A new formulation of the widely used HIV antiretroviral tenofovir is potent at a lower dose and works as well as the current version of the drug—but it has fewer effects on indicators of kidney and bone health, aidsmap reports. Paul Edward Sax, MD, clinical director at Brigham and Women’s Hospital and a professor of medicine at Harvard Medical School, presented findings from a Phase II study comparing Gilead Sciences’ new tenofovir alafenamide (TAF) with tenofovir disoproxil fumarate (TDF), which is the sole ingredient in Viread and a component of the single-pill combination therapies Truvada, Atripla, Complera and Stribild.

Researchers have found that concentrations of TAF in HIV-infected cells are five times higher than those of TDF. The new formulation’s levels in blood are far lower by comparison, which would likely make TAF less toxic to the kidneys and bones.

In a double-blind, placebo-controlled study, the researchers divided 170 treatment naive people with HIV into groups with a ratio of two to one receiving either 10 milligrams of TAF or 300 mg of TDF once a day in a coformulated pill with elvitegravir, cobicistat and emtricitabine (which in the TDF arm meant the participants were taking Stribild) for 48 weeks.

At the study’s outset, the median viral load was about 40,000 and the median CD4 cell level was approximately 390. The participants had normal kidney function.

At the end of the 48 weeks, 88.4 percent of those taking the TAF coformulation had achieved an undetectable viral load, compared with 87.9 percent in the TDF group. Average CD4 gains between the two groups were a respective 177 and 204. None of these differences between the arms were statistically significant, meaning they could have happened by chance.

Indicators of kidney function, such as changes in a marker known as eGFR, evidence of protein in the urine and a shift in serum creatinine, suggested TAF is a safer drug. Similarly, indications of bone health, including DEXA scans taken at the spine and hip at 24 and 48 weeks to measure bone mineral density, showed less deterioration in the TAF group than in the TDF arm. A third of those taking TAF had no change in their hip bone density compared with 7 percent of the TDF group.

To read the aidsmap story, click here.

To read the conference abstract, click here.