The role of genetic polymorphisms on drug response in Alzheimer’s disease: a systematic review

Alzheimer’s disease (AD) is the most common neurodegenerative disorder, affecting over 32 million people globally. The variability in treatment response to AD medications is influenced by genetic factors, sex, comorbidities, and medication history. Pharmacogenomics, the study of how an individual’s genetic makeup influences drug response, offers a promising approach to understanding these differences. This systematic review investigated the role of genetic polymorphisms in affecting treatment outcomes in AD. Following PRISMA guidelines, we systematically searched PubMed, Scopus, Cochrane, and PharmGKB databases for studies on AD, pharmacogenomics, and treatment response. Ten researchers independently screened the articles, with two independent reviewers resolving conflicts. A total of 1126 records were identified, and after removing duplicates and screening, 58 studies met inclusion criteria. APOE emerged as the most consistently studied gene, with ε2 and ε3 alleles generally associated with better responses to acetylcholinesterase inhibitors (AChEIs) and NMDA receptor antagonists, while ε4 carriage predicted poorer outcomes. The CYP2D610 allele, common in East Asian populations, was linked to enhanced donepezil response due to slower drug metabolism. Other genes, including ABCA1, A2M, CHRNA7, CHRFAM7A, and CHAT, showed potential associations with treatment response, particularly with AChEIs, though results varied across populations and study designs. Polymorphisms in inflammatory, metabolic, and vascular genes such as IL6, IDE, and ACE were also associated with cognitive outcomes, but findings were largely exploratory. In conclusion, APOE and CYP2D6 remain the most promising pharmacogenetic markers in AD, particularly for guiding donepezil therapy. However, evidence remains inconsistent due to varying study designs, populations, and clinical metrics. Additional genes show potential but require further validation. Larger, multiethnic studies with standardized treatment protocols and outcomes are needed to establish the clinical utility of pharmacogenomics in AD therapy.