AC Immune SA (ACIU) posts positive interim data from Phase 2 PD trial

Rhea-AI Filing Summary

AC Immune SA reported that it has positive interim safety and immunogenicity data from the Phase 2 VacSYn clinical trial of ACI-7104.056, its wholly owned anti‑alpha‑synuclein active immunotherapy for early Parkinson’s disease. The trial is evaluating this candidate in patients with early-stage Parkinson’s.

The company disclosed that these results were first shared in a press release dated December 11, 2025, which is attached as an exhibit to this Form 6-K for more detailed information.

Insights

Biotech clinical development analyst

Positive interim Phase 2 safety and immunogenicity data mark progress for AC Immune's Parkinson's immunotherapy, but only high-level details are disclosed here.

AC Immune SA reports positive interim safety and immunogenicity findings from its Phase 2 VacSYn trial of ACI-7104.056, an anti‑alpha‑synuclein active immunotherapy for early Parkinson’s disease. Phase 2 studies typically focus on refining dose and characterizing safety and immune response in the target patient population, so interim data at this stage represent a meaningful development step.

The mention of positive safety suggests the candidate has not raised new safety concerns in early Parkinson’s patients so far, while positive immunogenicity indicates it is triggering the intended immune response against alpha‑synuclein. Because only a brief description is provided and no quantitative results, sample size, or duration are stated, the overall clinical and commercial significance will depend on fuller data contained in the attached press release and in future updates.

The update was communicated via a press release dated December 11, 2025, which is incorporated as an exhibit to this Form 6-K. Subsequent detailed disclosures of efficacy outcomes, durability of response, and longer-term safety from this Phase 2 program will be important for understanding how ACI-7104.056 might progress toward later-stage trials in Parkinson’s disease.

UNITED STATES 

SECURITIES AND EXCHANGE COMMISSION 

 Washington, D.C. 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of December, 2025

Commission file number: 001-37891

AC IMMUNE SA  

(Exact Name of Registrant as Specified in Its Charter)

EPFL Innovation Park 

Building B 

1015 Lausanne, Switzerland

 (Address of Principal Executive Offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F  ☒ Form 40-F  ☐

On December 11, 2025, AC Immune SA issued a press release reporting positive interim safety and immunogenicity data from the Phase 2 VacSYn clinical trial evaluating ACI-7104.056, its wholly owned anti-alpha-synuclein (a-syn) active immunotherapy candidate, for the treatment of patients with early Parkinson’s disease (PD). A copy of the press release is attached as Exhibit 99.1 to this Report on Form 6-K.

EXHIBIT INDEX

Exhibit Number		Description
99.1		Press Release, dated December 11, 2025

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

	AC IMMUNE SA
	By:	/s/ Andrea Pfeifer
		Name:  Andrea Pfeifer
		Title:    Chief Executive Officer
	By:	/s/ Christopher Roberts
		Name:  Christopher Roberts
		Title:    Chief Financial Officer
Date:     December 11, 2025

FAQ

What did AC Immune SA (ACIU) report in this Form 6-K?

AC Immune SA reported that it has positive interim safety and immunogenicity data from the Phase 2 VacSYn clinical trial evaluating ACI-7104.056 in patients with early Parkinson’s disease.

What is ACI-7104.056 in AC Immune SA's (ACIU) pipeline?

ACI-7104.056 is described as AC Immune SA’s wholly owned anti‑alpha‑synuclein active immunotherapy candidate being evaluated for the treatment of patients with early Parkinson’s disease.

What is the VacSYn Phase 2 trial mentioned by AC Immune SA (ACIU)?

The VacSYn Phase 2 clinical trial is a study evaluating ACI-7104.056, AC Immune SA’s anti‑alpha‑synuclein active immunotherapy, in patients with early Parkinson’s disease, with interim safety and immunogenicity data reported as positive.

Which disease area is AC Immune SA (ACIU) targeting with ACI-7104.056?

ACI-7104.056 is being developed for the treatment of patients with early Parkinson’s disease, as evaluated in the Phase 2 VacSYn clinical trial.

Where can investors find more details on AC Immune SA's (ACIU) interim Phase 2 data?

More detailed information is available in the press release dated December 11, 2025, which is attached as Exhibit 99.1 to this Form 6-K.

What exhibit is attached to this AC Immune SA (ACIU) Form 6-K?

The Form 6-K includes Exhibit 99.1, which is a press release dated December 11, 2025 discussing the positive interim safety and immunogenicity data from the Phase 2 VacSYn trial of ACI-7104.056.