10-K

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

FOR THE FISCAL YEAR ENDED DECEMBER 31, 2021

FOR THE TRANSITION PERIOD FROM

Commission file number: 001-40551

Acumen Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

State or other jurisdiction of (I.R.S. Employer

incorporation or organization Identification No.)

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code (434) 297-1000

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

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

Common stock, par value $0.0001 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. ☐ Yes ☒ No

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act. ☐ Yes ☒ No

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. ☒ Yes ☐ 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 (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). ☒ Yes ☐ 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 ☐ Accelerated filer ☐

Non-accelerated filer ☒ Smaller reporting company ☒

Emerging growth company ☒

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. ☐

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. ☐

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

The registrant was not a public company as of the last business day of its most recently completed second fiscal quarter and therefore cannot calculate the aggregate market value of its voting and non-voting common equity held by non-affiliates as of such date. The registrant’s common stock began trading on the Nasdaq Global Select Market on July 1, 2021.

The number of the registrant’s shares of common stock outstanding as of March 25, 2022 was 40,473,270.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive proxy statement relating to its 2022 annual meeting of the shareholders (the “2022 Proxy Statement”) are incorporated by reference into Part III of this Annual Report on Form 10-K where indicated. The 2022 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.

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TABLE OF CONTENTS

Page

PART I

ITEM 1. BUSINESS 1

ITEM 1A. RISK FACTORS 39

ITEM 1B. UNRESOLVED STAFF COMMENTS 100

ITEM 2. PROPERTIES 100

ITEM 3. LEGAL PROCEEDINGS 100

ITEM 4. MINE SAFETY DISCLOSURES 100

PART II.

ITEM 6. [RESERVED] 101

ITEM 7A. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK 113

ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA 114

ITEM 9A. CONTROLS AND PROCEDURES 141

ITEM 9B. OTHER INFORMATION 142

ITEM 9C. DISCLOSURE REGARDING FOREIGN JURISDICTIONS THAT PREVENT INSPECTIONS 143

PART III

ITEM 10. DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE 144

ITEM 11. EXECUTIVE COMPENSATION 144

ITEM 14. PRINCIPAL ACCOUNTING FEES AND SERVICES 144

PART IV.

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES. 145

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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:

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

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

• potential claims relating to our intellectual property;

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• our financial performance;

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 (www.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.

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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:

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PART I

Item 1. Business.

Overview

We are a clinical-stage biopharmaceutical company developing a novel disease-modifying approach to target 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. 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, ACU193, through clinical proof of mechanism trials in early AD patients. ACU193 is a humanized monoclonal antibody, or mAb, that selectively targets 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 models for AD.

ACU193 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. ACU193’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.

In our nonclinical studies, we observed that ACU193 has over 500-fold greater selectivity for targeting AOßs over Aß monomers and has limited or no binding to amyloid plaques. Also, ACU193 potently prevents binding of AßOs to hippocampal neurons. Recent laboratory studies conducted by us and others suggest that inhibiting AßOs may enable damaged brain circuits to regain some function and prevent further degeneration from occurring. ACU193 has demonstrated in vivo biochemical and behavioral activity in several AD mouse models, including crossing the blood-brain barrier and forming complexes with AßOs in a dose-dependent manner. ACU193 has shown consistent pharmacokinetics and brain penetration properties in four animal species. Safety toxicology studies in rats and monkeys provide acceptable margins for dosing in the clinic. Additionally, studies in transgenic mice indicate low potential for microhemorrhage. Based in part on its binding selectivity for AßOs rather than amyloid plaques, ACU193 has the potential to have a lower rate of amyloid-related imaging abnormalities, or ARIA, than the plaque-clearing anti-amyloid antibody therapies currently in development. ARIA is a common adverse event for antibodies targeting amyloid plaque and can be a dose-limiting safety liability for those antibodies.

We initiated a Phase 1 clinical trial of ACU193 in the second quarter of 2021, which we named “INTERCEPT-AD.” This trial is enrolling patients with mild dementia or mild cognitive impairment, or MCI, due to AD, conditions referred to as “early AD.” INTERCEPT-AD is 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 involving a total of approximately 62 patients with early AD. The overall objective of the trial is to evaluate the safety and tolerability, and establish clinical proof of mechanism of ACU193 administered intravenously. The primary trial endpoints are focused on safety and immunogenicity. An important safety measure will be the use of magnetic resonance imaging, or MRI, to assess the presence or absence of ARIA. Secondary endpoints include pharmacokinetics in plasma and cerebrospinal fluid, or CSF, and target engagement as evidenced by detection of ACU193 bound to AßOs in CSF. Clinical scales typically used in AD trials as well as computerized cognitive testing are included as exploratory measures. In October 2021, we announced the initial dosing of the first patient in the INTERCEPT-AD trial and the subsequent successful sentinel safety review of the first two patients.

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Due to delays in clinical trial site activation and patient enrollment that we believe are principally related to effects of the COVID-19 pandemic, we are expanding the anticipated number of trial sites to support our enrollment objectives and anticipated timelines. Clinical trial site activation and patient recruitment and enrollment is ongoing. At present, INTERCEPT-AD is in the SAD portion of the trial. Based on current site activations and enrollment rates, we anticipate reporting our topline data from this trial in the first half of 2023.

Alzheimer’s disease currently affects over 6 million people in the United States and approximately 32 million people worldwide and is the sixth-leading cause of death in the United States. However, due to the aging population, patient populations in the United States impacted by AD are expected to triple 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 exceed $1 trillion.

Until June 2021, the four approved medications for AD provided only modest improvement in AD symptoms. In June 2021, the FDA granted approval for Biogen’s Aduhelm (aducanumab) under the FDA’s Accelerated Approval Pathway. Aduhelm is the first new AD product approval since 2004 and the first and only approved disease-modifying product. The FDA decision to approve Aduhelm has stirred significant controversy among various stakeholders. In January 2022, the Centers for Medicare and Medicaid Services, or CMS, published a draft guidance opinion for a National Coverage Decision, or NCD, that took the position that Aduhelm should receive reimbursement under a Coverage with Evidence Development, or CED, designation which would limit reimbursement to use of Aduhelm in the context of placebo controlled clinical trials. The need for a medical breakthrough in AD treatment and prevention becomes more urgent with each passing year, and we believe that our novel approach can potentially help address this pressing need.

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. 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, or amyloid plaques, which in turn contribute to the formation of intracellular neurofibrillary tangles composed of the tau protein and cause inflammation, ultimately leading to neuronal cell loss and progressive dementia. The primary constituent of amyloid plaques is the Aß peptide, although other proteins are present to lesser degrees.

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 monoclonal antibodies 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. Several of these antibodies are currently in late-stage development, one having recently received regulatory approval, and collectively they have provided a biological foothold for treating AD. However, the clinical data available to date 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 propose that amyloid accumulation 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 peptide), amyloid plaques (insoluble fibrillar Aß), and soluble AßOs (dimers and up to 200-mers). The more recent appreciation of the crucial role of AßOs in the pathologic process is the central tenet of our therapeutic approach.

Our therapeutic approach focuses on targeting AßOs, which we believe are the most toxic and pathogenic form of Aß relative to Aß monomers and amyloid plaques. Growing evidence, spurred by advances in AD research and analytic techniques, supports our view that AßOs are the main instigators of AD neurodegeneration. AßOs have been observed to be potent neurotoxins that cause both acute synaptic toxicity and induce

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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 the most promising approach for the treatment of AD, which led us to discover and develop ACU193.

Our Product Candidate

Our product candidate, ACU193, is a humanized monoclonal antibody that targets soluble AßOs. We are developing ACU193 for intravenous, or IV, administration every four weeks for the treatment of early AD. We believe that ACU193 represents a differentiated approach from current and prior anti-Aß/plaque immunotherapies because it is highly selective for soluble AßOs. ACU193 has a nanomolar affinity for AßOs, over 500-fold greater selectivity for AßOs over Aß monomers, and limited or no binding to dense core amyloid plaques. We believe ACU193 is the most advanced immunotherapy candidate in development that selectively targets AßOs.

We believe ACU193 has characteristics that make it a promising potential treatment for AD relative to other antibodies that do not selectively target AßOs. ACU193 is engineered to reduce immune effector function signaling and to avoid binding to vascular amyloid plaques, which we expect will reduce the incidence of ARIA observed with amyloid plaque-targeting immunotherapies approved and in development for AD. We are currently assessing ACU193 in INTERCEPT-AD, a proof of mechanism Phase 1 clinical trial involving early AD patients, which we expect to follow with an adaptive Phase 2/3 clinical trial as soon as late 2023 if INTERCEPT-AD is successful.

Summary of Clinical Development Plan

We are currently conducting INTERCEPT-AD, a U.S.-based, multi-center, randomized, placebo-controlled, single and multiple ascending dose Phase 1 clinical trial of ACU193 in patients with early AD. The early AD patient group is comprised of individuals who have mild dementia or MCI due to AD, and our trial excludes patients with moderate to severe AD dementia. We plan to enroll a total of 62 early AD patients across seven cohorts, consisting of a single ascending dose in Part A (32 participants) and an overlapping multiple ascending dose in Part B (30 participants). Part A will contain Cohorts 1 through 4; each cohort will receive a single IV dose between 2mg/kg and 60 mg/kg, or placebo. Part B will contain Cohorts 5 through 7; each cohort will receive a total of three doses of ACU193 or placebo as follows: 10 mg/kg every four weeks (Q4W), 60 mg/kg Q4W, or 60 mg/kg every two weeks (Q2W).

