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Biohead
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Scientists on Monday reported a major stride towards a vaginal gel that can thwart HIV, a goal that would be a huge benefit to African women bearing the brunt of the AIDS pandemic.
A prototype cream tested in South Africa reduced the risk of infection by the human immunodeficiency virus (HIV) by 39 percent overall, but by 54 percent among those women who used it most consistently, they said.
The study coincided with the six-day 18th International AIDS Conference, which opened in Vienna on Sunday.
The results must now be validated in a third, wider phase in the arduous process of assessing a new medication for safety and effectiveness.
Although several questions have yet to be answered, the findings are a bright ray of hope in the 29-year campaign against acquired immunodeficiency syndrome (AIDS), the researchers said.
"Without this gel, we may see 10 women becoming infected in a year. With this gel, we would see only six women becoming infected," said Salim Abdool Karim, one of the two leading co-researchers, in a teleconference with reporters.
Twenty-five million people have died from AIDS and more than 33 million others today are infected by HIV, which causes the disease.
More than two-thirds of these live in sub-Saharan Africa, where 60 percent of new infections occur among women and girls.
One of the big vectors of transmission is through coercive intercourse by an infected partner who is unwilling to wear a condom.
The gel that was tested contains a one-percent formulation of tenofovir. It is a frontline component in the "cocktail" of antiretroviral drugs that disrupt HIV reproduction in immune cells.
Previous microbicides that have been tested have not contained an antiretroviral, and have had either a very low level of protection or even boosted the risk of infection.
Over nearly three years, the gel was tested among 445 HIV-negative women, while 444 counterparts received a harmless lookalike called a placebo.
They were then tested for HIV at monthly follow-up visits, where they were also given counselling in safe sex, access to condoms and treatment for sexually-transmitted disease.
Each participant was asked to insert, using a vaginal applicator, a first dose of the gel within 12 hours before sex followed by a second dose as soon as possible but within 12 hours afterwards, said co-leader Quarraisha Abdool Karim, also of the Centre for the AIDS Programme of Research in South Africa (CAPRISA) in Durban.
Compared to the placebo group, the gel reduced the risk of HIV infection by 39 percent overall, but by 54 percent among women who adhered to the instructions most faithfully.
There was no increase in side effects, nor -- among women who became infected with HIV -- any sign that they were more resistant to tenofovir as a result of the gel.
Despite this good news, the scientists said they still had to tackle several important issues.
One is why the gel seemed to be less effective after about 18 months.
This may be due to weakened adherence to the cream, they suggested. About 40 percent of the women in the trial used the microbicide less than one time out of two.
The trial was conducted in an urban setting (Durban) and a rural setting (Pietermaritzburg) KwaZulu-Natal province, enrolling sexually active women aged 18 to 40 considered to be of high risk of exposure to HIV.
It was a so-called IIb trial, meaning that it had passed earlier scrutiny for safety and effectiveness, but was still relatively small compared to a Phase III test involving several thousand volunteers.
The study, published by the journal, Science, was to be the focus of a seminar on Wednesday at the world AIDS forum.
If -- eventually -- the gel is approved for use, it will join a small but growing arsenal of preventative tools against HIV.
For a long time, the condom was the only method that had a confirmed high degree of protection from HIV in intercourse.
Four years ago, it was joined by male circumcision. Removal of the foreskin, which contains cells that are vulnerable to penetration by HIV, can reduce HIV risk by more than half, but only for men and not for women.
Availability of a microbicide that is 60 percent effective would avert two and a half million infections over three years, according to a 2003 mathematical study.
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milray
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I quote here from my contribution to another forum on this topic of tenofovir gel as anti-HIV. The Gilead product, tenofovir, represents no threat to SPL's financial prospects over the next few years and probably little long-term threat.
Reasons for this are those described by another on that forum, with my own take added here:
1. Tenofovir is an effective anti-HIV and anti-hepatitis drug but it has drawbacks. It can have nasty effects in the liver and kidneys and on bone density
2. It is not proven safe for the foetuses of pregnant women (and young, fertile women in undeveloped countries are the prime target market)
3. It may or may not be excreted in human breast milk; it has not been proven safe for babies to consume
4. Resistance to its action may develop
As someone else said, and I agree, use of a potentially dangerous drug like this is only justified in a high-risk population. otherwise the risk of the treatment is greater than the anticipated benefit. This risk may be ameliorated by reduced absorption of tenofovir from topical application as opposed to systemic use but I've not seen any evidence making that comparison. Compare this to VivaGel, where several studies indicate that it is not absorbed into the bloodstream at all when applied topically in the vagina.
So much for tenofovir's competition with VivaGel as a drug. More importantly to us SPL owners, the financial risk is negligible. Jackie Fairley has said that the main immediate commercial opportunities for VivaGel are as condom coating (recently improved by the Reckitt takeover of SSL) and as anti-HSV application in developed countries. To these we now have added the possible strong revenue from BV treatment. With regard to VivaGel as anti-HIV she has said that SPL does not look to great revenue from this because of the expectation that it would be licensed for use mainly in the high risk undeveloped world without the intention to make significant profit from people who have no capacity to pay. Which is exactly what Gilead have stated is their intention with tenofovir, to license it free of royalties in the undeveloped world. As should be.
The really good thing from SPL's perspective, to come from the recently announced tenofovir gel trial, is the proof of the principle that locally applied gels in the vagina can prevent HIV. We wanted to hear that.
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Breakthrough anti-HIV gel
