Kiniksa Pharmaceuticals International, plc_December 31, 2025

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

For the fiscal year ended December 31, 2025

For the transition period from to

Commission File Number: 001-38492

Kiniksa Pharmaceuticals International, plc

(Exact name of registrant as specified in its charter)

Kiniksa Pharmaceuticals International, plc

105 Piccadilly, Second Floor

London, W1J 7NJ

England, United Kingdom

(781) 431-9100

(Address, zip code and telephone number, including area code of principal executive offices)

Kiniksa Pharmaceuticals Corp.

100 Hayden Avenue

Lexington, MA, 02421

(781) 431-9100

(Address, zip code and telephone number, including area code of agent for service)

N/A

(Former name, former address and former fiscal year, if changed since last report)

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

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

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 during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes☒ No ☐

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

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

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

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

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

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

As of the last business day of the Registrant’s most recently completed second fiscal quarter, June 30, 2025, the aggregate market value of the voting and non-voting common equity held by non-affiliates of the Registrant, based on the closing price of the ordinary shares on The Nasdaq Global Select Market was approximately $1,114.0 million.

As of February 20, 2026, there were 76,535,377 ordinary shares outstanding in aggregate, comprised of:

45,900,637 Class A ordinary shares, nominal value $0.000273235 per share

1,795,158 Class B ordinary shares, nominal value $0.000273235 per share

12,781,964 Class A1 ordinary shares, nominal value $0.000273235 per share

16,057,618 Class B1 ordinary shares, nominal value $0.000273235 per share

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant’s definitive proxy statement for its 2026 Annual Meeting of Shareholders, which the registrant intends to file with the Securities and Exchange Commission pursuant to Regulation 14A within 120 days after the end of the registrant’s fiscal year ended December 31, 2025, are incorporated by reference into Part III of this Annual Report on Form 10-K.

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Kiniksa Pharmaceuticals International, plc

FORM 10-K

FOR THE YEAR ENDED DECEMBER 31, 2025

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Page

PART I

Item 1. Business 7

Item 1A. Risk Factors 43

Item 1B. Unresolved Staff Comments 93

Item 1C. Cybersecurity 93

Item 2. Properties 94

Item 3. Legal Proceedings 94

Item 4. Mine Safety Disclosures 94

PART II

Item 6. Reserved. 96

Item 7A. Quantitative and Qualitative Disclosures About Market Risk 109

Item 8. Financial Statements and Supplementary Data 110

Item 9A. Controls and Procedures 110

Item 9B. Other Information 111

PART III

Item 10. Directors, Executive Officers and Corporate Governance 112

Item 11. Executive Compensation 112

Item 14. Principal Accounting Fees and Services 112

PART IV

Item 15. Exhibits and Financial Statement Schedules 113

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report on Form 10-K (this “Annual Report”) contains forward-looking statements. All statements other than statements of historical facts contained in this Annual Report should be considered forward-looking statements, including statements regarding: our beliefs that KPL-387 will expand the recurrent pericarditis market and provide additional treatment options for patients; our beliefs about dosing and administration for our product candidates, including that KPL-387 has the potential for monthly subcutaneous self-administration in a liquid formulation and that KPL-1161 has the potential for quarterly subcutaneous dosing; our expectation to have data from the Phase 2 portion of our trial of KPL-387 in recurrent pericarditis in the second half of 2026 and that we plan to use the totality of the data to determine further development strategy; our plan to initiate a Phase 1 first-in-human clinical trial of KPL-1161 by the end of 2026; our plan to explore strategic alternatives for abiprubart; our belief that advancing KPL-387 through the clinic and into the market will further our mission of meeting patients’ needs; the results we expect to receive from our commercialization efforts; the incidence and prevalence for our target patient populations; our belief that each of our product candidates holds the potential to offer differentiated therapy to patients; planned indications for our products and product candidates; our expectations regarding the value we expect to receive/pay under our current license and collaboration agreements; the plans and strategy of our competitors; our expectations around the intellectual property protection we hope to receive for our products and product candidates; the intellectual property strategy we expect to employ to protect our portfolio; our plans to apply for patent term extensions; our predictions regarding future regulations and legislation; our planned commercial strategy; our plans to rely on third-parties, such as specialty pharmacies, contract research organizations (“CROs”) and contract development and manufacturing organizations (“CDMOs”); our relationships with payers; future supply for our products and product candidates; the timing and likelihood of success of our ongoing technology transfer of ARCALYST drug substance manufacturing; the expected impact of the United States’ tariffs on our operations, including that we do not expect that tariffs in their current state to have a material impact on our overall business, financial condition or results of operations; plans to conduct operations through one or more of our foreign subsidiaries; the ways in which we expect to incur expenses, including through any future clinical or commercialization efforts; our expectation that our cash balance and our expected cash inflows form operations will allow us to meet our current operating plan and that our existing cash, cash equivalents and short-term investments will enable us to fund our operating expenses and capital expenditure requirements for at least the next 12 months; statements regarding our expected near-term expenditures and revenue; and other similar 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,” “goal,” “design,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions, although not all forward-looking statements contain these identifying words. The forward-looking statements in this Annual Report 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 Annual Report and are subject to a number of risks, uncertainties and assumptions described under the sections in this Annual Report entitled “Summary Risk Factors”, “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and elsewhere in this Annual Report.

Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond our control, you should not place undue reliance on our forward-looking statements. Except as required by applicable law, we do not assume and specifically disclaim any obligation to update any forward-looking statements, whether as a result of any new information, future events, changed circumstances or otherwise.

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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. You should carefully consider these risks and uncertainties when investing in our Class A ordinary shares. The principal risks and uncertainties affecting our business include the following:

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Industry and other data

Unless otherwise indicated, certain industry data and market data included in this Annual Report were obtained from independent third party surveys, market research, publicly available information, reports of governmental agencies and industry publications and surveys. All of the market data used in this Annual Report involve a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. We believe that the information from these industry publications and surveys included in this Annual Report is reliable.

ARCALYST® is a registered trademark of Regeneron. Solely for convenience, trademarks, service marks and trade names referred to in this Annual Report may be listed without identifying symbols.

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PART I

ITEM 1.BUSINESS.

Overview

We are a biopharmaceutical company developing and commercializing novel therapies for diseases with unmet need, with a focus on cardiovascular indications. Our portfolio of assets is based on strong biologic rationale or validated mechanisms and offers the potential for differentiation.

ARCALYST is an interleukin-1α (“IL-1α”) and interleukin-1β (“IL-1β”) cytokine trap. In 2017, we licensed ARCALYST from Regeneron, which discovered and initially developed the drug. Our exclusive license to ARCALYST from Regeneron includes worldwide rights, excluding the Middle East and North Africa, for all applications other than those in oncology and local administration to the eye or ear.

We received FDA approval of ARCALYST for the treatment of recurrent pericarditis and reduction in risk of recurrence in adults and children 12 years and older in March 2021. Recurrent pericarditis is a painful inflammatory cardiovascular disease with an estimated United States prevalent population of approximately 40,000 patients seeking and receiving medical treatment. ARCALYST is also approved in the United States for the treatment of Cryopyrin-Associated Periodic Syndromes (“CAPS”), including Familial Cold Autoinflammatory Syndrome (“FCAS”) and Muckle-Wells Syndrome in adults and children 12 years and older, and the maintenance of remission in Deficiency of Interleukin-1 Receptor Antagonist (“DIRA”) in adults and children weighing 10 kg or more.

ARCALYST is commercially available across the United States through a select network of specialty pharmacies. We are responsible for sales and distribution of ARCALYST in all approved indications in the United States and evenly split profits on sales as well as third party proceeds with Regeneron. In 2022, we granted Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd. (“Huadong”) exclusive rights to develop and commercialize ARCALYST in the Huadong Territory (as defined below). In 2023, Regeneron initiated a technology transfer of the manufacturing process for ARCALYST drug substance, and we are working to qualify Samsung as our replacement CDMO. In December 2024, we initiated a collaborative study agreement with The Mayo Clinic (together with Johns Hopkins University) to investigate the effects of ARCALYST in the treatment of cardiac sarcoidosis.

KPL-387 is an investigational, fully human immunoglobulin G2 monoclonal antibody that binds human interleukin-1 receptor 1 (“IL-1R1”), inhibiting IL-1α- and IL-1β-mediated signaling. KPL-387 is an independently developed asset that we believe may expand the recurrent pericarditis market and provide an additional treatment option for patients, with the potential to add the convenience of monthly subcutaneous self-administration with a liquid formulation.

In July 2025, we announced that the Phase 2 dose-focusing portion of the Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis had begun recruiting. We expect data from the Phase 2 portion of the trial in the second half of 2026 and plan to use the totality of the data to determine further development strategy. In September 2025, we announced plans to conduct a supplemental Phase 2 transition to KPL-387 monotherapy dosing and administration study to evaluate the efficacy and safety of dosing regimens used to transition patients from standard therapies to KPL-387 monotherapy.

In October 2025, the FDA granted Orphan Drug Designation to KPL-387 for the treatment of pericarditis.

KPL-1161 is an independently developed, pre-clinical, Fc-modified immunoglobulin G2 monoclonal antibody that binds IL-1R1, inhibiting IL-1α- and IL-1β-mediated signaling. KPL-1161 is a modified version of KPL-387 designed to have an increased drug half-life that we believe could support quarterly subcutaneous dosing. We are currently conducting preclinical activities with respect to this asset, with an expectation to initiate a Phase 1 first-in-human clinical trial by the end of 2026.

Abiprubart is an investigational monoclonal antibody inhibitor of CD40-CD154 costimulatory interaction, which we believe to be an attractive approach to address multiple autoimmune disease pathologies. We hold an exclusive worldwide license to abiprubart from Beth Israel Deaconess Medical Center, Inc. (“BIDMC”).

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We previously announced a Phase 2b clinical trial of abiprubart in Sjögren’s Disease. In February 2025, we announced our plans to discontinue development of abiprubart in the indication and to explore strategic alternatives for the asset.

The following table summarizes our current products, product candidates and out-licensing arrangements:

Using a data-centric approach, our team considers a wide variety of metrics to drive informed capital allocation strategies and generate value from this pipeline, including by analyzing potential additional indications for our products and product candidates, being opportunistic in our business development activities to in-license or acquire programs, considering appropriate opportunities to partner or out-license our programs and conducting internal research to discover and develop molecules to expand our portfolio.

Our Strategy

The core of our strategy is the identification, development and commercialization of therapeutic medicines for patients suffering from debilitating cardiovascular diseases with significant unmet medical need. We put patients first and live by our motto: Every Second CountsTM.

Critical components of our business strategy include the following:

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Our Products

ARCALYST

Overview

ARCALYST is an IL-1α and IL-1β cytokine trap. ARCALYST is currently approved in the United States for the treatment of recurrent pericarditis and reduction in risk of recurrence in adults and children 12 years and older, the treatment of CAPS, including FCAS and Muckle-Wells Syndrome in adults and children 12 years and older, and the maintenance of remission in DIRA in adults and children weighing 10 kg or more. ARCALYST was sold by Regeneron in the United States for the treatment of CAPS from 2008 and the maintenance of remission in DIRA from 2020 until we assumed responsibility for sales in such indications in March 2021.

Recurrent pericarditis is the primary indication for which we are commercializing ARCALYST. It is a severe, debilitating and chronic autoinflammatory cardiovascular disease with an estimated United States prevalent population of approximately 40,000 patients seeking and receiving medical treatment. We received Breakthrough Therapy designation from the FDA for ARCALYST for the treatment of recurrent pericarditis in 2019, Orphan Drug designation from the FDA for ARCALYST for the treatment of pericarditis, which includes the treatment of recurrent pericarditis, in 2020 and FDA approval of ARCALYST for the treatment of recurrent pericarditis and reduction in risk of recurrence in adults and children 12 years and older in March 2021.

In 2022, we granted Huadong exclusive rights to develop and commercialize ARCALYST in the Huadong Territory. In December 2024, we initiated a collaborative study agreement with The Mayo Clinic (together with Johns Hopkins University) to investigate the effects of ARCALYST in the treatment of cardiac sarcoidosis.

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Mechanism of Action

ARCALYST is an inhibitor of IL-1α and IL-1β cytokines. Cytokines are small proteins that play important roles in intercellular signaling, and IL-1α and IL-1β have been demonstrated to play a key role in inflammatory diseases. IL-1α and IL-1β provoke potent, proinflammatory events by engaging the IL-1α and IL-1β receptor. Following tissue insult, the release of IL-1α acts as the primary initiating signal to coordinate the mobilization of immune cells to the damaged area, while IL-1β is secreted mostly by macrophages and is a prototypical cytokine of the canonical NLRP-3 inflammasome. IL-1α and IL-1β signaling results in a dramatic increase in the production of cytokines that orchestrate the proliferation and recruitment of phagocytes to the site of damage, resulting in inflammation. Moreover, IL-1α and IL-1β signaling also affects other immune system cells, such as T-cells and B-cells.

