The Microbicide Trials Network (MTN) is launching the first clinical trial to directly compare the tablet and vaginal gel formulations of antiretroviral tenofovir.
In part because certain cells in the vagina are easy targets for the virus, women are more than twice as likely as their male partners to acquire HIV through sexual intercourse. As such, the clinical study, known as MTN-001, seeks to understand how each formulation of tenofovir works in these infection-prone cells, information that will help researchers determine the optimal doses needed to achieve drug concentrations most likely to prevent HIV in women.
MTN-001 also looks to understand the factors that influence women’s preferences for one daily approach over another, because not even the best approach will be effective if women don’t use it.
MTN-001 is a phase II study designed to evaluate women’s adherence to and acceptance of three daily regimens of tenofovir â€” tenofovir gel, tenofovir disoproxil fumarate tablets, and the two together – and the pharmacokinetics, or how the drug is absorbed by and distributed in the body over time, of each regimen.
The study will enroll 144 sexually active HIV-negative women who will follow all three regimens, each for six weeks with one week between when no study product is used. In the United States, Case Western Reserve University in Cleveland and the University of Pittsburgh are now beginning to screen potential participants.
Additional sites, including in South Africa and Uganda, will also be participating in the study, which is funded by the National Institute of Allergy and Infectious Diseases, a component of the US National Institutes of Health. Researchers expect to complete the study in 2009.
“Being able to capture in one study, and in all women, information about adherence, acceptability, and pharmacokinetics will help us answer critical questions about the three regimens more efficiently and with greater confidence than we could in separate studies,â€ said Craig W Hendrix MD, associate professor of medicine, Division of Clinical Pharmacology, Johns Hopkins University School of Medicine in Baltimore, Maryland, who, as MTN-001 protocol chair, is leading the multisite study.
â€œWe will be able to more clearly discern the differences between each formulation, including at the cellular level, and get a more accurate reading on women’s preferences and adherence patterns.”