α-Synuclein Immunotherapies Show Early Safety and Engagement in Parkinson's Disease, but Long-Term Clinical Benefits Unproven

Parkinson's disease (PD) is a devastating neurodegenerative disorder lacking a cure. A central pathological event in PD is the abnormal aggregation of α-synuclein (α-syn) in dopaminergic neurons, forming Lewy bodies. Current treatments primarily manage symptoms, failing to halt or reverse disease progression. Immunotherapeutic strategies, both passive and active, aim to address this gap by inhibiting α-syn aggregation, propagation, and toxicity, while promoting its clearance via immune mechanisms, offering a disease-modifying approach.

This review synthesized findings from in silico, in vitro, and in vivo models, alongside early phase clinical trials, evaluating immunotherapies targeting α-synuclein. Researchers analyzed data on monoclonal antibodies, peptide-based vaccines, protein-based vaccines, and structure-guided immunogens. The analysis focused on how epitope selection and antibody formats influenced efficacy, safety, and target engagement. Outcomes integrated behavioral, neuropathological, proteomic, and structural data, alongside biomarker development for α-syn species in cerebrospinal fluid and peripheral compartments.

Clinical evidence indicates that several α-synuclein immunotherapy candidates induce sustained anti-α-syn antibody responses with acceptable safety profiles. Signs of pharmacodynamic engagement were observed, including reductions in free or oligomeric α-syn. Advances in structural biology and proteomics are supporting more rational epitope selection and improved immunogen design, reinforcing the potential of this approach. However, a significant gap persists between preclinical success and achieving disease modification in humans. > Consistent long-term clinical benefits remain unproven, despite promising early safety and target engagement data. This highlights the complexity of translating preclinical findings into tangible patient outcomes for neurodegenerative diseases.