ContraVir’s experimental hepatitis B virus (HBV) treatment CMX157 bested Gilead Sciences’ new version of tenofovir (tenofovir alafenamide, known as TAF) in laboratory tests. An in vitro study compared CMX157, an analog of the antiretroviral tenofovir, with other tenofovir prodrugs, including Viread (tenofovir disoproxil fumarate, or TDF) and TAF, looking at how they affected hep B.

Viread is already approved to treat hep B. Gilead is investigating TAF, which is safer for the bones and kidneys than TDF, as a treatment for the virus.

This study found that CMX157 and TAF were similarly potent against hep B and that the former drug trended toward greater potency. The duration of CMX157’s activity against the virus was superior. Nine days after incubating the respective drugs with hep B in two different experimental conditions, the viral rebound of the CMX157-treated virus was one half to one third that of the TAF-treated virus.

ContraVir plans to start enrolling hep B–negative participants in a Phase I/IIa trial of CMX157 during the second quarter of 2016.

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