Gilead Sciences’ updated version of tenofovir disoproxil fumarate (TDF, brand name Viread), called tenofovir alafenamide (TAF), combats hepatitis B virus (HBV) as effectively as the older drug and is safer for bone and kidney health. Gilead released top-line results of two ongoing Phase III, double-blind, 96-week clinical trials that included 1,298 treatment-naive and treatment-experienced participants with chronic hepatitis B.

One trial, called Study 108, includes 425 HBeAg-negative participants who were randomized in a 2-to-1 ratio to receive TAF (285 participants) or TDF (140 participants). In the other trial, called Study 110, 873 HBeAg-positive participants were also randomized 2 to 1 to receive TAF (581 participants) or TDF (292 participants).

In Study 108, 94.0% (268 of 285) of participants in the TAF group and 92.9% (130 of 140) of the participants in the TDF group achieved a HBV viral load below 29 after 48 weeks of treatment. In Study 110, 63.9% (371 of 581) of those in the TAF group and 66.8% (195 of 292) of those in the TDF group achieved a viral load below 29. Based on these results, TAF was declared non-inferior to (which essentially means as good as) TDF.

In both studies, those in the TAF groups experienced a significantly smaller average percentage decrease in hip and spine bone mineral density after 48 weeks of treatment than those in the TDF groups. Two indicators of kidney health showed that TAF had a better safety profile in that regard. In study 110, those who were taking TAF experienced smaller increases in serum creatinine than those taking TDF. In both studies, the median change in estimated glomerular filtration rate (eGFR) after 48 weeks of treatment showed that TAF was less toxic to the kidneys.

Gilead intends to apply for approval of TAF to treat hepatitis B in the United States and the European Union during the first quarter of 2016. The company intends to submit data from both studies for presentation at a major conference later in the year.

To read a Gilead press release on the study, click here.