FOR CAMBRIDGE-BASED Biogen, it’s been the best of times and the worst of times. 

The biotech powerhouse saw its Alzheimer’s drug Aduhelm approved in June by the Food and Drug Administration. The first new Alzheimer’s therapy in nearly 20 years, the drug looked poised to become a blockbuster treatment that would reap billions in sales for the company given the millions of people affected by the degenerative and fatal brain disease. 

But Aduhelm’s approval has been dogged by controversy. An FDA advisory committee recommended against its approval, and there has been widespread criticism from the scientific community that the approval came despite no clear evidence that the drug confers benefits to Alzheimer’s patients. Dr. Aaron Kesselheim, Harvard Medical School researcher and member of the advisory committee who resigned following the FDA action, called it “probably the worst drug approval decision in recent US history.”

Congressional committees are seeking more information on behind-the-scenes interactions between FDA officials and Biogen leading up to the agency’s approval. 

Now, the company’s top scientist, who was reported by the medical news site STAT to have held an “off-the-books” meeting with a key FDA official prior to Aduhelm’s approval, is leaving. STAT reports that Biogen announced Al Sandrock’s departure on Monday after STAT reported the news. 

The Wall Street Journal, citing a source, says the 64-year-old scientist had been “discussing retirement for some time but wanted to wait until Aduhelm’s development was completed.” STAT characterizes his departure very differently, saying he is “leaving in the midst of a federal investigation” of the Aduhelm approval. 

Sandrock has led the company’s efforts to launch several successful new drugs, but Aduhelm, priced at $56,000 per year, is proving to be more of a drain than a boon. A number of prominent hospital systems, including Mass. General Brigham, have said they won’t offer it to patients. The biggest question, though, is what the federal Medicare agency will decide about covering the drug, since it is the insurer for all Americans 65 and older – the population that Alzheimer’s is mainly affecting. 

Even though that decision is still pending, Amitabh Chandra, an economist who is director of health policy research at the Harvard Kennedy School, told CommonWealth last month that he can’t see how Medicare won’t cover a drug approved by the FDA. “So it will be paid for by taxpayers,” he said. 

And also, it seems, by older Americans on Medicare. On Friday, Medicare announced that the cost of premiums for “Part B” coverage of outpatient care will jump by $21.60 in 2022. That’s one of the biggest annual increases ever, and Medicare officials said about half of the increase is due to anticipated costs to the program from Aduhelm. The Associated Press says that will eat up a big share of the average $92-a-month cost-of-living increase recently announced for Social Security recipients. 

The rate increase seems to confirm the fears some scientists and health care advocates have expressed — that Aduhelm could significantly increase health care costs without any clear evidence that it’s doing any good for patients. 

How this will all play out for Biogen still seems unclear. STAT calls it “a company in decline,” with revenue for 2021 on track to come in 20 percent lower than projected, and layoffs being considered. Meanwhile, Biogen announced today that a European Union drug review panel has given Aduhelm a “negative trend vote,” meaning it’s unlikely to receive approval there.