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Microbicides Against HIV

April 22, 2015

Microbicides Against HIV

Table of Contents

What Are Microbicides?

Microbicides are products being developed to reduce the spread of HIV and other sexually transmitted diseases (STDs). Microbicides could come in many forms, including gels, creams, suppositories, films, lubricants, sponges, or vaginal rings. They could be used in the vagina or rectum.

How Would Microbicides Work?

Microbicides could work in different ways:

  1. Killing germs such as bacteria and viruses or making them inactive
  2. Changing the condition of the vagina or rectum to make infection less likely
  3. Blocking infection by creating a barrier between the germ and the cells of the vagina or rectum
  4. Preventing the germ from spreading after it has entered the body

Are Microbicides Currently Available?

No. Scientists are testing many products to see whether they help protect against infection with HIV and/or other STDs. Some of these products have proven safe enough in lab studies that they are now being tested in people. However, no safe and effective microbicide is currently available to the public.

What Is Happening in Microbicide Research?

Microbicides have been in development for over 15 years. A number of studies conducted on the early products failed to find an effective microbicide.

However, there is hope that a new group of microbicides that contain HIV drugs will be more effective. Unlike earlier products, these newer microbicides do not have to be applied at the time of sex. They may be used daily as a gel or possibly as a vaginal ring that may only need to be inserted once a month.


Vaginal and Rectal Gels

Promising results were reported a few years ago from a study of HIV-negative women in South Africa. It showed that when women used a one percent gel version of the HIV drug Viread (tenofovir) inside the vagina, two out of every five HIV infections were prevented. These study results provide early proof that HIV drug-based microbicides, in particular tenofovir gel, can help protect women against HIV.

Unfortunately, a similar study of tenofovir one percent vaginal gel among over 5000 HIV-negative women in Uganda, South Africa, and Zimbabwe was not successful. This study, called the VOICE study (MTN 003), was stopped in the fall of 2011 because it did not work to prevent HIV infections. The gel did not work largely because women did not use it as directed. However, the tenofovir gel appeared to be safe, without major side effects. While it is encouraging that tenofovir-containing gels appear effective when used as directed, researchers will be shifting their focus to understanding why so few women choose to use these gels so that more acceptable and effective prevention methods can be identified.

Researchers are also testing a version of tenofovir gel designed for rectal use. This study (MTN 017) is exploring the safety and acceptance of the rectal gel in transgender women and men who have sex with men in Peru, South Africa, Thailand, and the US. Results are expected in early 2016.

Vaginal Rings

There is also hope that vaginal rings containing HIV drugs can prevent the spread of HIV. The ring is flexible and will be placed deep inside the vagina against the cervix (entrance to the womb), where it stays for several weeks. The benefit of using a vaginal ring compared to a vaginal gel is that women would not have to insert the microbicide ring as often as the gel.

Two studies, the ASPIRE study (MTN 020) and the Ring Study (IPM 027), have been looking at the effectiveness of a vaginal ring containing an HIV drug called dapivirine (a non-nucleoside reverse transcriptase inhibitor) to prevent the spread of HIV. The Ring Study is looking at the effect of the ring in almost 2000 women from South Africa and Uganda.

The ASPIRE study looked at the dapivirine ring's effects in over 3000 women from Malawi, South Africa, Uganda, and Zimbabwe. It also tested a vaginal ring containing a combination of two HIV drugs -- dapivirine and Selzentry (maraviroc) -- and a ring containing only Selzentry. While all the rings were safe and well-tolerated by study participants, only the dapivirine appeared to prevent HIV infection in cervical cells.

Vaginal Films

Scientists in the FAME-02 study found that a vaginal film containing dapivirine delivered enough drug to vaginal tissue to prevent HIV infection when tested in the laboratory.

Multipurpose Prevention Technologies

Multipurpose Prevention Technologies (MPTs) provide ways of preventing more than one thing in one device. For example, MPTs may prevent pregnancy and HIV, or they may prevent HIV and several other STDs. Having methods that combine prevention of pregnancy and STDs (including HIV) would be more convenient and likely lead to more consistent and therefore more effective use.

Researchers are studying several methods for combining prevention technologies, including a vaginal ring containing both a hormonal contraceptive (to prevent pregnancy) and an HIV drug (to prevent HIV; a form of Pre-Exposure Prophylaxis, or PrEP). It can be inserted well before sex, stay there for up to three months, and is not usually felt by either partner. Early studies have shown that the ring appears to be effective in preventing monkeys from getting HIV and from getting pregnant. The next step is for the ring to be tested in women in clinical research trials.

Would Microbicides Eliminate the Need for Condoms?

No. When used consistently and correctly, male or female condoms are likely to provide better protection against HIV and other STDs than microbicides, so they are still the best choice. But for people who do not have access to condoms, or who cannot or will not use condoms, microbicides would provide another option. This is especially true for women whose male partners refuse to use condoms. Microbicides could be used without the knowledge of women's sexual partners, thereby putting the power of prevention directly in women's hands. Using microbicides could save lives and have a major impact in reducing the spread of HIV.

Would Microbicides Protect Against All STDs?

Many of the microbicides being tested work against HIV. In time, a product may be developed that combines different microbicides and could prevent a wide range of STDs, including HIV (see multipurpose prevention technologies, or MPTs, above).


What if a Woman Wants to Get Pregnant?

Some of the microbicides being studied would allow a woman to get pregnant. These are called non-contraceptive microbicides. They would offer women the option of getting pregnant while still protecting themselves from infection – an option that is not available with condom use. The tenofovir one percent gel tested in the CAPRISA 004 study and mentioned above is one example of a non-contraceptive microbicide. Contraceptive microbicides would prevent pregnancy and STDs, including HIV. It is important to have both types available.

Would Microbicides Be Safe?

Any new product must go through strict safety testing before becoming available to the public. Health activists and researchers are closely watching over the clinical testing of microbicides to make sure that the testing is being done correctly.

How Would Microbicides Benefit Men?

It is possible that the male partner of a woman living with HIV might be protected from infection if she used a vaginal or rectal microbicide. However, this would need to be tested in clinical trials. The safety and effectiveness of vaginal microbicides must be tested separately from rectal microbicides.

How Would Microbicides Benefit Women With HIV?

Microbicides could help protect HIV+ women from re-infection with other HIV strains and from other STDs.

Why Do We Need Microbicides if We Will Eventually Have a Vaccine to Prevent HIV?

Research on developing a vaccine to prevent HIV infection has not been successful so far. Microbicides may be available sooner than a preventive HIV vaccine. Even if a safe and effective vaccine is discovered, vaccines and microbicides will both have roles to play in the prevention of HIV.

How Much Will Microbicides Cost, and Will People Be Able to Afford Them?

Advocates are working with researchers and policy makers to make sure that any approved microbicide will be as affordable and accessible as possible.

What About Nonoxynol-9 (N-9)?

N-9 products are sold over the counter as spermicides that can prevent pregnancy. They cannot prevent the transmission of HIV or other infections. In fact, when used more than once a day, N-9 contraceptive products may actually increase HIV risk by irritating the lining of the vagina. Other studies show that N-9 is even more irritating to the rectum than to the vagina.

According to the World Health Organization (WHO):

Taking Care of Yourself

Until microbicides are available, the best way to protect yourself and your partner from STDs, including HIV, is to use a male or female condom. It is also important to avoid the use of nonoxynol-9 (N-9) products if you think there is any chance you may be exposed to HIV. Getting tested for STDs regularly and getting treatment quickly if you have an STD will also help reduce your risk of HIV infection if you are exposed to HIV.

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