AC Immune Initiates Final Cohort in Ongoing Phase 1b/2 ABATE Trial of Anti-Abeta Active Immunotherapy to Treat Alzheimer's Disease Treatment of first patient in Cohort AD4 in ABATE trial triggers $12 millio

AC Immune Initiates Final Cohort in Ongoing Phase

Trial of Anti-Abeta Active Immunotherapy to Treat Alzheimer's Disease

Lausanne, Switzerland, April 30, 2026 -- AC Immune SA (NASDAQ:

ACIU), a clinical-stage biopharmaceutical company pioneering precision therapeutics for neurodegenerative diseases, today announced it

dosed the first patients in Cohort AD4 in the ongoing Phase 1b/2 ABATE trial. As a result, AC Immune will receive a $12 million milestone

payment from Takeda under the partners' exclusive, worldwide option and license agreement for AC Immune's active immunotherapies

targeting toxic forms of amyloid beta (Abeta), including ACI-24 for the treatment of Alzheimer's disease (AD).

ABATE is assessing ACI-24 in subjects with prodromal AD and in adults

with Down syndrome (DS). AD4 includes subjects with prodromal AD.

Dr. Andrea Pfeifer, CEO of AC Immune SA, said: "This milestone

underscores the progress in our Phase 1b/2 ABATE trial of ACI-24. AD4 will build on the encouraging early safety and immunogenicity data

to date. It allows further evaluation of the potential of ACI-24 and, more broadly, our precision prevention approach to neurodegenerative

diseases, which encompasses a pipeline of active immunotherapies and intracellular-targeted small-molecule therapeutics to intervene at

the earliest stages of disease."

ACI-24 is an anti-Abeta active immunotherapy candidate designed to induce

a robust antibody response against the toxic forms of Abeta believed to drive plaque formation and AD progression. By inducing plaque

clearance and efficiently inhibiting plaque formation in the brain, ACI-24 has the potential to delay or slow AD progression.

ACI-24 is being investigated in the ongoing ABATE randomized, double-blind,

placebo-controlled Phase 1b/2 trial to assess its safety, tolerability, immunogenicity and pharmacodynamic effects. Data so far show that

ACI-24 is generally safe and well tolerated, and that it has generated anti-Abeta antibody responses at all tested doses.

Cohorts AD1, AD2 and AD3 enrolled a total of 74 patients who received

ACI-24 at escalating dose levels. The 12-month data readouts from Cohorts AD1, AD2 and AD3 are expected later in Q2 2026. Cohort AD4 will

include an initial group of 36 patients treated for 12 months, with follow-up of 6 months, significantly expanding the safety and biomarker

efficacy data set. A subsequent expansion of the AD4 cohort could potentially see the total number of subjects reach approximately 112

AC Immune is responsible for conducting the ABATE trial. Following the

potential option exercise, Takeda would conduct and fund all further clinical development and be responsible for all global regulatory

activities as well as worldwide commercialization.

Under the terms of the agreement with Takeda, AC Immune received an

upfront payment of $100 million and is eligible to receive an option exercise fee and additional potential development, commercial and

sales-based milestones of up to approximately $2.1 billion, if all related milestones are achieved over the course of the agreement. Upon

commercialization, AC Immune will be entitled to receive tiered double-digit royalties on worldwide net sales.

This product is AC Immune's anti-Abeta active immunotherapy candidate.

The ABATE randomized, double-blind, placebo-controlled Phase 1b/2 trial of ACI-24 for treatment of Alzheimer's disease (AD) continues

fully blinded (NCT05462106). Enrolled patients are required to have a diagnosis of prodromal AD: MCI due to AD according to the National

Institute on Aging Alzheimer's Association (NIA-AA) criteria, and a PET scan at screening must be consistent with the presence

of amyloid pathology. Patients will be randomized to one of several doses of ACI-24 or placebo. Following multiple data safety monitoring

board (DSMB) reviews, no safety concerns have been raised to date, consistent with previous results. Very encouraging immunogenicity

has been shown with clear evidence of anti-Abeta antibody responses against toxic Abeta species observed in the blinded data.

AC Immune SA is a clinical-stage biopharmaceutical company and a global

leader in precision prevention for neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and NeuroOrphan

indications driven by misfolded proteins. The Company's two clinically validated technology platforms, SupraAntigen and Morphomer ,

fuel its pipeline of first- and best-in-class assets, which currently features a range of therapeutic and diagnostic programs, including

candidates in Phase 2 and Phase 3 development. AC Immune has a strong track record of securing strategic partnerships with leading global

pharmaceutical companies, resulting in substantial non-dilutive funding to advance its proprietary programs and >$4.5 billion in potential

milestone payments plus royalties.

SupraAntigen is a registered trademark of AC Immune SA in the following

territories: AU, EU, CH, GB, JP, RU, SG and USA. Morphomer is a registered trademark of AC Immune SA in CA, CN, CH, EU, GB, JP, KR,

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is expressly not incorporated by reference into, and does not constitute a part of, this press release.

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Forward looking statements

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statements" within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934.

Forward-looking statements are statements other than historical fact and may include statements that address future operating, financial

or business performance or AC Immune's strategies or expectations. In some cases, you can identify these statements by forward-looking

words such as "may," "might," "will," "should," "expects," "plans,"

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"outlook" or "continue," and other comparable terminology. Forward-looking statements are based on management's

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decisions to differ materially from those contemplated by these statements. These risks and uncertainties include those described under

the captions "Item 3. Key Information - Risk Factors" and "Item 5. Operating and Financial Review and Prospects"

in AC Immune's Annual Report on Form 20-F and other filings with the Securities and Exchange Commission. Forward-looking statements

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