10-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2024

Commission File Number 001-39402

ANNEXON, INC.

(Exact name of Registrant as specified in its Charter)

1400 Sierra Point Parkway, Bldg C, Suite 200

Brisbane, California94005

(Address of principal executive offices including zip code)

Registrant’s telephone number, including area code: (650) 822-5500

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

Title of each class TradingSymbol(s) Name of each exchange on which registered

Common Stock, par value $0.001 per share ANNX The Nasdaq Stock 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 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. ☐

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

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

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

As of June 28, 2024, the aggregate market value of the Registrant’s Common Stock held by non-affiliates of the Registrant (based on the closing sales price of such shares on the Nasdaq Global Select Market on June 28, 2024) was approximately $477.2 million. For purposes of calculating the aggregate market value of shares held by non-affiliates, we have assumed that all outstanding shares are held by non-affiliates, except for shares held by each of our executive officers, directors and 10% or greater stockholders. This calculation does not reflect a determination that such parties are affiliates for any other purpose.

The number of shares of the Registrant’s Common Stock outstanding as of February 28, 2025 was 109,709,826. This number does not include 38,543,577 shares of Common Stock issuable upon the exercise of pre-funded warrants (which are immediately exercisable at an exercise

price of $0.001 per share of Common Stock, subject to beneficial ownership limitations). See Note 6—Stockholders’ Equity to the Registrant’s audited consolidated financial statements.

Table of Contents

Page

PART I

Item 1. Business 1

Item 1A. Risk Factors 30

Item 1B. Unresolved Staff Comments 78

Item 1C. Cybersecurity 78

Item 2. Properties 79

Item 3. Legal Proceedings 79

Item 4. Mine Safety Disclosures 80

PART II

Item 6. [Reserved] 81

Item 7A. Quantitative and Qualitative Disclosures About Market Risk 91

Item 8. Financial Statements and Supplementary Data 92

Item 9A. Controls and Procedures 116

Item 9B. Other Information 117

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections 117

PART III

Item 10. Directors, Executive Officers and Corporate Governance 118

Item 11. Executive Compensation 118

Item 14. Principal Accountant Fees and Services 118

PART IV

Item 15. Exhibits, Financial Statement Schedules 119

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements 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 strategy, future financial condition, future operations, projected costs, prospects, plans, objectives of management and expected market growth, are forward-looking statements. In some cases, you can identify forward-looking statements by terminology such as “aim,” “anticipate,” “assume,” “believe,” “contemplate,” “continue,” “could,” “design,” “due,” “estimate,” “expect,” “goal,” “intend,” “may,” “objective,” “plan,” “positioned,” “potential,” “predict,” “seek,” “should,” “target,” “will,” “would” and other similar expressions that are predictions of or indicate future events and future trends, or the negative of these terms or other comparable terminology. These forward-looking statements include, but are not limited to, statements about:

• our expectations regarding the potential market size and size of the potential patient populations for our product candidates and any future product candidates, if approved for commercial use;

• our clinical and regulatory development plans;

• our expectations with regard to the initiation, scope, rate of progress, enrollment, dosing and results of our clinical studies, preclinical studies and research and development programs, including the timing and availability of data from such studies;

• the timing of commencement of future nonclinical studies, preclinical studies and clinical trials and research and development programs;

• our ability to acquire, discover, develop and advance product candidates into, and successfully complete, clinical trials;

• our intentions and our ability to establish collaborations and/or partnerships;

• the timing or likelihood of regulatory filings and approvals for our product candidates;

• our commercialization, marketing and manufacturing capabilities and expectations;

• our intentions with respect to the commercialization of our product candidates;

• the pricing and reimbursement of our product candidates, if approved;

• the implementation of our business model and strategic plans for our business and product candidates, including additional indications for which we may pursue;

• the scope of protection we are able to establish and maintain for intellectual property rights covering our product candidates, including the projected terms of patent protection;

• estimates regarding the sufficiency of our cash resources and our expenses, future revenue, capital requirements, our needs for additional financing and our ability to obtain additional capital;

• the potential future sales of our common stock under our at-the-market offering program;

• our future financial or operating performance;

• developments and projections relating to our competitors and our industry, including competing products; and

•our plans, objectives, expectations and initiations and any other statements that are not historical facts.

We have based these forward-looking statements largely on our current expectations, estimates, forecasts and projections about future events and financial trends that we believe may affect our financial condition, results of operations, business strategy and financial needs. In light of the significant uncertainties in these forward-looking statements, you should not rely upon forward-looking statements as predictions of future events. Although we believe that we have a reasonable basis for each forward-looking statement contained in this Annual Report on Form 10-K, we cannot guarantee that the future results, levels of activity, performance or events and circumstances reflected in the forward-looking statements will be achieved or occur at all. You should refer to the sections titled “Summary Risk Factor,” “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in this Annual Report on Form 10-K for a discussion of important factors that may cause our actual results

to differ materially from those expressed or implied by our forward-looking statements. Furthermore, if our forward-looking statements prove to be inaccurate, the inaccuracy may be material. Except as required by law, we undertake no obligation to publicly update any forward-looking statements, whether as a result of new information, future events or otherwise.

You should read this Annual Report on Form 10-K and the documents that we reference in this Annual Report on Form 10-K and have filed as exhibits completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of the forward-looking statements in this Annual Report on Form 10-K by these cautionary statements.

SUMMARY RISK FACTORS

The following summarizes the most material risks that make an investment in our securities risky or speculative. If any of the following risks occur or persist, our business, financial condition and results of operations could be materially harmed and the price of our common stock could significantly decline.

•

We are a clinical-stage biopharmaceutical company with a limited operating history and no products approved for commercial sale. We have incurred significant losses since our inception, and we anticipate that we will continue to incur significant losses for the foreseeable future, which, together with our limited operating history, makes it difficult to assess our future viability.

•

We will require substantial additional financing to achieve our goals, and a failure to obtain this necessary capital when needed on acceptable terms, or at all, could force us to delay, limit, reduce or terminate our product development programs, commercialization efforts or other operations.

•

Our business is heavily dependent on the successful development, regulatory approval and commercialization of our product candidates, some of which are in early stages of clinical development.

•

Research and development of biopharmaceutical products is inherently risky. We cannot give any assurance that any of our product candidates will receive regulatory approval, which is necessary before they can be commercialized.

•

We may encounter substantial delays in our clinical trials or may not be able to conduct or complete our clinical trials on the timelines we expect.

•

We conduct, and in the future plan to conduct, clinical trials for product candidates outside the United States, and the U.S. Food and Drug Administration, or FDA, and comparable foreign regulatory authorities may not accept data from such trials.

•

Adverse events or undesirable side effects caused by, or other unexpected properties of, any of our product candidates could halt their clinical development, delay or prevent their regulatory approval, limit their commercial potential or result in significant negative consequences.

•

We rely on third-party suppliers to manufacture our product candidates, and we intend to rely on third parties to produce commercial supplies of any approved product. The loss of these suppliers, or their failure to comply with applicable regulatory requirements or to provide us with sufficient quantities at acceptable quality levels or prices, or at all, would materially and adversely affect our business.

•

The successful commercialization of our product candidates will depend in part on the extent to which governmental authorities and health insurers establish adequate coverage, reimbursement levels and pricing policies. Failure to obtain or maintain coverage and adequate reimbursement for our product candidates, if approved, could limit our ability to market those products and decrease our ability to generate revenue.

•

Any collaboration arrangements that we may enter into in the future may not be successful, which could adversely affect our ability to develop and commercialize our product candidates.

•

If we are unable to obtain, maintain and enforce intellectual property protection directed to our current and any future technologies that we develop, others may be able to make, use or sell products substantially the same as ours, which could adversely affect our ability to compete in the market.

•

Our stock price has been volatile, and could in the future be volatile, and you may not be able to resell shares of our common stock at or above the price you paid.

•

Actual or perceived failure to comply with applicable data protection laws, regulations, standards, contractual obligations and other requirements related to data privacy and security could lead to government enforcement actions and civil or criminal penalties, private litigation (including class actions) or adverse publicity and otherwise could negatively affect our results of operations and business.

iii

PART I

Item 1. Business.

In this Annual Report on Form 10-K, “we,” “our,” “us,” “Annexon” and the “Company” refer to Annexon, Inc. and its consolidated subsidiary. Annexon, Annexon, Inc., the Annexon logo and other trade names, trademarks or service marks of Annexon are the property of Annexon, Inc. This report contains references to our trademarks and to trademarks belonging to other entities. Trade names, trademarks and service marks of other companies appearing in this report are the property of their respective holders. We do not intend our use or display of other companies’ trade names or trademarks to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

Overview

We are a clinical-stage biopharmaceutical company pioneering a new class of complement medicines for people living with devastating inflammatory-related diseases. The classical complement pathway is a core component to the body’s immune system that activates a powerful inflammatory cascade. We believe that by stopping the classical complement pathway at its start by targeting C1q, the initiating molecule of the classical complement pathway, our approach may have the potential to provide more complete protection against complement-mediated disorders of the body, brain and eye.

Using our proprietary platform, we are identifying and characterizing the role of the classical complement pathway in three therapeutic areas—autoimmune, neurodegeneration and ophthalmology. In so doing, we are advancing a pipeline of product candidates designed to block the early classical cascade and all downstream pathway components and their tissue-damaging functions. Our goal is to suppress excessive or aberrant classical complement activity that contributes to chronic inflammation and tissue damage to slow or even halt disease progression, while preserving the beneficial immune functions of the lectin and alternative complement pathways involved in the clearance of pathogens and damaged cells. We have demonstrated robust target engagement in the body, brain and eye, and clinical proof of concept in multiple diseases, and have focused our resources on development of three priority programs:

•

Guillain-Barré Syndrome, or GBS: We are advancing our lead candidate, ANX005, an investigational, full-length monoclonal antibody, or mAb, formulated for intravenous administration as the potential first targeted treatment for patients with GBS. GBS is a rare antibody-mediated autoimmune disease that is the most common cause of acute neuromuscular paralysis, with no therapies in the United States approved by the FDA. We believe maximum suppression of C1q and the classical complement cascade early in the disease process may act to rapidly prevent complement-mediated nerve damage and irreversible neurological disability. In a prior Phase 1b placebo-controlled proof-of-concept trial, a single dose of ANX005 showed rapid and consistent improvement in muscle strength that translated into observable gains in health status, including a reduction in the need of mechanical ventilation, as well as a reduction in nerve damage and clinical function. In 2024, we completed a Phase 3 trial in 241 patients, which showed ANX005 helped patients improve sooner with rapid increase in muscle strength and more complete functional recovery than placebo through six months, and provided an important benefit in the burden of care by enabling patients to walk or be off ventilation earlier. In addition, we completed a Real World Evidence, or RWE, study that matched ANX005-treated patients from the Phase 3 study with a western world patient population from the International Guillain-Barré Syndrome Outcomes Study, or IGOS, predominantly from Europe and North America treated with current standards of care (intravenous immunoglobulin, or IVIg, or plasma exchange, or PE). Consistent with the Phase 3 trial, ANX005 showed a rapid increase in muscle strength with more complete recovery over IVIg or PE. We anticipate the Phase 3 and RWE results to support a comprehensive dataset for our Biologics License Application, or BLA, and are targeting the first half of 2025 for our pre-BLA meeting with the FDA ahead of our planned BLA submission. ANX005 has been granted Fast Track and orphan drug designation for the treatment of GBS from the FDA. ANX005 has also been granted orphan designation from the European Medicines Agency, or EMA.