The main objective of INTERCEPT-AD is to evaluate the safety, tolerability, pharmacokinetics, pharmacodynamics, and target engagement of single and multiple ascending doses of ACU193 administered by intravenous infusions. Exploratory outcomes will include cognitive scales and computerized cognitive testing. Our goal is to establish clinical proof of mechanism of ACU193 in early AD patients in order to enable rapid progression into an adaptive Phase 2/3 clinical trial. In October 2021, we announced the initial dosing of the first patient in the INTERCEPT-AD trial and the subsequent successful sentinel safety review of the first two patients. Due to delays in clinical trial site activation and patient enrollment that we believe are principally related to effects of the COVID-19 pandemic, we are expanding the anticipated number of trial sites to support our enrollment objectives and anticipated timelines. Clinical trial site activation and patient recruitment and enrollment is ongoing. At present, INTERCEPT-AD is in the SAD portion of the trial. Based on current site activations and enrollment rates, we anticipate reporting our topline data from this trial in the first half of 2023. Following, and subject to the results of, INTERCEPT-AD, we plan to engage with the FDA in an end-of-Phase 2 meeting, which we anticipate will occur in the second half of 2023, to discuss the Phase 2/3 clinical trial design and pathway for potential approval.

Summary of Our Nonclinical Data

In nonclinical studies, ACU193 has demonstrated promising characteristics that indicate its potential to inhibit AßOs as a possible therapeutic treatment of AD. ACU193 has high selectivity, with over 500-fold binding

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selectivity for AßOs compared to Aß monomers and has limited or no binding to amyloid plaques. ACU193 binds to a broad spectrum of small to large soluble AßOs. Additionally, ACU193 has been shown to offer protection from synaptic toxicity by inhibiting binding of AßOs to primary hippocampal neurons. ACU193 has also demonstrated suitable in vivo pharmacology, target engagement, blood-brain barrier penetration and reduction of behavioral deficits. Based on nonclinical studies, AßO target engagement has the potential to be achieved at doses of ACU193 that will be tested in our Phase 1 clinical trial. Lastly, ACU193 has been shown to have an adequate safety margin in Good Laboratory Practice, or GLP, toxicity studies conducted in two animal species. We believe these data indicate that ACU193 has the potential to offer patients a reduction in cognitive decline.

Our Strategy

Our objective is to transform the treatment of AD, and potentially other diseases, by developing innovative therapeutics that target primary drivers of disease pathology. Our initial therapeutic approach is focused on inhibiting and reducing the toxic activity of AßOs, which may allow for synaptic protection and decreased neurodegeneration, leading to more effective treatment for patients with early AD. To achieve this objective, we are pursuing the following strategies:

Impact of AD

AD represents a significant unmet medical need. AD is a progressive neurodegenerative disease that destroys memory and other important cognitive functions and ultimately leads to patient death. AD is the sixth-leading cause of death in the United States. The disease afflicts more than six million people in the United States and more than 32 million people worldwide, and the patient population in the United States is expected to grow to approximately 13 million people in the United States by 2050. AD can have a significant burden on family and

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caretakers. In 2020, these caregivers provided an estimated 15.3 billion hours of care valued at nearly $257 billion. The direct costs of caring for individuals with AD and other dementias in the United States were expected to total $355 billion in 2021, and are projected to increase to $1.1 trillion by 2050, according to the Alzheimer’s Association.

Therapeutic Approaches to AD

The development of effective therapeutics addressing the underlying cause of AD is one of the greatest medical challenges facing society. Existing treatments for AD consist of drugs that provide modest improvements in symptoms but have no impact on the underlying disease and are unable to halt or slow disease progression. 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 hypothesis was more firmly established when a series of genetic mutations causing the disease were discovered in the early to mid-1990s. These mutations were found in genes coding for APP or in genes coding for one of the enzymes which cleaves APP, creating the Aß peptide.

Available Treatments: Symptomatic Treatments

Currently available symptomatic treatments include memantine, an N-methyl-D-aspartate receptor antagonist, and cholinesterase inhibitors, a class of drugs that block the normal breakdown of acetylcholine. The first approved cholinesterase inhibitor, tacrine, was approved in 1993, but was later withdrawn from the market due to liver toxicity. Three other cholinesterase inhibitors were subsequently approved and continue to be used clinically. Memantine is the most recently approved symptomatic treatment drug for AD in 2003 and is indicated for use in moderate to severe AD patients.

Potential Disease-Modifying Approaches focusing on Aß

Because of the lack of significant improvement provided by these symptomatic drugs, there remains a significant need for therapies that target underlying disease pathology and potentially slow or halt disease progression. Based on the strong linkage between Aß and AD pathology established by decades of research, a range of treatment modalities focusing on Aß have been explored as potential disease-modifying treatments, including

-secretase

inhibitors, ß-site APP-cleaving enzyme, or BACE, inhibitors and monoclonal antibodies.

Initial attempts at disease modification were made using small molecule

-secretase inhibitors and BACE inhibitors, each of which inhibited a different enzyme necessary to produce the Aß peptide. The first Phase 3 clinical trial results from a

-secretase inhibitor, semagacestat, were reported in 2010 and unexpectedly showed modest cognitive worsening. Development of the other

-secretase inhibitor, avagacestat, was also stopped due to cognitive worsening observed in the clinic. At least four BACE inhibitors have reached clinical trials; however, during 2018 and 2019, Phase 3 clinical trial results for many BACE inhibitors, including verubecestat and elenbecestat, also unexpectedly showed modest clinical worsening.

A third class of potential disease-modifying agents, monoclonal antibodies, or mAbs, have targeted Aß monomers or amyloid plaques. Some of these monoclonal antibodies, such as solanezumab (an Eli Lilly product), target Aß monomers, while others, such as Aduhelm (aducanumab) (a Biogen product), target deposited amyloid plaque, and these monoclonal antibodies have been evaluated in Phase 2 and Phase 3 trials over the period from 2012 to 2021. The most advanced monoclonal antibody for the treatment of AD is Aduhelm (aducanumab), which received Food and Drug Administration, or FDA, approval in June 2021 under the FDA’s Accelerated Approval Pathway. As shown in Table 1 below, several of these antibodies have demonstrated some degree of slowing of disease progression in clinical trials, as measured by customary assessments of cognition and function.

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Table 1: Percent Slowing of Cognitive/Functional Decline*

iADRS -11 % N.A. N.A. N.A. -32 %

** ADAS-cog: Alzheimer’s Disease Assessment Scale – Cognitive Subscale

ADCS-ADL: Alzheimer’s Disease Cooperative Study – Activities of Daily Living

CDR-SB: Clinical Dementia Rating – Sum of Boxes

MMSE: Mini-Mental State Examination

iADRS: Integrated Alzheimer’s Disease Rating Scale

A potential limitation of the amyloid plaque-targeting antibodies under development is an adverse effect known as ARIA. ARIA has two different forms, ARIA-E, or cerebral edema, formerly called vasogenic edema, and ARIA-H, or cerebral microhemorrhages. While the mechanism of ARIA is not known with certainty, the prevailing theory is that ARIAs are related to the presence of amyloid plaques around blood vessels in the vast majority of people with AD, a condition known as cerebral amyloid angiopathy. It is generally believed that the removal of these amyloid plaques by the antibody can result in small hemorrhages, or ARIA-H. ARIA-H occurs in individuals with untreated AD and its occurrence is increased in individuals treated with antibodies that target amyloid plaques. Increased ARIA-H is correlated with worsening cognition. In contrast to ARIA-H, ARIA-E is hypothesized to result from the leakage of fluid from the blood vessels into the interstitial spaces in the brain, causing edema, or ARIA-E. ARIA-E, in particular, is sometimes associated with symptoms that include worsening of cognition, headache, and gait disturbance, which can be severe enough to lead to hospitalization. ARIA-E usually resolves weeks to months following the cessation of treatment. In clinical trials for anti-Aß/plaque mAbs, surveillance MRI scans are required to detect asymptomatic ARIA. Table 2 below illustrates the rates of ARIA observed in Phase 2 or 3 studies for the most advanced mAbs. Given observed rates of ARIA, from approximately 10% to over 40%, we believe that MRI scans to assess for ARIA are likely to be required in clinical practice for any amyloid plaque-targeting monoclonal antibody that receives regulatory approval.

Table 2: Percent of ARIA Events for Anti-A

ß/plaque mAbs*

Targeting AßMonomers Targeting Amyloid Plaques

PC Treated PC Low High PC Low High PC High PC Treated

PC = Placebo, Low = Low Dose; High = High Dose

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Table 3: AD Product Candidates and Target Selectivity and ARIA Profile

Target Selectivity+ ARIAProfile

Product Candidate Amyloidplaque Aßfibrils Aßmonomers Aßoligomers LackofARIA

ACU193 x untested x ✓ ✓

Aduhelm aducanumab ✓ ✓ x ✓ x

lecanemab BAN2401 ✓ ✓ x ✓ x

gantenerumab ✓ ✓ x ✓ x

donanemab ✓ untested x x x

solanezumab* x x ✓ x ✓

crenezumab* ✓ ✓ ✓ ✓ ✓

bapineuzumab* ✓ ✓ ✓ ✓ x

* Phase 3 discontinued for primary AD indication

Additional Treatment Modalities

While Aß and amyloid are generally considered to be the proximal cause 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.

Potential Combination Approaches

The pathology of AD is complex, and many experts in the field expect that combination therapy using drugs with different mechanisms of action, such as tau-based therapies and immune inflammatory modulation, will ultimately prove most successful, similar to cutting edge approaches used in oncology. We believe that a drug targeting AßOs will likely be an important component of a combination treatment. In addition, because symptomatic treatments, such as memantine and cholinesterase inhibitors, affect neurotransmitter systems rather than the underlying AD pathology, we believe that it is likely that they will be used together with disease-modifying treatments.

