Clinicians at Glasgow's Southern General Hospital have already given six stroke patients the ground breaking stem cell therapy with promising results.
Yesterday they announced they had been given permission to progress the trial to its next stage, increasing the dose which sufferers will receive.
Professor Keith Muir, principal investigator in the trial, said: "We are pleased the trial is progressing well and all the patients treated so far have shown no adverse effects. We are pleased to have successfully completed cell injection in the first patient at the new, higher, dose and remain encouraged by the results of the study thus far."
Earlier this summer the team revealed five of the six patients treated had shown signs of improvement after the stem cells were injected into their damaged brain tissue.
Within three months their disability ratings halved from eight to four. Results have not yet been released for the sixth participant.
Changes included better thumb and finger movement, better strength and stability in the legs and improved speech.
A total of 12 patients left disabled by the most common form of stroke are expected to be treated as part of phase one of the trial.
Michael Hunt, chief executive officer of life sciences firm ReNeuron, said: "We are delighted the Data Safety Monitoring Board has given a favourable recommendation to proceed to the higher and penultimate dose in the stroke trial."