Abstract
Clinical trials for gene-therapy products began in the 1990s. Currently, most of the 630 completed or on-going trials are in Phase I and II. Because of the safety issues surrounding the use of viral vectors, approx. 25% of the ongoing clinical trials use DNA plasmids to carry the corrective gene (http://www.wiley.co.uk/genmed). The purpose of this perspective (and this issue) is to highlight some of the unique technical challenges and potential solutions associated with the manufacture and expression of a plasmid-based gene-therapy product.