Charities are disappointed but regulators say there is still little evidence of the drug’s benefit.
The European Medicines Agency has said no to approving a new drug for Alzheimer’s disease in the EU.
Aducanumab does not appear to be effective at treating adults with early-stage symptoms, the EMA said.
Alzheimer’s charities say they are disappointed by the decision because thousands of people are left with no treatment options.
The drug – the first new treatment for 20 years – was controversially approved in the US in June.
At the time, many scientists said there was little evidence from trials of it being of benefit despite it targeting amyloid – a protein that forms abnormal clumps in the brains of people with Alzheimer’s.
Biogen, the manufacturer of the drug, can ask for the EMA’s decision to be re-examined within the next two weeks.
It’s not known whether the company will submit a separate application for approval to the UK regulator, the MHRA.