An image of the kind of brain plaque commonly associated with Alzheimer's disease. (University of Pennsylvania School of Medicine Photo/James Eberwine)

WASHINGTON (AP) — The Centers for Medicare & Medicaid Services (CMS) says it needs more information before it will agree to pay for routine use of Amyvid, an imaging chemical that may help doctors screen for Alzheimer’s disease-related brain plaque.

Eli Lilly & Co., the company that is developing the first-of-a-kind imaging chemical, says it will forge ahead with efforts to introduce the product.

Through Medicare, CMS provides health coverage for more than 47 million seniors. Medicare is the largest payer for prescription drugs in the United States.

In decision posted online, CMS said more trials are needed to prove that the imaging agent works.

The government will pay for patients enrolled in future Amyvid studies, but not for general use.

The radioactive imaging agent works by binding to beta-amyloid plaques and causing them to show up on positron emission tomography, or PET, scans of the patient’s brain. The presence of these plaques may help indicate that a patient with cognitive problems has Alzheimer’s disease, although such a scan does not definitively show that.

Eli Lilly, which is based in Indianapolis, has said Amyvid is one tool intended to help find the cause of a patient’s cognitive decline.

The ruling is an unexpected setback for the product after European Union regulators endorsed the chemical in January.

The U.S. Food and Drug Administration approved the drug for sale in 2011.

“Lilly remains steadfast in our request for Medicare coverage of beta-amyloid imaging agents for the appropriate patient population,” said Wei-Li Shao, director of the company’s Alzheimer’s business, in a statement.

Eli Lilly and Co. paid $300 million in 2010 to acquire the drug and its developer, Avid Radiopharmaceuticals Inc.

Avid Radiopharmaceuticals CEO Daniel Skovronsky said in a statement the Medicare ruling “may stifle future innovation aimed at improving diagnosis.”

Doctors currently diagnose Alzheimer’s disease by observing patients and administering physical and mental tests. The disease is the sixth-leading cause of death in the United States and the most common form of dementia.

Alzheimer’s attacks neurons in the brain, leading to problems with memory, thinking and behavior. There is no cure for the disease, and scientists are not even sure what causes it.

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