An alarming number of people on antiretroviral therapy have developed a resistance to the drug tenofovir. Those findings are part of a report, published in the Lancet Infectious Diseases, that found a large number of HIV-positive people have become resistant to the medication, which is a common component in most HIV treatments.
The study involved multiple research centers and nearly 2,000 people from 36 countries, all of whom continued to have uncontrolled HIV despite being treated with medications including tenofovir. Research found that drug resistance was the likely cause of this treatment failure.
Worse, the scientists discovered that tenofovir resistance is quiet common: found in 60 percent of HIV patients in sub-Sahara Africa and 20 percent of patients in Europe. The study further suggested as many as an additional 15 percent of HIV patients in sub-Sahara Africa would develop resistance to the drug. Meaning up to 75 percent of sub-Saharan Africa's HIV population in treatment will eventually be resistant to tenofovir.
These results are particularly disconcerning, the study co-author Dr. Robert Schafer of Stanford University noted, because tenofovir is so widely used and it had been previously thought that patients would be less likely to develop resistance to tenofovir than other compounds in HIV medications.
"The availability of second-line drugs is increasing, but they're quite a bit more expensive and have more side effects associated with them," co-author Dr. Ravi Gupta of University College London told Reuters Health.
The study also revealed that resistance was more likely to develop in patients who had a lower CD4 count due to HIV disease progression, and that treatment worked best when begun with a high CD4 count.
"We think that part of the reason is that the immune system helps the drugs," Gupta explained. He went on to say that people in treatment for HIV could have developed the tenofovir resistance in one of two ways. Either they did not take the medication as perscribed and the drug mutated; or they were infected with HIV by someone who already had a drug resistant form of the virus. Resistant HIV apparently multiplies at the same rate as non-resistant HIV.
The study concluded that earlier detection of HIV and proper treatment are vital to keep resistance from developing. The researchers suggested that the World Health Organization should use monetary incentives to encourage people to get tested.
Even HIV prevention efforts could be negatively impacted by this wide-spread resistance to tenofovir, which could also affect the efficacy of PrEP.
"I think that if these trends continued...and you found a lot of HIV infections had resistance, then you would find the efficacy of PrEP is compromised," Gupta concluded.