APOE and early-onset autosomal dominant Alzheimer disease: On 22 August 2024, the United Kingdom's Medicines and Healthcare products Regulatory Agency (MHRA) approved the humanized IgG1 anti‐amyloid monoclonal antibody (mAb) lecanemab for the treatment of mild cognitive impairment (MCI) and mild dementia due to Alzheimer's disease (AD) in patients who are apolipoprotein E ε4 (ApoE ε4) heterozygotes or non‐carriers.