Gilead Sciences’ Vemlidy (tenofovir alafenamide, or TAF) is less toxic to bones and kidneys than the company’s Viread (tenofovir disoproxil fumarate, or TDF) when used as treatment for hepatitis B virus (HBV). Ninety-six-week data of two large trials also recently showed that switching from Viread to Vemlidy leads to improvement in a key liver enzyme level.

Researchers evaluated 96-week data from two randomized double-blind Phase III studies, called Studies 108 and 110, that compared Vemlidy to Viread among those who had or had not been treated for HBV before and who had HBeAg-negative or HbeAg-positive hep B.

Findings were presented at the 52nd International Liver Congress in Amsterdam.

At week 96, those receiving Vemlidy and Viread experienced virologic response rates of 90 percent (257 of 285) and 91 percent (127 of 140) respectively among HBeAg-negative individuals and 73 percent (423 of 581) and 75 percent (218 of 292) among HBeAg-positive individuals.

In both studies, a greater proportion of those receiving Vemlidy saw their ALT liver enzyme level normalize compared with those receiving Viread. Additionally, at the 96-week mark, those receiving Vemlidy experienced smaller declines in the hip and spine bone mineral density as well as smaller declines in their estimated creatinine clearance (an indication of kidney health), compared with those receiving Viread.

Groups taking each of the two drugs experienced similar rates of adverse health events and similar low rates of adverse health events leading them to stop treatment.   

None of the participants showed signs of virus that was resistant to Vemlidy of Viread at the 96-week mark.

Researchers also conducted an analysis of 541 people from both studies who finished 96 weeks during which they received either Vemlidy or Viread on a double-blind basis and then were switched to open-label Vemlidy (meaning they knew which drug they were taking at that point). A total of 180 people were switched from Viread to Vemlidy at week 96. These individuals maintained suppression of hep B while experiencing increasing rates of normalization of ALT enzymes during a 24-week period. These individuals also saw improvements in their hip and spine bone mineral density as well as their estimated creatinine clearance.

To read a press release about the study, click here.