FDA puts brakes on Geron stem cell trial--again

Last week the New York Times reported that the FDA put a clinical hold on Geron's pioneering human embryonic stem cell (ESC) trial—before the first patient could be enrolled. In what was to be the world's first clinical test of ESCs, Geron planned to differentiate the cells into neurons that can be injected into the spinal cords of paralyzed patients. However, the FDA requested more information after reviewing dose escalation data from pre-clinical animal studies.

This is the second time the FDA has delayed the Geron ESC clinical trial. Back in January, the FDA lifted an 8 months hold, allowing Geron to proceed with plans for the experimental injection of ESC-derived nerve cells into the spines of 8-10 paralyzed patients in attempt to repair the neural damage. The FDA was concerned over the safety of the protocol since the presence of any contaminating, undifferentiated ESCs could form tumors called teratomas.

In an announcement released Friday by Geron, the company explained that a recent animal study of the GRNOPC1 ESC therapy revealed the presence of “microscopic cysts in the regenerating injury site.” Fortunately the cysts were only found in the injection site and were non-proliferating. That is significant since it means that the cysts were benign, nevertheless, the FDA wants to look more closely at this development.

"We have submitted these data to the FDA and are in discussions with the agency to answer its questions and proceed with the clinical trial," said the company in the release.

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