The U.S. government health plan for people age 65 and over on Thursday issued its final coverage policy for Biogen Inc's Alzheimer's drug, Aduhelm, saying that it would limit it to patients in clinical trials.

For drugs similar to Aduhelm, the Centers for Medicare and Medicaid Services said it would allow coverage if the medication is approved after a standard review by the Food and Drug Administration.

In January, Medicare said it had significant doubts about the potential benefits of Aduhelm and proposed restricting use to clinical trials for it and similar experimental treatments designed to remove amyloid plaques from the brains of people with early Alzheimer's.

Eli Lilly and Co, Roche Holding AG and Eisai Co Ltd each have plaque-clearing drugs in late-stage development.

The FDA had approved Aduhelm under an accelerated approval pathway and viewed the reduction of amyloid plaque in the brain as an indication that the drug likely would provide benefit.

The Medicare agency said it would limit coverage only to patients in clinical trials for any of the other drugs if they were approved in this manner. For drugs approved by the traditional FDA process that showed clear patient benefit, the agency said there would not be any subsequent clinical trial requirements.