WASHINGTON — Clinical studies on an experimental Alzheimer's disease drug have been halted after 20% of the test subjects experienced changes in liver chemistry, the Food and Drug Administration and the drug's manufacturer announced Saturday.
FDA Commissioner Dr. Frank E. Young said the tests on the drug commonly called THA were halted through "a mutual decision" of the agency and the manufacturer, Warner-Lambert Co. of Morris Plains, N.J.
"It is a temporary hold until we understand more clearly what is going on," Young said. "This is not at all uncommon in early clinical studies."
Loss of Memory
Clinical studies on THA, whose formal name is tetrahydroaminoacridine, started a month ago on 40 patients suffering from Alzheimer's, a disease that causes a progressively increasing loss of memory and intellectual function.
The tests involved a gradually increasing dose, Young said. No side effects were observed at 40 and 80 milligrams but at 120 to 160 milligrams eight of the test subjects showed an elevation in the liver enzyme transaminase, he said.
The increase in the enzyme "indicates there are some cellular abnormalities," Young said. "These changes are the earliest things you see when cells are undergoing modification."
Warner-Lambert reported the findings to the FDA, and the decision was made to halt the testing.
Marshall Molloy, a Warner-Lambert spokesman, said the company regarded the action as "the prudent thing to do."
Studies of the drug were being conducted at 17 centers across the country. Plans call for the drug eventually to be tested on about 300 patients with Alzheimer's.
In earlier tests of the drug, Alzheimer's patients showed a marked improvement in memory and other functions. Although THA is not a cure, studies showed that it could treat symptoms of the disease.