abos-20251231

Table of Contents

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

__________________________

FORM 10-K

__________________________

For the fiscal year ended: December 31, 2025

FOR THE TRANSITION PERIOD FROM TO

Commission file number: 001-40551

__________________________

Acumen Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

__________________________

Newton, Massachusetts 02465

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code (617) 344-4190

Securities registered pursuant to Section 12(b) of the Act:

Title of each class TradingSymbol(s) Name of each exchangeon which registered

Common Stock, $0.0001 par value per share ABOS The Nasdaq Global Select Market

Securities registered pursuant to Section 12(g) of the Act: None

__________________________

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. o Yes xNo

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. o Yes xNo

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. xYeso No

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). xYeso No

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large accelerated filer o Accelerated filer o

Non-accelerated filer x Smaller reporting company x

Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. o

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements o

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to § 240.10D-1(b). o

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). o Yes x No

The aggregate market value of the common stock of the registrant held by non-affiliates of the registrant as of June 30, 2025, the last business day of the registrant’s second fiscal quarter, was $45.3 million.

The number of the registrant’s shares of common stock outstanding as of March 20, 2026 was 72,212,758.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive proxy statement relating to its 2026 annual meeting of the shareholders, or the 2026 Proxy Statement, are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. The 2026 Proxy Statement will be filed with the U.S. Securities and Exchange Commission within 120 days after the end of the fiscal year to which this report relates.

Table of Contents

TABLE OF CONTENTS

Page

PART I 1

ITEM 1. BUSINESS 1

ITEM 1A. RISK FACTORS 27

ITEM 1B. UNRESOLVED STAFF COMMENTS 77

ITEM 1C. CYBERSECURITY 78

ITEM 2. PROPERTIES 78

ITEM 3. LEGAL PROCEEDINGS 78

ITEM 4. MINE SAFETY DISCLOSURES 79

ITEM 6. [RESERVED] 80

ITEM 7A. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK 90

ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA 91

ITEM 9A. CONTROLS AND PROCEDURES 117

ITEM 9B. OTHER INFORMATION 118

ITEM 9C. DISCLOSURE REGARDING FOREIGN JURISDICTIONS THAT PREVENT INSPECTIONS 118

ITEM 10. DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE 119

ITEM 11. EXECUTIVE COMPENSATION 119

ITEM 14. PRINCIPAL ACCOUNTING FEES AND SERVICES 119

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES. 120

Table of Contents

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements, within the meaning of the Private Securities Litigation Reform Act of 1995, about us and our industry that involve substantial risks and uncertainties. All statements other than statements of historical facts contained in this Annual Report on Form 10-K including statements regarding our future results of operations or financial condition, business strategy and plans and objectives of management for future operations, are forward-looking statements. In some cases, you can identify forward-looking statements because they contain words such as “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “will” or “would” or the negative of these words or other similar terms or expressions. These forward-looking statements include, but are not limited to, statements concerning the following:

•the sufficiency of our existing cash and cash equivalents and marketable securities to fund our future operating expenses and capital expenditure requirements;

•our ability to obtain funding for our operations, including funding necessary to develop and commercialize sabirnetug or any Aß oligomer-targeted Enhanced Brain Delivery, or EBDTM, product candidates that we may develop pursuant to our collaboration with JCR Pharmaceuticals Co. Ltd., or JCR, subject to obtaining necessary regulatory approvals, and our ability to continue as a going concern;

•the ability of our clinical trials to demonstrate the safety and efficacy of sabirnetug, and other positive results;

•the therapeutic potential of sabirnetug, including its potential for improved safety and efficacy as compared to other monoclonal antibodies approved and or in development, as well as our expectations concerning our ongoing ALTITUDE-AD clinical trial and any future clinical trials we may conduct;

•the structure, focus,success, cost and timing of our development activities, nonclinical studies and clinical trials, and the reporting of data from those clinical trials;

•our plans relating to commercializing sabirnetug or any other product candidate that we may advance into clinical trials, subject to obtaining necessary regulatory approvals;

•our ability to attract and retain key scientific and clinical personnel;

•our ability to contract with third-party suppliers and manufacturers and their ability to perform adequately;

•our reliance on third parties to conduct both preclinical trials related to the potential development of an Aß oligomer-targeted EBDTM therapy and clinical trials of sabirnetug, as well as any other product candidate we may develop, and to manufacture sabirnetug and any other product candidates we may develop for nonclinical studies and clinical trials;

•the success of competing therapies that are or may become available;

•our plans and ability to obtain or protect our intellectual property rights, including extensions of existing patent terms where available or the use of data market exclusivity to provide protection from generic or biosimilar versions of our product;

•the scope of protection we are able to establish and maintain for intellectual property rights covering sabirnetug, any other product candidates we may develop, and our technology;

•potential claims relating to our intellectual property;

•existing regulations and regulatory developments in the United States and other jurisdictions;

•our ability to obtain and maintain regulatory approval of sabirnetug, and any related restrictions, limitations and/or warnings in the label of any approved product candidate;

•our plans relating to the further development and manufacturing of sabirnetug and any other product candidates we may develop, including additional therapeutic indications we may pursue;

•our ability to develop and maintain our corporate infrastructure, including our ability to design and maintain an effective system of internal controls;

•our financial performance; and

•our expectations regarding the time period during which we will be an emerging growth company under the Jumpstart Our Business Startups Act of 2012, or the JOBS Act.

Table of Contents

You should not rely on forward-looking statements as predictions of future events. The outcome of the events described in these forward-looking statements is subject to risks, uncertainties and other factors described under the header “Risk Factors” and elsewhere in this Annual Report on Form 10-K. Moreover, we operate in a very competitive and rapidly changing environment. New risks and uncertainties emerge from time to time, and it is not possible for us to predict all risks and uncertainties that could have an impact on the forward-looking statements contained herein. The results, events and circumstances reflected in the forward-looking statements may not be achieved or occur, and actual results, events or circumstances could differ materially from those described in the forward-looking statements.

The forward-looking statements made in this Annual Report on Form 10-K relate only to events as of the date on which the statements are made, and we undertake no obligation to update them to reflect events or circumstances after the date of this Annual Report on Form 10-K or to reflect new information or the occurrence of unanticipated events, except as required by law.

Unless the context otherwise indicates, references in this report to the terms “Acumen,” “the Company,” “we,” “our” and “us” refer to Acumen Pharmaceuticals, Inc.

We may announce material business and financial information to our investors using our investor relations website (investors.acumenpharm.com). We therefore encourage investors and others interested in Acumen to review the information that we make available on our website, in addition to following our filings with the Securities and Exchange Commission, or SEC, webcasts, press releases and conference calls. Our website and information included in or linked to our website are not part of this Annual Report on Form 10-K.

iii

Table of Contents

RISK FACTORS SUMMARY

Our business is subject to a number of risks of which you should be aware before making a decision to invest in our common stock. These risks are more fully described in “Part I, Item 1A. Risk Factors” of this Annual Report on Form 10-K, including the following:

•We are a clinical-stage biopharmaceutical company with a limited operating history.

•We have no product candidates approved for commercial sale, we have never generated any revenue from product sales and we may never be profitable.

•We will require substantial additional funding to finance our operations, complete the development and commercialization of sabirnetug for Alzheimer’s disease, or AD, and evaluate future product candidates, including any Aß oligomer-targeted EBDTM product candidates that we may develop pursuant to our collaboration with JCR. If we are unable to raise this funding when needed, we may be forced to delay, reduce or eliminate our drug development programs or other operations.

•Our independent registered public accounting firm has included an explanatory paragraph relating to our ability to continue as a going concern in its report in our audited financial statements included in this Annual Report on Form 10-K. If we are unable to obtain sufficient funding, our business, results of operations, financial condition and prospects may be adversely affected and we may be unable to continue as a going concern.

•We are substantially dependent on the success of sabirnetug, our sole product candidate, which will require significant clinical testing before we can seek regulatory approval and potentially launch commercial sales, and which may not be successful in clinical trials, receive regulatory approval or be successfully commercialized, even if approved.

•We have concentrated our research and development efforts on the treatment of AD, a field that has to date seen very limited success in drug development.

•Our approach to the potential treatment of AD is based on a novel therapeutic approach, which exposes us to unforeseen risks.

•Nonclinical and clinical drug development involves a lengthy, expensive and uncertain process. The results of nonclinical studies and early clinical trials are not always predictive of future results. Sabirnetug or any other product candidate that we advance into clinical trials may not achieve favorable results in later clinical trials, if any, or receive marketing approval.

•Clinical failure can occur at any stage of clinical development, and we have never submitted a biologics license application or other marketing authorization application.

•We may incur additional costs or experience delays in completing, or ultimately be unable to complete, the development and commercialization of our product candidates.

•If we are unable to enter into a commercial collaboration or, alternatively, establish internal sales, marketing and distribution capabilities for sabirnetug or any other product candidate, including any Aß oligomer-targeted EBD product candidates that we may develop pursuant to our collaboration with JCR, that may receive regulatory approval, we may not be successful in commercializing those product candidates if and when they are approved.

•We face significant competition in an environment of rapid technological and scientific change, and there is a possibility that our competitors may achieve regulatory approval before us or develop therapies that are safer or more effective than ours.

•We currently rely on contract manufacturing organizations, or CMOs, to supply components of and manufacture sabirnetug. The loss of any of these CMOs or the failure of any of them to meet their obligations to us could affect our ability to develop sabirnetug in a timely manner.

•We intend to rely on contract research organizations and other third parties to conduct, supervise and monitor a significant portion of our research and nonclinical testing and clinical trials for sabirnetug and any future product candidates, and if those third parties do not successfully carry out their contractual duties, comply with regulatory requirements or otherwise perform satisfactorily, we may not be able to obtain regulatory approval or commercialize our product candidates, or such approval or commercialization may be delayed, and our business may be substantially harmed.

Table of Contents

•If we are unable to obtain and maintain sufficient intellectual property protection for sabirnetug and any future product candidate, including any Aß oligomer-targeted EBDTM product candidates, as well as any other proprietary technologies we develop, or if the scope of the intellectual property protection obtained is not sufficiently broad, our competitors could develop and commercialize products similar or identical to ours, and our ability to successfully commercialize our product candidate, and other proprietary technologies if approved, may be adversely affected.

Table of Contents

PART I

Item 1. Business.

Overview

We are a clinical-stage biopharmaceutical company developing a novel disease-modifying approach targeting what we believe to be a key underlying cause of Alzheimer’s disease, or AD. Alzheimer’s disease is a progressive neurodegenerative disease of the brain that leads to loss of memory and cognitive functions and ultimately results in death. Alzheimer’s disease is currently estimated to affect approximately seven million people in the United States and approximately 55 million people worldwide and was the sixth-leading cause of death among individuals aged 65 and older in 2022 in the United States. Due to the aging population, patient populations in the United States impacted by AD are expected to grow to approximately 13 million people by 2050 without effective preventative measures or safe and effective disease-modifying treatments. By 2050, healthcare costs for AD in the United States alone are estimated to near $1 trillion.

Our scientific founders pioneered research on soluble amyloid-beta oligomers, or AßOs, which are globular assemblies of the amyloid-beta, or Aß, peptide that are distinct from Aß monomers and amyloid plaques. Based on decades of research and supporting evidence, AßOs have gained increasing scientific acceptance as a primary toxin involved in the initiation and propagation of AD pathology. We are currently focused on advancing a targeted immunotherapy drug candidate, sabirnetug (ACU193), in our Phase 2 ALTITUDE-AD clinical trial, and expect to announce top-line results in late 2026. Sabirnetug is a recombinant humanized immunoglobulin gamma 2, or IgG2, monoclonal antibody, or mAb, that was designed to selectively target AßOs, has demonstrated functional and protective effects in in vitro assays, and has demonstrated in vivo safety and pharmacologic activity in multiple animal species, including transgenic mouse models for AD, as well as in human AD patients in our Phase 1 INTERCEPT-AD clinical trial of sabirnetug, the results of which were announced in July 2023. ALTITUDE-AD is a randomized, double-blind, placebo-controlled, three-arm clinical trial designed to evaluate the clinical efficacy, safety and tolerability of sabirnetug with up to 180 participants per arm for a total of 542 participants with mild cognitive impairment, or MCI, or mild dementia due to AD. We plan to use the Integrated Alzheimer’s Disease Rating Scale at 18 months as the primary outcome measure. The active doses for ALTITUDE-AD are 35 mg/kg and 50 mg/kg, dosed intravenously every four weeks. These dose levels and frequency were selected based on extensive pharmacokinetic, or PK, and pharmacodynamic, or PD, modeling from our Phase 1 INTERCEPT-AD clinical trial of sabirnetug.

We completed our Phase 1 INTERCEPT-AD clinical trial of sabirnetug in the second quarter of 2023. This trial enrolled 65 participants with early AD, and 62 participants received at least one dose of study drug. INTERCEPT-AD was a U.S.-based, multi-center, randomized, double-blind, placebo-controlled clinical trial with overlapping single ascending dose, or SAD, and multiple ascending dose, or MAD, cohorts evaluating patients with early AD. The overall objective of the trial was to evaluate the safety and tolerability of sabirnetug administered intravenously, or IV, and to establish clinical proof of mechanism of sabirnetug. The primary trial endpoints were focused on safety and immunogenicity. An important safety measure was the use of magnetic resonance imaging, or MRI, to assess the presence or absence of amyloid-related imaging abnormalities, or ARIA. Secondary endpoints included pharmacokinetics in plasma and CSF and target engagement as evidenced by detection of sabirnetug bound to AßOs in CSF. Clinical scales typically used in AD trials as well as computerized cognitive testing and arterial spin labeling, or ASL, with MRI scans (which can be used to assess cerebral blood flow) were included as exploratory measures.

