10-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

FORM 10-K

(Mark One)

☒ ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2025

☐ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the transition period from to

Commission File Number: 001-37465

Seres Therapeutics, Inc.

(Exact Name of Registrant as Specified in Its Charter)

101 Cambridgepark DriveCambridge, Massachusetts 02140

(Address of Principal Executive Offices) (Zip Code)

(617) 945-9626

(Registrant’s Telephone Number, Including Area Code)

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

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

Common stock, par value $0.001 per share MCRB The Nasdaq Global Select Market

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

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ No ☒

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

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

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of the "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 Act). Yes ☐ No ☒

The aggregate market value of the voting and non-voting common stock held by non-affiliates of the registrant based on the closing price of the registrant’s common stock as reported on the Nasdaq Global Select Market on June 30, 2025, was $71,941,772. Solely for purposes of this disclosure, shares of common stock held by executive officers, directors and certain stockholders of the registrant as of such date have been excluded because such holders may be deemed to be affiliates.

As of March 6, 2026 there were 9,586,298 shares of the registrant’s common stock, par value $0.001 per share, outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive Proxy Statement relating to its 2026 Annual Meeting of Stockholders to be filed with the SEC within 120 days after the end of the fiscal year ended December 31, 2025 are incorporated herein by reference in Part III.

TABLE OF CONTENTS

Page

PART I.

Item 1. Business 5

Item 1A. Risk Factors 33

Item 1B. Unresolved Staff Comments 73

Item 1C. Cybersecurity 73

Item 2. Properties 74

Item 3. Legal Proceedings 74

Item 4. Mine Safety Disclosures 74

PART II.

Item 6. [Reserved] 75

Item 7A. Quantitative and Qualitative Disclosures about Market Risk 93

Item 8. Financial Statements and Supplementary Data 93

Item 9A. Controls and Procedures 93

Item 9B. Other Information 93

Item 9C. Disclosure Regarding Foreign Jurisdictions that Prevent Inspections 94

PART III.

Item 10. Directors, Executive Officers and Corporate Governance 95

Item 11. Executive Compensation 99

Item 14. Principal Accountant Fees and Services 99

PART IV.

Item 15. Exhibits and Financial Statement Schedules 100

FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K contains forward-looking statements. We intend such forward-looking statements to be covered by the safe harbor provisions for forward-looking statements contained in Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. All statements other than statements of historical facts contained in this Annual Report on Form 10-K, including without limitation statements regarding our future results of operations and financial position including our projected cash runway, our requirement for additional funding, our business strategy, including potential strategic partnership efforts, our prospective products, the design, timing and results of our clinical studies and data readouts, product approvals, communications with, feedback from, or submissions to the FDA, research and development costs, the timing and likelihood of success, our ability to continue as a going concern, our ability to maintain compliance with any applicable Nasdaq listing requirements, executive and director transition matters, plans and objectives of management for future operations and future results of anticipated products, or the timing of any of the foregoing, are forward-looking statements. These statements involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

In some cases, you can identify forward-looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions. The forward-looking statements in this Annual Report on Form 10-K are only predictions. We have based these forward-looking statements largely on our current expectations and projections about future events and financial trends that we believe may affect our business, financial condition and results of operations. These forward-looking statements speak only as of the date of this report and are subject to a number of important factors that could cause actual results to differ materially from those in the forward-looking statements, including the risks, uncertainties and assumptions described under the sections in this report titled “Summary Risk Factors,” “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in this Annual Report on Form 10-K.

Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties.

You should read this Annual Report on Form 10-K and the documents that we reference in this Annual Report on Form 10-K completely and with the understanding that our actual future results may be materially different from what we expect. We qualify all of our forward-looking statements by these cautionary statements. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances or otherwise.

TRADEMARKS, SERVICE MARKS AND TRADENAMES

We have proprietary rights to trademarks used in this Annual Report on Form 10-K, which are important to our business and many of which are registered under applicable intellectual property laws. Solely for convenience, the trademarks, service marks, logos and trade names referred to in this Annual Report on Form 10-K are without the ® and TM symbols, but such references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights to these trademarks, service marks and trade names. This Annual Report on Form 10-K contains additional trademarks, service marks and trade names of others, which are the property of their respective owners. All trademarks, service marks and trade names appearing in this Annual Report on Form 10-K are, to our knowledge, the property of their respective owners. We do not intend our use or display of other companies’ trademarks, service marks, copyrights or trade names to imply a relationship with, or endorsement or sponsorship of us by, any other companies.

SUMMARY RISK FACTORS

Our business is subject to numerous risks and uncertainties, including those described in Part I, Item 1A. “Risk Factors” in this Annual Report on Form 10-K. You should carefully consider these risks and uncertainties when investing in our common stock. The principal risks and uncertainties affecting our business include the following:

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We have identified conditions and events that raise substantial doubt regarding our ability to continue as a going concern.

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We will need additional funding in order to advance development of our product candidates (including to conduct the Phase 2 study of SER-155 in allo-HSCT) and commercialize our product candidates, if approved. If we are unable to raise capital or secure a partnership or other business development transaction, we could be required to implement further cost-reduction measures, reduce or delay our product development programs or any potential future commercialization efforts, or pursue other alternatives, which could include seeking relief under the U.S Bankruptcy Code or winding down our operations.

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We are a clinical-stage company and have incurred significant losses since our inception. We expect to incur losses for the foreseeable future and may never achieve or maintain profitability.

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The total amount of the Milestone Payments (as defined herein) we may receive from the Transaction is subject to various risks and uncertainties.

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We may not be able to realize the anticipated benefits of the Transaction (as defined herein), and we may face new challenges as a smaller, less diversified company.

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Our limited operating history may make it difficult to evaluate the success of our business to date and to assess our future viability.

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We are early in our development efforts of certain of our product candidates and may not be successful in our efforts to use our reverse translational platform to build a pipeline of product candidates and develop additional marketable drugs.

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Our product candidates are based on live biotherapeutics, which is a novel approach to therapeutic intervention.

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Clinical drug development involves a risky, lengthy and expensive process, with an uncertain outcome. We may incur additional costs or experience delays in completing, or ultimately be unable to complete, the development and any potential future commercialization of our product candidates.

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Delays or difficulties in the enrollment of patients in clinical trials, could result in our receipt of necessary regulatory approvals being delayed or prevented.

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Disruptions at the FDA and other government agencies caused by funding shortages, government shutdowns, or staffing limitations could hinder their ability to hire, retain or deploy key leadership and other personnel, or otherwise prevent new or modified products from being developed, approved or commercialized in a timely manner or at all, which could negatively impact our business.

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Current and future legislation or regulation may increase the difficulty and cost for us to obtain marketing approval of and commercialize our product candidates and may adversely affect the prices we may obtain.

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If we are not able to obtain, or if there are delays in obtaining, required regulatory approvals, we or any collaborators will not be able to commercialize our product candidates or will not be able to do so as soon as anticipated, and our ability to generate revenue will be materially impaired. Additionally, failure to obtain marketing approval in international jurisdictions would prevent our product candidates from being marketed abroad.

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We rely, and expect to continue to rely, on third parties to conduct our clinical trials, and those third parties may not perform satisfactorily, including failing to meet deadlines for the completion of such trials.

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Even if any of our product candidates receive marketing approval, such product candidates may fail to achieve the degree of market acceptance by physicians, patients, hospitals, third-party payors and others in the medical community necessary for commercial success.

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We face substantial competition, which may result in others discovering, developing or commercializing competing products before or more successfully than we do.

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If we are unable to adequately protect our proprietary technology or obtain and maintain issued patents that are sufficient to protect our product candidates, others could compete against us more directly, which would have a material adverse impact on our business, results of operations, financial condition and prospects.

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Our future success depends on our ability to retain key executives and to attract, retain and motivate qualified personnel.

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We have in the past and may again in the future receive a notice of the failure to satisfy a continued listing rule from Nasdaq.

PART I

Item 1. Business

Overview

We are a clinical-stage company focused on improving patient outcomes in medically vulnerable populations through discovery and development of novel live biotherapeutic product, or LBP, candidates. We led the successful development and approval of VOWST, the first FDA-approved orally administered microbiome biotherapeutic and a Breakthrough Therapy designated drug, which was sold to Société des Produits Nestlé S.A., or SPN, and with certain of its affiliates, collectively, Nestlé Health Science, in September 2024. We have established field-leading capabilities and platforms that are powered by best-in-field human data sets to advance a portfolio of products that can uniquely address diseases by targeting host pathways that are modulated by microbes in the human body, and, in particular, diseases associated with mucosal barrier-immune interface targets. We believe clinical and nonclinical data across our programs support the development of LBPs to target the prevention and treatment of a broad swath of infections, and to treat inflammatory and immune, or I&I, diseases. Our pipeline consists of SER-155, SER-603, and SER-147, as well as other potential candidates in earlier development.

Our LBP candidates are consortia of bacteria designed to optimize specific, targeted pharmacological properties, and are formulated for oral delivery. We maintain a differentiated live biotherapeutics drug discovery and development platform that includes good manufacturing practices, or GMP, manufacturing capabilities for this novel drug modality. Our pipeline assets, including SER-155 and SER-603, are designed to target multiple disease-relevant pathways and are manufactured from standard clonal cell banks via cultivation. Our knowledge base and platforms enable selection of bacteria for precision consortia design to drive specific clinical outcomes and further provide unique insights on microbe-associated disease targets. We are designing LBP candidates to modulate host function to increase epithelium integrity and to induce immune homeostasis and tolerance, as well as to prevent the colonization and overgrowth of pathogens in the gastrointestinal, or GI, tract. We believe that the scientific and clinical data from the development of VOWST (our then product candidate SER-109 program) and the data from the SER-155 Phase 1b study (described below) validate our novel therapeutic approach in both infectious disease and I&I diseases. In the context of infection, we believe that our technology may be replicable across different bacterial pathogens with the potential to develop live biotherapeutics to protect a range of medically compromised patients at risk of antimicrobial resistance, or AMR, infections and bloodstream infections, or BSIs, that can result from a compromised epithelial barrier and that can be a major cause of mortality.

SER-155, our most advanced LBP candidate, is an investigational, oral, live biotherapeutic designed to decolonize GI pathogens, improve GI epithelial barrier integrity, and induce immune homeostasis to prevent bacterial BSIs, including those that can harbor antimicrobial resistance, as well as other pathogen-associated negative clinical outcomes in patients undergoing allogeneic hematopoietic stem cell transplantation, or allo-HSCT. In December 2023, we received Fast Track Designation for SER-155 to reduce the risk of infection and GvHD in patients undergoing allo-HSCT, and in December 2024, the FDA granted Breakthrough Therapy designation to SER-155 for the reduction of BSIs in patients 18 years and older undergoing allo-HSCT. In our placebo-controlled Phase 1b study of SER-155 in allo-HSCT, SER-155 was associated with a 77% relative risk reduction in bacterial BSIs and a significant reduction in systemic antibiotic exposure as well as a lower incidence of febrile neutropenia, as compared to placebo through day 100 post HSCT. SER-155 was generally well tolerated, with no observed treatment-related serious adverse events. Importantly, we observed clinical translation on the drug candidate's mechanisms of action, including improvements in epithelial integrity and immune homeostasis. Following advancement of key startup activities for the SER-155 Phase 2 study in allo-HSCT, including the submission of a final protocol to the FDA in January 2026, study site evaluation and qualification with our CRO, and manufacturing of drug substance, we have paused additional investment in that program, preserving the optionality to efficiently restart the study, while continuing to seek funding for the Phase 2 study.

Our current strategy prioritizes advancing our programs that target I&I indications. We have meaningfully advanced over the past decade our scientific understanding of how microbes in the GI functionally modulate pathways at the mucosal barrier-immune interface that are associated with inflammatory and immune-related disease. The clinical data from our SER-155 Phase 1b study in allo-HSCT, along with our extensive preclinical and translational clinical data compiled over the past decade support and inform the advancement of our earlier stage programs targeting I&I diseases. We are evaluating SER-155 in immune checkpoint-related enterocolitis, or irEC, and we are developing SER-603, broadly in inflammatory bowel disease, or IBD, including ulcerative colitis, or UC, and Crohn's disease. We believe that our LBPs could represent a non-immunosuppressive treatment option for I&I diseases that are linked to colitis and could broadly address immune therapy toxicities, both of which represent significant unmet medical needs and potential commercial opportunities. We are currently exploring potential collaborations related to those I&I disease programs.

We have been collaborating with Memorial Sloan Kettering Cancer Center for over a decade on the impact of the GI microbiome on immune related diseases and cancer; recently this long-standing collaboration included an investigator-sponsored trial, or IST, evaluating SER-155 in 15 participants with irEC. irEC is among the most frequent and severe immune-related adverse events, or irAEs, in recipients of immune checkpoint inhibitor, or ICI, therapy and can be observed in up to 50% of patients, with rates varying based on cancer drug and treatment regimen. ICIs can cause a wide range of irAEs with links to T cell biology and epithelial barrier inflammation, both of which are biological functions shown in our preclinical and clinical pharmacology data to be positively impacted by SER-155. We expect to report initial clinical results, including preliminary safety, efficacy, pharmacology, and

exploratory biomarker data in the second quarter of 2026. We believe data from this IST could further support the potential for live biotherapeutics to address a significant unmet need among the large population of cancer patients receiving ICIs and may further support evaluation of our biotherapeutic approach in this setting.

