Switzerland-based AC Immune SA's (Nasdaq: ACIU) experimental alpha-synuclein vaccine ACI-7104 is expanding into US clinical development after the US FDA cleared its IND, as the company approaches a key Phase II readout that could provide an early test of whether active immunization can slow Parkinson's disease (PD) progression. The neurodegenerative disease specialist also announced receipt of US FDA Fast Track Designation for ACI-7104, an anti-alpha-synuclein (α-syn) active immunotherapy, for early-stage PD.
ACI-7104 is designed to stimulate the patient's immune system to produce antibodies that preferentially recognize aggregated, oligomeric forms of α-syn — the pathological species associated with neuronal toxicity and spread of PD pathology — rather than the physiological protein.
The Fast Track Designation was supported by interim Phase II data from the VacSYn trial (NCT06015841), an adaptive, placebo-controlled, biomarker-based study in patients with early-stage PD. At the week-76 interim readout, reported in December 2025, ACI-7104 achieved a 100% immunogenicity responder rate, with serum anti-α-syn antibody titers more than 500-fold higher than placebo two weeks after the sixth immunization. Cerebrospinal fluid antibodies were detected at approximately 0.1% of serum levels, confirming central nervous system penetration. Biomarker assessments — including cerebrospinal fluid α-syn, neurofilament light chain, glial fibrillary acidic protein, and dopamine transporter imaging — showed stabilization in the active arm relative to placebo. On the Movement Disorder Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS) Part III, the ACI-7104 group showed no meaningful progression from baseline at week 74, while the placebo arm showed an increase consistent with expected disease course. No clinically relevant safety issues were reported. The company has not disclosed formal p-values from this interim readout, characterizing the findings as exploratory signals ahead of the full dataset.
The IND clearance opens US enrolment in VacSYn, expanding the trial's geographic reach and patient access. AC Immune has also received a USD 4 million research grant from the Vijay and Marie Goradia Charitable Foundation to support a two-year extension of Part 1 of the trial, enabling longer-term safety and efficacy assessment.