IL-1β’s role in the inflammation process has been extensively studied, while, in comparison, much is still unknown about the independent function of IL-1α in disease pathology. Despite driving similar immunological outcomes, IL-1α and IL-1β differ substantially in their expression and regulation, and non-redundant roles for IL-1α or IL-1β have been demonstrated in multiple inflammatory diseases. There are disease states in which IL-1β inhibition alone does not appear to be sufficient for disease remission in the absence of IL-1α inhibition. Published studies suggest certain autoinflammatory diseases may, in fact, be pathologically driven primarily by IL-1α.

We believe that inhibiting both IL-1α and IL-1β signaling is important for treating recurrent pericarditis. In a published case study, a participant with a refractory form of recurrent pericarditis, who was well controlled on anakinra, was switched from anakinra to canakinumab, which inhibits only IL-1β, for tolerability reasons. The participant’s disease returned despite further dose escalation of canakinumab. When the participant was switched back to anakinra, which inhibits ILα and ILβ, the disease promptly went back into remission. These data, together with clinical data from our pivotal Phase 3 clinical trial of ARCALYST, indicate that IL-1α and IL-1β play unique roles in recurrent pericarditis and other autoinflammatory diseases in which the pathology may be driven primarily by IL-1α. Other literature published after the June 2022 completion of the phase 3 clinical trial of ARCALYST corroborated these findings in larger populations of participants.

Beyond recurrent pericarditis, we believe there is potential for ARCALYST to address additional indications driven by IL-1α or IL-1β. We are currently engaged in a collaborative study agreement to explore ARCALYST as a treatment for cardiac sarcoidosis and are exploring strategic opportunities for further development. In particular, we believe ARCALYST may be advantageous in acute indications that may benefit from a weekly subcutaneous therapy with a proven method of action.

Background and Market Opportunity for Recurrent Pericarditis

Pericarditis is the most common disorder involving the pericardium, the two-layered sac that surrounds the heart. Pericarditis is an inflammation of this sac and is typically characterized by significant chest pain, shortness of breath, coughing and fatigue and is often misconstrued by patients as a heart attack. In addition, typical signs of pericarditis include pericardial friction rub, electrocardiogram changes or pericardial effusion, which is a buildup of fluid around the heart. Pericarditis is described as recurrent if, following an initial occurrence of pericarditis, it recurs after a symptom-free period of about four to six weeks. Pericarditis is considered chronic if symptoms of any one episode last longer than three months, typically causing significant pain and frustration. If pericarditis is left untreated, patients can develop thickening and scarring of the pericardium, potentially requiring invasive surgical stripping. Pericardial effusion, if large enough, can compress the heart extrinsically, requiring emergent drainage.

In March 2021, we received FDA approval to market ARCALYST for the treatment of recurrent pericarditis and reduction in risk of recurrence in adults and children 12 years of age and older. Claims analysis, cross validated with published estimates, support a prevalent population of patients with recurrent pericarditis seeking and receiving medical treatment to be approximately 40,000 patients in the United States per year. Our commercialization efforts are focused initially on the approximately 14,000 patients in the United States who suffer from persistent underlying disease, multiple recurrences and an inadequate response to conventional therapy. Outside of our core target patient population, there are approximately 26,000 additional patients who are experiencing their first recurrence of the disease. Further, data shows that one-third of patients with multiple recurrences continue to suffer from the disease at 5 years from their

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first recurrence of the disease and one-quarter continue at 8 years. We have seen that, as we expand awareness about the disease and our therapy, healthcare professionals look to prescribe ARCALYST earlier in the disease’s natural history, including prescriptions to biologic-appropriate patients in their first recurrence. We expect that continuing to execute on this strategy will enable us to target this additional patient population more fully.

Current Treatment Landscape for Recurrent Pericarditis

ARCALYST, a weekly, subcutaneously injected, recombinant fusion protein that blocks IL-1α and IL-1β signaling, is the first and only FDA-approved therapy for recurrent pericarditis. A patient’s initial acute episode of pericarditis is typically treated with NSAIDs or colchicine. Prior to ARCALYST’s approval, episodes of recurrent pericarditis would usually have been treated in a similar manner or by adding long-term systemic corticosteroids. Both colchicine and corticosteroids often have adverse effects when used at high doses or for extended periods of time. Colchicine’s adverse effects include gastrointestinal distress and neutropenia. Adverse events that may be caused by corticosteroids include glaucoma, fluid retention, hypertension, mood changes, memory changes, other psychological effects, weight gain and diabetes. Since our commercial launch of ARCALYST, we have seen a shift in the treatment paradigm, with an increasing number of healthcare professionals prescribing ARCALYST’s targeted immunomodulation before using corticosteroids. Emblematic of this paradigm shift was the recently published American College of Cardiology Concise Clinical Guidance, which prioritized IL-1 inhibition therapy as a second-line treatment after failure of first-line therapy in the auto-inflammatory phenotype. We believe this reflects a growing acceptance of ARCALYST as an effective, steroid-sparing therapy for patients with unmet need in this debilitating disease.

Clinical Trials and Collaborative Study Agreements

We have initiated a collaborative study agreement with The Mayo Clinic (together with Johns Hopkins University) to investigate the effects of ARCALYST in the treatment of cardiac sarcoidosis. The study is a Phase 2 PROBE-design study to evaluate the efficacy and safety of ARCALYST over 24 weeks of treatment in patients with cardiac sarcoidosis. The primary efficacy endpoint is change from baseline in number of segments with FDG uptake on cardiac FDG-PET scan at week 24. The following graphic shows the trial design and primary and secondary efficacy endpoints in more detail:

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Commercial Strategy for ARCALYST

Since our commercial launch of ARCALYST for the treatment of recurrent pericarditis in 2021, we have developed a focused and targeted commercial strategy. Our specialty salesforce, which prioritizes calls on high-volume accounts and prescribers, is complemented by our medical affairs, payor and patient services teams who work to secure broad patient access to ARCALYST, educate communities, collaborate with patient advocacy groups and drive scientific understanding of recurrent pericarditis. Further, we have established an efficient marketing effort intended to educate and raise awareness of recurrent pericarditis among prescribers and patients and promote ARCALYST as the first and only FDA-approved treatment for this debilitating disease.

Using these resources, our commercialization efforts are focused on five strategic imperatives to increase the uptake and adoption of ARCALYST as well as ensuring a positive patient experience.

First, we are focused on increasing awareness of the disease and its impact on patients’ lives. We believe disease awareness is essential to enable physicians to diagnose recurrent pericarditis earlier in its disease course and to treat the underlying disease, rather than to manage individual flares episodically. Our sales and marketing teams work to educate patients and prescribers about the signs, symptoms, duration and treatment of the disease, and the impact that recurrent pericarditis has on patients’ lives. We have further partnered with each of NHL Hall-of-Famer Henrik Lundqvist and GRAMMY® Award-Winning Singer-Songwriter Carly Pearce as part of our Life DisRPtedTM Campaign to drive awareness of recurrent pericarditis.

Second, we are working to improve the patient journey for those suffering from recurrent pericarditis. For example, in 2024 we announced our sponsorship of the American Heart Association’s Addressing Recurrent Pericarditis initiative. This initiative is designed to facilitate knowledge-sharing across a network of healthcare providers around the United States and streamline patient access to expert care. The program currently collaborates with a number of pericardial disease centers, offering patients dedicated, expert care that is designed to shorten patients’ journeys to diagnoses.

Third, we are working to establish ARCALYST as a therapy to be used in recurrent pericarditis patients as soon as appropriate after diagnosis and for the full duration of the disease. Evidence shows that, in part due to our educational efforts, prescribers are opting to prescribe ARCALYST earlier in the disease course, with real world evidence demonstrating that ARCALYST has increasingly become a second-line treatment for recurrent pericarditis, including after patients’ first recurrence. In addition, patients and prescribers are opting to treat recurrent pericarditis for its full duration of disease. This supports our overall mission to help patients lead meaningful lives with minimal flares for the full breadth of the disease’s natural history.

Fourth, we aim to secure broad patient access at a price that reflects ARCALYST’s value as the first and only FDA-approved therapy for recurrent pericarditis. Helping to ensure affordability and access to treatment by patients is one of our core principles. To this end, we offer a suite of programs to support affordability for eligible patients who are prescribed ARCALYST.

Fifth, we have built a robust patient support program to optimize patient experiences with ARCALYST and Kiniksa. Our Kiniksa OneConnectTM program offers personalized treatment support for eligible patients prescribed ARCALYST. This program is designed to ensure patients have a positive experience from initiating ARCALYST therapy through the end of their treatment.

Our Product Candidates

KPL-387

Overview

KPL-387 is an investigational, fully human immunoglobulin G2 monoclonal antibody that binds IL1-R1, inhibiting the signaling of both IL-1α and IL-1β cytokines. KPL-387 is an independently developed asset that we believe

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may expand the recurrent pericarditis market and provide an additional treatment option for patients, with the potential to add the convenience of monthly subcutaneous self-administration with a liquid formulation. In October 2025, the FDA granted Orphan Drug Designation to KPL-387 for the treatment of pericarditis.

We are currently conducting the Phase 2 dose-focusing portion of the Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis, with data expected in the second half of 2026. We plan to use the totality of the data to determine further development strategy. In addition, we are conducting a supplemental Phase 2 transition to KPL-387 monotherapy dosing and administration study to evaluate the efficacy and safety of dosing regimens used to transition patients from standard therapies to KPL-387 monotherapy.

Mechanism of Action

KPL-387 binds IL-1R1, inhibiting the signaling of IL-1α and IL-1β cytokines. We believe there are diseases of the cardiovascular system where tissue inflammation may be driven by IL-1α and/or IL-1β, and we intend to consider development of KPL-387 in these indications and in others where we believe IL-1α and/or IL-1β plays a key role in disease pathophysiology.

Our Solution

We are developing KPL-387 for the treatment of recurrent pericarditis, where we believe IL-1 inhibition therapies offer significant advantages over other treatment modalities. Further, we believe an IL-1 inhibitor with the potential to combine convenient monthly dosing and a patient friendly, convenient autoinjector could meet patient needs and provide an additional treatment option for recurrent pericarditis patients.

Preclinical Development and Clinical Trials

Preclinical Development

In vitro studies with KPL-387 demonstrated its ability to potently inhibit IL-6 production from peripheral blood mononuclear cells when stimulated with either Il-1α or IL-1β. In vivo pharmacokinetic studies of KPL-387 in non-human primates demonstrated good pharmacokinetic properties. We believe that these pharmacokinetic data, combined with the potent inhibition of IL-1 signaling that we observed in vitro, suggest that this therapeutic effect could be achieved with monthly subcutaneous administration in future clinical studies.

Phase 1 Clinical Trial

In June 2024, we initiated a Phase 1 clinical trial of KPL-387 in healthy volunteers. Topline data from the trial have shown that a single subcutaneous dose of KPL-387 maintained levels in circulation sufficient to support our belief that the drug could offer the potential for monthly subcutaneous administration in recurrent pericarditis, a chronic disease that can last for years. We aim to explore this hypothesis further during Phase 2 development.

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Phase 2 Clinical Trial

In July 2025, we initiated our Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis, beginning with the Phase 2 dose-focusing portion of the study. The trial is designed to enroll up to approximately 80 patients with recurrent pericarditis who present at screening with a qualifying pericarditis episode despite treatment with conventional oral therapies. The primary efficacy endpoint is time to treatment response and time to CRP normalization (CRP ≤ 0.5mg/dL). We expect data from this trial in the second half of 2026 and plan to use the totality of the data to determine further development strategy. The following graphic shows the trial design in more detail:

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In addition, we are conducting a supplemental Phase 2 transition to KPL-387 monotherapy dosing and administration study to evaluate the efficacy and safety of dosing regimens used to transition patients from standard pericarditis therapies to KPL-387 monotherapy. The trial is designed to enroll up to 80 participants with well-controlled recurrent pericarditis receiving standard therapies (NSAIDS and/or colchicine, glucocorticoids and/or IL-1α and IL-1β inhibition). The following graphic shows the trial design in more detail:

KPL-1161

KPL-1161 is an independently developed, pre-clinical, Fc-modified immunoglobulin G2 monoclonal antibody that binds IL-1R1, inhibiting IL-1α- and IL-1β-mediated signaling. KPL-1161 is a modified version of KPL-387 designed to have an increased drug half-life that we believe could support quarterly subcutaneous dosing. We are currently conducting pre-clinical development of this asset and plan to initiate a Phase 1 first-in-human clinical trial of KPL-1161 by the end of 2026.

Abiprubart

Abiprubart is an investigational monoclonal antibody inhibitor of CD40-CD154 costimulatory interaction. We previously announced a Phase 2b clinical trial of abiprubart in Sjögren’s Disease. In February 2025, we announced our plans to discontinue development of abiprubart in the indication and explore strategic alternatives for the asset. We previously conducted a proof-of-concept Phase 2 clinical trial of abiprubart in RA and a Phase 2b clinical trial of abiprubart in Sjögren’s Disease. We believe that disrupting the CD40-CD154 co-stimulatory interaction is an attractive approach to addressing multiple autoimmune disease pathologies. We also believe that abiprubart’s ability to be administered in a high-concentration subcutaneous formulation that enables monthly dosing potentially distinguishes it from other competitors.

