The researchers traced the problem to overactivity of the copper-containing enzyme produced by the defective gene. This overactivity, in turn, leads to the death of nerve cells in the brain and spinal cord that control muscle movement, Dr. Dale E. Bredesen of the cancer foundation and his colleagues report today in the journal Science. Researchers are testing the drugs in mice bearing the defective gene and are gearing up to test them in humans if the mouse studies are successful. The disorder, known clinically as amyotrophic lateral sclerosis, or ALS, strikes 30,000 people each year in the United States and there are few effective treatments. The ALS-triggered nerve cell death produces muscle weakness and paralysis.
Most ALS victims die within two years after the disorder's onset but some live much longer.
ALS occurs in two forms. About three years ago, researchers discovered that the familial form of the disease is caused by a mutation in the gene that is the blueprint for a protein called superoxide dismutase, or SOD1. The same gene that causes the familial form is now known to be responsible for at least a quarter of the sporadic cases. SOD1 is an enzyme that clears certain types of toxic wastes, called superoxides, from the body. Two years of intensive research in several laboratories showed that this is not the case.