AC Immune reports positive week-100 safety and immunogenicity data for ACI-7104 in Parkinson's trial

AC Immune SA announced on September 23, 2026 positive safety and immunogenicity results through week-100 in Part 1 of its VacSYn Phase 2 trial of ACI-7104, an active immunotherapy targeting alpha-synuclein, in patients with early-stage Parkinson's disease. The trial is randomized, double-blind, and placebo-controlled.¹

The Part 1 data reported includes results from all 34 patients randomized into the study, with 25 receiving ACI-7104 and nine receiving placebo.¹ The primary endpoints for Part 1, covering safety, tolerability and immunogenicity, were all met, and the therapy was generally safe and well tolerated, with 100% of patients developing antibodies against the immunizing antigen PD01 after three immunizations.¹ Antibody reactivity against aggregated alpha-synuclein was also observed, along with robust antibody penetration into the cerebrospinal fluid in all patients.¹

Although Part 1 was not designed to evaluate biomarkers or clinical outcomes, exploratory analyses found a signal for total alpha-synuclein in the CSF, providing preliminary evidence consistent with target engagement.¹ Correlation analyses also suggested a trend linking antibody levels with disease activity measures, though the company noted the sample size in Part 1 was limited.¹

The trial continues in Part 1's two-year extension while advancing toward Part 2, with the final design to be submitted to the FDA and meetings expected in early 2027.¹

Interim CEO Martin Zügel said the results were encouraging, noting all primary endpoints were met and a 100% response rate was observed, and that the company plans to discuss next steps with regulators before an expanded Phase 2 trial aimed at showing clinical activity ahead of a Phase 3 decision, as stated in the release.