•

Geographic Atrophy, or GA: We are advancing ANX007, an antigen-binding fragment, or Fab, formulated for intravitreal administration, as the first potential program with a global registration path to

approval in Europe and the United States for the treatment of dry AMD with GA. Dry AMD with GA is a leading cause of vision loss in the elderly, that affects more than an estimated eight million people globally, and there are no approved therapies targeting the preservation of vision in this disease. ANX007 is designed to block C1q locally in the eye, to provide more complete protection against excess classical complement activity and the loss of photoreceptor neurons. It is the only investigational therapy in GA to show significant vision preservation on assessments of best corrected visual acuity, or BCVA, and low luminance visual acuity, or LLVA, demonstrating significant protection from vision loss in both normal and low light conditions, as well as significant preservation of central retinal photoreceptors necessary for visual acuity as demonstrated in the Phase 2 ARCHER trial. In 2024, we initiated our Phase 3 ARCHER II trial, a global, sham-controlled, double-masked trial expected to enroll ~630 patients who have dry AMD with GA. The primary endpoint of ARCHER II is prevention of ≥15-letter loss of BCVA, and a secondary objective structural measure is prevention of ellipsoid zone (EZ) loss. The single-study program will be analyzed as two sub-studies for the U.S. in accordance with the FDA’s two-trial recommendation. Accordingly, Annexon no longer plans to conduct a second injection-controlled head-to-head Phase 3 trial. We expect to complete enrollment of ARCHER II in the second half of 2025 and report topline data in the second half of 2026. ANX007 is the first and only therapeutic candidate for the treatment of GA to receive Priority Medicine, or PRIME, designation by the EMA, which provides early and proactive support to developers of promising medicines that may offer a major therapeutic advantage over existing treatments or benefit to patients without treatment options.

•

ANX1502 for Autoimmune Indications: We are advancing ANX1502, a novel oral small molecule inhibitor of classical complement which we believe is first-in-kind. In a Phase 1 single-ascending dose, or SAD, and multiple-ascending dose, or MAD, clinical trial in healthy volunteers designed to evaluate the safety, tolerability, pharmacokinetics, or PK, and pharmacodynamics, or PD, ANX1502 was generally well tolerated across cohorts with no serious adverse events, achieved target levels of active drug and showed supportive impact on a PD biomarker of complement activity that support its advancement. We are evaluating a tablet formulation of ANX1502 in an ongoing proof-of-concept study in patients with cold agglutinin disease, or CAD, to assess PK, PD and clinical efficacy endpoints (e.g., hemolysis as measured by reduction of elevated bilirubin) and data are expected in mid-2025. Following the successful completion of the proof-of-concept study, we intend to evaluate ANX1502 in serious complement-mediated diseases, with the aim of providing enhanced efficacy and offering convenient dosing administration for long-term treatment of chronic autoimmune conditions.

Annexon was co-founded by the late Dr. Ben Barres, former member of the National Academy of Sciences, Chair of Neurobiology at Stanford University and a pioneer in complement-mediated neurodegeneration, and Dr. Arnon Rosenthal, a world-renowned scientist and industry executive. We have assembled a seasoned and accomplished management team that has been involved in the discovery, development, approval and commercialization of numerous marketed drugs, and has been studying the complement pathway and autoimmune and neurodegenerative disorders for decades. Our team is further supported by an experienced scientific advisory board, board of directors and leading healthcare investors that share our commitment to advancing transformative medicines for patients suffering from debilitating autoimmune and neurodegenerative diseases.

We hold worldwide development and commercialization rights, including through exclusive licenses, to all of our product candidates, which allows us to strategically maximize value from our product portfolio over time. Our patent portfolio includes patent protection for our upstream complement platform and each of our product candidates.

Our Pipeline

Our pipeline is led by three flagship programs focused on complement-mediated diseases of the body, brain and eye for which there is significant unmet medical need and where we have the potential to provide a first-in-class treatment opportunity. Beyond our flagship programs, our “next wave” programs are supported by a strong scientific

and clinical rationale and poised for advancement following availability of resources and ongoing evaluation of further development options. Our clinical-stage pipeline is summarized below:

In addition to our flagship programs in GBS, dry AMD with GA and ANX1502 for autoimmune indications, we continue to be encouraged by multiple “next wave” programs, which provide additional potential portfolio growth and diversification.

We have evaluated ANX005 in patients with Huntington’s Disease, or HD, and amyotrophic lateral sclerosis, or ALS, chronic neurodegenerative disorders in which aberrant classical complement activation drives neuroinflammation and has been shown to be associated with disease progression. In a completed Phase 2 clinical trial in patients with manifest HD, chronic dosing of ANX005 was generally well-tolerated, demonstrated rapid and sustained target engagement of C1q in both blood and cerebrospinal fluid, or CSF, reduced downstream complement markers in CSF, and showed promising efficacy signals on standard measures of disease progression in patients with higher levels of classical complement activity at baseline.

In a completed signal-finding open-label Phase 2a trial in patients with ALS, chronic dosing of ANX005 was generally well-tolerated, showed rapid and sustained target engagement of C1q in blood, and reduced downstream pharmacodynamic complement markers in blood. Consistent with what has been shown in other neurodegenerative diseases, including HD, exploratory analyses indicated that patients with higher baseline classical complement activation who enrolled within 12 months of diagnosis achieved better outcomes, including less functional decline on the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) and stabilization of neurofilament light chain (NfL). These analyses support a precision medicine approach to identify patients most likely to respond to anti-C1q therapy in clinical trials with recently diagnosed ALS patients who have elevated baseline levels of classical complement activity.

In addition, we have developed ANX009, a C1q-blocking Fab formulated for subcutaneous delivery, for patients with lupus nephritis, or LN, who have high baseline complement activity. LN is an autoimmune disease for which pathogenic anti-C1q antibodies, or PACAs, enhance activity and uniquely amplify kidney inflammation and damage. In a completed Phase 1b signal-finding trial, ANX009 was well tolerated, demonstrated plasma C1q target engagement and complement inhibition, and rapidly increased free/circulating PACA levels (consistent with decreased deposition in the kidney) and improved all downstream markers of complement consumption and activation (C4, as well as C3 and C5b-9).

We are evaluating options for future development of ANX005 in chronic neurodegenerative indications and ANX009 in LN.

Our Strategy

Our goal is to develop disease-modifying medicines for patients suffering from classical complement-mediated diseases of the body, brain and eye. Key elements of our strategy include:

•

Leveraging our distinct approach of inhibiting C1q and aberrant classical complement activity to address a broad range of well-characterized classical complement-mediated diseases of the body, brain and eye. By inhibiting C1q and the early classical cascade, we believe our product candidates are uniquely designed to address a wide range of antibody-mediated autoimmune diseases and complement-mediated neurodegenerative disorders. We believe full classical complement inhibition may result in clinical benefits by blocking aberrant upstream and downstream immune cell activation in our targeted indications, as well as potentially provide safety advantages by leaving the lectin and alternative pathways intact to perform their normal immune functions.

•

Prioritizing resources and execution of mid- to late-stage development of three flagship programs. By focusing our resources on our three flagship programs in GBS, GA and ANX1502, our novel oral small molecule complement inhibitor, our goal is to create near-term value for patients, physicians and stakeholders.

•

ANX005 for dry AMD with GBS: Prepare for BLA Submission and Commercialization, if approved. We are advancing ANX005 as the potential first targeted therapy for GBS, an acute neurological emergency for which there is no FDA approved treatment. ANX005 is being developed as a first-line monotherapy treatment option to address the global unmet needs of 150,000 patients annually diagnosed with GBS, in support of our goal of obtaining the first FDA-approval for the treatment of GBS. ANX005’s well-tolerated, differentiated profile showing rapid and durable improvement in muscle strength, has received both Fast Track and orphan drug designations from the FDA, as well as orphan drug designation by the EMA.

•

ANX007 for GA: Execute Global Registration Program. We are advancing ANX007 as the potential first program with a global registration path to approval for the treatment of dry AMD with GA in Europe and the United States to address the unmet needs of more than 8 million patients worldwide. ANX007’s well-tolerated, differentiated profile is the only program to show significant protection against vision loss as well as significant protection of central retinal photoreceptors necessary for visual acuity. ANX007 is the first and only therapeutic candidate for the treatment of GA to receive PRIME designation in the EU, which provides early and proactive support to developers of promising medicines that may offer a major therapeutic advantage over existing treatments or benefit to patients without treatment options.

•

ANX1502 for Autoimmune Disease: Advance First-in-Kind Oral Small Molecule Program. We are advancing an enhanced tablet formulation of ANX1502 designed to disrupt the complement-mediated autoimmune space as the potentially first orally available treatment. Following successful completion of the proof-of-concept study in patients with CAD, we intend to evaluate ANX1502 in serious complement-mediated diseases, with the aim of providing efficacy with enhanced dosing flexibility and convenience for long-term treatment of chronic autoimmune conditions.

•

Expanding our portfolio across three therapeutics franchises informed by data from our flagship programs. We intend to leverage learnings and proof-of-concept data from our flagship programs to inform selection of additional patient populations involving classical complement-mediated diseases of the body, brain and eye. As we enhance our resources, we plan to efficiently prosecute opportunities across our three therapeutic franchises utilizing our disciplined, data-driven development strategy.

•

Maximizing the value of our product candidates. We currently hold worldwide development and commercialization rights, including through exclusive licenses, to all of our product candidates. We have secured broad intellectual property protection for our upstream complement platform and intend to leverage our intellectual property and know-how to protect and enhance our leading position in developing novel therapeutics that target the classical complement cascade. We intend to pursue independent development and commercialization in indications and markets we can address with a focused sales and marketing organization. We plan to explore licensing agreements, collaborations or partnerships to advance our product candidates in indications and markets where we could accelerate and expand development and commercialization leveraging the resources of larger biopharmaceutical companies.

Overview of the Complement System and C1q Biology

The Complement System—three main complement pathways

The complement system is an integral component of the immune system that consists of many circulating and locally-produced molecules. This system evolved to enhance, or complement, other components of the adaptive and innate immune systems. The complement system, also known as the complement cascade, rapidly responds to pathogens, damaged cells and unwanted tissue components to facilitate their removal by the immune system.

There are three main complement pathways (also called cascades)—the classical, lectin and alternative pathways. Each pathway is initiated by different molecules that respond to distinct triggers. When activated, the initiating molecules set in motion a cascade of enzymatic reactions that greatly amplify, or complement, an inflammatory response. The classical pathway is initiated by C1q, which recognizes antibody complexes, specific pathogens, damaged cells or unwanted cellular components. The lectin pathway is triggered by carbohydrates on the surface of pathogens or cells. The alternative pathway amplifies the action of the other two pathways and also self-activates to eliminate pathogens or cells that are not specifically shielded by the body’s built-in self-protective systems. While these three pathways are initiated by distinct molecules, they converge downstream on common pathway components known as C3 and C5.

Aberrant activation of the complement system can result in a range of diseases characterized by an attack on healthy tissue, such as red blood cells, nerve cells or kidney components. A broad range of diseases are known to be associated with pathological activation of the complement cascade, including antibody-mediated autoimmune disorders such as GBS, CAD and lupus nephritis, and complement-mediated neurodegeneration disorders in the eye, such as glaucoma and GA, and complement-mediated neurodegeneration disorders in the brain, such as HD, ALS, frontotemporal dementia and Alzheimer’s disease. We believe intervening in the activation of the complement cascade offers a potent and selective mechanism for specifically slowing or reversing these disease processes.

Specific activated components of the complement cascade have important immune functions that contribute to three key outcomes:

•

Immune cell recruitment and inflammation. Specific activated molecules from the cascade serve as soluble signals to make blood vessels leaky and attract immune cells into tissues.

•

Directed immune cell attack. Several complement components, including C1q, bind directly to the pathogen and serve as receptors that direct immune cell attack and pathogen engulfment.

•

Membrane damage. Downstream components of the cascade directly puncture the pathogen or cell surface, causing membrane damage and lysis.

Broad potential for classical complement pathway targeted therapeutics in autoimmune and neurodegenerative diseases

The classical complement cascade has a well-established role in augmenting antibody function within the immune system. C1q recognizes antibodies bound to pathogens or cells and activates the classical pathway to trigger their removal and clearance by the immune system. C1q can also directly recognize pathogens, damaged cells or unwanted cellular components leading to similar downstream clearance. A more recent finding made by the laboratory of Dr. Ben Barres, our scientific founder, is that C1q also directly interacts with neuronal connections, or synapses, during early development. Recognition of weaker synapses by C1q triggers the classical complement cascade and directs immune cells to “prune” the synapses away from neurons, thereby reinforcing stronger synapses to establish appropriate neuronal connections.

Because of its central role in immune function, aberrant activation of C1q can lead to damage of healthy tissue and destruction of functioning synapses. We are focused on two distinct disease processes involving C1q as a key mediator of tissue damage: antibody-mediated autoimmune disease and complement-mediated neurodegeneration.

