Based on Phase II data, Cortex Pharmaceuticals Inc. partner Shire Pharmaceuticals Group plc decided not to exercise its option to develop Cortex's CX516 to treat attention deficit hyperactivity disorder, leaving Cortex with no immediate plans to continue with the drug in that indication.

Shire, of Andover, UK, had the responsibility of running Cortex's Ampakine CX516 through Phase II work that involved 72 adults with ADHD, and had an option to continue to develop the product. However, Shire terminated the trial prior to the expiration of the option and did not recruit any more patients.

"[Shire] based this decision on the results - what it got out of the trial," said Vincent Simmon, president and CEO of Irvine, Calif.-based Cortex. "They analyzed the data and made a decision."

Cortex's stock (AMEX:COR) fell 45 cents Monday, or 27.2 percent, to close at $1.20.

Just what Shire saw is not yet known, Simmon told BioWorld Today, but most likely, the compound is finished in ADHD. Cortex has not seen full data yet, although it has a right to get from Shire what the study produced. That will take time, Simmon said, but Cortex wants "to know what went wrong and why."

"If we get a new partner [for ADHD], it will probably be with a different drug," he said. "If the results [in the Phase II] had been encouraging, Shire wouldn't have turned down [the option.]"

The Ampakine technology produces compounds designed to increase the strength of neurotransmitter signals in the brain, thus improving the brain's communication. Simmon said the compounds might have applications in several neurodegenerative diseases of the brain, such as Alzheimer's disease and mild cognitive impairment, as well as depression and anxiety, and Cortex is working in those areas.

Cortex has partnerships with NV Organon, of Oss, the Netherlands, for the treatment of schizophrenia and depression, and with Les Laboratoires Servier, of Paris, to treat neurodegenerative effects associated with aging. Also, Les Laboratoires Servier selected CX516 as its Phase II lead Ampakine compound to treat mild cognitive impairment [MCI] and Alzheimer's disease, having rights to the compound in that area mainly for Europe and Asia. Shire had held the right to first refusal to keep CX516, but with its decision made, Servier is "the happy folks on the block," Simmon said.

Cortex and Servier now are enrolling patients for an MCI study at 31 sites across the U.S. and in five countries in Europe. The study will examine CX516 in patients who meet the criteria for MCI for 28 days. Enrollment should be completed by the end of March 2003.

Looking ahead for Cortex, which would "rather have the larger and potentially valuable market of MCI and Alzheimer's," Simmon said, the MCI data next year will be important.

"And we'll be looking for partners in the areas that are not geographically held by Servier," he said. "And we'll be looking to see if there is anything in the [ADHD] data worth pursuing."