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