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Finding an effective treatment for Alzheimer’s disease

Professor Louise Serpell, Professor of Biochemistry (Sussex Neuroscience) at the ÌìÃÀ´«Ã½Ó°ÊÓ, is working with TauRx Therapeutics Ltd, a pharmaceutical company which aims to commercialise products for the diagnosis, treatment and cure of neurodegenerative diseases. Her lab is working to understand how a therapeutic drug compound developed by TauRx, now in Phase 3 clinical trials, is working at the molecular level.

“My sons used to map the Alzheimer’s breakthrough stories they saw in the media, and used to make fun of them,” said Professor Claude Wischik, Chief Executive of TauRx Pharmaceuticals and Professor of Old Age Psychiatry at the University of Aberdeen. “This is not an Alzheimer’s breakthrough story – this is the real deal. We have the most advanced Tau-based programme in the world.”

TauRx Pharmaceuticals Ltd, headquartered in Singapore with its research centre in Aberdeen, has just completed two large phase 3 trials of their compound, called hydromethylthionine, in over 20 countries with 1,686 Alzheimer’s disease patients. This trial compared a low dose intended as a control (8 mg/day) with high doses of their compound in the range 150-250 mg/day. has found that the low dose had effects on reducing cognitive decline and brain atrophy in the majority of patients receiving it and identified 16 mg/day as the predicted optimal dose. “The treatment effects that we have seen are about three times the magnitude of currently available treatments,” said Wischik.

Following those trials, TauRx has started a new phase 3 clinical trial to confirm the safety and effectiveness of the compound at the 16 mg/day dose compared with placebo in 450 patients in medical centres in Britain, France, Italy, Spain, Belgium, Poland, Canada and US. If the trial is successful, the results will be submitted for regulatory review so that the compound can be made available for wider use with patients.

The brain in a patient with Alzheimer’s disease may begin to change years before patients begin to show a decline in brain functioning, generally characterised by confusion, increasing memory loss and difficulty carrying out daily activities. Researchers think that changes which lead to the development of Alzheimer disease are caused by two different proteins: Amyloid Beta and Tau, although there is controversy over which is more important.

In Alzheimer’s and other neurodegenerative diseases, Tau protein forms deposits called neurofibrillary tangles inside brain cells, while Amyloid-beta clumps into plaques which form outside the cells. The TauRx therapeutic compound is designed to prevent the Tau protein from aggregating.

Supporting the most advanced Tau-based programme in the world

While TauRx knows the promising therapeutic compound has greater activity on brain structure and function than current treatments, it has been working in close collaboration with Serpell and her lab over the past five years to understand better how the compound works. “Our experiments aim to provide an understanding of how the molecule binds to the protein and how it might protect the neurons against the toxic effects of the Tau protein,” Serpell said. The lab has produced a model system to make the neurofibrillary tangles in vitro (in test tubes). Then they test the compound on those tangles to understand how it prevents self-assembly.

“This work has permitted us to map how the drug is binding inside the Tau unit,” said Wischik. “We’re close to being able to define it at the atomic level.” This detailed understanding of the tau protein could potentially also help TauRx identify compounds that are even more effective at treating Alzheimer’s disease in patients.

“We want to understand how the abnormal aggregates of Tau propagate in the brain,” said Wischik. “Once the process begins it spreads from one cell to the next and creates the same sort of damage exponentially in other brain regions. So it’s immensely destructive and yet it’s highly ordered. We’ll need all the strengths that Prof Serpell can bring to bear to understand that.”

The collaboration funds two Post-Doctoral researchers in Serpell’s lab who meet every three months to share research findings with the company. “I feel like it’s a give and take collaboration,” said Serpell. “We have academic discussions with them about the work. We are co-designing approaches.”

The collaboration has also opened up new research avenues for the Serpell lab as, prior to the collaboration, they mostly focussed on the Beta-amyloid protein. “We’ve developed a bigger picture understanding of the causes of Alzheimer’s disease,” said Serpell.

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I really would hope that in the next five years we will see some treatments for Alzheimer's.” Louise Serpell 
Professor of Biochemistry, ÌìÃÀ´«Ã½Ó°ÊÓ

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Dementia: third leading cause of death in high-income countries

“Dementia is now the most feared condition in the over 65s. More than cancer, more than arthritis, more than anything,” said Wischik. “That makes complete sense because the things that you have been working for all your life – the holidays you planned, the life after retirement, it evaporates in smoke. It’s a huge tragedy and squandering of human life and potential.”

Worldwide, around 50 million people . Alzheimer’s disease is the most common cause of dementia. Alzheimer’s and other dementias are already the third leading cause of death in high-income countries, after stroke and heart disease, according to the .

As people are living longer, the potential societal and economic impacts of the disease are growing given that the risk of dementia rises more or less proportional to age. The potential market for an effective treatment is large, and the societal and economic benefits are almost impossible to calculate, but certainly immense. Excitingly, both Serpell and Wischik believe a treatment is in sight.

“I really would hope that in the next five years we will see some treatments for Alzheimer’s,” said Serpell. “We’ve made huge progress in the last ten or fifteen years in terms of understanding the disease and we’re at a really good time to be able to develop drugs that at least slow the progression of the disease.” That could be good news for the roughly 850,000 people in the UK alone living with Alzheimer’s disease.

In addition to the compound, TauRx is developing diagnostic tools to help GPs better identify patients at risk of developing Alzheimer’s. Wischik is hopeful that these tools, combined with the compound, will bring hope to patients. “My vision is that by having the tools and an effective drug, people are better able to accept that they have Alzheimer’s because there is a hope attached to that.”

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Reference:
Schelter, B O et al. (2019) . Journal of Alzheimer’s Disease, vol. Pre-press, no. Pre-press, pp. 1-16, 2019. DOI 10.3233/JAD-190772

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