There’s a worrying trend in the treatment of HIV, particularly in sub-Saharan Africa: A new study has found that there’s growing resistance to tenofovir, one of the most effective and inexpensive first-line anti-retroviral drugs.
A large international team of researchers studied more than 1,900 patients around the world and found tenofovir-resistant HIV strains in 60 percent of the patients in almost every country in sub-Saharan Africa.
This is in contrast to 20 percent of those infected with the AIDS virus in Europe who develop resistance.
The study suggested that up to 15 percent of patients treated with tenofovir–based drug combinations would develop resistance in the first year.
In addition, two-thirds of those resistant to tenofovir have been found to not respond to two other drugs in the pharmaceutical cocktail used to keep HIV in check.
The findings are published in the journal The Lancet Infectious Diseases.
All of the patients in the study, led by Ravi Gupta, an infectious-disease specialist and consultant at University College London, were becoming sicker despite first-line treatment with tenofovir.
The World Health Organization "recommends this drug above all others," Gupta said. "It’s one of the backbone drugs in the combination. So what we wanted to know is what would the impact be if [patients were] using this drug in large populations in mostly poor settings.”
Gupta said the problem is that many people do not take the combination therapy as often or as regularly as they should, leading to HIV resistance. He said patients need to take their medication at least 85 to 90 percent of the time for it to be fully effective. Otherwise, the virus begins developing mutations as it replicates unchecked.
Drug supplies interrupted
In remote areas, Gupta said, supplies of tenofovir are often interrupted, leading to breaks in treatment. “And in the presence of suboptimal levels of drugs, it starts adapting to the presence of drugs while mutating itself, to the point where ... presence of the drug doesn’t really inhibit the virus anymore,” he said.
In the laboratory, studies show the mutated virus does not spread easily in real world conditions.
That’s not what’s actually happening in places where there’s emerging resistance. Gupta said that's because virus levels are high enough in people with the resistant strain that it becomes fully infectious.
Often, he said, patients don’t get tested or receive treatment until late in the disease process. Health care officials should "optimize and strengthen the treatment programs worldwide, such that patients are monitored more frequently and with a viral load test," he said. "What the viral load tells you is how much virus is in the blood.”
There are more expensive, second-line treatments that can be used in patients for whom tenofovir no longer works, but most are not as effective and they are not readily available in resource-poor countries.
Gupta said global health organizations need to focus on keeping treatments that include tenofovir effective for as long as possible.