US pharmaceutical giant Merck announced it is halting a clinical trial on a drug once touted as a promising treatment for Alzheimer's disease, saying studies show it does not work.
The decision was made to end trials on verubecestat for mild to moderate Alzheimer's disease after an external study found there was "virtually no chance of finding a positive clinical effect," said a statement issued late Tuesday.
"While we are disappointed that a benefit was not observed in this study, our work continues," said Roger Perlmutter, president of Merck Research Laboratories, adding that verubecestat will continue to be studied "in people with less advanced disease."
Another study using the experimental drug is continuing, with its results expected in 2019.
The results of a preliminary trial involving the drug in 32 people were released in November, when the company described the results as encouraging.
The experimental drug was said to work by reducing levels of beta amyloid proteins by blocking an enzyme known as BACE1.
In people with Alzheimer's disease, the proteins clump into plaques that damage the brain, affecting cognitive abilities, especially memory. The enzyme plays a key role in producing the proteins.
Three months ago, US firm Eli Lilly abandoned its experimental drug solanezumab, saying it failed in a major clinical trial and calling the results "disappointing."
The World Health Organization says 36 million people worldwide suffer from dementia.
The number of cases is expected to reach more than 65 million by 2030, and triple to 115 million by 2050.