WASHINGTON – Government health advisers sharply criticized a closely watched Alzheimer's drug on Friday, concluding there wasn't enough evidence that the experimental drug slowed the brain-destroying disease.

The panel of outside experts for the Food and Drug Administration agreed that a pivotal study in patients failed to show "strong evidence" that the drug worked. The experts warned of multiple "red flags" with the data, which did not initially show any benefit until another analysis with later results.

"Alzheimer's treatment is a huge, urgent, unmet need," said panelist Dr. Joel Perlmutter of Washington University School of Medicine. "But if we approve something with data that is not strong, we have the risk of delaying good, effective treatments."

He was one of eight panelists who voted against the drug's evidence; one voted that the drug showed "strong evidence" and two members said they were undecided. The panel also rejected the merits of a second study of the drug.

The FDA is not required to follow the group's guidance, but their negative opinion could weigh heavily on the agency's decision on whether to greenlight the drug. The FDA is expected to make a decision by March.

The Biogen drug, known as aducanumab, does not cure or reverse Alzheimer's; the claim is that it modestly slows the rate of decline. Existing drugs only temporarily ease symptoms, and no new options have emerged since 2003.

Much of the panel's commentary was a rejection of the FDA's viewpoint. Earlier in the day, the FDA's chief staff reviewer gave a glowing review of the drug, calling study data submitted by Biogen "exceptionally persuasive," "strongly positive" and "robust." But an FDA statistician noted flaws and inconsistencies in the results and potential safety issues.

"It feels like the audio and video on TV are out of sync," said panel member Dr. Caleb Alexander of Johns Hopkins University.

Friday's meeting follows months of intense skepticism surrounding the drug, co-developed with Japan's Eisai Co.

The drugmakers halted two studies of their drug last year after disappointing results. But several months later the companies reversed course, announcing that a new analysis showed the drug was effective at a higher dose and that the FDA advised that it might warrant approval.

More than 5 million people in the United States and many more worldwide have Alzheimer's.

The drug is expected to be very expensive and "could bankrupt our health care system" while giving patients false hope, the consumer group Public Citizen warned in comments ahead of the meeting.

The FDA evaluation focuses on safety and effectiveness. But advocates for approval, including the Alzheimer's Association, are pushing to make need part of the decision.

If the drug is approved, the American Academy of Neurology urged the FDA to not make it a broad authorization, which could expose many patients to a medicine that might harm rather than help, it said.