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PrEP effective in injection drug users
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Prophylactic treatment with tenofovir disoproxil fumarate reduced the incidence of HIV infection among injection drug users, according to data published in The Lancet.
“This study completes the picture of pre-exposure prophylaxis (PrEP) efficacy for all major HIV risk groups,” Michael Martin, MD, chief of HIV clinical research for the Thailand Ministry of Public Health – US CDC Collaboration, said in a press release. “We now know that PrEP can be a potentially vital option for HIV prevention in people at very high risk for infection, whether through sexual transmission or injection drug use.”
Martin and colleagues, including Kachit Choopanya, MD, of the Bangkok Tenofovir Study Group, conducted a randomized, double blind, placebo-controlled trial in which 2,413 volunteers from 17 drug treatment clinics in Bangkok were enrolled. From June 9, 2005, to July 22, 2010, the volunteers were assigned tenofovir (Viread, Gilead Sciences) or placebo. The participants were followed for 9,665 person-years, and there was no difference between the groups in adherence to the study drug.
Fifty of the participants became infected during the follow-up period. In the tenofovir group, 17 acquired HIV, for an incidence of 0.35 per 100 person-years. In the placebo group, 33 acquired HIV, for an incidence of 0.68 per 100 person-years. This resulted in a 48.9% reduction in HIV incidence among those who took tenofovir (95% CI, 9.6-72.2). The adverse event rates were similar between the groups.
“Adherence was a key factor determining efficacy in our trial among people who inject drugs, as it has been in previous PrEP trials examining sexual transmission,” Martin said. “These results underscore the importance of helping people using PrEP achieve effective levels of adherence.”
In a corresponding comment, Salim S. Abdool Karim, MD, PhD, director of the Center for the AIDS Program of Research in South Africa (CAPRISA) at the University of KwaZulu-Natal, South Africa, said the reduction of HIV infections may not be solely attributed to a protective effect of ART on injection drug users. Some of these individuals also practice risky sexual behaviors, making it possible that the protective effect was partly attributable to the protective effects PrEP has on sexual transmission of HIV.
Salim S. Abdool Karim
“Even though questions remain about the extent to which PrEP can be effective in preventing either of the routes of transmission in this group, the overall result is that daily tenofovir does reduce HIV transmission in injecting drug users,” Karim wrote. “The introduction of PrEP for HIV prevention in injecting drug users should be considered as an additional component to accompany other proven prevention strategies, like needle exchange programs, methadone programs, promotion of safer sex and injecting practices, condoms, and HIV counseling and testing.”
For more information:
Choopanya K. Lancet. 2013;doi:10.1016/S0140-6736(13)61127-7.
Karim S. Lancet. 2013;doi:10.1016/S0140-6736(13)61140-X.
Disclosure: Martin reports no relevant financial disclosures. Karim is a principal investigator on the CAPRISA 004 tenofovir gel trial and an inventor on two pending patents of tenofovir gel with Gilead.
Perspective
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Carlos del Rio, MD
This study is important because it is the first PrEP study among injection drug users (IDUs). While we have had successful PrEP studies among MSM (IPrEx study) and heterosexuals (Partners PrEP and TDF-2 studies) we have yet to have any studies among IDUs. The efficacy of tenofovir, which reduced incidence of HIV by almost 50% in IDUs, is also compatible with other trial results. For this trial the study drug was administered as directly-observed therapy, and like in other PrEP studies, better adherence led to better outcomes. Among participants with good adherence and detectable tenofovir levels in blood, the efficacy was 73.5%.
However, it is important to state that tenofovir should not be seen as the only strategy for IDUs. Harm reduction, particularly needle exchange, has proven to be effective in reducing HIV incidence. However, many countries, including Thailand where this study was conducted, consider needle exchange illegal and do not support it. The United States is the same. We need to change these attitudes if we are to truly implement combination prevention for IDUs.
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