Growing Interest in the Anti-AßO Hypothesis and AßOs as a Drug Target for AD

An important refinement of the amyloid hypothesis is the recognition that at least three pools of Aß species exist in vivo—Aß monomers, AßOs, and amyloid plaques. Because these pools exist in equilibria, manipulation of one pool may have indirect effects on other pools. For example, reduction of Aß monomers may reduce AßOs to some degree. Limited successes in the clinic have been demonstrated with antibodies targeting Aß monomers, even though Aß monomers themselves are not widely accepted to have toxic properties. Similarly, limited successes in the clinic have been demonstrated using antibodies that target amyloid plaques, although insoluble fibrillar Aß and ß-amyloid plaques exhibit relatively low in vitro toxicity and may even serve as an in vivo mechanism for removal of the more toxic soluble Aß species. Both Aß monomers and amyloid plaques can act as sources of AßOs. The positive results of monoclonal antibodies targeting Aß monomers and amyloid plaques, even in the absence of targeting AßOs directly, support the significance of Aß and amyloid in AD and have led to a growing confidence in the field in the amyloid hypothesis broadly. In contrast to the non-toxic Aß monomers

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and relatively non-toxic amyloid plaques, AßOs are known to bind to neurons, causing synaptic dysfunction and possibly contributing to cognitive impairment, neurodegeneration and cell death. As a result, AßOs are now generally believed to be the most toxic form of Aß. The acute synaptic and chronic neurodegenerative toxicity of AßOs, coupled with their very low in vivo levels, suggests that they may be an optimal therapeutic target compared to Aß monomers and fibrillar Aß species. Therefore, we believe that drugs that directly target AßOs could represent a promising new approach to the potential treatment of AD.

Figure 1: A

ß related species and pathophysiology of AD

The precise mechanism of toxicity of AßOs is not fully understood, however numerous studies suggest a mechanism that may include initial reversible memory loss caused by acute AßO-induced disruptions of synaptic plasticity, with progressive dementia attributable, at least in part, to neuronal degeneration induced by chronic exposure to AßOs. AßOs bind to synapses on hippocampal and cortical neurons. In rodent hippocampal slice preparations, AßOs cause rapid inhibition of long-term potentiation, or LTP, and direct injection of AßO solutions into rodent brains leads to reversible impairment of cognitive function. These findings support the view that AßOs may interfere acutely with normal synaptic functions and contribute significantly to the memory loss and cognitive dysfunction characteristic of AD. With regard to neurodegeneration, binding of AßOs to neurons also causes damage within neurons, such as calcium influx and the hyperphosphorylation of tau, which leads to neurofibrillary tangles, another downstream hallmark of AD pathology.

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Our Differentiated Approach to the Treatment of AD

We believe that, based on its differentiated mechanism of action, potential for symptomatic improvement and disease modification, and potential for higher dosing, ACU193 has several potential advantages in comparison to other AD drugs that are currently approved or in development:

Differentiated mechanism of action:

Potential for symptomatic improvement and disease modification:

Potential for higher dosing:

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ACU193: First AD Immunotherapy Candidate to Selectively Target A

ßOs

Our product candidate, ACU193, is a humanized, affinity-matured, immunoglobulin G2m4, or IgG2m4, subclass monoclonal antibody, derived from the murine immunoglobulin G1, or IgG1, parent, ACU3B3. ACU193 lacks the inflammatory effector functions of other IgG subclasses. ACU193 binds with high selectivity to soluble AßOs (over 500-fold versus Aß monomer in a competitive assay), differentiating ACU193 from other therapeutic monoclonal antibodies, which primarily bind Aß monomers or fibrillar forms of Aß. Binding of ACU193 to AßOs may improve synaptic function and decrease neurodegeneration.

Figure 2: Summary comparison of ACU193 to anti-A

ß/plaque antibodies in clinical development

Despite recognition that AßOs are key structures contributing to AD memory dysfunction, cognitive deficits, and neurodegeneration, drug discovery efforts targeting these species have been hampered by technical difficulties of generating physiologically relevant preparations of synthetic AßOs, or syn-AßOs. Our founders and early-stage researchers were instrumental in the development of well-characterized preparations of syn-AßOs, initially termed Aß Derived Diffusible Ligands, or ADDLs. ADDL preparations were used as the immunogen to generate and discover ACU3B3, the murine IgG1 parent of ACU193.

In December 2003, we entered into an exclusive license and research and development collaboration agreement with Merck for the research, discovery, development, and commercialization of immunotherapies for AD. From 2003 to 2011, Merck carried out extensive research leading to the humanization of ACU3B3 and creation of ACU193. ACU193 emerged as the lead product candidate based on its preferential AßO binding, favorable immunogenicity profile, and an absence of off-target binding. In 2011, Merck chose to terminate the program largely based on internal strategic priorities. Consequently, we regained an exclusive, perpetual, irrevocable, royalty-free, worldwide license for the research, development, manufacturing or commercialization of ADDL antibodies, ADDL antigens, or products, including ACU193.

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Product Profile

We are developing ACU193, a humanized monoclonal antibody targeting soluble AßOs, as an IV administered treatment for early AD patients. The early AD population is defined as individuals with clinical symptoms consistent with MCI, or consistent with mild dementia who have demonstrated amyloid pathology as assessed with either a positron emission tomography, or PET, or cerebrospinal fluid analysis. A blood test to determine amyloid status may become available in the future. We believe ACU193 has the potential to reduce the rate of cognitive decline by at least 35%, which would be broadly considered as clinically meaningful.

ACU193 is a humanized, affinity-matured, mAb with high selectivity for toxic AßOs versus Aß monomers (greater than 500-fold) and amyloid plaques. With its selective targeting of AßOs, we believe that ACU193 could demonstrate a number of potential valuable clinical outcomes, including the slowing of disease progression and downstream changes in tau and neurofibrillary tangles. Additionally, given the acute toxicity of AßOs in laboratory studies, we believe that some patients could experience an improvement in cognitive function. ACU193’s epitope is composed of a configuration of the N-terminal regions of Aß monomers within AßOs. AßOs form when Aß monomers associate co-linearly along the central alpha helical domains through C-terminal regions via stacking phenylalanine polar bonding associations. This presents an advantage for ACU193 binding because the co-linear association sterically restricts spatial configuration of the N-terminal regions presented by AßOs. The N-termini within AßOs are anionic and repel one another, resulting in presentation of N-terminal amino acids, which lead to high affinity for ACU193 binding.

In its current formulation, ACU193 deamidates at physiological pH and body temperature. The rate of deamidation is specific to the matrix and temperature, and results in reduced target binding. To prevent deamidation prior to administration of ACU193 in the clinic, the current drug product is stored frozen at -20°C.

ACU193 is an IgG2m4 subclass mAb which lacks the inflammatory effector function signaling stimulated by other IgG subclasses. The product is expected to be given as an IV infusion once every four weeks. Given the indication, ACU193 treatment would be initiated for patients diagnosed with mild dementia or MCI and would likely be continued for several years. Based on the target and lack of inflammatory effector function, we believe the rate of ARIA may be reduced compared to approaches targeting amyloid plaques. Finally, ACU193 could be used in combination with other therapies that might become available for AD, especially those targeting the tau protein or modulating the immune system.

Nonclinical Data Package

Summary of Nonclinical Studies

In our nonclinical studies, ACU193 has demonstrated: (i) preferential selectivity for binding to AßOs versus other forms of Aß monomers and amyloid plaques in in vitro assays, human AD tissue samples and in vivo transgenic mouse models; (ii) consistent data in support of ACU193 protective effects against AßO synaptic toxicity in in vitro and ex vivo assays; (iii) in vivo pharmacology in multiple species confirming blood-brain barrier penetration, target engagement, and behavioral effects; and (iv) safety data in multiple species including GLP toxicology studies in Sprague-Dawley rats and cynomolgus monkeys confirming an adequate safety margin for the first in human clinical trial. Based on the strength of the data we observed in our nonclinical studies, we initiated INTERCEPT-AD, a Phase 1 clinical trial, in the second quarter of 2021.

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Key Characteristics and Data

Selectivity for AßOs

In order to understand ACU193 selectivity for AßOs, we performed biochemical assays and immunohistochemistry experiments.

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Selectivity for AßOs versus Aß monomers

We demonstrated that ACU193 shows significant preferential selectivity for AßOs compared to Aß monomers. In a competition ELISA assay, ACU193’s binding to AßOs was 556-fold greater than binding to Aß monomers. Figure 3A shows comparative syn-AßO versus Aß monomer affinity data for ACU193, and illustrates the high selectivity of ACU193 for AßOs. Further evidence of ACU193 selectivity for syn-AßOs was obtained using a very high concentration of monomeric Aß, 5 μm, which did not decrease binding to syn-AßOs (Figure 3B). We believe ACU193’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, ACU193 does not experience “target distraction” from non-toxic Aß monomers in an environment simulating brain interstitial fluid.

Figure 3: [A] Competitive ELISA for ACU193 binding to syn-A

ßO or monomeric A

ß40 [B] 5μM monomeric A

ß did not substantially change binding to syn-A

ßO

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These results support the conclusion that selectivity of ACU193 for AßOs is maintained in a biochemical environment simulating the brain.

Selectivity for AßOs versus amyloid plaques

We have shown in our nonclinical data that ACU193 binds AßOs from AD patients with limited or no binding to amyloid plaques. In Figure 4 below, thioflavin S-positive ß-amyloid plaques are shown in green fluorescence while ACU193 binding is shown in red fluorescence. ACU193 binds significantly in regions that are thioflavin-S-negative, i.e., without amyloid plaques (Figure 4, Panels B and E), but only infrequently and minimally binds to thioflavin-S-positive fibrillar Aß structures (Figure 4, Panel D); close examination shows possible co-localization of ACU193 with thioflavin-S-positive Aß deposits in their periphery (Figure 4, Panel F). We believe the most likely explanation of ACU193 infrequent binding near the periphery of some amyloid plaques is due to binding to AßOs that surround the periphery of amyloid plaques. Taken together, these results are consistent with the concept that ACU193 binds endogenous AßOs, does not block binding by thioflavin-S, and, importantly, preferentially binds AßOs versus fibrillar Aß.

