promise for First Time, Study Shows

2009-09-24 10:16:53.53 GMT

By Simeon

Sept. 24 (Bloomberg) -- An experimental vaccine prevented

HIV infections for the first time, a breakthrough that has

eluded scientists for a quarter century.

A U.S.-funded study involving more than 16,000 volunteers

in Thailand found that a combination of ALVAC, made by Paris-

based Sanofi-Aventis SA, and AIDSVAX, from VaxGen Inc., of South

San Francisco, cut infections by 31.2 percent in the people who

received it compared with those on a placebo, scientists said

today in Bangkok. Neither vaccine had stopped the virus that

causes AIDS when tested separately in previous studies.

The finding represents a revival in a campaign that

appeared to stall just two years ago when use of Merck & Co.'s

experimental Ad5 vaccine boosted some people's chances of

infection in a study. The latest result will transform future

research, said Warren, director of the New York-based

AIDS Vaccine Advocacy Coalition.

" Wow, " said Warren, who was not involved in the study, in

a telephone interview today. " We are in a new place in the

search for an AIDS vaccine. It's safe to say that the scientific

community is caught off-guard. "

The findings don't mean the vaccine can be delivered

worldwide, because of the complexity of the process and the fact

that it's based on old technology, Warren said. Instead they

will serve to spur scientists to look for better combinations in

more user-friendly regimens with higher success rates, he said.

Different Strategies

The Thailand study looked at whether different infection-

fighting strategies devised by Sanofi and VaxGen could be

combined into a two-pronged attack. It was conducted by

Thailand's Ministry of Public Health over six years, and led by

researcher Supachai Reks-Gnarm.

" What is exciting is that this has provided a proof of

concept, that we can do this, " said Cate Hankins, chief

scientific officer at UNAIDS, the United Nations AIDS-fighting

agency. " Anything is possible now, it feels. It is a scientific

breakthrough, " Hankins said by phone from London.

Sanofi's ALVAC uses a canarypox virus that's been disabled

so it doesn't cause sickness in humans to smuggle three HIV

genes into the body. It's designed to coax the immune system to

make so-called T-cells, protectors that hunt and kill infection

deep inside the body.

The AIDSVAX shot contains an HIV protein called gp120

that's used by the virus to enter human cells. It is designed to

encourage the body to produce neutralizing antibodies to destroy

HIV viruses before they can infect healthy cells.

No Cure

The search for a vaccine to prevent HIV has eluded

scientists since the early 1980s. AIDS, the syndrome linked with

HIV, infects about 6,800 new people globally every day. While

there are treatments for HIV that limit the virus in the body,

holding AIDS at bay for years, there is no cure.

" This is the first concrete evidence, since the discovery

of the virus in 1983, that a vaccine against HIV is eventually

feasible, " Michel DeWilde, senior vice president of research at

Sanofi Pasteur, the French drugmaker's vaccine arm, said in a

statement today.

An international test of the Ad5 vaccine made by Whitehouse

Station, New Jersey-based Merck in about 3,000 people was halted

in September 2007, when 49 HIV infections occurred among those

who received it compared with 33 among those who got placebo

shots. That suggested the product may have raised HIV risk among

people exposed to blood or semen containing the virus.

In 2004, a group of U.S. AIDS researchers said in a letter

to the journal Science that the combination trial would probably

disappoint, and shouldn't be allowed to proceed because of the

failure of the two previous studies.

Highest HIV Rates

In a telephone interview from Oxford, England, before the

results were reported, Marie-e Kieny, director of the World

Health Organization's Initiative for Vaccine Research in Geneva,

said, " I don't think there is a lot of expectation that the

efficacy of this vaccine will be very high. Any hint towards

identifying something which is protective in humans would be

very good news, " she said.

The researchers enrolled volunteers in Thailand's Chon Buri

and Rayong provinces, which have the nation's highest rates of

HIV, according to the study Web site.

Subjects were given four doses of the ALVAC vaccine and two

of the AIDSVAX shot over six months, then monitored for three

years. They were also given advice on safe sex. There were no

serious side effects, the researchers said.

Free Treatment

Of those who received the vaccine, 51 became infected with

HIV, compared with 74 who received a placebo, the researchers

said. Those in the study who became infected with HIV during the

trial were given free access to treatment.

In another finding, the vaccine failed to reduce the amount

of virus in the blood of subjects who became infected.

Researchers had hoped that if the vaccine didn't prevent

infections, it would at least cut the virus to levels so low it

couldn't be transmitted.

" Although the results were modest, with an efficacy of

31.2 percent, this is a very important scientific advance, and

gives us hope that a globally effective HIV vaccine may be

possible in the future, " said Jerome Kim, a deputy director of

science at the Walter Army Institute of Research, which

sponsored the trial. " It has already caused us to change some

of our ideas, " Kim told reporters.

The researchers don't understand exactly how the vaccine

prevented infections or why it didn't reduce viral load.

'Slew of Studies'

" We need to find out a lot more about how it went about

reducing HIV risk, " said UNAIDS's Hankins. " There's a whole

slew of studies being planned now and meetings being planned to

discuss the significance of the results, and to go into detail

on the data. "

The same vaccine may not necessarily have the same effect

in other parts of the world, such as Africa, where different

strains of HIV circulate, Hankins said.

VaxGen, spun off in 1995 from South San Francisco,

California-based biotech company Genentech Inc., stopped

developing AIDSVAX in 2003 after a trial showed it didn't

prevent people from getting HIV. The Global Solutions for

Infectious Diseases, a South San Francisco-based non-profit

organization, acquired the rights to the product.

The Thailand trial was funded by the National Institute of

Allergy and Infectious Diseases, the National Institutes of

Health and the U.S. Army Medial Research and Materiel Command.

--Editors: Reg Gale, Phil Serafino.

To contact the reporter on this story:

Simeon in Singapore at +65-6212-1574 or

sbennett9@....

To contact the editors responsible for this story:

Reg Gale at +1-212-617-2563 or

rgale5@...;

Lena Lee at +65-6212-1892 or

llee42@...