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Early ART Cuts HIV Transmission Rate 93% Through 2015 in HPTN 052
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IAS 2015, July 19-22, 2015, Vancouver
Mark Mascolini
At the end of follow-up in the landmark HPTN 052 trial, starting antiretroviral therapy (ART) early in HIV-positive partners of HIV-discordant couples sliced the transmission risk 93% [1]. That result varies little from the 96% risk reduction at the previously reported end of the blinded phase of this 1763-couple trial [2]. The final HPTN 052 analysis presented at IAS 2015 follows participants after interim analysis showed the overwhelming advantage of early versus delayed ART and HIV-positive partners in the delayed arm were offered immediate ART.
The trial enrolled 1763 HIV-discordant couples in Malawi, Zimbabwe, South Africa, Botswana, Kenya, Thailand, India, Brazil, and the United States, 97% of them heterosexual. HIV-positive partners, all with a CD4 count between 350 and 550, got randomized to immediate ART (the early arm) or to wait until their CD4 count fell to 250 or an AIDS illness developed (the delayed arm). Through February 2011, the HPTN team counted 28 new HIV infections in previously negative partners that could be genetically linked to the positive partner. Only 1 of those infections occurred in the early ART arm (P < 0.001). At that point all HIV-positive partners in the delayed arm got the option to start ART and the study continued until May 2015.
Of the 1763 HIV-positive people initially enrolled, 96% remained in the trial in 2011 and 87% remained through May 2015. Similar proportions from the early and delayed arms stayed in the trial through 2015. At the end of the study, only 2% of HIV-positive people in the delayed arm still declined ART.
From May 2011 through May 2015, researchers counted 32 new infections in initially HIV-negative partners, 9 of which could be linked to positive partners. Two of these linked infections occurred in the early ART arm and 7 in the delayed ART arm. Those numbers translated into a 72% risk reduction from May 2011 through May 2015.
In the overall analysis, from April 2005 through May 2015, 78 initially negative partners became infected with HIV, and 46 of those infections could be linked to the positive partner. Three of those 46 linked infections occurred in the early ART arm and 43 in the delayed ART arm for an overall transmission risk reduction of 93%.
Eight linked partner infections got diagnosed after the initially positive partner started ART. Four linked infections probably occurred before or soon after the initially positive partner started ART, and 4 occurred after ART failed in an initially positive partner. No linked HIV transmissions happened when the treated participant had an undetectable viral load during ART.
The investigators concluded that "the benefit of early ART in HIV prevention among HIV-discordant couples is durable" and that "ART is highly effective for prevention of sexual transmission of HIV."
References
1. Cohen M, Chen Y, McCauley M, et al. Final results of the HPTN 052 randomized controlled trial: antiretroviral therapy prevents HIV transmission. IAS 2015. 8th Conference on HIV Pathogenesis, Treatment and Prevention. July 19-22, 2015. Vancouver. Abstract MOAC0101LB.
2. Cohen MS, Chen YQ, McCauley M, et al. Prevention of HIV-1 infection with early antiretroviral therapy. N Engl J Med. 2011;365:493-505.
http://www.nejm.org/doi/full/10.1056/NEJMoa1105243
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