Abstract Body

Antiretroviral medications used as prophlaxis can prevent acquisition of human immunodeficiency virus type 1 (HIV-1).  However, in clinical trials among African women, HIV-1 incidence was not reduced because of low adherence to daily- or coitally-prescribed antiretroviral-containing pills and vaginal gels. Sustained drug-delivery products, including antiretroviral-containing vaginal rings, may improve adherence and provide protection against HIV-1 with lower systemic antiretroviral exposure.

We conducted a randomized, double-blind, placebo-controlled trial of a monthly vaginal ring containing dapivirine, a non-nucleoside HIV-1 reverse transcriptase inhibitor, among women aged 18-45 years in Malawi, South Africa, Uganda, and Zimbabwe.   Dapivirine concentrations in plasma were measured in quarterly-collected samples; levels >95 pg/mL, a concentration nearly always achieved with >8 hours of use, were used to define adherence. Thus, plasma dapivirine could exclude those who were non-adherent but could potentially overestimate adherence if a ring was inserted only several hours before a visit.

A total of 2629 women enrolled.  Their median age was 26 years, median follow-up was 1.6 years, and women attended 91% of expected monthly visits. Among women assigned to the active dapivirine vaginal ring arm, approximately 80% had dapivirine detected in plasma. A total of 168 post-randomization HIV-1 infections occurred: 71 among those assigned the dapivirine vaginal ring (incidence 3.3 per 100 person-years) and 97 among those assigned the placebo ring (incidence 4.5 per 100 person-years).  Compared to those assigned placebo, women assigned the dapivirine ring had a 27% (95% CI 1 to 46, p=0.046) relative reduction in HIV-1 incidence overall, a 37% (95% CI 12 to 56, p=0.007) reduction in an analysis excluding data from two sites with lower retention and adherence, and a 56% (95% CI 31 to 71, p=0.0003) reduction in an as-randomized analysis among women older than 21 years of age. Adherence was lower in women aged 18-21 compared to women older than 21. The rate of adverse medical events was similar between study arms.

A monthly dapivirine vaginal ring was safe and effective for HIV-1 prevention in African women.  This multi-country study is the first to demonstrate HIV-1 protection for a sustained-release approach for delivery of an antiretroviral for HIV-1 prevention. HIV-1 protection was greater in as-randomized subgroups with evidence of better adherence to ring use.