The other thing that cadno isn't assessing is the makeup of those enrolled in the trials. Were they mild or mild-mod alzheimers patients? What was the age range of those in the trial? I think the 273 trial enrolled older (or was it younger?) subjects and more further advanced with disease. Both factors make it harder to get improvement
I only looked at donepezil MMSE charts for mild to moderate Alzheimer's. The charts for severe Alzheimer's are obvious, because they decline very quickly regardless of the treatment. If I had looked at severe Alzheimer's charts, it would hurt donepezil compared to 2-73.
I'd have to look at the ages. They are multiple studies. Still, I wouldn't extrapolate from differences in age. I don't know enough/haven't studied enough to reliably be able to say how age would impact the drug's effect on MMSE.