On June 7, 2021, the US Food and Drug Administration (FDA) approved aducanumab (Aduhelm, Biogen) for treatment of patients with Alzheimer disease.1 The FDA’s decision is shocking for many reasons, including that 10 of 11 committee members of the FDA’s own Peripheral and Central Nervous System Drugs Advisory Committee recommended that the agency not approve aducanumab (1 member was “uncertain”).2 The intended purpose of the drug, which is administered as an intravenous infusion, is to remove depositions of the amyloid protein from the brains of patients with Alzheimer disease. However, there is no definitive evidence that amyloid deposits are the cause of, rather than simply an association or even a by-product of, the underlying Alzheimer disease process.3,4 In fact, multiple previous drugs directed at amyloid deposits have failed to produce appreciable clinical benefit over time.4 Moreover, the committee was presented with mixed data suggesting that treatment with aducanumab improved the course of the disease, although treatment was actually accompanied by central nervous system adverse effects in some patients. Biogen reported that among patients given the subsequently approved dose of aducanumab in the 2 trials, 112 (10.2%) had treatment discontinued because of adverse events (https://investors.biogen.com/static-files/8e58afa4-ba37-4250-9a78-2ecfb63b1dcb). The FDA approved the drug for use in all patients with Alzheimer disease despite that Biogen only studied patients with early disease in 2 trials, which were stopped early for futility. Subsequently, the FDA worked with Biogen on post hoc analyses of the trial data. Finally, although the trials excluded patients who were taking anticoagulant drugs, the FDA approval did not exclude patients who were taking these medications, which are commonly prescribed for older adults.