SER-603 is a novel, LBP candidate optimized to address disruptions in the GI microbiome and to improve GI mucosal barrier integrity through the inhibition of inflammatory bacteria and associated metabolites, the promotion of epithelial barrier integrity to reduce the translocation of inflammatory molecules and barrier inflammation, and to induce immune homeostasis through non-immunosuppressive regulatory T cell, or T-reg, induction via T cell signaling. Our research on SER-603 has been primarily supported through a partnership with the Crohn’s and Colitis Foundation, or CCF. These efforts aim to (i) confirm the functional phenotype and inflammatory state of patient subpopulations observed in our prior ulcerative colitis, or UC, clinical trials, and (ii) prioritize inflammatory targets and evaluate the potential to utilize biomarker-based patient selection and stratification for future studies. Many IBD patients experience an efficacy ceiling due to non-response or poor durability of response to existing therapies, and further, most advanced therapies target downstream inflammatory and immune responses and are immunosuppressive leading to toxicities and limitations with respect to combination therapies. IBD is a heterogeneous disease with both disruptions in the GI microbiome and epithelial barrier compromise being important drivers of disease that are not addressed by existing IBD therapies.

We believe that SER-155 and other cultivated live biotherapeutic candidates could be developed in additional patient populations to address barrier compromise and bloodstream and AMR infections beyond allo-HSCT, including autologous-HSCT patients, cancer patients with neutropenia, chimeric antigen receptors therapy, or CAR-T, recipients, individuals with chronic liver disease, or CLD, solid organ transplant recipients, as well as patients in the intensive care unit, or ICU, and long-term acute care facilities. We continue to develop another proprietary live biotherapeutic composition, SER-147, designed to prevent bacterial bloodstream and spontaneous bacterial peritonitis, or SBP, infections in patients with metabolic disease, including CLD. Additionally, we are developing an oral liquid formulation based on SER-155 strains, for dosing in patients who cannot take oral capsules, such as intubated patients in the ICU, and other medically vulnerable patients at high risk of AMR infections, supported by a grant from CARB-X (Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator). We continue to leverage microbiome pharmacokinetic and pharmacodynamic data from across our clinical and preclinical portfolios, using our reverse translational development platform to prioritize future drug targets and to identify opportunities for monotherapy treatment and in combination with existing therapies across various indications, including inflammatory and immune diseases, cancer, and metabolic diseases.

We have built and deploy a reverse translational platform and knowledge base, which we call our MbTx Platform, for the discovery and development of live biotherapeutics, and maintain extensive proprietary know-how that may be used to support future research and development efforts. This platform incorporates high-resolution analysis of human clinical data to identify microbiome biomarkers associated with disease and non-disease states; preclinical screening using human cell-based assays and in vitro/ex vivo and in vivo disease models customized for live biotherapeutics; and a strain library and associated microbiological capabilities that spans broad biological and functional breadth. This platform and knowledge base are integrated through a proprietary knowledge graph and agentic artificial intelligence, enabling rapid identification of specific microbes, microbial genes, and microbial metabolites/peptides associated with disease and the design of therapeutic consortia of bacteria for specific pharmacological properties to restructure the gut microbiome and modulate functional pathways associated with disease. In addition, we own a valuable intellectual property estate related to the development and manufacture of live biotherapeutics.

We have assembled a world class group of scientists, clinicians, directors and investors, who have established our leadership in the field of live biotherapeutics. We were founded by Flagship Pioneering, and our experienced management team possesses core capabilities and know-how in live biotherapeutics, drug development, regulatory approval, chemistry, manufacturing and controls, or CMC, commercialization, public company management and finance.

Our Strategy

Our goal is to remain the leading biopharmaceutical company developing live biotherapeutics to address significant unmet medical needs. We intend to advance our field-leading capabilities and platforms for the discovery and development of live biotherapeutics and leverage our translational platforms that are powered by best-in-field human data sets to advance a portfolio of early-stage products that can address diseases by targeting host pathways that are modulated directly by microbes or microbe produced metabolites and peptides in the human body, in particular diseases associated with mucosal barrier-immune interface targets. Having finalized the protocol for the Phase 2 study of SER-155 in patients undergoing allo-HSCT with the FDA and having advanced key study startup activities for this program, we will pause further investment while efforts to seek funding for the study remain ongoing. The SER-155 program has meaningfully advanced our understanding of how microbes in the GI tract functionally modulate pathways at the mucosal barrier-immune interface associated with inflammatory and immune-related diseases. Accordingly, our strategy moving forward will prioritize advancing our early-stage programs, including SER-603 that targets inflammatory and immune indications such as UC and Crohn's disease, and SER-155 in irEC, including supporting the read-out of clinical results from the fully enrolled investigator-sponsored SER-155 study in irEC which are expected in the second quarter of 2026.

Advancing our Programs

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Leverage scientific and clinical data from past successful drug development programs and apply learnings to advance early-stage pipeline programs in inflammatory and immune diseases (I&I). We believe clinical and nonclinical data across our programs support the development of live biotherapeutics to target the prevention and treatment of a broad range of I&I diseases such as UC, Crohn's disease, and irEC. We believe that the scientific and clinical data from the development of VOWST (our then product candidate SER-109 program) and the data from the SER-155 Phase 1b study validate our novel therapeutic approach. The SER-155 program has meaningfully advanced our understanding of how microbes in the GI tract functionally modulate pathways at the mucosal barrier-immune interface associated with I&I diseases. Discussions are ongoing with counterparties related to potential collaborations in these areas.

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Advance development of SER-155 in allo-HSCT. We intend to continue the development of SER-155, an investigational, oral, live biotherapeutic designed to decolonize GI pathogens and improve GI epithelial barrier integrity to prevent bacterial BSIs, including those that can harbor AMR, as well as other pathogen-associated negative clinical outcomes in patients undergoing allo-HSCT. In December 2023, we received Fast Track Designation for SER-155 to reduce the risk of infection and graft versus host disease, or GvHD, in patients undergoing allo-HSCT. In September 2024, we announced topline clinical data from Cohort 2 of the SER-155 Phase 1b placebo-controlled study in patients undergoing allo-HSCT, in which SER-155 was associated with a significant reduction in BSIs (77% relative risk reduction), a significant reduction in systemic antibiotic exposure, and lower incidence of febrile neutropenia, in each case as compared to placebo, through day 100 post-HSCT. Additionally, SER-155 was generally well tolerated, with no observed treatment-related serious adverse events. In December 2024, the FDA granted Breakthrough Therapy designation to SER-155 for the reduction of BSIs in patients 18 years and older undergoing allo-HSCT. Seres has finalized the protocol for the Phase 2 study of SER-155 allo-HSCT patients with the FDA and has advanced key study startup activities. The planned Phase 2 study will incorporate a well-powered, placebo-controlled design, which provides for a planned interim analysis to enable an expedited initial data readout. Further investment in this program is paused while efforts to seek funding for the Phase 2 study remain ongoing.

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Maximize the broader opportunity of live biotherapeutics in other medically vulnerable patient populations in which there is a significant unmet need. We believe that SER-155 and SER-603 and other cultivated LBP candidates could be developed in additional patient populations to address mucosal barrier compromise and immune dysfunction associated disease as well as to address bloodstream and AMR infections beyond allo-HSCT, including autologous-HSCT patients, cancer patients with neutropenia, CAR-T, recipients, individuals with CLD, solid organ transplant recipients, as well as patients in the ICU and long-term acute care facilities. In July 2025, we were awarded a grant from CARB-X to support the development of an oral liquid formulation of SER-155 for medically vulnerable patient populations at risk of BSIs, including AMR infections, who cannot be dosed with oral capsules, such as intubated patients in the ICU. The CARB-X grant provides us with up to $3.6 million of funding for research, manufacture, and design of a Phase 1 clinical trial in ICU patients. We are also developing SER-147, an investigational live biotherapeutic designed to prevent bacterial bloodstream and SBP infections in patients with metabolic disease, including CLD. CLD is a progressive condition marked by deterioration of liver function and is reaching epidemic proportions affecting nearly 1.7 billion people worldwide, causing substantial health burden on afflicted countries. In the advanced stages of CLD, known as decompensated cirrhosis, patients exhibit significant immune dysfunction, microbiome disruption, and increased contact with the healthcare system, all of which drive increased susceptibility to bacterial infections.

Utilizing Our Capabilities

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Leverage our leading reverse translational platform to develop additional innovative and novel live biotherapeutics across a range of serious medical conditions with high unmet need including inflammatory disease, disease associated with modulation of host immunity, and infections. We believe that the combination of experience, proprietary data and proprietary know-how related to the microbiome, the functional properties of microbial species and strains, microbe-host interactions, the cultivation of microbial strains, and microbiome-specific functional screens and analytics provides us a competitive advantage in the design and development of live biotherapeutics. Our platform enables us to build upon our existing and growing clinical experience to rationally design treatments for acute and complex chronic diseases. We intend to leverage this advantage to develop additional innovative live biotherapeutics.

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Develop manufacturing capabilities sufficient to support commercialization of any approved live biotherapeutic candidates. Live biotherapeutic manufacturing requires capabilities that are distinct from other biologic drugs. We have made strategic investments in manufacturing capabilities to help ensure that we maintain control of our know-how and also because we believe these capabilities will be necessary and highly advantageous for the development of future live biotherapeutic candidates. Our bioprocess and manufacturing personnel are focused on creating a platform of manufacturing expertise that will set the stage for further advances in the emerging field of live biotherapeutics.

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Leverage our regulatory success in a novel drug modality. Live biotherapeutics are a novel drug modality. Regulatory requirements for novel modalities can be complex and must ensure the safety and efficacy of the specific drug and also the manufacturing process, consistency, quality, and other potential effects of the platform. We successfully developed and

manufactured VOWST which obtained FDA Breakthrough Therapy and Orphan Drug Designations and obtained priority review approval of VOWST, the first FDA-approved orally administered microbiome therapeutic. This approval required substantial engagement with the FDA to develop relevant standards for live biotherapeutics and then achieve them for VOWST. Through the development of SER-155, we continue to have ongoing and constructive engagement with FDA. In December 2023, we received Fast Track Designation for SER-155 to reduce the risk of infection and GvHD in patients undergoing allo-HSCT, and in December 2024, the FDA granted Breakthrough Therapy designation to SER-155 for the reduction of BSIs in patients 18 years and older undergoing allo-HSCT. Additionally, we successfully developed a protocol for the SER-155 Phase 2 study, incorporating FD feedback. We believe these experiences provide capability and experience for the discovery, clinical development, manufacturing, and regulatory engagement supporting all of our other programs.

Our Live Biotherapeutics Platform

We have developed a field leading reverse translational biotherapeutics platform and knowledge base which we believe enables us to apply our capabilities to efficiently identify, manufacture and develop novel live biotherapeutics for serious human diseases. This platform incorporates analysis of microbiome biomarkers from human clinical data and preclinical assessments using human cell-based assays and in vitro/ex vivo and in vivo functional screening and disease models. To identify specific microbiome and host signatures that associate with disease or the onset of disease, we utilize data sets from healthy subjects and subjects with disease, or being treated for a disease, to delineate at high-resolution the microbial composition and functional profiles of the microbiome associated with the physiological state of subjects. These in-human insights on how different microbial strains, species, genes, metabolites or peptides directly or indirectly modulate disease-relevant functional pathways in the host are leveraged in preclinical drug design, optimization and development.

Our discovery process begins with human data derived from clinical trials and cohort studies, which we use as a data input for target identification and the design of our live biotherapeutic candidates. We compare healthy, normal colonic microbiomes to those in an unhealthy disrupted or disease state, revealing the ecological, compositional and functional differences between various states of disease and during the transition from health to disease or vice versa. Specifically, we utilize clinical data sets combined with advanced data sciences and customized, proprietary microbiome analytics to identify microbiome signatures of disease at the resolution of specific species and strains, metabolites, or genes that are associated with disease states. These microbiome biomarkers are associated with host signatures and biomarkers of disease to identify drug targets for our live biotherapeutics. Our clinical data from VOWST (developed as SER-109), SER-287, SER-301, SER-155, and other programs, and microbiome data generated with external collaborators, serve to instruct us on how the introduction of certain keystone microbes have the potential to restructure the microbiome and modulate the metabolic state of the gut to shift it to a non-disease state.

