Doctors believe that a last-ditch attempt to save the life of a 19-year-old with vCJD may have slowed the progress of the disease.
Jon's condition may have improved
Jonathan Simms, from Belfast, had been given only months to live before the experimental drug pentosan polysulphate (PPS) was injected into his brain last year.
Experts meeting in Belfast on Friday to review the initial results of his case say that the drug appears to be safe - and may have improved his condition.
However, more research may be needed before it can be confirmed as a treatment for vCJD.
Jonathan's father Don took High Court action to secure permission to treat him.
Doctors say that vCJD is invariably fatal in both young and old and usually takes hold rapidly. No other treatment has yet been found that slows its progress.
Hope for treatment
Experts say that, even if this ground-breaking treatment does not cure the illness, it could delay the deterioration of patients, significantly extending their lives.
Despite campaigning by Don Simms, Jonathan had already suffered extensive brain damage by the time he was finally allowed to have the drug eight months ago.
As Jonathan is an adult - but incapable of giving consent to treatment - the High Court had to decide last year whether the risks of using him, effectively, as a "human guinea pig" outweighed the potential benefits.
Dame Elizabeth Butler Sloss gave the go-ahead and the injection - directly into the brain - was given shortly afterwards.
Jonathan remains severely disabled - he is confined to bed, with limited ability to move or interact with visitors, and has to be fed through a tube into his stomach.
He requires round-the-clock nursing from his family.
While there is no expectation that this can ever be fully reversed, doctors familiar with his case say that his progress has been encouraging.
Most importantly, his ability to swallow - an important indicator of his basic brain functions - has returned after disappearing as his condition worsened last year.
His parents say he is more alert, can respond to verbal instructions, and is even attempting to utter words, such as "mum" and the name of his new baby sister.
Don told the BBC: "It's not perfect but it's an awful lot better.
"But we're even pleased that Jonathan is still living. We take each day as it comes.
"I would hope that those who had their doubts about pentosan polysulphate would realise that, nine months on, we have no adverse side-effects."
He said that while pentosan might not restore Jonathan's health, it might buy time while other medical research, such as stem cell therapy, came to fruition.
It is hard to test the precise effects of pentosan on the brain, but a new form of testing which measures changes in heart rate might offer some clues.
Variations in heart rate are a common feature of vCJD - they are thought to be caused by damage to the "brain stem" - a key area of the brain.
Tests on Jonathan's heart rate variation before and after treatment show distinct changes which have not been spotted in another vCJD patient given the tests.
The researcher behind the test, Dr Chris Pomfrett, a lecturer in neurophysiology from the University of Manchester, told BBC News: "It's very encouraging we have seen this change - Jonathan is quite unique."
Nikolai Rainov, a consultant neurosurgeon from the Walton Centre for Neurology and Neurosurgery in Liverpool, believes Jonathan's progress is promising.
He told the BBC: "The question of efficacy is still very much open.
"Some neurological functions have improved significantly over the course of treatment.
Jonathan is nursed by his family
"We believe that the brain stem now functions better than it did six to eight months ago.
"The patient is even able to obey commands - something which was not the case six months ago."
He said that the drug, if backed by further successful studies, could help vCJD patients survive longer, with a better quality of life.
He said: "I believe that what would be achievable is a significant extension of the lifespan of these patients if treatment was instigated at an early stage.
"I am sure that earlier treatment would have been beneficial to him [Jonathan]."
BBC health correspondent Karen Allen said she understands three other families of vCJD victims are now lobbying to access the same treatment, but it is unclear whether they too will have to face a court battle.