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Results of a study published this month suggest that transmission of drug-resistant HIV remains prevalent in San Francisco, despite the introduction of new antiretroviral drugs such as Isentress and Selzentry.The researchers concluded that transmitted drug resistance is still a problem and emphasized the need for early diagnosis and aggressive treatment strategies for people with drug-resistant HIV.
HIV that is resistant to treatment with antiretrovirals is one of the most common reasons that treatments fail. When people with drug-resistant HIV pass their virus on to others, those newly infected people have fewer treatment options.
Drug-resistant HIV is usually transmitted by people who are undergoing antiretroviral therapy but fail to achieve viral suppression (an undetectable amount of HIV in the bloodstream), or by people who acquire drug-resistant HIV and transmit it before beginning antiretroviral therapy.
As more and more HIV-positive people take antiretroviral drugs for longer lengths of time, the prevalence of drug-resistant HIV has increasingly become a cause for concern. In many areas, 10 percent to 20 percent of new HIV infections involve transmission of drug-resistant HIV.
Beginning in late 2007, new HIV medications including Isentress (raltegravir), Selzentry (maraviroc), and Intelence (etravirine) were introduced.
Researchers predicted that these newer antiretrovirals would better suppress transmission of drug-resistant forms of HIV if the main driver was transmission by people on antiretroviral therapy, since the new drugs would be better at suppressing HIV that is resistant to older medications.
Conversely, researchers hypothesized that if the main driver of transmitted drug resistance was treatment-naïve people with drug-resistant HIV, the impact of improved antiretroviral therapy would be minimal or delayed until the new drugs become widely available.
In this study, the researchers tried to determine whether the new antiretrovirals had an effect on transmission rates for drug-resistant HIV in the years since they were approved. To do so, they used results from a study that was designed to measure rates of transmitted drug resistance between 2002 and 2009.
The study included 372 people in San Francisco who had tested positive for HIV within 12 months of enrollment. Most of the participants (96 percent) were men who have sex with men; 9 percent of participants were injection drug users.
Participants were divided into two groups: those who tested positive for HIV between 2005 and 2007 and those who tested positive between 2008 and 2009. This allowed researchers to compare the prevalence of transmitted drug resistance before and after the introduction of new antiretrovirals in late 2007.
The researchers analyzed participants’ CD4 cell counts, viral load, and the presence of any drug resistance mutations displayed by their HIV.
Results showed that the prevalence of transmitted drug resistance more than tripled between 2003 and 2007 from 7 percent in 2003 to 24 percent in 2007. Between 2008 and 2009, the rate dropped to 15 percent of participants.
However, the researchers concluded that the difference was not statistically significant, and that overall, the chances of acquiring drug-resistant HIV in 2008 to 2009 were not significantly lower than the chances of acquiring drug-resistant HIV in 2005 to 2007.
The researchers listed two possible explanations for the study results: (1) poor antiretroviral therapy adherence and/or poor medical care in people who are on antiretroviral therapy or (2) considerable transmission of drug resistance via treatment-naïve individuals. Since other studies have indicated that more HIV-positive people in San Francisco have successfully achieved viral suppression in recent years, the researchers thought the second explanation was more likely.
The study authors stressed that there is a scarcity of data on the use of new antiretroviral medications in San Francisco and warned that delayed uptake of the new drugs will have a delayed impact on transmission of drug-resistant HIV.
As a result, they suggested that longer studies with participants from broader geographic areas are needed to allow for better comparisons of transmitted drug resistance rates before and after the introduction of novel anti-HIV drugs.
The Friends of AIDS Foundation is dedicated to enhancing the quality of life for HIV positive individuals and empowering people to make healthy choices to prevent the spread of the HIV virus. To learn more about The Friends of AIDS Foundation, please visit: http://www.friendsofaids.org.
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