We have developed a proprietary, functionally characterized strain library and a suite of assays and screens, bioinformatics and computational tools, and databases, which facilitate our insights into the human microbiome. We have established proprietary, curated, reference databases and algorithms that: (i) integrate high-resolution genomic, metagenomic, metabolomic, and transcriptomic data sets, as well as data from in vitro and human cell-based functional screening assays, and in vitro/ex vivo and in vivo disease models, and (ii) enable us to track changes in the microbiome at the level of microbial species and individual strains and associate these changes with changes in the metabolic state of the gut and host physiology at the level of specific functional pathways. Our analytics leverage machine learning to integrate gene profiling and metabolomics data (the small molecules made by the microbiome) with genomic data (the collection of microbes defined by sequencing) to delineate microbiome biomarkers (the specific species or strains and metabolites or functional pathways) that contribute to the state of disease or health. Additionally, leveraging all of these data we have curated and continue to maintain and expand a graphical database, or graphDB, that links and associates: (i) functional properties of microbial species/strains, (ii) functional pathways in hosts that can be modulated by the microbiome, (iii) the association of functional pathways to disease, and (iv) the association of existing non-microbiome drugs to the functional pathways. This continually growing graphDB is structured to be efficiently mined using machine learning and artificial intelligence algorithms to inform drug targets, drug design and optimization, and disease area and patient population prioritization. Further, this platform extends from preclinical design to clinical assessment of pharmacokinetics and pharmacodynamics of live biotherapeutics, enabling seamless translation from bench to bedside.

Our proprietary strain library of bacterial isolates from healthy donors and patients enables us to translate microbiome biomarker insights into defined consortia of bacteria. The strain library contains bacterial species isolated from individuals that are either healthy or that have a disease. We have developed extensive isolation and cultivation know-how. The strain library contains a majority of the Human Microbiome Project’s “most wanted” species and many novel species we believe are not described in other databases nor found in other culture collections. The functional properties of strains are characterized using proprietary in vitro and ex vivo human cell-based assays as well as full-genome sequences and genome functional annotation. Functional characterization of target strains includes properties such as how the bacteria interact with human colonic epithelial cells and human immune cells. We also seek to understand how these microbes improve the health of epithelial barrier cells in the gut and how they may modulate immune responses.

We select bacteria from our library with specific predicted properties using novel algorithms for in silico functional design and optimization and grow the compositions in the lab to be tested both in vitro/ex vivo models as delineated above and in invivo animal models. Our animal models include conventional mice, germ-free mice, and “microbiome humanized avatar” mice that possess only bacteria derived from humans; these models were developed to minimize confounding variables presented by model organism microbes. Data from our in vitro/ex vivo and in vivo screens are analyzed and used to optimize compositional designs; introducing new bacterial strains and optimizing existing strains until we identify a lead composition with the desired profile and that is suitable for clinical testing.

We manufacture the bacterial composition under current Good Manufacturing Practices, or cGMP, or similar foreign requirements, which are required by FDA and foreign regulators. We believe our unique manufacturing capacities, including our cultivation and quality systems, position us to exploit the insights of our proprietary human data and the novel biology of species and strains that have not previously been used for therapeutics. We have optimized fermentation conditions to generate spores and enhance bacterial yields in anaerobic fermentation and have in-house capabilities to formulate both spores and live non-spore bacteria. Our manufacturing facility in Cambridge, Massachusetts was designed to be fit-for-purpose and is highly differentiated compared to the offerings of commercial contract research organizations.

In addition, we believe our clinical development strategy represents a differentiated strategic advantage. Over more than a decade, we have established and maintained a broad and well-connected network of leading medical experts and principal investigators at academic medical centers, transplant centers, and other specialty clinical sites with deep expertise in microbiome science, immunology, infectious diseases, oncology, and gastrointestinal disorders. We believe this network, developed in part through our long-standing collaboration with Memorial Sloan Kettering Cancer Center, positions us to pursue a “light and fast” first-in-human and first-in-patient development paradigm. By leveraging investigator-sponsored studies, where appropriate, we can efficiently generate early clinical proof-of-mechanism and biomarker data in high priority and well-defined patient populations, refine dose strategies, and inform registrational development pathways while maintaining capital discipline. We believe this model enhances our ability to rapidly translate preclinical insights into human data, prioritize assets with the highest probability of success, and accelerate decision-making across our portfolio. Additionally, we have experience utilizing clinical trial strategies to advance the pipeline including but not limited to incorporation of adaptive designs, patient stratification, designing protocols with a patient-centric focus to reduce patient burden, use of historical comparator cohorts, and will consider other approaches including basket, umbrella and seamless designs as part of clinical development efforts.

Taken together, we believe our platform, spanning drug discovery, preclinical translation, and novel manufacturing and quality control approaches, has enabled a field leading pipeline across a range of therapeutics areas.

Disease Overview and Our Product Pipeline

We believe our LBP candidates represent a novel approach with potential application across a broad range of human diseases. We led the successful development and approval of VOWST, the first FDA-approved orally administered microbiome therapeutic and a Breakthrough Therapy designated drug, which was sold to Nestlé Health Science in September 2024. SER-155, our most advanced LBP candidate, is an investigational, oral, live biotherapeutic designed to decolonize GI pathogens, improve GI epithelial barrier integrity, and induce immune homeostasis to prevent BSIs, including those that can harbor AMR, as well as other pathogen-associated negative clinical outcomes in patients undergoing allo-HSCT. In our placebo-controlled Phase 1b study of SER-155 in allo-HSCT, Cohort 2 results demonstrated that SER-155 was associated with a 77% relative risk reduction in bacterial BSIs and a significant reduction in systemic antibiotic exposure as well as a lower incidence of febrile neutropenia, as compared to placebo through day 100 post-HSCT. SER-155 was generally well tolerated, with no observed treatment-related serious adverse events. In December 2024, the FDA granted Breakthrough Therapy designation to SER-155 for the reduction of BSIs in patients 18 years and older undergoing allo-HSCT. In January 2025, we reported exploratory translational biomarker data from the SER-155 Phase 1b study which provided evidence supporting the intended therapeutic mechanisms, including promotion of intestinal epithelial barrier integrity to reduce the potential of bacterial translocation into the bloodstream, and reduction of systemic inflammatory responses. Results from this exploratory biomarker analysis showed that SER-155 was associated with lower levels of fecal albumin and lower concentrations of various plasma biomarkers associated with systemic inflammation (i.e., IFN-y, TNF-α, IL-17, and IL-8) in the HSCT peri-transplant period, the period from the end of the first SER-155 treatment course through to neutrophil engraftment. The results support SER-155’s intended mechanisms of action and reinforce the previously reported promising clinical study efficacy and safety data. These

systemic inflammatory response observations further support the potential to develop our live biotherapeutics to address inflammatory and immune diseases, including UC and Crohn’s disease.

Following advancement of key startup activities for the SER-155 Phase 2 study in allo-HSCT, including the submission of a final protocol to the FDA in January 2026, study site evaluation and qualification with our CRO, and manufacturing of drug substance, we have paused additional investment in that program, preserving the optionality to efficiently restart the study, while continuing to seek funding for the Phase 2 study.

We have been collaborating with Memorial Sloan Kettering Cancer Center for over a decade on the impact of the gastrointestinal microbiome on immune related diseases and cancer; recently this long-standing collaboration included an IST evaluating SER-155 in 15 participants with irEC. irEC is among the most frequent and severe irAEs in recipients of ICI therapy and can be observed in up to 50% of patients, with rates varying based on cancer drug and treatment regimen. ICIs can cause a wide range of irAEs with links to T cell biology and epithelial barrier inflammation, both of which are biological functions shown in our preclinical and clinical pharmacology data to be positively impacted by SER-155. We expect to report initial clinical results, including preliminary safety, efficacy, pharmacology, and exploratory biomarker data in the second quarter of 2026. We believe data from this IST could further support the potential for live biotherapeutics to address a significant unmet need among the large population of cancer patients receiving ICIs and may further support evaluation of our biotherapeutic approach in this setting.

We believe that our cultivated live biotherapeutic candidates could be developed in additional patient populations to address barrier compromise and bloodstream and antimicrobial resistant infections, including autologous-HSCT patients, cancer patients with neutropenia, CAR-T, recipients, individuals with CLD, solid organ transplant recipients, as well as patients in the ICU and long-term acute care facilities. We continue to develop another proprietary live biotherapeutic composition, SER-147, designed to prevent bacterial bloodstream and SBP, infections in patients with metabolic disease, including CLD. Additionally, we are developing an oral liquid formulation based on SER-155 strains, for dosing in patients who cannot take oral capsules, such as intubated patients in the ICU, and other medically vulnerable patients at high risk of antimicrobial resistant infections, supported by a grant from CARB-X. We continue to leverage microbiome pharmacokinetic and pharmacodynamic data from across our clinical and preclinical portfolios, using our reverse translational development platform to prioritize future drug targets and to identify opportunities for monotherapy treatment and in combination with existing therapies across various indications, including inflammatory and immune diseases, cancer, and metabolic diseases.

Immunology and Inflammation

Irritable Bowel Disease and Ulcerative Colitis

UC, a form of IBD, is a relapsing-remitting chronic inflammatory disorder affecting the mucosal surface of the colon, leading to episodes of bloody diarrhea, urgency and mucosal inflammation (Danese and Fiocchi, 2011), which generally begins in young adulthood and endures for life. The incidence of UC is rising worldwide, and the prevalence of the disease is highest in the United States, Canada, and Europe. In the United States alone, the prevalence of UC is estimated to be 378 per 100,000, or approximately 1.25 million Americans (Lewis et al., 2023). The severity, extent, and duration of disease are also risk factors for developing colon cancer, which occurs at a rate as high as 0.5-1.0% per year, an important complication given the young age at which the disease

strikes. Patients with UC also experience increased risk of Clostridioides difficile infection, or CDI, and primary sclerosing cholangitis, compared to the general population (Dlalal & Allegretti, 2022).

The majority of current medical therapies for the treatment of UC suppress the immune system rather than target reducing the triggers of immune activation and promoting immune tolerance. We believe there remains an unmet need for safer agents with novel non-immunosuppressive mechanisms of action. Moreover, alternative therapy is needed for patients with UC who experience frequent flares, are intolerant to the aminosalicylate class of medication, or where there are safety concerns relating to the use of immunomodulator or steroid therapy.

Current IBD therapies primarily suppress immune responses rather than address upstream drivers of immune activation. Despite advances in biologics and small molecules, many patients fail to achieve durable remission, and a substantial subset experience incomplete response, loss of response over time, or safety limitations associated with chronic immunosuppression. Additionally, current therapeutic approaches in IBD do not address the potential role of microbiome functional disruptions in causing or aggravating disease in IBD. However, not all patients with IBD present with microbiome disruption; many patients with IBD demonstrate comparable taxonomic and functional microbiome diversity to healthy subjects (Lloyd-Price 2019). Similarly, pre-clinical models have shown that microbiomes from patients with IBD drive variable immune responses, with only a subset of microbiomes resulting in inflammation (Hart et al. 2017; Britton et al. 2019). These data suggest that the microbiome may play a role in a subset of subjects with IBD.

Data from our SER-287 Phase 2b study and the first cohort of subjects from our SER-301 Phase 1b study in patients with mild-to-moderate UC suggest that the pharmacodynamic effects observed for SER-287 and SER-301 were greater in a subset of patients. Based on these results, we continue to advance research and development activities supported by partnerships to evaluate the potential to utilize biomarker-based patient selection and stratification in future clinical development efforts in IBD, and to further optimize our live biotherapeutic lead candidates. In October 2023, we were awarded a $500,000 grant from the CCF to leverage our clinical results and biological mechanism insights to functionally characterize subpopulations and to define associated biomarkers for IBD patient selection and stratification of patients where the GI microbiome plays an active role in inflammation and could be modified to reduce colitis. Our preclinical studies conducted to date have recapitulated the patient subpopulation observations from the previously run trials and progressed associated biomarker delineation of the populations, as well as confirmed a microbiome-driven functional link to disease. These research efforts aim to prioritize inflammatory targets for future clinical trials and evaluate the potential to utilize biomarker-based patient selection and stratification for these future studies.

SER-603

SER-603 is an investigational live biotherapeutic designed to improve response rates and durability of remission in patients with IBD, including UC and Crohn's disease. SER-603 is being developed for use as either a stand-alone therapy in mild-to-moderate disease or as a mechanism-distinct adjunctive therapy in combination with biologics or small molecules in moderate-to-severe disease. The program leverages our prior clinical experience in UC, including learnings from SER-287 and SER-301, and incorporates biomarker-driven patient stratification and optimized microbiome conditioning strategies.

SER-603 is in preclinical development, with IND-enabling activities ongoing. The program is supported by translational analyses from prior clinical studies and by preclinical studies that have recapitulated microbiome-defined patient subpopulation observations. We continue to evaluate biomarker-based patient selection approaches and functional characterization strategies to inform future clinical development.