INTERCEPT-AD demonstrated that sabirnetug met the primary and secondary objectives of this clinical trial in 62 participants with early AD. Sabirnetug was well-tolerated throughout the SAD and MAD dose cohorts, with an overall rate of ARIA-E of 10.4%. The incidence of ARIA-E was dose dependent, with a rate of 7% for patients given 10 mg/kg or 25 mg/kg and 21% for patients given 60 mg/kg. An analysis of change in amyloid plaque load, as measured by positron emission tomography, or PET, Centiloids demonstrated a rapid, dose-related mean decrease at the higher dose levels studied. Statistically significant, dose-related central target engagement was observed as measured by sabirnetug-AßO complex, establishing the first target engagement assay developed that is specific to an AßO-targeting antibody. This assay also demonstrated near maximal target engagement for patients receiving 25 mg/kg every two weeks, or Q2W, or 60 mg/kg every four weeks, or Q4W. A number of downstream biomarkers in CSF specific to amyloid and tau pathology and synaptic injury showed improvement in the MAD cohorts, further supporting a drug effect of sabirnetug on Alzheimer’s pathology. These included effects of sabirnetug on p-tau181, which reflects damage to neurons and is known to be elevated in CSF of patients with AD, and effects of sabirnetug on neurogranin and vesicle-associated membrane protein 2, or VAMP2, which reflect damage to neuronal synapsis and are elevated in CSF of patients with AD.

Table of Contents

In addition, we are investigating a blood-brain barrier-penetrating, Aß oligomer-targeted Enhanced Brain Delivery (EBDTM) therapy for the treatment of AD. In March 2026, we announced certain preclinical data from EBD candidates, including in vitro, in vivo and non-human primate study results, supporting the advancement of the EBD program: (1) EBD candidates achieved 14-40x higher brain levels in non-human primates compared to native antibodies 24 hours after dosing; (2) hematology data in non-human primates indicated low potential for anemia, including that, at 24 hours after subcutaneous dosing, EBD candidates demonstrated no observed change in red blood cell count, hematocrit, hemoglobin or reticulocyte count; and (3) favorable stability profile and enhanced brain delivery support a path to subcutaneous administration with low-volume devices. Based on this data, an IND is targeted for mid-2027. In July 2025, we entered into a collaboration, option and license agreement with JCR Pharmaceuticals Co. Ltd., or JCR, to develop an Aß oligomer-targeted EBDTM therapy for AD. Under the terms of the agreement, in addition to an upfront license payment that we paid to JCR, if we exercise our exclusive option to develop up to two development candidates, JCR will be eligible for an option exercise payment of $9.25 million. Our option is expected to be exercised when we have selected or identified up to two preclinical candidates we would license and advance into IND-enabling activities. JCR will also be eligible to receive future milestone payments of up to $40.0 million related to development, and up to $515.0 million related to sales, for a total of up to $555.0 million, as well as single-digit percentage royalties on sales of any products that emerge from the collaboration. The combination of sabirnetug or additional, novel, AβO-selective antibodies with JCR’s blood-brain barrier-penetrating technology, J-Brain Cargo®, strengthens Acumen’s portfolio of AβO-targeted therapies. The partnership is designed to advance potential next-generation treatment options for people living with AD, by targeting the development of products with enhanced efficacy, safety and convenience.

In November 2023, we announced a global collaboration and license agreement with Halozyme, Inc., or Halozyme, to develop a subcutaneous formulation of sabirnetug. We announced the results of a Phase 1 clinical trial investigating a subcutaneous dosing option of sabirnetug in March 2025. This study in healthy volunteers enrolled 16 subjects who received four weekly subcutaneous doses of 1,200 mg of sabirnetug and 12 subjects who received single IV doses of 2,800 mg of sabirnetug. The most frequently reported adverse events included injection site reactions (62.5%), all of which were mild (Grade 1) in severity and resolved. No other safety issues were identified. Additionally, subcutaneous administration of sabirnetug was shown to produce sufficient systemic exposure to support further development of this formulation as a more convenient administration option for patients.

Understanding the Foundation of Our Therapeutic Approach

While the pathology of AD was first described by Dr. Alois Alzheimer in 1906, the amyloid hypothesis was not developed until the Aß peptide was first identified as a major constituent of amyloid plaques in the 1980s. The primary constituent of amyloid plaques is the Aß peptide, although other proteins are present to lesser degrees. Historically, the primary hypothesis of decades of AD research, known as the amyloid hypothesis, held that AD dementia is the clinical consequence of Aß peptide monomers accumulating into extracellular amyloid plaques, which in turn contribute to the formation of intracellular neurofibrillary tangles composed of the tau protein, which is directly linked to neuronal cell death. Additionally, amyloid plaques cause inflammation. The disruption of synaptic function, inflammation and brain cell loss ultimately lead to progressive Alzheimer’s related dementia.

The amyloid hypothesis was more firmly established when a series of genetic mutations causing AD were discovered in the early to mid-1990s. These mutations were found in genes coding for the Amyloid Precursor Protein, or APP, and the genes coding for one of the enzymes which cleaves APP, creating the Aß peptide. Based on this hypothesis, a number of mAbs currently or previously in clinical development for AD have primarily targeted either Aß monomers or amyloid plaques; for our purposes, this broadly defined class is referred to as anti-Aß/plaque antibodies. One of these antibodies, lecanemab, or LEQEMBI®, which was developed to target soluble aggregated species of Aß known as protofibrils, received approval from the U.S. Food and Drug Administration, or the FDA, in 2023. Another antibody, donanemab, which was developed to target amyloid plaques, was approved by the FDAin 2024. The clinical data available to date, even for these approved mAbs, indicate some of the potential limitations of these approaches with respect to clinically meaningful patient benefit and safety.

Though alternative hypotheses to the amyloid hypothesis have been proposed, e.g., that neurodegeneration is a consequence of another process such as infection, the field has now developed an understanding that three predominant pools of Aß species exist in vivo: Aß monomers (single Aß peptides), amyloid plaques (insoluble fibrillar Aß), and soluble AßOs (dimers up to 200-mers). Some experts in the field differentiate soluble AßO oligomers into globular structures or linear protofibrils. Linear soluble Aß protofibrils may elongate to form the insoluble fibrils that make up deposited amyloid plaques.Sabirnetug was developed to bind to globular AßOs rather than to Aß monomers, fibrils or deposited amyloid

Table of Contents

plaques. The more recent recognition of the direct toxicity of soluble AßOs to neurons is the central tenet of our therapeutic approach.

AßOs have been observed to be potent neurotoxins that cause both acute synaptic toxicity and induce neurodegeneration. Experimentally in animal models, the accumulation of AßOs is associated with core AD neuropathology, including synapse deterioration and loss, tau hyper-phosphorylation and inflammation. Research has also shown that the accumulation of AßOs is associated with AD-related behavioral deficits, such as learning and memory impairment. In light of this evidence, we believe that blocking the toxicity of AßOs is a differentiated and promising approach for maximizing the therapeutic index (efficacy compared to safety) for the treatment of AD.

Our Product Candidate

Our product candidate, sabirnetug, is a recombinant humanized, affinity-matured IgG2 subclass mAb, derived from the murine immunoglobulin G1, or IgG1, parent, ACU3B3. Sabirnetug is the result of over a decade of research and development undertaken by the Company, which included a drug discovery partnership with Merck & Co., Inc., or Merck, from 2003 to 2011. Sabirnetug’s mechanism of action is intended to slow disease progression and potentially preserve or improve memory function in early AD patients by binding to AßOs and neutralizing their toxicity. AßOs have been shown to bind to neurons, contributing to synaptic malfunction, memory deficits, cognitive impairment and, ultimately, neurodegeneration and cell death. As such, we believe AßOs are the most toxic and pathogenic form of Aß in the brains of AD patients relative to other forms of amyloid, including Aß monomers and amyloid plaques. We believe the development and commercialization of a drug that reduces toxicity of AßOs is one of the most promising approaches for the potential treatment and prevention of the progression of AD. The target population for sabirnetug and other mAbs approved and in development is what is now being called “early AD.” This population includes people with a clinical diagnosis of MCI or mild dementia due to AD who are also amyloid positive based on either imaging studies or cerebrospinal fluid, or CSF, biochemical analyses. The term “mild cognitive impairment or mild dementia due to AD” has also been used and is accepted by regulators as an inclusion/exclusion criterion in clinical trials. While epidemiologic studies of this population are evolving, approximately four to five million people in the United States are likely to have early AD who also exhibit amyloid pathology associated with AD.

We are currently developing sabirnetug for IV administration Q4W for the treatment of early AD, and we have begun developing sabirnetug for subcutaneous administration as well. We believe that sabirnetug represents a differentiated approach from current and prior anti-Aß/plaque immunotherapies because it is highly selective for soluble toxic AßOs, which may increase the potential for greater efficacy. In our nonclinical studies using an enzyme-linked immunosorbent assay, or ELISA assay, we observed that sabirnetug has over 500-fold greater selectivity for AßOs compared to Aß monomers, and 87-fold greater selectivity for AßOs over Aß fibrils, and limited or no binding to amyloid plaques. In 2024, we completed a nonclinical study using Surface Plasmon Resonance, or SPR, technology, which demonstrated that sabirnetug has up to 8750-fold greater selectivity for AßOs than Aß monomers and compares favorably to other monoclonal antibodies recently approved by the FDA for the treatment of AD. In immunohistochemical studies of human AD brain tissue, sabirnetug appears to have limited binding to amyloid plaques. Sabirnetug has also demonstrated in vivo biochemical and behavioral activity in several AD mouse models, and safety toxicology studies in rats and monkeys provide acceptable margins for acute and chronic dosing in the clinic.

We believe that sabirnetug is the most advanced immunotherapy candidate in development that was designed to selectively target toxic AßOs. Sabirnetug has additional characteristics that make it a promising potential treatment for AD relative to other antibodies that lack selectivity for AßOs. Sabirnetug is designed to have reduced immune effector function signaling and to avoid binding to vascular amyloid plaques, which we expect will reduce the incidence of ARIA as compared to amyloid plaque-targeting immunotherapies approved and in development for AD. We expect to announce top-line results for ALTITUDE-AD, our Phase 2 clinical trial, in late 2026, following positive results from INTERCEPT-AD, a proof of mechanism Phase 1 clinical trial involving early AD patients, in July 2023. We also announced the results ofa Phase 1 clinical trial investigating a subcutaneous dosing option of sabirnetug in healthy volunteersin March 2025.

Clinical Development Plan

ALTITUDE-AD

As noted above, we expect to announce topline results of our Phase 2 clinical trial, ALTITUDE-AD, in late 2026. ALTITUDE-AD is a randomized, double-blind, placebo-controlled, three-arm clinical trial designed to evaluate the clinical efficacy, safety and tolerability of sabirnetug, with a total of 542 participants with MCI or mild dementia due to AD. We intend to use iADRS, a measurement of cognitive and functional decline, at 18 months as the primary outcome measure.

Table of Contents

The doses for ALTITUDE-AD are 35 mg/kg and 50 mg/kg, both dosed IV Q4W. Participants randomized to the 50 mg/kg dose are being administered 35 mg/kg for the first two doses, which is then increased to 50 mg/kg. The 35 and 50 mg/kg doses were selected based on extensive PK/PD modeling of our Phase 1 clinical trial data.

Figure 1. Design of ALTITUDE-AD

INTERCEPT-AD

We reported topline results from INTERCEPT-AD, a U.S.-based, multi-center, randomized, placebo-controlled, SAD and MAD Phase 1 clinical trial of sabirnetug in July 2023. This trial enrolled 65 participants with early AD, and 62 participants received at least one dose of study drug. The early AD patient group was comprised of individuals who have mild dementia or MCI due to AD, and our trial excluded patients with moderate to severe AD dementia. Patients were enrolled across seven cohorts, consisting of a SAD in Part A and an overlapping MAD in Part B. Part A contained Cohorts 1 through 4; each cohort received a single IV dose between 2 mg/kg and 60 mg/kg, or placebo. Part B contained Cohorts 5 through 7; each cohort received a total of three doses of sabirnetug or placebo as follows: 10 mg/kg Q4W, 60 mg/kg Q4W, or 25 mg/kg Q2W.

Figure 2. Design of INTERCEPT-AD

Table of Contents

Trial Design Part A - Single Ascending Dose

In Part A of our clinical trial, participants were randomized in a 6:2 ratio into one of four cohorts to receive a single dose of sabirnetug or placebo as follows:

•Cohort 1: One IV dose of sabirnetug (2 mg/kg) or placebo.

•Cohort 2: One IV dose of sabirnetug (10 mg/kg) or placebo.

•Cohort 3: One IV dose of sabirnetug (25 mg/kg) or placebo.

•Cohort 4: One IV dose of sabirnetug (60 mg/kg) or placebo.

The double-blind treatment period for Cohorts 1-4 of Part A was approximately 20 weeks and included 10 visits (four inpatient and six outpatient). A sequential dosing scheme was followed for each cohort in Part A. Dosing of Cohorts 1-3 began at least one week after all participants in the immediately preceding lower-dose cohort had received one administration of study drug and safety data had been reviewed by our internal blinded safety team. Dosing of Cohort 4 began at least one week after all participants in Cohort 3 received one administration of study drug and these safety data, along with Cohort 2 aggregate PK data, had been reviewed by our internal blinded safety team. An unblinded, independent Data Monitoring Committee, or DMC, also monitored safety data in the trial and was able to review data on an ad hoc basis if requested by the blinded study team.

Trial Design Part B - Multiple Ascending Dose

In Part B of our clinical trial, participants were randomized in an 8:2 ratio into one of three cohorts to receive a total of three doses of sabirnetug or placebo as follows:

•Cohort 5: One IV dose of sabirnetug (10 mg/kg) or placebo once Q4W.

•Cohort 6: One IV dose of sabirnetug (60 mg/kg) or placebo once Q4W.

•Cohort 7: One IV dose of sabirnetug (25 mg/kg) or placebo once Q2W.

Participants in Cohorts 5 and 6 were evaluated over approximately 35 weeks, consisting of a seven-week screening period followed by a 28-week, double-blind treatment period.

Participants in Cohort 7 were evaluated over approximately 31 weeks, consisting of a seven-week screening period, followed by a 24-week, double-blind treatment period.

