Current status of clinical trials of neural transplantation in Parkinson's disease.

ABSTRACT

There is a major unmet need for therapies for Parkinson's disease (PD) that go beyond treating symptoms and instead modify the course of the disease. The use of neural transplantation to repair the degenerating dopaminergic nigrostriatal pathway is one strategy by which this might be achieved. A series of small, independent open-label studies initially reported beneficial effects in patients treated with cell transplants derived from the fetal ventral mesencephalon. However, this initial promise was subsequently tempered by negative results from two larger, randomized studies, and the emergence of complications related to the procedure. The reason for these discordant results has been debated and this has led to the development of a new, multicenter, collaborative study--TRANSEURO--which will ultimately herald the next generation of clinical trials of cell therapy in PD, including those involving stem cells. In this chapter, we discuss what has been learned from previous studies of neural transplantation and go on to consider how relevant disease-modifying effects could be demonstrated in PD. We then go on to discuss how the design of future trials of transplantation-based therapies might be better conceived and executed.