In antibody-mediated autoimmune disease, self-reactive antibodies bind to cells or tissues, activating C1q and leading to damaging inflammatory responses. In GBS, pathogenic antibodies react with components of the peripheral nerve system, or PNS, to cause widespread peripheral nerve damage and paralysis. This disease process is also evident

in antibody-mediated autoimmune disease involving blood components, such as CAD, characterized by auto-reactive antibodies that trigger destruction of red blood cells, and in a subset of patients with systemic lupus erythematosus, or SLE, where endogenous pathogenic antibodies against C1q itself drive aberrant C1q activation and are highly associated with kidney damage, or lupus nephritis.

In complement-mediated neurodegeneration, aberrant activation of C1q at synapses in aging and disease can lead to excessive synapse loss and neuronal damage, driving disease progression in multiple neurodegenerative disorders regardless of the initiating factor. In animal models, C1q accumulated on synapses with age, building up to 300-fold higher levels than in younger animals. It did not activate with normal aging, but other inflammatory stimuli, including misfolded proteins, metabolic dysfunction or increases in intraocular pressure, appeared to aberrantly reactivate C1q’s developmental role in synapse elimination. Complement activation and aberrant synapse pruning in disease may lead to neuroinflammation, loss of synaptic neuronal connections and neurodegeneration. In support of this hypothesis, we and other investigators have observed that C1q inhibition was protective in numerous models of neurodegenerative disease, including diseases of the eye, such as glaucoma and age-related macular degeneration, chronic diseases of the CNS, such as frontotemporal dementia, Alzheimer’s, HD and Spinal Muscular Atrophy, or SMA, and acute injury, such as traumatic brain injury and stroke.

Our differentiated approach to treating complement-mediated autoimmune and neurodegenerative disease through inhibition of C1q

We believe that in order to selectively inhibit aberrant activation of the classical complement pathway implicated in driving certain complement-mediated autoimmune and neurodegenerative diseases, it is important to target the early components of the classical cascade, particularly C1q, C4 and C3. Activated fragments of C4 and C3 induce vascular leakiness and immune cell recruitment into the tissue, while other fragments of C4 and C3, as well as C1q, work together to direct immune cell attack to the cell or synapse surface. Furthermore, C1q inhibition blocks downstream classical pathway activation of C5 and its membrane damaging effects. We believe that inhibition of C1q does not block the activity of these components in the lectin or alternative complement pathways, and both of these pathways will continue to perform their normal immune functions.

Our Platform

Our novel upstream complement platform is designed to completely inhibit classical complement activity for the treatment of antibody-mediated autoimmune diseases and complement-mediated neurodegenerative diseases in the body, brain and eye. We believe there are potential advantages to our approach of upstream inhibition of the classical complement cascade, which include:

•

Full inhibition of the classical cascade while preserving healthy immune function of the other complement pathways. Inhibition of C1q fully inhibits the classical cascade, including components downstream of C1q such as C4, C3, C5 and the downstream membrane attack complex. As a result, we believe our approach is designed to block all classical complement activity that can contribute to disease pathology, including immune cell recruitment, directed immune cell attack and membrane damage. By targeting upstream tissue-damaging components of the classical complement pathway, our approach leaves the lectin and alternative pathways to perform their normal immune function, which may aid both clinical improvement and safety. Our approach is also distinct from inhibiting C3 or C5. Inhibition of C5 will not affect the upstream components of the classical pathway involved in pathology (C1q, C4 and C3), while inhibition of C3 will block downstream components in all three complement pathways.

•

Broad applicability across many indications. We believe our approach has broad utility for the treatment of diseases in which full inhibition of the entire classical complement cascade may be beneficial. We believe our approach is distinguishable from those that target only downstream complement components. Our initial indications represent our beachhead within antibody-mediated autoimmune and

complement-mediated neurodegenerative diseases, and we will selectively pursue both orphan and larger patient population diseases with clear biological evidence of classical complement activation.

Our Flagship Programs

Guillain-Barré Syndrome

Overview of Guillain-Barré Syndrome

Guillain-Barrésyndrome (GBS) is a serious and life-threatening condition that continues to be associated with significant long-term morbidity and mortality in patients despite use of IVIg treatment as standard of care. GBS is a rare disease, but is also the most common, most severe, and well understood acute paralytic inflammatory disease of the peripheral nervous system. GBS generally occurs post-infection in otherwise healthy persons. Antibodies generated against an infectious agent cross-react with components of peripheral nerves, leading to a complement mediated attack on nerve components, including myelin sheath and axonal tissue. The ensuing peripheral nerve damage is acute and rapidly progressive, leading to acute severe paralysis, significant morbidity, disability and mortality. The neuronal destruction progresses until titers of the cross-reactive, complement-activating antibodies have diminished (van den Berg et al., 2014). GBS impacts approximately 150,000 people annually worldwide, 22,000 in the United States and EU, and 7,000 are hospitalized each year in the United States. The prevalence of GBS continues to increase with advancing age. In 2004, the annual economic cost of GBS in the United States was $2 billion, largely due to the permanent disability and mortality it can cause.

There are currently no FDA-approved or targeted therapies for the treatment of GBS. Treatment guidelines published by the American Academy of Neurology recommend early initiation of IVIg or plasma exchange in patients diagnosed with GBS. Although IVIg and plasma exchange are the established standards of care in the western world and parts of Asia, significant unmet need still exists, and many patients, despite receiving the standard of care, are left with residual neurological disability, accompanied by chronic pain and fatigue.

The clinical course of GBS usually involves rapidly progressive weakness in the limbs culminating in neuromuscular paralysis within two to four weeks of onset. According to 2011 estimates, 20 to 30% of patients require mechanical ventilation, over 20% have permanent motor or sensory disability and 2 to 20% of cases result in death globally. Many patients with GBS require extensive monitoring and supportive care and will seek treatment in a hospital within a few days of onset of the disease. Because approximately a quarter of patients need artificial ventilation due to respiratory muscle weakness, and many develop autonomic disturbances, admission in an intensive care unit is frequently necessary. Symptoms peak within four weeks as the auto-antibody response declines, followed by a recovery period that can last months or years, as the nervous system repairs itself. The development of targeted treatments for GBS is crucial to improve outcomes and quality of life for those affected by this debilitating condition.

C1q is a key driver of pathogenesis in GBS

GBS is an acute, autoimmune disease driven by antibodies that lead to activation of the classical complement cascade. Pathological nerve-targeting auto-antibodies, which may be triggered by an infection, lead to the activation of C1q and the classical complement cascade. Studies have shown that pathogenic auto-antibodies are present in the serum and CSF, and that activated components of the complement cascade are deposited on peripheral nerve tissue from GBS patients. Peripheral nerve roots are immersed in CSF as they emerge from the spinal cord and are prominent sites of damage in GBS. The figure below illustrates the activation of the classical complement pathway within peripheral nerves in GBS patient samples from autopsy. The left image shows a low magnification view of a peripheral nerve with numerous individual nerve fibers coated with membrane-damaging complement activation products (C5b-9; dark staining). The middle image shows a high magnification view of an individual nerve fiber with deposition of C3d (dark staining), a complement activation product that directs immune cell attack. The right image shows a highpower image of an individual nerve fiber being probed by an infiltrating immune cell (macrophage).

We believe that by blocking the activity of C1q early in the onset of the disease, we can minimize the neuronal damage caused by these pathogenic auto-antibodies, in turn reducing the patients’ symptoms and accelerating their neurological recovery.

ANX005 Development Background in GBS

Since 2015, we have developed ANX005 as the potential first targeted therapy for patients with GBS, an acute neurological emergency for which there is no FDA approved treatment. ANX005 is being developed as a first-line monotherapy treatment option to address the unmet needs of GBS patients and healthcare providers, leveraging our expertise and leadership in classical complement-mediated diseases. A robust data package has been generated over the nine year development path that includes a placebo-controlled Phase 1b trial that established POC for ANX005 as a first-line treatment for GBS, a successful Phase 3 trial showing that ANX005 was generally well-tolerated and resulted in faster and more complete functional recovery versus placebo, a RWE study that showed improved outcomes against current standards of care in matched patient populations, and a drug-drug interaction study with ANX005 and IVIg strengthening the safety profile for ANX005 in GBS. Importantly, to ethically provide a placebo-controlled dataset, Annexon conducted ANX005’s clinical development for GBS outside of the U.S. in jurisdictions where IVIg treatment is not readily available. In addition, Annexon has generated real-world evidence to support the generalizability of ANX005 to a matched Western patient population and compared ANX005 treatment outcomes from a single infusion of ANX005 versus standard of care IVIg given as a 5-day infusion or PE.

We have closely coordinated our clinical efforts with leading researchers of the International GBS Outcome Study, or IGOS, in pursuing a novel therapy for GBS. With the goal of aiding the development of effective treatments for GBS, practitioners established IGOS in May 2012, and have collected natural history data from 2,000 GBS patients worldwide. IGOS is a prospective, observational, multicenter cohort study that aims to identify the clinical and biological determinants and predictors of disease onset as well as the subtype, course and outcome of GBS. IGOS was established to help develop a better understanding of the mechanism of disease progression and recovery and to conduct selective therapeutic trials to improve patient outcomes. This natural history database is an invaluable resource to clinical development, facilitating the design of clinical trials, optimal selection of endpoints, and patient follow-up for one to three years. We initiated our GBS clinical development in Bangladesh, a country where the incidence of GBS is several times higher than in North America and Europe and where 17% of patients die from the disease and 20% suffer permanent disability and are unable to walk. Additionally, our site in Bangladesh is well situated to conduct clinical research in GBS in a manner compliant with good clinical practice, or GCP, requirements.

Phase 1b Trial of ANX005 in GBS

We conducted a Phase 1b placebo-controlled, dose escalation trial (n=50) of ANX005 in GBS patients at a tertiary care hospital in Bangladesh, in compliance with GCP as described above. The trial objectives included safety and tolerability, dosing levels and target engagement, and included a follow up of eight weeks. The dosing levels of ANX005 delivered in this trial ranged from 3 mg/kg to 75 mg/kg. ANX005 was well tolerated, and no drug-related serious adverse events or drug-related discontinuations occurred. The most common adverse events were acute infusion-related reactions, or IRRs, which occurred in the majority of patients and presented as low grade, non-serious, transient skin rash. These acute IRRs were mitigated by standard anti-inflammatory pre-medications.

Results from the Phase 1b trial showed increasing serum levels of ANX005 and its duration in the circulation at increasing dose levels, and that the drug was present in the serum for up to three weeks at a dose of 75 mg/kg. When ANX005 was present in the circulation C1q function was fully inhibited, and rapidly returned to normal levels as ANX005 serum levels declined.

Much of the proximal weakness in GBS patients is due to involvement of peripheral nerve roots that are immersed in CSF as they exit the spinal cord. Hence, we believe product candidate levels and target inhibition in CSF may be an important contributor to efficacy. We observed that ANX005 entered the CSF of GBS patients treated with doses of 18-75 mg/kg of ANX005, resulting in full engagement of C1q inhibition in the CSF.

In the Phase 1b trial in GBS patients, ANX005 treatment at doses that engaged C1q in both serum and CSF (i.e., 18-75 mg/kg dose) resulted in a statistically significant early decline in serum NfL levels compared to placebo (two to four-week post treatment p-value <0.05). In this Phase 1b trial, we also explored the administration of ANX005 on multiple validated clinical disability measures including GBS-Disability Score, or GBS-DS, Medical Research Council Muscle Strength Scale, or MRC, and Inflammatory Rasch-built Overall Disability Scale, or I-RODS, over an eight-week period. We observed that early decline in NfL correlated with improvement in the GBS-DS at the end of the study (two to eight-week post treatment p-value <0.05). We believe these results suggest that ANX005 had a rapid impact on the disease process by ameliorating antibody-induced nerve damage, likely within the first two weeks of dosing.

Though the trial was not powered for statistical significance, treatment with ANX005 resulted in consistent, positive numerical trends, including an improvement in MRC score and the number of days of ventilation. We observed a dose-dependent trend for improvement in MRC within the first week of treatment.

