Geron, a California company developing therapies derived from embryonic stem cells, announced on Monday that the first patient has been treated in its landmark trial for spinal cord injury. The therapy, which involves injecting differentiated neural cells into the injury site, is the first such treatment to be tested in humans. Other experimental stem cell therapies involve adult stem cells or cells derived from fetuses.

Geron first garnered approval for the tests from the U.S. Food and Drug Administration in January of 2009. But that approval was put on hold several months later due to new safety concerns from animal tests. Because cells can behave unpredictably, regulators want to make sure the transplanted cells don’t develop into teratomas, a type of tumor associated with the injection of embryonic stem cells.The FDA gave permission to resume testing in July, after another round of animal safety tests. This early stage trial is designed to assess the safety of the therapy in humans and will involve a small number of patients with new injuries; the treatment must be delivered within 14 days of the injury.

The cell therapy is made by transforming embryonic stem cells into oligodendrocytes–a type of brain cell that wraps itself around neurons, forming a fatty insulation layer that allows electrical messages to be conducted throughout the nervous system. These cells are often damaged in spinal cord injury, while the underlying nerve cells remain intact. When the new cells are injected into the site of the injury in animals, they coat exposed nerves and restore communication to the nervous system.

In 2005, Hans Keirstead and collaborators at the University of California, Irvine, showed that paralyzed rats injected with the cells were able to walk again. Since then, Geron has been conducting numerous studies intended to show the safety of the cell-based therapy, as well as developing production methods that would make the cells as easy to use as more traditional treatments. Geron researchers have also developed a way to reliably freeze and thaw brain cells, so that they can be manufactured in a central location, and then shipped to the hospitals where they will be used.

The first patient in the study was enrolled at the Shepherd Center, a private, not-for-profit rehabilitation hospital in Atlanta, Georgia. It is one of seven potential sites in the United States that may enroll patients in the clinical trial. According to Geron,

Northwestern Medicine in Chicago, IL is also open for patient enrollment. As additional trial sites come online and are ready to enroll patients, they will be listed on the Patient Information pages of Geron’s website and on the NIH clinical trials registry, ClinicalTrials.gov.