MAO-B x MAO-A

AC Immune Reports First Quarter 2024 Financial Results and Provides a Corporate Update Landmark deal announced with Takeda for ACI-24.060 with $100 million upfront and total potential payments for option exercise and milestones of up to approximately $2.1 billion ACI-24.060 ABATE Phase 2 trial on track to report Abeta-PET imaging results in Q2 2024, evaluating amyloid plaque reduction after 6 months of anti-Abeta active immunotherapy ACI-7104.056 VacSYn Phase 2 trial of anti-a-syn active immunotherapy in Parkinson’s disease (PD) on track for safety and immunogenicity interim data in H2 2024 Three-year cash runway with CHF 104.8 million at quarter end, plus $100 million upfront from Takeda and the anticipated ACI-35.030-related CHF 25 million milestone Lausanne, Switzerland, May 13, 2024 – AC Immune SA (NASDAQ: ACIU), a clinical-stage biopharmaceutical company pioneering the development of precision medicine approaches for the diagnosis, treatment, and prevention of neurodegenerative diseases, today reported results for the quarter ended March 31, 2024, and provided a corporate update. Dr. Andrea Pfeifer, CEO of AC Immune SA, commented: “We are thrilled to have announced today our agreement with Takeda to advance ACI-24.060 anti-Abeta active immunotherapy in Alzheimer’s disease (AD). This landmark collaboration furthers our aim of pioneering Precision Prevention, establishing a powerful force in the neuroscience space that combines the neuroscience knowledge and expertise of AC Immune with the development and commercial experience of Takeda. We remain on track to report the first Phase 2 data this quarter on amyloid plaque reduction as assessed by PET scans after 6-months of treatment. This is a potentially de-risking event for ACI-24.060 that could enable advancement into a registrational study.” “We continue to make strong progress elsewhere in our pipeline. Our partner Janssen continues to push ahead with the launch of the Phase 2b trial, ReTain, evaluating ACI-35.030 (JNJ-64042056), our anti-phospho-Tau active immunotherapy, in patients with pre-symptomatic AD. At the same time, our wholly-owned anti-alpha-synuclein active immunotherapy, ACI-7104.056, is advancing through Phase 2 testing to treat Parkinson’s disease, with safety and immunogenicity updates expected in the second half of 2024. Any of these three studies could be transformational for treatment of patients with neurodegenerative disease. With our significantly strengthened financial position, we are well-positioned to achieve our clinical development milestones across our pipeline through 2024 and beyond.” Q1 2024 and Subsequent Highlights AC Immune and Takeda signed an exclusive Option and License agreement to develop and commercialize ACI-24.060 for AD. Under the terms of the agreement, AC Immune will receive an upfront payment of $100 million from Takeda and, if all related milestones are achieved over the course of the agreement, is eligible to receive payments of up to approximately $2.1 billion including an Option exercise fee in the low-to-mid hundred million range and additional potential development, commercial and sales-based milestones. Upon commercialization, AC Immune will be entitled to receive tiered mid-to-high teens percentages royalties on worldwide net sales. Enrolment in the ACI-24.060 ABATE Phase 2 AD trial continues, with cohorts 1 and 2 now fully enrolled and an expanded cohort 3 targeting completion of enrolment by year end. Six-month Abeta positron emission tomography (PET) imaging results continue to be expected in Q2 2024, and 12-month Abeta-PET data are expected in H2 2024. AC Immune’s therapeutic and diagnostic programs were featured in multiple presentations at the International Conference on Alzheimer’s & Parkinson’s Diseases (AD/PD™ 2024). In addition, Andrea Pfeifer, Ph.D., CEO of AC Immune, led an industry symposium exploring the latest clinical advances in the diagnosis and treatment of alpha-synuclein pathologies. To view a replay of the industry symposium, click HERE. Anticipated 2024 Milestones ACI-24.060 anti-Abeta active immunotherapy 6-month Abeta-PET data in AD expected in Q2 2024 Initial safety and immunogenicity data in Down syndrome cohort expected in H2 2024 12-month Abeta-PET data in AD expected in H2 2024 ACI-7104.056 anti-a-syn active immunotherapy Interim safety and immunogenicity update from the Phase 2 VacSYn study in Parkinson’s disease expected in H2 2024 ACI-35.030 anti-pTau active immunotherapy First patient treated in ReTain Phase 2b clinical trial expected in the coming months Anti-TDP-43 antibody Completion of regulatory tox studies expected in H1 2024 TDP-43-PET tracer Phase 1 initiation expected in H2 2024 ACI-15916 a-syn-PET tracer IND-enabling studies in PD expected to be completed in H2 2024 Analysis of Financial Statements for the Quarter Ended March 31, 2024 Cash position: The Company had a total cash balance of CHF 104.8 million (CHF 103.1 million as of December 31, 2023), composed