In order to maintain participant safety for Part B of the clinical trial, dosing of Cohort 5 began at least one week after all participants in Cohort 2 of Part A had received one administration of sabirnetug or placebo and the Cohort 2 safety data had been reviewed by our internal blinded safety team. For Cohort 6, dosing began at least one week after all participants in Cohort 4 of Part A had received one administration of sabirnetug or placebo and the Cohort 4 safety data had been reviewed by our internal blinded safety team. Dosing of Cohort 7 began after review of Cohort 3 and Cohort 4 safety data at least one week after the last person in the cohort was dosed.If a potential safety signal, an unexpected adverse reaction, or higher than expected exposure had occurred, our internal blinded safety team would have notified the independent, unblinded DMC to review the safety and PK data and advise on dose escalation. Cohort 7 allowed for additional PK modeling to more accurately determine if Q2W dosing is necessary and if accumulation of sabirnetug occurs with this dosing frequency.

Endpoints

Our Phase 1 clinical trial established clinical proof of mechanism of sabirnetug in patients with early AD. The endpoints we measured as part of this trial included:

Primary Endpoint

•safety and immunogenicity, including assessment for ARIA.

Secondary Endpoints and Exploratory Objectives

•pharmacokinetics in plasma;

•determination of CSF concentrations of sabirnetug;

Table of Contents

•evaluation of central target engagement as measured by levels of sabirnetug AßO complex in CSF;

•evaluation of possible changes in concentration of biomarkers for AD in CSF or blood;

•evaluation of possible changes in amyloid plaque load as determined by PET imaging;

•exploratory evaluation of possible changes in cerebral blood flow as determined by MRI, using ASL pulse sequence; and

•exploratory evaluation of possible changes in cognitive, functional and behavioral measures using computerized testing and standard clinical measures for AD.

The main objective of INTERCEPT-AD was to evaluate the safety, tolerability, PK, PD, and target engagement of single and multiple ascending doses of sabirnetug administered by IV infusion. Exploratory outcomes included cognitive scales and computerized cognitive testing. Our goal was to establish clinical proof of mechanism of sabirnetug in early AD patients in order to enable progression into further clinical development.

Results

We announced INTERCEPT-AD topline data in July of 2023, which demonstrated that sabirnetug met the primary

and secondary objectives of this clinical trial in 62 participants with early AD.

•An analysis of change in amyloid plaque load, as measured by PET Centiloids, demonstrated a rapid, dose-related mean decrease at the higher dose levels studied. Sabirnetug (60 mg/kg Q4W and 25 mg/kg Q2W) showed a statistically significant reduction in amyloid plaque load as determined by amyloid PET after 6-12 weeks (from baseline to endpoint within cohorts (p=0.01)). This finding provides evidence that sabirnetug is active in the brain.

Figure 3. INTERCEPT-AD plaque reduction observed in highest dose MAD cohorts

•Sabirnetug was well-tolerated throughout the SAD and MAD dose cohorts. Three treatment-emergent serious adverse events were observed after administration of sabirnetug; all were deemed not related or unlikely to be related to sabirnetug. The most common treatment-emergent adverse events from all dose groups combined were ARIA-E (10.4%), ARIA-H (hemorrhage) (8.3%), COVID-19 (6.3%), and hypersensitivity (6.3%). The overall rate of ARIA-E was 10.4%, which included one case of symptomatic ARIA-E (2.1%). Of note, no apolipoprotein E homozygote patients exhibited ARIA-E (n=6 treated).

•PK results in CSF demonstrated statistically significant dose proportionality. Serum PK was dose-related without drug accumulation, and CSF PK was dose- and dose-regimen proportional. Levels of sabirnetug detected in CSF in all cohorts were in excess of endogenous levels of AßOs reported in CSF. Evidence of treatment emergent immunogenicity was observed; anti-drug antibodies were consistently low titer and there was no apparent effect on serum PK. These data support monthly dosing of sabirnetug.

Table of Contents

•Statistically significant, dose-related central target engagement was observed as measured by sabirnetug-AßO

complex, establishing the first target engagement assay developed that is specific to an AßO-targeting antibody. An exposure response relationship (Emax) model revealed near maximal target engagement with repeated dosing at 25 mg/kg and 60 mg/kg.

Figure 4. Near maximal target engagement of AßOs observed in INTERCEPT-AD

•Exploratory measures of potential acute drug effects including assessment of cognition, as determined by a computerized cognitive battery, and changes in cerebral blood flow, as determined by ASL with MRI (Siemens MRI), did not show discernible effects from the immediate administration of sabirnetug. This was not unexpected due to the short duration and small sample size of INTERCEPT-AD.

•Biofluids for assessment of biomarkers of downstream neurodegeneration were collected during the clinical trial.

◦A dose-dependent trend was observed in the MAD cohorts toward sabirnetug effect on CSF biomarkers specific to amyloid and tau pathology and synaptic injury. These included p-tau181, total tau, neurogranin, VAMP2 and the Aß-42/40 ratio. At the 60 mg/kg Q4W dose of sabirnetug, nominally statistically significant improvements in p-tau181 and neurogranin were observed as compared to the placebo group (p=0.049 and p=0.037, respectively). At all doses, statistically significant improvement in VAMP2 was observed compared to placebo (p=0.033 for the 10 mg/kg dose, p=0.041 mg/kg for 25 mg/kg dose and p=0.033 for the 60 mg/kg dose). Nominally significant correlation was also observed between target engagement of AßOs and change in CSF neurogranin across all doses, and a trend was seen for target engagement versus CSF p-tau181.

Table of Contents

Figure 5. CSF biomarker changes observed in INTERCEPT-AD

◦At the 60 mg/kg MAD cohort of sabirnetug, consistent trends were observed in plasma biomarkers, including glial fibrillary acidic protein, p-tau181 and p-tau217. After dosing completed, biomarkers also rebounded toward placebo, further supportive of a drug effect of sabirnetug.

In October of 2023, we met with the FDA to discuss the ALTITUDE-AD clinical trial design, and the potential pathway for registration of sabirnetug. The FDA had previously granted Fast Track designation to ACU193 in October 2022.

Nonclinical and Laboratory Data

In nonclinical studies, sabirnetug has demonstrated promising characteristics that indicate its potential to bind to AßOs as a possible therapeutic treatment of AD. Early studies showed that sabirnetug has high selectivity, with over 500-fold greater binding selectivity for AßOs compared to Aß monomers, 87-fold greater selectivity for AßOs over Aß fibrils, and limited or no binding to amyloid plaques. More recent SPR data demonstrated that sabirnetug has up to 8750-fold greater selectivity for AßOs over Aß monomers and compares favorably to other monoclonal antibodies recently approved by the FDA for the treatment of AD (Figure 6). Sabirnetug binds to a broad spectrum of small to large soluble AßOs. Additionally, sabirnetug has been shown to offer protection from synaptic toxicity by inhibiting binding of AßOs to primary hippocampal neurons. Sabirnetug has also demonstrated suitable in vivo pharmacology, target engagement, blood-brain barrier penetration and reduction of behavioral deficits in transgenic mouse studies. Lastly, Good Laboratory Practice, or GLP, toxicity studies conducted in two animal species supported the Phase 1 clinical trial. We believe these data, combined with our Phase 1 clinical trial results, indicate that sabirnetug has the potential to offer patients a reduction in cognitive decline.

Table of Contents

Figure 6. Relative Selectivity for AßO versus Monomeric Aß Measured with SPR

Selectivity for AßOs

In order to understand sabirnetug selectivity for AßOs, we performed biochemical assays and immunohistochemistry experiments.

Selectivity for AßOs versus Aß monomers

We demonstrated that sabirnetug shows significant preferential selectivity for AßOs compared to Aß monomers. In a competition ELISA assay, sabirnetug’s binding to AßOs was 556-fold greater than sabirnetug’s binding to Aß monomers. Figure 7[A] shows comparative syn-AßO versus Aß monomer affinity data for sabirnetug and illustrates the high selectivity of sabirnetug for AßOs. Further evidence of sabirnetug selectivity for synthetic-AßOs, or syn-AßOs, was obtained using a very high concentration of monomeric Aß, 5 μM, which did not decrease binding to syn-AßOs (Figure 7[B]). We believe sabirnetug’s selectivity for AßOs in the presence of abundant Aß monomers is representative of the in vivo levels of these Aß species in AD patients.

Thus, sabirnetug does not experience “target distraction” from non-toxic Aß monomers in an environment simulating brain interstitial fluid.

Table of Contents

Figure 7. [A] Competitive ELISA for sabirnetug binding to syn-AßO or monomeric Aß40 [B] 5μM monomeric Aß did not substantially change binding to syn-AßO

These results support the conclusion that selectivity of sabirnetug for AßOs is maintained in a biochemical environment simulating the brain.

Selectivity for AßOs versus amyloid plaques

We have shown in our human immunohistochemistry studies that sabirnetug binds AßOs from AD patients with limited or no binding to amyloid plaques. In Figure 8 below, thioflavin S-positive ß-amyloid plaques are shown in green fluorescence while sabirnetug binding is shown in red fluorescence. Sabirnetug binds significantly in regions that are thioflavin-S-negative, i.e., without amyloid plaques (Figure 8, Panels B and E), but only infrequently and minimally may bind to thioflavin-S-positive fibrillar Aß structures in their periphery (Figure 8, Panels D and F). Taken together, these results are consistent with the concept that sabirnetug binds endogenous AßOs, and preferentially binds AßOs versus fibrillar Aß.

Table of Contents

Figure 8. Sabirnetug binding to AßOs versus amyloid plaques

The upper left portion of the immunohistochemistry figure shows that in areas with no amyloid plaque binding (no green fluorescence staining, Panel A) there is substantial binding by sabirnetug (red fluorescence staining, Panel B) that is not related to amyloid plaque. The merge of these panels (Panel E) shows sabirnetug binding with no amyloid plaque present. On the upper right portion of the figure, the area that is positive for amyloid plaque (green fluorescence staining, Panel C) shows minimal sabirnetug binding (red fluorescence staining, Panel D). The merge of these panels (Panel F) shows the minimal binding of sabirnetug (red fluorescence staining) on the periphery of the amyloid plaque (green fluorescence staining), which may be related to AßO binding in the halo of the amyloid plaque.

Binding to a broad spectrum of molecular weight AßOs

In addition, we demonstrated that sabirnetug binds a broad spectrum of AßOs across various molecular weights. In another series of experiments, syn-AßOs were fractionated by size exclusion chromatography and characterized by ELISA using sabirnetug, hu3D6 (bapineuzumab) or hu266 (solanezumab) as the capture antibody and biotinylated anti-human Aß antibody 82E1 for detection. These data show sabirnetug binds AßOs ranging from dimers to approximately 100-mers, with preferential binding to mid-molecular weight oligomers compared to hu266.

Figure 9. Binding of humanized antibodies to size exclusion chromatography fractions of synthetic Aß species

Table of Contents

Size exclusion chromatography fractionation of syn-AßO prep with sandwich ELISA detection. hu3D6 is also known as bapineuzumab; hu266 is also known as solanezumab. These data demonstrate the specificity of sabirnetug for oligomers versus monomers, and also demonstrate a range of oligomers that are bound by sabirnetug.

Collectively the data show that sabirnetug binds AßOs with 556-fold selectivity versus Aß monomers and demonstrates limited to no binding to amyloid plaques, but does bind to a broad range of synthetic and endogenous low, mid, and higher molecular weight AßOs. Based on these and our target engagement data demonstrated in our INTERCEPT-AD Phase 1 clinical trial data, we believe that sabirnetug can target therapeutically relevant AßOs in the brains of early AD patients.

In Vivo Pharmacology

In order to understand the effects of sabirnetug in intact animals, we performed behavioral studies in transgenic mice with genetic alterations that overproduce a mutant APP that forms amyloid plaques. The transgenic mouse models are generally based on autosomal dominant mutations in the APP gene causing rare forms of human AD. Transgenic mouse models using these mutations may not cause the full spectrum of AD pathology, but they do provide relevant animal models for drug development in AD. Taken together, these behavioral studies, performed at three different laboratories, indicate in vivo central pharmacologic activity of peripherally administered ACU3B3. The behavioral effects seen in these studies indicate that sufficient amounts of ACU3B3 cross the blood-brain barrier to engage the target, resulting in behavioral improvements in these transgenic mice.

Pharmacokinetics and Pharmacodynamics

A study of PK in CSF was conducted in rhesus monkeys. An intrathecal catheter was implanted in the monkeys, and two doses at 20 mg/kg IV were administered. As shown in Figure 10, the concentrations of sabirnetug in CSF should provide adequate target engagement with dosing Q4W. This was recapitulated in our INTERCEPT-AD Phase 1 results, which demonstrated near-maximal target engagement of AßOs at both 25 mg/kg Q2W and 60 mg/kg Q4W.

Figure 10. Comparison of sabirnetug levels in rhesus CSF to CSF Levels of AßO in human AD patients

Following two doses of 20 mg/kg sabirnetug CSF concentrations were sufficient to provide target engagement at 28 days. An estimate of 1 fmole/mL for oligomer concentration is conservative given that it is based on AßOs consisting of trimers.

Safety Profile

GLP studies using IV administration of sabirnetug established a no-observed-adverse-effect level, or NOAEL, of 250 mg/kg/dose, which was the maximum feasible dose, given Q2W in a 28-day study in Sprague-Dawley rats. The NOAEL in cynomolgus monkeys was 300 mg/kg/dose in a 14-week study in cynomolgus monkeys using IV dosing Q2W. In Sprague Dawley rats, no adverse findings were noted. In the 14-week study in cynomolgus monkeys, doses of 60, 300 or 600 mg/kg/dose sabirnetug once Q2W were administered. Three animals administered the highest 600 mg/kg/dose were sacrificed early for humane reasons on Days 43 or 60 due to sabirnetug-related, anaphylactoid-type reactions.

Table of Contents

Thus, the 300 mg/kg/dose is considered the NOAEL for cynomolgus monkeys. The NOAELs of 300 mg/kg and 250 mg/kg compare favorably to the highest dose of sabirnetug that was used in our Phase 1 clinical trial (60 mg/kg) and the doses chosen for our Phase 2 clinical trial (30 and 50 mg/kg).