Emerging clinical and preclinical evidence suggests that microbiome functional disruption contributes to disease activity in a defined subset of IBD patients. Observational and translational data from our prior SER-287 Phase 2b study and SER-301 Phase 1b study indicate that pharmacodynamic responses were greater in microbiome-defined subpopulations. These findings, along with external data demonstrating heterogeneity in microbiome-associated inflammatory responses, support the development of targeted, biomarker-informed live biotherapeutic strategies. We have discovered more than fifty GI bacterial features linked to inflammatory outcomes and have nominated and validated microbe associated biomarkers that can predict a response to current advanced therapies for IBD. Leveraging these biomarkers and our integrated preclinical and clinical data sets, SER-603 is optimized to address epithelial barrier dysfunction and microbiome-driven inflammation without systemic immunosuppression.

Given the chronic nature of IBD and continued unmet need for safe, durable, and non-immunosuppressive treatment options, we believe SER-603 has the potential to address a substantial commercial opportunity. SER-603 targets multiple segments of the IBD market, including moderate-to-severe UC (approximately 300,000-400,000 patients in the United States) as combination therapy with current standards of care, moderate-to-severe Crohn's disease in combination therapy setting, and mild-to-moderate UC and Crohn's disease as potential monotherapy.

Immune checkpoint-related enterocolitis (irEC)

IrEC is among the most frequent and severe irAEs in recipients of immune checkpoint-inhibitor therapy and can be observed in up to 50% of patients with rates varying based on cancer drug and treatment regimen. Immune checkpoint inhibitors can cause a wide range of irAEs with links to T cell biology and epithelial barrier inflammation, both of which are biological functions shown in

our preclinical and clinical pharmacology data to be positively impacted by SER-155. We believe that supportive data from this study could provide further support for the expansion of indications that may be well suited for our biotherapeutic approach.

Immune checkpoint inhibitors are a commonly used class of drugs that promote anti-tumor immune activity for cancer treatment. irEC represents a growing and underserved market driven by the rapid expansion of ICI use across oncology. Importantly, irEC shares substantial pathophysiologic overlap with inflammatory bowel disease (IBD), including epithelial barrier dysfunction, dysregulated mucosal immunity, and microbiome perturbation. This biological convergence enables clinical, regulatory, and commercial synergies between irEC and IBD development programs. With approximately 500,000 patients using ICI globally, approximately 50,000 to 100,000 are anticipated to experience clinically significant irEC. irEC rates vary, with rates highest in CTLA-4-based and combination therapies (~50%); grade 2+ irEC can lead to discontinuation of therapy, risking further cancer progression.

SER-155 in irEC

SER-155 is currently being evaluated as a first-in-class live biotherapeutic candidate for the treatment of Grade 2–3 immune checkpoint inhibitor-related enterocolitis (irEC) as a result of ICI therapy. The program is designed to promote mucosal healing and modulate inflammation without systemic immunosuppression, with the goal of reducing or eliminating the need for high-dose corticosteroids, which carry the risk of toxicity and ICI efficacy impact. We believe SER-155 could be a first-in-class therapy as current approaches manage toxicity reactively with immunosuppression, which can negatively impact cancer treatment.

We are nearing completion of a single-arm, open-label Phase 1b investigator-sponsored trial conducted with Memorial Sloan Kettering Cancer Center evaluating SER-155 as first-line treatment of irEC. The study was fully enrolled (n=15) in early 2026, and we expect to report initial clinical results, including preliminary safety, efficacy, pharmacology, and exploratory biomarker data in the second quarter of 2026.

Infection Risk Reduction

We continue to be invested in the infectious disease space, with a renewed focus on leveraging our existing clinical data, translational insights, and manufacturing capabilities to support targeted development efforts across a defined set of related indications. We believe that the scientific and clinical data from our VOWST program (our then product candidate SER-109 program) validate our novel approach of using live biotherapeutics to decolonize pathogens and improve epithelial barrier integrity, resulting in reduced rate of infections in medically compromised patients. Data from the ECOSPOR III and ECOSPOR IV Phase 3 trial published in the New England Journal of Medicine (Feuerstadt et al., 2022) and Journal of the American Medical Association (Sims et al., 2023) suggest that live biotherapeutics have the potential to restructure the gut microbiome and shift the gut metabolic landscape. Additional data show that VOWST rapidly reduced the abundance of bacteria associated with common antibiotic resistance genes, or ARGs, and reduced ARG abundance in the gut (Straub et al., 2023). Collectively, we believe these data suggest the potential for live biotherapeutics to prevent the colonization and overgrowth of pathogens that can establish in the gut and ultimately to reduce infections. We believe that reducing pathogen colonization in the GI and improving GI epithelial barrier integrity to reduce the risk of infection may be replicable in a range of medically compromised patients, protecting them from infections and resulting downstream clinical sequelae.

We believe this approach may also enable us to reduce AMR, which the World Health Organization declared as a top ten global public health threat facing humanity, and with estimates that yearly deaths may reach 10 million by 2050, putting mortality due to AMR on par with deaths due to cancer. Recently, two manuscripts were published in Nature Medicine (Bryant et al. 2026) and the Journal of Infectious Diseases (Bryant et al. 2025) highlighting new insights into the functional mechanism and clinical impact of VOWST. The Nature Medicine article, titled “The impact of an oral purified microbiome therapeutic on the GI microbiome”, confirmed our pharmacological hypotheses from earlier VOWST studies, with higher VOWST dosing associated with enhanced pharmacokinetics, as assessed by faster and more robust therapeutic species engraftment in the gut. Treatment also significantly altered the composition of the intestinal microbiome and microbe-associated metabolites, including decreased primary and increased secondary bile acids, as well as elevated short- and medium-chain fatty acids, functional changes that inhibit C. difficile spore germination and vegetative growth. Further, in vitro analyses confirmed that VOWST batches induced production of these metabolites that disrupt C. difficile life cycle and growth. Collectively, these findings support VOWST’s role in restoring microbe-associated metabolic functions critical to preventing CDI recurrence. A complementary publication in the Journal of Infectious Diseases, titled “Comparability of Gastrointestinal Microbiome and Bile Acid Profiles in Patients With First or Multiply Recurrent Clostridioides difficile Infection”, reported a post hoc analysis of the ECOSPOR IV Phase 3 trial, evaluating differences in gastrointestinal microbiome and bile acid profiles between patients experiencing a first recurrence C. difficile infection (frCDI) versus multiply recurrence infection (mrCDI). These data demonstrate that the underlying functional disease etiology is consistent in both first and multiply recurrent CDI patient populations, with VOWST demonstrating similar efficacy and drug pharmacology across the broad patient population.

We believe these data provide important clinical translation and further demonstrate the potential of live biotherapeutics to target specific microbiome functions that are linked to serious disease, including those that are not effectively treated with other drug modalities. The underlying data supporting these publications was developed using Seres MbTx platform, which provides high-resolution assessment of drug pharmacology and functional mechanism of action. These data on bacterial function and pharmacology

anchored the preclinical development of SER-155 and inform the continued development of Seres’ pipeline of next-generation live biotherapeutic products.

SER-155 in allo-HSCT

We are developing SER-155, an investigational, oral, live biotherapeutic designed to decolonize GI pathogens, improve GI epithelial barrier integrity, and induce immune homeostasis to prevent bacterial BSIs as well as other pathogen associated negative clinical outcomes in patients undergoing allo-HSCT. SER-155 is a live biotherapeutic candidate designed to prevent frequent, expensive, and fatal infections in blood cancer patients.

SER-155 contains 16 bacterial strains selected using our reverse translation discovery and development platform technologies to optimize SER-155’s targeted profile. The design incorporates biomarker data from human clinical data and screening data from nonclinical human cell-based assays and in vivo disease models. The bacteria consortia is designed to optimize: (i) the prevention of the growth of various Enterococcaceae and Enterobacteriaceae species known to potentially dominate the GI tract and lead to downstream negative clinical outcomes in medically compromised patients and that can harbor antibacterial resistance, (ii) the production of multiple bacterial metabolites that can promote mucosal and epithelial barrier integrity with the goal of reducing the likelihood of harmful bacteria translocating from the gut to the bloodstream through a compromised epithelium, and (iii) the production of multiple bacterial metabolites that can modulate immune pathways to induce immune tolerance with a potential impact on GvHD.

The rationale for this program is based in part on published clinical evidence from our collaborators at Memorial Sloan Kettering Cancer Center showing that allo-HSCT patients with decreased diversity of commensal microbes and pathogen domination in the GI tract were significantly more likely to die due to infection and/or lethal GvHD (Peled et al., 2020). There are an estimated 40,000 allo-HSCT procedures annually worldwide, and infection is one of the most common causes of mortality in these patients. The Center for International Blood & Marrow Transplant Research, or CIBMTR, reports that 19-28% of deaths in allo-HSCT patients over 18 years of age within 100 days post-transplant are caused by infections and 5-14% by GvHD. In December 2023, we received Fast Track Designation for SER-155 to reduce the risk of infection and GvHD in allo-HSCT patients. In December 2024, the FDA granted Breakthrough Therapy designation for SER-155 for the reduction of BSIs in patients 18 years and older undergoing allo-HSCT.

SER-155 Phase 1b Study (including placebo-controlled Cohort)

SER-155 has been evaluated in a Phase 1b study in patients undergoing allo-HSCT. The SER-155 Phase 1b study included two cohorts. Cohort 1 was designed to assess safety and drug pharmacology, specifically the drug strain engraftment in the GI tract. Cohort 1 included 13 subjects who received any dosing of the SER-155 regimen, with 11 subjects subsequently receiving an allo-HSCT. Results from this cohort, announced in May 2023, showed SER-155 was generally well tolerated and resulted in successful drug strain engraftment and a reduction in pathogen domination in the GI microbiome relative to a historical control cohort.

Study Cohort 2 utilized a randomized, double-blinded 1:1 placebo-controlled design to further evaluate safety and drug strain engraftment, as well as key secondary and exploratory endpoints such as the incidence of bacterial bloodstream infections and related medical consequences such as febrile neutropenia and antibiotic use. Cohort 2 included 45 patients in the intention-to-treat (ITT) population. Of the ITT population, 20 received SER-155 and 14 received placebo, each of whom subsequently received an allo-HSCT, with data available for clinical evaluation through day 100, the study’s prespecified primary observation point. Exploratory hypothesis testing was conducted at the two-sided α=0.05 level. Ninety-five percent (95%) 2-sided confidence intervals (CIs) were determined, where specified. No adjustment for multiplicity was done. A subset of patient samples was available for drug pharmacology analysis.

The median age in Cohort 2 was 63, and most subjects had acute myeloid leukemia, acute lymphocytic leukemia, myelodysplastic syndrome or myeloproliferative neoplasia as their primary disease and received reduced-intensity conditioning pre-transplant. Most patients received peripheral blood stem cells from a matched unrelated donor. A majority received post-transplant cyclophosphamide as part of their GvHD prophylaxis.

Results from Cohort 2, announced in September 2024, were consistent with the observations from Cohort 1. SER-155 was generally well tolerated, and no treatment-emergent serious adverse events related to drug were observed. SER-155 bacterial strains engrafted into the gastrointestinal tract of patients following the administration of SER-155.

The incidence of BSIs was significantly lower in the SER-155 arm compared with the placebo arm (2/20 (10%) vs. 6/14 (42.9%), respectively; [Odds Ratio: 0.15; 95% CI: 0.01, 1.13, p=0.0423]), which represents a relative risk reduction of approximately 77% and an absolute risk reduction of approximately 33%. In addition, while treatment antibiotic starts were similar in each arm, patients administered SER-155 were treated with antibiotics for a significantly shorter cumulative duration compared to patients in the placebo arm (9.2 days vs. 21.1 days, respectively, with a mean difference of -11.9 days [95% CI: -23.85, -0.04; p=0.0494]). The incidence of febrile neutropenia was lower in patients administered SER-155 compared to placebo (65% vs. 78.6%, respectively; [Odds Ratio: 0.51; 95% CI: 0.07, 2.99; p=0.4674]). Six cases of GI infections (C. difficile infections) were observed in the study, with four cases (20%) in the SER-155 arm and two cases (14.3%) in the placebo arm.

Recent changes in the allo-HSCT standard of care and the increasing use of post-transplant cyclophosphamide as part of prophylactic therapy for GvHD have reduced rates of GvHD overall in this patient population. The rates of GvHD in the study were low, with two cases of grade 2 GvHD observed in each arm, and no cases of grade 3 or 4 GvHD were observed.

In Cohort 2, the ability to detect pathogen domination (i.e., relative abundance in the GI ≥30%) in the placebo arm, and differences between the study arms, was constrained due to the limited number of placebo stool samples and an imbalance in the number of available stool samples between the arms. Observed pathogen domination events were low in the placebo and SER-155 arms with no significant differences identified. In a comparison of the prevalence of pathogen domination versus a larger allo-HSCT historical control cohort, pathogen domination in SER-155 subjects was substantially lower, providing further evidence of SER-155 activity.