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Discovery Activities

We conduct internal discovery activities directed toward wholly owned molecules for the treatment of debilitating disease targets where we believe there to be a strong mechanistic rationale and potential for clear differentiation from existing approved agents or those in development.

Manufacturing

We do not currently own or operate any late-stage manufacturing facilities. Although we have built a development and manufacturing facility to produce drug substance to support certain research, preclinical and other clinical development for our product candidates, we rely, and expect to continue to rely, on third parties for the manufacture of our late-stage product candidates and certain of our early-stage product candidates for the majority of our clinical development efforts, as well as for the commercial manufacture of ARCALYST and our future products. Regeneron currently manufactures and supplies all of our requirements of ARCALYST for development and commercial activities pursuant to the Supply Agreement (as defined below). The Supply Agreement terminates upon the sooner of the termination of the Regeneron Agreement and the date of the completion of the transfer of technology related to the manufacture of ARCALYST drug substance. We are currently conducting a transfer of technology related to the manufacturing process of ARCALYST drug substance and the analytical testing methods of ARCALYST drug substance and drug product. As part of this process, we are working with Samsung, who will serve as the new manufacturer of ARCALYST drug substance and CTLs who will serve as the new analytical testing labs of ARCALYST drug substance and drug product. See, Risk Factors – Risks Related to Manufacturing and Our Reliance on Third Parties – We are conducting a technology transfer with respect to the manufacturing process of ARCALYST drug substance from Regeneron to Samsung and the analytical testing methods of ARCALYST drug substance and drug product to new CTLs. Such technology transfer will be subject to significant risks and uncertainties.” Fill-finish, labeling, packaging and shipping services are conducted by additional third-party contractors.

We also have engaged CDMOs to produce our clinical product candidates. We intend to use such CDMOs for development and scale-up work for any future clinical trials and eventual commercialization of such product candidates, if approved.

We require our CDMOs to conduct manufacturing activities in compliance with current good manufacturing practice or comparable foreign requirements (“cGMP”). We have assembled a team of experienced employees and consultants to provide the necessary technical, quality and regulatory oversight of our CDMOs. We currently perform most process development internally but are reliant on CDMOs for late-stage clinical product manufacturing, process qualification, validation and commercial supply. We anticipate that the CDMOs currently manufacturing our product candidates will have the capacity to support both future clinical supply and commercial-scale production, but we do not have any formal agreements at this time with any of such CDMOs to cover commercial production. We also may elect to pursue additional CDMOs for manufacturing supplies of drug substance and finished drug product in the future.

Our reliance on third parties to manufacture certain of our products and product candidates exposes us to risks, and any technology transfer of the manufacturing process for our products or product candidates may be subject to a number of risks and uncertainties, see “Risk Factors – Risks Related to Manufacturing and Our Reliance on Third Parties.”

Commercial Operations

Our commercial team combines years of pharmaceutical commercial leadership experience with a passion for helping patients with significant unmet medical need. Since March 2021, we have marketed ARCALYST, our only commercial product, in the United States for recurrent pericarditis and have established our own specialty salesforce to expand our commercialization efforts nationwide. For more information, see “Business—Our Products—ARCALYST – Commercial Strategy for ARCALYST.”

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Competition

The biotechnology and pharmaceutical industries are characterized by rapidly advancing technologies, intense competition and a strong emphasis on proprietary products. We face potential competition from many different sources, including pharmaceutical and biotechnology companies, academic institutions and governmental agencies and public and private research institutions. Our products and any product candidates that we successfully develop and commercialize may compete with existing products and new products that may become available in the future.

Competition poses a number of risks to our company, with a number of competitive factors affecting our ability to market and commercialize our products and product candidates. For more information, see “Risk Factors—Risks Related to Competition, Executing our Strategy and Managing Growth—We face substantial competition, which may result in others discovering, developing or commercializing drugs before or more successfully than we do.”

We are aware of the following drugs currently marketed or in clinical development for the treatment of the diseases that we are targeting or may plan to target:

ARCALYST

Recurrent Pericarditis: We are not aware of any other FDA-approved therapies for recurrent pericarditis, but we are aware of several competitors developing treatments for this indication. CardiolRx is an oral cannabidiol being developed by Cardiol Therapeutics in a Phase 3 clinical trial, targeting patients who are discontinuing treatment with an IL-1 blocker. R-Pharm International is developing goflikicept, which is a cytokine trap that inhibits IL-1α/IL-1β-induced signaling. This drug is approved and marketed in Russia but with no currently active trial in the United States. Ventyx Biosciences is developing VTX2735, which is designed to inhibit the NLRP3 inflammasome, an intracellular sensor of a broad range of danger signals, that leads to the production and release of IL-1β and IL-18. In addition to their development program in CAPS, Ventyx Biosciences is conducting a Phase 2 trial of VTX2735 in recurrent pericarditis, which began in January 2025. In January 2026, Ventyx Biosciences announced that it had entered into a definitive agreement to be acquired by Eli Lilly and Company (this acquisition is expected to close in the first half of 2026). Monte Rosa Therapeutics is developing MRT-8102 (a molecular glue degrader targeting NEK-7) and has announced plans to expand their ongoing Phase 1 proof-of-concept studies in individuals at high risk for cardiovascular disease and are planning to initiate a Phase 2 study in patients with atherosclerotic cardiovascular disease. They have indicated that they continue to evaluate additional indications including recurrent pericarditis.

Dual IL-1α and IL-1β Inhibition: Other drugs, while not approved for the treatment of recurrent pericarditis, also inhibit IL-1α/IL-1β-induced signaling. Anakinra (KINERET), marketed by Swedish Orphan Biovitrum AB, is currently approved for use in RA, CAPS and DIRA, and lutikizumab (a bispecific antibody targeting IL-1α andIL-1β) is being developed by Abbvie for the treatment of hidradenitis suppurativa, ulcerative colitis, atopic dermatitis, psoriatic arthritis, rheumatoid arthritis, and Crohn’s Disease.

IL-1β Inhibition Alone: There are also drugs that inhibit IL-1β-induced signaling but do not inhibit IL-1α-induced signaling. Canakinumab (ILARIS), marketed by Novartis Pharmaceuticals Corporation, is currently approved for use in CAPS, Tumor Necrosis Factor Receptor Associated Periodic Syndrome (TRAPS), Hyperimmunoglobulin D Syndrome (HIDS), Mevalonate Kinase Deficiency (MKD), Familial Mediterranean Fever (FMF), Adult Onset Still’s Disease (AOSD), Systemic Juvenile Idiopathic Arthritis (SJIA) and gout flares.

Other Competitors. We are also aware of several other molecules that do not directly compete with our approved indications for ARCALYST but nonetheless target IL-1α and/or IL-1β directly or indirectly. Development programs targeting IL-1α and/or IL-1β directly or indirectly via the NLRP3 inflammasome include: ZYIL-1 (by Zydus Lifesciences in amyotrophic lateral sclerosis); HT-6184 (by Halia in myelodysplastic syndromes, inflammatory pain); OLT1177 (by Olatec Therapeutics in osteoarthritis of the knee and acute gout flares); DFV-890 (by Novartis in FCAS); MAS-825 (by Novartis for the treatment of hidradenitis suppurativa and Still’s disease); Selnoflast (by Roche, no indications announced); NT-00249 (by NodThera, no indications announced); NT-0796 (by NodThera in obesity); Somalix and Inzomelid (by Roche, no indications announced); VTX-3232 (by Ventyx Bioscience in Parkinson’s); SSGJ-613 (by Sunshine Guojian Pharmaceuticals in acute gout); Natrunix (by XBIOTECH Inc in rheumatoid arthritis, axial

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spondylarthritis); AVTX-009 (by Avalo Therapeutics in hidradenitis suppurativa); CAN-10 (by Cantargia in healthy subjects and plaque psoriasis); PCRX-202 (by Pacira Biosciences, osteoarthritis of the knee), SAR445399 (by Sanofi in hidradenitis suppurativa); LAD191/ALM27134 (by Almirall in hidradenitis suppurativa) and VENT-02 (by Ventus Therapeutics, no indications announced). There are also therapies that modulate IL-1α-induced signaling in preclinical and clinical development for diseases other than recurrent pericarditis from Johnson & Johnson and XBIOTECH USA, INC. In addition, Invea Therapeutics is developing INVA8003, a small-molecule inhibitor targeting apoptosis-associated speck-like protein containing a caspase activation and recruitment domain, with a stated intent to prioritize an indication for which injectable IL-1α and/or IL-1β therapies are already approved.

KPL-387

Since we currently expect to develop KPL-387 for the treatment of recurrent pericarditis, we believe that it will compete with the same assets as those described under “Business—Competition—ARCALYST”, which includes a number of drugs that target IL-1α and/or IL-1β.

For recurrent pericarditis, there are a number of drugs in development that explore alternative dosing methods and frequencies to the once-weekly subcutaneous dosing method of ARCALYST, the only currently FDA-approved treatment. Both CardiolRx and VTX2735, in Phase 3 and 2 development by Cardiol Therapeutics and Ventyx Biosciences, respectively, are being investigated for oral administration. Goflikicept, currently marketed solely in Russia, though with prior clinical studies conducted in the United States, is dosed subcutaneously every two weeks following an initial loading dose. We expect that additional therapies offering even more convenient dosing and administration, including those listed in the sections above, may enter the market, including therapies that offer quarterly dosing. For KPL-387 to succeed on a commercial basis, if approved, we expect that it will need to compete against such drugs by offering a more convenient dosing regimen and/or an improved risk-benefit profile than other available options.

Abiprubart

There are various programs in clinical development antagonizing the CD40 / CD154 costimulatory pathway; however, we believe the high concentration liquid formulation of abiprubart may enable chronic subcutaneous dosing at a higher dose level than other similar drugs, which could be a key differentiator.

Amgen is developing Dazodalibep (anti-CD40L) for the treatment of Sjogren’s Syndrome with Moderate to Severe Systemic Disease Activity. Sanofi S.A./ImmuNext Inc. are developing frexalimab (anti-CD40L) for the treatment of Relapsing Multiple Sclerosis, Non-relapsing Secondary Progressive Multiple Sclerosis, Systemic Lupus Erythematosus, Type 1 Diabetes and Focal segmental glomerulosclerosis. Biogen, Inc. and UCB S.A. are developing dapirolizumab pegol (anti-CD40L) for the treatment of moderately to severely active Systemic Lupus Erythematosus. Eledon Pharmaceuticals, Inc. is developing tegoprubart (anti-CD40L) for use by patients undergoing kidney transplantation. AbbVie is developing Ravagalimab (anti-CD40) for the treatment of moderately to severely active Rheumatoid Arthritis. H. Lundbeck A/S is developing Lu AG22515 (bi-specific, anti-CD40L & Albumin (scFv)2-Fab) for the treatment of moderate to severe thyroid eye disease. Tonix Pharmaceuticals, Inc is developing TNX-1500 (anti-CD40L) for use in kidney transplant recipients. Innovent Bio is developing IBI-355 (anti-CD40L, no indication announced).

License and Acquisition Agreements

Out-Licensing Agreements

Genentech Agreement

In August 2022, we entered into a license agreement (the “Genentech License Agreement”) with Genentech, Inc. and F. Hoffmann-La Roche Ltd. (collectively, “Genentech”), pursuant to which we granted Genentech exclusive worldwide rights to develop, manufacture and commercialize vixarelimab and related antibodies (each, a “Genentech Licensed Product”).

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Under the Genentech License Agreement, we received an upfront payment of $80.0 million for the license. In total, we have recognized $50.0 million in additional payments from Genentech related to delivery of certain drug material to Genentech and Genentech’s achievement of development milestones under the Genentech License Agreement. We remain eligible to receive up to approximately $570.0 million in additional contingent payments, including specified development, regulatory and sales-based milestones, before fulfilling our upstream financial obligations to Biogen, Inc. (as further described in Note 13 to our consolidated financial statements included elsewhere in this Annual Report). We will also be eligible to receive tiered percentage royalties on a Genentech Licensed Product-by-Genentech Licensed Product basis ranging from low double digits to mid-teens on annual net sales of each Genentech Licensed Product, subject to certain customary reductions, with an aggregate minimum floor, before fulfilling our upstream financial obligations. Royalties will be payable on a Genentech Licensed Product-by-Genentech Licensed Product and country-by-country basis until the latest to occur of the expiration of certain patents that cover a Genentech Licensed Product, the expiration of regulatory exclusivity for such Genentech Licensed Product or the tenth anniversary of first commercial sale of such Genentech Licensed Product in such country.

Absent early termination, the Genentech License Agreement will continue until there are no more royalty or other payment obligations owed to us. Genentech has the right to terminate the Genentech License Agreement at its discretion with prior written notice and either party may terminate the Genentech License Agreement in the event of an uncured material breach of the other party or in the case of insolvency of the other party. In addition, the Genentech License Agreement will terminate upon termination of our upstream license agreement related to vixarelimab.