With regard to effector function and possible inflammatory effects generally, sabirnetug is an IgG2 subclass antibody which has limited inflammatory effector function signaling compared to other IgG subclasses.

Combination Potential

While we believe sabirnetug, if successful, will likely be a foundational treatment for people with early AD, it also could be used as part of a combination treatment regimen, including with EBD technology. The pathology of AD is complex, and many experts in the field expect that combination therapy using disease-modifying drugs with different mechanisms of action, such as tau, immune modulation, glial cells such as microglia and astrocytes, and growth factors, will ultimately prove most successful, similar to cutting edge approaches used in oncology. In addition, because symptomatic treatments, such as memantine and cholinesterase inhibitors, affect neurotransmitter systems rather than the underlying AD pathology, we believe that they can be used together with disease-modifying treatments.

Manufacturing

We do not currently own or operate facilities for product manufacturing, storage and distribution, or testing. We contract with third parties for the manufacture of sabirnetug. Because we rely on contract manufacturers, we employ personnel with extensive technical, manufacturing, analytical and quality experience. Our staff has strong project management discipline to oversee contract manufacturing and testing activities, and to compile manufacturing and quality information for our regulatory submissions.

Manufacturing is subject to extensive regulation that imposes various procedural and documentation requirements and that governs record keeping, manufacturing processes and controls, personnel, quality control and quality assurance, and more. Our systems and our contractors are required to be in compliance with these regulations, and compliance is assessed regularly through monitoring of performance and a formal audit program.

Our current supply chains for sabirnetug involve several manufacturers that specialize in specific operations of the manufacturing process, including raw materials manufacturing, drug substance manufacturing and drug product manufacturing. We currently operate under work order programs for sabirnetug with master services agreements in place that include specific supply timelines, volume and quality specifications. We believe our current manufacturers have the scale, the systems and the experience to supply our currently planned clinical trials.

Competition

In June 2021, the FDA granted approval for Biogen Inc.’s, or Biogen’s, Aduhelm® (aducanumab) under the FDA’s Accelerated Approval Pathway, or AAP. Aduhelm was the first new AD product approval since 2004 and the first approved disease-modifying product. In April 2022, the Centers for Medicare and Medicaid Services, or CMS, released a final National Coverage Decision that restricts reimbursement for mAbs directed against amyloid for the treatment of AD, including Aduhelm, under a Coverage with Evidence Development, or CED, designation. The CED designation limits reimbursement of anti-amyloid antibodies, including Aduhelm, to placebo-controlled clinical trials. In May 2022, Biogen announced its decision to eliminate substantially all commercial support for Aduhelm in the United States and withdrew its marketing application for Aduhelm in Europe. In January 2024, Biogen announced its decision to discontinue the development and commercialization of Aduhelm.

In September 2022, Eisai Co., Ltd., or Eisai, announced results from its Leqembi® (lecanemab) Phase 3 CLARITY-AD trial. Leqembi is a recombinant humanized IgG1 mAb directed against aggregated soluble (protofibrils) and insoluble (plaque) forms of Aß. In CLARITY-AD, Leqembi demonstrated highly statistically significant effects on primary and secondary clinical measures (including a 27% slowing of cognitive decline as measured by CDR-SB) and a lower rate of ARIA-E (12.6%) than observed for aducanumab in the Phase 3 EMERGE and ENGAGE studies. In January 2023, the FDA granted approval for Leqembi under the AAP based on results of its Phase 2 clinical trial. In July 2023, the FDA approved the supplemental Biologics License Application, or BLA, supporting the approval of Leqembi. Also in July 2023, CMS announced it would cover Leqembi when a physician and care team participates in a CMS-facilitated registry. While this approval and coverage determination are encouraging developments, the need for additional options for AD treatment and prevention becomes more urgent with each passing year, and we believe that our novel approach can potentially help

Table of Contents

address this pressing need. In August 2025, the FDA approved once-weekly subcutaneous maintenance dosing of Leqembi in patients with early AD following an 18-month intravenous induction period. Moreover, in January 2026, Eisai and Biogen announced that the FDA granted priority review for a subcutaneous starting dose of Leqembi with a Prescription Drug User Fee Act date of May 24, 2026.

In January 2023, the FDA issued a complete response letter, or CRL, to Eli Lilly and Company, or Eli Lilly, for the accelerated approval submission of donanemab. In May 2023, Eli Lilly announced results from its donanemab Phase 3 TRAILBLAZER-ALZ 2 trial. Donanemab is an IgG1 mAb that specifically targets deposited amyloid plaque. In the TRAILBLAZER-ALZ 2 trial, donanemab demonstrated highly statistically significant effects on primary and secondary clinical measures (including a 29% slowing of cognitive decline, as measured by CDR-SB in its high and intermediate tau patient group) with a higher rate of ARIA-E (24%) among all donanemab-treated patients when compared to Leqembi. In July 2024, the FDA approved Kisunla® (donanemab) for the treatment of early AD, and in July 2025, due to the results of the TRAILBLAZER-ALZ 6 study, a modified titration schedule for donanemab was approved and the label was updated, indicating an incidence of ARIA of 14% among donanemab-treated patients by week 24.

There have been no comprehensive head-to-head clinical trials between any of the product candidates discussed above. Study designs and protocols for each product candidate were different, and results may not be comparable among product candidates.

We face competition from several different institutions, including pharmaceutical and biotechnology companies, research institutions, governmental organizations and universities developing novel therapies for AD. We believe that the key factors affecting the clinical and commercial success of sabirnetug will include safety profile, efficacy, method of administration, level of marketing activity, insurance reimbursement and intellectual property protection.

If approved, sabirnetug can be used in combination with therapies currently approved for the treatment of AD that treat the symptoms of AD rather than the underlying cause of the disease, such as memantine and cholinesterase inhibitors.

Other companies known to be developing therapies with Aß-, AßO- and amyloid plaque-related targets include AbbVie Inc., or Abbvie, Alector, Inc., or Alector, Alnylam Pharmaceuticals, Inc., AltPep Corporation, Alzheon, Inc., Alzinova AB, BioArctic AB, Biogen, Bristol-Myers Squibb Company, Cognition Therapeutics, Inc., Denali Therapeutics, Inc., or Denali, Eisai, Eli Lilly, Grifols, S.A., Korsana Biosciences, Inc., Neurimmune AG, Priavoid GmbH, ProMIS Neurosciences, Inc., Prothena Biosciences, Inc., Roche Holding AG (including Genentech, Inc., its wholly-owned subsidiary), or Roche, and Wavebreak Therapeutics, Inc. Additionally, sabirnetug, if approved, may also compete with other potential therapies intended to address underlying causes of AD that are being developed by several companies, including AbbVie, AC Immune SA, Alector, Anavex Life Sciences Corp., Annovis Bio, Inc., Biogen, Biohaven Pharmaceuticals, Inc., Cassava Sciences, Inc., Denali, Eisai, Johnson & Johnson (including Janssen Inc., its wholly-owned subsidiary), H. Lundbeck A/S, Lighthouse Pharmaceuticals, Inc., Roche and Takeda Pharmaceutical Co. Ltd.

Additional Treatment Modalities

While Aß and amyloid are generally considered to be the proximal causes of AD pathology, and alternative hypotheses to the amyloid hypothesis propose that amyloid accumulation is a consequence of other processes such as infection and that other pathogens lead to amyloid accumulation, downstream targets such as tau, inflammation-related targets and growth factors may eventually be useful approaches in the treatment of AD and are being explored. Some of these treatment modalities have made nonclinical and early-stage clinical progress, although these efforts are still significantly less advanced than those approaches targeting Aß or amyloid plaques.

Collaboration Agreement with Merck

In December 2003, we entered into an exclusive license and research and development collaboration agreement with Merck to research, discover and develop certain technology related to Aß-derived diffusible ligands, or ADDLs, which agreement was amended and restated in October 2006. The agreement generally provided that, during the course of the collaboration, Merck would be responsible for the preclinical and clinical development and commercialization of any products covered by the agreement and, in return, we were eligible to receive potential nonclinical, clinical and regulatory milestone payments and royalties on future product sales. During the collaboration, Merck developed sabirnetug, an ADDL antibody, and intellectual property related to sabirnetug was filed by Merck. In 2011, Merck elected to voluntarily terminate the collaboration agreement. Pursuant to the surviving provisions of the agreement, effective upon termination of the collaboration, Merck granted us an exclusive, perpetual, irrevocable, royalty-free, worldwide license, with right to

Table of Contents

sublicense, under Merck’s interest in the patent rights and know-how necessary for the research, development, manufacturing or commercialization of ADDL antibodies, ADDL antigens or products, including sabirnetug.

License Agreement with Lonza

On November 2, 2022, the Company entered into a license agreement, or the Lonza License Agreement, with Lonza Sales AG, or Lonza. Under the terms of the Lonza License Agreement, Lonza granted the Company a worldwide non-exclusive license to use Lonza’s glutamine synthetase gene expression system to manufacture and commercialize sabirnetug, or the Lonza Product.

Pursuant to the Lonza License Agreement, we paid Lonza an upfront fee of 1.0 million Swiss Francs. The Company is also required to pay certain royalties upon commercialization and annual payments on a country-by-country basis in respect of the manufacturing and sale of the Lonza Product, which include (i) a royalty of less than 1.0% on net sales where Lonza manufactures the Lonza Product, (ii) an annual royalty payment in Swiss Francs in the low six-digits and a royalty of less than 1.0% on net sales where the Company manufactures the Lonza Product and (iii) an annual payment in Swiss Francs in the mid six-digits per sublicense and a royalty on net sales in the low single digits where a third party manufactures the Lonza Product. These payment obligations would expire 10 years from the first commercial sales of the Lonza Product in such country of sale.

The Lonza License Agreement continues until terminated, and the Company or Lonza may terminate the Lonza License Agreement for uncured material breaches or insolvency of the other party. The Company can unilaterally terminate the Lonza License Agreement with prior written notice to Lonza, and Lonza can also unilaterally terminate the Lonza License Agreement upon certain actions by the Company. The Lonza License Agreement also contains customary representations, warranties, indemnification and other obligations of the Company and Lonza.

Halozyme License Agreement

On November 5, 2023, the Company entered into a non-exclusive collaboration and license agreement, or the Halozyme License Agreement, with Halozyme. Under the terms of the Halozyme License Agreement, Halozyme granted the Company a non-exclusive license to Halozyme’s ENHANZE® drug delivery technology for the development of a subcutaneous formulation of sabirnetug, or the Halozyme Product. Halozyme will also be the Company’s exclusive supplier of clinical and commercial supplies of the active pharmaceutical ingredient for Halozyme’s PH20 product.

Pursuant to the Halozyme License Agreement, the Company paid Halozyme a seven-figure upfront payment for the license to Halozyme’s technology. Additionally, the Company will make milestone payments tied to achievement of certain development and commercialization milestone events with respect to the Halozyme Product, as well as milestone payments based on achievement of certain net sales levels of the Halozyme Product. The Company will also make single-digit royalty payments based on worldwide net sales of the Halozyme Product.

The Halozyme License Agreement includes customary termination rights, representations and warranties, covenants and indemnification obligations for a transaction of this nature.

JCR License Agreement

In July 2025, we entered into a collaboration, option and license agreement with JCR to develop an Aß oligomer-targeted EBDTM therapy for the treatment of AD. Under the terms of the agreement, in addition to an upfront license payment that we paid to JCR, if we exercise our exclusive option to develop up to two development candidates, JCR will be eligible for an option exercise payment of $9.25 million. Our option is expected to be exercised when we have selected or identified up to two preclinical candidates we would license and advance into IND-enabling activities. JCR will also be eligible to receive future milestone payments of up to $40.0 million related to development, and up to $515.0 million related to sales, for a total of up to $555.0 million, as well as single-digit percentage royalties on sales of any products that emerge from the collaboration. The combination of sabirnetug or additional, novel, AβO-selective antibodies with JCR’s blood-brain barrier-penetrating technology, J-Brain Cargo®, strengthens Acumen’s portfolio of AβO-targeted therapies. The partnership is designed to advance potential next-generation treatment options for people living with AD, by targeting the development of products with enhanced efficacy, safety and convenience.

Table of Contents

Intellectual Property

Our intellectual property is critical to our business and we strive to protect it, including by obtaining and maintaining patent protection in the United States and internationally for our product candidate. We also rely on the skills, knowledge and experience of our scientific and technical personnel, as well as that of our advisors, consultants and other contractors. To help protect our proprietary know-how that is not patentable, we rely on confidentiality agreements to protect our interests. We require our employees, consultants, scientific advisors and contractors to enter into confidentiality agreements prohibiting the disclosure of confidential information and requiring disclosure and assignment to us of the ideas, developments, discoveries and inventions important to our business.

The main form of commercial exclusivity for our product candidate, sabirnetug, is expected to come from biologic regulatory exclusivity. We expect that once approved by regulatory agencies, sabirnetug will receive the benefit of 12 years of market exclusivity in the United States and 10 to 11 years of data and market exclusivity in Europe, in each case, against competitors seeking approval for a biosimilar product.

We have an exclusive license grant from Merck to patents claiming the composition and method of use of our product candidate, sabirnetug. The license grant arose from our collaboration agreement with Merck to research, discover and develop technology related to ADDLs. During our collaboration, sabirnetug, an ADDL antibody, was developed and intellectual property was filed by Merck. In 2011, the collaboration agreement terminated and Merck exclusively licensed to Acumen Merck’s interest in patent rights claiming ADDL antibodies, including sabirnetug, ADDL Antigens and/or Products to Acumen. In the nine years subsequent to the termination of the collaboration with Merck, Acumen has controlled and directed and continues to control and direct prosecution of the licensed sabirnetug patent portfolio. Acumen has also paid for and continues to pay all costs and fees associated with the prosecution and maintenance of the licensed sabirnetug patent portfolio.

As of March 27, 2025, Acumen licenses from Merck one issued U.S. patent and 18 issued foreign patents, including issued patents in Brazil, China, Canada, Australia, Japan, South Korea, France, Germany and the UK drawn to our product candidate, sabirnetug. These patents are projected to expire in July 2031, without taking into account any possible extensions and assuming payment of all appropriate maintenance, renewal, annuity or other governmental fees.

