Thai PrEP Open-label study illustrates better adherence in people at higher risk of HIV

Factors associated with the uptake of and adherence to HIV pre-exposure prophylaxis in people who have injected drugs: an observational, open-label extension of the Bangkok Tenofovir Study.

Martin M, Vanichseni S, Suntharasamai P, Sangkum U, Mock PA, Chaipung B, Worrajittanon D, Leethochawalit M, Chiamwongpaet S, Kittimunkong S, Gvetadze RJ, McNicholl JM, Paxton LA, Curlin ME, Holtz TH, Samandari T, Choopanya K, on behalf of the Bangkok Tenofovir Study Group. Lancet HIV. 2017 Feb;4(2):e59-e66. doi: 10.1016/S2352-3018(16)30207-7. Epub 2016 Nov 18.

Background: Results of the randomised, double-blind, placebo-controlled Bangkok Tenofovir Study (BTS) showed that taking tenofovir daily as pre-exposure prophylaxis (PrEP) can reduce the risk of HIV infection by 49% in people who inject drugs. In an extension to the trial, participants were offered 1 year of open-label tenofovir. We aimed to examine the demographic characteristics, drug use, and risk behaviours associated with participants' uptake of and adherence to PrEP.

Methods: In this observational, open-label extension of the BTS (NCT00119106), non-pregnant, non-breastfeeding, HIV-negative BTS participants, all of whom were current or previous injecting drug users at the time of enrolment in the BTS, were offered daily oral tenofovir (300 mg) for 1 year at 17 Bangkok Metropolitan Administration drug-treatment clinics. Participant demographics, drug use, and risk behaviours were assessed at baseline and every 3 months using an audio computer-assisted self-interview. HIV testing was done monthly and serum creatinine was assessed every 3 months. We used logistic regression to examine factors associated with the decision to take daily tenofovir as PrEP, the decision to return for at least one PrEP follow-up visit, and greater than 90% adherence to PrEP.

Findings: Between Aug 1, 2013, and Aug 31, 2014, 1348 (58%) of the 2306 surviving BTS participants returned to the clinics, 33 of whom were excluded because they had HIV (n=27) or grade 2-4 creatinine results (n=6). 798 (61%) of the 1315 eligible participants chose to start open-label PrEP and were followed up for a median of 335 days (IQR 0-364). 339 (42%) participants completed 12 months of follow-up; 220 (28%) did not return for any follow-up visits. Participants who were 30 years or older (odds ratio [OR] 1.8, 95% CI 1.4-2.2; p<0.0001), injected heroin (OR 1.5, 1.1-2.1; p=0.007), or had been in prison (OR 1.7, 1.3-2.1; p<0.0001) during the randomised trial were more likely to choose PrEP than were those without these characteristics. Participants who reported injecting heroin or being in prison during the 3 months before open-label enrolment were more likely to return for at least one open-label follow-up visit than those who did not report injecting heroin (OR 3.0, 95 % CI 1.3-7.3; p=0.01) or being in prison (OR 2.3, 1.4-3.7; p=0.0007). Participants who injected midazolam or were in prison during open-label follow-up were more likely to be greater than 90% adherent than were those who did not inject midazolam (OR 2.2, 95% CI 1.2-4.3; p=0.02) or were not in prison (OR 4.7, 3.1-7.2; p<0.0001). One participant tested positive for HIV, yielding an HIV incidence of 2.1 (95% CI 0.05-11.7) per 1000 person-years. No serious adverse events related to tenofovir use were reported.

Interpretation: More than 60% of returning, eligible BTS participants started PrEP, which indicates that a substantial proportion of PWID who are knowledgeable about PrEP might be interested in taking it. Participants who had injected heroin or been in prison were more likely to choose to take PrEP, suggesting that participants based their decision to take PrEP, at least in part, on their perceived risk of incident HIV infection.

Abstract access   [1]

Editor’s notes: Following the clinical trials assessing the efficacy of oral pre-exposure prophylaxis (PrEP) for HIV prevention, several of the trial teams and others have undertaken open-label extension and implementation studies. These were conducted to investigate the ‘real-world’ delivery of PrEP among key populations in various settings throughout the world. This paper presents the open-label study following the Bangkok Tenofovir Study (BTS) where oral PrEP was offered to participants, people who inject (or injected) drugs, for one year in the BTS study clinics. Unique to this study was the element of observed daily dosing at the clinics where participants were required to attend in order to access their PrEP. Results of the study are largely in line with reports from other similar studies, where people with more HIV-associated risk factors tended to adhere better and were more likely to take up and use PrEP. Interestingly, having a casual partner was not associated with better adherence, however, the number of casual partners reported by participants decreased during the study period, and there was no observed increase in other risky behaviours such as injecting drug use or sharing needles. One other additional point of note was the relatively higher adherence seen among prisoners and other incarcerated people which could point to consistent and easy access as a strong motivator to take PrEP. These results are an important contribution to the growing body of evidence around PrEP implementation which seems to suggest that people with a higher risk will be appropriately self-selecting for uptake of the programme. 

Asia [5]
Thailand [6]
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