Huadong Collaboration Agreements

In February 2022 we entered into two collaboration and license agreements (each, a “Huadong Collaboration Agreement” and together, the “Huadong Collaboration Agreements”) with Huadong, pursuant to which we granted Huadong exclusive rights to develop and commercialize ARCALYST and develop, manufacture and commercialize mavrilimumab in each case in a territory currently consisting of the following countries: People’s Republic of China, Hong Kong SAR, Macao SAR, Taiwan Region, Indonesia, The Philippines, Thailand, Bangladesh, Bhutan, Brunei, Burma, Cambodia, India, Laos, Malaysia, Maldives, Mongolia, Nepal, New Zealand, Sri Lanka and Vietnam (collectively, the “Huadong Territory”). We otherwise retained our rights to ARCALYST and mavrilimumab outside the Huadong Territory.

In April 2025, we and Huadong entered into a mutual termination agreement pursuant to which we agreed to terminate the mavrilimumab Huadong Collaboration Agreement and release all claims related thereto. The ARCALYST Huadong Collaboration Agreement remains in effect.

Under the Huadong Collaboration Agreements, we received a total upfront cash payment of $22.0 million, which includes $12.0 million for the Huadong Territory license of ARCALYST and $10.0 million for the Huadong Territory license of mavrilimumab. In the fourth quarter of 2024, following the achievement of a regulatory milestone under the ARCALYST Huadong Collaboration Agreement, Huadong became obligated to make an additional cash payment of $20.0 million, which was received in the first quarter of 2025. We remain eligible to receive up to approximately $50.0 million in sales-based milestone payments for ARCALYST. Due to its termination, we do not expect to receive any future payments under the mavrilimumab Huadong Collaboration Agreement. Huadong will also be obligated to pay us tiered percentage royalties ranging from the low to mid-teens on annual net sales of ARCALYST in the Huadong Territory, subject to certain reductions tied to ARCALYST manufacturing costs and certain other customary reductions, with an aggregate minimum floor. Royalties will be payable on a country-by-country or region-by-region basis until the later of (i) 12 years after the first commercial sale of ARCALYST in such country or region in the Huadong Territory, (ii) the date of expiration of the last valid patent claim of our patent rights or any joint collaboration patent rights that covers ARCALYST in such country or region in the Huadong Territory and (iii) the expiration of the last regulatory exclusivity for ARCALYST in such country or region in the Huadong Territory.

Pursuant and subject to the terms of the Huadong Collaboration Agreements, Huadong has the exclusive right to conduct Huadong Territory-specific development activities for ARCALYST in the Huadong Territory, the first right to support global development of ARCALYST by serving as the sponsor of the global clinical trials conducted in the Huadong Territory and the exclusive right to commercialize ARCALYST in the Huadong Territory. Huadong will be

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responsible for all costs of development activities and commercialization in the Huadong Territory. We and Huadong participate in a joint steering committee, which coordinates and oversees the exploitation of ARCALYST in the Huadong Territory.

We will supply certain materials to support development and commercialization activities for ARCALYST.

Absent early termination, the ARCALYST Huadong Collaboration Agreement will continue on a country-by-country or region-by-region basis until there are no more royalty payments owed to us in such country or region. Huadong has the right to terminate the ARCALYST Huadong Collaboration Agreement at its discretion upon 12 months’ notice and either party may terminate the ARCALYST Huadong Collaboration Agreement in the event of an uncured material breach of the other party or in the case of insolvency of the other party. In addition, we may terminate the ARCALYST Huadong Collaboration Agreement if Huadong or its affiliates or sublicensees challenges the scope, validity or enforceability of our patent rights being licensed to Huadong. If Huadong and its affiliates do not conduct any material development or commercialization activities for ARCALYST in the People’s Republic of China for a continuous period of longer than six months, then, subject to certain exceptions, we may terminate the ARCALYST Huadong Collaboration Agreement with 60 days’ prior written notice. In addition, Huadong’s rights under the ARCALYST Huadong Collaboration Agreement in certain regions within the Huadong Territory may be subject to termination upon failure by Huadong to perform certain clinical, development or commercialization activities, as applicable, in such regions.

In-Licensing Agreements

License Agreement with Regeneron

In September 2017, we entered into a license agreement with Regeneron (the “Regeneron Agreement”)”), pursuant to which we were granted an exclusive license under certain intellectual property rights controlled by Regeneron to develop and commercialize ARCALYST worldwide, excluding the Middle East and North Africa, for all indications other than those in oncology and local administration to the eye or ear. Upon receiving positive data in RHAPSODY, our pivotal Phase 3 clinical trial of ARCALYST, Regeneron transferred the biologics license application (“BLA”) for ARCALYST to us. In March 2021, when the FDA granted approval of ARCALYST for the treatment of recurrent pericarditis and reduction in risk of recurrence in adults and children 12 years and older, we assumed the sales and distribution of ARCALYST for CAPS and DIRA in the United States.

Under the Regeneron Agreement, we paid $32.5 million in connection with upfront fees and the achievement of regulatory milestones. We evenly split profits on sales of ARCALYST with Regeneron, where profits are determined after deducting from net sales of ARCALYST certain costs related to the manufacturing and commercialization of ARCALYST. Such costs include but are not limited to (i) our cost of goods sold for product used, sold or otherwise distributed for patient use by us; (ii) customary commercialization expenses, including the cost of our field force and (iii) our cost to market, advertise and otherwise promote ARCALYST, with such costs identified in subsection (iii) subject to specified limits. To the extent permitted in accordance with the Regeneron Agreement, the fully-burdened costs incurred by each of us and Regeneron in performing (or having performed) the technology transfer of the manufacturing process for ARCALYST drug substance will also be deducted from net sales of ARCALYST to determine profit. We also evenly split with Regeneron any proceeds received by us from any licensees, sublicensees and distributors in consideration for the sale, license or other disposition of rights with respect to ARCALYST, including upfront payments, milestone payments and royalties.

The Regeneron Agreement will expire on the date on which we, our affiliates or sublicensees are no longer developing or commercializing any product containing ARCALYST. We may terminate the agreement for convenience at any time with one year’s written notice. We may also terminate with three months’ written notice if we reasonably determine that ARCALYST is unsafe in the indications we are pursuing. Regeneron may terminate the agreement if there is a consecutive twelve-month period during which we do not conduct any material development or commercialization activities or we do not grant a sublicense to a third party to do so, or if we challenge Regeneron’s patent rights in any country in our territory. Either party may terminate the agreement in the event of a material breach

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by the other party that remains uncured for 90 days (or 30 days for payment-related breaches), or by either party due to the insolvency or bankruptcy of the other party.

We have also entered into a commercial supply agreement with Regeneron (the “Supply Agreement”), under which Regeneron agreed to manufacture product for our clinical and commercial use. The Supply Agreement terminates upon the sooner of the termination of the Regeneron Agreement and the date of the completion of the transfer of technology related to the manufacture of ARCALYST drug substance.

Beth Israel Deaconess Medical Center License Agreement

In 2019, we acquired all of the outstanding securities of Primatope Therapeutics, Inc. (“Primatope”), the company that owned or controlled the intellectual property related to abiprubart. In connection with our acquisition of Primatope, we acquired the rights to an exclusive license to certain intellectual property rights controlled by BIDMC to make, use, develop and commercialize abiprubart under the BIDMC license agreement (the “BIDMC Agreement”). Under the BIDMC Agreement, we are solely responsible for all development, regulatory and commercial activities and costs. We are also responsible for costs related to filing, prosecuting and maintaining the licensed patent rights. Under the BIDMC Agreement, we are obligated to pay an insignificant annual maintenance fee as well as future clinical and regulatory milestone payments of up to an aggregate of $1.2 million to BIDMC. We are also obligated to pay a low single-digit royalty on annual net sales of products licensed under the agreement, if approved.

Intellectual Property

Our success depends in part on our ability to obtain and maintain proprietary protection for our drug candidates, manufacturing and process discoveries and other know-how, to operate without infringing the proprietary rights of others and to prevent others from infringing our proprietary rights. We plan to protect our proprietary position using a variety of methods, which include pursuing United States and foreign patent applications related to our proprietary technology, inventions and improvements, which can include compositions of matter, drug product formulations, methods of use and methods of manufacture. We also rely on trade secrets, know-how, continuing technological innovation and potential in-licensing opportunities to develop and maintain our proprietary position.

ARCALYST

We have a field-specific exclusive license under the Regeneron Agreement to granted patents and pending applications in the United States and numerous other jurisdictions relating to ARCALYST. A United States patent covering ARCALYST as a composition of matter expired in 2020, and relevant composition of matter patents issued outside of the United States expired in 2023. Five patents covering methods of using ARCALYST in the treatment of recurrent pericarditis have issued in the United States and have a statutory term that expires in 2038, not including any patent term adjustment. In March 2021, the FDA granted approval for ARCALYST for the treatment of recurrent pericarditis and reduction in risk of recurrence in adults and children 12 years of age and older, which granted us seven years of marketing exclusivity in the United States. See “Business—In-Licensing Agreements – License Agreement with Regeneron” above for additional information on our rights under the Regeneron Agreement.

KPL-387

We own pending patent applications relating to KPL-387, which cover formulations and methods of manufacturing KPL-387. If issued, such patents will have statutory expiration dates in 2045, not including any patent term extensions or adjustments. As of December 31, 2025, one patent covering KPL-387 formulations has issued in the United States, expiring in 2045, not including any patent term extensions. We also own a pending patent application covering methods of using KPL-387 in the treatment of recurrent pericarditis. If issued, patents covering methods of using KPL-387 in treating recurrent pericarditis will have statutory expiration dates in 2046, not including any patent term extensions or adjustments. If we are successful in obtaining regulatory approval of KPL-387 for the treatment of recurrent pericarditis, we also expect to rely on data exclusivity and orphan exclusivity (if we satisfy the criteria for orphan drug exclusivity at the time of approval and thereafter) to protect our market position. For example, in the United States, a new biologic product receives 12 years of data exclusivity upon receiving regulatory approval. In the EU, a new

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product generally receives eight years of data exclusivity and an additional two years of market exclusivity upon regulatory approval. See “Business –Government Regulation” below for additional information on regulatory exclusivities.

KPL-1161

We own a pending patent application relating to KPL-1161, which covers composition of matter. If issued, patents covering the composition of matter will have statutory expiration dates in 2046, not including any patent term extensions or adjustments.

Abiprubart

We own, via our acquisition of Primatope, granted patents and pending patent applications in the United States and numerous other jurisdictions relating to abiprubart. We also have an exclusive license with BIDMC to granted patents and pending patent applications in the United States and numerous other jurisdictions relating to abiprubart. These patents and patent applications cover abiprubart as a composition of matter and its use. As of December 31, 2025, the patent rights acquired from Primatope include four patents granted in the United States and 32 patents granted in other jurisdictions, including Australia, Brazil and selected countries in Europe and Asia. In addition, the patent rights acquired from Primatope include patent applications pending in the United States, Australia, Europe, Canada and selected countries in Asia. The issued composition of matter patents acquired from Primatope have statutory expiration dates in 2036, not including any patent term extensions or adjustments. As of December 31, 2025, the patent rights licensed from BIDMC include two patents granted in the United States and 58 patents granted in other jurisdictions, including Australia, Canada and selected countries in Europe and Asia. In addition, the patent rights licensed from BIDMC include patent applications pending in the United States, Europe and Canada. The issued composition of matter patents licensed from BIDMC have statutory expiration dates in 2032, not including any patent term extensions or adjustments. Patent term extension could extend the expiration date of one patent in the United States and patents in certain other jurisdictions, each in accordance with applicable law.

Other Intellectual Property

In addition to the above, we maintain certain other intellectual property, including patents, trademarks and know-how, related to our other assets, pre-clinical development and broader Kiniksa brand.

There can be no assurances that patents will issue from any of our pending patent applications or that any of our existing patents may be extended. See “Risk Factors—Risks Related to Intellectual Property.”

In the future, if and when our drug candidates receive approval by the FDA or comparable regulatory authorities in other jurisdictions (as applicable, “regulatory authorities”), provided the legal requirements are met, we expect to apply for patent term extensions on issued patents covering those drugs, depending upon the length of the clinical trials for each drug and other factors. There can be no assurance that any of our pending patent applications will issue or that we will benefit from any patent term extension or favorable adjustment to the term of any of our patents.

Government Regulation

Government authorities in the United States at the federal, state and local level and in other countries and jurisdictions, including the European Union, extensively regulate, among other things, the research, development, testing, manufacture, quality control, approval, labeling, packaging, storage, record-keeping, promotion, advertising, distribution, post-approval monitoring and reporting, marketing and export and import of drug products. The process of obtaining regulatory approvals and the subsequent compliance with applicable federal, state, local and foreign statutes and regulations requires the expenditure of substantial time and financial resources. Generally, before a new drug can be marketed, considerable data demonstrating its quality, safety and efficacy must be obtained, organized into a format specific for each regulatory authority, submitted for review and approved by the regulatory authority.

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United States Government Regulation of Biological Products

In the United States, the FDA regulates biologics under the Federal Food, Drug, and Cosmetic Act (the “FDCA”) and the Public Health Service Act (the “PHSA”) and their implementing regulations. Biologics are also subject to other federal, state and local statutes and regulations.

