Amyloid-Beta Immunotherapies for Alzheimer's Disease: Current Progress.

Abstract

Alzheimer's Disease (AD) is a major global challenge and the most common cause of dementia worldwide. Accumulation of Amyloid-Beta (Aβ) is considered a key factor in AD pathophysiology and progression, and is linked to disruptions of neuronal integrity and the initiation of several downstream neurodegenerative cascades. Immunotherapeutic agents targeting Aβ have emerged as potential disease-modifying drug candidates, and extensive efforts have been dedicated to both active and passive modalities. Early Aβ vaccines demonstrated proof of concept; however, they were later discontinued due to several safety concerns, which, in turn, guided the refinement of epitope design and immune response modulation in the second-generation ones. On the other hand, early monoclonal antibodies have also faced challenges, such as variable efficacy and adverse events, particularly Amyloid-Related Imaging Abnormalities (ARIA), which ultimately led to their discontinuation. Nonetheless, recent regulatory advances have led to the approvals of Aduhelm® (Aducanumab), Leqembi® (Lecanemab), and Kisunla® (Donanemab), each of which has demonstrated the ability to reduce Aβ burden and slow cognitive decline. Despite these advancements, challenges persist regarding patient selection, biomarker-guided monitoring, ARIA risk reduction, long-term outcomes, and global accessibility. Notably, the clinical benefits observed to date remain modest, and it remains uncertain whether the currently approved Aβ-targeted immunotherapies achieve meaningful long-term disease modification. Collectively, the evolution of Aβ-targeted immunotherapies has provided further insights into the complexity of AD pathology and the challenges associated with future progress toward achieving effective disease modification. This paper aims to provide a comprehensive review of all Aβ-directed immunotherapies, both active and passive agents, that have advanced into clinical trials, including those currently approved, discontinued, or undergoing late-stage evaluation.