Current status and challenges in targeting circulating amyloid-β carriers for Alzheimer's disease therapy

Amyloid-β (Aβ) accumulation in the brain is a defining pathological feature of Alzheimer's disease (AD). Cerebral Aβ burden is regulated not only by central production and degradation but also by its transport and clearance in the peripheral circulation. Blood-borne Aβ carriers provide a potential peripheral route for reducing brain Aβ levels by strengthening the brain-to-blood concentration gradient, representing a therapeutic strategy that does not require direct penetration of the blood-brain barrier. This review summarizes advances in blood-borne Aβ carriers and discusses their potential therapeutic applications in AD. Key carriers include human serum albumin (HSA), transthyretin (TTR), α₂-macroglobulin (α₂M), soluble low-density lipoprotein receptor-related protein 1 (sLRP1), apolipoproteins, red blood cells (RBC), monocytes and platelets, all of which participate in Aβ binding, transport from the brain to peripheral organs, and subsequent clearance. Structural abnormalities or functional dysregulation of these carriers may impair peripheral Aβ metabolism and promote cerebral Aβ deposition. Because blood-based therapeutic strategies are clinically feasible, may improve patient compliance, and do not require direct blood-brain barrier penetration, targeting circulating Aβ carriers has attracted increasing attention as a potential therapeutic approach for AD. This review further summarizes the classification and functional mechanisms of major blood-borne Aβ carriers, analyzes related intervention strategies and current limitations, and highlights future directions, including multi-target combination therapy and precision medicine. These discussions may provide a theoretical basis for developing AD treatments that target blood-borne Aβ transport and clearance.