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

● FDA review and approval of the BLA.

Preclinical Studies

Before testing any biological product candidate, including our product candidates, in humans, the product candidate must undergo rigorous preclinical testing. The preclinical development stage generally involves laboratory evaluations of the chemistry, formulation and stability of the product candidate, as well as animal trials to evaluate toxicity. The conduct of the preclinical tests must comply with federal regulations and requirements, including GLP regulations. Before conducting a clinical trial in the United States, the sponsor must provide the results of the preclinical studies as part of an IND submitted to the FDA, along with other information, including information about chemistry, manufacturing and controls (“CMC”). An IND is a request for authorization from the FDA to administer an investigational product to humans and must become effective before human clinical trials may begin. An IND automatically becomes effective 30 days after receipt by the FDA, unless before that time the FDA places the clinical trial on hold and the IND sponsor must resolve any outstanding issues before clinical trials can proceed.

Clinical Trials

Clinical trials involve the administration of the investigational product to normal healthy volunteers or participants under the supervision of qualified investigators. Clinical trials must be conducted in accordance with GCPs, which include the requirement that all research subjects provide their informed consent for their participation in any clinical trial. Clinical trials also must be conducted under protocols detailing, among other things, the objectives of the clinical trial, dosing procedures, participant selection and inclusion/exclusion criteria and the parameters to be used to monitor subject safety and assess efficacy. Each protocol, and any subsequent amendments to the protocol, must be submitted to the FDA as part of the IND. Furthermore, an IRB representing each institution at which the clinical trial

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will be conducted must review and approve the plan for any clinical trial, including, among other things, the protocol and informed consent information to be provided to clinical trial subjects or their legal representatives, to ensure that the risks to individuals participating in the clinical trials are minimized and are reasonable in relation to anticipated benefits. The IRB also must monitor the clinical trial until completed.

Some clinical trials also include oversight by an independent group of qualified experts organized by the clinical study sponsor, commonly known as a Data Safety Monitoring Board (a “DSMB”) or Data Monitoring Committee (a “DMC”), which may recommend continuation of a trial as planned, changes in the trial or cessation of the trial at designated check points based on access to certain data from the trial. The FDA or the sponsor may suspend or terminate a clinical trial at any time on various grounds, including a finding that the participants are being exposed to an unacceptable health risk. Similarly, an IRB can suspend or terminate approval of a clinical trial at its institution if the clinical trial is not being conducted in accordance with the IRB’s requirements or if the drug has been associated with unexpected serious harm to participants. There also are requirements governing the reporting of ongoing clinical trials and completed clinical trial results to public registries.

Human clinical trials are typically conducted in three sequential phases, which may overlap or be combined.

Post-approval trials, sometimes referred to as Phase 4 clinical trials, may be conducted after initial marketing approval. These trials are used to gain additional experience from the treatment of participants in the intended therapeutic indication, particularly for long-term safety follow up. In certain instances, the FDA may mandate the performance of Phase 4 clinical trials as a condition of approval of a BLA.

BLA Review and Approval

Assuming successful completion of the required clinical testing, the results of the preclinical studies and clinical trials, together with detailed information relating to the product’s CMC and proposed labeling, among other things, are submitted to the FDA as part of a BLA requesting marketing approval for a product for one or more indications. To support marketing approval, the data submitted from company sponsored clinical trials or potentially other alternative sources must be sufficient in quality and quantity to establish the safety, purity and potency (or efficacy) of the investigational product to the satisfaction of the FDA. In relevant cases, the BLA must include data relevant to safety, efficacy and dosing for pediatric populations. FDA approval of a BLA must be obtained before a biologic may be marketed in the United States.

In most cases, the submission of a BLA is subject to a substantial application user fee. Within 60 days following submission of the application, the FDA reviews all BLAs submitted to ensure that they are sufficiently complete for substantive review before it accepts them for filing. The FDA may require the sponsor to provide additional information before accepting the BLA for filing. Once the BLA submission is accepted for filing, the FDA begins an in-depth substantive review. The FDA reviews a BLA to determine, among other things, whether the product is safe, pure and potent and the facility in which it is manufactured, processed, packed or held meets standards designed to assure the

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product’s continued safety, purity and potency. Most BLAs are reviewed within ten months from the filing date or six months from the 60-day filing date for BLAs with priority review, subject in each case to extensions by the FDA.

Before approving a BLA, the FDA will typically conduct a pre-approval inspection of the manufacturing facilities for the new product to determine whether the manufacturing processes and facilities comply with cGMPs and are adequate to ensure consistent product production within required specifications. The FDA also may inspect the sponsor and one or more clinical trial sites to assure compliance with GCP requirements and integrity of the clinical data submitted to the FDA.

Additionally, the FDA may refer applications for novel biologic candidates, which present challenges in interpretation of the safety or efficacy data, to an Advisory Committee, typically a panel that includes clinicians and other experts appointed by the FDA Commissioner or a designee, for review, evaluation and a recommendation as to whether the application should be approved. The FDA is not bound by the recommendations of an advisory committee, but it considers such recommendations when making decisions on approval.

The BLA approval process is lengthy and difficult, and the FDA may refuse to approve a BLA if the applicable regulatory criteria are not satisfied or may require additional clinical or other data and information. After the FDA evaluates a BLA, it will issue an approval letter or a Complete Response Letter (“CRL”). An approval letter authorizes commercial marketing of the product with specific prescribing information for specific indications. A CRL indicates the deficiencies in the submission and may require substantial additional testing or information for the FDA to reconsider the BLA. If and when the deficiencies have been addressed to the FDA’s satisfaction, the FDA will issue an approval letter.

FDA approval authorizes commercial marketing of a drug or biologic product with specific prescribing information and for specific indications. As a condition of approval, the FDA may require, among other things, post-approval trials or testing and surveillance programs to monitor the product after commercialization or implementation of a risk evaluation and mitigation strategy (“REMS”) to ensure the benefits of the product outweigh the potential risks. The FDA may prevent or limit further marketing of a product based on the results of post-marketing trials or surveillance programs, or new safety findings after market introduction. After approval, certain changes to the approved product, such as adding new indications, manufacturing changes and additional labeling claims, are subject to further testing requirements and FDA review and approval.

Orphan Drug Designation

Under the Orphan Drug Act, the FDA may grant orphan designation to a drug or biologic product intended to treat a rare disease or condition, which is generally a disease or condition that affects fewer than 200,000 individuals in the United States or more than 200,000 individuals in the United States and for which there is no reasonable expectation that the cost of developing and making the product available in the United States for this type of disease or condition will be recovered from sales of the product. After the FDA grants Orphan Drug designation, the identity of the therapeutic agent and its potential orphan use are disclosed publicly by the FDA. Orphan Drug designation does not convey any advantage in, or shorten the duration of, the regulatory review and approval process.

Orphan Drug designation entitles a party to financial incentives such as opportunities for grant funding towards clinical trial costs, tax advantages and user-fee waivers. In addition, 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 Orphan Drug exclusivity, which means that the FDA may not approve any other applications to market the same drug for the same indication for seven years from the date of such approval, except in limited circumstances, such as a showing of clinical superiority to the product with orphan exclusivity.

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

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Expedited Review and Approval

The FDA is authorized to designate certain product candidates for expedited development and review if they are intended to address an unmet medical need in the treatment of a serious or life-threatening disease or condition. These programs include Fast Track designation, Breakthrough Therapy designation, accelerated approval and priority review.

To be eligible for a Fast Track designation, the FDA must determine, based on the request of a sponsor, that a product is intended to treat a serious or life-threatening disease or condition and demonstrates the potential to address an unmet medical need for such disease or condition. Fast Track designation provides opportunities for more frequent interactions with the FDA review team to expedite development and review of the product. The FDA may also review sections of the BLA for a Fast Track product on a rolling basis before the complete application is submitted, if the sponsor and the FDA agree on a schedule for the submission of the application sections, and the sponsor pays any required user fees upon submission of the first section of the BLA.

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

A product candidate intended to treat serious or life-threatening diseases or conditions may be eligible for accelerated approval upon a determination that the product candidate has an effect on a surrogate endpoint that is reasonably likely to predict clinical benefit, or on a clinical endpoint that can be measured earlier than irreversible morbidity or mortality, that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit, taking into account the severity, rarity or prevalence of the condition and the availability or lack of alternative treatments. As a condition of approval, the FDA generally requires that a sponsor of a product receiving accelerated approval perform adequate and well-controlled confirmatory clinical trials to verify the predicted clinical benefit. A product that receives accelerated approval may be subject to expedited withdrawal procedures if the sponsor fails conduct the required confirmatory trials in a timely manner or if such trials fail to verify the predicted clinical benefit. In addition, the FDA currently requires as a condition for accelerated approval pre-approval of promotional materials, which could adversely impact the timing of the commercial launch of the product.

The FDA may designate a product candidate for priority review if the product candidate is designed to treat a serious condition, and if approved, would provide a significant improvement in safety or effectiveness compared to marketed products. The FDA will attempt to direct additional resources to the evaluation of an application for a biologic designated for priority review in an effort to facilitate the review. The FDA endeavors to review original BLAs with priority review designations within six months of the filing date as compared to ten months under its standard review goals.

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

Post-approval Requirements

Once a BLA is approved, a product will be subject to certain post-approval requirements. For instance, the FDA closely regulates the post-approval marketing and promotion of drugs and 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. Drugs and biologics may only be marketed for the approved indications and in accordance with the provisions of the approved labeling.

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Adverse event reporting and submission of periodic reports are required following FDA approval of a BLA.

In addition, FDA regulations require that products be manufactured in specific approved facilities and in accordance with cGMPs. We rely, and expect to continue to rely, on third party CDMOs for the production of clinical and commercial quantities of our products in accordance with cGMP regulations. We, and our CDMOs are required to register our establishments with the FDA and certain state agencies. Registration with the FDA subjects us and our CDMOs to periodic unannounced inspections by the FDA, during which the agency inspects manufacturing facilities to assess compliance with cGMPs. Accordingly, we and our CDMOs must continue to expend time, money and effort in the areas of production and quality-control to maintain compliance with cGMPs.

Later discovery of previously unknown problems with a product, including adverse events of unanticipated severity or frequency, or failure to comply with regulatory requirements, may result in, among other things:

● injunctions or the imposition of civil or criminal penalties; and

Biosimilars and Exclusivity

An abbreviated approval pathway for biological products that are biosimilar to or interchangeable with an FDA-licensed reference biological product was created by the Biologics Price Competition and Innovation Act of 2009 (the “BPCIA”) as part of the Patient Protection and Affordable Care Act, as amended by the Health Care and Education Reconciliation Act (the “ACA”).

Under the BPCIA, a manufacturer may submit an application for a biological product that is “biosimilar to” or “interchangeable with” a previously approved “reference product.” Biosimilarity requires that the biological product be highly similar to the reference product and that there be no clinically meaningful differences in safety, purity and potency. This must be demonstrated through analytical studies, animal studies and a clinical trial or trials. In order to meet the higher hurdle of interchangeability, a sponsor must demonstrate that the biosimilar product can be expected to produce the same clinical result as the reference product, and for a product that is administered more than once, that the risk of switching between the reference product and biosimilar product is not greater than the risk of maintaining the patient on the reference product.

Under the BPCIA, a reference biological product is granted 12 years of data exclusivity from the time of first licensure of the product, and the FDA will not accept an application for a biosimilar or interchangeable product based on the reference biological product until four years after the date of first licensure of the reference product.

Foreign Government Regulation

In addition to regulations in the United States, we are subject to a variety of regulations in other jurisdictions governing, among other things, clinical trials, marketing authorization, post-marketing requirements and any commercial sales and distribution of products approved in such jurisdictions. The product approval process ultimately varies between

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countries and jurisdictions and can involve additional product testing and additional administrative review periods. The time required to obtain approval in other countries and jurisdictions might differ from and be longer than that required to obtain FDA approval. Regulatory approval in one country or jurisdiction does not ensure regulatory approval in another, but a failure or delay in obtaining regulatory approval in one country or jurisdiction may negatively impact the regulatory process in others.

Regulatory Framework in the European Union

Clinical Trials

Clinical trials of medicinal products in the European Union (“EU”) are governed by the Clinical Trials Regulation (EU) No 536/2014 (the “CTR”), which became applicable on January 31, 2022, and repealed the Clinical Trials Directive. 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 (“CTIS”), which contains a centralized EU portal and database. 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.

While the Clinical Trials Directive required a separate clinical trial application (a “CTA”) to be submitted in each member state, to both the competent national health authority and an independent ethics committee, much like the FDA and IRB respectively, the CTR introduces a centralized process and only requires the submission of a single application to all member states concerned to streamline the regulatory review. 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 information concerning the trial protocol and the manufacture and quality of the medicinal product under investigation. The assessment procedure of the CTA has been harmonized. For each clinical trial submitted in CTIS, one reporting member state will lead the assessment process for those elements of the clinical trial application that are common throughout the EU, and member states concerned by the application may raise objections to the reporting member state’s assessment. Each member state is responsible for assessing the elements specific to its own territory, including ethics rules. Once the CTA is approved, clinical study development may proceed. Documents and data from the CTA are made publicly available through CTIS at time of decision about the clinical trial, subject to the redaction of personal data and confidential information.

