Al Sandrock, head of R&D for Biogen, will step down at year’s end, the company said yesterday

The departure, which Biogen described as a retirement effective December 31, came unexpectedly, noted STAT, which was first to report the news. Details surrounding the decision were not immediately clear.

Priya Singhal, head of global safety and regulatory sciences, will assume Sandrock’s duties on an interim basis.

A 23-year company veteran, Sandrock became the driving force behind the development of many of Biogen’s most successful medicines, among them Tysabri and Tecfidera for multiple sclerosis and Spinraza for spinal muscular atrophy. He was also the figure most associated with the company’s quest to develop a treatment for Alzheimer’s disease. When the U.S. Food and Drug Administration approved the drug in June, Aduhelm (aducanamab) became the first new treatment for the disease in nearly two decades. 

Instead of salvaging the Cambridge, Massachusetts-based firm’s reputation for pumping out neuroscience blockbusters, however, Aduhelm has been synonymous with withering controversy. Doctors and scientists heavily criticized the clinical data, which were equivocal as to whether the drug confers any functional benefit for patients. 

Several lawmakers launched probes into the approval, and the company also faces a federal investigation into the FDA’s process for reviewing the drug. This included an ex parte meeting between Sandrock and a top agency official which seemed to raise the specter of improper influence. 

In July Sandrock and CEO Michel Vounatsos went on the offensive. The two issued an open letter saying they welcomed discussion but also decrying what they argued has been “a turn outside the boundaries of legitimate scientific deliberation.” Aduhlem, the two wrote, has been the subject of “extensive misinformation and misunderstanding.”

With sales from the rest of its portfolio largely flat or declining, Biogen was counting on Aduhelm to jumpstart revenues. The company is spending $500 million on commercializing the medicine this year

But the drug’s third-quarter sales of $300,000 fell far short of analyst expectations and may not turn around until 2022, when Medicare is slated to make a coverage decision. Meanwhile, several insurers have pushed back, and a few big medical centers have said they won’t offer the drug to patients.