The Food and Drug Administration has cleared Geron, a stem cell company based in Menlo Park, CA, to move forward with clinical tests of its experimental cell therapy for spinal cord injury, which is derived from embryonic stem cells. The company, which has been working on cell based therapies for the last decade, first won permission to begin clinical testing in January of 2009. But the trials were put on hold last August due to new safety concerns from animal tests. The clinical trial marks the first human tests of a therapy derived from embryonic stem cells.

The cell therapy, called 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. The new cells are then injected into the site of the injury, coating exposed nerves and restoring communication to the nervous system.

As I noted in a previous post:

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.

According to a statement from Geron:

The clinical hold was placed following results from a single preclinical animal study in which Geron observed a higher frequency of small cysts within the injury site in the spinal cord of animals injected with GRNOPC1 than had previously been noted in numerous foregoing studies. In response to those results, Geron developed new markers and assays as additional release specifications for GRNOPC1. The company completed an additional confirmatory preclinical animal study to test the new markers and assays, and subsequently submitted a request to the FDA for the clinical hold to be lifted.

Advanced Cell Technology, a stem cell company based in Marlborough, MA, hopes to follow Geron. The company announced this week that it has submitted new materials to the FDA in regards to its application, first filed in November, to begin clinical trials of a cell therapy for patients with Stargardt’s Macular Dystrophy, an inherited eye disease.