Since January 2025, all clinical trials (including those which are ongoing but approved under the previous legal framework) are regulated by the CTR.

Medicines used in clinical trials must be manufactured in accordance with cGMP. Other national and EU-wide regulatory requirements may also apply.

Marketing Authorization

In the EU, medicinal products can only be placed on the market after obtaining a marketing authorization (an “MA”). To obtain a MA of a product candidate in the EU, we must submit a MA application (an “MAA”). The process for doing this depends, among other things, on the nature and therapeutic category of the medicinal product. There are two types of MAs that can be granted by the relevant competent authorities:

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MAs have an initial duration of five years. After this period, the authorization may be renewed and its validity extended, subject to a satisfactory reevaluation of the risk-benefit balance of the product.

In the EU, a “conditional” MA may be granted in cases where all the required safety and efficacy data are not yet available. The European Commission may grant a conditional MA for a medicinal product if it is demonstrated that all of the following criteria are met: (i) the benefit-risk balance of the medicinal product is positive; (ii) it is likely that the applicant will be able to provide comprehensive data post-authorization; (iii) the medicinal product fulfils an unmet medical need; and (iv) the benefit of the immediate availability to patients of the medicinal product is greater than the risk inherent in the fact that additional data are still required. A conditional MA is subject to specific obligations such as generating comprehensive evidence to confirm the benefit-risk balance of the product. It is valid for one year and must be renewed annually until all conditions are fulfilled. Once outstanding data are provided and satisfactorily assessed, the conditional MA can be converted into a standard (traditional) MA. However, if the conditions are not fulfilled within the timeframe set by the EMA and approved by the European Commission, the MA will cease to be renewed or may be revoked.

Data and Marketing Exclusivity

The EU also provides opportunities for marketing exclusivity. Newly authorized products that qualify as reference medicinal products – based on a complete, stand-alone dossier consisting of pharmaceutical, non-clinical and clinical trial data – receive eight years of data exclusivity, followed by additional two years of marketing exclusivity upon receiving an MA. During the data exclusivity period in the EU, biosimilar applicants are not permitted to rely on the pre-clinical and clinical trial data contained in the dossier of the reference product when applying for a biosimilar MA. Once the eight-year data exclusivity has expired, a biosimilar MAA can be submitted and approved. However, no biosimilar product can be commercialized until the full ten-year exclusivity period has expired. The overall ten-year data and marketing 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.

Approval of a biosimilar differs from the conventional regulatory process for approving generic products because biosimilars do not meet the definition of a generic medicinal product. This is primarily due to differences in raw materials or manufacturing processes or the complex nature of biological products. Approval of a biosimilar require submission of appropriate preclinical or clinical trial results. The EMA and its advisory committees have developed detailed guidelines specifying the type of supplementary data that should be provided for different classes of biological products. These guidelines outline the evidence necessary to demonstrate that the biosimilar is comparable to the

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reference product in terms of quality, safety, and efficacy. Currently, there exist no specific guidelines for complex biological products, such as gene or cell therapy medicinal products. The EMA has indicated that guidance for such complex biological products may be developed in the future, taking into account advancements in scientific knowledge and regulatory experience as they are gained.

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Orphan Medicinal Products

The criteria for designating an “orphan medicinal product” in the EU, are broadly similar to those in the United States with the additional requirement in the EU to demonstrate significant benefit during the designation procedure. Under Article 3 of Regulation (EC) 141/2000, 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. Orphan medicinal products are eligible for financial incentives such as reduction of fees or fee waivers 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, grant an MA or accept an application to extend a MA for a similar product for the same indication. Orphan Drug designation does not confer any advantage in, or shorten the duration of, the regulatory review and approval process.

The ten-year market exclusivity in the EU 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. 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 marketing authorization holder for the first approved product consents to a second orphan medicinal product application; or (iii) the marketing authorization holder cannot supply sufficient quantities of the approved orphan medicinal product.

Pediatrics Development

In the EU, MAAs for new medicinal products must be accompanied by the results of studies contained in a pediatric investigation plan (a “PIP”) agreed with the EMA’s Pediatric Committee (the “PDCO”), unless a deferral or a waiver applies. The PIP sets out the timing and measures proposed to generate the necessary data determining the conditions in which a medicinal product may be authorized to treat the pediatric population. The PDCO can grant a deferral of the obligation, allowing the requirement to carry out some or all of the measures of the PIP to be postponed until sufficient data are available 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 such data are necessary 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 EU member states and study results are included in the product information, regardless of whether those results would lead to approval of a pediatric indication, the product is eligible for six months’ supplementary extension of the basic patent protection under a supplementary protection certificate (if one is in effect at the time of approval) or, in the case of orphan medicinal products, a two-year extension of the ten-year orphan market exclusivity may be granted under the same conditions. An extension of a supplementary protection certificate cannot be granted for orphan medicinal products, and only one of these incentives may be awarded.

PRIME Designation

In the EU, innovative products that address conditions with an unmet medical need – either because no treatment option exists or because they can offer a major therapeutic advantage over existing treatments– may be eligible for early and proactive support. Such products can benefit from a range of expedited development and review programs, including the Priority Medicines (“PRIME”) scheme, which shares a common objective with the US Breakthrough Therapy designation to optimize and accelerate the development and regulatory assessment of promising therapies. The benefits of a PRIME designation include the appointment of a rapporteur before submission of an MAA, early dialogue and scientific advice at key development milestones and the potential to qualify products for accelerated review earlier in the application process. Product developers that benefit from PRIME designation may be eligible for accelerated assessment (in 150 days instead of 210 days), which may be granted for medicinal products of major interest from a public health perspective or that target an unmet medical need, but this is not guaranteed.

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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 EU member states. The holder of an MA for a medicinal product must also comply with pharmacovigilance legislation and its related regulations and guidelines, which entail many requirements for conducting pharmacovigilance, or the assessment and monitoring of the safety of medicinal products. The holder of a MA must establish and maintain a pharmacovigilance system and appoint a qualified person for pharmacovigilance (a “QPPV”) who is responsible for the establishment and maintenance of that system. MA holders required to record all suspected adverse reactions within and outside the EU and report all serious suspected adverse reactions expeditiously. In addition, MA holders are required to submit periodic safety update reports (“PSURs”) or periodic benefit-risk evaluation reports to evaluate the benefit-risk balance of a medicinal product at defined time points after its authorization.

All new MAAs must include a risk management plan (“RMP”), describing the risk management system consisting of a set of pharmacovigilance activities and interventions designed to identify, characterize, prevent or minimize the risks relating to a medicinal product, including the assessment of those activities and interventions. The RMP must be updated whenever new information becomes available that significantly impacts its content. The regulatory authorities may also impose specific obligations as a condition of the MA. These risk-minimization measures or post-authorization requirements may include additional safety monitoring, more frequent submission of PSURs or the conduct of additional clinical trials or post-authorization safety studies.

Advertising and promotion of medicinal products are subject to strict legal requirements, including those governing interactions with healthcare professionals, 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 prohibited in the EU. Although general requirements for advertising and promotion of medicinal products are established under EU directives, the specific rules are set out in national regulations and the codes of conduct of various trade associations within each member state for the rules to be enforced. As a result, the detailed requirements and enforcement practices can vary from country to country.

Failure to comply with EU and national 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 medicinal products, 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 an 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.

Regulatory Framework in the United Kingdom

Since the end of the Brexit transition period on January 1, 2021, Great Britain (England, Scotland and Wales) has not been directly subject to EU laws. However, under the terms of the Ireland/Northern Ireland Protocol, EU laws applied to Northern Ireland. In February 2023, the EU and UK reached an agreement, known as the Windsor Framework, on the future of trade with Northern Ireland, which amends certain aspects of the Northern Ireland protocol. Pursuant to the Northern Ireland protocol, different medicinal product regulatory regimes applied in Great Britain (being England, Scotland and Wales) and Northern Ireland. In particular, Northern Ireland was bound by EU law concerning medicinal products, whereas Great Britain was not. The Windsor Framework corrects this by disapplying EU pharmaceutical law in Northern Ireland and ensuring regulatory continuity between Great Britain and Northern Ireland. In practice this means that, since these provisions took effect on January 1, 2025, medicinal products destined for sale in both Great Britain and Northern Ireland must be sold under one marketing authorization (MA), and in the same packaging and labelling.

The EU laws that have been transposed into United Kingdom (the “UK”) law through secondary legislation remain applicable in Great Britain. However, under the Retained EU Law (Revocation and Reform) Act 2023, which

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received royal assent on June 29, 2023, any retained EU law not expressly preserved and “assimilated” into domestic law or extended by ministerial regulations (to no later than June 23, 2026) was automatically expired and revoked by December 31, 2023. New legislation such as the EU CTR or in relation to orphan medicines is, therefore, not applicable to Great Britain. The UK government has passed a new 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 (the “MHRA”) is the UK’s standalone medicines and medical devices regulator.

To be used or sold in the UK, a drug must have a valid MA granted through the national application process. National applications are governed by the Human Medicines Regulations (SI 2012/1916). Applications are made electronically through the MHRA Submissions Portal. The MHRA operates fixed submission and assessment timetables for innovative medicines applications to facilitate consultation with its statutory advisory committee, the Commission on Human Medicines (“CHM”). The MHRA assessment procedure for a MA application involves an initial evaluation, including orphan designation if applicable, and consultation with expert advisory groups as needed. By Day 90, applicants receive a consolidated request for information (“RFI”), which pauses the review clock until a complete response is submitted electronically. Responses are assessed by Day 150, with further RFIs issued for minor issues or a CHM letter for major objections. Each subsequent RFI requires a complete response within three months, and the clock is restarted upon submission. Applicants may make written or oral representations to the CHM if major objections remain. Final compliance checks are conducted once all issues are resolved, and the MHRA issues a grant or refusal letter specifying any conditions and the MA expiry date. The entire assessment process is designed to be completed within 210 calendar days, excluding any procedural clock-stops for additional information or representations. The innovative medicines timetable allows for a positive decision within 150 clock-on days if all issues are resolved following one round of questions. Where there are outstanding issues at Day 150, we will come to a final decision as soon as possible and within 210 clock-on days. The innovative medicines timetable allows for a positive decision within 150 clock-on days if all issues are resolved following one round of questions. Where there are outstanding issues at Day 150, we will come to a final decision as soon as possible and within 210 clock-on days.

In addition, the MHRA 150-day accelerated review is a specialized, fast-track national MA procedure designed for innovative medicines, new active substances, and biosimilars, aiming for a decision in 150 "clock-on" days rather than the standard 210. It requires high-quality applications, typically involving one round of questions and a 60-day cool-down period for responses.

On August 30, 2023, the MHRA published detailed guidance on its recently announced new International Recognition Procedure (“IRP”) for MAAs. The IRP applies from January 1, 2024, and replaces existing EU decision reliance procedure. to apply for authorizations from seven international regulators (e.g. Health Canada, Swiss Medic, FDA, EMA, among others). The IRP allows the MHRA to take into account the assessment and decision-making of the ‘Reference Regulators” to perform a targeted assessment of IRP applications but retain the authority to reject applications if the evidence provided is considered insufficiently robust. There exist two recognition timetables for new IRP MAAs: IRP Route A (60 days) and IRP Route B (110 days), both starting from validation. Eligibility is determined via an applicant-completed form six weeks before submission. Recognition A applies to applications with Reference Regulator approval within the past two years, with no clock stop, but may revert to Recognition B if major objections arise. IRP Route B covers Reference Regulator approvals within the past ten years (or exceptionally older) and applies if specific criteria, such as conditional approvals, manufacturing changes, or UK-specific requirements, are met. IRP Route B allows for consultation with the CHM and aligns with CHM dates for new active substances. Applications not eligible for either timetable may be submitted as full national applications if MHRA requirements are met. IRP can be used for post-authorization measures including line extensions, variations, and renewal application.

There will be no pre-MA orphan designation. Instead, the MHRA will review applications for orphan designation in parallel to the corresponding MA application. The criteria are essentially the same as the EU rules, but have been tailored for the market, i.e., the prevalence of the condition in GB, rather than the EU, must not be more than

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five in 10,000. Should an orphan designation be granted, the period or market exclusivity will be set from the date of first approval of the product in GB.

Rest of the World Regulation

For other countries outside of the EU and the United States, such as countries in Eastern Europe, Latin America, Asia or Japan, the requirements governing the conduct of clinical trials, product licensing, pricing and reimbursement vary from jurisdiction to jurisdiction. Additionally, the clinical trials must be conducted in accordance with GCP requirements and the applicable regulatory requirements and the ethical principles that have their origin in the Declaration of Helsinki.

If we fail to comply with applicable regulatory requirements, we may be subject to, among other things, fines, suspension or withdrawal of regulatory approvals, product recalls, seizure of products, operating restrictions and criminal prosecution.

