Patients and their families may see hope in the news that the Food and Drug Administration has approved a drug to slow the pace of Alzheimer’s disease. Aducanumab is the first medicine authorized to treat what might be an underlying cause of the disease: amyloid beta clumps that accumulate in the brain.

Yet the evidence from clinical trials that this drug reduces Alzheimer’s is incomplete; it may be only minimally effective, if it works at all. The FDA’s own expert panel strongly objected to the drug’s approval.

All of which makes the FDA’s announcement both perplexing and wrong. It threatens to mislead millions of Alzheimer’s patients. At the same time, because Biogen plans to price the drug at $56,000 a year for the average patient, it also stands to cost Medicare and other insurers a bundle.