PRO 2000 is the name of an experimental vaginal microbicide

Vaginal microbicide

A vaginal microbicide is a microbicide for vaginal use. Most commonly such a product would be a topical gel or cream inserted into the vagina so that it may treat some infection in the vagina, such as types of vaginitis....

 which has been proposed as a preventative medicine for reducing the risk of contracting HIV

HIV

Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

. It has never been recommended as an effective medicine to be used for any purpose. Some clinical trials have shown that under some conditions it may provide some protection against HIV.

Efficacy

Animal testing

Animal testing

Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals in experiments. Worldwide it is estimated that the number of vertebrate animals—from zebrafish to non-human primates—ranges from the tens of millions to more than 100 million...

 studies done on macaques have shown that PRO 2000 is effective in preventing the transmission of HIV. Other studies have given supportive evidence that the product is safe in humans and would be an appropriate candidate for testing.

One study of 9385 women in sub-Saharan Africa

Sub-Saharan Africa

Sub-Saharan Africa as a geographical term refers to the area of the African continent which lies south of the Sahara. A political definition of Sub-Saharan Africa, instead, covers all African countries which are fully or partially located south of the Sahara...

showed that PRO 2000 was not effective in preventing HIV.