they chose to use 1.8mg of victoza as the comparator for the trial vs bydureon. victoza has 3 doses and the most commonly used dose is 1.2mg. i'm not 100% sure about this but I think the 1.2mg dose is the comparable dose when you account for things like cost of therapy
There is also a huge difference in cost between 1.8 which is much more expensive compared to 1.2 for Victoza. I also posted yesterday that 1.8 dosing for Victoza was rejected by the Brits in England, because of its low cost benefit. Had Lilly chosen to compare Bydureon to Victoza multiple doses of .6mg, 1.2mg and 1.8mg, it would have demonstrated superiority.