Efforts to find a drug that may slow the progression of Alzheimer's disease saw a glimmer of hope this week in a small trial using an experimental treatment.
Researchers are testing the drug, known as LMTM and made by TauRx Therapeutics, Ltd. of Singapore, to see if it can reduce the accumulation of the protein tau in the brain.
When tau malfunctions, the brain can form protein tangles that are believed to cause Alzheimer's, the most common form of dementia.
Overall, the clinical trial involving 891 people with suspected Alzheimer's disease showed no benefit from the drug, which participants were randomized to receive at one of two doses, or a placebo.
Most of those in the study were taking other approved medications for Alzheimer's disease in addition to the experimental drug, said the researchers.
But a smaller subgroup of over 100 patients who were taking only the experimental drug and no other treatments for Alzheimer's showed a reduced rate of brain atrophy, according to the findings presented Wednesday at the Alzheimer's Association International Conference (AAIC) in Toronto, Canada.
"The study results failed to demonstrate a treatment benefit on either of the co-primary outcomes at either dose in the prespecified primary analysis," said study author Serge Gauthier, neurology professor at McGill University.
"However, additional analyses are very encouraging and showed that patients taking LMTM as monotherapy had significantly lower decline than control patients or those taking LMTM as an add-on to existing Alzheimer's treatments."
Researchers reported "a statistically significant benefit on cognitive and functional outcomes, and slowing of brain atrophy" in this smaller subgroup.
The findings are part of the first completed phase III trial of an anti-tau drug in Alzheimer's.
"In a field that has been plagued by consistent failures of novel drug candidates in late-stage clinical trials and where there has been no practical therapeutic advance for over a decade, I am excited about the promise of LMTM as a potential new treatment option for these patients," added Gauthier.
Outside experts urged caution in interpreting the results.
The findings are "interesting but also complex, and it will take time for the field to determine what they mean," said Maria Carrillo, the chief science officer at the Alzheimer's Association.
"The small number of participants receiving the study drug as monotherapy raises very important questions. Additional research is needed to help us understand these findings so that more and better Alzheimer's therapies can be created and effectively tested."
A full 80 percent of study participants also reported at least one adverse event, including disorders of the gastrointestinal or nervous system, infections and infestations, and renal and urinary problems.
Almost 47 million people around the world are living with dementia, according to Alzheimer's Disease International, a number that is expected to skyrocket to 131.5 million by 2050.
There is no cure for Alzheimer's disease. In the past 20 years, the US Food and Drug Administration has approved five drugs to treat its symptoms.