The search for an effective treatment for the most common form of dementia, Alzheimer’s disease, has been long and hard in spite of the huge unmet need of the 55 million people currently living with the condition, a number that is expected to double every 20 years.
Yet, the arrival of a potential treatment, Biogen’s Aduhelm (aducanumab), has not perhaps been welcomed with the unalloyed joy some might have thought.
In addition to a controversial approval by the Food and Drug Administration (FDA) and slow uptake among physicians and patients, the drug has been plagued by reports about side effects.
The most worrying for many is amyloid-related imaging abnormalities – oedema (ARIA-E), an accumulation of the fluid in brain first seen in clinical trials for another human monoclonal antibody tested as a treatment for Alzheimer’s, bapineuzumab.
Now, Biogen has announced that it is investigating a fatal case of ARIA-E in a 75-year-old man who was taking Aduhelm. According to the company, the cause of death, which was reported through the FDA’s Adverse Event Reporting System (FAERS), ‘remains under investigation’. It said it would ‘continue to work with the reporting physician as well as global regulators to further understand the case. Alzheimer’s disease is complex, and patients affected by this devastating disease often suffer from other serious medical conditions’.
When announcing the results of its Aduhelm trials to the FDA, Biogen said that 80% of the cases of ARIA-E reported during clinical testing resolved within four months. It added that it believed the benefits of Aduhelm outweighed the risks.
Yet, the potential case of ARIA-E has attracted a great deal of attention, far more than is usual for a single medicine-related death.
First to highlight the case was an analyst from RBC Capital Market, Brian Abrahams, who also has a medical degree. In a note to investors, Dr Abrahams cautioned against ‘overinterpreting causality’ from the FAERS data then pointed to the fact that, if the six patients reported to the database ‘likely received commercial product in the US’, it would put the real-world adverse event rate at around 3%.
The note continued: ‘It is hard to definitively assign a cause of death, though we note the patient was not particularly old (75 years of age) and did not appear to have any other contributing conditions listed.’
Should the patient’s death be linked to Aduhelm. Abrahams added, it could contribute to further hesitancy among physicians to prescribe the drug.
Professor of psychiatry and neurology at the University of Southern California Lon Schneider commented that a handful of hospitalisations was concerning, considering how few people have received Aduhelm, but that the reports were not wholly unexpected in the real world as patients in the trials were carefully selected and intensively monitored.
Biogen’s stock closed down by nearly 4% following the news.