Protein to be tested on motor neurone patients

GERMAN scientists have raised hopes that a protein which encourages the growth of nerve cells might eventually provide the first treatment for people with motor neurone disease.

Two American companies have started clinical trials on human patients following experiments which showed that the protein, known as a growth factor, prolonged the life of nerve cells cultured in the laboratory.

The idea that the protein, ciliary neurotrophic factor (CNTF), might help in the treatment of motor neurone disease has now received strong support since the disclosure that mice afflicted with a similar disorder improved after treatment with CNTF.

Motor neurone disease is a fatal condition in which the nerve cells connecting the brain to the muscles degenerate and die. Because nerve impulses cannot travel to the muscles, those who suffer from the disease experience progressive muscular weakness. The Cambridge physicist Stephen Hawking suffers from motor neurone disease, for which there is at present no treatment.

Writing in the scientific journal Nature, Professor Hans Thoenen and his group from the Max- Planck-Institute in Martinsread, describe how they treated mice suffering from a mutation which causes rapid motor neurone degeneration - akin to the human disease. The researchers took cells from the bone marrow of mice and genetically engineered them to produce large quantities of CNTF. The genetically engineered cells were then injected into the affected mice.

Animals treated with CNTF in this way survived whereas most of their untreated siblings died and the treated mice retained considerable strength in their limbs. Furthermore, the scientists found that the treated mice had considerably more nerves remaining than the untreated group. The researchers concluded that the growth factor worked by prolonging the life of nerve cells.

'This is potentially one of the most important discoveries in the field of treatment for motor neurone disease, but whether the dramatic results in mice translate into humans is still an open question,' Ron Oppenheim, Professor of Neuroscience at Wake Forest University in North Carolina, said.

Mice were treated only when they were old enough to show some paralysis and scientists were encouraged that mice benefited when CNTF was given after the disease had already taken hold and the mice had suffered a significant amount of nerve loss. Similarly, the disease in people is recognised only comparatively late on, after many nerves have already wasted away.

In human trials the growth factor itself, rather than cells producing it, is injected under the skin of patients with a form of motor neurone disease called amyotrophic lateral sclerosis.

Alan Pestronk, Professor of Neurology at Washington University in St Louis, Missouri, is co-ordinating the first trial of CNTF in which it is being given to 48 patients. 'This is the most promising avenue to pursue. It's logical, and works in animal models,' he said. 'In the present trial we are finding an optimal dose. If the drug is safe there will be a much larger trial afterwards, using 10 to 20 times more patients.'

Results from the first trial are expected in December.