Figure 4: ACU193 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, A) there is substantial binding by ACU193 (red fluorescence staining, B) that is not related to amyloid plaque. The merge of these panels (Panel E) shows ACU193 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, C) shows minimal ACU193 binding (red fluorescence staining, D). The merge of these panels (F) shows the minimal binding of ACU193 (red fluorescence staining) on the periphery of the amyloid plaque (green fluorescence staining), most likely related to AßO binding in the halo of the amyloid plaque.

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Figure 5: AD stages based on AD neuropathic change, or ADNC, scoring

ADNC scoring is a combination of amyloid plaque levels, neuritic plaque levels, and neurofibrillary tangle pathology, or NFT, levels (Braak stage). In human tissue samples, ACU193 shows a disease state-relevant signal based on immunohistochemistry shown on the left from aged controls, intermediate AD pathology, and advanced AD pathology. On the far-right panel, ACU193 detects AßOs in soluble hippocampal extracts from an autosomal dominant AD patient, but not from a cognitively normal patient.

Furthermore, we have demonstrated that ACU193 does not bind to amyloid plaque surrounding blood vessels (cerebral amyloid angiopathy). In a study of transgenic mice, we did not observe binding to vascular amyloid, in contrast to hu3D6 (bapineuzumab), which displayed significant binding at all dose levels.

Figure 6: ACU193 versus hu3D6 binding to vascular amyloids

ACU193 (A and C) shows no binding to the vascular amyloid that is visible in the vessels stained by thioflavin-S (green fluorescence, B and D) in the brain 24 hours following IV dosing of 10 or 50 mg/kg in seven- to eight-month-old Tg2576 mice. In contrast, hu3D6 (bapineuzumab) binds vascular amyloid (E) at all dose levels assessed.

The data above related to vascular plaque binding support our belief that ACU193 is unlikely to have an ARIA liability. Given that the amyloid plaque-binding properties of multiple antibodies have been associated with ARIA (e.g., aducanumab, lecenamab, gantenerumab, and donenamab), we believe that ACU193’s negligible binding of amyloid plaques, including amyloid plaques associated with cerebral amyloid angiopathy, provides evidence that ARIA is unlikely to be associated with ACU193.

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Binding to a broad spectrum of molecular weight AßOs

In addition, we demonstrated that ACU193 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 ACU193, hu3D6 (bapineuzumab) or hu266 (solanezumab) as the capture antibody and biotinylated anti-human Aß antibody 82E1 for detection. These data show ACU193 binds mid to higher molecular weight AßOs, with preferential binding to mid-molecular weight oligomers compared to hu266. This range of molecular weights is very similar to the range of molecular weights of oligomers thought to be most toxic.

Figure 7. Binding of humanized antibodies to size exclusion chromatography fractions of synthetic Aß species

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 ACU193 for oligomers versus monomers, and also demonstrate a range of oligomers that are bound by ACU193.

Collectively the data show that ACU193 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 other data, we believe that ACU193 can target therapeutically relevant AßOs in the brain of early AD patients.

Protection from AßO-induced synaptic toxicity

In order to understand ACU193’s ability to either neutralize or limit AßO-induced physiological changes, we performed ex vivo studies using brain slices or cell cultures.

Prevention of AßO toxic effects on neuronal electrophysiology

In ex vivo studies using the murine hippocampal slice long term potentiation, or LTP, model, pre-incubation with ACU193 or ACU3B3 has been shown to prevent the LTP deficit caused by AßOs (formed by administration of 50nM Aß

1-42

). LTP is an electrophysiological phenomenon demonstrated in neurons that may be associated with memory formation and other important neurological functions. Disruption of LTP has been associated with animal models in a variety of central nervous system disease states.

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Figure 8. Effects of ACU3B3 and ACU193 on A

ßO-induced change in LTP

Note that AßOs disrupted normal LTP findings, but that pre-incubation with ACU3B3 prevented that disruption.

Prevention of toxic effects of AßOs on calcium homeostasis

Exposure to ACU3B3 has been shown to prevent calcium overload in cortical neuronal cultures induced by direct application of syn-AßOs (Figure 9). Disruptions in calcium homeostasis that cause cellular dysfunction have been implicated in a number of disease states, including myocardial infarction and stroke. Further, AßOs have been shown to cause disruption of calcium homeostasis, and thus, restoration of intracellular calcium to normal levels could serve as a functional indicator of potential treatment effect in AD. Multiphoton microscopy was used to examine the relationship of syn-AßO and neuronal calcium homeostasis in vitro (Figure 9). Direct application of syn-AßOs elicited calcium elevations in cortical neuronal cultures. Prior exposure to antibodies ACU3B3 and 3D6 prevented this calcium elevation (Figure 9). These results demonstrate that syn-AßOs induce elevated concentrations of intracellular neuronal calcium and that ACU3B3 prevented the syn-AßO-induced calcium overload.

Figure 9: Effect of ACU3B3 on calcium homeostasis

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The relationship of syn-AßO and neuronal calcium homeostasis in the presence and absence of ACU3B3 was studied in primary cultures of transgenic APP-PS1 mouse cortical neurons. Multiphoton microscopy was used to obtain images of neuronal cultures at 12–14 days in vitro, or DIV, or 21 DIV. Cortical regions were identified and reimaged before and after topical applications of syn-AßOs to allow comparison of resting calcium within the same neuronal compartments. After baseline calcium was obtained, the cultures were treated with antibody-immunodepleted syn-AßOs (1 mL of 3 nM syn-AßOs with 9 μg of antibody) or syn-AßOs alone for 45 minutes. The cultures were then re-imaged in the same areas in the dish. Taken together, these studies show that ACU3B3 prevents the toxic effect of AßOs on calcium homeostasis.

In Vivo Pharmacology

In order to understand the effects of ACU193 in intact animals, we performed behavioral studies in transgenic mice with genetic alterations that overproduce a mutant amyloid precursor protein 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.

In vivo behavioral studies in multiple transgenic mouse models for AD

The behavioral studies described below, 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. The Phase 1 clinical trial includes doses in the range used in these nonclinical studies.

A study conducted at QPS and using nine- to ten-month-old APP/SL transgenic mice treated weekly with 20 mg/kg ACU3B3 for four weeks demonstrated statistically significant behavioral improvements in swim path length and swim speed during the water maze learning test (Figure 10).

Figure 10: Results of ACU3B3 treatment in mice study

ACU3B3 treatment in nine- to ten-month-old APPSL mice (n=10/group) improves performance on the first day of water maze training (A; p=0.057), decreases swim path length (B; p=0.034), and reverses a swim speed abnormality (C; p<0.02).

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In a separate study conducted at Stanford University, the hyperactivity phenotype of five- to seven-month-old Thy1-hAPP/SL transgenic mice in the open field and Y-maze tests was also significantly reduced after four to five weeks of treatment with ACU3B3 (20 and 30 mg/kg, weekly). Prior to dosing, Thy1-hAPP/SL mice showed increased activity in the activity chamber compared to wild-type mice. After treatment with ACU3B3, Thy1-hAPP/SL mice activity fell to a level comparable to wild-type mice, particularly activity in the center of the test arena (Figure 11A). Similar effects of ACU3B3 were found with changes in Y-maze behavior (Figure 11B) and passive avoidance (Figure 11C).

Figure 11: ACU3B3 treatment at 20 mg/kg in five- to seven-month-old Thy1-hAPP/SL mice (n=13-14/group, means + SEM)

[A] Open field total distance measurement, APP-Veh vs. APP-3B3, *p=0.029. [B] Y-maze arm entries, APP-Veh vs APP-3B3, *p=0.045; APP-Veh vs WT-Veh, **p=0.007. [C] Passive avoidance latency, APPSL-APP3B3 vs. APPSL-Veh trended for drug effect, but was not statistically significant.

In separate studies conducted at the Gladstone Institute in young three- to five-month-old hAPP/J20 mice, behavioral abnormalities in these mice were reduced after chronic treatment with ACU3B3. Treatment ameliorated the hyperactivity phenotype, emotional response alterations and procedural learning deficits in this mouse model and hyperactivity in the Y-maze test was reduced dose-dependently (5 < 10 = 20 mg/kg) (Figure 12).

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Figure 12: Open field and water-maze behavior in three- to five-month-old hAPP/J20 mice following repeat weekly IP dosing with ACU3B3 (n=13-14/group)

[A] Open field activity after four weekly doses. [B], [C] Water-maze behavior following eight weekly doses.

Figure 13: Y-maze and elevated plus-maze behavior in three- to five-month-old hAPP/J20 mice following repeat, weekly IP dosing with ACU3B3 (n=13-14/group)

[A] Y-maze activity after six weekly doses. [B], [C] Elevated plus-maze behavior following nine weekly doses.

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. The range of doses used in these nonclinical studies are expected to be covered in INTERCEPT-AD.

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Pharmacokinetics and Pharmacodynamics

ACU193 has demonstrated favorable pharmacokinetics and pharmacodynamics based on a number of nonclinical studies. ACU193 could be detected in plasma, CSF, and brain tissue of Tg2576 mice, rats, dogs, and rhesus monkeys following IV injection. Penetration of ACU193 into the brain was demonstrated by direct measurements of brain levels in Tg2576 mice, rats, and dogs, and by measurements of CSF levels in rats and rhesus monkeys. Brain levels were approximately 0.02% of plasma levels and CSF levels ranged from 0.05 to 0.15% of plasma levels, showing penetration of ACU193 into the brain. Toxicokinetic data collected as part of GLP toxicity studies in Sprague Dawley rats and cynomolgus monkeys showed clearance of 1 to 3 mL/h/kg and terminal half-life of approximately seven days.