Other Healthcare Laws

In the United States, activities of pharmaceutical manufacturers are subject to numerous other federal, state and local laws designed to, for example, prevent “fraud and abuse” in the delivery of and payment for healthcare; promote transparency in interactions with others in the healthcare industry; require reporting of drug prices and payment of rebates or offering of discounts to certain government programs and public and private payors; protect consumers; and regulate government payment for drugs. These laws are enforced by various federal and state enforcement authorities and non-compliance, or alleged non-compliance, with such laws could adversely affect our reputation, our business and our financial results. Similar laws exist in foreign jurisdictions, including the EU, as well.

We may be subject to various federal and state laws pertaining to health care “fraud and abuse,” including anti-kickback laws (which typically prohibit soliciting, offering, receiving or paying anything of value to generate healthcare business reimbursable by third party payors, including Medicare and Medicaid) and false claims laws (which generally prohibit anyone from knowingly and willingly presenting, or causing to be presented, any false or fraudulent claims for payment for reimbursed drugs or services to third party payors, including Medicare and Medicaid). Although the specific provisions of these laws vary, their scope is generally broad and there may not be regulations, guidance or court decisions that apply the laws to particular industry practices.

Laws and regulations have also been enacted by the federal government and various states to regulate the sales and marketing practices of pharmaceutical manufacturers, including laws that require manufacturers to adopt certain compliance standards; restrict interactions with healthcare professionals; disclose financial interactions with healthcare professionals to the government and public; report pricing information or marketing expenditures; or register sales representatives. Many of these laws and regulations contain ambiguous requirements or require administrative guidance for implementation. Given the lack of clarity in laws and their implementation, our activities could be subject to challenge.

We may need to obtain and maintain licenses for our manufacturing and distribution activities in the states in which we operate or distribute our products.

In the EU, many EU member states have adopted specific anti-gift statutes that further limit commercial practices for medicinal products, in particular vis-à-vis healthcare professionals and organizations. Additionally, there has been a recent trend of increased regulation of payments and transfers of value provided to healthcare professionals or entities and many EU member states have adopted national laws which impose requirements to disclose financial interactions with healthcare professionals to the government and public (often on an annual basis), similar to the requirements in the United States, on pharmaceutical companies. Certain countries also mandate implementation of commercial compliance programs or require disclosure of marketing expenditures and pricing information.

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Coverage, Pricing and Reimbursement

Significant uncertainty exists as to the coverage and reimbursement status of approved biological products. Governments around the world are exploring cost containment programs, including price controls, reimbursement restrictions and requirements for biosimilar substitution. In the United States and markets in other countries, patients rely on third party payors to reimburse healthcare costs. Third party payors include government authorities or health care programs, managed care plans, private health insurers and other organizations.

In the United States, the process for determining whether a third party payor will provide coverage and the related coverage criteria for a biological product typically is separate from the process for setting the price of such product or for establishing the level of reimbursement that the payor will pay for the product once coverage is approved. Third party payors may limit coverage or take other action to control utilization of covered products, including restricting coverage to specific products on an approved list, also known as a formulary, which might not include all of the FDA-approved products for a particular indication, or place products at certain formulary levels that result in lower reimbursement levels, which results in higher cost-sharing financial obligation imposed on patients. Additionally, coverage, coverage criteria and reimbursement for products can differ significantly from payor to payor. One third party payor’s decision to cover a particular biologic does not ensure that other payors will also provide coverage for the biologic or will provide coverage at an adequate reimbursement rate. As a result, the coverage determination process usually requires manufacturers to provide scientific, clinical and health economic support for the use of their products to each payor separately, which is a time-consuming process.

Third party payors are increasingly challenging the prices charged for medical products and services, examining the medical necessity and reviewing the cost-benefit of biopharmaceutical products, in addition to questioning safety and efficacy. If third party payors do not consider a product to offer a favorable cost-benefit compared to other available therapies, they may not cover that product after FDA approval or, if they do, the level of payment may not be sufficient to allow a manufacturer to sell its product at a profit.

In addition, in many countries, the proposed pricing for a drug must be approved before it may be lawfully marketed. The requirements governing drug pricing and reimbursement vary widely from country to country. In the EU, governments influence the price of products through their pricing and reimbursement rules and control of national healthcare systems that fund a large part of the cost of those products to consumers. Member states are free to restrict the range of pharmaceutical products for which their national health insurance systems provide reimbursement, and to control the prices and reimbursement levels of pharmaceutical products for human use. Some jurisdictions operate positive and negative list systems under which products may only be marketed once a reimbursement price has been agreed to by the government. Member states may approve a specific price or level of reimbursement for the pharmaceutical product, or alternatively adopt a system of direct or indirect controls on the profitability of the company responsible for placing the pharmaceutical product on the market, including volume-based arrangements, caps and reference pricing mechanisms. To obtain reimbursement or pricing approval, some of these countries may require the completion of clinical trials that compare the cost effectiveness of a particular product to currently available therapies. Other member states allow companies to fix their own prices for medicines but monitor and control company profits.

Government Programs and Price Reporting

We are subject to federal laws, including the Medicaid Drug Rebate Program (the “MDRP”), that require pharmaceutical manufacturers to report certain calculated product prices to the government or provide certain discounts or rebates to government authorities or private entities, often as a condition of reimbursement under government healthcare programs. Reporting requirements are complex and, in some instances, require reporting manufacturers to make reasonable assumptions in interpreting their obligations.

●Medicaid. Our products are eligible to be reimbursed by Medicaid. Medicaid is a joint federal and state program that is administered by the states for low-income and disabled beneficiaries. Under the MDRP, participating manufacturers are required to pay a rebate for each unit of product reimbursed under the state Medicaid programs. The amount of the rebate for each product is set by law and depends in part on the prices at which our products are sold to certain other purchasers and may be subject to an additional

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discount if certain pricing increases more than inflation. State Medicaid programs and Medicaid managed care plans can seek additional “supplemental” rebates from manufacturers.

●Medicare. Medicare is a federal program that is administered by the federal government that covers individuals age 65 and over, disabled individuals and certain other eligible individuals. Medicare Part B generally covers drugs that are usually administered by physicians or other clinicians. Medicare Part B pays for such drugs under a payment methodology based on the average sales price (“ASP”) of the drugs, with manufacturers reporting an ASP for their drug products. Reimbursement levels and reimbursement methodologies have come under scrutiny and may be subject to change. Medicare Part D provides coverage for self-administered drugs (i.e., drugs that do not need to be injected or otherwise administered by a physician). Medicare Part D is administered by private prescription drug plans approved by the United States government. Each drug plan establishes its own government-approved Medicare Part D formulary for prescription drug coverage and pricing, which the drug plan may modify from time-to-time. The prescription drug plans negotiate rebates with manufacturers and may condition formulary placement on the availability of manufacturer discounts. Manufacturers with marketed brand name drugs and biologics are required to provide discounts on such drugs and biologics utilized by Medicare Part D beneficiaries, under a manufacturer discount program. Additionally, as the result of recent changes under the Inflation Reduction Act of 2022 (“IRA”), drug utilization under Medicare Part B and Part D may be subject to an additional Medicare discount if the pricing increases more than inflation.

●Federal Purchasers. Drug products are subject to discounted pricing when purchased by federal agencies via the Federal Supply Schedule (“FSS”). FSS participation is required for a drug to be covered and reimbursed by certain federal agencies and for coverage of any manufacturer drug products under the MDRP and Medicare Part B. FSS pricing is subject to statutory reporting requirements and also is negotiated periodically with the Department of Veterans Affairs, including by reference to a manufacturer’s comparable non-federal customer pricing. By statute, prices for drugs purchased by the Veterans Administration, Department of Defense (including drugs purchased by military personnel and dependents through the TRICARE retail pharmacy program), Coast Guard and the Public Health Service (“PHS”) are subject to a cap on pricing (known as the “federal ceiling price”) and may be subject to an additional discount if pricing increases more than the rate of inflation.

●PHS 340B Drug Pricing Program. To obtain coverage of drugs under the MDRP and Medicare Part B, manufacturers are required to extend discounts to certain purchasers under the PHS 340B drug pricing program. Purchasers eligible for 340B discounts include hospitals that serve a disproportionate share of financially needy patients, community health clinics and other entities that receive certain health services grants from the PHS.

Additionally, several states have either implemented or are considering implementing drug price transparency legislation. Requirements under such laws include advance notice of planned price increases, reporting price increase amounts and factors considered in taking such increases, wholesale acquisition cost information disclosure to prescribers, purchasers and state agencies, and new product notice and reporting. A number of states may impose civil monetary penalties or pursue other enforcement mechanisms against manufacturers who fail to comply with drug price transparency requirements. Certain other state legislation focuses on limiting the price or payment for certain drugs.

Healthcare Reform and Potential Changes to Healthcare Laws

Within the United States, federal and state governments have been active in proposing and implementing health care reform. Drug pricing and payment reform has been an ongoing focus for reform. Recent examples include federal legislation that eliminated a statutory cap on Medicaid drug rebate program rebates effective January 1, 2024. As another example, the IRA of 2022 includes a number of changes intended to address rising prescription drug prices in Medicare Parts B and D, with varying implementation dates. These changes include caps on Medicare Part D out-of-pocket costs, Medicare Part B and Part D drug price inflation rebates, a new Medicare Part D manufacturer discount drug program (replacing the prior Medicare Part D coverage gap discount program) and a drug price negotiation program for certain

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high spend Medicare Part B and D drugs (with the first set of negotiated Medicare maximum fair prices going into effect in 2026). The IRA has had a significant impact on the pharmaceutical industry and that impact is anticipated to continue.

Beyond the IRA, changes to Medicaid effective in 2024 eliminated the Medicaid rebate cap and changes to certain Medicare price reporting requirements for drugs beginning in 2026 will likely increase the administrative and compliance burden for manufacturers. In addition, recent legislation expanded the orphan drug exclusion in the IRA Medicare drug price negotiation program.

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

Other healthcare reform efforts or actions may affect access to healthcare coverage or the funding of health care benefits, although the full impact of such efforts or actions cannot be predicted. For example, the Congressional Budget Office has estimated that Medicaid provisions in the 2025 budget reconciliation legislation, including restrictions in eligibility and funding for Medicaid, as well as changes to the healthcare marketplace such as the elimination of certain subsidies, will increase the number of uninsured patients.

Additionally, there has been increasing legislative and enforcement interest in the United States with respect to specialty drug pricing practices. Specifically, there have been several recent Congressional inquiries and proposed and enacted federal and state legislation designed to, among other things, bring more transparency to drug and biologic pricing, reduce the cost of prescription drugs and biologics under Medicare, review the relationship between pricing and manufacturer patient programs and reform government program reimbursement methodologies for drugs and biologics.

Individual states in the United States have also become increasingly active in passing legislation and implementing regulations designed to control pharmaceutical product pricing, including price constraints, restrictions on copayment assistance by pharmaceutical manufacturers, value-based pricing, marketing cost disclosure and other transparency measures, and, in some cases, measures designed to encourage importation from other countries and bulk purchasing.

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

Other government actions could have an adverse effect upon, and could prevent, our products’ commercial success. For example, the current presidential administration’s announced tariff on branded or patented drugs may increase the cost of drug products that are imported from abroad or manufactured using products or materials imported from abroad. The timeline for implementation of this tariff has not yet been finalized. As another example, the Budget Control Act of 2011, as amended, resulted in the imposition of reductions in Medicare (but not Medicaid) payments to

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providers in 2013 and remains in effect through 2032 unless additional Congressional action is taken. Any significant spending reductions affecting Medicare, Medicaid or other publicly funded or subsidized health programs that may be implemented and/or any significant taxes or fees that may be imposed on us could have an adverse impact on our results of operations.

Outside the United States, there are also reform efforts. In December 2021, the EU adopted Regulation No 2021/2282 on Health Technology Assessment (the “HTA”). While the HTA entered into force in January 2022, it only became applicable to apply from January 2025 and will have a phased implementation depending on the concerned products. The HTA intends to boost cooperation among EU member states in assessing health technologies, including new medicinal products, and providing the basis for cooperation at the EU level for joint clinical assessments in these areas. The HTA permits EU member states to use common HTA tools, methodologies and procedures across the EU, working together in four main areas, including joint clinical assessment of the innovative health technologies with the most potential impact for patients, joint scientific consultations whereby developers can seek advice from HTA authorities, identification of emerging health technologies to identify promising technologies early and continuing voluntary cooperation in other areas. Individual EU member states will continue to be responsible for assessing non-clinical (e.g., economic, social, ethical) aspects of health technology and making decisions on pricing and reimbursement.

