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Correlates of Sex-Related Pre-exposure Prophylaxis Adherence, Thai Men Who Have Sex With Men, and Transgender Women, 2012–2013

Holtz, Timothy H. MD, MPHa,b; Chitwarakorn, Anupong MDc; Hughes, James P. PhDd,e; Curlin, Marcel E. MDa,b,f; Varangrat, Anchalee MAa; Li, Maoji MSe; Amico, K. Rivet PhDg; Mock, Philip A. MAppStatsa; Grant, Robert M. MDh the Thai HPTN 067/ADAPT Study Team

JAIDS Journal of Acquired Immune Deficiency Syndromes: October 1, 2019 - Volume 82 - Issue 2 - p e18–e26
doi: 10.1097/QAI.0000000000002131
Prevention Research

Background: We identified correlates of sex-related pre-exposure prophylaxis (PrEP) adherence in HPTN067/ADAPT, a phase 2, open-label feasibility study of daily and nondaily regimens of emtricitabine/tenofovir disoproxil fumarate (FTC/TDF)-based PrEP, among Thai men who have sex with men (MSM), and transgender women (TGW), Bangkok.

Methods: Participants were randomly assigned to one of three self-administered dosing regimens for 24 weeks: daily, time-driven, or event-driven. Demographic and behavioral information was obtained at screening. Pill-container opening was recorded with electronic dose monitoring, and self-reported information on PrEP use, sex events, and substance use was obtained during weekly interviews to confirm dose data. Sex-related PrEP adherence was calculated as the proportion of sex events covered by PrEP use (at least one tablet taken within 4 days before sex and at least one tablet taken within 24 hours after sex) to total sex events. We used multivariate modeling with sex event as the unit of analysis to evaluate correlates associated with sex-related PrEP adherence.

Results: Among 178 MSM and TGW, sex-related PrEP adherence was similar in the daily and time-driven arms (P = 0.79), both significantly greater than the event-driven arm (P = 0.02 compared to daily). Sex-related PrEP adherence by those reporting stimulant use (74.2%) was similar to those reporting other nonalcohol drug use (76.3%, P = 0.80), but lower than those reporting no substance use (84.6%, P = 0.04). In a multivariable model, randomization to the event-driven arm, a higher prestudy number of reported sex events, and use of stimulant drugs were associated with significantly lower sex-related PrEP adherence.

Conclusion: Adherence was influenced by treatment schedule and adversely affected by nonalcoholic substance use. Regardless of these factors, Thai MSM and TGW maintained high adherence levels to oral PrEP dosing regimens and coverage of sexual exposures.

aThailand Ministry of Public Health-U.S., Centers for Disease Control and Prevention Collaboration, Nonthaburi, Thailand;

bDivision of HIV/AIDS Prevention, Centers for Disease Control and Prevention, Atlanta, GA;

cDepartment of Disease Control, Ministry of Public Health, Nonthaburi, Thailand;

dDepartment of Biostatistics, University of Washington, Seattle, WA;

eVaccine and Infectious Diseases Division, Fred Hutchinson Cancer Research Center, Seattle, WA;

fDepartment of Medicine, Oregon Health Sciences University, Portland, OR;

gDepartment of Health Behavior and Health Education, School of Public Health, University of Michigan, Ann Arbor, MI;

hDepartment of Medicine, University of California, San Francisco, CA.

Correspondence to: Timothy H. Holtz, MD, MPH, Office of AIDS Research, National Institutes of Health, 5601 Fishers Lane, Rockville, MD 20892-9840 (e-mail:

Supported by the HIV Prevention Trials Network (HPTN), sponsored by the National Institute of Allergy and Infectious Diseases (NIAID), the National Institute on Drug Abuse (NIDA), the National Institute of Mental Health (NIMH), and the Office of AIDS Research of the National Institutes of Health (NIH), Department of Health and Human Services (DHHS) [Grant numbers UM1AI068613, UM1AI068617, and UM1AI068619]. Gilead Sciences donated study medication to the NIH to support this study. This work was also supported in part by the Emory-CDC HIV/AIDS Clinical Trials Unit Grant award number UM1AI069418 from the NIH (NIAID). The funder of the study reviewed and commented on the study protocol and final manuscript written by the study investigators. The corresponding author had full access to all the data in the study and had final responsibility for the decision to submit for publication. The study sponsor reviewed and approved of the study protocol and of this article. The study sponsor had no role in the analysis or interpretation of the data or in writing of this article.

Presented in part at Conference on Retroviruses and Opportunistic Infections (CROI 2016); February 22–25, 2016; Boston, MA, and 9th IAS Conference on HIV Pathogenesis, Treatment and Prevention (IAS 2017); July 23–26, 2017; Paris, France.

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional research committee and with the 1975 Helsinki Declaration and its later amendments (2000) or comparable ethical standards.

The protocol was approved by the Ethical Review Committee for Research in Human Subjects of the Thailand Ministry of Public Health, and by Institutional Review Boards of the U.S. CDC and Columbia University Medical Center. The protocol was registered at (identifier NCT01327651;

Informed consent was obtained from all individual participants included in the study.

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the CDC.

The authors have no conflicts of interest to disclose.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (

Received December 19, 2018

Accepted May 29, 2019

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