Brain penetration and in vivo binding of ACU193 was explored in seven-month-old Tg2576 mice dosed intravenously with 2, 10 and 50 mg/kg of ACU193 or hu3D6 (bapineuzumab), and perfused brain tissue was collected 24 hours after dosing for analysis. A dose dependent increase in brain levels of ACU193 (Figure 14A) and ACU193/AßO complex (Figure 14B) was demonstrated, with a minimum effective dose for target engagement of 10 mg/kg.

Figure 14: Levels of ACU193 and AßO/ACU193 complexes in the brain 24 hours following IV dosing in seven-month-old Tg2576 mice (n = 4/cohort)

These results show ACU193 can penetrate the blood-brain barrier and bind endogenous AßOs.

Additionally, a study of pharmacokinetics 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 15, the concentrations of ACU193 in CSF should provide adequate target engagement with every four week dosing.

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Figure 15: Comparison of ACU193 levels in rhesus CSF to CSF Levels of AßO in human AD patients

Following two doses of 20 mg/kg ACU193 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 ACU193 established a no-observed-adverse-effect level, or NOAEL, of 250 mg/kg/dose, which was the maximum feasible dose, given every two weeks 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 every two weeks. 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 ACU193 once every two weeks were administered. Three animals administered the highest 600 mg/kg/dose were sacrificed early for humane reasons on Days 43 or 60 due to ACU193-related, anaphylactoid-type reactions.

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 ACU193 being used in our Phase 1 clinical trial (60 mg/kg).

Based in part on binding to AßOs rather than amyloid plaque, ACU193 has the potential to have a lower rate of ARIA than plaque-clearing anti-amyloid antibodies. Additionally, ACU3B3 showed no apparent increased risk of microhemorrhage when administered in vivo for three months in aged Tg2576 mice, as compared with 3D6, a plaque binding antibody used as a positive control.

With regard to effector function and possible inflammatory effects generally, ACU193 is an IgG2m4 subclass antibody which lacks inflammatory effector function signaling stimulated by other IgG subclasses. Thus, the risk for inflammatory effector function using ACU193 is considered to be low.

Investigational New Drug Application

In October 2020, we submitted an investigational new drug, or IND, application for ACU193 to the FDA. The FDA initially placed the IND on clinical hold until we were able to address the FDA’s concerns regarding potential off-target binding of ACU193 with an additional nonclinical tissue cross reactivity (TCR) study in

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human, monkey, and rat samples. The supplemental TCR study supported the in-vivo GLP safety results. On April 9, 2021, we received an FDA letter advising us that the clinical hold had been removed and authorizing us to proceed with a first-in-human, Phase 1 clinical trial.

Clinical Development Plan

Phase 1 Clinical Trial in AD

In the second quarter of 2021, we initiated a multi-center, randomized, placebo-controlled, single and multiple ascending dose Phase 1 clinical trial of ACU193, which we named “INTERCEPT-AD,” in 62 patients with early AD. The early AD patient set is comprised of individuals who have mild dementia or MCI due to AD. Patients with moderate to severe dementia will not be included. The main objectives of the trial are to evaluate the safety, tolerability, pharmacokinetics, and target engagement of single and multiple ascending doses of ACU193 administered by IV infusion. Pharmacodynamics effects including cognitive testing are expected to be performed on an exploratory basis. The trial is designed to be conducted in two overlapping parts: Part A (the single ascending dose portion) and Part B (the multiple ascending dose portion).

Figure 16: Design of INTERCEPT-AD

Trial Design Part A – Single Ascending Dose

We expect to enroll 32 participants in Part A of our clinical trial, with the participants randomized in a 6:2 ratio into one of four cohorts to receive a single dose of ACU193 or placebo as follows:

• Cohort 1: One IV dose of ACU193 (2 mg/kg) or placebo.

• Cohort 2: One IV dose of ACU193 (10 mg/kg) or placebo.

• Cohort 3: One IV dose of ACU193 (25 mg/kg) or placebo.

• Cohort 4: One IV dose of ACU193 (60 mg/kg) or placebo.

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

Trial Design Part B – Multiple Ascending Dose

We expect to enroll 30 participants in Part B of our clinical trial, with the participants randomized in an 8:2 ratio into one of three cohorts to receive a total of three doses of ACU193 or placebo as follows:

• Cohort 5: One IV dose of ACU193 (10 mg/kg) or placebo once every four weeks.

• Cohort 6: One IV dose of ACU193 (60 mg/kg) or placebo once every four weeks.

• Cohort 7: One IV dose of ACU193 (60 mg/kg) or placebo once every two weeks.

Participants in Cohorts 5 and 6 will be evaluated over approximately 35 weeks, consisting of a seven-week screening period followed by a 28-week, double-blind treatment period. A follow-up safety check will be performed approximately eight weeks after the final visit of the double-blind treatment period.

Participants in Cohort 7 will be evaluated over approximately 31 weeks, consisting of a seven-week screening period, followed by a 24-week, double-blind treatment period. A follow-up safety check will be performed approximately eight weeks after the final visit of the double-blind treatment period.

In order to maintain participant safety for Part B of the clinical trial, dosing of Cohort 5 will begin at least one week after all participants in Cohort 2 of Part A have received one administration of ACU193 or placebo and the Cohort 2 safety data have been reviewed by our internal blinded safety team. For Cohort 6, dosing will begin at least one week after all participants in Cohort 4 of Part A have received one administration of ACU193 or placebo and the Cohort 4 safety data have been reviewed by our internal blinded safety team. Dosing of Cohort 7 will begin after four or more participants in Cohort 6 have been administered two doses of ACU193 or placebo and the Cohort 6 safety data, along with aggregated pharmacokinetic data from Cohort 4, have been reviewed by our internal blinded safety team. If a potential safety signal, an unexpected adverse reaction, or higher than expected exposure occurs, our internal blinded safety team will notify the independent, unblinded DMC to review the safety and pharmacokinetic data and advise on dose escalation. Cohort 7 will allow for additional pharmacokinetic modeling to more accurately determine the half-life of ACU193 if every two-week dosing is necessary.

Endpoints

Our goal for the Phase 1 trial is to establish clinical proof of mechanism of ACU193 in patients with early AD. The endpoints we will measure as part of this trial include:

Primary Endpoint

• safety and immunogenicity, including assessment for ARIA;

Secondary Endpoints and Exploratory Objectives

• pharmacokinetics in plasma;

• determination of CSF concentrations of ACU193;

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In October 2021, we announced the initial dosing of the first patient in the INTERCEPT-AD trial and the subsequent successful sentinel safety review of the first two patients. Due to delays in clinical trial site activation and enrollment that we believe are principally related to effects of the COVID-19 pandemic, we are expanding the anticipated number of trial sites to support our enrollment objectives and anticipated timelines. Clinical trial site activation and patient recruitment and enrollment is ongoing. At present, INTERCEPT-AD is in the SAD portion of the trial. Based on current site activations and enrollment rates, we anticipate reporting our topline data from this trial, including assessments of safety, ARIA-E, pharmacokinetics and target engagement through the full 168 day follow-up period for Cohort 7, in the first half of 2023.

Future Clinical Trials

Subject to establishment of proof of mechanism of ACU193 and the safety and immunogenicity results of INTERCEPT-AD, we intend to advance ACU193 into later stage clinical trials. We plan to explore a proposed therapeutic dose of ACU193 in a future Phase 2/3 clinical trial based on safety, pharmacokinetics and pharmacodynamics assessments of the various dosing cohorts in INTERCEPT-AD. Following, and subject to the results of, INTERCEPT-AD, we plan to engage with the FDA in an end-of-Phase 2 meeting, which we anticipate will occur in the second half of 2023, to discuss the Phase 2/3 clinical trial design and pathway for potential approval. The Phase 2/3 trial is being designed as an adaptive trial, such that after a planned interim analysis of clinical and biomarker changes, a decision could be made to increase the enrollment of the trial to be adequately powered as a Phase 3 pivotal trial, or to continue the trial as a Phase 2 clinical trial. The Phase 2/3 trial will utilize standard cognitive measures that are widely employed in AD trials and most highly sensitive to changes in mild AD patients, including ADAS-COG 13, CDR-sb, ADCS-iADL, iADRS, MMSE, and potentially others including computerized neuropsychological testing. Additionally, a number of biomarkers may be studied including blood flow as determined by ASL pulse sequence on MRI, plasma or CSF p-tau, amyloid PET scanning, and tau PET scanning. Selected endpoints will be used to inform the interim decision whether to expand the trial and whether to initiate a second Phase 3 clinical trial.

Combination Potential

While we believe ACU193, 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. The pathology of AD is complex, and many experts in the field expect that combination therapy using 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 it is likely that they will 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 ACU193. 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.

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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 ACU193 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 ACU193 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

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 ACU193 will include safety profile, efficacy, cost, method of administration, level of marketing activity, insurance reimbursement and intellectual property protection.

