APP and Alzheimer disease: The study showed that combination treatments resulted in significant reductions of total Aβ by 45–65% in the brain of AD mouse overexpressing both human amyloid precursor protein containing the Swedish and London mutations and human QC (hAPPsl × hQC), while single treatments at subtherapeutic levels only showed a moderate (16–41%) but statistically insignificant reduction in Aβ level.