LONDON ¿ ReNeuron Holdings plc said it has failed to solve stability problems with the human neural stem cells it was hoping to take into clinical trials in stroke and it now plans to bring forward a program for development of murine neural stem cells in the treatment of Huntington¿s disease.

The company said it requested a meeting with the FDA to discuss the issues involved in getting permission for xenotransplants into the brain.

CEO Martin Edwards told BioWorld International, ¿The FDA is familiar with the issues and has approved cell transplants and xenotransplants to the brain.¿ The company was planning to carry out its first trial in the UK, but Edwards said the switch to murine cells would make it far more difficult to get the go-ahead because to date no UK trials involving xenotransplants have been approved.

¿In the UK you need the approval of three separate committees, and it is too big a risk that someone will raise a red flag.¿

The company has selected Huntington¿s disease as its first indication because there is no existing treatment, and as an orphan indication the number of patients that must be treated is low. One U.S. company, Diacrin Inc., of Charlestown, Mass., has completed a Phase I trial, treating 12 Huntington¿s patients with transplants of porcine neural stem cells to the brain.

Edwards said ReNeuron, based in Guildford, Surrey, would maintain its focus on developing human neural stem cells for transplantation, but could not find any short-term solution to increase the genetic stability of its cell lines. However, the company now understands the problem and is re-deriving its cell lines using novel immortalizing techniques. This will take two years.

¿In addition, we have taken an exclusive license on a novel immortalizing gene,¿ Edwards said.

As a result of the problems, ReNeuron has decided to expand its activities outside stem cells, and has licensed in two soluble receptor proteins from the University of Bristol and Enact Pharma plc, with potential applications in pain and inflammation. In addition, the company made a second deal to use its stem cells in drug discovery, announcing an agreement with Psychiatric Genomics Inc., of Gaithersburg, Md., to use its cell lines for functional gene discovery and screening compounds in mental disorders. Earlier this year ReNeuron entered a deal with VistaGen Therapeutics Inc. to use its cell lines in toxicity testing.