FDA Grants Fast Track Designation to AC Immune’s ACI-7104 for Parkinson Disease

AC Immune’s anti-alpha-synuclein (α-syn) active immunotherapy ACI-7104 has received FDA Fast Track designation and Investigational New Drug (IND) clearance for early-stage Parkinson’s disease, clearing the way for expansion of the ongoing Phase 2 VacSYn trial into the United States. Interim data showed a 100% immunogenicity responder rate with a favorable safety profile and early signals of biological and clinical activity, but clinical efficacy remains unproven pending the full week-100 and extended follow-up results.

FDA Advances U.S. Development of ACI-7104

The FDA decisions mark a regulatory milestone for ACI-7104, a wholly owned active immunotherapy being evaluated in the adaptive, placebo-controlled, biomarker-based Phase 2 VacSYn study (NCT06015841) in patients with early Parkinson’s disease.

Fast Track designation provides a pathway for closer interaction with the FDA during development and regulatory review of therapies addressing serious conditions with unmet medical needs. IND clearance allows the VacSYn program to expand to clinical sites in the United States.

The decisions follow interim Part 1 findings that showed ACI-7104 was generally safe and well tolerated. The company reported no clinically relevant safety issues and a 100% responder rate for the immunogenicity endpoint. These findings demonstrate that the vaccine can generate the intended immune response, but they do not establish that treatment slows or prevents Parkinson’s disease progression.

 ACI-7104 Targets Pathological α-Synuclein

Parkinson’s disease is associated with the accumulation and spread of abnormal α-synuclein aggregates in the nervous system. These pathological protein species are linked to cellular stress and neuronal degeneration, making α-synuclein an important target for potential disease-modifying therapies.

ACI-7104 is an optimized formulation of AC Immune’s earlier anti-α-syn active immunotherapy. It induces antibodies that preferentially recognize aggregated, pathological forms of α-synuclein. The resulting immune response is intended to target pathological α-synuclein and interfere with processes associated with its spread and downstream neurodegeneration.

As an active immunotherapy, ACI-7104 stimulates the patient’s immune system to produce target-specific antibodies rather than supplying therapeutic antibodies directly.

Phase 2 VacSYn Trial Continues

VacSYn is evaluating ACI-7104 in early Parkinson’s disease using biomarker and clinical assessments. Part 1 enrolled more than 30 patients who were randomized to ACI-7104 or placebo at a 3:1 ratio. Earlier interim analyses showed robust anti-α-syn antibody responses, with repeated immunization further increasing antibody levels.

At 76 weeks, AC Immune reported changes in biomarkers and clinical measures that it considered signals of a potential treatment effect. Earlier analyses also showed that the ACI-7104 group did not demonstrate meaningful progression in mean MDS-UPDRS Part III scores at week 74, while the placebo group showed an increase. However, these interim findings remain exploratory and require confirmation in the complete dataset.

AC Immune also received a $4 million research grant from The Vijay and Marie Goradia Charitable Foundation to support an extension of Part 1, enabling longer-term assessment of safety and potential efficacy.

Week-100 Data Will Be the Next Key Catalyst

The company expects to report the full Part 1 results in the second half of 2026. The dataset will provide a more complete assessment of the durability of the immune response, biomarker changes, clinical measures and longer-term safety.

The results will also inform discussions with regulators on the future clinical development plan for ACI-7104. AC Immune has indicated that the VacSYn data could support further development toward registration, but whether the candidate can demonstrate a clinically meaningful disease-modifying effect remains to be determined.

Martin Zügel, interim CEO of AC Immune, described the FDA decisions as important milestones for ACI-7104 and said the company will work with the agency as the program advances.

For now, the regulatory clearance expands the development pathway for ACI-7104, while the upcoming full VacSYn dataset will be critical in determining whether its strong immunogenicity and early biological signals translate into evidence of clinical benefit in Parkinson’s disease.

Reference

AC Immune Receives FDA Fast Track Designation for Anti-Alpha-synuclein Active Immunotherapy, ACI-7104, to Treat Early Parkinson’s Disease (PD) | AC Immune SA