A systematic review of therapeutic strategies against amyloid‐β peptides in Alzheimer’s disease: Past, present, and future

Abstract

AbstractBackgroundLargely recognized too late, Alzheimer’s disease (AD) affects around 46 million people worldwide. The etiology of AD is still puzzling the scientific community, and its drug development and clinical trials have had high failure rate. In the recent decade, numerous studies targeting amyloid‐β peptides (Aβ) and their metabolism have been tested in patients, raising additional questions regarding AD.MethodIn order to integrate recent (from 2014) findings and analyze their clinical potential, we conducted a systematic review of investigational studies, follow‐up studies and review articles, that focus on anti‐Aβ therapies. The records were required to investigate the safety, tolerability, pharmacokinetics, efficacy, or immunogenicity of anti‐amyloid treatments in human population, excluding short and interrupted studies (<10 days), and clinical trials concerning other pathologies or comorbidities.ResultThus far, experimental therapies directed against Aβ have not been able to significantly reduce the progress of AD and memory impairment. The majority of therapeutic strategies were focused on amyloid precursor protein processing, and active or passive immunotherapy. Fewer studies evaluated drugs affecting Aβ misfolding, aggregation or clearance. Targeting β‐ and γ‐secretase have had unwanted results, but the activators of α‐secretase and immunotherapy against Aβ oligomers are giving some promise. Recent FDA approval and EU refusal of aducanumab sparked hopes and controversies, since the latest trial data confirmed amyloid plaque removal, without clear cognitive benefits.ConclusionTargeting only Aβ was not able to significantly improve the cognition of patients or modify the AD progression. The research is slowly moving toward multifunctional drugs targeting factors that precede the Aβ aggregation process, i.e., pathologic positive feedback loop linking Aβ production and other factors, such as neuronal hyperexcitability, neuroinflammation, or oxidative stress. Further development of early detection biomarkers, antibodies and additional agents that would act on both amyloid and non‐amyloid targets, could be the key to slowing down this global epidemic.FundingThis work was supported by grants BFU2017‐82494‐P and PID2020‐115823GB‐I00 funded by MCIN/AEI/ 10.13039/501100011033 and by ERDF “A way of making Europe” by the European Union; both to LJ‐D and JDN‐L. DJ held a predoctoral scholarship from Plan Propio de Investigación–ESF Programme of University of Castilla‐La Mancha.