Advances in Extracellular Vesicle-Based Innovative Drugs Targeting Alzheimer's Disease.

The scarcity of effective therapies for Alzheimer's disease (AD) underscores the urgent need for innovative strategies. This review focuses on the targeted delivery of engineered small extracellular vesicles (sEVs, 30-150 nm). By capitalizing on their intrinsic properties as natural nanocarriers-including low immunogenicity and excellent biocompatibility-these EVs can be engineered to co-deliver therapeutic cargoes such as specific miRNAs, neurotrophic factors (e.g., BDNF), and nucleic acid modalities (e.g., siRNA/ASO targeting BACE1). While a single construct simultaneously delivering all these agents with proven in vivo synergy remains a conceptual framework rather than a validated reality, independent studies have demonstrated that EV-mediated delivery of each cargo type exerts beneficial effects on AD pathology, including Aβ clearance, Tau pathology alleviation, and neuroinflammation suppression. The intranasal administration offers a significant brain-targeting advantage by enabling direct nose-to-brain delivery, bypassing the blood-brain barrier and minimizing peripheral biodistribution. Recently, a phase I/II trial (Ruijin Hospital) demonstrated that intranasal MSC-EVs are safe and produce durable cognitive improvements (ADAS-Cog ↓ 2.33 points at week 12, sustained to - 3.98 points at week 36) in the medium-dose cohort, exceeding the minimal clinically important difference (MCID) of ≥ 2 points for AD. Based on these demonstrated clinical and preclinical evidence, we propose that rationally engineered EVs, following rigorous systematic pharmacology and safety assessments, hold transformative potential to pioneer a safe, efficacious, and non-invasive breakthrough therapy for AD, while acknowledging that critical challenges in GMP manufacturing, biodistribution, and regulatory approval remain to be resolved.