Tenofovir for HIV prevention: gel or tablet

Author:  Shrestha Suvash
Date:  July 2008

The Microbicide Trials Network (MTN) is aiming to compare the tablet and vaginal gel formulations of tenofovir – a widely used Anti retroviral drug (ARV) - as a HIV preventive drug. While researchers are turning to the preventive aspects of ARV, they have chosen this drug as it can be formulated either as an oral tablet or a vaginal gel to be used daily.

MTN-001 is a study designed to evaluate women's compliance to three daily regimens of Tenofovir – 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. The study areas will include the United States, South Africa and Uganda. In the United States, Case Western Reserve University in Cleveland and the University of Pittsburgh are now beginning to screen potential participants.

"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. We 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," said Craig W. Hendrix, M.D., who is the leader of the multi-site study.

Researchers will assess women's adherence to each of the three regimens through structured interviews and questionnaires. Questions will focus on their overall experience using the product regimen, asking how sexual activity may have changed, how well the regimen was adhered to and why the product was not always used - did they forget, dislike using the product or give the tablet or gel to other people? They will also conduct pharmacokinetic studies of blood plasma (the liquid component of blood), white blood cells, and vaginal tissue to see the level of Tenofovir in blood and whether it is in active or inactive form. The study is expected to be completed in 2009.

Tenofovir belongs to a class of ARV called nucleotide reverse transcriptase inhibitors (NRTIs), which act against HIV by targeting a key enzyme the virus needs to make a copy of its genetic material.

Written by Suvash Shrestha

Reviewed by Nadia Ramlagan

Published by Pooja Ghatalia.