A world-first clinical trial is combining a commonly used antibiotic and a cough medicine to fight some of the processes that cause a common form of dementia.
Researchers at Macquarie University hope the combination of the antibiotic doxycycline and the cough medicine ambroxol may even stop dementia with Lewy bodies (DLB) in its tracks.
DLB is the second most common form of dementia after Alzheimer’s disease, and has a much more aggressive and swift course of progression.
It is closely related to Parkinson’s disease, with symptoms including problems with thinking and movement, as well as changes in mood, sleep disturbances, hallucinations, and losing the sense of smell.
Macquarie University Professor of Cognitive Neurology Simon Lewis specialises in degenerative diseases of the brain, including DLB and Parkinson’s disease.
“Dementia with Lewy bodies is more common than most people realise, because the overlap of symptoms with other conditions means it is commonly misdiagnosed,” Professor Lewis said.
“About 20% of Australian dementia patients are likely to have DLB rather than Alzheimer’s, and some people with DLB may even be misdiagnosed as having Parkinson’s.
“In some cases, the hallucinations and mood disruptions may lead people to believe they have a mental health condition, as was the case with actor Robin Williams, who sadly was not diagnosed with DLB until after his death in 2014.”
Until recently, the only way to conclusively prove DLB was at autopsy, but blood tests are now being developed to diagnose the disease in living patients.
In the meantime, Professor Lewis says three telltale symptoms can be useful for confirming DLB in patients with dementia: acting out dreams (for example, punching or kicking while asleep), the loss of the sense of smell, and physical changes such as a shuffling gait or tremor.
Proteins linked to neurodegeneration
Abnormal build-ups of naturally occurring proteins in brain cells have been shown to be associated with a number of neurodegenerative diseases, including Alzheimer’s, frontotemporal dementia, motor neurone disease, Parkinson’s and DLB.
Lewy bodies are clusters of the protein alpha-synuclein in dying brain cells that can be seen through the microscope in post-mortem tissue in both DLB and Parkinson’s.
In the lab, the antibiotic doxycycline has been shown to prevent alpha-synuclein from forming these damaging clumps in the first place; while the anti-mucosal ambroxol, which is used to treat coughs, boosts the production of an enzyme that can clear clusters of this protein.
In the current phase II clinical trial, it is hoped the combination of the two drugs will attack on both fronts, slowing or even stopping the progression of DLB in people who are already experiencing symptoms.