Elan Corp. and Wyeth said on Wednesday that an experimental Alzheimer’s disease treatment did not improve cognition in patients, but it did reduce plaques that form on patients’ brains.

Clinical development of the drug AN-1792 was suspended in January 2002 after reports of encephalitis in some patients.

Researchers tracked patients in the clinical study until December 2002 and presented the results at the 9th International Conference on Alzheimer’s Disease and Related Disorders.

The phase IIA clinical trial for AN-1792, a synthetic form of the plaque that builds up in the brains of people with Alzheimer’s disease, involved 372 patients with mild to moderate cases. The compound is meant to spur the body’s immune system to prevent the plaque from forming.

“These results are significant because they suggest that it may be possible to reduce plaque buildup in the brain and alter the pathologic findings of patients with Alzheimer’s disease,” Elan Chief Scientific Officer Dale Schenk said in a statement.

Wyeth and Elan are evaluating AAB-001, a new humanized monoclonal antibody, which uses a similar approach to the disease.

The study found that AN-1792 did not meet cognitive endpoints, but there were improvements shown in other measures of the disease’s effect, including memory.

The study also revealed evidence of plaque reduction in three cases of patients who died during the study. Those results are consistent with tests of this type of drug on animals.

Also, the drug led to reductions of a protein that becomes elevated in the cerebral spinal fluid in Alzheimer’s patients.