AC Immune Reports Positive Safety & Immunogenicity at week-100 in Part 1 of VacSYn Phase 2 Trial of ACI-7104

* All primary endpoints of the study were met, with ACI-7104 shown to be generally safe and well tolerated * Strong immunogenicity demonstrated, with 100% response rate after three immunizations * Clear antibody penetration into the cerebrospinal fluid (CSF) and signals for target engagement * Discussions with FDA regarding future development path planned for early 2027 * AC Immune to host webcast & conference call today at 10:00am EDT / 16:00 CEST details below Lausanne, Switzerland, September 23, 2026 – AC Immune SA (NASDAQ: ACIU), a clinical-stage biopharmaceutical company developing targeted therapeutics for neurodegenerative diseases, today announced positive safety and immunogenicity results through week-100 in Part 1 of VacSYn, its randomized, double-blind, placebo-controlled Phase 2 trial of ACI-7104 in patients with early-stage Parkinson’s disease (PD). The study is being conducted in two parts with the aim for Part 1 being to show safety, tolerability and immunogenicity while Part 2 is designed to provide evidence of clinical activity as the basis for a Phase 3 decision. The Part 1 data reported today includes results from all 34 patients randomized into the study (25 patients receiving ACI-7104 and nine receiving placebo).