Glatiramer Acetate Therapy Induces DNA Methylation Changes in Immune Cells of Multiple Sclerosis Patients: A Pilot Study

Glatiramer acetate (GA) is a first-line disease-modifying therapy for multiple sclerosis (MS) with well-established moderate efficacy and high safety, yet its mechanisms of action remain incompletely understood. DNA methylation plays a significant role in MS development and is modulated by various environmental factors, including therapeutic drugs. In this pilot study, we report the first prospective analysis of genome-wide DNA methylation changes in peripheral blood mononuclear cells (PBMCs) from four female relapsing-remitting MS patients before GA initiation and after approximately four and eight months of therapy. We identified 365 loci that are characterized by differential methylation, distinguishing post-treatment time points from baseline, with significant enrichment in CpG islands, shores, and promoter regions. Two distinct temporal patterns emerged: (1) non-monotonic DNA methylation changes peaking at four months and associated with response to foreign antigenic stimuli, and monotonic changes progressively increasing by eight months and related to mTOR-associated pathways relevant to chronic inflammation and neurodegeneration. Integration of DNA methylation and transcriptomic data revealed significant methylation-expression correlations for eight genes, including HLA-<i>DMA</i>, <i>PDE4A</i>, and <i>SMOX</i>-genes with established roles in MS-associated antigen presentation, immunoregulation, and neuroinflammation. Cell composition of PBMCs remained stable throughout treatment. In general, GA therapy for MS appears to induce dynamic, locus-specific DNA methylation changes in PBMCs, with distinct temporal patterns suggesting a biphasic response of the immune system. However, given that none of the individual DMPs reached genome-wide significance, the results presented in this pilot study strongly require validation in larger independent cohorts. Nevertheless, we believe that our findings provide insights into the immunomodulatory effects of GA and lay the foundation for future hypothesis-driven studies to develop epigenetic biomarkers for therapeutic monitoring and generic GA product assessment.