Early improvement in MRC is known to have strong prognostic implications on long-term functional recovery (modified Erasmus GBS Outcome Score). In line with this published data, we found that early improvement in MRC correlated with patients’ disability scores at the end of the Phase 1b trial (GBS-DS at week eight). This result is important because GBS-DS is typically used as the primary endpoint in GBS registrational studies. In addition, using a responder analysis, 28% of patients treated with high dose ANX005 (18-75 mg/kg) improved by at least three points on GBS-DS by week eight compared to 0% of placebo-treated patients.

Following the completion of the Phase 1b treatment cohorts (through 75 mg/kg), two unblinded exploratory cohorts were enrolled to establish higher dose and multiple dose safety and PK/PD to inform subsequent chronic dosing trials. These two exploratory cohorts were a single dose of 100 mg/kg, and two doses of 75 mg/kg separated by one week (150 mg/kg total). At these higher dose levels, ANX005 was well-tolerated, and no drug-related serious adverse events or drug-related discontinuations occurred; moreover, we did not reach a maximum tolerated dose. Similarly, we observed full inhibition of C1q in serum and CSF, a reduction in NfL and trends of improvement in clinical measures when compared to placebo; however, there was no additional impact on these clinical measures beyond that seen at 75 mg/kg.

The results of the Phase 1b dose-ranging trial in GBS showed that ANX005 was well-tolerated, fully inhibited C1q in the blood and CSF at target doses, and demonstrated an early reduction in NfL levels. Drug treatment was associated with a trend for early improvement in MRC, and early changes in MRC significantly correlated with improved clinical measures in GBS patients. An additional key learning from the study is the importance of using baseline MRC for patient stratification at the time of hospitalization and study entry. Accounting for baseline MRC strengthened the impact of ANX005 treatment in the biomarker and clinical measures, demonstrating that MRC will be an important stratification tool in future GBS trials.

Phase 3 Trial of ANX005 in GBS

Based on the positive findings from our Phase 1b trial, we conducted a randomized, double-blind, placebo-controlled, multi-center Phase 3 trial to evaluate the efficacy, safety, pharmacokinetics and pharmacodynamics of ANX005 administered by a single intravenous, or IV, infusion. The Phase 3 trial enrolled 241 patients in Bangladesh and the Philippines diagnosed with GBS according to the National Institute of Neurological Disorders and Stroke Diagnostic Criteria for Guillain-Barré Syndrome at the onset of GBS-related weakness ≤10 days prior to the start of

treatment. Patients were stratified for leading prognostic factors including muscle strength and time from symptom onset.

In June 2024, we presented topline results from the Phase 3 trial demonstrating that a single infusion of ANX005 at 30 mg/met the trial’s primary endpoint of a meaningful improvement in GBS-disability scale at week 8. Specifically, ANX005 30 mg/kg achieved a highly statistically significant 2.4-fold improvement on the GBS-DS (p = 0.0058), utilizing a proportional odds methodology to assess the proportion of patients who shift to better outcomes on the GBS-DS with ANX005 treatment compared to placebo at week 8. ANX005 30 mg/kg treatment also demonstrated improvements versus placebo on key secondary endpoints, including early gains in muscle strength by Medical Research Council (MRC) sum score at day 8 (p <0.0001*) and at week 8 (p = 0.0351*), and a median of 28 fewer days on artificial ventilation through week 26 (p = 0.0356*). Additionally, ANX005 30 mg/kg demonstrated a 31-day reduction in the median time to walk independently versus placebo (p = 0.0211*) in a prespecified analysis. ANX005 30 mg/kg treated patients got better sooner on each of these assessments, presenting important clinical care outcomes for patients and the healthcare community.

* nominal p-values

The Phase 3 trial evaluated two doses of ANX005, 30 mg/kg and 75 mg/kg, both of which delivered rapid and complete suppression of complement activity but differed in duration of C1q inhibition. The 30 mg/kg dose suppression lasted one week and the 75 mg/kg dose suppression lasted two to three weeks. ANX005 75 mg/kg outperformed placebo on multiple endpoints; however, it was not statistically significant on the primary endpoint of GBS-DS at week 8 (p = 0.5548). The two dose levels were evaluated based on findings in the earlier Phase 1b proof-of-concept study, which showed efficacy in pooled analysis of both shorter and longer duration of ANX005 C1q inhibition. Because classical complement drives tissue damage in the early phase of disease, while facilitating nerve repair after acute nerve injury, the strong positive Phase 3 results with the 30 mg/kg dose resulting in one week of C1q inhibition appeared to define the optimal treatment window.

The clinical safety and tolerability findings of ANX005 at both doses in the Phase 3 study support a generally well-tolerated profile with no new safety signals. The majority of adverse events were mild Grade 1 to moderate Grade 2 events. The most common treatment-related adverse events were infusion related reactions (30.4%) that were mostly mild transient rashes. There were no autoimmune related adverse events, and no drug-related deaths or serious infections were observed.

Real World Evidence Study of ANX005 in GBS

All of our studies to date for ANX005 in GBS have been conducted at sites outside the United States. To support these clinical trials and based on feedback from the FDA, we conducted a RWE study in collaboration with IGOS investigators to establish comparability between Phase 3 participants and western patients.

IGOS investigators and we established a cohort of 79 real-world patients from the IGOS global patient registry that was matched based on key prespecified prognostic factors to the cohort of 79 patients treated with ANX005 30 mg/kg from our completed Phase 3 study. Patients in the ANX005 Phase 3 population had moderate to severe disease, and the matching level demonstrates that the Phase 3 population is represented within the global GBS patient spectrum captured in IGOS.

This RWE study also provided the first insights comparing ANX005 with the standard of care IVIg or PE. Patients treated with ANX005 showed faster and greater improvement in muscle strength and disability compared to patients in the matched IGOS cohort treated with IVIg or PE. The comparison also showed that fewer patients treated with ANX005 required mechanical ventilation. Further, ANX005-treated patients were observed to spend less time on ventilation and less time in the intensive care unit, or ICU. These findings indicate that ANX005 may decrease the overall burden of GBS care.

Some key findings comparing ANX005 30 mg/kg to IVIg or PE included:

•

By week 1, patients treated with ANX005 showed more than 10-point improvement in muscle strength over patients treated with IVIg or PE, a clinically meaningful benefit as measured by MRC sumscore and an indicator for future recovery potential (p < 0.0001).

•

Patients treated with ANX005 were approximately twice as likely to be in a better state of health than patients on IVIg or PE on the GBS-DS at multiple timepoints throughout the study, including at week 8, the primary endpoint for the Phase 3 trial (p = 0.0459).

•

Approximately half the number of patients treated with ANX005 (n=15 of 79) required mechanical ventilation compared with patients treated with IVIg or PE (n=32 of 79) (p = 0.022).

•

ANX005-treated patients were observed to spend fewer days on mechanical ventilation and fewer days in the ICU (median of 12 fewer days for each measure, p = n.s.).

Together, we believe the Phase 3 trial and RWE study demonstrate consistent, robust effects of ANX005 treatment in support of a potential U.S. BLA. ANX005 has received both Fast Track and orphan drug designations from the FDA as well as orphan designation by the EMA for the treatment of GBS. The EMA orphan designation was based on an indirect comparison between ANX005 and IVIg that demonstrated a notable and early improvement in muscle strength with ANX005 versus patients treated with IVIg, which translated into observable gains in health status, including a reduction in the need of mechanical ventilation.

Geographic Atrophy

Overview of Geographic Atrophy

GA is an advanced form of dry age-related macular degeneration (AMD), an eye disease that is the leading cause of blindness in the elderly. GA is a chronic progressive neurodegenerative disorder of the retina involving the loss of photoreceptor synapses and cells in the outer retina. GA affects an estimated one million people in the United States and eight million people globally, severely limiting their independence and causing frustration, anxiety and emotional hardship. Effective treatments that preserve vision are still needed, as no currently approved therapies have been shown in clinical trials to significantly prevent vision loss.

Role of C1q and Complement in Geographic Atrophy

Genome-wide association studies have strongly implicated multiple components of the complement cascade in AMD and geographic atrophy. For example, specific alleles of the gene for C3 can increase the likelihood of developing AMD by 50%. Histopathological investigations have also observed the presence of complement components in geographic atrophy. These studies largely point to a role of excessive C3 activity in disease, but do not indicate how C3 is being activated (classical, lectin or alternative pathways). We have identified a potential dual role of C1q and the classical cascade as an important complement-activating system in geographic atrophy. First, we found that C1q strongly accumulated on photoreceptor cell synapses with normal age or disease, as shown below (left panel), implicating C1q’s role in excessive synapse pruning and complement-mediated neurodegeneration. Second, C1q and C1q ligands, such as C-reactive protein, also accumulated in the retina below photoreceptor cells in association with drusen (extracellular membrane and protein debris associated with geographic atrophy; right panel). These results suggest that the photoreceptor neurons and pigmented retinal epithelial cells – cell types that are both lost in GA – are sandwiched between deposits of C1q and that the classical complement cascade may have an ongoing and pathogenic role in GA by activating C3.

In support of this hypothesis, we found that either deletion or pharmacologic inhibition of C1q was protective in an animal model of photoreceptor neuron loss induced by photo-oxidation, as shown below. Further, components of the classical complement cascade have been associated with photoreceptor cells in human GA tissue (C4 and C3) and implicated in photoreceptor cell targeting with an in vitro assay. Finally, C1q is locally produced within the retina during disease by infiltrating immune cells, indicating that its pathogenic role may be amenable to local inhibition of C1q. As described above, we believe inhibition of C1q would block all key components of the classical cascade, including C1q, C4, and C3 involved in immune cell attack and synapse pruning, as well as C5 involved in direct membrane damage.

C1q inhibition was shown to be protective of photoreceptor cells and retinal function in a model of photoreceptor cell damage induced by light.

Phase 1b Trial of ANX007 in Glaucoma to Support Development in GA

We completed single-ascending dose (n=9) and sham-controlled multiple dose (n=17) studies of intravitreal ANX007 in patients with glaucoma to evaluate safety, tolerability, pharmacokinetics and target engagement. These patients had aqueous humor taps so that ocular fluid could be analyzed for levels of ANX007 and free C1q immediately prior to first dose (day 1) and prior to second dose (day 29). The studies showed that ANX007 was well-tolerated at all doses (1 mg, 2.5 mg and 5 mg) and achieved complete suppression of C1q at 2.5 mg and 5 mg.

Phase 2 ARCHER Trial of ANX007 in GA

We conducted the randomized, multi-center, double-masked, sham-controlled Phase 2 ARCHER trial to compare the safety and efficacy of ANX007 in patients with GA secondary to AMD. The study enrolled a total of 270 patients, stratified by GA lesion size, location and choroidal neovascularization, or CNV, in the fellow eye at the time of enrollment. Patients were nearly equally split between foveal (49.4% to 57.3%) and non-foveal groups, had an average age of 80 years and were balanced between female and male. Ninety-six percent of patients enrolled were from the United States. Patients were randomized to receive an intravitreal dose of 5mg ANX007 monthly (n=89), 5mg ANX007 every other month (n=92) or sham monthly or every other month (pooled n=89) for a treatment period of 12 months, followed by a six-month off-treatment period.

The primary outcome measure of the study was the rate of change in GA lesion growth (slope) from baseline as measured by fundus autofluorescence through 12 months for the study eye. The study included multiple pre-specified visual function measures to assess the effects of ANX007 on vision: change from baseline in BCVA; change from baseline in low-luminance best corrected visual acuity; and change in baseline from low-luminance visual acuity deficit, or LLVD.

In the Phase 2 ARCHER trial, ANX007 demonstrated consistent protection against vision loss in a broad population of patients with GA. Specifically, topline data from the Phase 2 ARCHER trial reported in May 2023 and presented at the American Society of Retina Specialists Annual Meeting in July 2023 showed that ANX007 provided significant, time and dose-dependent protection from vision loss in patients with GA, measured by BCVA ≥ 15-letter loss, the widely accepted and clinically meaningful functional endpoint assessing visual acuity.

