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Animals being tested using Geron Corporation’s treatment for spinal cord injury developed cysts at the injury sites, a finding that led the U.S. FDA to place a clinical hold on a planned human trial of the treatment, the Menlo Park, Calif.-based stem cell firm said on August 27.
However, Geron said, the cysts did not spread, did not harm the lab animals, nor did they lead to teratomas, a form of tumor that is usually, but not always, benign.
Recent testing of the product showed no cyst development, according to the company.
[Editor’s note: the formation of teratomas with all three embryonic germ layers (endoderm, ectoderm, mesoderm) in specially-prepared mice injected with pluripotent cells is the gold standard for determining whether a human embryonic stem cell (hESC) line has been created. Researchers are concerned, however, about the development of any tumors in humans using hESCs.]
Geron said in a statement that ongoing testing of its hESC-based product GRNOPC1 in live animals found that “a very low frequency of injected animals developed microscopic cysts in the regenerating injury site” but the cysts were “non-proliferative, confined to the injury site, and had no adverse effects on the animals,” and the animals did not develop teratomas.
Geron said, “Cysts of much larger size appear in the spinal cord scar tissue of up to 50 percent of patients with spinal cord injury.”
Ongoing testing in animals showed “a higher frequency of cysts, although their characteristics were similar to the cysts seen in previous studies: non-proliferative, confined to the injury site, smaller than the injury cavity and not associated with adverse clinical outcomes.”
Geron said it recently tested samples of GRNOPC1 in spinal cord injured rats using new markers and assays and found no cysts.
“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,” Geron said in a statement. “We are committed to the optimization of all our hESC-based products as we improve the manufacturing process and identify improved product release criteria.”
Contact: http://www.geron.com
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