We believe the available study data from Cohort 1 suggest that SER-155 administration results has the potential to significantly lower incidence rates of gastrointestinal dominations with pathogens of clinical concern, such as Enterococcaceae, Enterobacteriaceae, Streptococcaceae, and Staphylococcaceae. We further believe the resulting Cohort 2 data, together with the Cohort 1 SER-155 Phase 1b study results provide encouraging evidence to support further development of SER-155 to potentially reduce GI associated bloodstream and AMR infections as well as increase immune tolerance in individuals undergoing allo-HSCT for cancers and other serious conditions.

Proposed SER-155 Phase 2 Study

The SER-155 Phase 2 study will incorporate a well-powered, placebo-controlled design, which provides for a planned interim analysis to enable an expedited initial data readout. The SER-155 Phase 2 study is expected to enroll approximately 248 participants and incorporate an adaptive design and an interim data analysis when approximately half of the enrolled participants have reached the primary endpoint. We expect to obtain the interim clinical results within twelve months following study initiation, which we believe will facilitate timely engagement with the FDA on the design of a Phase 3 study and inform development in adjacent medically vulnerable patient populations. We believe that positive results, if achieved, from the Phase 2 study could enable advancement into a single Phase 3 trial to support registration.

Following advancement of key startup activities for the SER-155 Phase 2 study in allo-HSCT, including the submission of a final protocol to the FDA in January 2026, study site evaluation and qualification with our CRO, and manufacturing of drug substance, we have paused additional investment in that program while continuing to seek funding for the Phase 2 study.

We continue our efforts to obtain capital and other resources to support further development of SER-155 and our broader portfolio of live biotherapeutic product candidates with applications for inflammatory diseases. We are evaluating a range of potential deal structures that we believe could leverage our live biotherapeutics expertise and success, as demonstrated by bringing VOWST from early development through FDA approval.

In October 2025, we presented new post hoc data from our SER-155 Phase 1b trial in an oral presentation at IDWeek in Atlanta, Georgia. The presentation included new post-hoc analysis from the completed SER-155 Phase 1b study describing differences between the SER-155 and placebo groups, including the bacterial and fungal organisms causing BSIs, BSI event clinical outcomes, antibacterial prophylaxis use, and patterns of AMR among the bacterial BSI organisms. These new data illustrated that BSIs occurred despite antibacterial prophylaxis, and that BSI bacteria exhibited AMR. Resistance to multiple antibacterial agent classes was observed only in the BSI bacteria from placebo-treated participants, two of whom had fatal outcomes related to their BSIs. These new data further support the potential of SER-155 as an innovative alternative approach to the significant unmet medical need for prevention of BSIs in HSCT patients, especially those BSIs associated with AMR that increases the risk of morbidity and mortality.

Exploratory biomarker data

In January 2025, we reported exploratory translational biomarker data from the SER-155 Phase 1b study which provided evidence supporting the intended therapeutic mechanisms, including promotion of intestinal epithelial barrier integrity to reduce the potential of bacterial translocation into the bloodstream, and reduction of systemic inflammatory responses. Results from this exploratory biomarker analysis showed that SER-155 was associated with lower levels of fecal albumin and lower concentrations of various plasma biomarkers associated with systemic inflammation (i.e., IFN-y, TNF-α, IL-17, and IL-8) in the HSCT peri-transplant period, the period from the end of the first SER-155 treatment course through to neutrophil engraftment. The results support SER-155’s intended mechanisms of action and reinforce the previously reported promising clinical study efficacy and safety data. These systemic inflammatory response observations further support the potential to develop our live biotherapeutics to address inflammatory and immune diseases, including ulcerative colitis and Crohn’s disease.

In February 2025, clinical and biomarker results from our biotherapeutic programs were presented as a poster at the 2025 Tandem Transplantation & Cellular Therapy Meetings of the American Society for Transplantation and Cellular Therapy (ASTCT) and Center for International Blood and Marrow Transplant Research (CIBMTR). SER-155 Phase 1b clinical study data were also featured in an oral presentation in the Best Abstracts in Infectious Diseases track at the Tandem meeting.

In April 2025, we presented SER-155 Phase 1b clinical and exploratory biomarker results at the 51st annual meeting of the

European Society for Blood and Marrow Transplantation, or EBMT. Our presented poster was recognized by the EBMT scientific organizing committee and obtained the “Best Clinical Poster Award.”

In May 2025, we presented data at the Digestive Disease Week, or DDW conference highlighting preclinical and clinical data that enable identification of patients with a disease etiology linked to the gastrointestinal microbiome, and the identification of microbiome-based biomarkers that are predictive of response and suitable for patient selection and stratification in clinical trials. Our poster, entitled “Candidate Biomarkers of Microbiome Disruption for Patient Selection or Stratification in Clinical Trials of Microbiome Therapies in Ulcerative Colitis” received a Poster of Distinction award in the Microbiome and Microbial Therapies subgroup. We believe that the data generated suggest that live biotherapeutics could provide a novel treatment modality that could benefit patients living with gut-related inflammatory and immune diseases that are not effectively addressed today. Furthermore, research indicates that specific patient subpopulations optimally suited for biotherapeutic-based treatments may be identifiable. We are exploring options, including potential partnerships, to advance the development of our biotherapeutics in inflammatory and immune diseases, including ulcerative colitis and Crohn’s disease.

In May 2025, we presented new exploratory biomarker data from the SER-155 Phase 1b study in a poster session at the 2025 American Society of Clinical Oncology, or ASCO, Annual Meeting. The biomarker data presented at ASCO demonstrate the potential of SER-155 to promote immune reconstitution following allo-HSCT by modulating homeostatic cytokines and peripheral T-cell expansion. In post hoc analyses from the SER-155 Phase 1b study, significantly higher levels of the homeostatic cytokine IL-7 were observed both after the second course of SER-155 (administered after neutrophil recovery) and at HSCT Day 100, as compared to placebo. Additionally, a higher frequency of CD4+ T cells was observed in peripheral blood at these same timepoints in the SER-155 arm. We believe the results support the ability of SER-155 to promote peripheral T-cell recovery and immune reconstitution to support favorable outcomes post allo-HSCT.

We believe that exploratory biomarker data presented at recent medical meetings have supported the intended mechanisms of SER-155 and demonstrated the broader potential of live biotherapeutics in inflammatory and immune mediated diseases.

Oral Live Biotherapeutic Product - Liquid Formulation (LBP-LF)

In July 2025, we were awarded a grant from CARB-X to support the development of an oral liquid formulation of an LBP based on SER-155 (LBP-LF) for medically vulnerable patient populations at risk of BSIs, including AMR infections, who cannot be dosed with oral capsules, such as intubated patients in the ICU. The CARB-X grant provides us with up to $3.6 million of funding for research, manufacture, and design of a Phase 1 clinical trial in ICU patients. LBP-LF is designed to target the prevention of bloodstream infections in medical ICU patients by Escherichia coli and other gut-derived bacteria capable of harboring antibiotic resistance.

Up to 50% of all preventable medical ICU deaths have been attributed to infections with E. coli and other gut-derived bacteria (Mayr, 2006). These infections are also the leading cost in the medical ICU (Neidell, 2012). When ICU patients with multidrug resistant, or MDR, infections survive hospitalization, they have high long-term morbidity with over 20% 30-day readmission rates (Chang, 2015; Mayr, 2017). Over 5 million patients are admitted to ICUs in the U.S. annually, and these admissions account for approximately 20% of all acute care hospitalizations (Barrett et al. 2024). Infections with pathogenic, often MDR, bacteria are the leading cause of mortality in the medical ICU, causing up to 9 deaths for every 100 ICU patients admitted (Vincent, 2009). Most patients are admitted to the medical ICU with a known or suspected infection (i.e., sepsis) but, with targeted or empiric antibiotics, most recover from this initial infection. Once in the ICU, secondary, healthcare-associated infections frequently develop during the prolonged recovery from sepsis and are a significant driver of mortality.

LBP-LF is a novel approach that addresses both gut colonization and subsequent translocation by E. coli and other gut-derived pathogens to prevent a significant proportion of these secondary hospital acquired infections. LBP-LF is in preclinical development, with IND-enabling activities ongoing and IND-readiness targeted by the end of 2026. Development of LBP-LF is ongoing with grant support from CARB-X and in collaboration with Columbia University.

SER-147

We are also developing another proprietary live biotherapeutic composition, SER-147, designed to prevent bacterial bloodstream and spontaneous bacterial peritonitis, or SBP, infections in patients with metabolic disease, including chronic liver disease, or CLD. SER-147 was designed and optimized using our reverse translational therapeutics development platform.

CLD is a progressive condition marked by deterioration of liver function and is reaching epidemic proportions affecting nearly 1.7 billion people worldwide, causing substantial health burden on afflicted countries (GBD 2017 Cirrhosis Collaborators, 2020, Clinical Liver Disease, 2021). In the advanced stages of CLD, known as decompensated cirrhosis, patients exhibit significant immune dysfunction, microbiome disruption, and increased contact with the healthcare system, all of which drive increased susceptibility to bacterial infections such as SBP and BSIs (Bajaj et al., 2021, Albillos et al., 2022). Over 40% of patients with decompensated cirrhosis experience an infection within the first year of diagnosis. Antibiotics are the only prophylactic option for patients at high risk of infections like SBP, resulting in exposure to antibiotics for months or years. To combat increasing rates of AMR, antibacterial prophylaxis for primary SBP is no longer recommended for the majority of patients outside of very high-risk, leaving significant

unmet need. Many cultivated live biotherapeutics currently in clinic are constrained by formulation technologies incompatible with concomitant medications commonly used in CLD.

SER-147 is in preclinical development. The program is ready to progress to IND-enabling activities, including manufacturing, in order to advance to clinical development.

Manufacturing

The production of bacterial live biotherapeutic products is highly specialized. Owing to their hardiness and environmental persistence, production of aerobic and anaerobic vegetative bacteria, as well as spore-forming organisms, poses unique considerations for product, personnel, facility design, operation, quality assurance and quality control. Manufacturing activities with spores are subject to specialized regulations. We expect that a typical commercial fermentation will yield on the order of hundreds or thousands of doses per liter depending on the product and its composition. Additionally, because a given total dose contains multiple strains, the per-strain requirements for production may be even lower. As a result, we believe the relatively high productivity of our manufacturing processes relative to the dose level will enable production scales for both clinical and commercial supply to be modest by traditional industry standards for biologics and vaccine manufacturing.

We have developed supply chains for producing and testing materials to ensure the availability of future clinical trial supplies. Our development processes are designed to ensure that the raw materials, process technologies and analytical tests we use are scalable and transferable to a cGMP manufacturing environment. These include the following core elements:

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Fermentation. We use microscale screening to optimize culture conditions of the bacterial strains of interest in our current and foreseeable fermentation-based product candidates. These screens are designed to identify the fermentation platform that is best-suited for optimization and scale-up of the strains. Small-scale fermentation systems (0.1 L to 50 L) enable the optimization of a wide variety of culture conditions and have been demonstrated to be scalable to larger fermentation processes and enable technology transfer to clinical and final manufacturing sites. We employ platform fermentation processes as starting points for cGMP production processes and develop strain specific processes as required. To develop master cell banks, working cell banks, and bulk drug substance for commercial product, we are using bacterial strains that each originate from a unique research cell bank precursor, so we expect the research cell banks and final drug product should be genetically and physiologically similar.

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Purification. Similar to fermentation, we use small-scale purification operations to quickly assess downstream process yield, quality and robustness and believe these are scalable to large-scale cGMP manufacturing of live cells and spores based on historical performance during internal clinical manufacturing campaigns. Our products in development are predominantly oral dosage forms containing spores and/or live bacteria, hence purification is typically less complex than for parenteral biologics such as monoclonal antibodies that must separate highly similar components from the culturing process. Separation of viable microbes from soluble fermentation broth components is typically much simpler by comparison.

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Formulation. Our live biotherapeutic candidates are combinations of bacteria and can be administered by a number of methods and by different routes. Where possible, our product formulation development is focused on oral delivery for patient convenience. The primary goal in developing a formulation is to deliver bacteria to the intended location in a condition where they are able to replicate and modulate the microbiome. Formulation development generally uses approved excipients and preservatives with pharmaceutical industry precedent, and will include screening of liquid, solid, and suspension formulations to maximize the opportunity for extended stability with minimal cold-chain requirements. Dosage forms for oral products may be liquid- or powder-filled capsules, tablets, sachets, or liquid containers.

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Analytical. We are addressing quality control requirements for our live biotherapeutic candidates using proprietary microbiological, chemical, biochemical, and molecular sequence-based testing schemes. We have available and are further developing quality control, environmental monitoring and in-process analytical tools that can quantitatively measure the composition of spore, vegetative microbe and spore/vegetative combinations, which we believe enable a wide variety of drug products to be manufactured. Throughout the bioprocess and formulation development platform we use and will expand on quantitative analytics to assess the identity, potency and purity of the final product.

