Aducanumab

Aducanumab, or BIIB037, is a monoclonal IgG1 antibody that targets extracellular amyloid-β plaques in the brain; similar to gantenerumab, bapineuzumab and solanezumab. Aducanumab is a recombinant antibody derived from patients with slow or absent cognitive decline, and phase 1b clinical trial data have shown patients treated with aducanumab show a reduction in amyloid-β plaques. Based on Mini-Mental State Examination and Clinical Dementia Rating (CDR), patients taking aducanumab showed signs of slowing progression, however, these data are controversial. Clinical trials showed a 23% relative difference between the experimental and placebo groups as determined by CDR, however, this is equivalent to an absolute difference of 0.4/18.

Although aducanumab's approval represents the first drug treatment for Alzheimer's disease, the approval is conditional on further results. Biogen enrolled patients in phase 3 clinical trials in 2015, but increased the size of the trials from 1350 patients to 1650 patients to maintain statistical power in the face of a high standard deviation. Development of aducanumab was discontinued in March 2019 when two phase 3 clinical trials did not pass futility analysis, however, Biogen sought FDA approval in October 2019 after a reanalysis of the data.

Aducanumab was granted accelerated FDA approval on 7 June 2021. Continued approval will be based on further trials confirming a clinical benefit over currently available therapy.

Aducanumab is indicated for the treatment of Alzheimer’s disease. Treatment should be initiated in patients with mild cognitive impairment or mild dementia stage of disease, the population in which treatment was initiated in clinical trials. There are no safety or effectiveness data on initiating treatment at earlier or later stages of the disease than were studied.