New Tenofovir Regimens Containing TAF (Tenofovir Alafenamide) What’s Different, What’s The Same

Tenofovir alafenamide (TAF) the new formulation and prodrug of the old tenofovir disoproxil fumarate known as was approved late last year in the single tablet regimen known as Genvoya.

Genvoya contains emtricitabine/tenofovir alafenamide (ECF/TAF), elvitegravir and cobicistat is similar to Stribild which contains emtricitabine/tenofovir disoproxil fumarate (ECF/TDF), elvitegravir and cobicistat the only difference being that it contains TAF instead of TDF.

So what’s the Difference?

1. ECF/TDF has shown to decrease bone mineral density in patients. ECF/TAF has less of an effect on bone mineral density. In studies on initial therapy and switch therapy bone mineral density reductions are less in patients on ECF/TAF and there was also an improvement in bone mineral density in patients switched from ECF/TDF to ECF/TAF

2. Kidney toxicity also seems to be less in patients on ECF/TAF compared to ECF/TDF. Patients who are stable and on ECF/TDF who were switched to ECF/TAF have shown improvements in kidney function

3. ECF/TAF has been studied in patients who have been virologically suppressed and complex treatment histories. A study showed that a combination of ECF/TAF with darunavir 800mg is potentially safe for simplifying therapy even in patients who have multiclass resistance. Patients who showed resistance to darunavir or who had high resistance to nucleosides were excluded from the study

So What’s The Same?

1. The antiviral effect of ECF/TAF does not seem to be greater than ECF/TDF. Both the Genvoya & Stribild formulations contain cobicistat which have the potential for drug-drug interactions
2. The price is not different, in fact the average wholesale price (AWP) is actually one hundred dollars cheaper for Genvoya compared to Stribild

References:

Sax P, Brar I, Elion R, et al. 48 week study of tenofovir alafenamide (TAF) versus tenofovir disoproxil fumarate (TDF), each in a single tablet regimen (STR) with elvitegravir, cobicistat, and emtricitabine [E/C/F/TAF Versus E/C/F/TDF] for initial HIV treatment.

Mills A, Andrade-Villanueva J, DiPerri G, et al. Switching from a tenofovir disoproxil fumarate (TDF)-based regimen to a tenofovir alafenamide (TAF)-based regimen:

Huhn G, Tebas P, Gallant J, et al. Strategic simplification: the efficacy and safety of switching to elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide (E/C/F/TAF) plus darunavir (DRV) in treatment- experienced HIV-1 infected adults