The FDA has removed a clinical hold on the first medical trial of an embryonic-stem-cell treatment for spinal-cord injuries.

Early-stage trial by Geron began in January 2009 but the FDA placed the trial on hold seven months later when safety concerns surfaced in an animal study. There was an increased frequency of microscopic spinal cysts within the injury site where the cells were injected.

The FDA had lifted a nearly yearlong hold that delayed authorizing tests in humans in what Geron described as the world’s first clinical trial of embryonic stem cell-based therapy in humans.

For the resumed study, Geron say a new testing methods has been developed and it can ensure the purity of the drug, which is actually a mix of different cells. Early clinical trials will focus on evaluating safety with eight to 10 patients who recently suffered severe spinal cord injuries.

The study will test the drug that contains cells called oligodendrocyte progenitor as a treatment for acute spinal cord injury by injecting it into the spine one to two weeks after the patients suffer an injury.

The living cells help restore nerve fibers and myelin that protect nerves in the central nervous system and lead to restoration of sensory function.

Embryonic stem cells, obtained by destroying human embryos, are building block cells that differentiate into more specific cells. The long-term aim of the research is to use embryonic stem cells to regenerate cells that can’t be replaced because of injury or disease.

Geron say the company is currently conducting animal tests to determine the therapy’s potential in nervous-system diseases such as Alzheimer's disease, multiple sclerosis, and Canavan disease.