Umibecestat is a small molecule inhibitor of the beta-site amyloid precursor protein-cleaving enzyme 1 (BACE1). 

The Generation Program was testing the safety and efficacy of umibecestat for the prevention or delay of the onset ofAlzheimer's diseasein people at high risk for developing symptoms based on age and genetic makeup. 

However, data from apreplanned analysisshowed worsening in some measures of cognitive function, leading to the conclusion that the potential benefit for participants in the studies did not outweigh the risk, the developers said. 

"We still believe amyloid plays an important but complex role in Alzheimer's disease," David Reese, MD, executive vice president of Research and Development at Amgen, said in a statement. 

"Although the outcomes of the research program did not lead to the results we aimed for, we are committed to sharing our findings to help advance the medical and scientific community one step further toward finding a prevention for this devastating disease," said Reese. 

Umibecestat joins a host of other amyloid-focused drugs that have failed to demonstrate a benefit in Alzheimer's disease. They include verubecestat (Merck), another BACE1 inhibitor that did not reduce the decline in cognitive function or overall function compared with placebo in a phase 3 trial,as reportedbyMedscape Medical News. 

The list of failed Alzheimer's drugs also includesaducanumab(Biogen, Eisai) andcrenezumab(Roche, AC Immune) — both scrapped in phase 3 testing. 

Disappointed But Hopeful 

In a statement, the Alzheimer's Association called the latest failure disappointing "on behalf of the millions of people living with Alzheimer's disease and their families."

Currently, more than 5 million Americans are living with Alzheimer's disease or dementia. By 2050, this number could nearly triple to 14 million. 

"The Alzheimer's field has never faced more challenges, but due to increased research funding it has never been more hopeful," the Alzheimer's Association said. 

"We must advance all potential treatment targets and also explore methods for combining these approaches. We must diversify our treatment and prevention strategies, which has been a focus in the last few years and will lead to new generations of approaches to be pursued. No stone can be left unturned," they added. 

The Alzheimer's Association International Conference (AAIC) gets underway this weekend in Los Angeles, California.Medscapewill be onsite throughout the 5-day conference to report the latest research.