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PLoS One. 2017 Jul 27;12(7):e0181607. doi: 10.1371/journal.pone.0181607. eCollection 2017.

High levels of adherence to a rectal microbicide gel and to oral Pre-Exposure Prophylaxis (PrEP) achieved in MTN-017 among men who have sex with men (MSM) and transgender women.

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HIV Center for Clinical and Behavioral Studies at New York State Psychiatric Institute and Columbia University, New York, NY, United States of America.
Center for AIDS Prevention Studies, Department of Medicine, University of California San Francisco, San Francisco, CA, United States of America.
Department of Medicine, Johns Hopkins University, Baltimore, MD, United States of America.
Division of AIDS, National Institute of Allergy and Infectious Diseases, Rockville, MD, United States of America.
Department of Biostatistics, University of Washington, Seattle, WA, United States of America.
National Institute of Mental Health, Bethesda, MD, United States of America.
FHI 360, Durham, NC, United States of America.
Magee-Womens Research Institute, Pittsburgh, PA, United States of America.
Statistical Center for HIV/AIDS Research and Prevention, Seattle, WA, United States of America.
Desmond Tutu HIV Centre, University of Cape Town, Cape Town, South Africa.
Research Institute for Health Sciences, Chiang Mai University, Chiang Mai, Thailand.
Thailand Ministry of Public Health, Nonthaburi, Thailand.
Asociación Civil Impacta Salud y Educación, Lima, Peru.
Thailand Ministry of Public Health-Centers for Disease Control Collaboration, Bangkok, Thailand.
San Francisco Department of Public Health, San Francisco, CA, United States of America.
The Fenway Institute, Boston, MA, United States of America.
Department of Medicine, University of Puerto Rico, San Juan, PR, United States of America.
School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States of America.


Trials to assess microbicide safety require strict adherence to prescribed regimens. If adherence is suboptimal, safety cannot be adequately assessed. MTN-017 was a phase 2, randomized sequence, open-label, expanded safety and acceptability crossover study comparing 1) daily oral emtricitabine/tenofovir disoproxil fumarate (FTC/TDF), 2) daily use of reduced-glycerin 1% tenofovir (RG-TFV) gel applied rectally, and 3) RG-TFV gel applied before and after receptive anal intercourse (RAI)-if participants had no RAI in a week, they were asked to use two doses of gel within 24 hours. Product use was assessed by mixed methods including unused product return count, text messaging reports, and qualitative plasma TFV pharmacokinetic (PK) results. Convergence interviews engaged participants in determining the most accurate number of doses used based on product count and text messaging reports. Client-centered adherence counseling was also used. Participants (N = 187) were men who have sex with men and transgender women enrolled in the United States (42%), Thailand (29%), Peru (19%) and South Africa (10%). Mean age was 31.4 years (range 18-64 years). Based on convergence interviews, over an 8-week period, 94% of participants had ≥80% adherence to daily tablet, 41% having perfect adherence; 83% had ≥80% adherence to daily gel, 29% having perfect adherence; and 93% had ≥80% adherence to twice-weekly use during the RAI-associated gel regimen, 75% having perfect adherence and 77% having ≥80% adherence to gel use before and after RAI. Only 4.4% of all daily product PK results were undetectable and unexpected (TFV concentrations <0.31 ng/mL) given self-reported product use near sampling date. The mixed methods adherence measurement indicated high adherence to product use in all three regimens. Adherence to RAI-associated rectal gel use was as high as adherence to daily oral PrEP. A rectal microbicide gel, if efficacious, could be an alternative for individuals uninterested in daily oral PrEP.

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