In April 2023, the Commission published its long-awaited proposals to revise the EU’s pharmaceutical legislation. The proposals seek to balance supporting innovation and increasing affordability and availability of medicines. The most controversial proposal is the shortening of regulatory protection periods to six (6) years of data exclusivity and two (2) years of market exclusivity (rather than the current eight (8) years data exclusivity and two (2) years market exclusivity). Other proposals include: (i) a transferable data exclusivity voucher for ‘priority antimicrobials’ entitling the holder to an additional one year data protection for any other centrally approved product (provided this is used within the first four years of data protection for that product) in an effort to encourage the development of new antimicrobials capable of combating antimicrobial resistance; (ii) greater flexibility for hospital pharmacies to prepare product for dispensing products in response to individual prescriptions; (iii) compulsory licenses for public health emergencies which would lead to suspension of data and market exclusivities while the compulsory license is in place; (iv) further transparency and disclosure requirements; (v) requirements for MAA to include an environmental risk assessment for the product; and (vi) streamlining regulatory procedures, reducing approval timeline by over 50 days for centrally authorized products. On December 11, 2025, the European Council (consisting of the EU member states) and the European Parliament reached an agreement on the final shape of the new rules. The agreed text now awaits formal adoption by both the Parliament and Council, after which it will be published in the Official Journal of the EU. The new Directive and Regulation will then enter into force following a transition period of 18 to 36 months, ultimately modernizing EU pharmaceutical law to better support innovation, access, and supply. The agreed framework provides among other things that new medicines benefit from eight years of data protection and one year of market protection, with possible extensions for addressing unmet medical needs or additional indications, up to a maximum of 11 years. Developers of new antibiotics may receive transferable vouchers for extra market protection, and orphan medicines can receive up to 11 years of combined protection, along with early regulatory guidance. In addition, the European Commission proposed in December 2025 the Biotech Act which seeks to strengthen the competitiveness of the biotechnology sector and facilitate the development and timely market entry of biotechnology innovations, while ensuring high standards for the protection of human health.

Other Regulations

In additional to the regulations and laws described above, our business is subject to a number of other regulations that apply broadly to companies doing business in the healthcare space, including the following:

●the United States federal Anti-Kickback Statute, which prohibits, among other things, persons from knowingly and willfully soliciting, offering, receiving or providing remuneration, directly or indirectly, in cash or in kind, to induce or reward either the referral of an individual for, or the purchase, order or recommendation of, any good or service, for which payment may be made under federal and state healthcare programs such as Medicare and Medicaid. A person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation;

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●the United States federal False Claims Act and civil monetary penalties laws, which, among other things, impose criminal and civil penalties, including through civil whistleblower or qui tam actions, against individuals or entities for knowingly presenting, or causing to be presented, to the federal government, claims for payment that are false or fraudulent or making a false statement to avoid, decrease or conceal an obligation to pay money to the federal government. Pharmaceutical manufacturers can be held liable under the False Claims Act even when they do not submit claims directly to government payors if they are deemed to “cause” the submission of false or fraudulent claims. Moreover, a claim including items and services resulting from a violation of the federal Anti-Kickback Statute is deemed a false or fraudulent claim for purposes of the False Claims Act;

●the United States Foreign Corrupt Practices Act (the “FCPA”), the U.K. Bribery Act 2010 (the “Bribery Act”) and similar anti-bribery or anti-corruption laws, regulations or rules in other countries in which we operate, which prohibit companies and their representatives from paying, offering to pay, promising to pay or authorizing the payment of anything of value to any foreign government official, government staff member, political party or political candidate for the purpose of obtaining or retaining business or to otherwise obtain favorable treatment or influence a person working in an official capacity abroad. The Bribery Act may also create liability where we fail to prevent a person associated with us from committing a bribery offense. In many countries, the healthcare professionals we interact with may meet the FCPA’s and Bribery Act’s definition of a foreign government official. The FCPA also requires public companies to make and keep books and records that accurately and fairly reflect their transactions and to devise and maintain an adequate system of internal accounting controls;

●the United States federal Health Insurance Portability and Accountability Act, as amended (“HIPAA”), which imposes criminal and civil liability for executing a scheme to defraud any healthcare benefit program or obtain, by means of false or fraudulent pretenses, representations or promises, any of the money or property owned by, or under the custody or control of, any healthcare benefit program, regardless of the payor (e.g., public or private) and knowingly and willfully falsifying, concealing or covering up a material fact or making any materially false statement in connection with the delivery of or payment for healthcare benefits, items or services. Similar to the federal Anti-Kickback Statute, a person or entity does not need to have actual knowledge of the statute or specific intent to violate it in order to have committed a violation;

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

●the United States federal physician payment transparency requirements, sometimes referred to as the “Sunshine Act”, which requires manufacturers of drugs, devices, biologics and medical supplies that are reimbursable under Medicare, Medicaid or the Children’s Health Insurance Program to report to the Department of Health and Human Services information related to certain financial interactions with physicians (defined to include medical doctors, dentists, optometrists, podiatrists and chiropractors), certain non-physician practitioners (including physician assistants and nurse practitioners) and teaching hospitals, as well as the ownership and investment interests of physicians and their immediate family members;

●United States federal consumer protection and unfair competition laws, which broadly regulate marketplace activities and activities that potentially harm consumers;

●United States federal, state and local laws, and similar foreign laws, regulations and standards governing the collection, use, access to, confidentiality and security of health-related and other personal information;

●analogous United States state laws and regulations, such as state anti-kickback and false claims laws that may apply to sales or marketing arrangements and claims involving healthcare items or services reimbursed by nongovernmental third party payors, including private insurers; and state laws that require

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pharmaceutical companies to adopt certain compliance standards; restrict interactions with healthcare professionals; disclose financial interactions with healthcare professionals to the government and public; report pricing information or marketing expenditures; or register sales representatives; and

●similar healthcare laws and regulations in the EU, United Kingdom and other jurisdictions, including: Directive 2001/83/EC on the Community code relating to medicinal products for human use and its national implementing legislation; the UK Human Medicines Regulations 2012; Directive 2011/83/EU on consumer rights and its national implementing legislation; and reporting requirements detailing interactions with and payments to healthcare professionals, which may be applicable even if we are not commercializing a product in such jurisdictions.

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Human Capital

We aim to cultivate a highly-skilled and passionate team determined to deliver transformative therapies to the patients who need them most. As of December 31, 2025, we had 366 full-time employees, of which 351 were located within the United States and 15 were located outside of the United States.

We believe that the success and growth of our business depends in large part on our continued ability to attract, retain and motivate qualified personnel at all levels of our company.

Competitive Pay and Benefits. We provide our employees with competitive base salaries, cash bonus opportunities designed to incentivize achievement of our corporate goals, equity awards and opportunities for equity ownership through our employee share purchase plan and a robust benefit package designed to promote well-being across different aspects of our employees’ lives, including comprehensive health insurance, dental and vision plans, life and other employment related insurance, retirement planning through a 401(k) plan with partial company match and paid time off.

Ethics in the Workplace. Overall, we believe that our commitment to compliance, quality and ethics throughout our business makes us a stronger and more competitive organization. We believe this attracts and retains the highest caliber of executives and employees who deliver for our patients and execute on our corporate strategy. Each employee of our company is required to confirm in writing that they understand and will comply with our policies, including but not limited to our Code of Business Conduct and Ethics, anti-harassment policy, our insider trading and compliance policy, our policies against bribery and corruption and our policies regarding interactions with healthcare professionals. Further, we believe our company benefits from a broad range of experiences and viewpoints that enable innovative approaches to our business and operations. We foster a culture where employees put compliance first and speak up on important ethical issues. Employees are required to participate in periodic and as-needed trainings to refresh their understanding of our policies and to provide additional training for new issues as and when they arise. For the clinical and manufacturing activities that we perform and oversee, we adhere to operating within the accepted GLP, GCP, cGMP and other similar regulatory guidelines.

Health and Safety. Health and safety principles are firmly rooted across our company through the integration of health and safety processes throughout our business and risk management. To foster a safe and healthy culture, we have implemented a comprehensive safety program and emergency response plan to ensure that we understand and mitigate health and safety incidents. As part of our employee health and safety program, we have a number of safety policies that employees are required to train on, conduct periodic on-site safety drills at our offices and perform periodic internal and external safety audits.

Our Corporate Information

We were initially incorporated under the laws of Bermuda in July 2015 and, in June 2024, subsequently announced the completion of the change of place of incorporation of our principal holding company from Bermuda to the United Kingdom (the “Redomiciliation”), pursuant to a scheme of arrangement approved by both the Bermuda Supreme Court and our shareholders, which caused the shareholders of our former parent company, Kiniksa Pharmaceuticals, Ltd., to become the shareholders of our current parent company, Kiniksa Pharmaceuticals International, plc.

Our registered office is located at 105 Piccadilly, Second Floor, London, W1J 7NJ, England, United Kingdom. Our executive offices are located at 100 Hayden Avenue, Lexington, Massachusetts, 02421. The telephone number for our offices is +1 (781) 431-9100. Our website address is www.kiniksa.com. The information contained on our website is not incorporated by reference into this Annual Report, and you should not consider any information contained on, or that can be accessed through, our website as part of this Annual Report.

As used herein, and unless the context otherwise requires, references to “we,” “us,” “our” and similar words or phrases prior to the Redomiciliation shall refer to Kiniksa Pharmaceuticals, Ltd. and from and after the Redomiciliation, to Kiniksa Pharmaceuticals International, plc. In addition, references to “ordinary shares” prior to the Redomiciliation

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are to Kiniksa Pharmaceuticals, Ltd.’s common shares and from and after the Redomiciliation are to Kiniksa Pharmaceuticals International, plc’s ordinary shares.

Where You Can Find More Information

We are subject to the information requirements of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). The SEC maintains an internet site that contains reports, proxy and information statements and other information regarding issuers that file electronically, such as ourselves, with the SEC at http://www.sec.gov.

We make available free of charge on our website our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports filed or furnished pursuant to Section 13(a) or 15(d) of the Exchange Act as soon as reasonably possible after we electronically file such material with, or furnish it to, the SEC. Our website is located at www.kiniksa.com. The reference to our or the SEC’s website address does not constitute incorporation by reference of the information contained at or available through such websites, and you should not consider it to be a part of this Annual Report.

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Item 1A.Risk Factors.

You should carefully consider the risks described below, as well as the other information in this Annual Report, including our audited consolidated financial statements and the related notes and “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” The occurrence of any of the events or developments described below could adversely affect our business, financial condition, results of operations and growth prospects. In such an event, the market price of our Class A ordinary shares could decline. Additional risks and uncertainties not presently known to us or that we currently deem immaterial also may impair our business operations.

Risks Related to Commercialization

We may not be able to continue to commercialize ARCALYST or be successful in commercializing any future products, potentially impairing the commercial potential for our current and future products to generate any revenue.

Since our commercial launch of ARCALYST, we have focused on establishing and expanding our sales, marketing, distribution, access and payor and patient support services capabilities as well as contracting with third parties to perform certain services. Each aspect of commercialization on its own can be complex, expensive and time consuming, and, collectively, the required effort for coordination is intensive. While we have realized revenues from such efforts, there is no guarantee that we will be able to maintain the trajectory of growth or significant and sustained revenues in the future.

In addition, our continued commercialization of ARCALYST or successful commercialization of any of our current or future product candidates, if approved, could be materially adversely impacted by a number of foreseen and unforeseen factors, including:

●any delays in our ability to produce sufficient quantities of ARCALYST, or any of our future products, at an acceptable cost or quality, including delays arising out of quality assurance concerns or changes in regulatory guidance, or those caused by our reliance on our third party manufacturers;

●our inability to recruit, train and retain adequate numbers of effective sales, marketing, access and payor and patient support personnel;

●the inability of sales personnel to obtain access to prescribers and accounts;

●an inadequate number of prescribers or accounts prescribing our current and future products;

●the lack of complementary products to be supported by sales personnel, which may put us at a competitive disadvantage relative to companies with more extensive product lines;

●our inability to equip customer-facing personnel with effective materials, including medical and sales literature to help them educate physicians and other healthcare professionals regarding applicable diseases relevant to ARCALYST or any of our future products;

●an absence or reduction in strong scientific-based relationships to drive disease awareness and education;

●our inability to establish the unmet medical need for a given disease;

●our inability to provide acceptable evidence of safety and efficacy;

●the prevalence and severity of side effects associated with any future product;

●our inability to compete with current or future competitor products and/or biosimilars;

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●the convenience and ease of administration of our products relative to alternative therapies, if any;

●alternative therapies that use the same or different mechanism of action for treating patients with recurrent pericarditis or other indications that our future products may treat;

●our inability or delay in gaining or maintaining reimbursement and broad patient access at a price that reflects the value of ARCALYST or any of our future products;

●limitations on the content or form of the consumer and/or prescriber-facing marketing materials that we may use;

●any delays in the ongoing technology transfer of the process for manufacturing ARCALYST drug substance;

●our inability to provide prescribers and patients adequate support and training to build comfort around the preparation and administration process to initiate and continue to use ARCALYST or any of our future products;

●our inability to develop or sustain robust patient support programs to optimize the patient and customer experience with ARCALYST or any of our future products;

KNSA US Equity

KNSA · 10-K · period ended 2025-12-31

ITEM 1.BUSINESS.

Item 1A.Risk Factors.

KNSA US Equity☆

KNSA · 10-K · period ended 2025-12-31

ITEM 1.BUSINESS.

Item 1A.Risk Factors.

KNSA US Equity