Throughout the development of our product candidate, we seek to identify additional means of obtaining patent protection that would potentially enhance commercial success, including by protecting inventions related to additional methods of use, processes of making, formulation and dosing regimens.

Patent Term and Term Extensions

The terms of individual patents are determined based primarily on the date of filing of the patent application or the date of patent issuance and the legal term of patents in the countries in which they are obtained. Generally, utility patents issued for applications filed in the United States are granted a term of 20 years from the earliest effective filing date of a non-provisional patent application. In addition, in certain instances, the term of a U.S. patent can be extended to recapture a portion of the United States Patent and Trademark Office, or USPTO, delay in issuing the patent as well as a portion of the term effectively lost as a result of the FDA regulatory review period. However, as to the FDA component, the restoration period cannot be longer than five years and the restoration period cannot extend the patent term beyond 14 years from FDA approval for the product covered by that patent. In addition, only one patent applicable to an approved drug may receive the extension, and the extension applies only to coverage for the approved drug, methods for using it and methods of manufacturing it, even if the claims cover other products or product candidates. Where one patent covers multiple products or product candidates, it may only receive an extension for one of the covered products; any extension related to a second product or product candidate must be applied to a different patent. The duration of foreign patents varies in accordance with provisions of applicable local law, but typically is also 20 years from the earliest effective filing date of a non-provisional patent application, such as a Patent Cooperation Treaty application. All taxes, annuities or maintenance fees for a patent, as required by the USPTO and various foreign jurisdictions, must be timely paid in order for the patent to remain in force during this period of time.

The actual protection afforded by a patent may vary on a product-by-product basis, from country to country, and can depend upon many factors, including the type of patent, the scope of its coverage, the availability of regulatory-related extensions and the availability of legal remedies in a particular country and the validity and enforceability of the patent.

Our patents and patent applications may be subject to procedural or legal challenges by others. We may be unable to obtain, maintain and protect the intellectual property rights necessary to conduct our business, and we may be subject to

Table of Contents

claims that we infringe or otherwise violate the intellectual property rights of others, which could materially harm our business. For more information, see the section titled “Risk Factors—Risks Related to Our Intellectual Property.”

Trademarks and Know-How

In connection with the ongoing development and advancement of our products and services in the United States and various international jurisdictions, we seek to create protection for our marks and enhance their value by pursuing trademarks and service marks where available and when appropriate. We rely upon know-how and continuing technological innovation to develop and maintain our competitive position. We seek to protect our proprietary information, in part, by using confidentiality agreements with our commercial partners, collaborators, employees and consultants, and invention assignment agreements with our employees and consultants. These agreements are designed to protect our proprietary information and, in the case of the invention assignment agreements, to grant us ownership of technologies that are developed by our employees and through relationships with third parties. These agreements may be breached, and we may not have adequate remedies for any breach. In addition, our trade secrets may otherwise become known or be independently discovered by competitors. To the extent that our contractors, commercial partners, collaborators, employees and consultants use intellectual property owned by others in their work for us, disputes may arise as to the rights in related or resulting know-how and inventions. For more information, see the section titled “Risk Factors—Risks Related to Our Intellectual Property.”

Government Regulation

The FDA and other regulatory authorities at federal, state and local levels, as well as in foreign countries, extensively regulate, among other things, the research, development, testing, manufacture, quality control, import, export, safety, effectiveness, labeling, packaging, storage, distribution, record keeping, approval, advertising, promotion, marketing, pricing, reimbursement, post-approval monitoring and post-approval reporting of biologics such as those we are developing. The process of obtaining regulatory approvals and the subsequent compliance with applicable federal, state, local and foreign statutes and regulations, both pre-approval and post-approval, require the expenditure of substantial time and financial resources. The regulatory requirements applicable to drug and biological product development, approval and marketing are subject to change, and regulations and administrative guidance often are revised or reinterpreted by the agencies in ways that may have a significant impact on our business.

U.S. Biologics Regulation

In the United States, biological products are subject to regulation under the Federal Food, Drug, and Cosmetic Act, or FDCA, the Public Health Service Act and other federal, state and local statutes and regulations. The process required by the FDA before biologics may be marketed in the United States generally involves the following:

•completion of preclinical laboratory tests and animal studies performed in accordance with the FDA’s GLP requirements;

•submission to the FDA of an investigational new drug application, or IND, which must become effective before clinical trials may begin and must be updated annually and when certain changes are made;

•approval by an institutional review board, or IRB, or independent ethics committee at each clinical site before the trial is commenced;

•performance of adequate and well-controlled human clinical trials in accordance with Good Clinical Practices, or GCPs, requirements and other clinical trial-related regulations to establish the safety, purity and potency of the proposed biologic product candidate for its intended purpose;

•preparation of and submission to the FDA of a BLA after completion of all pivotal clinical trials;

•payment of user fees for FDA review of the BLA;

•satisfactory completion of an FDA Advisory Committee review, if applicable;

•a determination by the FDA within 60 days of its receipt of a BLA to file the application for review;

•satisfactory completion of an FDA pre-approval inspection of the manufacturing facility or facilities at which the proposed product is produced to assess compliance with current Good Manufacturing Practices, or cGMPs, and to assure that the facilities, methods and controls are adequate to preserve the biological product’s continued safety, purity and potency, and of selected clinical investigation sites to assess compliance with GCPs; and

Table of Contents

•FDA review and approval of the BLA to permit commercial marketing of the product for particular indications for use in the United States.

Failure to comply with the applicable regulatory requirements at any time during the product development process or post-approval may subject an applicant to delays in development or approval, as well as administrative and judicial sanctions.

Preclinical and Clinical Trials

Prior to beginning the first clinical trial with a product candidate, the product candidate must undergo rigorous preclinical testing. Preclinical studies include laboratory evaluations of chemistry, formulation and stability, as well as in vitro and animal studies to assess safety and in some cases to establish the rationale for therapeutic use. The conduct of preclinical studies is subject to federal and state regulations and requirements, including GLP requirements for safety and toxicology studies. The results of the preclinical studies, together with manufacturing information and analytical data, must be submitted to the FDA as part of an IND. An IND is a request for authorization from the FDA to administer an investigational new drug to humans. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, raises safety concerns or questions about the proposed clinical trial, including concerns that human research subjects will be exposed to unreasonable health risks. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns or questions before the clinical trial can begin.

The FDA may, at any time during the initial 30-day IND review period, or while clinical trials are ongoing, impose a partial or complete clinical hold based on concerns for patient safety and/or noncompliance with regulatory requirements. This order issued by the FDA would delay a proposed clinical study or cause suspension of an ongoing study until all outstanding concerns have been adequately addressed and the FDA has notified the company that investigations may proceed. Imposition of a clinical hold could cause significant delays or difficulties in completing planned clinical studies in a timely manner. Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCPs, which include the requirement that all research subjects provide their informed consent for their participation in any clinical study. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the dosing procedures, subject selection and exclusion criteria, and the parameters and criteria to be used in monitoring safety and effectiveness. A separate submission to the existing IND must be made for each successive clinical trial conducted during product development and for any protocol and subsequent protocol amendments. Furthermore, an independent IRB for each site proposing to conduct the clinical trial must review and approve the plan for any clinical trial and its informed consent form before the clinical trial begins at that site, and must monitor the study until completed. In addition, the IRB or the sponsor may suspend a clinical trial at any time on various grounds, including a finding that the subjects are being exposed to an unacceptable health risk, that the trial is unlikely to meet its stated objectives or that the trial is not being conducted in accordance with FDA requirements. Some studies also include oversight by an independent group of qualified experts organized by the clinical study sponsor, known as a data safety monitoring board or DMC, which provides authorization for whether or not a study may move forward at designated checkpoints based on access to certain data from the study and may halt the clinical trial if it determines that there is an unacceptable safety risk to subjects or on other grounds, such as lack of efficacy.

Information about applicable clinical trials, including clinical trials results, must be submitted within specific timeframes for publication on the www.clinicaltrials.gov website.

IND sponsors must submit annual reports on the progress of investigations under the IND to the FDA and submit IND safety reports when certain serious and unexpected adverse reactions and certain other safety issues occur.

For purposes of BLA approval, human clinical trials are typically conducted in three sequential phases that may overlap or be combined:

•Phase 1-The investigational product is initially introduced into a limited population of healthy human subjects or patients with the target disease or condition. These studies are designed to test the safety, dose response, absorption, metabolism and distribution of the investigational product in humans, the side effects associated with increasing doses, and, if possible, to gain early evidence on effectiveness.

•Phase 2-The investigational product is administered to a limited patient population with a specified disease or condition to evaluate the preliminary efficacy, optimal dosages and dosing schedule and to identify possible adverse side effects and safety risks. Multiple Phase 2 clinical trials may be conducted to obtain information prior to beginning larger and more expensive Phase 3 clinical trials.

Table of Contents

•Phase 3-The investigational product is administered to an expanded patient population to further evaluate dosage, to provide statistically significant evidence of clinical efficacy and to further test for safety, generally at multiple geographically dispersed clinical trial sites. These clinical trials are intended to establish the overall risk/benefit ratio of the investigational product and to provide an adequate basis for product approval. Generally, two adequate and well-controlled Phase 3 clinical trials are required by the FDA for approval of a BLA.

In some cases, the FDA may require, or companies may voluntarily pursue, additional clinical trials after a product is approved. These trials are used to gain additional data from the treatment of patients in the intended therapeutic indication and are commonly intended to generate additional safety data regarding use of the product in a clinical setting. These so-called Phase 4 studies may also be made a condition to approval of the BLA.

Concurrent with clinical trials, companies may complete additional animal studies and develop additional information about the biological characteristics of the product candidate and must finalize a process for manufacturing the product in commercial quantities in accordance with cGMP requirements. The manufacturing process must be capable of consistently producing quality batches of the product candidate and, among other things, must develop methods for testing the identity, strength, quality and purity of the final product. Additionally, appropriate packaging must be selected and tested, and stability studies must be conducted to demonstrate that the product candidate does not undergo unacceptable deterioration over its shelf life and to identify appropriate storage conditions for the product candidate.

BLA Submission and Review by the FDA

Assuming successful completion of all required testing in accordance with all applicable regulatory requirements, the results of product development, nonclinical studies and clinical trials are submitted to the FDA as part of a BLA requesting approval to market the product for one or more indications. To support marketing approval, the data submitted must be sufficient in quality and quantity to establish the safety, purity and potency of the investigational biologic, to the satisfaction of the FDA. FDA approval of a BLA must be obtained before a biologic may be marketed in the United States. The submission of a BLA requires payment of a substantial application user fee to the FDA, unless a waiver or exemption applies.

Within 60 days following submission of the application, the FDA reviews a BLA submitted to determine if it is substantially complete before the FDA accepts it for filing. Once a BLA has been accepted for filing, the FDA’s goal is to review standard applications within 10 months after the filing date, or, if the application qualifies for priority review, six months after the FDA accepts the application for filing. In both standard and priority reviews, the review process may also be extended by FDA requests for additional information or clarification.

Before approving a BLA, the FDA will typically inspect the facility or facilities where the product is manufactured. The FDA will not approve an application unless it determines that the manufacturing processes and facilities are in compliance with cGMPs and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA will typically inspect one or more clinical sites to assure compliance with GCP and other requirements and the integrity of the clinical data submitted to the FDA.

After the FDA evaluates a BLA and conducts inspections of manufacturing facilities where the investigational product and/or its drug substance will be produced, the FDA may issue an approval letter or a CRL. An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A CRL will describe all of the deficiencies that the FDA has identified in the BLA, except that where the FDA determines that the data supporting the application are inadequate to support approval, the FDA may issue the CRL without first conducting required inspections, testing submitted product lots, and/or reviewing proposed labeling. In issuing the CRL, the FDA may recommend actions that the applicant might take to place the BLA in condition for approval, including requests for additional information or clarification. The FDA may delay or refuse approval of a BLA if applicable regulatory criteria are not satisfied, require additional testing or information and/or require post-marketing testing and surveillance to monitor safety or efficacy of a product.

If regulatory approval of a product is granted, such approval will be granted for particular indications and may entail limitations on the indicated uses for which such product may be marketed. For example, the FDA may approve the BLA with a Risk Evaluation and Mitigation Strategy, or REMS, to ensure the benefits of the product outweigh its risks. A REMS is a safety strategy implemented to manage a known or potential serious risk associated with a product and to enable patients to have continued access to such medicines by managing their safe use, and could include medication guides,

Table of Contents

physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling, the development of adequate controls and specifications, or the completion of post-marketing studies or surveillance programs.

Expedited Development and Review Programs

The FDA offers a number of expedited development and review programs for qualifying product candidates. These programs include Fast Track designation, Breakthrough Therapy designation, and priority review.

The Fast Track program is intended to expedite or facilitate the process for reviewing new products that are intended to treat a serious or life-threatening disease or condition and demonstrate the potential to address unmet medical needs for the disease or condition. Fast Track designation applies to the combination of the product and the specific indication for which it is being studied. The sponsor of a Fast Track product has opportunities for more frequent interactions with the applicable FDA review team during product development, in addition to the potential for rolling review of the BLA, meaning that the FDA may consider for review sections of the BLA on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the BLA, the FDA agrees to accept sections of the BLA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the BLA.

A product candidate intended to treat a serious or life-threatening disease or condition may also be eligible for Breakthrough Therapy designation if preliminary clinical evidence indicates that the product candidate, alone or in combination with one or more other drugs or biologics, may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. The designation includes all of the Fast Track program features, as well as more intensive FDA interaction and guidance beginning as early as Phase 1 and an organizational commitment to expedite the development and review of the product candidate, including involvement of senior managers and experienced review staff in a cross-disciplinary review, where appropriate.

Any marketing application for a drug or biologic submitted to the FDA for approval, including a product candidate with a Fast Track designation and/or Breakthrough Therapy designation, may be eligible for priority review. A product candidate is eligible for priority review if it is designed to treat a serious or life-threatening disease or condition, and if approved, would provide a significant improvement in safety or effectiveness compared to available alternatives for such disease or condition. For original BLAs, priority review designation means the FDA’s goal is to take action on the marketing application within six months of the 60-day filing date (as compared to 10 months under standard review).

