Researchers believe they have found an "exciting new potential therapy" for motor neurone disease (MND), with a drug commonly used for other health treatments.
MND is a group of rare diseases that destroy cells called motor neurons and causes patients to slowly lose the function of their muscles.
About 5,000 people are thought to be living with the incurable disease across the UK - the average life expectancy after the onset of symptoms is about three years.
The treatment could slow the progression of paralysis associated with MND.
Scientists said they have taken an "important step" with a drug currently used to treat enlarged prostates and high blood pressure.
The research at the University of Edinburgh showed the drug terazosin protects against the death of motor neurons in zebrafish, mice and stem cell models by increasing energy protection.
Alongside partners at Oxford University, the experts wanted to determine if the drug could also protect motor neurons from MND.
Dr Helena Chaytow, senior postdoctoral researcher at University of Edinburgh's Euan MacDonald Centre and first author of the study, said: "Our work shows that terazosin is protective of motor neuron cell death in multiple models of MND, making it an exciting new potential therapy.
"The benefit of working with terazosin is that it is already prescribed for a different health condition, so we know that it is safe for humans and could quickly move to the clinic."
Professor Kevin Talbot, Professor of Motor Neuron Biology at the University of Oxford and study co-lead, added the work "represents an important new step in the search for therapies".
The research focused on an enzyme - an active molecule in the cells - involved in energy production called PGK1.
'Terazosin delayed progression of paralysis'
Motor neurons were grown in a dish and experts demonstrated that terazosin protects these cells by increasing energy levels.
Terazosin also protected motor neurons in a mouse model of MND, improving survival and delaying the progression of paralysis.
The scientists believe this could slow the progression of the disease in humans and are looking into launching a clinical trial.
Fifty patients have been invited from the Oxford MND Care and Research Centre to participate in a feasibility study which will examine the impact of terazosin on key indicators of disease progression.
A number of high profile British sportsmen have shared their experience with MND in recent years, including rugby league's Rob Burrow, rugby union's Doddie Weir and footballer Stephen Darby.
Professor Stephen Hawking also had the disease, but lived for 55 years after his diagnosis at the age of 21 - despite being given two years to live.