Rates of antiretroviral (ARV) resistance are very high among those failing first-line Viread (tenofovir disoproxil fumarate, or TDF)–based treatment in a Kenyan clinic, aidsmap reports. Publishing their findings in the Journal of the International AIDS Society, researchers studied a sample of 333 out of nearly 27,000 people treated for HIV at Kenya’s largest HIV clinic.

The participants had all been on TDF–based treatment for more than six months. A total of 217 members of the group were taking their first TDF­–based regimen. All of these individuals were also taking Epivir (lamivudine). Sixty percent additionally took Sustiva (efavirenz); the remaining 40 percent additionally took Viramune (nevirapine).

The remaining 116 people had taken other HIV regimens before going on TDF. Almost all had taken Zerit (stavudine, or d4T), four out of five had taken Viramune, one in three had taken Sustiva and one in four had taken Retrovir (zidovudine, or AZT).

The participants had been taking TDF for an average of two years. Those who had previously taken other regimens had been on HIV treatment for an average of six years.

Fifty-nine (18 percent) of the 333 participants had a detectable viral load (above 40) and 10 percent had a viral load above 1,000. Twenty-seven percent and 15 percent of those new to treatment had a detectable viral load and a viral load above 1,000, respectively, compared with a respective 7 percent and 1 percent of those who had switched to TDF–based treatment from a previous regimen.

Out of 35 people on first-line treatment for whom there were drug resistance test results available, 31 (89 percent) had drug resistance and 83 percent had resistance to both nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs, or nukes) and non-nucleoside reverse transcriptase inhibitors (NNRTIs, or non-nukes). Twenty-seven (77 percent) had the M184V resistance mutation to Epivir and Emtriva (emtricitabine), and 69 percent had the K65R mutation that leads to resistance to tenofovir along with the rest of the NRTI class, except for Retrovir.

Eighty-three percent of these 35 individuals showed clinically significant resistance to Epivir and Emtriva, 71 percent to tenofovir, 86 percent to Sustiva and 89 percent to Viramune. Seventy-seven percent had resistance to Intelence (etravirine) and Edurant (rilpivirine), ARVs they had never taken. Seventy-seven percent were resistant to Ziagen (abacavir), which is often prescribed as an alternative to tenofovir. Among the nuke and non-nuke classes, the only ARV that would largely still work for this group was Retrovir; just 6 percent were resistant to the drug.

A recent report found high levels of tenofovir resistance among those failing ARVs around the world. Another recent study found that overall rates of ARV resistance have fallen dramatically among those treated for HIV in Switzerland.

To read the aidsmap article, click here.

To read the study abstract, click here.