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  ICAAC 2015 55th Interscience Conference
on Antimicrobial Agents and Chemotherapy
September 5-9, 2015, San Diego, CA
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ICAAC: Under 1% in TDF/FTC PrEP Demonstration Projects Picked Up HIV
  ICAAC 2016, June 16-20, 2016, Boston
ASM: HIV-1 Seroconversion Across 17 International Demonstration Projects Using Pre-exposure Prophylaxis (PrEP) With Oral Emtricitabine/Tenofovir Disoproxil Fumarate (FTC/TDF) - (06/22/16)
Mark Mascolini
In 32 preexposure prophylaxis (PrEP) demonstration projects across the world, just under 1% of 8478 participants taking tenofovir/emtricitabine (TDF/FTC) PrEP got infected with HIV yearly [1]. Almost all new infections involved young men who have sex with men (MSM), and MSM made up the largest proportion of demonstration project participants.
In clinical trials of TDF/FTC PrEP, HIV seroconversion rates have ranged from 0.5 per 100 person-years of TDF/FTC exposure in the African Partners PrEP study of HIV-discordant couples to 4.7 per 100 person-years in the FemPrEP and VOICE studies of African women. In studies of MSM, HIV infection rates were 2.2 per 100 person-years in iPrEx, 1.2 per 100 person-years in PROUD, and 0.9 per 100 person-years in IPERGAY, which assessed before-and-after sex PrEP instead of daily PrEP. (A new-HIV rate of 4.7 per 100 person-years means about 5 of every 100 people got infected every year. A rate of 0.9 per 100 person-years means about 1 of every 100 people got infected every year.)
Gilead Sciences researchers assembled and analyzed data from 32 PrEP demonstration projects, which involved nonrandomized PrEP use and risk counseling in communities of people at high risk of HIV infection. Individual groups of investigators not working with Gilead oversight planned and conducted each demonstration project and reported adherence data and new-HIV rates to the FDA. The Gilead analysis focused only on people who took TDF/FTC PrEP in these projects. Thirty of the 32 project began after the FDA licensed TDF/FTC for PrEP in July 2012.
The demonstration projects took place in 16 countries in North America (19 projects), Africa (9), Europe (3), Asia (2), Australia (2), and South America (2). In North America the largest number of projects, 16, involved MSM, 13 involved transgender women, 4 HIV-discordant couples, 3 heterosexual women, 2 heterosexual men, and 1 adolescents. All projects used once-daily PrEP. Together they enrolled 8478 people, including 7002 men, 1378 women, and 76 transgender people.
During 7061 person-years of TDF/FTC exposure, 67 people became infected with HIV for an incidence of 0.95 per 100 person-years (95% confidence interval 0.74 to 1.21). In 17 studies with 2467 participants, no one taking TDF/FTC picked up HIV infection. In 9 projects with 4230 participants, the HIV-seroconversion rate ranged from 0 to 1.5 per 100 person-years. And in 6 projects with 1781 participants, the new-HIV rate lay above 1.5 per 100 person-years and ranged from 1.8 to 7.7 per 100 person-years. The highest seroconversion rate, 7.7 per 100 person-years, came in a project enrolling 18- to 25-year-old MSM.
Of the 67 people who got infected with HIV, 64 were men (rate 1.03 per 100 person-years), 2 were women (0.25 per 100 person-years), and 1 was a transgender woman (2.07 per 100 person-years). Total TDF/FTC exposure rates were 6214 person-years in men, 788 person-years in women, and 48 person-years in transgender women. The 67 people who became infected included 25 blacks, 23 people of mixed race, 14 whites, 1 Asian, and 4 with unreported race. The highest number of seroconversions (29) occurred in the United States, followed by Peru (18), Brazil (5), the UK (5), South Africa (3), Ecuador (3), Australia (1), and Thailand (1).
The age of people who got HIV infection averaged 25.3 years (range 17 to 49). Three infections occurred in the first 30 days of PrEP and 6 in the posttreatment phase. Among 67 people who became infected, researchers had dried blood spot data on tenofovir-diphosphate levels for 32 people. Seventeen of 32 had tenofovir-diphosphate levels below assay detection limits. Fourteen of the remaining 15 people had tenofovir-diphosphate levels consistent with taking fewer than 2 TDF/FTC tablets weekly.
The Gilead team concluded that the overall HIV seroconversion rate of 0.95 per 100 person-years in these PrEP demonstration projects "compares favorably with rates in controlled clinical trials." They underlined the "encouraging" seroconversion rate of 0.25 per 100 person-years in 1388 women enrolled in these projects.
1. McCallister S, Magnuson D, Guzman R, et al. HIV-1 seroconversion across 17 international demonstration projects with pre-exposure prophylaxis (PrEP) with oral emtricitabine/tenofovir disoproxil fumarate (FTC/TDF). ICAAC 2016, June 16-20, 2016, Boston.