What is the iPrEx study?

The Chemoprophylaxis for HIV Prevention in Men study, also known as iPrEx, is a Phase III clinical study designed to determine whether a daily tablet containing a combination of two antiretroviral drugs used for HIV treatment can safely and effectively prevent HIV infection among men who have sex with men and transgendered women who have sex with men. The iPrEx study, which began in July 2007, is the National Institute of Allergy and Infectious Diseases’ (NIAID’s) first large-scale study to evaluate the investigational HIV prevention research approach known as pre-exposure prophylaxis, or PrEP.

What is pre-exposure prophylaxis?

Pre-exposure prophylaxis, or PrEP, is an investigational approach to HIV prevention in which antiretroviral medicines currently approved to treat HIV infection are given to people who are not infected with HIV in an attempt to reduce their risk of infection. The concept behind PrEP is not a new one. Drugs are taken to prevent malaria during periods of increased risk and can also be used to reduce the risk of developing tuberculosis and certain types of meningitis.

With HIV, scientists theorize that taking an antiretroviral drug before exposure to HIV could potentially inhibit HIV replication immediately after exposure to the virus, thereby preventing the establishment of permanent infection. There is scientific evidence to support this theory in animal models and humans. Antiretroviral drugs have been successfully used to prevent HIV transmission from infected mothers to their newborns.

How many participants were involved in the iPrEx study, and where was the study conducted?

The iPrEx study enrolled 2,499 sexually active men who have sex with men and transgendered women who have sex with men. All participants were at least 18 years old and HIV-negative at the time of enrollment. All participants were born male (1.2% of participants reported their current gender identity as female).

The study was conducted at 11 sites in nine cities in Brazil, Ecuador, Peru, South Africa, Thailand and the United States.

. Who funded, sponsored and conducted iPrEx?

NIAID sponsored the iPrEx study through a grant to the J. David Gladstone Institutes, a non-profit independent research organization affiliated with the University of California at San Francisco. Additional study funding was provided by the Bill and Melinda Gates Foundation. Gilead Sciences, based in Foster City, Calif., donated the study drug.

The study was conducted under the leadership of protocol chair Robert M। Grant, M.D., M.P.H., of the Gladstone Institute of Virology and Immunology, and protocol co-chair Javier R. Lama, M.D., M.P.H., of Investigaciones Medicas en Salud, a Peruvian-based research organization.