For the second time this summer, a candidate drug has failed to slow the rate of mental decline in large trials of patients with Alzheimer’s disease. But some hope remains that the compound could help patients with milder forms of the disease.

On Friday, Eli Lilly announced that two late-stage trials of its amyloid-grabbing antibody solanezumab did not protect patients’ cognitive abilities. The results come just weeks after Pfizer and Johnson & Johnson announced their anti-amyloid antibody bapineuzumab failed in clinical trials (see “A New Setback for Alzheimer’s Drugs”).

However, when the data from both of Eli Lilly’s trials was pooled together, the company says its compound was able to slow decline in patients with mild forms of the disease. If that suggestion proves true, then it would lend support to the idea that amyloid-fighting drugs need to be administered early. Recent studies show that changes in the brain begin long before dementia sets in (see “An Alzheimer’s Warning 25 Years Before Symptoms Show”), so early treatment may be key to preventing permanent damage.

There is no cure for Alzheimer’s disease, which progressively robs patients of their memory and thinking abilities. The cause of the disease is unknown. But because the brains of Alzheimer’s patients are riddled with amyloid plaques– clumps of a piece of the amyloid protein– many see amyloid as a culprit and therapeutic target. Eli Lilly, Pfizer and Johnson & Johnson had all placed multi-million dollar bets on the amyloid hypothesis with the hope that their compounds would clear or block the formation of amyloid plaques in the brain.

According to a statement from Jan Lundberg, president of Lilly Research Laboratories, Eli Lilly thinks the results of the combined trial data validate that gamble:

“We believe the pooled data support the amyloid hypothesis, as these are the first Phase 3 data with an anti-beta amyloid agent that appear to show a slowing of cognitive decline.”

The Alzheimer’s Disease Cooperative Study will present the results of its independent analyses of the solanezumab data in Boston in early October.