If approved, ACU193 will compete with therapies currently approved for the treatment of AD, which have primarily been developed to treat the symptoms of AD rather than the underlying cause of the disease, such as memantine and cholinesterase inhibitors. ACU193 may also compete with one or more potentially disease-modifying therapeutics that target Aß or amyloid plaques, the most advanced of which is Biogen Inc.’s Aduhelm (aducanumab), which the FDA approved in June 2021 under the accelerated approval pathway, which allows for earlier approval of drugs that treat serious conditions, and that fill an unmet medical need based on a surrogate endpoint. Regulatory approval of aducanumab is pending in Europe and Japan. Eisai Co., Ltd. (lecenamab), Eli Lilly and Company (donenamab), and Roche Holding AG (gantenerumab), are anticipated to complete Phase 3 studies in 2022 and 2023 with their amyloid plaque targeting monoclonal antibody drugs and may obtain FDA approval under the accelerated approval pathway or full approval based on Phase 3 results.

Other companies known to be developing therapies with Aß, AßO-, and amyloid plaque-related targets include Alzheon, Inc., Alzinova AB, Chugai Pharmaceutical Co. Ltd., Cognition Therapeutics, Inc., Grifols, S.A., KalGene Pharmaceuticals, Inc., Neurimmune AG, Novartis AG, ProMIS Neurosciences, Inc., Prothena Biosciences, Inc., Vaxxinity, Inc., Vivoryon Therapeutics N.V. and Wren Therapeutics, Inc. Additionally, ACU193, 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 Inc., AC Immune SA, Alector, Inc., Anavex Life Sciences Corp., Annovis Bio, Inc., Athira Pharma, Inc., Biohaven Pharmaceuticals, Inc., Cassava Sciences, Inc., Cortexyme, Inc., Denali Therapeutics, Inc., Johnson & Johnson (including Janssen, its wholly-owned subsidiary) and Takeda Pharmaceutical Co. Ltd.

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 amyloid beta-derived diffusible ligands, or ADDL, 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 ACU193, an ADDL antibody, and intellectual property related to ACU193 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

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granted us an exclusive, perpetual, irrevocable, royalty-free, worldwide license, with right to 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 ACU193.

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, ACU193, is expected to come from biologic regulatory exclusivity. We expect that once approved by regulatory agencies, ACU193 will receive the benefit of 12 years of market exclusivity in the U.S. 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, ACU193. The license grant arose from our collaboration agreement with Merck to research, discover, and develop technology related to ADDLs. During our collaboration, ACU193, 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 ACU193, 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 ACU193 patent portfolio. Acumen has also paid for and continues to pay all costs and fees associated with the prosecution and maintenance of the licensed ACU193 patent portfolio.

As of March 25, 2022, Acumen licenses from Merck one issued U.S. patent, 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, ACU193. These patents are projected to expire in July of 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,

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even if the claims cover other products or product candidate. Where one patent covers multiple products or product candidate, 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, or PCT, 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 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,

post-approval

monitoring, and post-approval reporting of biologics such as those we are developing. We, along with our third-party contractors, will be required to navigate the various preclinical, clinical, manufacturing and commercial approval requirements of the governing regulatory agencies of the countries in which we wish to conduct studies or seek approval or licensure of our product candidates. The process of obtaining regulatory approvals and the subsequent compliance with applicable federal, state, local and foreign statutes and regulations require the expenditure of substantial time and financial resources. 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.

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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, or PHSA, and other federal, state, local and foreign statutes and regulations. The process required by the FDA before biologics may be marketed in the United States generally involves the following:

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

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

Preclinical and Clinical Trials

Prior to beginning the first clinical trial with a product candidate in the United States, 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. In the United States, 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 central focus of an IND submission is on the general investigational plan and the protocol(s) for clinical studies. The IND also includes results of animal and

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studies assessing the toxicology, pharmacokinetics, pharmacology, and pharmacodynamic characteristics of the product; chemistry, manufacturing, and controls information; and any available human data or literature to support the use of the investigational product. An IND must become effective before human clinical trials may begin. 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. In such a case, the IND may be placed on clinical hold and the IND sponsor and the FDA must resolve any outstanding concerns or questions before the clinical trial can begin. Submission of an IND therefore may or may not result in FDA authorization to begin a clinical trial.

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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 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.

While clinical trials are ongoing, the FDA may 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 cause the suspension of an ongoing study, or part 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. 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 or that the trial is unlikely to meet its stated objectives. 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, which provides authorization for whether or not a study may move forward at designated check points 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 for subjects or other grounds, such as no demonstration of efficacy. There are also requirements governing the reporting of ongoing clinical studies and clinical study results to public registries. In the United States, information about applicable clinical trials, including clinical trials results, must be submitted within specific timeframes for publication on the www.clinicaltrials.gov website.

Progress reports detailing the results of the clinical trials, among other information, must be submitted at least annually to the FDA. Written IND safety reports must be submitted to the FDA and the investigators fifteen days after the trial sponsor determines the information qualifies for reporting for serious and unexpected suspected adverse events, findings from other studies or animal or in vitro testing suggest a significant risk for human participants exposed to the drug or biologic, or for any clinically important increase in the rate of a serious suspected adverse reaction over that listed in the protocol or investigator brochure. The sponsor must also notify the FDA of any unexpected fatal or life-threatening suspected adverse reaction as soon as possible but in no case later than seven calendar days after the sponsor’s initial receipt of the information.

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

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In some cases, the FDA may require, or companies may voluntarily pursue, additional clinical trials after a product is approved to gain more information about the product. 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. The BLA must include data available from preclinical and clinical studies, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls, and proposed labeling, among other things. Data can come from company-sponsored clinical studies intended to test the safety and effectiveness of a use of the product, or from a number of alternative sources, including studies initiated by independent investigators. 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. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission and may request additional information. In this event, the BLA must be resubmitted with the additional information. Once a BLA has been accepted for filing, the FDA’s goal is to review standard applications within ten 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. The FDA reviews a BLA to determine, among other things, whether a product is safe, pure and potent and the facility in which it is manufactured, processed, packed or held meets standards designed to assure the product’s continued safety, purity and potency. The FDA may also convene an advisory committee to provide clinical insight on application review questions. An advisory committee is a panel of independent experts, including clinicians and other scientific experts, which reviews, evaluates and provides a recommendation as to whether the application should be approved and under what conditions. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations carefully when making decisions.

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 cGMP 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.

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If the FDA determines that the application, manufacturing process or manufacturing facilities are not acceptable, it will outline the deficiencies in the submission and often will request additional testing or information. Notwithstanding the submission of any requested additional information, the FDA ultimately may decide that the application does not satisfy the regulatory criteria for approval. 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 Complete Response Letter, or 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, 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 or the development of adequate controls and specifications. Once approved, the FDA may withdraw the product approval if compliance with pre- and post-marketing requirements is not maintained or if problems occur after the product reaches the marketplace. The FDA may require one or more Phase 4 post-market studies and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization, and may limit further marketing of the product based on the results of these post-marketing studies.

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, priority review, and accelerated approval.

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 and, once a BLA is submitted, the product candidate may be eligible for priority review. A fast track product may also be eligible for rolling review, where 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 to expedite its development and review. A product candidate can receive 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

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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 other types of FDA programs intended to expedite the FDA review and approval process, such as priority review and accelerated approval. 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 ten months under standard review).

Additionally, product candidates studied for their safety and effectiveness in treating serious or life-threatening diseases or conditions may receive accelerated approval upon 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.

Fast track designation, breakthrough therapy designation, and priority review, accelerated approval 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.

Orphan Drug Designation and Exclusivity

Under the Orphan Drug Act, the FDA may grant orphan designation 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. Orphan drug designation must be requested before submitting a BLA. After the FDA grants orphan drug designation, the generic identity of the therapeutic agent and its potential orphan use are disclosed publicly by the FDA.

If a product that has orphan drug designation subsequently receives the first FDA approval for a particular active ingredient 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 orphan drug designation are tax credits for certain research and a waiver of the BLA application user fee.

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A designated orphan drug may not receive orphan drug exclusivity if it is approved for a use that is broader than the indication for which it received orphan designation. In addition, orphan drug exclusive marketing rights in the United States may be lost if the FDA later determines that the request for designation was materially defective or, as noted above, if a second applicant demonstrates that its product is clinically superior to the approved product with orphan exclusivity or the manufacturer of the approved product is unable to assure sufficient quantities of the product to meet the needs of patients with the rare disease or condition.

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. Although physicians may prescribe approved products for off-label uses, manufacturers may not market or promote such uses. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of off-label uses, including not only by Company employees but also by agents of the Company or those speaking on the Company’s behalf, 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 also are 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 cGMP, which impose certain procedural and documentation requirements up. Changes to the manufacturing process are strictly regulated, and, depending on the significance of the change, may require prior FDA approval before being implemented. FDA regulations also require investigation and correction of any deviations from cGMP and impose reporting requirements. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP 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:

• fines, warning letters, or untitled letters;

• clinical holds on clinical studies;

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• 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, which requires that there be no clinically meaningful differences between the biological product and the reference product in terms of safety, purity, and potency, can be shown through analytical studies, animal studies, and a clinical study or studies. 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. At this juncture, it is unclear whether products deemed “interchangeable” by the FDA will, in fact, be readily substituted by pharmacies, which are governed by state pharmacy law.

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 Patient Protection and Affordable Care Act, 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 and may constrain the financial arrangements and relationships through which we research, as well as, sell, market and distribute any products for which we obtain marketing approval. Such laws include, without limitation, federal and state anti-kickback, fraud and abuse, false claims, data privacy and security and physician and other health care provider transparency laws and regulations. The laws that will affect our operations include, but are not limited to:

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Because of the breadth of these laws and the narrowness of the statutory exceptions and regulatory safe harbors available, it is possible that some of our business activities could be subject to challenge under one or more of

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such laws. It is possible that governmental authorities will conclude that our business practices may not comply with current or future statutes, regulations or case law involving applicable fraud and abuse or other healthcare laws and regulations. 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 these laws or any other governmental regulations that may apply to us, we may be subject to significant penalties, including, without limitation, civil, criminal and administrative penalties, damages, fines, disgorgement, 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 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 harm our business.

