Clinical trials of neural transplantation in Huntington's disease.

Clinical neural transplantation in Huntington's disease has moved forward as a series of small studies, which have provided some preliminary proof of principle that neural transplantation can provide benefit. However, to date, such benefits have not been robust, and there are a number of important issues that need to be addressed. These include defining the optimum donor tissue conditions and host characteristics in order to produce reliable benefit in transplant recipients, and whether, and for how long, immunosuppression is needed. Further clinical studies will be required to address these, and other issues, in order to better understand the processes leading to a properly functioning neural graft. Such studies will pave the way for future clinical trials of renewable donor sources, in particular, stem cell-derived neuronal progenitor grafts.