I’m pretty sure the design of ENDURANCE-3 is a business decision by ABBV/ENTA rather than a requirement imposed by regulators.
To which I might add, marketing....
Abbvie has been battling the notion that Gild is justbest, even perhaps where it wasn't (G-1b's)
Gilead may have massaged the numbers a little; they provided blended SVR rates; combining G-1a and g-1b rates.
One REALLY had to look hard to find SVR rates for g-1b's.
It may be that Abbvie is out to upset the mindset first by toppling the Sovaldi/Daclatasvir best treatment for G-3, and then perhaps..... challenging SOV/VEL.
When the results are so close in SVR rates, it is conceivable that the Abbvie program could be better in some ways; Cure rates, tolerability, or cure rates on certain patient sub-sets.
It may even be that undermining the the concept may work on getting more acceptance of the upcoming 2nd gen program, but even a bit more consideration for the 1st gen.
It would seem to me, that if this were a purely optional exercise, Abbvie would avoid direct comparison it it knew it was inferior. I think it seems almost implicit that the SVR rates will be compared with SOV/VEL.
I am also wondering if they are gathering data on adding a 3rd component to the ABBVIE 2nd gen; nuke or cyclophillin?