An experimental laboratory study of macaque monkeys has shown the efficacy of a vaginal ring impregnated with a potent microbicide, a molecule called MIV-150, which acts by blocking an enzyme necessary for HIV to pass from one cell to another and spread throughout the body.

To carry out the study, they used 33 macaques that they divided into two groups; one of the groups was given the vaginal ring fitted with the microbicidal agent, and the other one with a placebo ring. The scientists tried to supply the rings, either two weeks before infecting the animals with a combination of human HIV virus and SIV -version of the virus to the monkeys-, only 24 hours before infection, to see if there were differences in as to the level of protection offered by the new device.

The vaginal microbicidal ring showed an efficacy of 83% protection against HIV

They also analyzed the effectiveness of the ring if it was removed immediately after exposure to the virus, or if they waited two weeks to extract it. The vaginal microbicidal ring showed an efficacy of 83% protection against HIV, but part of that protection was lost when it was removed before exposure, even though the drug with which they impregnated the devices is able to penetrate the tissues 30 minutes after insertion. The conclusion of the researchers is that in order to achieve the best protection against HIV, it is essential that the ring be present before, during and after exposure to the virus.

A vaginal ring that releases a drug with an adequate antiviral power would be a great advantage to prevent the transmission of AIDS, because one of the problems faced by current prevention policies is that the population is not constant when using protective barriers such as condoms or microbicidal gels before having sex, and the vaginal ring, once inserted, does not require daily attention, nor do you need to do anything before intercourse, making it easier for women to adhere to this treatment.

The results of the research, which has been published in 'Science Translational Medicine', have been welcomed with hope by scientists, who have been looking for a substance that can be applied to the vagina or rectum for over 20 years and avoid infection. for HIV when the person has a sexual relationship that may involve risk of infection. However, there is still a long way to go, as new clinical trials are needed to test whether the vaginal ring with microbicidal function is equally effective in humans.

The Promise of the Ring for HIV Prevention for Women (November 2019).