Fast Track designation, Breakthrough Therapy designation and priority review do not change the standards for approval but may expedite the development or approval process. Even if a product candidate qualifies for one or more of these programs, the FDA may later decide that the product no longer meets the conditions for qualification or decide that the time period for FDA review or approval will not be shortened.

Accelerated approval pathway

The FDA may grant accelerated approval to a product candidate for a serious or life-threatening condition that provides meaningful therapeutic advantage to patients over existing treatments based on a determination that the product has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity, or prevalence of the condition and the availability or lack of alternative treatments.

As a condition of accelerated approval, the FDA will generally require the sponsor to perform adequate and well-controlled post-marketing clinical studies to verify and describe the anticipated effect on irreversible morbidity or mortality or other clinical benefit. Products receiving accelerated approval may be subject to expedited withdrawal procedures if the sponsor fails to conduct the required post-marketing studies or if such studies fail to verify the predicted clinical benefit. In addition, the FDA currently requires as a condition for accelerated approval pre-approval of promotional materials, which could adversely impact the timing of the commercial launch of the product. FDORA, signed by President Biden on December 29, 2022 as part of the Consolidated Appropriations Act, 2023 (H.R. 2617), includes numerous reforms to the accelerated approval process for drugs and biologics and enables the FDA to require, as appropriate, that a post-approval study be underway prior to granting accelerated approval. FDORA also expands the expedited withdrawal procedures

Table of Contents

already available to the FDA to allow the agency to use expedited procedures if a sponsor fails to conduct any required post-approval study of the product with due diligence, including with respect to “conditions specified by the Secretary [of HHS].” FDORA also adds the failure of a sponsor of a product approved under accelerated approval to conduct with due diligence any required post-approval study with respect to such product or to submit timely reports with respect to such product to the list of prohibited acts in the FDCA.

Orphan Drug Designation and Exclusivity

Under the Orphan Drug Act, the FDA may grant orphan drug designation, or ODD, to a drug or biologic intended to treat a rare disease or condition, defined as a disease or condition with a patient population of fewer than 200,000 individuals in the United States, or a patient population greater than 200,000 individuals in the United States and when there is no reasonable expectation that the cost of developing and making available the drug or biologic in the United States will be recovered from sales in the United States for that drug or biologic. ODD must be requested before submitting a BLA. After the FDA grants ODD, the generic identity of the therapeutic agent and its potential orphan use are disclosed publicly by the FDA.

If a product that has received ODD subsequently receives the first FDA approval for that drug for the disease for which it has such designation, the product is entitled to orphan product exclusivity, which means that the FDA may not approve any other applications, including a full BLA, to market the same biologic for the same indication for seven years, except in limited circumstances, such as a showing of clinical superiority to the product with orphan drug exclusivity or if the FDA finds that the holder of the orphan drug exclusivity has not shown that it can assure the availability of sufficient quantities of the orphan drug to meet the needs of patients with the disease or condition for which the drug was designated. Orphan drug exclusivity does not prevent the FDA from approving a different drug or biologic for the same disease or condition, or the same drug or biologic for a different disease or condition. Among the other benefits of ODD are tax credits for certain research and a waiver of the BLA user fee.

Post-approval Requirements

Biologics are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to record-keeping, reporting of adverse experiences, periodic reporting, product sampling and distribution, and complying with advertising and promotion requirements, which include restrictions on promoting products for unapproved uses or patient populations (known as “off-label use”) and limitations on industry-sponsored scientific and educational activities. The FDA and other agencies actively enforce the laws and regulations applicable to biologics, including those prohibiting the promotion of off-label uses, and a company that is found to have improperly promoted off-label uses may be subject to significant liability. Promotional materials for approved biologics must be submitted to the FDA in conjunction with their first use or first publication.

After approval, most changes to the approved product, such as adding new indications or other labeling claims, are subject to prior FDA review and approval. There are also continuing annual program fees for any marketed products. Biologic manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies, and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with ongoing regulatory requirements, including cGMPs. Changes to the manufacturing process are strictly regulated, and, depending on the significance of the change, may require prior FDA approval before being implemented. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMPs and other aspects of regulatory compliance.

The FDA may withdraw approval if compliance with regulatory requirements and standards is not maintained or if problems occur after the product reaches the market. Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or with manufacturing processes, or failure to comply with regulatory requirements, may result in revisions to the approved labeling to add new safety information; imposition of post-market studies or clinical studies to assess new safety risks; or imposition of distribution restrictions or other restrictions under a REMS program. Other potential consequences include, among other things:

•restrictions on the marketing or manufacturing of the product, complete withdrawal of the product from the market or product recalls;

•safety alerts, Dear Healthcare Provider letters, press releases or other communications containing warnings or other safety information about the product;

•fines, warning letters or untitled letters;

Table of Contents

•clinical holds on clinical studies;

•refusal of the FDA to approve pending applications or supplements to approved applications, or suspension or revocation of product license approvals;

•product seizure or detention, or refusal to permit the import or export of products;

•consent decrees, corporate integrity agreements, debarment or exclusion from federal healthcare programs;

•mandated modification of promotional materials and labeling and the issuance of corrective information; and

•the imposition of civil or criminal penalties.

United States Biosimilars and Exclusivity

The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act of 2010, or collectively, the ACA, signed into law in 2010, includes a subtitle called the Biologics Price Competition and Innovation Act, or BPCIA, which created an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-licensed reference biological product. The FDA has issued several guidance documents outlining an approach to review and approval of biosimilars in the United States. Biosimilarity requires that there be no clinically meaningful differences between the biological product and the reference product in terms of safety, purity and potency. Interchangeability requires that a product is biosimilar to the reference product, and the product must demonstrate that it can be expected to produce the same clinical results as the reference product in any given patient and, for products that are administered multiple times to an individual, the biologic and the reference biologic may be alternated or switched after one has been previously administered without increasing safety risks or risks of diminished efficacy relative to exclusive use of the reference biologic.

Under the BPCIA, a reference biological product is granted 12 years of data exclusivity from the time of first licensure of the product, and an application for a biosimilar product may not be submitted to the FDA until four years following the date that the reference product was first licensed by the FDA. In addition, the approval of a biosimilar product may not be made effective by the FDA until 12 years from the date on which the reference product was first licensed. During this 12-year period of exclusivity, another company may still market a competing version of the reference product if the FDA approves a full BLA for the competing product containing that applicant’s own preclinical data and data from adequate and well-controlled clinical trials to demonstrate the safety, purity and potency of its product. The BPCIA also created certain exclusivity periods for biosimilars approved as interchangeable products.

The BPCIA is complex and continues to be interpreted and implemented by the FDA. In addition, government proposals have sought to reduce the 12-year reference product exclusivity period. Other aspects of the ACA, some of which may impact the BPCIA exclusivity provisions, have also been the subject of recent litigation. As a result, the ultimate impact, implementation and regulatory interpretation of the BPCIA remain subject to significant uncertainty.

Other Healthcare Laws

Pharmaceutical companies are subject to additional healthcare regulation and enforcement by the federal government and by authorities in the states and foreign jurisdictions in which they conduct their business, which may constrain their business operations, including financial arrangements related to the research, marketing and distribution of drug products. Such laws include, without limitation, the following, some of which may apply to our operations only if and when we have a marketed product:

•the federal Anti-Kickback Statute, which prohibits, among other things, individuals or entities from knowingly and willfully soliciting, receiving, offering or paying any remuneration (including any kickback, bribe or rebate), directly or indirectly, overtly or covertly, in cash or in kind in return for, or to induce, either the referral of an individual, or the purchase, lease, order or arrangement for or recommendation of the purchase, lease, order or arrangement for any good, facility, item or service for which payment may be made, in whole or in part, under a federal healthcare program, such as the Medicare and Medicaid programs. The term “remuneration” has been broadly interpreted to include anything of value. A person does not need to have actual knowledge of this statute or specific intent to violate it in order to have committed a violation. Although there are a number of statutory exceptions and regulatory safe harbors protecting some common activities from prosecution, the exceptions and safe harbors are drawn narrowly;

•the federal civil and criminal false claims laws, including, without limitation, the federal False Claims Act, or FCA, which prohibit, among other things, individuals or entities from knowingly presenting, or causing to be

Table of Contents

presented, to the federal government, claims for payment or approval that are false or fraudulent or knowingly making a false statement to avoid, decrease or conceal an obligation to pay money to the federal government. In addition, the government may assert that a claim including items or services resulting from a violation of the federal Anti-Kickback Statute constitutes a false or fraudulent claim for purposes of the FCA;

•the federal civil monetary penalties laws, which impose civil fines for, among other things, the offering or transfer of remuneration to a Medicare or state healthcare program beneficiary if the person knows or should know it is likely to influence the beneficiary’s selection of a particular provider, practitioner or supplier of services reimbursable to Medicare or a state health program, unless an exception applies;

•the federal Health Insurance Portability and Accountability Act, or HIPAA, which created additional federal criminal statutes which prohibit, among other things, a person from knowingly and willfully executing, or attempting to execute, a scheme to defraud any healthcare benefit program, including private third-party payors and knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false, fictitious or fraudulent statement in connection with the delivery of or payment for healthcare benefits, items or services. Similar to the federal Anti-Kickback Statute, a person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation;

•HIPAA, as amended by the Health Information Technology for Economic and Clinical Health Act, and their implementing regulations, also imposes obligations on “covered entities,” including certain healthcare providers, health plans, healthcare clearinghouses, and their respective “business associates,” if those business associates create, receive, maintain or transmit individually identifiable health information for or on behalf of a covered entity as well as the business associates’ covered subcontractors, with respect to safeguarding the privacy, security and transmission of individually identifiable health information, as well as analogous state and foreign laws that govern the privacy and security of health information in some circumstances, many of which differ from each other in significant ways and often are not preempted by HIPAA, thus complicating compliance efforts;

•the FDCA, which, among other things, strictly regulates drug product and medical device marketing, prohibits manufacturers from marketing such products for off-label use and regulates the distribution of samples;

•federal laws, such as the Medicaid Drug Rebate Program, that require pharmaceutical manufacturers to report certain calculated product prices to the government or provide certain discounts or rebates to government authorities or private entities, often as a condition of reimbursement under governmental healthcare programs;

•the so-called federal “sunshine law,” or Open Payments, which requires manufacturers of drugs, devices, biologics and medical supplies to report to the CMS information related to payments and other transfers of value to teaching hospitals, physicians and other healthcare practitioners, as well as ownership and investment interests held by physicians and their immediate family members;

•federal and state consumer protection and unfair competition laws, which broadly regulate marketplace activities and activities that potentially harm consumers; and

•analogous state laws and regulations, such as state anti-kickback and false claims laws, which may apply to sales or marketing arrangements and claims involving healthcare items or services reimbursed by non- governmental third-party payors, including private insurers, and state laws which regulate interactions between pharmaceutical companies and healthcare providers, require pharmaceutical companies to comply with the pharmaceutical industry’s voluntary compliance guidelines and the relevant compliance guidance promulgated by the federal government, require pharmaceutical companies to report information on transfers of value to other healthcare providers, marketing expenditures or pricing information and/or require licensing or registration of sales representatives.

Ensuring compliance with healthcare laws is time-consuming and costly. Given the breadth of the laws and regulations and narrowness of any exceptions, limited guidance for certain laws and regulations and evolving government interpretations of the laws and regulations, governmental authorities may possibly conclude that our business practices are non-compliant. Efforts to ensure that our business arrangements with third parties will comply with applicable healthcare laws and regulations will involve substantial costs. Any action against us for violation of these laws, even if we successfully defend against it, could cause us to incur significant legal expenses and divert our management’s attention from the operation of our business. If our operations are found to be in violation of any of the laws described above or any other government regulations that apply to us, we may be subject to penalties, including, without limitation, civil and criminal penalties, damages, fines, imprisonment, exclusion from participating in federal and state funded healthcare programs, such as Medicare and Medicaid, additional reporting requirements and oversight if we become subject to a corporate integrity

Table of Contents

agreement or similar agreement to resolve allegations of non-compliance with these laws, contractual damages, diminished profits and future earnings, reputational harm and the curtailment or restructuring of our operations, any of which could adversely affect our business, financial condition, results of operations and prospects.

Coverage and Reimbursement

The ability of a pharmaceutical company to successfully commercialize and achieve market acceptance of a product depends in significant part on adequate coverage and reimbursement from third-party payors, including government healthcare programs, such as the Medicare and Medicaid programs, and private entities, such as managed care organizations and private health insurers.

In the United States, no uniform policy of coverage and reimbursement for drug products exists among third-party payors and coverage and reimbursement for drug products can differ significantly from payor to payor. The process for determining whether a third-party payor will provide coverage for a product may be separate from the process for setting the price or reimbursement rate that the payor will pay for the product once coverage is approved.

Third-party payors are increasingly challenging the prices charged, examining the medical necessity, and reviewing the cost-effectiveness of medical products and services and imposing controls to manage costs. Coverage and reimbursement by a third-party payor may depend upon a number of factors, including the third-party payor’s determination that a procedure is safe, effective and medically necessary; appropriate for the specific patient; cost-effective; supported by peer-reviewed medical journals; included in clinical practice guidelines; and neither cosmetic, experimental nor investigational. To obtain or maintain coverage and reimbursement for any approved drug product, a pharmaceutical manufacturer may need to conduct expensive pharmacoeconomic studies or otherwise provide evidence to demonstrate the medical necessity and cost-effectiveness of a product. These studies will be in addition to the studies required to obtain or maintain regulatory approvals. If third-party payors do not consider a product to be cost-effective compared to other available therapies, the payors may not cover the product or, if they do, the level of payment may not be sufficient to allow sale of a product at a profit.

Even if third-party payors provide some coverage, they may impose limits on the coverage or controls to manage utilization of products.Third-party payors may limit coverage to specific products on an approved list, or formulary, which might not include all of the approved products for a particular indication and can exclude drugs from their formularies in favor of competitor drugs or alternative treatments. Payors may also impose step edits that require patients to try alternative, including generic, treatments before authorizing payment for our products, limit the types of diagnoses for which coverage will be provided, require pre-approval (known as “prior authorization”) for coverage of a prescription for each patient (to allow the payor to assess medical necessity) or impose a moratorium on coverage for products while the payor makes a coverage decision.

