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PrEP plus ART yields "near elimination" of HIV in Partners cohort
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CROI 2015, February 23-26, 2015, Seattle, Washington
Mark Mascolini
http://www.croiwebcasts.org/console/player/25541?mediaType=slideVideo&
Preexposure prophylaxis (PrEP) as a bridge to antiretroviral therapy (ART) in HIV-discordant couples--followed by overlapping PrEP and ART then ART alone--lowered the HIV transmission rate to 0.2 per 100 person-years in an observational demonstration project [1]. That rate indicates "near elimination" of HIV transmission, according to the Partners in Prevention team that conducted this study.
PrEP and ART have both proved successful in preventing HIV transmission in HIV-discordant heterosexual African couples (one partner positive, one negative). Jared Baeten and Partners in Prevention colleagues conducted the Partners Demonstration Project to test the feasibility and value of combining the strategies sequentially in an open-label prospective study.
From November 2012 through August 2014, the investigators enrolled more than 1000 HIV-discordant couples in Kenya and Uganda. They rated couples at high risk for HIV transmission with a validated risk-scoring tool [2]. The positive partner had not yet begun ART and the negative partner had not taken PrEP. During the observation period, national guidelines recommended ART for people with a CD4 count below 350 and then for all positive partners in discordant couples regardless of CD4 count. The HIV-negative partner began daily tenofovir/emtricitabine PrEP and continued until the positive partner had taken ART for 6 months.
The investigators modeled HIV incidence in study populations with data from the placebo arm of the Partners PrEP trial [3], which involved HIV-discordant couples at the same study sites. Couples selected for the simulation model had a distribution of HIV risk scores and follow-up duration identical to couples in the Partners Demonstration Project.
The discordant couples followed had a median age of 30 years, and 67% of HIV-negative partners were men. Two thirds of couples reported sex without condoms in the past month. Median CD4 count of positive partners stood at 436 (interquartile range [IQR] 272 to 638), and 41% had a CD4 count topping 500. Median viral load of positive partners measured 37,096 copies (IQR 7058 to 104,462), and 41% had a viral load above 50,000 copies. Slightly more than half of couples had no children together.
At this report 858 person-years of follow-up had accumulated, 42% of target person-years in this ongoing study. Retention stands above 85% at each quarterly visit. More than 95% of negative partners have begun PrEP, and adherence is high. About 80% of HIV-positive partners have begun ART, and more than 90% have reached an undetectable viral load. During 48% of accrued follow-up time, couples have used PrEP before ART, while PrEP and ART overlapped during 27% of the time, ART was used alone 16% of the time, and neither was used 9% of the time.
The simulation model predicted 39.7 infections during the observation period for an incidence of 5.2 per 100 person-years (95% confidence interval [CI] 3.7 to 6.9), meaning 5 of 100 people would be infected every year. In Partners Demonstration Project couples, only 2 people became infected for an incidence of 0.2 per 100 person-years (95% CI 0.0 to 0.9). The incidence rate ratio for observed versus expected infections came to 0.04 (95% CI 0.01 to 0.19), indicating a 96% reduction in HIV incidence (95% CI 81% to 99%, P < 0.0001). The two people who became infected in the demonstration project, both women, had evidence of limited PrEP use.
Baeten and colleagues observed that their Partners Demonstration Project "differs substantially from randomized trials of PrEP and ART in its open-label, implementation science approach and its focused recruitment of higher-risk couples."
They believe their results "demonstrate that PrEP as a bridge to ART is not only feasible but highly effective in preventing HIV transmission in this population." The team suggested that their findings may also be relevant to other high-risk populations, including gay and bisexual men and women at risk.
References
1. Baeten J, Heffron R, Kidoguchi L, et al. Near elimination of HIV transmission in a demonstration project of PrEP and ART. CROI 2015. February 23-26, 2015. Seattle, Washington. Abstract 24.
2. Kahle EM, Hughes JP, Lingappa JR, et al. An empiric risk scoring tool for identifying high-risk heterosexual HIV-1-serodiscordant couples for targeted HIV-1 prevention. J Acquir Immune Defic Syndr. 2013;62:339-347. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3620695/
3. Baeten JM, Donnell D, Ndase P, et al. Antiretroviral prophylaxis for HIV prevention in heterosexual men and women. N Engl J Med. 2012;367:399-410.
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