Human trials for neurodegenerative disease.

The lack of disease-modifying treatments currently available for not just some but most neurodegenerative diseases, including Parkinson's disease, Huntington's disease, and even stroke, helps explain increasing interest in cell-based therapies. One key aim of such treatment is to replace neurons or glia lost as a result of the disease, with a view to the cells integrating functionally within the host tissue in order to reconstruct neural circuitry. Clinical trials using primary human fetal tissue as a cell source commenced in Parkinson's disease (PD) in the 1980s; currently, comparable neural transplantation trials in Huntington's disease are underway. Disappointing results of later controlled trials in PD illustrated not least the vital importance of methodological issues relating to the structure and implementation of clinical trials, and these issues will be considered here in more depth.