CRISPR-based correction of apolipoprotein E4 in Alzheimer's disease: Therapeutic strategies and macromolecular delivery innovations.

Alzheimer's disease (AD) is the leading cause of dementia worldwide, with substantial unmet clinical needs. The apolipoprotein E4 (APOE4) allele is the strongest genetic risk factor for late onset AD, with each copy increasing risk approximately two- to three-fold, and homozygous carriers facing up to a 10- to 15-fold higher risk compared to APOE3 carriers. APOE4 contributes to diverse pathogenic mechanisms including lipid dysregulation, neuroinflammation, synaptic dysfunction, and vascular compromise. The precise, allele-specific correction of APOE4 therefore holds transformative therapeutic potential. CRISPR-based genome editing technologies, including nuclease disruption, base editing, and prime editing, offer unprecedented opportunities to directly modify APOE4 at its genomic source. Here, we review mechanistic underpinnings of APOE4 pathology, summarize current gene editing platforms for APOE4 correction, evaluate relevant in vitro and in vivo model systems, and assess delivery strategies with an emphasis on nanoparticle and exosome based approaches. We highlight recent breakthroughs in exosome mediated APOE4 editing while addressing ongoing technical hurdles in allele specificity and translational barriers such as Cas nuclease immunogenicity, limited delivery efficiency across the blood brain barrier (BBB), and concerns over long term genomic safety. This review concludes that overcoming BBB constraints remains the most significant challenge for clinical translation, and that innovations in exosome and nanoparticle based delivery platforms represent the most promising strategies for advancing CRISPR therapeutics for AD.