Repair work: This animation shows glial progenitor cells, made from human embryonic stem cells, repairing nerve damage. Credit: University of California, Irvine

Geron, a California-based cell-therapy company that has been working with embryonic stem cells for the last decade, finally received clearance from the U.S. Food and Drug Administration to begin clinical trials of its cell-based therapy for spinal-cord injury.

The trial is limited to eight patients with newly acquired spinal-cord injuries who will receive injections of the cell therapy, called GRNOPC1, within two weeks of their accident. GRNOPC1 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. In many spinal-cord injuries, these cells are damaged, but the underlying nerve cells remain intact. These cells are then injected into the site of the injury, coating exposed nerves and restoring communication to the nervous system.

Scientists published the results of a successful study testing the therapy in animals in 2005, showing 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.

Because embryonic-stem-cell-based therapies are so new, the FDA has had trouble deciding how to evaluate new drug applications. (Geron's president and CEO, Thomas Okarma, thought approval was imminent when I spoke with him in 2006. See "Human Tests of Embryonic Stem Cell Treatments Planned.") The initial trial is designed to assess safety, but doctors will also measure its effectiveness, such as improved neuromuscular control or sensation in the trunk or lower extremities.

The announcement comes amid general excitement in the stem-cell field, thanks to Barack Obama's promise to lift funding restrictions for embryonic-stem-cell research. (See "Braving Medicine's Frontier.")

Geron's Thomas Okarma said in a statement, "This marks the beginning of what is potentially a new chapter in medical therapeutics--one that reaches beyond pills to a new level of healing: the restoration of organ and tissue function achieved by the injection of healthy replacement cells. The ultimate goal for the use of GRNOPC1 is to achieve restoration of spinal cord function by the injection of hESC-derived oligodendrocyte progenitor cells directly into the lesion site of the patient's injured spinal cord."

This video illustrates how Geron's cell therapy works in rats.