After Biogen’s price cut, advocacy groups for Alzheimer’s patients urged C.M.S. to lower the premium increase. On Monday, the secretary for health and human services, Xavier Becerra, said that he was instructing C.M.S. to re-examine the premium hike “given the dramatic price change of the Alzheimer’s drug, Aduhelm.”

Aduhelm was approved by the Food and Drug Administration in June in a decision vigorously criticized by many doctors and Alzheimer’s experts because clinical trial results showed it had significant safety risks and unclear benefit to patients.

Congress is investigating whether the F.D.A. worked too closely with Biogen and why Aduhelm was approved despite strong objections from some senior F.D.A. officials and the agency’s independent advisory committee.

So far, only a small number of patients — a fraction of the number Biogen and industry analysts had initially expected — have used Aduhelm, a monoclonal antibody administered as a monthly infusion. Many large American health care systems have declined to offer the drug, citing questions about its benefits and risks.

Medicare officials are supposed to determine coverage based on whether a drug is a “reasonable and necessary” treatment, a phrase that usually “means adequate evidence of improved health outcomes,” said Dr. Sean Tunis, a former official with C.M.S. who is now a senior fellow at the Center for the Evaluation of Value and Risk in Health at Tufts Medical Center.

Medicare’s decision on Aduhelm will also establish standards for evaluating several similar Alzheimer’s drugs in the pipeline.

The F.D.A. itself acknowledged in its approval of Aduhelm that there was insufficient evidence it would help patients. Instead, it greenlighted the medication — the first new treatment for Alzheimer’s in 18 years — under a program called “accelerated approval,” which allows authorization of unproven drugs for serious diseases with few treatment options if the drug affects a biological mechanism in a way considered “reasonably likely to predict clinical benefit.”

The F.D.A. said it based accelerated approval on Aduhelm’s reduction of a protein, called amyloid, that clumps into plaques in the brains of people with Alzheimer’s. But many Alzheimer’s specialists say that extensive research has shown little evidence that reducing amyloid slows cognitive decline. The F.D.A. also required Biogen to conduct another clinical trial to determine if the drug provided any evidence of benefit. In the years it will take for that trial to be completed, Aduhelm will be available to patients.

This content was originally published here.