Compared with tenofovir disoproxil, tenofovir alafenamide is a slightly different prodrug of tenofovir, according to Dr. Kwo.
The approved dose of tenofovir alafenamide is 25 mg, compared with 300 mg for tenofovir disoproxil. “It’s more stable in the serum, so you don’t need higher levels, and you have fewer off-target effects,” Dr. Kwo said.
The two agents are “Coke and Pepsi” in terms of efficacy, he added, noting that comparative studies showed similar efficacy on endpoints of percentage HBV DNA less than 29 IU/mL and log10 HBV DNA change.
Very low rates of resistance are seen with first-line therapies for chronic hepatitis B, including entecavir and tenofovir disoproxil. “We wouldn’t expect (tenofovir alafenamide) to be any different, but nonetheless the surveillance has to happen,” Dr. Kwo said.