About 12 percent of HIV-positive people with chronic hepatitis B virus (HBV) infection failed to control their HBV after one year with Viread (tenofovir), combined with either Epivir (lamivudine) or Emtriva (emtricitabine). These data were presented at the American Association for the Study of Liver Diseases, which was being held October 29 to November 2 in Boston.

Viread, with or without Epivir or Emtriva, is considered a first-line treatment for chronic HBV infection. Because those drugs also control HIV, guidelines recommend that coinfected people start treatment right away—if therapy for chronic HBV is needed—and include those drugs in their regimens. Long-term data indicate these drugs are effectivedo at controlling HBV in coinfected individuals, but questions remain about how and when they are most useful.

To better explore the efficacy of Viread, researchers at King’s College Hospital in London, examined the medical records of 113 coinfected people receiving care at their clinic. The researchers found that 14 (12.4 percent) of the study participants had detectable HBV levels in their blood despite being on a Viread-containing regimen for at least 48 weeks and despite having undetectable HIV levels.

Before starting a full HIV regimen containing Viread, nine of the 14 people had taken Epivir by itself and three three had taken Viread by itself to treat their HBV. At the time they started taking a full HIV regimen, 36 percent had HBV that was resistant to both Epivir. None had detectable HBV resistance to Viread. Of the 14 who had detectable HBV levels one year after starting a Viread-containing HIV regimen, nine saw their HBV levels become undetectable after two years of treatment.

“Despite optimal adherence to [Viread] treatment, as evidenced by control of HIV, 14 [patients] failed to achieve an undetectable HBV DNA after 48 weeks of treatment,” the authors state. “In [five of] 14 patients, HBV DNA remained detectable at a low level nearly 4 years into [Viread] treatment, but no patient developed [Viread] HBV resistance.”

Though the authors hypothesize that the failure to control HBV might be due to HIV, or cumulative HBV resistance at very low levels, and that further research is warranted, they conclude: “The long-term clinical significance of low low-level HBV viremia in this population is unclear.”