Monthly treatment with ANX007 demonstrated nominally statistically significant reduction in BCVA ≥15-letter loss (p=0.0021) compared to sham. The persistent ≥15-letter BCVA loss through month 12 hazard was reduced 72% in the monthly arm (p=0.006) and 48% in the every other month arm (p=0.064). Protection from vision loss was also shown in multiple additional prespecified measures of BCVA and visual function, including in standard and low light conditions. Protection from vision loss was enhanced in a subpopulation of patients with less advanced disease defined by LLVD < 30 at baseline and in patients with more intact vision as defined by <80% ellipsoid zone, or EZ, loss. ANX007’s treatment effect increased over the course of the on-treatment portion of the study, suggesting that ANX007 may provide a growing and durable treatment effect over time. While benefit gained against vision lost was maintained during the subsequent six-month off-treatment period, the rate of decline for BCVA ≥ 15-letter vision began to parallel that of sham, providing additional support for the observed on-treatment protection.

While the primary endpoint of mean rate of change (slope) in GA lesion area compared to sham at 12 months did not reach statistical significance, greater impact on retinal pigment epithelium loss was observed in the second six months of treatment versus the first. Consistent with its proposed mechanism, ANX007 reduced photoreceptor EZ loss and showed more pronounced effect in reducing total EZ loss and protection of photoreceptors in the central fovea that are associated with visual acuity.

ANX007 treatment was generally well-tolerated, with no increase in CNV rates between the treated and sham arms and no events of retinal vasculitis reported.

Phase 3 Program of ANX007 in dry AMD with GA

In 2024, we initiated the Phase 3 ARCHER II trial, a global, sham-controlled, double-masked trial enrolling approximately 630 patients who have dry AMD with GA. The single-study program will be analyzed as two sub-studies in the U.S. in accordance with the FDA’s two-trial recommendation. The primary endpoint of ARCHER II is prevention of ≥15-letter loss of BCVA, and an objective secondary objective structural measure is prevention of EZ loss. Accordingly, Annexon no longer plans to conduct a second injection-controlled head-to-head Phase 3 trial.

ANX007 is the first therapeutic candidate for the treatment of GA to receive PRIME designation by the EMA, which provides early and proactive support to developers of promising medicines that may offer a major therapeutic advantage over existing treatments or benefit to patients without treatment options.

ANX1502

Overview of ANX1502

ANX1502 is a novel small molecule inhibitor of classical complement designed for oral administration in a range of chronic autoimmune diseases. ANX1502 converts to the active compound, ANX1439, on administration and delivers a highly potent and selective inhibitor of the activated form of C1s—part of the C1 complex that initiates the classical pathway. The active compound has been shown to have a high affinity to C1s and demonstrate a robust functional inhibition of the classical pathway.

Role of C1s in Complement-Mediated Autoimmune Diseases

The C1 complex is responsible for the activation of the classical pathway and is comprised of C1r, C1s and C1q. As part of the disease process, once activated, C1s is responsible for cleaving C4 and C2, key amplification components of the classical cascade. We believe that by stopping C1s from cleaving C4 and C2 with ANX1502, we will be able to block the classical cascade to reduce levels of inflammation, slow disease progression and potentially impact disease outcomes for patients.

Phase 1 SAD/MAD Trial of ANX1502

We completed the randomized, double-blind, placebo-controlled Phase 1 SAD/MAD trial of ANX1502 to assess the safety, tolerability, PK and PD of ANX1502 liquid suspension formulation in healthy adults. The study evaluated single ascending doses of ANX1502 ranging from 25 mg to 1050 mg (6 patients treated with ANX1502 plus 2 placebo subjects per cohort) and multiple ascending doses of ANX1502 ranging from 200 mg twice-daily to 525 mg twice-daily (9 patients treated with ANX1502 plus 3 placebo subjects per cohort).

In the SAD/MAD study, dose-proportional PK and targeted levels of active drug were observed across both cohorts, and single doses of 525-1025 mg ANX1502 suppressed C4d serum levels in healthy volunteers with higher than median baseline C4d. Across all doses evaluated, ANX1502 was generally well tolerated with mild to moderate treatment-emergent adverse events (TEAEs), which included gastro-intestinal events such as nausea, emesis and diarrhea. No serious adverse events were reported, and there were no significant clinical or lab findings.

Ongoing Development of ANX1502 in Autoimmune Diseases

We are evaluating a tablet formation of ANX1502 in an ongoing open-label, single arm POC study in patients with CAD for up to four weeks to assess tolerability, pharmacokinetics, pharmacodynamic and clinical efficacy endpoints (e.g., hemolysis as measured by reduction of elevated bilirubin). Enteric coated tablets allow flexible dosing 4-5-times above target concentrations of 100nM for rigorous testing in CAD, a classical complement-mediated disease. Three patients have been enrolled to date with observed reduction in key clinical and biomarker outcomes consistent with complement inhibition. Data in up to seven patients are expected in mid-2025.

Following the successful completion of the proof-of-concept study, we intend to evaluate ANX1502 in serious complement-mediated diseases, with the aim of providing enhanced efficacy and offering convenient dosing administration for long-term treatment of chronic autoimmune conditions.

Our Next Wave Programs

ANX005 for Huntington’s Disease

We completed a Phase 2 trial of ANX005 in patients with HD (28 patients were enrolled with safety data measured from all 28 patients and efficacy data measured from 23 patients that completed both six-months of treatment and subsequent three-month follow-up period), which showed that treatment with ANX005 was generally well-tolerated, with full target engagement of C1q in both serum and CSF observed throughout the six-month treatment period and well into the three-month follow-up period. Disease progression stabilized for the entire nine months of the study, as assessed by both Composite Unified Huntington's Disease Rating Scale, or cUHDRS, and Total Functional Capacity, or TFC, the two primary clinical measurement scales for HD. Additionally, HD patients with higher baseline complement activity, as measured by elevated levels of C4a/C4 in CSF, demonstrated a rapid clinical benefit as early as week 6, as assessed by both cUHDRS and TFC, that was sustained over the entire nine months of the study. Plasma and CSF NfL levels remained generally consistent through the nine-month study and were comparable to NfL levels described in published natural history data for HD patients. Based on these findings and productive engagement with the FDA, we are assessing opportunities for late-stage development of ANX005 in HD.

ANX005 for ALS

We completed a Phase 2a signal-finding trial evaluating ANX005 in patients with ALS, designed to assess safety, tolerability, and target engagement (13 patients were enrolled and treated for 12 weeks, of which 7 patients continued on treatment for 24 weeks). Chronic dosing of ANX005 was generally well-tolerated, showed rapid and sustained target engagement of C1q in blood, and reduced downstream pharmacodynamic complement markers in blood. Consistent with what has been shown in other neurodegenerative diseases, including HD, exploratory analyses indicated that patients with higher baseline classical complement activation who enrolled within 12 months of diagnosis achieved better outcomes, including less functional decline on the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) and stabilization of neurofilament light chain (NfL). These analyses support a precision medicine approach to identify patients most likely to respond to anti-C1q therapy in clinical trials with recently diagnosed ALS patients who have elevated baseline levels of classical complement activity.

ANX009 for Lupus Nephritis

ANX009, an investigational C1q Fab formulated for subcutaneous delivery, which was most recently evaluated in a Phase 1b signal-finding trial using a precision medicine approach for patients with lupus nephritis (LN) who have high baseline complement activity. LN is an autoimmune disease for which pathogenic anti-C1q antibodies (PACAs) enhance activity and uniquely amplify kidney inflammation and damage. We designed ANX009 with a goal of enabling chronic dosing for patients with antibody-mediated autoimmune disorders where anti-C1q may have a disease-modifying effect and where we can utilize our targeted biomarker-driven approach. In a first-in-human clinical trial, ANX009 was well-tolerated (7 patients were enrolled, of which 6 patients completed treatment) at all dose levels tested and no drug-related safety signals were observed. The trial showed that ANX009 led to sustained C1q inhibition at multiple doses, supporting the potential for twice-weekly subcutaneous administration with the current formulation, and advancement into the Phase 1b signal-finding trial for patients with LN.

Initial results from the Phase 1b trial were presented at the American Society of Nephrology’s Kidney Week 2023 conference, which showed subcutaneous ANX009 was well tolerated and demonstrated plasma C1q target engagement and complement inhibition. Importantly, inhibition of C1q rapidly increased free/circulating PACA levels (consistent with decreased deposition in the kidney) and improved all downstream markers of complement consumption and activation (C4, as well as C3 and C5b-9). These results indicate that C1q and the classical pathway are key drivers of complement activation in LN, independent of the alternative and lectin pathways, and that PACAs are a component of the classical complement activation pathway. Consistent with the short duration of this signal-finding study (3 weeks), changes in urinary protein excretion were not observed as anticipated. We are evaluating options for future development of ANX009 in LN.

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 candidates, new therapeutic approaches and potential indications, and other inventions that are important to our business. Our policy is to seek to protect our proprietary and intellectual property position by, among other methods, filing U.S. and foreign patent applications related to our proprietary technology, inventions and improvements that are important for the development and implementation of our business. 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 generally 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.

Our patent portfolio includes patents and patent applications that are licensed to us in whole or in part from a number of partners, including Stanford University and the University of California, and patents and patent applications that are owned by us. Our proprietary technology has been primarily developed by in-house research and development programs, and to a lesser extent through acquisitions, relationships with academic research centers and contract research organizations.

For our product candidates, we will, in general, initially pursue patent protection covering compositions of matter and methods of use. Throughout the development of our product candidates, 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.

As of February 10, 2025, our patent portfolio, including patents licensed from our partners, comprised 18 different patent families filed in various jurisdictions worldwide. Our patent portfolio includes issued patents and patent applications in the United States and in other jurisdictions.

One patent family, which we exclusively license from Stanford University, includes nine granted U.S. patents covering various methods of treating neurodegeneration and related medical conditions by inhibiting the C1 complex or its components, such as by using an anti-C1q antibody. The U.S. patents in this family include claims covering uses of ANX005, ANX007 and ANX009. These U.S. patents will expire between 2026 and 2030, absent any additional disclaimers, extensions or adjustments of patent term. There are no pending applications or foreign patents in this family.

Two other patent families, which we own, are directed to anti-C1q antibodies and methods of using them. These families include six granted U.S. patents, two pending U.S. patent applications, 30 granted foreign patents and eight pending foreign patent applications. The patents in these families cover ANX005, ANX007 and ANX009. These patents will expire between 2034 and 2037, absent any additional disclaimers, extensions or adjustments of patent term.

Other patent families that we own include:

•

two granted U.S. patents, one pending U.S. patent application, eight granted foreign patents, and nine pending foreign patent applications. The patents in this family include claims directed to ANX007 and will expire between 2036 and 2038, absent any additional disclaimers, extensions or adjustments of patent term;

•

one pending PCT application. The pending PCT application in this family includes claims covering a pharmaceutical formulation comprising anti-C1q antibodies, including ANX005, ANX007 and ANX009. Patents that may be issued from this family would expire in 2043, absent any disclaimers, extensions or adjustments of patent term;

•

one granted U.S. patent, one pending U.S. patent application, and 37 pending foreign patent applications. The granted U.S. patent in this family includes claims covering certain small molecule modulators of the classical pathway, including ANX1502. This patent will expire in 2041, absent any additional disclaimers, extensions or adjustments of patent term. Patents that may be issued from these applications would expire in 2041, absent any disclaimers, extensions or adjustments of patent term; and

•

one pending U.S. patent application and 16 pending foreign applications. The pending U.S. patent application in this family includes claims covering certain small molecule modulators of the classical pathway. Patents that may be issued from this family would expire in 2043, absent any disclaimers, extensions or adjustments of patent term.

Our patent portfolio also includes ten patent families, owned by us solely or jointly with the University of California or The J. David Gladstone Institutes or Fondazione Telethon and Universita’ degli Studi di Trento, directed to the treatment of certain medical conditions using anti-C1q antibodies, including ANX005, ANX007 and ANX009. These families include nine pending U.S. patent applications, three granted foreign patents, and 84 pending foreign patent applications. Patents that may be issued from these applications would expire between 2034 and 2043, absent any disclaimers, extensions or adjustments of patent term.

