Results of MTN-001, a pharmacokinetics study comparing absorption rates of vaginal tenofovir gel versus oral tablets, were published in the January 30th, 2013 issue of PLoS ONE. The open label 3-period crossover study involved 144 HIV-uninfected women at 7 clinical research sites in the U.S and Africa. The women participated in 3 different daily tenofovir regimens, each for 6 weeks on either oral tenofovir, vaginal tenofovir 1% gel, or both. The study found that serum concentrations after vaginal dosing were lower than after oral dosing and vaginal tissue tenofovir diphosphate was ≥130-fold higher with vaginal compared to oral dosing. The study conclusion stated: “Compared to oral dosing, vaginal dosing achieved much lower serum concentrations and much higher vaginal tissue concentrations.”
CONRAD conducted the first pharmacokinetic study of tenofovir gel, which was published in PLoS ONE in 2011, and was the first to measure the active form of the drug in the genital tissue. The evidence suggests that tenofovir gel can achieve protective concentrations if women use it as instructed. CONRAD is currently sponsoring a Phase III clinical trial called FACTS 001, which is studying the efficacy of vaginal tenofovir gel when used before and after sex, as well as another pharmacokinetic study assessing vaginal and systemic levels of tenofovir with different gel dosing regimens: before and after sex, before sex, after sex, and daily. This ongoing study is fully enrolled at 5 clinical research sites in the U.S. and the Dominican Republic.