LONDON ¿ Stem cell specialist ReNeuron plc has agreed to an alliance with VistaGen Inc. to exploit the commercial potential of stem cells as a drug discovery platform. In exchange for a phased equity stake in VistaGen, ReNeuron has granted exclusive rights to its neuronal stem cells for predictive screening of drugs for toxicity.

Martin Edwards, CEO of ReNeuron, told BioWorld International, ¿VistaGen will use our stem cells to predict if lead compounds will be toxic. For example, if a drug is added to liver stem cells, what does this do to gene expression? We believe using stem cells in drug discovery could be an important source of novel genes and proteins.¿

Edwards said the deal is important because it validates the concept of stem cells as a route to drug discovery and it broadens ReNeuron¿s technology base. ¿We could do other deals elsewhere once the concept is validated,¿ he said.

ReNeuron, based in Guildford, UK, also said that it is having problems ramping up production of stem cells for its lead product for the treatment of stroke. This means Phase I trials will not start this year as planned.

¿We can make plenty of cells, and they all continue to divide rigorously. But at high-population doubling they show some instability, and so I don¿t think we would get approval [to use them] for the trial,¿ Edwards said.

The manufacturing problem is not related to the temperature mechanism that ReNeuron has introduced into the cells to enable them to be turned off and on once they are injected into patients.

The company is working on a number of ways around the problem, but Edwards said it is not clear how long the delay will be.

ReNeuron has developed clonal lines of pluripotent neuroepithelial stem cells, which differentiate into different types of brain cells in situ after grafting. The cells are immortalized, allowing them to be grown and expanded indefinitely in appropriate culture conditions. After implantation by injection, they migrate to the site of damage, allowing some flexibility over the transplant site.

Using the mouse cell line MHP36, the company has demonstrated functional recovery in rats following strokes, with cells migrating from the site of insertion to the site of the damage, differentiating into both neurons and glia, and repairing the behavioral deficit.

ReNeuron has developed more than 100 human cell lines from different regions of the brain. Aside from stroke, it intends to develop stem cell lines for treating Parkinson¿s, Alzheimer¿s and Huntington¿s diseases and cerebral palsy.

The cell lines are conditionally immortalized, enabling the cells to divide in the laboratory at temperatures of 33 degrees Celsius. Division ceases, and the cells mature, when implanted into the brain where the temperature is higher at 37 C.

The Phase I/IIa trial in stroke will involve about 12 patients who have reached a stable condition three to six months after suffering a stroke.

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