Targacept (NASDAQ:TRGT) said Thursday clinical results for its investigational treatment of attention deficit hyperactivity disorder in adults missed expectations, though positive results in a separate test fed optimism that the drug may be developed as a treatment for Alzheimer's disease.

The phase II study, conducted by AstraZeneca (NYSE:AZN), was one of several early trials designed to obtain information on dosage in potential later-stage development of the drug for use in Alzheimer’s disease and ADHD.

AZD1446 was licensed by Targacept to AstraZeneca pursuant to a 2005 collaboration agreement.

In the trial, the compound did not improve core symptoms of ADHD as compared to the placebo and, based on this finding, Targacept said it does not expect AstraZeneca to progress with the drug as a treatment for the disorder.

“While we are disappointed in the results on the primary outcome measure in this ADHD trial, we are encouraged by the memory and learning findings from the CogState test battery and believe they support further study of AZD1446 as a treatment for Alzheimer’s disease,” said Targacept CEO J. Donald deBethizy, Ph.D.

A decision by AstraZeneca as to AZD1446’s future development in Alzheimer’s disease is expected in the coming months.