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January 28th, 2016 - Stanford Medicine Scope - by Ruthann Richter
HIV resistance to the antiviral tenofovir, one of the mainstays of HIV treatment and prevention, is increasingly common following therapy, particularly in low and middle-income countries, according to a new, multi-national study.
“Public health organizations and global funders have been very effective at expanding antiretroviral drug therapy to increasing proportions of patients in need,” said Robert Shafer, MD, professor of medicine and co-author of the work. “This study highlights the need for efforts to ensure that the regimens used to treat HIV retain their effectiveness for as long as possible.”
Researchers studied 1,926 patients in 36 countries who developed virological failure after taking a first-line regimen containing tenofovir. In this group, tenofovir-resistant strains were found in 60 percent of the patients in sub-Saharan Africa, compared with fewer than 30 percent in Europe and North America. Patients most at risk for tenofovir resistance were those who started therapy late in the progression of the disease or who received tenofovir in combination with drugs less commonly used in upper-income countries.
About two-thirds of the patients with tenofovir-resistant strains also had become resistant to the other two drugs in their regimens, suggesting their treatment had become largely ineffective.
Resistance may develop when patients don’t take their medication regularly, although it may also occur in adherent patients on some of the regimens used in the developing world. People carrying resistant strains can pass them along to others, so that HIV resistance could become even more widespread, the researchers note.
“Tenofovir is a critical part of our armamentarium against HIV, so it is extremely concerning to see such a high level of resistance to this drug,” said lead author Ravi Gupta, MD, at University College London. “It is a very potent drug with few side effects, and there aren’t any good alternatives that can be deployed using a public health approach. Tenofovir is used not only to treat HIV but also to prevent it in high-risk groups, so we urgently need to do more to combat the problem of emerging resistance.”
The researchers say the results reinforce the need for increased drug resistance surveillance in both untreated and treated HIV-positive individuals. They are now working to better understand how these resistant viruses develop and spread.
The study, which involved dozens of researchers and institutions, appears today in the journal Lancet Infectious Diseases. It was co-authored by scientists at the London School of Hygiene and Tropical Medicine and funded by the Wellcome Trust.
