The study also showed no sign of tenofovir resistance in women who became infected despite use of the drug, a benign adverse effect profile, no safety issues in pregnancy, and no increase in HIV risk behavior. During the study, all women received regular counseling that reinforced the need for condom use whenever possible. The purpose of the gel was to give women protection when a condom wasn't used.
A pharmacology study showed very low concentrations of tenofovir appearing in the women’s blood, while high levels of tenofovir in cervicovaginal fluid linked with better HIV protection.
"I was very struck by the lack of any degree of [HIV] resistance from the topical application of this drug. That was encouraging" said Dr. Fauci. "And the concentrations in the vagina tell you that you’re getting a real whopper of an effect locally." He speculated that tenofovir penetrates the mucosal surface of the vagina and enters submucosal dendritic and T cells where it blocks HIV replication and thus prevents infection from starting.
Dr. Salim S. Abdool Karim and Dr. Quarraisha Abdool Karim said that they had no conflicts. Gilead, which supplied the tenofovir gel, licensed its use in Africa to CONRAD, a nongovernmental organization in Arlington, Va.