of CHF 47.8 million in cash and cash equivalents and CHF 57.0 million in short-term financial assets. The Company’s cash balance provides sufficient capital resources for at least three years, when including the upfront payment of $100 million from Takeda, and assuming the potential milestone payment of CHF 24.6 million related to achieving an undisclosed enrolment target for our ACI-35.030, and no other milestones. R&D expenditures: R&D expenses in the period were CHF 15.2 million, compared with CHF 13.9 million for the comparable period in 2023, mainly driven by higher clinical expenses in our ACI-24.060 active immunotherapy as the ABATE study progresses. Other operating income: The Company recognized CHF 0.1 million in grant income from Michael J. Fox Foundation and Target ALS. IFRS loss for the period: The Company reported a net loss after taxes of CHF 17.9 million for the three months ended March 31, 2024, compared with a net loss of CHF 17.5 million for the comparable period in 2023. About AC Immune SA 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 broad and diversified pipeline of first- and best-in-class assets, which currently features sixteen therapeutic and diagnostic programs, including five in Phase 2 development and one in Phase 3. 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 CN, CH, GB, JP, KR, NO and RU. The information on our website and any other websites referenced herein is expressly not incorporated by reference into, and does not constitute a part of, this press release. SVP, Investor Relations & Corporate Communications Gary Waanders, Ph.D., MBA AC Immune Phone: +41 21 345 91 91 Email: gary.waanders@acimmune.com U.S. Investors Corey Davis, Ph.D. LifeSci Advisors Phone: +1 212 915 2577 Email: cdavis@lifesciadvisors.com U.S. and International Media Chris Maggos Cohesion Bureau Phone: +41 79 367 6254 / +1 646 583 2369 Email: chris.maggos@cohesionbureau.com Forward looking statements This press release contains statements that constitute “forward-looking 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,” “anticipates,” “believes,” “estimates,” “predicts,” “projects,” “potential,” “outlook” or “continue,” and other comparable terminology. Forward-looking statements are based on management’s current expectations and beliefs and involve significant risks and uncertainties that could cause actual results, developments and business 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 speak only as of the date they are made, and AC Immune does not undertake any obligation to update them in light of new information, future developments or otherwise, except as may be required under applicable law. All forward-looking statements are qualified in their entirety by this cautionary statement. Condensed Consolidated Balance Sheets (Unaudited) (In CHF thousands) As of March 31, December 31, 2024 2023 Assets Non-current assets Property, plant and equipment 3,236 3,376 Right-of-use assets 3,341 3,508 Intangible asset 50,416 50,416 Long-term financial assets 415 361 Total non-current assets 57,408 57,661 Current assets Prepaid expenses 3,917 6,437 Accrued income 267 246 Other current receivables 868 622 Accounts receivable — 14,800 Short-term financial assets 47,812 24,554 Cash and cash equivalents 57,009 78,494 Total current assets 109,873 125,153 Total assets 167,281 182,814 Shareholders' equity and liabilities Shareholders’ equity Share capital 2,093 2,089 Share premium 475,286 474,907 Treasury shares (105) (105) Currency translation differences (35) (51) Accumulated losses (332,558) (316,197) Total shareholders’ equity 144,681 160,643 Non-current liabilities Long-term lease liabilities 2,657 2,825 Net employee defined benefit liabilities 5,819 5,770 Total non-current liabilities 8,476 8,595 Current liabilities Trade and other payables 2,837 1,679 Accrued expenses 10,541 11,087 Deferred income 74 138 Short-term lease liabilities 672 672 Total current liabilities 14,124 13,576 Total liabilities 22,600 22,171 Total shareholders’ equity and liabilities 167,281 182,814 Condensed Consolidated Statements of Income/(Loss) (Unaudited) (In CHF thousands, except for per-share data) For the Three Months Ended March 31, 2024 2023 Revenue Contract revenue — — Total revenue — — Operating expenses Research & development expenses (15,165) (13,873) General & administrative expenses (4,971) (4,106) Other operating income/(expense), net 68 408 Total operating expenses (20,068) (17,571) Operating loss (20,068) (17,571) Financial income 629 209 Financial expense (36) (97) Exchange differences 1,613 (51) Finance result, net 2,206 61 Loss before tax (17,862) (17,510) Income tax expense — (3) Loss for the period (17,862) (17,513) Loss per share: (0.18) (0.21) Condensed Consolidated Statements of Comprehensive Income/(Loss) (Unaudited) (In CHF thousands) For the Three Months Ended March 31, 2024 2023 Loss for the period (17,862) (17,513) Items that will be reclassified to income or loss in subsequent periods (net of tax): Currency translation differences: 16 (8) Items that will not to be reclassified to income or loss in subsequent periods (net of tax): Remeasurement gains on defined-benefit plans (net of tax) — — Total comprehensive loss, net of tax (17,846) (17,521) Attachment 20240513_ACIU_Q1_Earnings_Final

