AC Immune reported interim data from its Phase II Vacsyn program showing coherent biomarker changes — reductions in aggregated α‑synuclein measures and supportive NfL and GFAP signals — that the company says indicate potential disease modification in early Parkinson’s disease. The firm announced plans to discuss the dataset with regulators to explore accelerated development pathways. The dossier mixes fluid biomarkers and imaging endpoints and is being positioned as the first time an active anti‑α‑synuclein vaccine has produced a consistent biomarker signal in humans. AC Immune will need to link biomarker shifts to clinical benefit in larger, longer trials; investors and partners will watch regulator feedback and next trial design closely. For readers: α‑synuclein is the protein central to Parkinson’s pathology; reductions in its soluble forms are interpreted as target engagement.