EXPLAINER: How will insurers cover a new Alzheimer's drug?

Federal regulators have approved the first new drug for Alzheimer’s disease in nearly 20 years, leaving patients waiting to see how insurers will handle the pricey new treatment.

Health care experts expect broad coverage of the drug, which was approved Monday. But what that means for patients will vary widely depending on their insurance plan. In some cases, that could mean coming up with several thousand dollars to pay for what the insurer didn’t cover.

And there's no guarantee that every case will be covered.

Here’s what you need to know:

WHAT WAS APPROVED?

The Food and Drug Administration said it granted approval to a drug from Biogen based on clinical research results that seemed “reasonably likely” to benefit Alzheimer’s patients.

It’s the only drug that U.S. regulators have said can likely treat the underlying disease, rather than just manage symptoms. The new drug, which Biogen developed with Japan’s Eisai Co., did not reverse mental decline. It slowed it in one study.

The FDA’s decision came despite the conclusion of its advisory committee that there wasn’t enough evidence that the drug slowed the brain-destroying disease.

WHAT DOES IT DO?

It aims to help clear harmful clumps of a protein called beta-amyloid from the brain. The medication will be marketed as Aduhelm and is to be given as an infusion every four weeks.

WHAT WILL IT COST?

Biogen said the drug would cost approximately $56,000 for a typical year’s worth of treatment, and it said the price would not be raised for four years.

HOW WILL INSURERS COVER IT?

They will likely request some documentation first that the patient needs the drug. Many plans will require doctors to submit records and other paperwork justifying the treatment before they agree to...