LONDON - A pioneering clinical trial to inject stem cells into the brains of patients disabled by stroke has been cleared to progress to the next stage after the treatment raised no safety concerns in the first three candidates.

ReNeuron Group PLC , the British biotech behind the trial, said the independent Data Safety Monitoring Board had reviewed safety data from its ReN001 stem cell therapy and recommended the trial advance to the higher dose.

"Data from the laboratory safety tests, neurological examinations and neurofunctional tests conducted thus far indicate that the ReN001 treatment is safe and well-tolerated at the initial dose," the company said in a statement on Thursday.

The procedure involves injecting ReNeuron's neural stem cells into patients' brains in the hope they will repair areas damaged by stroke, thereby improving both mental and physical function.  

It uses stem cells derived from human foetuses rather than embryos, which were used in a stem cell trial to treat patients with spinal cord injuries by Geron Corp of the United States.  

ReNeuron's chief executive Michael Hunt said the clearance was an important milestone, and the preliminary data also backed up the group's other therapeutic programmes using the CTX neural stem cell line that formed the basis of the ReN001 stroke treatment.  

The principal investigator for the trial, Keith Muir from the University of Glasgow's Institute of Neuroscience and Psychology, said he looked forward to evaluating further patients at a higher dose.

"ReN001 has the potential to address a very significant unmet medical need in disabled stroke patients and I am pleased that our team is involved in this pioneering clinical trial," he said.

Shares in ReNeuron rose 3.3 percent in early trade.

Analysts at Matrix said ReNeuron was making excellent progress within the trial, which it believed could set the company apart from other stem-cell companies in the field, given the other advantages it has in terms of manufacturing, scalability and the off-the-shelf nature of the technology.  

"The data generated thus far are all the more remarkable, in our view, given the fact that the patients receiving the cells have not been subject to immunosuppression" they said in a note.

"We look forward to the data from the next cohort within this study."