Historic trial to treat spinal injury with stem cells

Andy Coghlan

Patients with spinal cord injuries will be first humans to receive repair cells derived from embryonic stem cells.

The first ever clinical trial using stem cells derived from embryonic stem cells (ESCs) received the go-ahead today from the US Food and Drug Administration.

Geron Corporation, a company based in Menlo Park, California, hopes to mend the spines of patients paralysed from the chest down by injecting injury sites with stem cells that restore connections and repair damage.

"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," said the company's president, Tom Okarma.

"My hat is off to Geron – this is what we've all been waiting for," says Robert Lanza, chief scientist at Advanced Cell Technology, a stem cell company in Worcester, Massachusetts. "It's been over a decade since embryonic stem cells were discovered, and this sends a message that we're ready at last to start helping people."

The trial had been "on clinical hold" for years over concerns that the cells could form tumours, but the FDA is now satisfied that this risk is low enough to allow the trial to proceed.

New political climate

Ethical concerns have also dogged the trial, because obtaining the cell lines involved destruction of embryos. The previous US president, George Bush, had obstructed research using such cells for eight years to appease his conservative supporters.

However, the new president, Barack Obama, promised in his inaugural address to "restore science to its rightful place", so approval of the trial could be an early sign that he will lift all the Bush restrictions on stem-cell research, first imposed in 2001.

Hundreds of trials are already under way around the world with stem cells derived from adult or fetal tissue, but these cells are limited in the types of tissue they can turn into and repair.

The spine repair trial could open up a new era in medicine because embryonic stem cells are the only type that generate all 200 or so tissues of the body.

Revolutionary treatments

ESCs can't be used directly, because they can form cancers called teratomas. But they can be used in the lab to generate potentially inexhaustible supplies of all other types of cell that might be needed for repair.

The type to be used in the trial are neural stem cells called oligodendrocyte progenitor cells. These support other neurons in the brain and nerves by supplying growth factors and by producing the myelin sheaths that protect neurons from damage.

In previous research with these cells, Geron showed that they could improve the mobility of rats whose hind legs had been made immobile by spinal injuries. The treated rats could walk better and post-mortems showed that the injected cells had multiplied in the injury site and restored lost connections. The hope now is that the same will happen in people.

Geron says that the main objective is to prove the cells are safe, especially given the FDA's earlier misgivings over the cancer risk. But for one year after treatment, the company will also look closely for any recovery of function and movement in the lower body lost through the injury. In all, the patients will be monitored for 15 years.

If the cells appear safe, it could open the floodgates for a host of other trials using cells originally derived from ESCs. Geron itself has developed such cells for treating heart attacks, diabetes, bone damage, arthritis, liver failure and cancer.

Obama influence?

The trial is the second revolutionary stem cell therapy to receive approval within a week. On Monday, a UK company, ReNeuron, received clearance to inject stem cells into the brain, with the aim of repairing tissue damaged by strokes.

But John Sinden, chief scientist at ReNeuron, doubts whether the UK approval spurred the FDA to approve the Geron trial. "It's great news all round," he says. "It's like London buses, with two arriving together."

Sinden doubtes that Obama's arrival as president had any direct bearing on the outcome of the Geron trial, but it will undoubtedly have a benign influence on the FDA in the coming months.

"You don't expect the FDA to move as quickly as that," said Sinden. "They probably had it in mind to approve the trial for a while."

As to pressure on the FDA behind the scenes from the new administration, he said he could only guess. "The FDA will change, and the new management will be very much aligned with Obama's views on stem cells," he said.

Sinden is now hopeful that the Geron approval could signal potential willingness by the FDA to approve ReNeuron's application to conduct a planned stroke trial in the US, which has been on hold for two years.

Likewise, Lanza's company hopes to apply to the FDA this summer to begin a trial using retinal stem cells derived from ESCs to prevent a form of blindness.

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