Alzheimer’s Drug Is Bonanza for Biogen, Most Likely at Taxpayer Expense

In addition to the United States, Biogen has asked regulators in Australia, Brazil, Canada, the European Union, Japan and Switzerland to review the drug.

The U.S. approval is a crucial victory for a company that has been counting on Aduhelm to make up for stalled or declining revenue from its other products. Competitors last year introduced generic versions of Biogen’s multiple sclerosis drug, Tecfidera, causing the company to miss out on hundreds of millions of dollars in revenue from what had been its top-selling product.

The approval “completely transforms” Biogen, said Brian Skorney, an analyst at Robert W. Baird & Company, who is projecting that the drug will generate $7.5 billion in revenue in 2025. “This changes it from a declining revenue company to a growth company,” he said, and, in so doing, “opens up a bit of Pandora’s box” in terms of pricing and reimbursement.

While only patients with mild cognitive decline were enrolled in the clinical trials, the F.D.A. approved the drug for anyone with Alzheimer’s, a much broader group of patients than many experts were expecting.

Just how lucrative the drug will be for Biogen will depend on how many patients it can reach — and in what circumstances, and for how long, insurers are willing to pay for it.

Dr. Steve Miller, the chief clinical officer at the insurer Cigna, said on Monday that he expected his company and most of its peers would pay for the drug only for patients with mild cognitive symptoms and higher-than-normal levels of the protein amyloid in their brains.

“There’s just no data that more advanced patients will benefit,” he said.

Dr. Miller said he was disappointed that the F.D.A. had made so many patients eligible. “You’re leaving the tough decision-making about who should be covered to the individual payers,” he said.