The dapivirine ring confers moderate efficacy, but hope for a new prevention option

Use of a vaginal ring containing dapivirine for HIV-1 prevention in women.

Baeten JM, Palanee-Phillips T, Brown ER, Schwartz K, Soto-Torres LE, Govender V, Mgodi NM, Matovu Kiweewa F, Nair G, Mhlanga F, Siva S, Bekker LG, Jeenarain N, Gaffoor Z, Martinson F, Makanani B, Pather A, Naidoo L, Husnik M, Richardson BA, Parikh UM, Mellors JW, Marzinke MA, Hendrix CW, van der Straten A, Ramjee G, Chirenje ZM, Nakabiito C, Taha TE, Jones J, Mayo A, Scheckter R, Berthiaume J, Livant E, Jacobson C, Ndase P, White R, Patterson K, Germuga D, Galaska B, Bunge K, Singh D, Szydlo DW, Montgomery ET, Mensch BS, Torjesen K, Grossman CI, Chakhtoura N, Nel A, Rosenberg Z, McGowan I, Hillier S, Team M-AS N Engl J Med. 2016 Feb 22. [Epub ahead of print]

Background: Antiretroviral medications that are used as prophylaxis can prevent acquisition of human immunodeficiency virus type 1 (HIV-1) infection. However, in clinical trials among African women, the incidence of HIV-1 infection was not reduced, probably because of low adherence. Longer-acting methods of drug delivery, such as vaginal rings, may simplify use of antiretroviral medications and provide HIV-1 protection.

Methods: We conducted a phase 3, randomized, double-blind, placebo-controlled trial of a monthly vaginal ring containing dapivirine, a non-nucleoside HIV-1 reverse-transcriptase inhibitor, involving women between the ages of 18 and 45 years in Malawi, South Africa, Uganda, and Zimbabwe.

Results: Among the 2629 women who were enrolled, 168 HIV-1 infections occurred: 71 in the dapivirine group and 97 in the placebo group (incidence, 3.3 and 4.5 per 100 person-years, respectively). The incidence of HIV-1 infection in the dapivirine group was lower by 27% (95% confidence interval [CI], 1 to 46; P=0.05) than that in the placebo group. In an analysis that excluded data from two sites that had reduced rates of retention and adherence, the incidence of HIV-1 infection in the dapivirine group was lower by 37% (95% CI, 12 to 56; P=0.007) than that in the placebo group. In a post hoc analysis, higher rates of HIV-1 protection were observed among women over the age of 21 years (56%; 95% CI, 31 to 71; P<0.001) but not among those 21 years of age or younger (-27%; 95% CI, -133 to 31; P=0.45), a difference that was correlated with reduced adherence. The rates of adverse medical events and antiretroviral resistance among women who acquired HIV-1 infection were similar in the two groups.

Conclusions: A monthly vaginal ring containing dapivirine reduced the risk of HIV-1 infection among African women, with increased efficacy in subgroups with evidence of increased adherence.

 Abstract [1] Full-text [free] access  [2]

Editor’s notes: Women bear a larger proportion of the HIV burden worldwide due to biological and behavioural factors. As a result, the HIV prevention field has focused research over the past couple of decades to identify new prevention options especially for women, to reduce this burden. The study presented in this paper is the first to publish phase III efficacy trial results for a vaginal ring containing the antiretroviral drug dapivirine for HIV prevention. The ring is designed to prevent HIV acquisition locally within the vagina in HIV negative women and kept in the body for a period of four weeks. This strategy is meant to address two components of adherence and side effects. A longer-acting product and local application is contrasted with the daily and systemic use of oral pre-exposure prophylaxis, a regimen which can be difficult to maintain. This study found that the dapivirine ring did not protect women with a high rate of efficacy, 27% overall. Interestingly, the sub-analyses of the data illustrated that there was better protection in women with better adherence, and in women who were over the age of 21. Further explorations of the data along with the qualitative findings from the study will surely provide more valuable insights into the low overall rate of efficacy, and perhaps most importantly into why age made such a difference in rates of protection. As mentioned in the paper, a second study on the ring, which was presented at CROI 2016, publishing similar results, and those results combined with the data from this study will further our knowledge regarding the viability of this HIV prevention option.  

Africa [6]
Malawi [7], South Africa [8], Uganda [9], Zimbabwe [10]
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