Can an over-the-counter cough medicine slow the progress of Parkinson’s disease? A world-first Phase III clinical is about to find out.

UK researchers are investigating Ambroxol – a medicine sold in Australia as Bisolvon – as a potential treatment for the neurodegenerative disorder.

Ambroxol – typically taken to break down phlegm and ease congestion –has been found to boost the levels and activity of an enzyme called beta-glucocerebrosidase (GCase).

Why is this enzyme important?

GCase helps break down and effectively recycle waste material from nerve cells, including alpha-synuclein, a biomarker for Parkinson’s.

More than that, alpha-synuclein is a toxic aggregate in Parkinson’s thought to contribute to nerve cell loss and disease symptoms.

GCase is important in Parkinson’s because some people with the condition have genetic mutations in the region of DNA that provides the instructions for making GCase.

The gene is called GBA. Variations in the GBA gene can increase an individual’s risk of developing Parkinson’s.

Clinical assessments promising

There are no treatments available for Parkinson’s that slow, stop or reverse the disease.

But clinical assessments of participants in a Phase II clinical trial of Ambroxl in the UK – designed to test tolerance and safety – suggest that “the treatment improved motor symptoms associated with Parkinson’s”.

However, The Cure Parkinson’s Trust which funded the research, said the trial “was not designed to test disease modification because it was a small cohort safety study without placebo control, therefore the clinical outcomes in this part of the trial should be interpreted with caution”.

The clinical trial

Professor Anthony Schapira, head of the Department of Clinical Neurosciences, and his research team at University College London and the Royal Free London Hospital, conducted the trial.

They confirmed the safety and tolerability of Ambroxol (1.26g/day) in 17 people with Parkinson’s over six months. There were no adverse reactions reported.

The drug was found to cross the blood-brain barrier – and achieved “a good level of penetrance into the brain”.

Researchers reported a 35 per cent increase overall in levels of the GCase enzyme levels found in participants’ cerebrospinal fluid.

For the study, the dose of Ambroxol was reportedly about 10 times higher than when taken as a cough medicine and was taken longer than its licence allowed.

Phase III trial to begin this year

A phase 3 clinical trial will begin this year to establish Ambroxol’s potential to slow the progression of Parkinson’s disease.

The trial will be conducted by University College London and led by Professor Schapira.

The trial will involve 330 people with Parkinson’s across 10 to 12 clinical centres in the UK. It will be placebo controlled and participants will take Ambroxol for two years.

The effectiveness of the drug “will be measured by its ability to slow the progression of Parkinson’s using a scale including quality of life and movement”.

Professor Schapira said: “I am delighted to be leading this exciting project. This will be the first time a drug specifically applied to a genetic cause of Parkinson’s disease has reached this level of trial and represents 10 years of extensive and detailed work in the laboratory and in a proof of principle clinical trial.”