AC Immune (ACIU) Study result summary

Study design and objectives

• The VacSYn Phase II trial was a randomized, double-blind, placebo-controlled study in early-stage Parkinson's disease, enrolling 34 patients (25 active, 9 placebo), with 18 months of treatment and a 6-month safety follow-up.

• Primary endpoints were safety, tolerability, and immunogenicity, with exploratory biomarker and clinical outcome assessments.

• The study used an optimized formulation with CRM197 as a carrier protein to enhance immunogenicity.

• Fast Track designation was granted, supporting regulatory engagement and future FDA discussions planned for early 2027.

• Part 2 will expand to approximately 250 patients, focusing on clinical activity, digital motor function, and advanced MRI biomarkers to support Phase 3 entry.

Safety and tolerability results

• ACI-7104.056 was generally safe and well-tolerated, with most adverse events being mild and transient, mainly injection site reactions, headache, and fatigue.

• Six serious adverse events (including two deaths) were reported but considered unrelated or unlikely related to the study drug.

• No significant MRI, laboratory, or ECG abnormalities were observed.

• The Data Safety Monitoring Board recommended continuation without modification.

Immunogenicity and antibody response

• 100% of treated patients developed significant antibody responses after three immunizations, with robust titers in both serum and CSF.

• Antibody responses were at least two-fold higher than previous formulations and showed high specificity for aggregated alpha-synuclein, binding to Lewy bodies in post-mortem PD brains.

• Robust antibody penetration into CSF was observed in all treated subjects, with titers increasing after each dose.