I believe the short 48 week duration of the ABT study does not capture what I believe is the the durability of Truvada when compared with Isentress, which has a low resistance hurdle when compared with Truvada.
I believe part of this is due to the relative half-life of the drugs, Viread with median 17 hours serum and 60 hour intracellular, compared with 9 hours serum for Isentress and an ill-defined intracellular range of up to 29 hours.
There are known advantages of reduced viral fitness resulting from adapted viral resistance to the shorter-live Emtriva co-drug in Truvada, or the closely related Epivir.
The other portion of reduced Isentress durability lies in the limited number of mutations required to obtain resistance.
Side-effect wise you have kidney toxicity with Viread compared with inflammatory symptoms in many who try Isentress.
It would be great if someone developed a superior complementary therapy to Viread, but I don't see that currently among the contenders.
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