As many would-be biotech entrepreneurs have learned, one of the scariest things about bringing a new biomedical technology into the world is when an unexpected and very public problem crops up, especially during clinical trials. You can't tell if you've merely hit a bump in the road or run smack into a brick wall. At the moment of impact, they feel much the same.

The road to gene therapy, which has been nothing if not rocky over the last two decades, hit another one of those sickening bumps last September, when word spread from Philadelphia that a fatality had occurred in a gene therapy trial at the University of Pennsylvania's Institute for Human Gene Therapy. Eighteen-year-old Jesse Gelsinger, according to university officials, died four days after receiving experimental treatment for a genetic disorder known as ornithine transcarbamylase (OTC) deficiency. In reporting the episode, publications like the Wall Street Journal suggested that the death was "raising new questions" about a beleaguered technology.