AC Immune Receives FDA Fast Track Designation for Parkinson Immunotherapy ACI-7104

AC Immune has received fast track designation and clearance of its investigational new drug (IND) application from FDA for ACI-7104, an anti-alpha-synuclein active immunotherapy for early-stage Parkinson disease (PD), the company announced August 11, 2026.¹ The designation will allow the ongoing phase 2 VacSYn trial to expand enrollment to sites in the United States.¹

"Fast track designation and IND clearance from [FDA] are important achievements for ACI-7104, one of our wholly-owned programs, given its potential to address the significant unmet need in [Parkinson]," said Martin Zügel, interim CEO of AC Immune, in a company press release.¹

Why does this designation matter for Parkinson's treatment?

ACI-7104 is designed to induce antibodies that preferentially recognize aggregated, toxic forms of alpha-synuclein, the misfolded protein whose accumulation drives inflammatory stress and neuronal degeneration in PD. The candidate is an optimized formulation of AC Immune's earlier anti-alpha-synuclein active immunotherapy, which previously generated a target-specific antibody response intended to inhibit the spread of pathological alpha-synuclein and downstream neurodegeneration.¹

What clinical data support the designation?

FDA's decision reflects interim phase 2 data reported for Part 1 of the VacSYn trial (NCT06015841) at 76 weeks, which showed ACI-7104 was safe and well tolerated, with no clinically relevant safety issues, and met its immunogenicity target with a 100% responder rate.¹ Those results, first reported in detail in December 2025, also showed consistent trends across multiple disease-related biomarkers and clinical assessments, providing early signals that targeting alpha-synuclein pathology with an active immunotherapy could affect Parkinson's disease progression.² VacSYn is an adaptive, placebo-controlled, biomarker-based phase 2 study enrolling patients with early-stage PD across 2 parts.³

"ACI-7104 represents a promising active immunotherapy designed to target pathological a-syn for the treatment of prodromal and early PD," said Günther Staffler, executive vice president of development at AC Immune, in the release.¹ "This is a key regulatory milestone for the program, and we look forward to delivering the full results from Part 1 of the VacSYn trial in the coming months."

What's next for ACI-7104?

Full week-100 results from Part 1 of the VacSYn trial are expected in the second half of 2026.¹ AC Immune recently received a $4 million research grant from the Vijay and Marie Goradia Charitable Foundation to extend Part 1 of the trial, enabling assessment of ACI-7104's long-term safety and efficacy for an additional 2 years.¹

How does this fit into AC Immune's broader pipeline?

ACI-7104 is one of AC Immune's wholly owned proprietary clinical-stage programs, alongside ACI-19764, a small molecule NLRP3 inflammasome inhibitor, and an early-stage small molecule program targeting intracellular alpha-synuclein. The company also has pharma-partnered programs in Alzheimer disease, including collaborations on ACI-24, targeting amyloid-beta, and ACI-35, targeting phospho-Tau, together representing more than $4.5 billion in potential milestone payments.¹

What are the limitations?

Fast track designation facilitates more frequent FDA interactions but does not indicate that ACI-7104 will receive accelerated or full approval. The reported safety and immunogenicity data are interim findings from an ongoing trial, and full week-100 results, which will determine whether early signals of clinical benefit hold up, have not yet been reported.

References

1. AC Immune. AC Immune receives FDA fast track designation for anti-alpha-synuclein active immunotherapy, ACI-7104, to treat early Parkinson's disease (PD). Press release. Published August 11, 2026. Accessed August 11, 2026. https://ir.acimmune.com/news-releases/news-release-details/ac-immune-receives-fda-fast-track-designation-anti-alpha
2. AC Immune. AC Immune positive interim phase 2 data on ACI-7104.056 support potential slowing of progression of Parkinson's disease. Press release. Published December 11, 2025. Accessed August 11, 2026. https://ir.acimmune.com/news-releases/news-release-details/ac-immune-positive-interim-phase-2-data-aci-7104056-support
3. ClinicalTrials.gov. A study to test whether ACI-7104.056 is effective for people with early Parkinson's disease (VacSYn). NCT06015841. Updated November 21, 2025. Accessed August 11, 2026. https://clinicaltrials.gov/study/NCT06015841