The US Food and Drug Administration has cleared the way for the first trial to see if human embryonic stem cells can treat people safely, a company involved in the controversial research said.

Geron Corp, a California biotechnology company, said it plans a clinical trial to try to use the stem cells to regrow nerve tissue in patients with crushed, but not severed, spinal cords.

The issue of human embryonic stem cell research has been a political touchstone, with anti-abortion forces backed by former president George W Bush arguing the technique involves the destruction of human embryos. Advocates say it could transform medicine.

"For us, it marks the dawn of a new era in medical therapeutics. This approach is one that reaches beyond pills and scalpels to achieve a new level of healing," Geron chief executive Dr Thomas Okarma said in a telephone briefing.

Geron will recruit eight to 10 recently injured patients and inject them with small numbers of human embryonic stem cells manipulated to become the oligodendrocyte cells that insulate nerves, and that produce compounds to stimulate the growth of nerve cells.

Okarma said there was no political significance to the announcement coming the same week as President Barack Obama took office. Obama has been widely expected to lift restrictions on federal funding and support of human embryonic stem cell research.

An FDA spokeswoman said: "Before FDA allowed the study to proceed, Geron worked with FDA to address important scientific questions."

Okarma said the treatment should eventually become cheap and easy to mass produce because the cells can be grown in vats. He believes the cells may be useful for other diseases such as multiple sclerosis, in which nerve cells are stripped of their insulating sheaths, and perhaps strokes.

Financial analysts celebrated. Stephen Brozak and Daniel Mallin of WBB Securities LLC said it could be "as important to drug therapy as the discovery of ... penicillin."

Dr Robert Lanza of the rival Massachusetts-based Advanced Cell Technology, which is also seeking to create therapies using human embryonic stem cells, called the decision a "huge advance for the entire field". This sends a message that we're ready at last to start helping people," he said.

Stem cells are the body's master cells, giving rise to all the tissues, organs and blood. Embryonic stem cells are considered the most powerful kinds of stem cells, as they have the potential to give rise to any type of tissue.

Researchers are also trying to find ways to use so-called adult stem cells, taken from bone marrow and elsewhere in the body, and have learned how to transform ordinary skin cells into stem-like cells. But scientists argue that no one knows which route will work so all avenues must be pursued.

The Phase I trial will be designed to show that patients do not develop tumors, or damage to their nervous systems. But Okarma believes it will also indicate whether the stem cells might repair the damaged spinal cords. - Reuters