The drug which Jonathan Simms will be given has been around for many years but has never before been approved as a treatment for humans with CJD.
Pentosan Polysulphate has been used in the US and Germany against inflammation of the bladder.
It has also been used by vets to treat arthritis in animals such as dogs and horses.
But animal experiments have suggested it could work against the prion proteins understood to play a key part in the development of new variant Creutzfeldt- Jakob disease (vCJD).
If the drug was injected into the body, the natural barrier between the bloodstream and brain would prevent it reaching the brain. This means, in order for it to have any chance of working, it must be injected straight into the brain itself.
A catheter tube has to be inserted into the brain so that doses of the drug can be administered. Those in favour of the drug being used have said evidence from animal studies suggests it might be able to lengthen the incubation period of the disease, thereby halting the speed of its progression.
They claim there is enough evidence to justify its use in humans, particularly those in the advanced stages of the disease, who have no alternative treatment on offer.
Others, however, believe the treatment could expose the patient to unnecessary risk as not enough safety research has been done.