Coverage and Reimbursement

In the United States and in other countries, patients who are provided medical treatment for their conditions generally rely on third-party payors to reimburse all or part of the costs associated with their treatment. Sales of any product depend, in part, on the extent to which such product will be covered by third-party payors, such as federal, state, and foreign government healthcare programs (e.g., Medicare, Medicaid, TRICARE), commercial insurance and managed healthcare organizations, and the level of reimbursement for such product by third-party payors. Decisions regarding the extent of coverage and amount of reimbursement to be provided are made on a plan-by-plan basis. The principal decisions about reimbursement for new medicines are typically made by CMS, an agency within the U.S. Department of Health and Human Services, or HHS. CMS decides whether and to what extent products will be covered and reimbursed under Medicare and private payors tend to follow CMS to a substantial degree.

Third-party payors determine which products and procedures they will cover and establish reimbursement levels. These third-party payors are increasingly reducing reimbursements for medical products, drugs and services. In addition, the U.S. government, state legislatures and foreign governments have continued implementing cost-containment programs, including price controls, restrictions on coverage and reimbursement and requirements for substitution of generic products. Patients who are treated in-office for a medical condition generally rely on third-party payors to reimburse all or part of the costs associated with the procedure, including costs associated with products used during the procedure, and may be unwilling to undergo such procedures in the absence of such coverage and adequate reimbursement. In addition, for products administered under the supervision of a physician, obtaining coverage and adequate reimbursement may be particularly difficult because of the higher prices often associated with such drugs.

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. In order to secure coverage and reimbursement for any product that might be approved for sale, we may need to conduct expensive pharmacoeconomic studies in order to demonstrate the medical necessity and cost-effectiveness of our products. Adoption of price controls and cost-containment measures, and adoption of more restrictive policies in jurisdictions with existing controls and measures, could further limit sales of any product. Decreases in third-party reimbursement for any product or a decision by a third-party payor not to cover a product could reduce physician usage and patient demand for the product and also have a material adverse effect on sales.

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Healthcare Reform

In March 2010, the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, each as amended, collectively known as the ACA, was enacted, which substantially changed the way healthcare is financed by both governmental and private insurers, and significantly affected the pharmaceutical industry. The ACA contains a number of provisions, including those governing enrollment in federal healthcare programs, reimbursement adjustments and changes to fraud and abuse laws. For example, the ACA:

Since its enactment, there have been executive, judicial and Congressional challenges to certain aspects of the ACA, and we expect there will be additional challenges and amendments to the ACA in the future. On June 17, 2021 the U.S. Supreme Court dismissed a challenge on procedural grounds that argued the ACA is unconstitutional in its entirety because the “individual mandate” was repealed by Congress. Thus, the ACA will remain in effect in its current form. Prior to the U.S. Supreme Court ruling, on January 28, 2021, President Biden issued an executive order that initiated a special enrollment period from February 15, 2021 through August 15, 2021 for purposes of obtaining health insurance coverage through the ACA marketplace. The executive order also instructed certain governmental agencies to review and reconsider their existing policies and rules that limit access to healthcare, including among others, reexamining Medicaid demonstration projects and waiver programs that include work requirements, and policies that create unnecessary barriers to obtaining access to health insurance coverage through Medicaid or the ACA. It is possible that the ACA will be subject to judicial or Congressional challenges in the future. It is also unclear how other such challenges and the healthcare reform measures of the Biden administration will impact the ACA or our business.

Other legislative changes have been proposed and adopted since the ACA was enacted, including aggregate reductions of Medicare payments to providers of 2% per year, which began in 2013, and due to subsequent legislative amendments to the statute, will remain in effect through 2031, with the exception of a temporary suspension from May 1, 2020 through March 31, 2022 due to the COVID-19 pandemic. Under current legislation the actual reduction in Medicare payments will vary from 1% in 2022 to up to 3% in the final fiscal year of this sequester. Additionally, on March 11, 2021, President Biden signed the American Rescue Plan Act of 2021 into law, which eliminates the statutory Medicaid drug rebate cap, currently set at 100% of a drug’s average manufacturer price, for single source and innovator multiple source drugs, beginning January 1, 2024.

Moreover, there has recently been heightened governmental scrutiny over the manner in which manufacturers set prices for their marketed products, which has resulted in several Congressional inquiries, proposed and enacted legislation and executive orders issued by the prior presidential administration designed to, among other things, bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs, and reform government program reimbursement methodologies for drug products. At the federal level, the Trump administration used several means to propose or implement drug pricing reform, including through federal budget proposals, executive orders and policy initiatives. However, several lawsuits have been brought against HHS challenging various aspects of the rules implemented during the Trump administration. As a result, the Biden administration and HHS have delayed the implementation or published rules rescinding some of these

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Trump-era policies. In July 2021, the Biden administration released an executive order, “Promoting Competition in the American Economy,” with multiple provisions aimed at prescription drugs. In response to Biden’s executive order, on September 9, 2021, HHS released a Comprehensive Plan for Addressing High Drug Prices that outlines principles for drug pricing reform and sets out a variety of potential legislative policies that Congress could pursue as well as potential administrative actions HHS can take to advance these principles. No legislation or administrative actions have been finalized to implement these principles. It is also possible that additional governmental action is taken in response to the COVID-19 pandemic. 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.

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 1, 2022, we had 17 employees, 14 of which were full time. Of the 17 employees, there were 11 in research and development and six in general and administrative functions. We also utilized 12 consultants, nine in various roles related to research and development and three in 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 427 Park St., Charlottesville, Virginia 22902 and our telephone number is (434) 297-1000.

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 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

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.

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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 focused on pioneering a novel disease-modifying therapeutic approach to treat AD. We were incorporated in 1996 and were party to an exclusive license and research collaboration with Merck in 2003. Although we acquired the exclusive rights to ACU193 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 very limited operating history, which may make it difficult to evaluate the success of our business to date and assess our future viability. Drug development is a highly uncertain undertaking and involves a substantial degree of risk. We received clearance of our Investigational New Drug application, or IND, for our sole product candidate, ACU193, 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 the subsequent successful sentinel safety review of the first two patients. Due to delays in clinical trial site activation and patient enrollment that we believe are principally related to effects of the COVID-19 pandemic, we are expanding the anticipated number of trial sites to support our enrollment objectives and anticipated timelines. However, we cannot assure that we will not experience additional delays in site activation or enrollment. Clinical trial site activation and patient recruitment and enrollment is ongoing. To date, we have not completed a clinical trial, 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 sales and we may never be profitable.

We have no product candidates approved for sale, have never generated any revenue from 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, 2021 and 2020, our net losses were $100.6 million and $7.3 million, respectively. As of December 31, 2021, we had an accumulated deficit of $127.6 million.

To date, we have devoted most of our financial resources to research and development of ACU193, including our nonclinical development activities of ACU193, 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, ACU193 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 ACU193 or another drug with significant revenue.

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

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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 ACU193 for AD and evaluate future product candidates. 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.

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, ACU193. Developing ACU193 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 ACU193 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. Furthermore, we expect to incur additional 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, 2021, we had $122.2 million in cash and cash equivalents and $103.7 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 at least through 2025. However, 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 we anticipate 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 number and characteristics of product candidates that we pursue;

• our need to expand our research and development activities;

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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 and the recent disruptions to and volatility in the credit and financial markets in the United States and worldwide resulting from the ongoing COVID-19 pandemic and conflict with Russia and Ukraine. 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.

Risks Related to the Development of our Product Candidates

We are substantially dependent on the success of ACU193, 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 of ACU193, which is currently our only product candidate. Before seeking marketing approval from regulatory authorities for the sale of ACU193, 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 of our product candidates 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 ACU193 will be successful in clinical trials. Further, ACU193 may not receive regulatory approval even if it is successful in clinical trials. If we do not receive regulatory approvals for ACU193, 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 ACU193 by us or by one or more of our partners. The clinical and commercial success of ACU193 will depend on a number of factors, including the following:

• the results from INTERCEPT-AD and future clinical trials of ACU193;

• the frequency and severity of adverse effects of ACU193;

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• effectively competing with other AD therapies;

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

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 ACU193. If we are not successful in commercializing ACU193, or are significantly delayed in doing so, our business will be materially harmed.

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 very 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 ACU193 for treating AD. The development and, if approved, commercialization of ACU193 subjects us to a number of challenges, including ensuring that we select an effective dose of ACU193, 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 ACU193, 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, of physicians to prescribe novel treatments.

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 ACU193, 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

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of the amyloid-beta, or Aß, peptide that are distinct from other forms of amyloid. AßOs have gained scientific acceptance as primary toxins involved in the initiation and propagation of AD pathology. Based on the results of our nonclinical studies to date, we believe ACU193 is different from current and prior clinical-stage anti-amyloid drugs and product candidates based on its selectivity for AßOs. We believe that this is a novel mechanism which has the potential to provide more clinically meaningful benefits, with a possible improved safety profile, as compared to approved therapies and product candidates in development. However, we may ultimately discover that ACU193 does not possess properties required for therapeutic effectiveness. We have no evidence regarding the efficacy, safety or tolerability of ACU193 in humans. We may spend substantial funds attempting to develop ACU193 or other product candidates and never succeed in doing so.

The market for any products that we successfully develop, if any, will also depend on the cost of the product. We do not yet have sufficient information to reliably estimate what it would cost to commercially manufacture ACU193, and the actual cost to manufacture ACU193 or any drug we develop in the future could materially and adversely affect the commercial viability of the drug. We may also find that the manufacture of our product candidates is more difficult than anticipated, resulting in an inability to produce a sufficient amount of our product candidates for our clinical trials or, if approved, commercial supply. If we do not successfully develop ACU193 or any other drug we develop with drug product cannot be reliably and economically manufactured at scale, we will not become profitable, which would materially and adversely affect the value of our common stock.