We have cGMP manufacturing capabilities at our Cambridge, Massachusetts locations where we conduct cGMP manufacture of therapeutic candidates to support both drug substance and drug product manufacturing for early-phase and late-phase clinical development. Our current live biotherapeutic pipeline assets, including SER-155 and SER-603, are manufactured from standard clonal cell banks via cultivation. We may establish further manufacturing capabilities and facilities that will serve late-phase clinical and commercial supply for our product candidates. We may do this by expanding our current facilities, or by purchasing or building additional facilities. We also use contract manufacturing and testing organizations to supplement our internal capacity.

Material Agreements

For a description of our material agreements, see “Management’s Discussion and Analysis of Financial Condition and Results of Operations – Liquidity and Capital Resources" in Part II, Item 7 of this Annual Report on Form 10-K.

Intellectual Property

We strive to protect the proprietary technology that is important to our business, including seeking and, if granted, maintaining patents intended to cover our product candidates and compositions, their methods of use and processes for their manufacture and any other aspects of inventions that are commercially important to the development of our business. We also utilize regulatory exclusivity as well as trade secrets to protect aspects of our business.

We plan to continue to expand our intellectual property estate by filing patent applications directed to compositions, methods of treatment, methods of manufacture and methods for patient selection created or identified from our ongoing development of our product candidates. Our success will depend on our ability to obtain and maintain patent and other proprietary protection for commercially important technology, inventions and know-how related to our business, defend and enforce any patents that we may obtain, preserve the confidentiality of our trade secrets and operate without infringing the valid and enforceable patents and proprietary rights of third parties. We also rely on know-how and continuing technological innovation to develop and maintain our proprietary position and, in the future, may rely on or leverage in-licensing opportunities. We seek to obtain domestic and international patent protection, and endeavor to promptly file patent applications for new commercially valuable inventions.

The patent positions of biopharmaceutical companies like us are generally uncertain and involve complex legal, scientific and factual questions. In addition, the coverage claimed in a patent may be challenged in courts after issuance. Moreover, many jurisdictions permit third parties to challenge issued patents in administrative proceedings, which may result in further narrowing or even cancellation of patent claims. We cannot predict whether the patent applications we are currently pursuing will issue as patents in any particular jurisdiction or at all, whether the claims of any patent applications, should they issue, will cover our product candidates, or whether the claims of any issued patents will provide sufficient protection from competitors or otherwise provide any competitive advantage.

Because patent applications in the United States and certain other jurisdictions are maintained in secrecy for 18 months or potentially even longer, and because publication of discoveries in the scientific or patent literature often lags behind actual discoveries and patent application filings, we cannot be certain of the priority of inventions covered by pending patent applications. Accordingly, we may not have been the first to invent the subject matter disclosed in some of our patent applications or the first to file patent applications covering such subject matter, and we may have to participate in interference proceedings or derivation proceedings declared by the United States Patent and Trademark Office, or USPTO, to determine priority of invention.

Our patent portfolio includes issued U.S. patents and patent applications in various stages of prosecution, including ex-U.S. international counterparts. We believe that issued claims will provide protection for our live biotherapeutic candidates.

Patent Term

The base term of a U.S. patent is 20 years from the filing date of the earliest-filed non-provisional, patent application from which the patent claims priority. The term of a U.S. patent can be lengthened by patent term adjustment, which compensates the owner of the patent for administrative delays at the USPTO. In some cases, the term of a U.S. patent is shortened by terminal disclaimer that reduces its term to that of an earlier-expiring patent.

The term of a U.S. patent may be eligible for patent term extension under the Drug Price Competition and Patent Term Restoration Act of 1984, referred to as the Hatch-Waxman Act, to account for at least some of the time the drug is under development and regulatory review after the patent is granted. With regard to a drug for which FDA approval is the first permitted marketing of the active ingredient, the Hatch-Waxman Act allows for extension of the term of one U.S. patent that includes at least one claim covering the composition of matter of such an FDA-approved drug, an FDA- approved method of treatment using the drug and/or a method of manufacturing the FDA-approved drug. The extended patent term cannot exceed the shorter of five years beyond the non-extended expiration of the patent or fourteen years from the date of the FDA approval of the drug, and a patent cannot be extended more than once or for more than a single product. During the period of extension, if granted, the scope of exclusivity is limited to the approved product for approved uses. Some foreign jurisdictions, including Europe and Japan, have analogous patent term extension provisions, which allow for extension of the term of a patent that covers a drug approved by the applicable foreign regulatory agency. In the future, if and when our product candidates receive FDA approval, we expect to apply, if appropriate, for patent term extension on patents covering those product candidates, their methods of use and/or methods of manufacture.

Trade Secrets

In addition to patents, we rely on trade secrets and know-how to develop and maintain our competitive position. We typically utilize trade secrets to protect aspects of our business. We protect trade secrets and know-how by establishing confidentiality agreements and invention assignment agreements with our employees, consultants, scientific advisors, contractors and collaborators. These agreements provide that all confidential information developed or made known during the course of an individual or entities’

relationship with us must be kept confidential during and after the relationship. These agreements also provide that all inventions resulting from work performed for us or relating to our business and conceived or completed during the period of employment or assignment, as applicable, shall be our exclusive property. In addition, we take other appropriate precautions, such as physical and technological security measures, to guard against misappropriation of our proprietary information by third parties.

Competition

The development and commercialization of new drug and biologic products is highly competitive and is characterized by rapid and substantial technological development and product innovations. We face competition with respect to our current product candidates and will face competition with respect to any product candidates that we may seek to develop or commercialize in the future from major pharmaceutical companies, specialty pharmaceutical companies and biotechnology companies worldwide. We are aware of a number of large pharmaceutical and biotechnology companies, as well as smaller, early-stage companies, that are pursuing the development of products, including live biotherapeutics, and disease indications we are targeting. Potential competitors also include academic institutions, government agencies and other public and private research organizations that conduct research, seek patent protection and establish collaborative arrangements for research, development, manufacturing and commercialization.

Many of the companies against which we are competing or against which we may compete in the future have significantly greater financial resources, established presence in the market and expertise in research and development, manufacturing, preclinical testing, conducting clinical trials, obtaining regulatory approvals and marketing approved products than we do. Mergers and acquisitions in the pharmaceutical and biotechnology industries may result in even more resources being concentrated among a smaller number of our competitors.

These third parties compete with us in recruiting and retaining qualified scientific, clinical, manufacturing sales and 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.

The key competitive factors affecting the success of the product candidates that we develop, if approved, are likely to be their efficacy, safety, convenience, price, the level of competition and the availability of reimbursement from government and other third-party payors.

Our commercial opportunity could be reduced or eliminated if our competitors develop and commercialize products that are more effective, have fewer or less severe side effects, are more convenient or are less expensive than any products that we may develop. Our competitors also may obtain FDA or other regulatory approval for their products more rapidly than we may obtain approval for ours, which could result in our competitors establishing a strong market position before we are able to enter the market, especially for any competitor developing a live biotherapeutic which will likely share our same regulatory approval requirements. In addition, our ability to compete may be affected in many cases by insurers or other third-party payors seeking to encourage the use of lower cost products.

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 drugs and biologics such as those we are developing. We, along with our contract manufacturers, will be required to navigate the various preclinical, clinical and commercial approval requirements of the governing regulatory authorities of the countries in which we wish to conduct studies or seek approval for our product candidates. The process of obtaining regulatory approvals and ensuring subsequent compliance with appropriate federal, state, local and foreign statutes and regulations requires the expenditure of substantial time and financial resources.

In the United States, the FDA regulates drug and biologic products under the Federal Food, Drug and Cosmetic Act, its implementing regulations and other laws, including, in the case of biologics, the Public Health Service Act. Our product candidates are subject to regulation by the FDA as biologics. Biologics require the submission of a BLA and approval by the FDA before being marketed in the United States.

The process required by the FDA before our biologic product candidates may be marketed in the United States generally involves the following:

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completion of certain preclinical laboratory tests and animal studies performed in accordance with the FDA’s good laboratory practice, or GLP, regulations;

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submission to the FDA of an IND, which must become effective before clinical trials in the United States may begin;

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

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performance of adequate and well-controlled human clinical trials to establish the safety, purity and potency of the product candidate for each proposed indication, conducted in accordance with the FDA’s good clinical practice, or GCP, regulations;

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

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

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

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satisfactory completion of an FDA inspection of the manufacturing facility or facilities at which the product is produced to assess compliance with cGMP regulations, and to assure that the facilities, methods and controls are adequate to preserve the biological product’s continued safety, purity and potency;

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satisfactory completion of potential inspection of selected clinical investigation sites to assess compliance with GCPs; and

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FDA review and approval of the BLA prior to any commercial marketing, sale or shipment of the product.

Preclinical and Clinical Trials

Once a product candidate is identified for development, it enters the preclinical testing stage. Preclinical studies include laboratory evaluations of drug chemistry, formulation and stability, as well as studies to evaluate toxicity in animals, certain of which must be conducted in accordance with GLP requirements. The results of the preclinical studies, together with manufacturing information and analytical data, are submitted to the FDA as part of an IND. An IND is a request for allowance from the FDA to administer an investigational drug to humans. An IND must become effective before human clinical trials may begin. The IND automatically becomes effective 30 days after receipt by the FDA, unless the FDA, within the 30-day time period, raises concerns or questions about the conduct of the clinical trial, including concerns that human research subjects will be exposed to unreasonable health risks. In such a case, the IND sponsor and the FDA must resolve any outstanding concerns before the clinical trial can begin. Submission of an IND may result in the FDA not allowing clinical trials to commence or not allowing clinical trials to commence on the terms originally specified in the IND. A separate submission to an existing IND must also be made for each successive clinical trial conducted during product development, and the FDA allows the trial to proceed, either explicitly or implicitly by not objecting, before each clinical trial can begin.

Clinical trials involve the administration of the product candidate to human subjects under the supervision of qualified investigators in accordance with GCPs, which include among other things, the requirement that all research subjects provide their informed consent for their participation in any clinical study. Clinical trials are conducted under protocols detailing, among other things, the objectives of the clinical trial and the parameters and criteria to be used in monitoring safety and evaluating effectiveness. Each protocol must be submitted to the FDA as part of the IND. 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 drug, findings from animal or in vitro testing suggesting a significant risk to humans exposed to the drug, and any clinically important increased rate of a serious suspected adverse reaction compared to that listed in the protocol or investigator brochure.

An independent institutional review board, or IRB, for each investigator site proposing to participate in a clinical trial must also review and approve the clinical trial before it can begin at that site, and the IRB must monitor the clinical trial until it is completed. Some studies also include oversight by an independent group of qualified experts organized by the clinical study sponsor, known as a data safety monitoring board, which provides authorization for whether or not a study may move forward at designated check points based on access to certain data from the study and may halt the clinical trial if it determines that there is an unacceptable safety risk for subjects or other grounds, such as no demonstration of efficacy. The FDA, the IRB, or the sponsor may suspend or discontinue a clinical trial at any time on various grounds, including a finding that the subjects are being exposed to an unacceptable health risk. There are also requirements governing the reporting of ongoing clinical studies and clinical study results to public registries.

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

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Phase 1 — The investigational product is initially introduced into healthy human subjects or patients with the target disease or condition. These studies are typically 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.

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Phase 2 — The investigational product is typically 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.

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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 labeling.

In some cases, the FDA may condition approval of a BLA on the sponsor’s agreement to conduct additional clinical trials to further assess the biologic’s safety and effectiveness after BLA approval. Such post-approval clinical trials are typically referred to as Phase 4 clinical trials.

Concurrent with clinical trials, companies usually complete additional animal studies and must also develop additional information about the chemistry and physical characteristics of the biologic and finalize a process for manufacturing the biologic in commercial quantities in accordance with cGMP requirements. The manufacturing process must be capable of consistently producing quality batches of the product candidate and manufacturers must develop, among other things, methods for testing the identity, strength, quality and purity of the final biological 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.

BLA Submission and FDA Review

The results of preclinical studies and clinical trials, together with other detailed information, including extensive manufacturing information and information on the composition of the biologic, are submitted to the FDA in the form of a BLA requesting approval to market the biologic for one or more specified indications. The BLA must include all relevant data available from preclinical and clinical studies, including negative or ambiguous results as well as positive findings, together with detailed information relating to the product’s chemistry, manufacturing, controls, and proposed labeling, among other things. Data can come from company-sponsored clinical studies intended to test the safety and effectiveness of a use of the product, or from a number of alternative sources, including studies initiated by independent investigators. The submission of a BLA requires payment of a substantial user fee unless a waiver is granted or exemption applies.

