The risks of employing a cell-based therapeutic in any given condition, or for any individual patient, must be must be weighed against the efficacy, risks and costs of the standard of care for that disorder. While this is an easy calculus when one is dealing with untreatable and otherwise fatal disorders, such as the childhood leukodystrophies or Huntington disease, it is a more nuanced issue when one considers disorders for which some effective treatment is already available, when lifespan is not necessarily threatened by the disease process, or for which the costs may be high for only incremental improvements in condition or lifespan. The example of Parkinson’s disease, noted previously, is especially instructive in this regard, as essentially all of these considerations come to the fore: multiple effective treatment modalities already exist that are effective for the majority of patients, lifespan is only threatened after the development of refractory disease, most typically in the late elderly, and both the costs and risks of treatment may be significant. Yet for a minority of younger patients with early refractory disease, cell-based dopaminergic
