Daily oral PrEP (pre-exposure prophylaxis) with a tablet containing tenofovir disoproxil fumarate (tenofovir, marketed
in the United States under the brand name Viread
was found to reduce the risk of acquiring HIV by approximately
49 percent in a study of 2,413 men and women who inject drugs in Bangkok, Thailand.
Those who took the medication consistently had higher levels of protection, similar to findings previously reported
from other PrEP trials. In a separate analysis of participants known to be adherent, because they were observed taking
their medication and had tenofovir detected in their blood, the risk of HIV acquisition was reduced by approximately
74 percent.
This is the first study to report results of PrEP efficacy among people who inject drugs. Previous studies have found
that PrEP with tenofovir – alone or in combination with emtricitabine (brand name Truvada
– can reduce the risk of sexual transmission of HIV among heterosexuals and men who have sex with men.
Trial Design and Study Population
Overview:
The Bangkok Tenofovir Study (BTS) examined use of a once-daily antiretroviral pill containing tenofovir
disoproxil fumarate as PrEP for preventing HIV infection among adult men and women who inject drugs in Bangkok,
Thailand. The CDC- sponsored study was conducted in collaboration with the Bangkok Metropolitan Administration
(BMA) and the Thailand Ministry of Public Health. Study medication was donated by the manufacturer, Gilead Sciences.
The primary goal of the study was to determine if PrEP with daily oral tenofovir wnhttp://www.cdc.gov/hiv/pdf/prevention_research_prep_BTSfactsheet.pdfould reduce the risk of HIV infection
among people who inject drugs. Safety, adherence, and participants’ risk behavior were also assessed.
Study Population:
2,413 HIV-uninfected men and women who reported injecting drugs during the previous year were
recruited to participate in the study at 17 BMA drug treatment clinics in Bangkok. Approximately 80 percent of the
population were male (1,924) and 20 percent were female (489). The age of participants ranged from 20 – 60, with a
median age of 31 years. People with HIV, people with hepatitis B infection, and women who were pregnant or breast
feeding were excluded from the study.
Participants were randomly assigned to one of two arms: 1,204 participants were assigned to receive one 300 mg
tablet of tenofovir daily, and 1,209 were assigned to take one placebo tablet daily. Tenofovir and placebo tablets were
similar in shape, color, and taste. Neither researchers nor participants knew a participant’s group assignment.
Two participants in the placebo arm tested positive for HIV at baseline and were excluded from the analysis, which
included the remaining 2,411 HIV-negative participants.