Safety and Tolerability of Active Immunotherapy Targeting α-Synuclein with PD03A in Patients with Early Parkinson's Disease: A Randomized, Placebo-Controlled, Phase 1 Study

Background: Immunotherapies targeting alpha-synuclein aim to limit its extracellular spread in the brain and prevent progression of pathology in Parkinson's disease (PD). PD03A is a specific active immunotherapy (SAIT) involving immunization with a short peptide formulation. Objective: This phase 1 study characterized the safety and tolerability of PD03A in patients with early PD. A key secondary objective was to evaluate immunological activity following immunization. Methods: This was a phase 1 study of two different doses of PD03A versus placebo in PD patients. Patients were randomized (1:1:1) to receive four priming plus one booster vaccination of PD03A 15 mu g, PD03A 75 mu g or placebo and were followed for 52 weeks. Results: Overall, 36 patients were randomized, of which 35 received five immunizations and completed the study. All patients experienced at least one adverse event. Transient local injection site reactions affected all but two patients; otherwise most AEs were considered unrelated to study treatment. A substantial IgG antibody response against PD03 was observed with a maximum titer achieved at Week-12. Differences in titers between both active groups versus placebo were statistically significant from the second immunization at Week-8 until Week-52. Conclusion: The safety profile and positive antibody response of PD03A supports the further development of active immunotherapeutic approaches for the treatment of PD.