To investigate whether inhibiting BACE1 in adults might be less harmful, researchers generated mice that gradually lose this enzyme as they grow older.
As Yan and colleagues explain in their paper, the enzyme in question helps to produce beta-amyloid peptide.
On Tuesday, executives were forced to admit defeat, dealing an ominous forewarning to the four other major pharmaceutical companies which have bet big on this inhibitor, BACE1, to treat the disease.
Researchers were able to reverse the formation of amyloid plaques, which gradually kill neurons in patients with Alzheimer's disease, in the brains of mice - essentially reversing the condition.
They claim their tests on a 20-month-old mouse - equivalent to a 50-year-old human - show it could be possible to halt the disease if it is caught decades earlier than usual.More news: Facebook rolls out Messenger Kids
The researchers were led by Riqiang Yan, of the Department of Neuroscience at the University of Connecticut School of Medicine in Farmington.
Yan said that, as far as they are aware, "this is the first observation of amyloid deposits in any study of Alzheimer's disease in mice".
Drugs that inhibit BACE1 are therefore being developed as potential Alzheimer's disease treatments but, because BACE1 controls many important processes by cleaving proteins other than APP, these drugs could have serious side effects.
The O'Donnell Brain Institute is also leading a five-year national clinical trial aiming to establish how fitness levels and Alzheimer's disease are connected.
These mice developed normally and appeared to remain perfectly healthy over time.More news: The Hays plc (LON:HAS) Receives Buy Rating from Liberum Capital
'If we can show the compound is safe, it would be available for preventative measures.
Another major pharma player, Roche, canceled its BACE1 research back in 2013, but several large-scale trials for BACE1 inhibitors are still now in development or underway.
APECS is a randomized, placebo-controlled, parallel-group, double-blind Phase 3 clinical trial evaluating the efficacy and safety of verubecestat in people with prodromal AD. Subjects are randomized to receive placebo, or 12 mg or 40 mg verubecestat, once-daily.
Roche did away with BACE1 inhibitors in 2013.
Scientists also used brain imaging to measure the functionality of each patient's white matter. The Merck Phase 3 trial failure does strike a giant blow to this once-promising field, despite this new research reiterating the pathway as effective, at least in animal models.More news: CI Global Investments Inc. Has $218.90 Million Stake in Microsoft Co. (MSFT)
But the once-exciting trial has slowly spluttered to a halt: the firm shelved a similar trial of the same drug Verubecestat in late-stage patients previous year, but had hoped it could work in early or mid-stage sufferers.