Exclusive (Equity) Agreement with The Board of Trustees of the Leland Stanford Junior University

In November 2011, we and The Board of Trustees of the Leland Stanford Junior University, or Stanford, entered into an exclusive licensing agreement, or the Stanford Agreement. Under the Stanford Agreement, Stanford granted to us an exclusive, worldwide, royalty-bearing, sublicensable license, under certain patent rights, or the Licensed Patents, to make, use, offer for sale, sell, import and otherwise commercialize products covered by the Licensed Patents for human or animal diseases, disorders or conditions. We are required to meet certain development and funding milestones for the licensed products.

Under the Stanford Agreement, we are obligated to pay Stanford an upfront payment, license maintenance fees ranging from the single digit to tens of thousands of dollars per year, and milestone payments totaling up to $675,000. We also agreed to make royalty payments at a rate equal to a low single-digit percentage of worldwide net sales of licensed products and a portion of certain sublicensing income we receive from sublicensees at a rate in the low double digit percentages, subject to a specified maximum total payment.

Additionally, in accordance with the terms of the Stanford Agreement, upon closing our first financing event that raised at least $2.0 million, we granted Stanford $150,000 in shares of our redeemable convertible preferred stock, which were automatically converted into shares of our common stock prior to the completion of the initial public offering, or IPO, in July 2020. We may also have to pay a fee to Stanford if we assign our rights under the Stanford Agreement to a third party.

We may terminate the Stanford Agreement in its entirety, or as to a particular Licensed Patent or licensed product, for convenience on thirty days’ prior written notice. Stanford may terminate the Stanford Agreement for our breach that remains uncured for forty-five days or if we provide any false report, are delinquent on any report or payment, fail to achieve a milestone or fail to diligently develop and commercialize a licensed product.

Patent Term and Term Extensions

Generally, utility patents issued for applications filed in the United States are granted a term of 20 years from the filing date of the earliest non-provisional patent application to which a claim of priority is made. In addition, in certain instances, the term of a U.S. patent can be extended to recapture a portion of any delay caused by the United States Patent and Trademark Office, or USPTO, in issuing the patent, as well as a portion of the term of a granted patent that is effectively lost as a result of the FDA regulatory review period. However, as to the FDA component, the restoration period cannot be longer than five years and the restoration period cannot extend the patent term beyond 14 years from FDA approval for the product covered by that patent. In addition, only one patent applicable to an approved drug may receive the extension, and the extension applies only to coverage for the approved drug, methods for using it and methods of manufacturing it, even if the claims cover other products or product candidates. Where one patent covers multiple products or product candidates, it may only receive an extension for one of the covered products; any extension related to a second product or product candidate must be applied to a different patent. The duration of foreign patents varies in accordance with provisions of applicable local law, but typically is also 20 years from filing date of the earliest non-provisional patent application to which a claim of priority is made, such as a 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.

In addition to patent and trademark protection, 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.”

Sales and Marketing

We hold worldwide commercialization rights, including through exclusive licenses, to our product candidates. Given our stage of development, we have established a small commercial organization and have not established distribution capabilities. Should any of our product candidates be approved for commercialization, we intend to develop a plan to commercialize them in the United States and other key markets, through internal infrastructure and/or external partnerships in a manner that will enable us to realize the full commercial value of our programs.

Manufacturing

Our success as a company will depend on our ability to deliver reliable, high-quality drug supply. 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 our product candidates. Because we rely on contract manufacturers, we employ personnel with extensive technical, manufacturing, analytical and quality experience. Our staff has strong project management discipline to oversee contract manufacturing and testing activities, and to compile manufacturing and quality information for our regulatory submissions.

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

Our current supply chains for our lead drug candidates involve several manufacturers that specialize in specific operations of the manufacturing process, specifically, raw materials procuring, drug substance manufacturing and drug product manufacturing. We currently operate under work order programs for our drug candidates with Master Services and Quality agreements in place that include specific supply timelines, volume and quality specifications. We are in discussions with our current manufacturers regarding preparation of Biologics License Applications (BLA) and Marketing Authorization Application (MAA) in the near future. This involves technology transfers, process characterization, and process validation to establish commercial manufacturing capabilities.

We intend to establish long-term supply agreements in the future. We believe our current manufacturers have the scale, the system, and the experience to supply our currently planned clinical trials and commercial launch. To ensure continuity in our supply chain, we plan to establish supply arrangements with alternative larger scale suppliers for certain portions of our supply chain, as appropriate.

Competition

The pharmaceutical, biopharmaceutical and biotechnology industries are characterized by rapidly advancing technologies, intense competition and a strong emphasis on proprietary products. While we believe that our technology, the expertise of our executive and scientific team, research, clinical capabilities, development experience and scientific knowledge provide us with competitive advantages, we face potential competition from many different sources, including pharmaceutical, biopharmaceutical and biotechnology companies, academic institutions, governmental agencies and public and private research institutions. Product candidates that we successfully develop and commercialize may compete with existing therapies and new therapies that may become available in the future.

Our competitors may have significantly greater financial resources, established presence in the market, expertise in research and development, manufacturing, preclinical and clinical testing, and experience in obtaining regulatory approvals and reimbursement and marketing approved products than we do. These competitors also compete with us in recruiting and retaining qualified scientific, sales, marketing and management personnel, establishing clinical trial sites and patient registration for clinical trials, as well as in acquiring technologies complementary to, or necessary for, our programs. Smaller or early-stage companies may also prove to be significant competitors, particularly through collaborative arrangements with large and established companies.

Guillain-Barré Syndrome

There are currently no approved therapies for GBS in the United States. IVIg and PE are the most commonly used therapies in the Western world and parts of Asia. Currently, two investigational products are in development. Hansa Biopharma AB is conducting an open label Phase 2 trial of imlifidase in GBS patients in Europe and the United Kingdom for which it released topline results in December 2023 and real-world comparison data in December 2024. AstraZeneca/Alexion completed a Phase 3 trial of SOLIRIS (eculizumab) in Japan that did not meet its primary endpoint. Additionally, a primary investigator sponsored Phase 2 trial with argenx’s efgartigimod is listed as an active trial.

Geographic Atrophy

Two treatments are currently FDA-approved for GA, both receiving approval in 2023: Apellis’s Syfovre, a C3 inhibitor as well as Astellas’s avacincaptad pegol, a C5 inhibitor. There are currently no approved therapies for GA in the EU. There is currently one combination complement cascade-targeted therapy in Phase 3 development for GA: Regeneron’s pozelimab, a C5 inhibiting monoclonal antibody combined with cemdisiran, a C5-targeted siRNA molecule. In Phase 2, there are currently four complement-targeting agents: Aviceda Therapeutics’s AVD-104, a nanoparticle molecule that inhibits complement cascade amplification and inflammation pathways, AstraZeneca’s danicopan, an oral, complement factor D inhibitor, Janssen’s JNJ 1887, a gene therapy candidate which expresses soluble CD59, a complement protein, and Novartis’s iptacopan, an oral factor B inhibitor. Other products that do not target the complement cascade currently in Phase 2 or 3 clinical trials are being developed by Roche, Alkeus, Belite Bio, Stealth BioTherapeutics, Boehringer Ingelheim, Galimedix Therapeutics, Cognition Therapeutics and ONL Therapeutics. Perceive Bio, Ocugen, and Astellas each have an asset in Phase 1 of development.

Cold Agglutinin Disease, a type of autoimmune hemolytic anemia

Sanofi’s Enjaymo was approved by the FDA for CAD in February 2022, and in October 2024, Sanofi sold global rights to Enjaymo to Italy-based Recordati. There are currently two investigational agents in clinical trials for CAD: Alpine Immune Sciences, Inc. is developing povetacicept, a fusion protein that blocks the function of two cytokines and Sanofi completed a phase I trial of BIVV020 in November 2023 with positive results with a single dose delivery in CAD patients.

Multifocal Motor Neuropathy

Currently, Gammagard Liquid (10% Immune Globulin Infusion (Human)) is the only therapy approved by the FDA for MMN. There are currently two agents in Phase 3 of development: Argenx’s empasiprubart (ARGX-117), an IV-delivered C2 inhibitor and Takeda’s TAK-771, which is being studied in a Japan-based Phase 3 trial. TAK-771 is a 10% Immune Globulin and Recombinant Human Hyaluronidase (rHuPH20) delivered as a subcutaneous infusion. There is also a complement-targeted agent, in Phase 2 development, Dianthus Therapeutics’ DNTH103, a monoclonal antibody inhibitor of C1s.

Lupus Nephritis

There are currently two approved medicines specifically for LN: GSK’s Benlysta and Aurinia’s Lupkynis. One agent, Roche’s obinutuzumab (Gazyva), has been filed with the FDA and EMA with approvals expected in 2025. There are four agents in development targeting the complement pathway, three in Phase 2 development and one in Phase 1 development: AstraZeneca’s ravulizumab, a C5 inhibitor, vemircopan (ALXN2050), an oral Factor D inhibitor, and Novartis’s iptacopan, an oral factor B inhibitor, are in Phase 2. AstraZeneca has a 3rd generation, subcutaneously administered C5 inhibitor, gefurulimab, which is being studied in a Phase 1, specifically for proteinuria. Outside of the complement pathway, there are currently four agents in Phase 3 development for adults with lupus: Novartis’s ianalumab, AstraZeneca’s anifrolumab, Vera Therapeutics’s atacicept and Aurinia’s voclosporin in adolescents with lupus nephritis. There are twelve cellular therapies in Phase 1 and Phase 1/2 of development as well as oral agents and monoclonal antibodies from BMS, Boehringer Engelheim, argenx, Janssen, Novartis and others in Phase 1 and Phase 2 development.

Huntington’s Disease

There are no approved disease-modifying therapies for HD, and no potentially disease modifying agents in Phase 3 development. Multiple companies are developing potentially disease-modifying therapies in earlier stages of development, including, PTC Therapeutics’s oral PTC518 in Phase 2, uniQure’s gene therapy candidate, AMT-130 in Phase 1/2, Roche’s tominersen in prodromal or early manifest HD patients aged 25-50 in Phase 2 and Vaccinex’s pepinemab in Phase 2. Additional early-stage products in development are Wave Life Sciences’s WVE-003 in Phase 1/2, Vico Therapeutics’s V0659 in Phase 1/2 and Alnylam’s ALN-HTT02 in Phase 1.

Amyotrophic Lateral Sclerosis

There are currently no additional complement-targeted therapies in clinical development. The drugs riluzole, Radicava and Radicava ORS (edaravone) are currently approved for the treatment of ALS and have shown modest effects in slowing the progression of the disease. Biogen’s Qalsody, an antisense oligonucleotide that binds to SOD1 mRNA, for those ALS patients with SOD1-ALS, received accelerated approval from the FDA in April 2023. Amylyx’s Relyvrio (AMX0035) was approved by the FDA in September 2022 for people living with ALS but was voluntarily pulled from the market by Amylyx after their Phase 3 confirmatory failed to show a benefit for ALS patients. Seven investigational agents are currently in Phase 3 development. There are a significant number of companies conducting earlier-stage clinical trials in ALS patients, including Ionis, argenx, Novartis, uniQure, NeuroSense, and others, testing oral agents, cellular therapies, gene therapies and other modalities.

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 product candidates such as those we are developing. A new drug must be approved by the FDA through the approval process and a new biologic must be approved by the FDA through the biologics license application, or BLA, process before it may be legally marketed in the United States. We, along with 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.

U.S. Biologics Regulation

In the United States, the FDA regulates drugs under the federal Food, Drug, and Cosmetic Act, or FDCA, and in the case of biologics, also under the Public Health Service Act, or PHSA, and their implementing regulations. The process required by the FDA before a drug or biologic may be marketed in the United States generally involves the following:

•

completion of preclinical laboratory tests and animal studies performed in accordance with the FDA’s Good Laboratory Practice requirements, or GLP requirements and other applicable regulations;

•

submission to the FDA of an Investigational New Drug application, or IND, which must become effective before clinical trials may begin;

•

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

•

performance of adequate and well-controlled human clinical trials in accordance with Good Clinical Practice, or GCP, requirements to establish the safety and efficacy of the proposed drug, or the safety, purity and potency of the proposed biologic for its intended purpose;

•

preparation of and submission to the FDA of an NDA or BLA after completion of all required clinical trials;

•

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

•

a determination by the FDA within 60 days of its receipt of an NDA or BLA whether to file the application for review;

•

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

•

FDA review and approval of the BLA or NDA to permit commercial marketing of the product for specific indication(s) for use in the United States.