In addition, the Pediatric Research Equity Act, or PREA, requires a sponsor to conduct pediatric clinical trials for most drugs and biologics, for a new active ingredient, new indication, new dosage form, new dosing regimen or new route of administration. Under PREA, original BLAs and certain supplements must contain a pediatric assessment unless the sponsor has received a deferral or waiver. The required assessment must evaluate the safety and effectiveness of the product for the claimed indications in all relevant pediatric subpopulations and support dosing and administration for each pediatric subpopulation for which the product is deemed safe and effective. The sponsor or FDA may request a deferral of pediatric clinical trials for some or all of the pediatric subpopulations. A deferral may be granted for several reasons, including a finding that the candidate is ready for approval for use in adults before pediatric clinical trials are complete or that additional safety or effectiveness data needs to be collected before the pediatric clinical trials begin. The FDA must send a non-compliance letter to any sponsor that fails to submit the required assessment, keep a deferral current or fails to submit a request for approval of a pediatric formulation.

Each BLA submitted to the FDA is reviewed for administrative completeness and reviewability within 60 days of the FDA’s receipt of the application. If the BLA is found to be complete, the FDA will file the BLA, triggering a full review of the application. The FDA may refuse to file any BLA that it deems incomplete or not properly reviewable at the time of submission. In this event, the BLA must be resubmitted with the additional information.

Once a BLA has been accepted for review, the FDA’s goal is to review standard applications within ten months after the filing date, or, if the application qualifies for Priority Review, six months after the FDA accepts the application for filing, but the overall timeframe may be extended for a period of three months for FDA to respond to new information deemed a “major amendment” to the application. The FDA reviews a BLA to determine, among other things, whether the biological product is safe, pure and potent and whether the facility or facilities in which it is manufactured meet standards designed to assure the product’s continued safety, purity and potency.

The FDA may also refer the application to an Advisory Committee for review, evaluation, and recommendation as to whether the application should be approved. The FDA is not bound by the recommendation of an advisory committee, but it generally follows such recommendations.

Before approving a BLA, the FDA will typically inspect the facility or the facilities at which the biologic product is manufactured and will not approve the product unless it determines that the manufacturing processes and facilities are in compliance with cGMP and adequate to assure consistent production of the product within required specifications. Additionally, before approving a BLA, the FDA may inspect one or more clinical sites to assure that such trials were conducted in compliance with GCP.

After the FDA evaluates a BLA and conducts any required inspections of clinical trial sites or manufacturing facilities where the investigational product and/or its drug substance will be produced, the FDA may issue an approval letter or a Complete Response Letter, or CRL. An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A CRL indicates that the review cycle of the application is complete, and the application will not be approved in its

present form. A CRL usually describes the specific deficiencies in the BLA identified by the FDA and may require additional clinical data, including additional clinical trials, or other significant and time-consuming requirements related to clinical trials, nonclinical studies or manufacturing. If a CRL is issued, the sponsor must resubmit the BLA, addressing all of the deficiencies identified in the letter, or withdraw the application. Even if such data and information are submitted, the FDA may decide that the BLA does not satisfy the criteria for approval.

If regulatory approval of a product is granted, such approval will be granted for particular indications and may entail limitations on the indicated uses for which such product may be marketed. For example, the FDA may approve the BLA with a Risk Evaluation and Mitigation Strategy, or REMS, to ensure the benefits of the product outweigh its risks. A REMS is a safety strategy implemented to manage a known or potential serious risk associated with a product and to enable patients to have continued access to such medicines by managing their safe use, and could include medication guides, physician communication plans, or elements to assure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. The FDA also may condition approval on, among other things, changes to proposed labeling or the development of adequate controls and specifications. The FDA may require one or more Phase 4 post-market studies and surveillance to further assess and monitor the product’s safety and effectiveness after commercialization and may limit further marketing of the product based on the results of these post-marketing studies.

Expedited Development and Review Programs

The FDA maintains several programs intended to facilitate and expedite development and review of new biologics designed to address unmet medical needs in the treatment of serious or life- threatening diseases or conditions. These programs include Fast Track designation, Breakthrough Therapy designation, Priority Review designation and Accelerated Approval, and the purpose of these programs is to expedite the development and review of qualifying product candidates.

A biologic is eligible for Fast Track designation if it is intended to treat a serious or life- threatening disease or condition and demonstrates the potential to address unmet medical needs for such disease or condition. Fast Track designation provides increased opportunities for sponsor meetings with the FDA during preclinical and clinical development, in addition to the potential for rolling review, meaning that the agency may review portions of the marketing application before the sponsor submits the complete application, if the sponsor provides a schedule for the submission of the sections of the BLA, the FDA agrees to accept sections of the BLA and determines that the schedule is acceptable, and the sponsor pays any required user fees upon submission of the first section of the BLA. Product candidates receiving Fast Track status may also be eligible for Priority Review, if the relevant criteria are met.

In addition, a biologic product candidate may be eligible for Breakthrough Therapy designation if it is intended to treat a serious or life-threatening disease or condition and preliminary clinical evidence indicates that the product candidate may demonstrate substantial improvement over existing therapies on one or more clinically significant endpoints, such as substantial treatment effects observed early in clinical development. Breakthrough Therapy designation provides all the features of Fast Track designation in addition to intensive guidance on an efficient development program beginning as early as Phase 1, and FDA organizational commitment to expedited development, including involvement of senior managers and experienced review staff in a cross-disciplinary review, where appropriate.

Any product candidate submitted to the FDA for approval, including a product candidate with Fast Track or Breakthrough Therapy designation, may also be eligible for additional FDA programs intended to expedite the review process, including Priority Review designation. A BLA is eligible for Priority Review if the product candidate has the potential to provide a significant improvement in safety or effectiveness in the treatment, diagnosis or prevention of a serious disease or condition. For original BLAs, priority review designation means the FDA’s goal is to take action on the marketing application within six months of the 60-day filing date (as compared to ten months under standard review).

Additionally, depending on the design of the applicable clinical trials, product candidates are eligible for accelerated approval if they can be shown to have an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or an effect on a clinical endpoint that can be measured earlier than an effect on irreversible morbidity or mortality which 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. Accelerated approval is usually contingent on a sponsor’s agreement to conduct confirmatory studies to verify and describe the product’s clinical benefit, and the FDA may require that such studies be underway before granting any accelerated approval. Products receiving accelerated approval may be subject to expedited withdrawal procedures if the sponsor fails to conduct the required confirmatory studies in a timely manner or if such studies fail to verify the predicted clinical benefit. In addition, the FDA requires as a condition for accelerated approval pre-approval of promotional materials, which could adversely impact the timing of the commercial launch of the product.

Fast Track designation, Breakthrough Therapy designation, Priority Review designation and Accelerated Approval do not change the standards for approval but may expedite the development or review process.

Post-Approval Requirements

Approved biologics that are manufactured or distributed in the United States are subject to pervasive and continuing regulation by the FDA, including, among other things, requirements relating to recordkeeping, periodic reporting, product distribution, advertising and promotion and reporting of adverse experiences with the product. There also are continuing, annual user fee requirements for products marketed pursuant to approved applications.

Any biologics manufactured or distributed pursuant to FDA approvals remain subject to continuing regulation by the FDA, including recordkeeping requirements and reporting of adverse experiences associated with the product. Manufacturers and their subcontractors are required to register their establishments with the FDA and certain state agencies and are subject to periodic unannounced inspections by the FDA and certain state agencies for compliance with ongoing regulatory requirements, including cGMP, which impose certain procedural and documentation requirements upon manufacturers and contract 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 cGMP and impose reporting requirements. Accordingly, manufacturers must continue to expend time, money and effort in the area of production and quality control to maintain compliance with cGMP and other aspects of regulatory compliance.

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

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

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fines, warning letters, untitled letters, or holds on clinical trials;

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

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

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

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

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

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injunctions or the imposition of civil or criminal penalties.

The FDA closely regulates the post-approval marketing and promotion of biologics, including standards and regulations for direct-to-consumer advertising, off-label promotion, industry-sponsored scientific and educational activities, and promotional activities involving the internet and social media. A company can make only those claims relating to safety and efficacy that are approved by the FDA. Physicians may prescribe legally available biologics for uses that are not described in the product’s labeling and that differ from those tested and approved by the FDA. The FDA does not regulate the behavior of physicians in their choice of treatments. The FDA does, however, impose stringent restrictions on manufacturers’ communications regarding off-label use. Failure to comply with these requirements can result in adverse publicity, warning letters, corrective advertising and potential civil and criminal penalties.

Biosimilars and Regulatory Exclusivity

The Affordable Care Act, signed into law in 2010, includes a subtitle called the Biologics Price Competition and Innovation Act, or BPCIA, which created an abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-licensed reference biological product. 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.

A biological product can also obtain pediatric market exclusivity in the United States. Pediatric exclusivity, if granted, adds six months to existing exclusivity periods and patent terms. This six-month exclusivity, which runs from the end of existing periods of regulatory exclusivity protection or patent terms, may be granted based on the voluntary completion of a pediatric study in accordance with an FDA-issued “Written Request” for such a study.

Orphan Drug Designation

Under the Orphan Drug Act, the FDA may grant orphan designation to a drug or biologic intended to treat a rare disease or condition, which is a disease or condition that affects fewer than 200,000 individuals in the United States, or if it affects more than 200,000 individuals in the United States, there is no reasonable expectation that the cost of developing and making the product available in the United States for the disease or condition will be recovered from sales of the product. Orphan designation must be requested before submitting a BLA. Orphan designation does not convey any advantage in or shorten the duration of the regulatory review and approval process, though companies developing orphan products are eligible for certain incentives, including tax credits for qualified clinical testing and waiver of application fees.

If a product that has orphan designation subsequently receives the first FDA approval for the disease or condition for which it has such designation, the product is entitled to a seven-year period of marketing exclusivity during which the FDA may not approve any other applications to market the same therapeutic agent for the same disease or condition, except in limited circumstances, such as a subsequent product’s showing of clinical superiority over the product with orphan exclusivity or where the original applicant cannot produce sufficient quantities of product for the applicable disease or condition. Competitors, however, may receive approval of different therapeutic agents for the disease or condition for which the orphan product has exclusivity or obtain approval for the same therapeutic agent for a different disease or condition than that for which the orphan product has exclusivity. Further, if a designated orphan product receives marketing approval for a disease or condition broader than the rare disease or condition for which it received orphan designation, it may not be entitled to orphan exclusivity.

Government Regulation Outside of the United States

To market any product outside of the United States, we would need to comply with numerous and varying regulatory requirements of other countries regarding safety and efficacy and governing, among other things, clinical trials, marketing authorization, or MA, manufacturing, commercial sales and distribution of our products. Because biologically sourced raw materials are subject to unique contamination risks, their use may be restricted in some countries. Whether or not we obtain FDA approval of a product, we must obtain the requisite approvals from regulatory authorities in foreign countries prior to the commencement of clinical studies or marketing of the product in those countries. The requirements and process governing the conduct of clinical studies, product licensing, pricing and reimbursement vary from country to country. Failure to comply with applicable foreign regulatory requirements, may be subject to, among other things, fines, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

Non-clinical studies and clinical trials

Similar to the United States, the various phases of non-clinical and clinical research in the EU are subject to significant regulatory controls.

Non-clinical studies are performed to demonstrate the health or environmental safety of new biological substances. Non-clinical (pharmaco-toxicological) studies must be conducted in compliance with the principles of good laboratory practice, or GLP, as set forth in EU Directive 2004/10/EC (unless otherwise justified for certain particular medicinal products, e.g., radio-pharmaceutical precursors for radio-labeling purposes). In particular, non-clinical studies, both in vitro and in vivo, must be planned, performed, monitored, recorded, reported and archived in accordance with the GLP principles, which define a set of rules and criteria for a quality system for the organizational process and the conditions for non-clinical studies. These GLP standards reflect the Organization for Economic Co-operation and Development requirements.

Clinical trials of medicinal products in the EU must be conducted in accordance with EU and national regulations and the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use, or ICH, guidelines on Good Clinical Practices, or GCP, as well as the applicable regulatory requirements and the ethical principles that have their origin in the Declaration of Helsinki. Additional GCP guidelines from the European Commission, focusing in particular on traceability, apply to clinical trials of advanced therapy medicinal products, or ATMPs. If the sponsor of the clinical trial is not established within the EU, it must appoint an EU entity to act as its legal representative. The sponsor must take out a clinical trial insurance policy, and in most EU member states, the sponsor is liable to provide ‘no fault’ compensation to any study subject injured in the clinical trial.

The EU Clinical Trials Regulation, or CTR, which was adopted in April 2014 and repeals the EU Clinical Trials Directive, became applicable on January 31, 2022. Unlike directives, the CTR is directly applicable in all EU member states without the need for member states to further implement it into national law. The CTR notably harmonizes the assessment and supervision processes for clinical trials throughout the EU via a Clinical Trials Information System, which contains a centralized EU portal and database.

The CTR utilizes a centralized process and requires the submission of a single clinical trial application, or CTA, for multi-center trials. The CTR allows sponsors to make a single submission to both the competent authority and an ethics committee in each member state, leading to a single decision per member state. The CTA must include, among other things, a copy of the trial protocol and an investigational medicinal product dossier containing information about the manufacture and quality of the medicinal product under investigation. The assessment procedure of the CTA has been harmonized as well, including a joint assessment by all member states concerned, and a separate assessment by each member state with respect to specific requirements related to its own territory, including ethics rules. Each member state’s decision is communicated to the sponsor via the centralized EU portal. Once the CTA is approved, clinical study development may proceed.

