Microbicides Against HIV
March 1, 2017
Table of Contents
Microbicides are products being developed to reduce the spread of HIV and other sexually transmitted infections or diseases (STIs or 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.
Microbicides could work in different ways:
No. Scientists are testing many products to see whether they help protect against infection with HIV and/or other sexually transmitted infections. 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.
Microbicides have been in development for more than 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. These microbicides come in several different forms -- gels, rings, films -- and may serve as multipurpose prevention technologies (MPTs), which address two or more sexual health issues at one time (e.g., HIV and pregnancy).
There is also hope that vaginal rings containing HIV drugs can prevent the spread of HIV. The ring is flexible and can be inserted by the woman herself deep inside the vagina against the cervix (entrance to the womb). The ring is comfortable and rarely felt by the woman herself or her sexual partner(s). It needs to be replaced once every one to two months. This is different from vaginal gels, which need to be inserted directly before or at the time of a sexual act. Women are in control of the use of both rings and gels. However, with the ring, women do not need to plan for sex, which can allow sex to be more spontaneous.
One of the largest announcements at the 2016 Conference on Retroviruses and Opportunistic Infections involved results from two studies that looked at the effectiveness of an intravaginal dapivirine-containing ring. The two studies -- the ASPIRE study and The Ring Study -- enrolled more than 4,500 HIV-negative women in South Africa, Uganda, Malawi, and Zimbabwe ages 18 to 45 years. They shared a very similar design, which assigned half of participants to receive a ring containing the study drug -- dapivirine, a non-nucleoside reverse transcriptase inhibitor (NNRTI) -- and half to receive a ring containing no dapivirine (the placebo). The rings were inserted into the vagina every month for two years.
Both studies showed a modest reduction in HIV infection among women who used the dapivirine ring. The trials were also similar in that younger women saw little or no benefit from using the ring. The difference in effectiveness in age groups has to do with adherence. Younger women were less adherent in using the ring, and consequently saw less protective benefit. Interestingly, adherence increased over time, suggesting that women may have needed some time to become familiar with the new technology.
As a result, researchers are now conducting open-label extensions on The Ring and ASPIRE studies. These extension trials are designed to gather information about how the ring works for women who are aware of its potential benefit and may shed some light on challenges with adherence.
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 more than 5,000 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 also tested a version of tenofovir gel designed for rectal use. This study (MTN 017) explored 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. It found that the rectal gel was safe and well-tolerated, and that participants were highly adherent overall. Adherence was higher among those who used the product before and after sex compared to those who used it on a daily basis.
Rectal gels containing dapivirine and maraviroc are currently in development and under investigation. Scientists are also studying vaginal gels containing dapivirine, dapivirine plus maraviroc, and dapivirine plus darunavir.
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. Study of a vaginal film containing dapivirine is ongoing.
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 STIs. Having methods that combine prevention of pregnancy and STIs (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. Vaginal gels that may prevent pregnancy and HIV are also under investigation.
This article was provided by The Well Project. Visit The Well Project's Web site to learn more about their resources and initiatives for women living with HIV. The Well Project shares its content with TheBody.com to ensure all people have access to the highest quality treatment information available. The Well Project receives no advertising revenue from TheBody.com or the advertisers on this site. No advertiser on this site has any editorial input into The Well Project's content.
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