Geron Says Some Animals Developed Cysts In Trial

MENLO PARK, Calif. (AP) — Geron Corp. said Thursday that a human clinical trial of its embryonic stem cell product is being delayed because some of the animals treated with the injection developed microscopic spinal cysts.

Geron is testing GRNOPC1, an injection of human stem cells, for spinal cord injury. The company has been testing the product on rats and mice, and hopes to begin human clinical trials soon. However the FDA placed the program on hold on Aug. 18, saying it wanted to review new data from the animal studies. Neither Geron nor the FDA have said how long the current review will take.

"A very low frequency of injected animals developed microscopic cysts in the regenerating injury site," Geron said. The company said the cysts were harmless, did not spread to other parts of the body and were not connected to increased risk of death or other health problems. None of the animals developed tumors, Geron said.

Geron said as many as half of all spinal cord injury patients develop much larger cysts in their spinal cord tissue. The company said it recently finished another study of the product on animals, and it found a higher frequency of cysts. It said they were similar to the cysts that were seen in other trials.