Preclinical studies include laboratory evaluation of product chemistry, toxicity and formulation, as well as animal studies to assess potential safety and efficacy. Prior to beginning the first clinical trial with a product candidate in the United States, a sponsor must submit an IND to the FDA, which is a request for authorization from the FDA to administer an investigational new drug product to humans. The central focus of an IND submission is on the general investigational plan and the protocol(s) for the proposed clinical trial(s). The IND also includes results of animal and in vitro 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 goes into effect 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.

Clinical trials involve the administration of the investigational product to human subjects under the supervision of qualified investigators in accordance with GCP, which include the requirement that all research subjects provide their informed consent for their participation in any clinical trial. Clinical trials are conducted under protocols detailing, among other things, the objectives of the study, the parameters to be used in monitoring safety and the effectiveness criteria to be evaluated. 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. While the IND is active, progress reports summarizing the results of the clinical trials and nonclinical studies performed since the last progress report, among other information, must be submitted at least annually to the FDA, and written IND safety reports must be submitted to the FDA and investigators for serious and unexpected suspected adverse events, findings from other studies suggesting a significant risk to humans exposed to the same or similar drugs, findings from animal or in vitro testing suggesting a significant risk to humans, and any clinically important increased incidence of a serious suspected adverse reaction compared to that listed in the protocol or investigator brochure.

Furthermore, an independent IRB or EC 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 trial until completed. Some studies also include oversight by an independent group of qualified experts organized by the clinical trial sponsor, known as a Data Safety Monitoring Board, which provides authorization for whether or not a trial 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. Regulatory authorities, the IRB/ethics committee 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 objective(s). There are also requirements governing the reporting of ongoing clinical trials and clinical trial results to public registries.

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

•

Phase 1—The investigational product is initially introduced into healthy human subjects or patients with the target disease or condition. These trials are designed to test the safety, dosage tolerance, absorption, metabolism and distribution of the investigational product in humans, the side effects associated with increasing doses, and, if possible, to gain early evidence on effectiveness.

•

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

•

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

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 trials may also be made a condition to approval of the BLA or NDA.

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 cGMPs. 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.

FDA Review and Approval Process

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 or NDA requesting approval to market the product candidate for one or more indications. The BLA or NDA must include all relevant data available from preclinical studies and clinical trials, 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 trials intended to test the safety and effectiveness of a use of the product candidate or from a number of alternative sources, including studies and trials initiated by investigators. The submission of a BLA or NDA requires payment of a substantial user fee to the FDA, and the sponsor of an approved BLA or NDA is also subject to an annual program fee. A waiver of user fees may be obtained under certain limited circumstances. Additionally, no user fees are assessed on BLAs or NDAs for products designated as Orphan Drugs, unless the application also seeks a non-orphan-designated indication.

Within 60 days following submission of the application, the FDA reviews a BLA or NDA submitted to determine if it is substantially complete before the FDA accepts it for filing. The FDA may refuse to file any BLA or NDA that it deems incomplete or not properly reviewable at the time of submission and may request additional information. In this event, the Sponsor may meet with the FDA to confirm the additional information required to resubmit the BLA or NDA. Once a BLA or NDA has been accepted for filing, the FDA’s goal is to review standard applications within ten months after it accepts the application for filing, or, if the application qualifies for priority review, six months after it accepts the application for filing. Priority review designation will direct overall attention and resources to the evaluation of applications for products that, if approved, would represent significant improvements in the safety or effectiveness of the treatment, diagnosis or prevention of serious conditions. In both standard and priority reviews, the review process is often significantly extended by FDA requests for additional information or clarification. The FDA reviews an NDA to determine, among other things, whether a product is safe and effective for its intended use and whether its manufacturing is cGMP‐compliant to assure and preserve the product’s identity, strength, quality and purity. The FDA reviews a BLA to determine, among other things, whether a product is safe, pure and potent and the facilities in which it is manufactured, processed, packed or held meet standards designed to assure the product’s continued safety, purity and potency. The FDA may also convene a public Advisory Committee to provide additional expert insight on application review questions. The FDA is not bound by recommendations of an Advisory Committee, but it considers such recommendations when making decisions regarding approval.

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

After the FDA evaluates a BLA or NDA and conducts inspections of clinical trial sites and 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. An Approval Letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A Complete Response Letter indicates that the BLA or NDA is not ready for approval in its present form and ends the current review cycle, and will describe all of the deficiencies that the FDA has identified in the BLA or NDA. The FDA may issue the Complete Response Letter without first conducting required inspections, testing submitted product lots, and/or reviewing proposed labeling. In issuing the Complete Response Letter, the FDA may recommend actions that the applicant might take to place the BLA or NDA in condition for approval, including requests for additional information or clarification. The FDA may delay or refuse approval of a BLA or NDA 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. Additionally, the FDA may approve a BLA or NDA 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 to manage a known or potential serious risk associated with a medicine 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. 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 also require one or more Phase 4 post-marketing 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

A sponsor may seek approval of its product candidate under programs designed to accelerate FDA’s review and approval of product candidates that meet certain criteria. Specifically, drugs and biologics s are eligible for Fast Track designation if they 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. For a Fast Track product candidate, the FDA may consider sections of the BLA or NDA for review on a rolling basis before the complete application is submitted, if the sponsor provides a schedule for the submission of the sections of the application, the FDA agrees to accept sections of the application and determines that the schedule is acceptable and the sponsor pays any required user fees upon submission of the first section of the application. A BLA or NDA for a Fast Track-designated product candidate may also qualify for priority review, under which the FDA sets the target date for FDA action on the BLA or NDA at six months after the FDA accepts the application for filing. Priority review is granted when there is evidence that the product candidate, if approved, would provide a significant improvement in the safety or effectiveness of the treatment, diagnosis, or prevention of a serious disease or condition. If criteria are not met for priority review, the application is subject to the standard FDA review period of 10 months after FDA accepts the application for filing.

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 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 reviewers at FDA.

In addition, a product candidate may be eligible for accelerated approval. Drugs and biologics intended to treat serious or life threatening diseases or conditions may be eligible for accelerated approval upon a determination that the drug or biologic has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit or 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 approval, the FDA generally requires sponsors of products receiving accelerated approval to conduct well-controlled confirmatory required to verify or characterize the drug or biologic’s 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. The FDA may withdraw approval of a product or indication approved under accelerated approval if, for example, the sponsor fails to conduct any required confirmatory studies in a timely manner, or if such studies fail to verify the predicted clinical benefit of the product.

Fast Track designation, priority review, accelerated approval and Breakthrough Therapy designation do not change the standards for approval but may expedite the development or approval process. Even if a product 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 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 or NDA. 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. Orphan designation does not convey any advantage in or shorten the duration of the regulatory review and approval requirements or process.

If a product candidate that has Orphan Drug designation subsequently receives the first FDA approval for the disease or condition 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 or NDA, to market the same biologic or chemical entity for the same disease or condition 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 development activities and a waiver of the BLA or NDA application user fee.

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 the 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

Any drugs or biologics manufactured or distributed pursuant to FDA approvals 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 advertising and promotion of the product. 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. Drug and 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 cGMPs, which impose certain procedural and documentation requirements upon us and our third-party manufacturers. 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 cGMPs and impose reporting requirements upon us and any third-party manufacturers that we may decide to use. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMPs and other aspects of regulatory compliance.

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

•

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

•

fines, Warning Letters, or untitled enforcement letters;

•

clinical holds on clinical studies;

•

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

•

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

•

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

•

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

•

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

•

injunctions or the imposition of civil or criminal penalties.

The FDA closely regulates the marketing, labeling, advertising and promotion of drugs and biologics. A company can make only those claims relating to safety and efficacy, purity and potency that are approved by the FDA and in accordance with the provisions of the approved label. The FDA and other agencies actively enforce the laws and regulations prohibiting the promotion of so-called “off-label” uses. Failure to comply with these requirements can result in, among other things, adverse publicity, Warning Letters, corrective advertising and potential civil and criminal penalties. Physicians may prescribe legally available products for uses that are not described in the product’s labeling and that differ from those tested by us and approved by the FDA. Such off-label uses are common across medical specialties. Physicians may believe that such off-label uses are the best treatment for many patients in varied circumstances. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, restrict manufacturer’s communications on the subject of off-label use of their products.

Biosimilars and Exclusivity

The Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act, or collectively the ACA, signed into law in 2010, includes a subtitle called the 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. 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, 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.

Drug Product Marketing Exclusivity

Market exclusivity provisions authorized under the FDCA can delay the submission or the approval of certain marketing applications. For example, the FDCA provides a five-year period of non-patent data exclusivity within the United States to the first applicant to obtain approval of an NDA for a new chemical entity. A drug is a new chemical entity if the FDA has not previously approved any other new drug containing the same active moiety, which is the molecule or ion responsible for the action of the drug substance. During the exclusivity period, the FDA may not approve or even accept for review an abbreviated new drug application, or ANDA, or an NDA submitted under Section 505(b)(2), or 505(b)(2) NDA, submitted by another company for another drug based on the same active moiety, regardless of whether the drug is intended for the same indication as the original innovative drug or for another indication, where the applicant does not own or have a legal right of reference to all the data required for approval. However, an application may be submitted after four years if it contains a certification of patent invalidity or non-infringement to one of the patents listed with the FDA by the innovator NDA holder.

The FDCA alternatively provides three years of marketing exclusivity for an NDA, or supplement to an existing NDA if new clinical investigations, other than bioavailability studies, that were conducted or sponsored by the applicant are deemed by the FDA to be essential to the approval of the application, for example new indications, dosages or strengths of an existing drug. This three-year exclusivity covers only the modification for which the drug received approval on the basis of the new clinical investigations and does not prohibit the FDA from approving ANDAs or 505(b)(2) NDAs for drugs containing the active agent for the original indication or condition of use. Five-year and three-year exclusivity will not delay the submission or approval of a full NDA. However, an applicant submitting a full NDA would be required to conduct or obtain a right of reference to any preclinical studies and adequate and well-controlled clinical trials necessary to demonstrate safety and effectiveness.

Pediatric exclusivity is another type of marketing exclusivity available in the United States. Pediatric exclusivity provides for an additional six months of marketing exclusivity attached to another period of exclusivity if a sponsor conducts clinical trials in children in response to a written request from the FDA. The issuance of a written request does not require the sponsor to undertake the described clinical trials. In addition, orphan drug exclusivity, as described above, may offer a seven-year period of marketing exclusivity, except in certain circumstances.

Other Healthcare Laws and Compliance Requirements

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. Such laws include, without limitation, U.S. federal and state fraud and abuse laws, including false claims, civil monetary penalties, consumer protection and transparency laws regarding drug pricing and payments or other transfers of value made to physicians and other licensed healthcare professionals, as well as similar foreign laws in the jurisdictions outside the United States. Violation of any of such laws or any other governmental regulations that apply may result in penalties, including, without limitation, significant administrative, civil and criminal penalties, damages, fines, disgorgement, additional reporting obligations, contractual damages, the curtailment or restructuring of operations, exclusion from participation in governmental healthcare programs and imprisonment.

Data Privacy and Security Laws

Numerous state, federal and foreign laws, regulations, and standards govern the collection, use, access to, confidentiality and security of health-related and other personal data, including clinical trial data, and apply now or could apply in the future to our operations or the operations of our partners. In the United States, numerous federal and state laws and regulations, including data breach notification laws, health information privacy and security laws and consumer protection laws and regulations govern the collection, use, disclosure, and protection of health-related and other personal data. In addition, certain foreign laws govern the privacy and security of personal data, including health-related data. For example, the European Union General Data Protection Regulation, or the EU GDPR, imposes strict requirements for processing the personal data of individuals within the European Economic Area, or the EEA. Companies that must comply with the EU GDPR face increased compliance obligations and risk, including more robust regulatory enforcement of data protection requirements and potential fines for noncompliance of up to €20 million or 4% of the annual global revenues of the noncompliant company, whichever is greater. Further, from January 1, 2021, certain companies that have had to comply with the EU GDPR also have to comply with the UK GDPR, which, together with the amended UK Data Protection Act 2018, retains the GDPR in UK national law. The UK GDPR mirrors the fines under the GDPR, i.e., fines up to the greater of €20 million (£17.5 million) or 4% of global turnover. Privacy and security laws, regulations, and other obligations globally are evolving, may conflict with each other (which complicate compliance efforts and increases compliance cost), and can result in investigations, proceedings, and other actions that can lead to significant civil and/or criminal penalties and fines.