Moreover, a third-party payor’s decision to provide coverage for a product does not mean that an adequate reimbursement rate will be approved.A pharmaceutical company may be required to provide mandatory discounts or rebates to certain purchasers to obtain coverage under federal healthcare programs or to sell products to government purchasers. A pharmaceutical company may also have to offer discounts or rebates to private third-party payors to obtain favorable coverage. There has been significant consolidation in the health insurance industry, increasing the leverage of large insurers and pharmacy benefit managers in pricing and other negotiations and potentially impacting potential drug product sales, business and results of operations. Adequate third-party reimbursement may not be available to enable a company to realize an appropriate return on an investment in product development.

The containment of healthcare costs has become a priority of federal and state governments, and the prices of products have been a focus in this effort. Governments have shown significant interest in implementing cost-containment programs, including price controls, restrictions on reimbursement and requirements for substitution of generic products. Adoption or enhancement of price controls and cost-containment measures could further limit a company’s revenue generated from the sale of any approved products. Coverage policies and third-party payor reimbursement rates may change at any time. Even if favorable coverage and reimbursement status is attained for one or more products for which a company receives regulatory approval, less favorable coverage policies and reimbursement rates may be implemented in the future.

Healthcare Reform

In the United States and some foreign jurisdictions, there have been, and likely will continue to be, a number of legislative and regulatory healthcare reform initiatives directed at broadening the availability of healthcare, improving the quality of

Table of Contents

healthcare, and containing or lowering the cost of healthcare. These reform initiatives, if and when implemented, could impact our ability to sell a product candidate profitably if and when approved for marketing. For example, in 2010, the ACA was enacted, which, among other things, subjected biologic products to potential competition by lower-cost biosimilars; addressed a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted or injected; increased the minimum Medicaid rebates owed by most manufacturers under the Medicaid Drug Rebate Program; extended the Medicaid Drug Rebate Program to utilization of prescriptions of individuals enrolled in Medicaid managed care organizations; subjected manufacturers to new annual fees and taxes for certain branded prescription drugs; and established a Medicare Part D coverage gap discount program.More generally, the ACA expanded healthcare coverage through Medicaid expansion and the implementation of the “individual mandate” for health insurance coverage.

Beyond the ACA, there have been ongoing healthcare reform efforts, including efforts focused on drug pricing and payment.For example, the Inflation Reduction Act of 2022, or IRA, includes a number of changes intended to address rising prescription drug prices in Medicare Parts B and D. These changes include caps on Medicare Part D out-of-pocket costs, Medicare Part B and Part D drug price inflation rebates, a new Medicare Part D manufacturer discount drug program (replacing the previous ACA Medicare Part D coverage gap discount program) and a drug price negotiation program for certain high spend Medicare Part B and D drugs (with negotiated prices for the first set of drugs scheduled to take effect in 2026). The IRA has had and will likely continue to have a significant impact on the pharmaceutical industry. Additionally, changes to Medicaid effective in 2024 eliminated the Medicaid rebate cap, and changes to certain Medicare price reporting requirements for drugs beginning in 2026 will likely increase the administrative and compliance burden for manufacturers.

More recently, President Trump issued an Executive Order in April 2025 with multiple directives aimed at lowering drug prices, including refining the Medicare drug price negotiation program established by the IRA; accelerating competition for high-cost prescription drugs by accelerating approval of generics and biosimilars and facilitating the process for re-classifying prescription drugs as over-the-counter drugs; and increasing drug importation. In May 2025, President Trump issued another Executive Order that directed government agencies and officials to identify most-favored nation pricing targets for prescription drugs (and looked to pharmaceutical manufacturers to make significant progress towards delivering target prices to patients); prevent foreign countries from disproportionately shifting the cost of global pharmaceutical research and development to the United States; and facilitate direct-to-consumer purchasing programs for pharmaceutical manufacturers to sell their products to patients at the most-favored-nation price. In the wake of the Executive Orders and related executive initiatives, a number of pharmaceutical manufacturers have announced direct-to-consumer offerings with discounted prices and/or reached agreement with the federal government regarding pricing for drugs, including prices for Medicaid drugs and newly launched products.A website sponsored by the federal government offering pharmaceutical direct-to-consumer channels has also been launched.Federal agencies are developing new drug pricing pilot programs, such as a voluntary Medicaid initiative which would authorize the federal government to negotiate Medicaid supplemental rebates with participating manufacturers on behalf of state Medicaid programs, in exchange for standardized coverage criteria for participating manufacturer drugs, and proposed Medicare Part B and Part D pilot models that, if finalized as proposed, would replace existing inflation-based Medicare rebates with rebates determined on the basis of international prices, for drugs and patients subject to the model.Many of these reform initiatives would require additional legal and/or administrative action to implement and may be subject to legal challenge.

Other federal healthcare reform efforts or actions may affect access to healthcare coverage or the funding of health care benefits, although the full impact of such efforts or actions cannot be predicted. For example, the Congressional Budget Office has estimated that Medicaid provisions in the 2025 budget reconciliation legislation, including restrictions in eligibility and funding for Medicaid, as well as changes to the healthcare marketplace, such as the elimination of certain subsidies, will increase the number of uninsured. Individual states in the United States have also become increasingly active in implementing regulations designed to control pharmaceutical product pricing, including price or patient reimbursement constraints, discounts, restrictions on certain product access and marketing cost disclosure and transparency measures, and, in some cases, designed to encourage importation from other countries and bulk purchasing.

Healthcare reform efforts have been and may continue to be subject to scrutiny, legal challenge and subsequent amendment, creating further uncertainty.

Other recent government actions may also affect prices or payments for prescription drugs. For example, the current presidential administration’s recently announced tariff on branded or patented drugs may increase the cost of drug products that are imported from abroad or manufactured using products or materials imported from abroad. The timeline for implementation of this tariff has not yet been finalized. As another example, the Budget Control Act of 2011, as amended,

Table of Contents

resulted in the imposition of reductions in Medicare (but not Medicaid) payments to providers in 2013 and will remain in effect into 2032 unless additional Congressional action is taken. Any significant spending reductions affecting Medicare, Medicaid or other publicly funded or subsidized health programs that may be implemented and/or any significant taxes or fees that may be imposed on us could have an adverse impact on our results of operations.

Adoption of new legislation at the federal or state level could affect demand for, or pricing of, any future products if approved for sale. We cannot, however, predict the ultimate content, timing or effect of any federal and state reform efforts. There is no assurance that federal or state healthcare reform will not adversely affect our future business and financial results.

Employees and Human Capital Resources

Our human capital objectives include, as applicable, identifying, recruiting, retaining, incentivizing and integrating our existing and new employees, advisors and consultants. The principal purposes of our equity incentive plans are to attract, retain and reward personnel through the granting of stock-based compensation awards.

As of March 25, 2026, we had 61 employees, 60 of which were full time. Of our 61 employees, 40 were engaged in research and development and 21 were engaged in general and administrative functions. We also utilized consultants in various roles related to research and development and general and administrative functions. We believe our employee relations are good.

Corporate Information

We were incorporated under the laws of the State of Delaware in 1996. Our principal executive offices are located at 1210-1220 Washington Street, Suite 210, Newton, MA 02465 and our telephone number is (617) 344-4190.

Available Information

Our website address is http://www.acumenpharm.com/. In addition to the information about us contained in this Annual Report on Form 10-K, information about us can be found on our website. Our website and information included in or linked to our website are not part of this Annual Report on Form 10-K.

Our annual reports on Form 10-K, quarterly reports on Form 10-Q, current reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, are available free of charge through our website as soon as reasonably practicable after they are electronically filed with or furnished to the U.S. Securities and Exchange Commission, or the SEC. Additionally, the SEC maintains an internet site that contains reports, proxy and information statements and other information. The address of the SEC’s website is www.sec.gov.

Table of Contents

Item 1A. Risk Factors.

The following information sets forth risk factors that could cause our actual results to differ materially from those contained in forward-looking statements we have made in this Annual Report on Form 10-K and those we may make from time to time. You should carefully consider the risks described below, in addition to the other information contained in this Annual Report on Form 10-K and our other public filings. Our business, financial condition or results of operations could be harmed by any of these risks. The risks and uncertainties described below are not the only ones we face. Additional risks not presently known to us or other factors not perceived by us to present significant risks to our business at this time also may impair our business operations.

Risks Related to our Financial Position and Capital Needs

We are a clinical-stage biopharmaceutical company with a limited operating history.

We are a clinical-stage biopharmaceutical company with a limited operating history developing a novel disease-modifying approach targeting what we believe to be a key underlying cause of Alzheimer’s disease, or AD. We were incorporated in 1996 and were party to an exclusive license and research collaboration with Merck & Co., Inc., or Merck, in 2003. Although we acquired the exclusive rights to sabirnetug from Merck in 2011, following Merck’s strategic decision to focus its AD development efforts on a different product candidate, we did not recommence meaningful operations until we completed our first institutional fundraising in 2018. As a result, we have a limited operating history, which may make it difficult to evaluate the success of our business to date and to assess our future viability. Drug development is a highly uncertain undertaking and involves a substantial degree of risk. We received authorization of our Investigational New Drug application, or IND, for our sole product candidate, sabirnetug, and initiated our Phase 1 clinical trial in the second quarter of 2021. In October 2021, we announced the initial dosing of the first patient in the INTERCEPT-AD trial and in February 2023 we announced the completion of enrollment. We announced topline data from INTERCEPT-AD in July 2023. We initiated our Phase 2 clinical trial, ALTITUDE-AD, in May 2024, completed enrollment in March 2025 and expect to announce top-line results in late 2026. We also conducted a Phase 1 clinical trial investigating a subcutaneous dosing option of sabirnetug in mid-2024 and announced results in March 2025. In addition, we announced a collaboration with JCR Pharmaceuticals Co. Ltd., or JCR, in July 2025, pursuant to which we are conducting preclinical studies, in coordination with JCR, to assess a blood-brain barrier-penetrating, Aß oligomer-targeted Enhanced Brain Delivery (EBDTM) therapy for the treatment of AD. We have previously experienced delays in site activation and enrollment with respect to our INTERCEPT-AD clinical trial, and cannot assure you that we will not experience additional delays in site activation or enrollment in our future clinical trials. To date, we have not yet initiated a pivotal trial, obtained marketing approval for any product candidate, manufactured a commercial scale product candidate, arranged for a third party to do so on our behalf or conducted sales or marketing activities necessary for successful product candidate commercialization. Our short operating history makes any assessment of our future success and viability subject to significant uncertainty. We will likely encounter risks and difficulties frequently experienced by early-stage biopharmaceutical companies in rapidly evolving fields, and we have not yet demonstrated an ability to overcome such risks and difficulties successfully. If we do not address these risks and difficulties successfully, our business will suffer.

We have no product candidates approved for commercial sale, we have never generated any revenue from product sales and we may never be profitable.

We have no product candidates approved for sale, have never generated any revenue from product sales, have never been profitable and do not expect to be profitable in the foreseeable future. We have incurred net losses in each year since our inception. For the years ended December 31, 2025 and 2024, our net losses were $121.3 million and $102.3 million, respectively. As of December 31, 2025, we had an accumulated deficit of $446.5 million.

To date, we have devoted most of our financial resources to the research and development of sabirnetug, including our nonclinical development activities of sabirnetug and our clinical trials, and corporate overhead. We expect that it will be several years, if ever, before we have a product candidate approved and ready for commercialization. We expect to continue to incur losses for the foreseeable future, and we expect these losses to increase as we continue our development of, and seek regulatory approvals for, sabirnetug and any other product candidate we may develop in the future, prepare for and begin the commercialization of any approved product candidates and add infrastructure and personnel to support our drug development efforts and operations as a public company. We anticipate that any such losses could be significant for the next several years. These net losses and negative cash flows have had, and will continue to have, an adverse effect on our stockholders’ equity and working capital. Further, these net losses may fluctuate significantly from quarter-to-quarter or year-to-year. To become and remain profitable, we must develop and eventually commercialize sabirnetug or another drug with significant revenue.

Table of Contents

We may never succeed in developing a commercial drug, and, even if we succeed in commercializing one or more product candidates, we may never generate revenues that are large enough to achieve profitability. In addition, we may encounter unforeseen expenses, difficulties, complications, delays and other known or unknown challenges. Because of these numerous risks and uncertainties, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to generate revenues or achieve profitability. If we do achieve profitability, we may not be able to sustain or increase profitability on a quarterly or annual basis, and we will continue to incur substantial research and development costs and other expenditures to develop and market additional product candidates.

We will require substantial additional funding to finance our operations, complete the development and commercialization of sabirnetug for AD and evaluate future product candidates, including any Aß oligomer-targeted EBDTM product candidates we may develop pursuant to our collaboration with JCR. If we are unable to raise additional funding when needed, we may be forced to delay, reduce or eliminate our drug development programs or other operations.

To date, we have used substantial amounts of cash to fund our operations, and we expect our expenses to increase substantially in the foreseeable future in connection with our ongoing activities, particularly as we continue the research and development, conduct clinical trials of, and seek marketing approval for, sabirnetug and any future product candidates we may develop. Developing sabirnetug and conducting clinical trials for the treatment of AD and any other product candidates or indications that we may pursue in the future will require substantial amounts of capital. In addition, if we obtain marketing approval for sabirnetug or any future product candidates, we expect to incur significant commercialization expenses related to the commercialization of the product, whether we are commercializing alone or with a collaborator. Further, we expect to incur significant expenses associated with operating as a public company.

Accordingly, we will need to obtain substantial additional funding in connection with our continuing operations. As of December 31, 2025, we had $54.0 million in cash and cash equivalents and $62.9 million in marketable securities. Based on our current operating plan, we believe that our existing cash and cash equivalents and marketable securities will be sufficient to enable us to fund our operating expenses and capital expenditure requirements into early 2027. In addition, changing circumstances may cause us to increase our spending significantly faster than we currently anticipate, and we may need to spend more money than currently expected because of circumstances beyond our control. We may need to raise additional funds sooner than anticipated if we choose to expand more rapidly than we presently anticipate.

