Alzheimer disease immunotherapeutics: Then and now

Dementia is a public health priority and one of the major contributors to morbidity and global non-communicable disease burden, thus necessitating the need for significant health-care interventions. Alzheimer disease (AD) is the most common cause of dementia and may contribute to 60–70% of cases. The cause and progression of AD are not well understood but have been thought to be due at least in part to protein misfolding (proteopathy) manifest as plaque accumulation of abnormally folded β-amyloid and tau proteins in brain. There are about 8 million new cases per year. The total number of people with dementia is projected to almost double every 20 years, to 66 million in 2030 and 115 million in 2050. Immunotherapy in AD aimed at β-amyloid covers 2 types of vaccination: active vaccination against Aβ42 in which patients receive injections of the antigen itself, or passive vaccination in which patients receive injections of monoclonal antibodies (mAb) against Aβ42. Three of the peptide vaccines for active immunizations, CAD106, ACC001, and Affitope, are in phase 2 clinical trials. Three of the mAbs solanezumab, gantenerumab, and crenezumab, are or were in phase 2 and 3 clinical studies. While the phase 3 trials failed, one of these may have shown a benefit at least in mild forms of AD. There is a need for a greater initiative in the development of immunotherapeutics. Several avenues have been explored and still to come.