Coverage and Reimbursement

Sales of any pharmaceutical 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, commercial insurance and managed healthcare organizations, and the level of reimbursement for such product by third-party payors. No uniform policy exists for coverage and reimbursement for products exists among U.S. third-party payors. Therefore, decisions regarding the extent of coverage and amount of reimbursement to be provided are made on a plan-by-plan basis. The process for determining whether a third-party payor will provide coverage for a product typically is separate from the process for setting the price of such product or for establishing the reimbursement rate that the payor will pay for the product once coverage is approved. Third-party payors may limit coverage to specific products on an approved list, also known as a formulary, which might not include all of the FDA-approved products for a particular indication, or place products at certain formulary levels that result in lower reimbursement levels and higher cost-sharing obligation imposed on patients. One third-party payor’s decision to cover a particular medical product or service does not ensure that other payors will also provide coverage for the medical product or service. As a result, the coverage determination process will often require us to provide scientific and clinical support for the use of our product candidates to each payor separately and can be a time-consuming process, with no assurance that coverage and adequate reimbursement will be applied consistently or obtained in the first instance. 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. Additionally, separate reimbursement for the product itself or the treatment or procedure in which the product is used may not be available, which may impact physician utilization.

In international markets, reimbursement and healthcare payment systems vary significantly by country, and many countries have instituted price ceilings on specific products and therapies. For example, the European Union provides options for its member states to restrict the range of medicinal products for which their national health insurance systems provide reimbursement and to control the prices of medicinal products for human use. A member state may approve a specific price for the medicinal product or it may instead adopt a system of direct or indirect controls on the profitability of the company placing the medicinal product on the market. Pharmaceutical products may face competition from lower-priced products in foreign countries that have placed price controls on pharmaceutical products. Furthermore, there can be no assurance that a product will be considered medically reasonable and necessary for a specific indication, that a product will be considered cost-effective by third-party payors, that an adequate level of reimbursement will be established even if coverage is available or that the third-party payor’s reimbursement policies will not adversely affect the ability to sell a product profitably.

Healthcare Reform

In the United States and certain foreign jurisdictions, there have been, and we expect there will continue to be, a number of legislative and regulatory changes to the healthcare system. In March 2010, the ACA was signed into law, which substantially changed the way healthcare is financed by both governmental and private insurers in the United States and significantly affected the pharmaceutical industry. The ACA contains a number of provisions, including those governing enrollment in federal healthcare programs, reimbursement adjustments and fraud and abuse changes. Additionally, the ACA increased the minimum level of Medicaid rebates payable by manufacturers of brand name drugs from 15.1% to 23.1%; required collection of rebates for drugs paid by Medicaid managed care organizations; required manufacturers to participate in a coverage gap discount program, under which they must agree to offer 70.0% point-of-sale discounts off negotiated prices of applicable brand drugs to eligible beneficiaries during their coverage gap period, as a condition for the manufacturer’s outpatient drugs to be covered under Medicare Part D; imposed a non-deductible annual fee on pharmaceutical manufacturers or importers who sell certain “branded prescription drugs” to specified federal government programs; implemented a new methodology by which rebates owed by manufacturers under the Medicaid Drug Rebate Program are calculated for drugs that are inhaled, infused, instilled, implanted or injected; expanded eligibility criteria for Medicaid programs; created a new Patient-Centered Outcomes Research Institute to oversee, identify priorities in, and conduct comparative clinical effectiveness research, along with funding for such research; and established a Center for Medicare and Medicaid Innovation at CMS to test innovative payment and service delivery models to lower Medicare and Medicaid spending, potentially including prescription drug spending.

Since its enactment, there have been amendments to and judicial, Congressional and executive branch challenges to certain aspects of the ACA. For example, on August 16, 2022, the Inflation Reduction Act of 2022, or IRA, was signed into law, which among other things, extends enhanced subsidies for individuals purchasing health insurance coverage in ACA marketplaces through plan year 2025. The IRA also eliminates the "donut hole" under the Medicare Part D program beginning in 2025 by significantly lowering the beneficiary maximum out-of-pocket cost and creating a new manufacturer discount program.

Other legislative changes have been proposed and adopted since the Affordable Care Act was enacted, including aggregate reductions of Medicare payments to providers, which will remain in effect through 2032, absent additional Congressional action. In addition, on March 11, 2021, the American Rescue Plan Act of 2021 was signed into law, which eliminates the statutory Medicaid drug rebate cap, currently set at 100.0% of a drug’s average manufacturer price, effective 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 and proposed and enacted legislation designed, among other things, to bring more transparency to product pricing, review the relationship between pricing and manufacturer patient programs and reform government program reimbursement methodologies for pharmaceutical products. Most recently, the IRA, among other things, (1) directs the U.S. Department of Health and Human Services, or HHS, to negotiate the price of certain single-source drugs and biologics that have been on the market for at least 7 years covered under Medicare, or Medicare Drug Price Negotiation Program, and (2) imposes rebates under Medicare Part B and Medicare Part D to penalize price increases that outpace inflation. These provisions began to take effect beginning fiscal year 2023. On August 15, 2024, HHS announced the agreed-upon price of the first ten drugs that were subject to price negotiations, although the Medicare Drug Price Negotiation Program is currently subject to legal challenges. On January 17, 2025, HHS selected fifteen additional products covered under Part D for price negotiation in 2025. Each year thereafter more Part B and Part D products will become subject to the Medicare Drug Price Negotiation Program. The IRA permits the Secretary of the Department of HHS to implement many of these provisions through guidance, as opposed to regulation, for the initial years. For that and other reasons, it is currently unclear how the IRA will be effectuated. 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, mechanisms to encourage importation from other countries and bulk purchasing. Furthermore, there has been increased interest by third-party payors and governmental authorities in reference pricing systems and publication of discounts and list prices.

We expect that additional state and federal healthcare reform measures will be adopted in the future, any of which could limit the amounts that federal and state governments will pay for healthcare product candidates and services, which could result in reduced demand for our product candidates once approved or additional pricing pressures.

Human Capital Resources

As of December 31, 2024, we had 100 full-time employees, 80 of whom were primarily engaged in research and development activities. A total of 38 employees have an M.D., Ph.D. or Pharm.D. degree. Most of our employees are based in our Brisbane, California facility, subject to hybrid and remote work arrangements.

We believe that our future success will depend, in part, on our ability to continue to attract, hire, and retain qualified personnel. We continue to seek additions to our science and technical staff. Through our experience with technological innovation, we appreciate the importance of retention, growth and development of our employees. We believe we offer competitive compensation (including salary, incentive bonus, and equity) and benefits packages. None of our employees is represented by a labor union, and we consider our employee relations to be good.

Corporate Information

We were incorporated under the laws of the State of Delaware on March 3, 2011. Our principal executive offices are located at 1400 Sierra Point Parkway, Bldg C, Suite 200, Brisbane, California 94005, and our telephone number is (650) 822-5500. Our corporate website address is www.annexonbio.com. Information contained on, or accessible through, our website shall not be deemed incorporated into and is not a part of this Annual Report on Form 10-K.

Available Information

We file Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K, proxy statements, and related amendments, exhibits and other information with the Securities and Exchange Commission, or the SEC. You may access and read our filings without charge through the SEC’s website at www.sec.gov or through our website at https://ir.annexonbio.com/financial-information/sec-filings, as soon as reasonably practicable after such materials are electronically filed with or furnished to the SEC pursuant to Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended, or the Exchange Act. Information contained on, or accessible through, our website shall not be deemed incorporated into and is not a part of this Annual Report on Form 10-K.

Item 1A. Risk Factors.

Our business involves significant risks, some of which are described below. You should carefully consider the risks and uncertainties described below, together with all of the other information contained in this Annual Report on Form 10-K, including "Management's Discussion and Analysis of Financial Condition and Results of Operations" and the financial statements and the related notes. If any of the following risks actually occur, it could harm our business, prospects, results of operations and financial condition and future prospects. In such event, the market price of our common stock could decline and you could lose all or part of your investment. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also impair our business operations. This Annual Report on Form 10-K also contains forward-looking statements that involve risks and uncertainties. Our actual results could differ materially from those anticipated in the forward-looking statements as a result of factors that are described below and elsewhere in this Annual Report on Form 10-K.

Risks Related to Our Limited Operating History, Financial Condition and Capital Requirements

We are a clinical-stage biopharmaceutical company, and we have only a limited operating history upon which you can evaluate our business and prospects. Biopharmaceutical product development is a highly speculative undertaking and involves a substantial degree of risk. We have no products approved for commercial sale and have not generated any revenue from sales of our product candidates and have incurred losses in each year since our inception in March 2011. We have only a limited operating history upon which you can evaluate our business and prospects. In addition, we have not yet demonstrated an ability to successfully overcome many of the risks and uncertainties frequently encountered by companies in new and rapidly evolving fields, particularly in the pharmaceutical, biopharmaceutical and biotechnology industry.

We have had significant operating losses since our inception. Our net loss for the years ended December 31, 2024 and 2023 was approximately $138.2 million and $134.2 million, respectively. As of December 31, 2024, we had an accumulated deficit of $710.7 million. Substantially all of our losses have resulted from expenses incurred in connection with our research and development programs and from general and administrative costs associated with our operations. We expect to continue to incur losses for the foreseeable future, and we anticipate these losses will continue as we develop our product candidates, conduct clinical trials and pursue research and development activities. Even if we achieve profitability in the future, we may not be able to sustain profitability in subsequent periods. Our prior losses, combined with expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital.

Since our inception, we have invested a significant portion of our efforts and financial resources in research and development activities. Our product candidates will require additional clinical development, and we intend to conduct additional research and development activities to discover and develop new product candidates, including conducting preclinical studies and clinical trials, all of which will require substantial additional funds. We will continue to expend significant resources for the foreseeable future in connection with these activities. These expenditures will include costs associated with conducting preclinical studies and clinical trials, obtaining regulatory approvals and manufacturing and supply, as well as marketing and selling any products approved for sale. In addition, other unanticipated costs may arise. Because the outcome of any preclinical study or clinical trial is highly uncertain, we cannot reasonably estimate the actual amounts necessary to successfully complete the development and commercialization of our product candidates or any future product candidates.

As of December 31, 2024, we had capital resources consisting of cash and cash equivalents and short-term investments of approximately $312.0 million. We expect our existing capital resources to fund our planned operating expenses into the second half of 2026. However, our operating plans may change as a result of many factors currently

unknown to us, and we may need to seek additional funds sooner than planned through public or private equity offerings or debt financings or other sources, such as strategic collaborations. Such financing may result in dilution to our stockholders, imposition of burdensome debt covenants and repayment obligations, or other restrictions that may affect our business. In addition, we may seek additional capital due to favorable market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans.

Our future capital requirements depend on many factors, including:

•

the scope, progress, results and costs of researching and developing our current product candidates or any other future product candidates we choose to pursue, conducting preclinical studies and clinical trials;

•

the timing of, and the costs involved in, obtaining feedback from regulators on our clinical trials and regulatory approvals for our product candidates or any future product candidates;

•

the number and characteristics of any additional product candidates we develop or acquire;

•

the timing and amount of any milestone, royalty and/or other payments we are required to make pursuant to our current or any future license or collaboration agreements;

•

the cost of manufacturing our product candidates or any future product candidates and any products we successfully commercialize;

•

the cost of building a sales force in anticipation of product commercialization;

•

the cost of commercialization activities of our product candidates, if approved for sale, including marketing, sales and distribution costs;

•

ANNX US Equity

ANNX · 10-K · period ended 2024-12-31

Item 1. Business.

Item 1A. Risk Factors.

ANNX US Equity☆

ANNX · 10-K · period ended 2024-12-31

Item 1. Business.

Item 1A. Risk Factors.

ANNX US Equity