The world’s first authorized test in people of a treatment derived from human embryonic stem cells has been cleared to begin by the Food and Drug Administration.
The trial will test cells developed by Geron Corporation and the University of California, drugstore Irvine in patients with new spinal cord injuries.
The F.D.A. had initially cleared the clinical trial in January, salve 2009, in what was viewed at the time as a research milestone.
But before the study could begin, the agency then put a so-called hold on the trial after cysts were discovered in some mice injected with the cells. Geron had to do another mouse study and develop better ways to check the purity of its cells.
On Friday, the company announced in a press release that the F.D.A. had lifted the hold. Geron shares rose in morning trading.
Embryonic stem cells can turn into any type of cell in the body. Scientists envision one day making replacements for injured or diseased tissues to treat a wide variety of illnesses.
Clarification: But the cells have been controversial because their creation has required the destruction of human embryos, although some scientists claim they now avoid killing the embryos.
Geron, which is based in Menlo Park, Calif., helped finance the isolation of the first human embryonic stem cells at the University of Wisconsin in the late 1990s, so it holds certain patent rights on use of the cells.
Geron turns embryonic stem cells into precursors of neural support cells called oligodendrocytes, which would be injected into the spinal cord at the site of the injury. The hope is that the injected cells will repair the insulation, known as myelin, around nerve cells, restoring the ability of some of the nerves to carry signals.
The first trial, a so-called phase 1 study, will have a small number of patients and is aimed mainly at testing the safety of the therapy. Years of further testing will be required before the therapy would be proven and ready for widespread use, assuming it works.
Some experts have worried that this particularly therapy has not been adequately proven in animals and could spur a backlash against the embryonic stem cell field should it fail in the trial or cause harm to patients.
“We really want the best trial to be done for this first trial, and this might not be it,’’ Dr. John A. Kessler, chairman of neurology and director of the stem cell institute at Northwestern University said at the time the F.D.A. first cleared the trial.
Still, Dr. Kessler’s own institution will apparently participate in the trial. Geron’s press release Friday morning quoted Dr. Richard Fessler, professor of neurological surgery at Northwestern, saying that if it worked the therapy would be “revolutionary for the field.’’