As well as causing considerable pain, rheumatoid arthritis (RA) can also trigger neuropsychiatric problems including memory impairment. Scientists have now examined the role of monoamine oxidase-B (MAO-B) in RA. MAO-B and related molecules were upregulated in patients' joints and the brain. Rheumatoid arthritis (RA) is an autoimmune disease that causes extensive inflammation of the joints, causing severe pain and discomfort in patients. But did you know that the disease is also commonly accompanied by neuropsychiatric complications, such as cognitive impairment and depression? Previous studies show that up to 70% of RA patients can have such cognitive disorders. These neurological symptoms are thought to be caused by neuroinflammation, which originates from systemic inflammation. However, the precise mechanisms of such cognitive impairment in RA remain unclear. Previously, a team led by Director C. Justin LEE at the Center for Cognition and Sociality within the Institute for Basic Science (IBS) in Daejeon, South Korea, explored the hippocampus of dementia patients to better understand the overall mechanism of memory impairment. The group found that reactive astrocytes release an increased level of monoamine oxidase-B (MAO-B)-dependent gamma-aminobutyric acid (GABA), which in turn leads to neurological disorder. MAOs, including MAO-A and MAO-B, are enzymes that catalyze the oxidation of monoamines and are bound to the outer mitochondrial membrane in cells of several organs, such as the brain and the immune system. More than 30 years ago, previous research suggested that MAO inhibitors can relieve pain and stiffness in RA patients. However, there have been no follow-up studies of these results, and further studies related to the role of MAO in RA have been generally lacking even until today. Recently, Director Lee's team revealed that interleukin-1β (IL-1β), one of these inflammatory substances that are responsible for RA, causes aberrant expression of MAO-B infibroblast-like synoviocytes cells (FLSs) isolated from joint tissues of RA patients. It was been revealed that both MAO-B and GABA are aberrantly expressed in these cells. The team's findings indicate that the expression of MAO-B and MAO-B products, such as GABA and H2O2, can exacerbate joint inflammation by upregulating the expression of proinflammatory factors. It was also observed that MAO-B and GABA levels were significantly increased in the RA tissue compared to the osteoarthritis (OA) tissue, which generally has a lower level of inflammation. Notably, the researcher also observed that the RA animal model showed increased cognitive impairment. In routine behavioral experiments, normal healthy mice had no difficulty remembering a new object or location. On the other hand, it was shown that RA model mice were unable to distinguish new things and objects, which is a hallmark of a cognitive impairment disorder. Similarly to the joint tissues, the secretion of astrocytic MAO-B-dependent GABA was aberrantly increased in the hippocampus, which is thought to be the main cause of this cognitive dysfunction. It has been known that hippocampal astrocytic MAO-B-mediated GABA inhibits neurons, causing memory and cognitive impairment. Based on the fact that astrocytes respond sensitively to inflammation, it was hypothesized that astrocytes would also be affected during the course of RA disease progression, which would lead to cognitive impairment. The first author, Dr. WON Woojin states, "Until now, research on RA has focused only on the mechanism of inflammation, so the cause and treatment of cognitive impairment have not been clear. With a new approach of astrocytes and MAO-B, we were able to determine the cause of cognitive impairment." Subsequently, the IBS researchers decided to administer an MAO-B inhibitor called "KSD2010" in the RA animal model. KDS2010 is a newly developed selective and reversible MAO-B inhibitor, which is currently being tested in phase 1 clinical trials, Once administered in mice, it was discovered that both the joint inflammation decreased and cognitive function recovered at the same time. Taken together, this study revealed both joint inflammation and cognitive impairment have a common underlying mechanism in RA patients, namely aberrant MAO-B expression. This opens the possibility of treating both of these symptoms with one drug. "The mechanism by which cognitive impairment in RA is induced by reactive astrocytes caused by chronic inflammation was first presented. It is hoped that the newly developed and improved MAO-B inhibitor KDS2010 will become an effective next-generation treatment for RA," explains Director C. Justin LEE, who supervised this work.