Medicines used in clinical trials must be manufactured in accordance with Good Manufacturing Practice, or GMP. Other national and EU-wide regulatory requirements may also apply.

During the development of a medicinal product, the EMA and national regulators provide the opportunity for dialogue and guidance on the development program. At the EMA level, this is usually done in the form of scientific advice, which is given by the Scientific Advice Working Party of the Committee for Medicinal Products for Human Use, or CHMP. A fee is incurred with each scientific advice procedure. Advice from the EMA is typically provided based on questions concerning, for example, quality (chemistry, manufacturing and controls testing), nonclinical testing and clinical trials, and pharmacovigilance plans and risk-management programs. Advice is not legally binding with regard to any future marketing authorization application of the product concerned.

Marketing Authorizations

In the EU, medicinal products can only be placed on the market after obtaining a MA. To obtain regulatory approval of an investigational biological product in the EU, we must submit a MA application, or MAA. The process for doing this depends, among other things, on the nature of the medicinal product.

Centralized procedure—Under the centralized procedure, following the opining of the EMA’s CHMP the European Commission issues a single MA valid throughout the EU. The centralized procedure is compulsory for certain types of products, such as (i) medicinal products derived from biotechnology processes, such as genetic engineering, (ii) designated orphan medicinal products, (iii) advanced therapy medicinal products, or ATMPs, such as gene therapy, somatic cell therapy and tissue engineered products, and (iv) medicinal products that contain a new active substance indicated for the treatment of certain diseases, such as HIV/AIDS, cancer, neurodegenerative diseases, diabetes, autoimmune diseases and other immune dysfunctions, and viral diseases. The centralized procedure is optional for any products containing a new active substance not yet authorized in the EU, or for products that constitute a significant therapeutic, scientific or technical innovation or for which the granting of a MA would be in the interest of public health in the EU.

Under the centralized procedure the maximum timeframe for the evaluation of an MAA by the EMA's CHMP is 210 days, excluding clock stops, when additional written or oral information is to be provided by the applicant in response to questions asked by the CHMP. At the end of the review period, the CHMP provides an opinion to the European Commission. If this opinion is favorable, the Commission may then adopt a decision to grant an MA. In exceptional cases, the CHMP might perform an accelerated review of a MAA in no more than 150 days (excluding clock stops), when a medicinal product targets an unmet medical need and is expected to be of a major public health interest, particularly from the point of view of therapeutic innovation. The timeframe for the evaluation of an MAA under the accelerated assessment procedure is 150 days, excluding clock stops.

Innovative products that target an unmet medical need and are expected to be of major public health interest may be eligible for a number of expedited development and review programs, such as the PRIME scheme, which provides incentives similar to the breakthrough therapy designation in the U.S. In March 2016, the EMA launched an initiative, the Priority Medicines, or PRIME, scheme, a voluntary scheme aimed at enhancing the EMA’s support for the development of medicines that target unmet medical needs. It is based on increased interaction and early dialogue with companies developing promising medicines, to optimize their product development plans and speed up their evaluation to help them reach patients earlier. Product developers that benefit from PRIME designation can expect to be eligible for accelerated assessment but this is not guaranteed. Many benefits accrue to sponsors of product candidates with PRIME designation, including but not limited to, early and proactive regulatory dialogue with the EMA, frequent discussions on clinical trial designs and other development program elements, and accelerated MAA assessment once a dossier has been submitted. Importantly, a dedicated contact and rapporteur from the CHMP is appointed early in the PRIME scheme facilitating increased understanding of the product at EMA’s committee level. An initial meeting initiates these relationships and includes a team of multidisciplinary experts at the EMA to provide guidance on the overall development and regulatory strategies.

National authorization procedures—There are also two other possible routes to authorize medicinal products in several member states, which are available for products that fall outside the scope of the centralized procedure:

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Decentralized procedure. Using the decentralized procedure, an applicant may apply for simultaneous authorizations in more than one EU member states of medicinal products that have not yet been authorized in any EU member states and that do not fall within the mandatory scope of the centralized procedure. Under the decentralized procedure an identical dossier is submitted to the national competent authority of each of the member states in which the MA is sought, one of which is selected by the applicant as the reference member state. National MAs are issued by competent authorities of the EU member states for their respective territory.

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Mutual recognition procedure. In the mutual recognition procedure, a medicine is first authorized in one EU member state, in accordance with the national procedures of that member state. Following this, further MAs can be sought from other EU member states in a procedure whereby the countries concerned recognize the validity of the original national MA.

MAs have an initial duration of five years. After these five years, the authorization may be renewed on the basis of a reevaluation of the risk-benefit balance. Once renewed, the MA is valid for an unlimited period unless the European Commission or the national competent authority decides, on justified grounds relating to pharmacovigilance, to proceed with one additional five-year renewal.

Data and Marketing Exclusivity

In the EU, upon receiving a MA, reference medicinal products generally receive eight years of data exclusivity and an additional two years of market exclusivity. If granted, data exclusivity period prevents generic or biosimilar applicants from relying on the preclinical and clinical trial data contained in the dossier of the reference product when applying for a generic or biosimilar MA in the EU during a period of eight years from the date on which the reference product was first authorized in the EU. During the additional two-year period of the market exclusivity period a generic or biosimilar MA can be submitted, and the innovator’s data may be referenced but no generic or biosimilar can be marketed in the EU until ten years have elapsed from the initial authorization of the reference product in the EU. The overall ten-year market exclusivity period can be extended to a maximum of eleven years if, during the first eight years of those ten years, the MA holder obtains an authorization for one or more new therapeutic indications which, during the scientific evaluation prior to their authorization, are held to bring a significant clinical benefit in comparison with existing

therapies. However, there is no guarantee that a product will be considered by the EU’s regulatory authorities to be a new chemical or biological entity, and products may not qualify for data exclusivity.

There is a special regime for biosimilars, or biological medicinal products that are similar to a reference medicinal product but that do not meet the definition of a generic medicinal product, for example, because of differences in raw materials or manufacturing processes. For such products, the results of appropriate preclinical or clinical trials must be provided, and guidelines from the EMA detail the type of quantity of supplementary data to be provided for different types of biological product. There are no such guidelines for complex biological products, such as gene or cell therapy medicinal products, and so it is unlikely that biosimilars of those products will currently be approved in the EU. However, guidance from the EMA states that they will be considered in the future in light of the scientific knowledge and regulatory experience gained at the time.

Orphan Medicinal Products

The criteria for designating an “orphan medicinal product” in the EU are similar in principle to those in the United States. A medicinal product may be designated as orphan if (1) it is intended for the diagnosis, prevention or treatment of a life-threatening or chronically debilitating condition; (2) either (a) such condition affects no more than five in 10,000 persons in the EU when the application is made, or (b) the product, without the benefits derived from orphan status, would not generate sufficient return in the EU to justify investment; and (3) there exists no satisfactory method of diagnosis, prevention or treatment of such condition authorized for marketing in the EU, or if such a method exists, the product will be of significant benefit to those affected by the condition. The application for orphan drug designation must be submitted before the MAA. Orphan medicinal products are eligible for financial incentives such as reduction of fees or fee waivers, protocol assistance, access to the centralized procedure, and are, upon grant of a MA, entitled to ten years of market exclusivity for the approved therapeutic indication. During this ten-year orphan market exclusivity period, the competent authorities cannot accept another MAA, or grant a MA, or accept an application to extend a MA for a similar product for the same indication. The period of market exclusivity is extended by two years for orphan medicinal products that have also complied with an agreed pediatric investigation plan, or PIP. No extension to any supplementary protection certificate can be granted on the basis of pediatric studies for orphan indications. Orphan drug designation does not convey any advantage in, or shorten the duration of, the regulatory review and approval process.

The ten-year market exclusivity may be reduced to six years if, at the end of the fifth year, it is established that the product no longer meets the criteria for orphan designation, for example, if the product is sufficiently profitable not to justify maintenance of market exclusivity or where the prevalence of the condition has increased above the threshold. Additionally, a MA may be granted to a similar product for the same indication at any time if (i) the second applicant can establish that its product, although similar, is safer, more effective or otherwise clinically superior; (ii) the applicant consents to a second orphan medicinal product application; or (iii) the applicant cannot supply enough orphan medicinal product.

Pediatric Development

In the EU, MAAs for new medicinal products have to include the results of trials conducted in the pediatric population, in compliance with a pediatric investigation plan, or PIP, agreed with the EMA’s Pediatric Committee, or PDCO. The PIP sets out the timing and measures proposed to generate data to support a pediatric indication of the drug for which an MA is being sought. The PDCO can grant a deferral of the obligation to implement some or all of the measures of the PIP until there are sufficient data to demonstrate the efficacy and safety of the product in adults. Further, the obligation to provide pediatric clinical trial data can be waived by the PDCO when these data are not needed or appropriate because the product is likely to be ineffective or unsafe in children, the disease or condition for which the product is intended occurs only in adult populations, or when the product does not represent a significant therapeutic benefit over existing treatments for pediatric patients. Once the MA is obtained in all member states and study results are included in the product information, even when negative, the product is eligible for a six-months supplementary protection certificate extension (if any is in effect at the time of approval) or, in the case of orphan pharmaceutical products, a two year extension of the orphan market exclusivity is granted.

Post-Approval Requirements

Similar to the United States, both MA holders and manufacturers of medicinal products are subject to comprehensive regulatory oversight by the EMA, the European Commission and/or the competent regulatory authorities of the member states. The holder of a MA must establish and maintain a pharmacovigilance system and appoint an individual qualified person for pharmacovigilance, or QPPV, who is responsible for the establishment and maintenance of that system, and oversees the safety profiles of medicinal products and any emerging safety concerns. Key obligations include expedited reporting of suspected serious adverse reactions and submission of periodic safety update reports, or PSURs.

All new MAAs must include a risk management plan, or RMP, describing the risk management system that the company will put in place and documenting measures to prevent or minimize the risks associated with the product. The regulatory authorities may also impose specific obligations as a condition of the MA. Such risk-minimization measures or post-authorization obligations may include additional safety monitoring, more frequent submission of PSURs, or the conduct of additional clinical trials or post-authorization safety studies.

The advertising and promotion of medicinal products is also subject to laws concerning promotion of medicinal products, interactions with physicians, misleading and comparative advertising and unfair commercial practices. All advertising and promotional activities for the product must be consistent with the approved summary of product characteristics, and therefore all off-label promotion is prohibited. Direct-to-consumer advertising of prescription medicines is also prohibited in the EU. Although general requirements for advertising and promotion of medicinal products are established under EU directives, the details are governed by regulations in each member state and can differ from one country to another.

Failure to comply with EU and member state laws that apply to the conduct of clinical trials, manufacturing approval, MA of medicinal products and marketing of such products, both before and after grant of the MA, manufacturing of pharmaceutical products, statutory health insurance, bribery and anti-corruption or with other applicable regulatory requirements may result in administrative, civil or criminal penalties. These penalties could include delays or refusal to authorize the conduct of clinical trials, or to grant MA, product withdrawals and recalls, product seizures, suspension, withdrawal or variation of the MA, total or partial suspension of production, distribution, manufacturing or clinical trials, operating restrictions, injunctions, suspension of licenses, fines and criminal penalties.

The aforementioned EU rules are generally applicable in the European Economic Area, or EEA (comprised of the 27 EU member states plus Iceland, Liechtenstein and Norway).

Brexit and the Regulatory Framework in the United Kingdom

Since the end of the Brexit transition period on January 1, 2021, and the implementation of the Windsor Framework on January 1, 2025, the United Kingdom, or UK, is not generally subject to EU laws in respect of medicinal products. The EU laws that have been transposed into UK law through secondary legislation remain applicable in the UK. However, new legislation such as the CTR is not applicable in the UK. The UK government has passed the Medicines and Medical Devices Act 2021, which introduces delegated powers in favor of the Secretary of State or an ‘appropriate authority’ to amend or supplement existing regulations in the area of medicinal products and medical devices. This allows new rules to be introduced in the future by way of secondary legislation, which aims to allow flexibility in addressing regulatory gaps and future changes in the fields of human medicines, clinical trials and medical devices.

As of January 1, 2021, the Medicines and Healthcare products Regulatory Agency, or MHRA, is the UK’s standalone medicines and medical devices regulator. As a result of the Ireland/Northern Ireland Protocol, different rules applied in Northern Ireland than in England, Wales, and Scotland, together, Great Britain (“GB”); which continued to follow the EU regulatory regime. However, on January 1, 2025, an arrangement called the “Windsor Framework” came into effect and reintegrated Northern Ireland under the regulatory authority of the MHRA with respect to medicinal products. The Windsor Framework removes EU licensing processes, and EU labeling and serialization requirements in relation to Northern Ireland, and introduces a UK-wide licensing process for medicinal products.

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