The amount and timing of our future funding requirements will depend on many factors, some of which are outside of our control, including but not limited to:

•the progress, costs, timing and results of ALTITUDE-AD and other potential clinical trials of sabirnetug and/or preclinical trials related to the potential development of an Aß oligomer-targeted EBDTM therapy, or for any potential additional indications that we may pursue beyond AD;

•the requirements of the U.S. Food and Drug Administration, or FDA, and the European Medicines Agency, or EMA, and comparable foreign regulatory authorities, for clinical trials and nonclinical studies and other work, for review and approval of sabirnetug for AD;

•the outcome, costs and timing of seeking and obtaining FDA, EMA and any other regulatory approvals;

•the number and characteristics of product candidates that we pursue;

•our ability to obtain sufficient quantities of our product candidates from our third-party manufacturers;

•our need to expand our research and development activities;

•the costs associated with securing and establishing commercialization capabilities if we were to elect to commercialize one or more products on our own;

•the economics and other terms, timing of and success of any collaboration, licensing or other arrangements into which we may enter for the commercialization of our products;

•the costs and other terms, timing and success, of acquiring, in-licensing or investing in businesses, product candidates and technologies;

•our ability to maintain, expand and defend the scope of our intellectual property portfolio, including the amount and timing of any payments we may be required to make, or that we may receive, in connection with the licensing, filing, prosecution, defense and enforcement of any patents or other intellectual property rights;

•our need and ability to retain management and hire scientific and clinical personnel;

Table of Contents

•the effect of competing drugs and product candidates and other market developments; and

•our need to implement additional internal systems and infrastructure, including financial and reporting systems.

Additional funding may not be available to us on acceptable terms or at all. Any such funding may result in dilution to stockholders, imposition of debt covenants and repayment obligations or other restrictions that may affect our business. We also could be required to seek funds through arrangements with collaborative partners or otherwise that may require us to relinquish rights to some of our technologies or product candidates or otherwise agree to terms unfavorable to us. Any funds we raise may not be sufficient to enable us to continue to implement our long-term business strategy. Further, our ability to raise additional capital may be adversely impacted by potential worsening global economic conditions. Additionally, escalation in interest rates may lead to financial institutions being more prudent with capital deployment and tightening lending. If we are unable to raise sufficient additional capital on a timely basis, we could be forced to curtail our planned operations and the pursuit of our business strategy, which would have a material adverse effect on the value of our common stock.

Our independent registered public accounting firm has included an explanatory paragraph relating to our ability to continue as a going concern in its report on our audited financial statements included in this Annual Report on Form 10-K.

The report from our independent registered public accounting firm for the year ended December 31, 2025 includes an explanatory paragraph stating that our recurring losses from operations raise substantial doubt about our ability to continue as a going concern for at least 12 months after the date of issuance of the financial statements included in this Annual Report on Form 10-K and we will need to obtain additional funding. See Note 1 to our financial statements appearing elsewhere in our Annual Report on Form 10-K for additional information on our assessment.

If we are unable to obtain sufficient funding to support our current operating plan, we may be forced to delay or reduce the scope of our product development programs, reduce our research and development costs, limit or cease our operations; our business, results of operations, financial condition and prospects may be adversely affected; and we may be unable to continue as a going concern. Our cash forecast contains estimates and assumptions related to our ongoing clinical trial and other research and development expenses, and we cannot predict the amount or timing of all expenditures with certainty. Nevertheless, our financial statements do not include any adjustments that might result from the outcome of this uncertainty.

We cannot guarantee that we will be able to obtain any or sufficient additional funding or that such funding, if available, will be obtainable on terms satisfactory to us. If we seek additional financing to fund our business activities in the future and there remains substantial doubt about our ability to continue as a going concern, investors or other financing sources may be unwilling to provide additional funding to us on commercially reasonable terms or at all. If we are unable to continue as a going concern, we may have to liquidate our assets and may receive less than the value at which those assets are carried on our audited financial statements, and it is likely that investors will lose all or a part of their investment. There can be no assurance that the current operating plan will be achieved in the time frame anticipated by us, or that our cash resources will fund our operating plan for the period we anticipate.

The terms of our Loan Agreement place restrictions on our operating and financial flexibility. If we raise additional capital through debt financing, the terms of any new debt could further restrict our operating and financial flexibility.

In November 2023, we entered into the Loan Agreement with K2 HealthVentures LLC, or K2HV. At closing, we borrowed $30.0 million in the first tranche under the Loan Agreement. We may borrow an additional $20.0 million under the Loan Agreement upon our request, subject to review by the lenders of certain information from the Company and discretionary approval by the lenders.

Our obligations under the Loan Agreement are secured by a security interest in substantially all of our assets, excluding the Company’s intellectual property. The Loan Agreement includes customary affirmative and negative covenants, as well as standard events of default, including an event of default based on the occurrence of a material adverse event. The negative covenants include, among others, restrictions on us transferring collateral, incurring additional indebtedness, engaging in mergers or acquisitions, paying cash dividends or making other distributions, making investments, creating liens, selling assets and making any payment on subordinated debt, in each case subject to certain exceptions. These restrictive covenants could limit our flexibility in operating our business and our ability to pursue business opportunities that we or our stockholders may consider beneficial. In addition, K2HV could declare a default upon the occurrence of any event that it interprets could have a material adverse effect, subject to the limitations specified in the Loan Agreement. Upon the

Table of Contents

occurrence and continuance of an event of default, K2HV may declare all outstanding obligations immediately due and payable and take such other actions as set forth in the Loan Agreement. Any declaration of an event of default could significantly harm our business and prospects and could cause the price of our common stock to decline. If we are liquidated, the rights of our lenders to repayment would be senior to the rights of the holders of our common stock to receive any proceeds from the liquidation. We may not have enough available cash or be able to raise additional funds through equity or debt financings to repay these outstanding obligations at the time any event of default occurs. Further, if we raise any additional capital through debt financing, the terms of such additional debt could further restrict our operating and financial flexibility.

We are exposed to interest rate risk under our Loan Agreement with K2HV, which could cause our debt service obligations to increase significantly.

We are exposed to market risk from changes in interest rates. Under the Loan Agreement with K2HV, our term loan facility bears a variable interest rate equal to the greater of (i) 9.65% and (ii) the sum of (A) the prime rate last quoted in The Wall Street Journal and (B) 1.15%. An increase in interest rates by the Federal Reserve could cause the prime rate to increase, which could increase our debt service obligations. Significant increases in such obligations could have a negative impact on our financial position or operating results, including cash available for servicing our indebtedness, or result in increased borrowing costs in the future.

Risks Related to the Development of our Product Candidates

We are substantially dependent on the success of sabirnetug, our sole product candidate, which will require significant clinical testing before we can seek regulatory approval and potentially launch commercial sales, and which may not be successful in clinical trials, receive regulatory approval or be successfully commercialized, even if approved.

We are early in our development efforts. To date, we have invested substantially all of our efforts and financial resources in the research and development and clinical trials of sabirnetug, which is currently our only product candidate. Before seeking marketing approval from regulatory authorities for the sale of sabirnetug, or any other product candidate we may develop, we must conduct extensive clinical trials to demonstrate the safety and efficacy of the drug in humans. We are not permitted to market or promote any product candidate before we receive regulatory approval from the FDA, or comparable foreign regulatory authorities, and we may never receive such regulatory approval. We cannot be certain that sabirnetug will be successful in clinical trials. Further, sabirnetug may not receive regulatory approval even if it is successful in clinical trials. If we do not receive regulatory approvals for sabirnetug, we may not be able to continue our operations. Our prospects, including our ability to finance our operations and generate revenue, will depend entirely on the successful development, regulatory approval and commercialization of sabirnetug by us or by one or more of our partners. The clinical and commercial success of sabirnetug will depend on a number of factors, including the following:

•successful completion of ALTITUDE-AD and other clinical trials of sabirnetug;

•sufficiency of our financial and other resources to complete the necessary clinical trials;

•the results from ALTITUDE-AD and future clinical trials of sabirnetug;

•the frequency and severity of adverse effects related to sabirnetug;

•the ability of third-party manufacturers to manufacture supplies of sabirnetug and to develop, validate and maintain a commercial-scale manufacturing process that is compliant with current good manufacturing practices, or cGMPs;

•our ability to demonstrate sabirnetug’s safety and efficacy to the satisfaction of the FDA, EMA and any foreign regulatory authorities in order to receive necessary marketing approvals for sabirnetug;

•whether we are required by the FDA, EMA or other regulatory authorities to conduct additional clinical trials prior to the approval to market sabirnetug and whether the FDA, EMA or other regulatory authorities may disagree with the number, design, endpoints, size, conduct, implementation or other aspects of our clinical trials;

•whether the FDA, EMA or other regulatory authorities may require implementation of a Risk Evaluation and Mitigation Strategy, or REMS, as a condition of approval or post-approval;

•our ability to successfully commercialize sabirnetug, if approved for marketing and sale by the FDA, EMA or foreign regulatory authorities, whether alone or in collaboration with others;

•our success in educating physicians and patients about the benefits, administration and use of sabirnetug;

Table of Contents

•acceptance of sabirnetug as safe and effective by patients and the medical community;

•the availability, perceived advantages, relative cost, relative safety and relative efficacy of alternative and competing treatments;

•our ability to achieve and maintain compliance with all regulatory requirements applicable to sabirnetug, including any required post-marketing approval commitments;

•effectively competing with other AD therapies;

•the effectiveness of our own or any future collaborators’ marketing, pricing, coverage and reimbursement, sales and distribution strategies and operations;

•our ability to maintain our existing patents and obtain newly issued patents that cover sabirnetug and to enforce such patents and other intellectual property rights in and to sabirnetug;

•our ability to avoid third-party intellectual property claims;

•the availability of third-party coverage and adequate reimbursement for sabirnetug and any other product candidates, once approved; and

•a continued acceptable safety, tolerability and efficacy profile of sabirnetug following approval.

Many of these factors are beyond our control. Accordingly, we cannot assure you that we will ever be able to generate revenue through the sale of sabirnetug. If we are not successful in commercializing sabirnetug, or are significantly delayed in doing so, our business will be materially harmed.

The FDA granted Fast Track designation for sabirnetug for the treatment of early AD, and we may seek Fast Track designation for other product candidates. Even if received, Fast Track designation may not actually lead to a faster review or approval process and does not increase the likelihood that our product candidates will receive marketing approval.

The FDA granted Fast Track designation for sabirnetug for the treatment of early AD in October 2022, and we may in the future seek Fast Track designation for any other product candidates we may develop. If a drug or biologic is intended for the treatment of a serious or life-threatening condition and the product demonstrates the potential to address unmet medical needs for this condition, the sponsor may apply for FDA Fast Track designation for a particular indication. There is no assurance that the FDA will grant this status to any of our other product candidates. If granted, Fast Track designation makes a product eligible for more frequent interactions with FDA to discuss the development plan and clinical trial design, as well as rolling review of the application, which means that the company can submit completed sections of its marketing application for review prior to completion of the entire submission. Marketing applications of product candidates with Fast Track designation may qualify for priority review under the policies and procedures offered by the FDA, but the Fast Track designation does not assure any such qualification or ultimate marketing approval by the FDA. The FDA has broad discretion to decide whether to grant Fast Track designation, so even if we believe a particular product candidate is eligible for this designation, there can be no assurance that the FDA would decide to grant it. Even if we do receive Fast Track designation, we may not experience a faster development, review or approval process compared to conventional FDA procedures. In addition, the FDA may withdraw Fast Track designation at any time if it believes that the designation is no longer supported by data from our clinical development program.

We have concentrated our research and development efforts on the treatment of AD, a field that has to date seen very limited success in drug development.

We have focused our research and development efforts solely on developing effective treatments for AD. Collectively, efforts by pharmaceutical companies in the field of AD have seen limited successes in drug development. There are few approved products available for patients with AD.

Our future success is highly dependent on the successful development of sabirnetug for treating AD. The development and, if approved, commercialization of sabirnetug subjects us to a number of challenges, including ensuring that we select an effective dose and delivery mechanism of sabirnetug, executing appropriate clinical trials to test for safety and efficacy and obtaining regulatory approval from the FDA and other regulatory authorities. We cannot be sure that sabirnetug, or any other product candidate we develop, will ultimately prove to be safe and effective, scalable or profitable. Moreover, public perception of drug safety issues, including adoption of new therapeutics or novel approaches to treatment, may adversely influence the willingness of subjects to participate in clinical trials, or if approved, the willingness of physicians to prescribe novel treatments.

Table of Contents

Our approach to the potential treatment of AD is based on a novel therapeutic approach, which exposes us to unforeseen risks.

There is no current scientific or general consensus on the causation of AD or method of action to treat AD. We have discovered and are developing sabirnetug, a humanized monoclonal antibody that selectively targets amyloid-beta oligomers, or AßOs, to treat AD. Our approach is based on research on AßOs, globular assemblies of the amyloid-beta, or Aß, peptide that are distinct from other forms of amyloid. AßOs have gained increasing scientific acceptance as a primary toxin involved in the initiation and propagation of AD pathology. Based on the results of our nonclinical studies to date and our INTERCEPT-AD Phase 1 clinical trial, we believe sabirnetug represents a differentiated approach from current and prior anti-Aß/plaque immunotherapies because of its selectivity for soluble AßOs. We believe that sabirnetug is the most advanced immunotherapy candidate in development that was designed to selectively target AßOs. However, we may ultimately discover that sabirnetug does not possess properties required for therapeutic effectiveness. We may spend substantial funds attempting to develop sabirnetug or other product candidates and never succeed in doing so.

ABOS US Equity

ABOS · 10-K · period ended 2025-12-31

Item 1. Business.

Item 1A. Risk Factors.

ABOS US Equity☆

ABOS · 10-K · period ended 2025-12-31

Item 1. Business.

Item 1A. Risk Factors.

ABOS US Equity