The two large Aducanumab trials began in 2015 but were cut short in March 2019. Although the EMERGE trial was said to be ‘trending positive’ in terms of potential outcomes, early results indicated the ENGAGE study was not going to be successful. In order to progress, Biogen had specified that both trials needed to be heading in the right direction. The results meant that both trials were terminated.  

However, further analysis using data from more participants changed Biogen’s initial conclusions. The EMERGE trial data showed a positive effect in people given Aducanumab compared to placebo. The ENGAGE trial however only demonstrated a clinical benefit in a subgroup of people on a higher dose of Aducanumab – only specifically in relation to memory and thinking skills. As a result, Biogen restarted enrolment of participants back into the clinical trials, which are now due to finish in 2022.

Both trials showed a reduction in the levels of amyloid beta in the brain of those treated.

The reanalysis of EMERGE and ENGAGE suggested some reduction in cognitive decline in people taking the higher dose of Aducanumab.   

Are there any known side effects from Aducanumab?

From the clinical trials, the main side effect of Aducanumab treatment reported was amyloid-related imaging abnormalities (ARIA). These are thought to be micro-bleeds or swelling in the brain and have been reported in other anti-amyloid trials, particularly following high-dose treatment.

Biogen reported individuals with ARIA showed mild to moderate symptoms, with some displaying dizziness, headaches and nausea. These effects mean it will be important to continually monitor patients on undergoing Aducanumab treatment. 

How has the research progressed for Aducanumab?

October 2019

Biogen announced they would be submitting an application to the FDA to license Aducanumab.

November 2020

The FDA brought together and publicly broadcast an independent advisory committee meeting to discuss the evidence. The advisory committee voted against the approval of Aducanumab as a treatment for people with early Alzheimer’s disease. The committee felt there was insufficient evidence to show it is effective. 

June 2021

The FDA reached their final decision and approved the drug for use as a treatment for people living with Alzheimer’s disease at any stage. This decision was largely made on the drug's ability to reduce amyloid in the brain. However, it is still unclear whether this action will provide a clinical benefit.

The FDA used the ‘Accelerated Approval pathway’ for this decision. This pathway enables earlier access to treatments which could benefit people living with serious diseases like Alzheimer’s disease. The FDA uses the pathway where there are very few other treatments available and where a new treatment is expected to have a beneficial effect.

The FDA has also requested a further clinical trial after this approval to ensure Aducanumab really is beneficial for people living with Alzheimer's disease. The approval means Aducanumab is available to people with Alzheimer’s disease in the United States.

December 2021

The EMA announced their decision on Aducanumab and recommended the refusal of the application to license the drug for use as a treatment for Alzheimer’s disease in Europe. They concluded that there was currently insufficient evidence that Aducanumab was safe, effective and had clinical benefit for people living with Alzheimer’s disease.

The EMA noted some concerns around the safety of the drug in their decision and took the opinion that the benefits of Aducanumab did not outweigh the risks. 

The EMA’s recommendation will now be passed to the European Commission, who will formalise the decision.