AC Immune's ACI-7104 Alpha-Synuclein Peptide Vaccine Meets Week-100 Safety and Immunogenicity Endpoints in Part 1 of Phase 2 VacSYn Parkinson's Trial
AC Immune reported on September 23, 2026 that Part 1 of VacSYn, a randomized, double-blind, placebo-controlled Phase 2 trial in early Parkinson's disease, met all of its primary safety, tolerability, and immunogenicity endpoints through week 100. Thirty-four patients were randomized 3:1 to ACI-7104 or placebo; the company said 100% of patients developed antibodies against the PD01 antigen after three immunizations, antibodies reached the cerebrospinal fluid in all patients, and the vaccine was generally safe and well tolerated. ACI-7104.056 uses an eight-amino-acid peptide that mimics a C-terminal alpha-synuclein epitope, conjugated to keyhole limpet hemocyanin, according to Alzforum. AC Immune reported a CSF total alpha-synuclein signal consistent with target engagement but no clinical efficacy result, and plans FDA meetings in early 2027 before an expanded Phase 2.