Researchers see FDA uncertainty behind hold on ESC work

The news that the FDA had put a ‘clinical hold' on Geron's plans to launch the first U.S. clinical trial of a stem cell therapy is attracting considerable scrutiny from researchers. The agency has yet to spell out exactly why it won't let Geron make the leap from preclinical work to a human trial. But Ole Isacson, a neuroscientist at Harvard Medical School, tells Nature that any outfit in Geron's position would have to offer convincing data that none of the transplanted cells could trigger a tumor or some other adverse event.

The problem in ESC research, he adds, is that no one has firmly established the criteria for that standard. Meanwhile, the FDA is still educating itself on the subject, and that is likely to give the agency pause before any human embryonic stem cell trials can be started.

At least one analyst, Steven Brozak of WBB Securities, has fretted that the Bush administration's objections to embryonic stem cell work may have forced the FDA's hand, but researchers say there's every reason to believe that the FDA simply doesn't know how to make sure the trials can be conducted safely. And that could prove to be a much bigger obstacle than politics for other ESC companies also looking to move into the clinic.

- read the article from Nature