I seem to recall that being a much longer trial aimed at addressing the disease earlier on. Don't recall exactly by memory (and too lazy too check :-)) but think length is in YEARS.
I think ß-secretase inhibitors therapies will face similar challenges to those seen with y-secretase (because the enzyme has many substrates* and a wide substrate binding domain) I'd expect serious off-target tox.
*like neuregulin-1, which is involved in myelination and y-secretase inhibitors have in fact shown AE on myelin in animal models.