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. ACU193 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.

The research and development of product candidates is extremely risky. Only a small percentage of product candidates that enter the development process ever receive marketing approval. Before obtaining marketing approval from regulatory authorities for the sale of any product candidate, we must complete nonclinical development and then conduct extensive clinical trials to demonstrate the safety and efficacy of our product candidates in humans. Clinical testing is expensive and can take many years to complete, and its outcome is inherently uncertain.

The results of nonclinical studies and early clinical trials are not necessarily predictive of future results and ACU193, or any other product candidate that we may develop, may not be further developed or have favorable results in later studies or trials. Clinical trial failure may result from a multitude of factors including, but not limited to, flaws in study design, dose selection, placebo effect, patient enrollment criteria and failure to demonstrate favorable safety or efficacy traits. As such, failure in clinical trials can occur at any stage of testing. A number of companies in the pharmaceutical industry have suffered setbacks in the advancement of their product candidates into later-stage clinical trials due to lack of efficacy or adverse safety profiles, notwithstanding results in earlier nonclinical studies or clinical trials. We intend to enroll 62 patients with early AD in INTERCEPT-AD. Even if the results of INTERCEPT-AD are positive, it may not be predictive of the results of outcomes in our later-stage clinical trials. The results of clinical trials in one set of patients or disease indications may not be predictive of those obtained in another. In some instances, there can be significant variability in safety or efficacy results between different clinical trials of the same product candidate due to numerous factors, including changes in trial procedures set forth in protocols, differences in the size and type of the patient populations, changes in and adherence to the dosing regimen and other clinical trial protocols and the rate of dropout among clinical trial participants. A number of companies in the pharmaceutical industry have suffered significant setbacks in advanced clinical trials due to lack of efficacy or unacceptable safety issues, notwithstanding promising results in earlier trials. This is particularly true in AD, where failure rates historically are higher than in most other disease areas.

In the event of negative or inconclusive results, we may decide, or regulatory authorities may require us, to conduct additional clinical trials or nonclinical studies. In addition, data obtained from clinical trials and nonclinical studies is susceptible to varying interpretations, and regulatory authorities may not interpret our data

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as favorably as we do, which may further delay, limit or prevent development efforts, clinical trials or marketing approval. Furthermore, as more competing product candidates within a particular class of drugs proceed through clinical development to regulatory review and approval, the amount and type of clinical data that may be required by regulatory authorities may increase or change.

If we are unable to complete nonclinical studies or clinical trials of ACU193 or future product candidates, due to safety concerns or otherwise, or if the results of these trials are not sufficient to convince regulatory authorities of their safety or efficacy, we will not be able to obtain marketing approval for commercialization on a timely basis or at all. Even if we are able to obtain marketing approval for ACU193 or any future product candidates, those approvals may be for indications or dose levels that deviate from our desired approach or may contain other limitations that would adversely affect our ability to generate revenue from sales of those product candidates. Moreover, if we are not able to differentiate our product candidate against other approved product candidates within the same class of drugs, or if any of the other circumstances described above occur, our business would be harmed and our ability to generate revenue from that class of drugs would be severely impaired.

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

We are early in our development efforts for ACU193, and will need to successfully complete our ongoing and planned clinical trials, including pivotal clinical trials, in order to obtain FDA approval to market ACU193 or any other product candidate we seek to develop. Carrying out clinical trials and the submission of a successful BLA is a complicated process. Although members of the Acumen team have significant experience in clinical development of drugs through regulatory approval, as an organization, Acumen recently began conducting its first clinical trial, has no experience in conducting any clinical trials, has limited experience in preparing regulatory submissions and has not previously submitted a BLA for any product candidate.

In addition, we have had limited interactions with the FDA and cannot be certain how many clinical trials of ACU193 will be required or how such trials should be designed. Consequently, we may be unable to successfully and efficiently execute and complete necessary clinical trials in a way that leads to BLA submission and approval of ACU193 or any other product candidate. We may require more time and incur greater costs than our competitors and may not succeed in obtaining regulatory approvals of product candidates that we develop. Failure to commence or complete, or delays in, our planned clinical trials, could prevent us from or delay us in commercializing ACU193 or any future product candidates we may develop, and failure to successfully complete any of these activities in a timely manner could have a material adverse impact on our business and financial performance.

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

We may experience numerous unforeseen events during, or as a result of, clinical trials that could delay or prevent our ability to receive marketing approval or commercialize our product candidates, including:

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• changes to clinical trial protocols;

Adverse side effects, properties or other safety risks associated with ACU193 or any future product candidates could delay or preclude approval, cause us to suspend or discontinue clinical trials, abandon further development, limit the commercial profile of an approved label or result in significant negative consequences following marketing approval, if any.

As is the case with pharmaceuticals generally, it is possible that there may be side effects and adverse events associated with the use of ACU193 or any future product candidates we may develop. Results of INTERCEPT-AD, or future clinical trials, could reveal a high and unacceptable severity and prevalence of side effects or unexpected characteristics as the clinical trials progress to greater exposures and a larger number of patients. Undesirable side effects caused by, or unexpected or unacceptable characteristics associated with, ACU193 or any future product candidates we may develop, could result in the delay, suspension or termination of clinical trials by us, the FDA or other regulatory authorities, or IRBs for a number of reasons. We may also elect to limit their development to more narrow uses or subpopulations in which the undesirable side effects or other characteristics are less prevalent, less

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severe or more acceptable from a risk-benefit perspective, which may limit the commercial expectations for such product candidate if approved. If we elect or are required to further delay, suspend or terminate any clinical trial of any product candidates we may develop, the commercial prospects of such product candidates will be harmed and our ability to generate drug revenues from any such product candidates will be delayed or eliminated.

It is possible that, as we test ACU193 in INTERCEPT-AD or future trials, or as the use of ACU193 becomes more widespread if it receives regulatory approval, we may identify additional adverse events that were not identified or not considered significant in our earlier trials. If such side effects become later known in development or upon approval, if any, such findings may harm our business, financial condition, results of operations and prospects significantly. If we or others later identify undesirable side effects, a number of potentially significant negative consequences could result, including:

• we may decide to remove such product candidates from the market;

• we could be sued and held liable for harm caused to patients;

• our reputation may suffer.

Any of these events could prevent us from achieving or maintaining market acceptance of ACU193 or any future product candidates, if approved, and could significantly harm our business, financial condition, results of operations and prospects.

We have experienced and may continue to experience delays or difficulties in the enrollment and retention of patients in clinical trials, which could delay or prevent our receipt of necessary regulatory approvals.

Successful and timely completion of clinical trials will require that we enroll a sufficient number of patients. Patient enrollment, a significant factor in the timing of clinical trials, is affected by many factors, including the size and nature of the patient population and competition for patients eligible for our clinical trials with competitors which may have ongoing clinical trials for product candidates that are under development to treat the same indications as one or more of our product candidates or approved products for the conditions for which we are developing our product candidates.

Trials may be subject to delays as a result of patient enrollment taking longer than anticipated or patient withdrawal. We may not be able to initiate or continue clinical trials for our product candidates if we are unable

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to locate and enroll a sufficient number of eligible patients to participate in these trials as required by the FDA, EMA or foreign regulatory authorities. We cannot predict how successful we will be at enrolling subjects in future clinical trials. We have experienced delays in clinical site initiation and patient enrollment as a result of the COVID-19 pandemic. Subject enrollment is affected by other factors including:

• the severity and difficulty of diagnosing the disease under investigation;

• the eligibility and exclusion criteria for the trial in question;

• the size of the patient population and process for identifying patients;

• the design of the trial protocol;

• the willingness of patients to be enrolled in our clinical trials;

• the efforts to facilitate timely enrollment in clinical trials;

• the patient referral practices of physicians;

• the ability to monitor patients adequately during and after treatment; and

Our inability to enroll a sufficient number of patients for clinical trials would result in significant delays and could require us to abandon one or more clinical trials altogether. Enrollment delays in these clinical trials may result in increased development costs for our product candidates, which would cause the value of our company to decline and limit our ability to obtain additional financing.

Furthermore, we expect to rely on CROs and clinical trial sites to ensure the proper and timely conduct of our clinical trials and we will have limited influence over their performance. Additionally, even if we are able to enroll a sufficient number of patients for our clinical trials, we may have difficulty maintaining enrollment of such patients in our clinical trials.

Interim, “topline” and preliminary results from our clinical trials that we announce or publish from time to time may change as more data become available and is subject to audit and verification procedures that could result in material changes in the final data.

From time to time, we may publish interim, topline or preliminary results from our clinical trials. Interim results from clinical trials that we may complete are subject to the risk that one or more of the clinical outcomes may materially change as patient enrollment continues and more patient data become available. Preliminary or topline results also remain subject to audit and verification procedures that may result in the final data being materially different from the preliminary data we previously published. As a result, interim and preliminary data should be viewed with caution until the final data are reported. Differences between preliminary, topline or interim data and final data could significantly harm our business prospects and may cause the trading price of our common stock to fluctuate significantly. We also make assumptions, estimations, calculations and conclusions as part of our analyses of data, and we may not have received or had the opportunity to fully and carefully evaluate all data. As

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a result, the topline results that we report may differ from future results of the same studies, or different conclusions or considerations may qualify such results, once additional data have been received and fully evaluated.

ABOS US Equity

ABOS · 10-K · period ended 2021-12-31

Item 1. Business.

Item 1A. Risk Factors.

ABOS US Equity☆

ABOS · 10-K · period ended 2021-12-31

Item 1. Business.

Item 1A. Risk Factors.

ABOS US Equity