The first product derived from embryonic stem cells has been placed on clinical hold by the FDA, according to a company announcement today. Geron’s product GRNOPC1 consists of oligodendroglial progenitor cells derived from embryonic stem cells and is being developed to treat acute spinal cord injury. The clinical hold means that Geron will not be able to start its trial, presumably until it addresses concerns raised by the FDA. In a statement, Geron said that it had received only verbal communication about the clinical hold and could not yet offer an explanation of the decision.

Geron was one of three companies invited to present to the FDA in April about what evidence needed to be presented about the safety of such products. The FDA’s chief concerns were 1) characterization of cell product (are the mixtures of cells predictable and free from contamination?) 2) the possibility for unwanted growth and differentiation both from the desired cell type and contaminating cells 3) potential unpredictability of cells 4) difficulty in monitoring cells for harmful effects or retreiving cells for such reasons. Also, the FDA was concerned that the animal tests performed to evaluate cells could be much less predictive even than for animal tests for small molecule or protein drugs.

CIRM’s scientific head, Marie Csete, has clearly explained the issues of putting cells into people in an interview.

I covered the FDA meeting in April with two blog posts:

Gearing for nitty gritty questions in clinical trials

plus an overview of the meeting.

A comment in the overview links to the slides and transcripts of the meeting.