Kiniksa Pharmaceuticals International, plc

1. Nature of the Business and Basis of Presentation

Kiniksa Pharmaceuticals International, plc (the “Company” or “Kiniksa International”) is a biopharmaceutical company developing and commercializing novel therapies for diseases with unmet medical need, with a focus on cardiovascular indications. The Company’s portfolio of immune-modulating assets is based on strong biologic rationale or validated mechanisms, targets a spectrum of underserved cardiovascular and autoimmune conditions and offers the potential for differentiation.

The Company is the successor issuer to Kiniksa Pharmaceuticals, Ltd. (“Kiniksa Bermuda”). On June 27, 2024, the Company and Kiniksa Bermuda completed a transaction pursuant to a Bermuda court-approved scheme of arrangement (the “Scheme”), which had been previously approved by Kiniksa Bermuda’s shareholders. Pursuant to the Scheme, the shareholders of Kiniksa Bermuda became the shareholders of the Company and the Company became the ultimate parent and holding company of the Kiniksa organization, thereby effecting a change of incorporation from Bermuda to the United Kingdom (the “UK) (the “Redomiciliation”). As used herein, and unless the context otherwise requires, references to the “Company” prior to the Redomiciliation shall refer to Kiniksa Bermuda and from and after the Redomiciliation, to Kiniksa International. In addition, references to “ordinary shares” prior to the Redomiciliation are to Kiniksa Bermuda’s common shares and from and after the Redomiciliation are to Kiniksa International’s ordinary shares.

The Company is subject to risks common to companies in the biopharmaceuticals industry including, but not limited to, commercialization of existing and new products, conducting clinical research and development, its current and future products and product candidates, risks from existing or new competition, protection of proprietary intellectual and other technology and compliance with United States and foreign regulations and approval requirements.

Principles of Consolidation

The Redomiciliation was accounted for as a change in the reporting entity between entities under common control and the historical basis of accounting was retained as if the entities had always been combined for financial reporting purposes. The consolidated financial statements for periods prior to the Redomiciliation are the consolidated statements of Kiniksa Bermuda as the predecessor to the Company for accounting and reporting purposes and, upon completion of the Redomiciliation, such historical consolidated financial statements became Kiniksa International’s historical consolidated financial statements.

The accompanying consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”) and include the accounts of the Company and its wholly owned subsidiaries, Kiniksa Pharmaceuticals Corp. (“Kiniksa US”), Kiniksa Bermuda and Kiniksa Pharmaceuticals (UK), Ltd. (“Kiniksa UK”) as well as the subsidiary of Kiniksa US, Primatope Therapeutics, Inc. (“Primatope”) and subsidiaries of Kiniksa UK, Kiniksa Pharmaceuticals (Germany) GmbH (“Kiniksa Germany”), Kiniksa Pharmaceuticals (France) SARL (“Kiniksa France”), and Kiniksa Pharmaceuticals, GmbH (“Kiniksa Switzerland”), after elimination of all significant intercompany accounts and transactions. Where the Kiniksa Pharmaceuticals International, plc entity is referred to in its single, unconsolidated form, it is referred to as “Kiniksa International”.

Use of Estimates

The preparation of the Company’s consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the consolidated financial statements and the reported amounts of expenses during the reporting period. Significant estimates and assumptions reflected in these consolidated financial statements include, but are not limited to, the recognition of revenue, the accrual for research and development expenses, and the valuation of the Company’s deferred tax assets. Estimates are periodically reviewed in light of changes in circumstances, facts and experience. Changes in estimates are recorded in the period in which they become known. Actual results could differ from those estimates.

Unaudited Interim Consolidated Financial Information

The accompanying unaudited consolidated financial statements have been prepared in accordance with GAAP for interim financial information. The accompanying unaudited consolidated financial statements do not include all of the information and footnotes required by GAAP for complete consolidated financial statements. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company’s audited consolidated financial statements and the accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2024 (the “2024 Form 10-K”). The Company’s accounting policies are described in the Notes to Consolidated Financial Statements included in the Company’s 2024 Form 10-K and updated, as necessary, in this report. The accompanying year-end consolidated balance sheet was derived from audited financial statements but does not include all disclosures required by GAAP. The unaudited interim consolidated financial statements have been prepared on the same basis as the audited annual consolidated financial statements and, in the opinion of management, reflect all adjustments, which include only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of June 30, 2025 and the results of its operations for the three and six months ended June 30, 2025 and 2024, the changes in its shareholders’ equity for the three and six months ended June 30, 2025 and 2024 and its cash flows for the six months ended June 30, 2025 and 2024. The results for the three and six months ended June 30, 2025 are not necessarily indicative of results to be expected for the year ending December 31, 2025, any other interim periods or any future year or period.

Liquidity

The Company has evaluated whether there are conditions and events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the consolidated financial statements are issued. As of June 30, 2025, the Company had an accumulated deficit of $494,772. During the six months ended June 30, 2025, the Company reported a net income of $26,371 and had cash provided from operating activities of $50,414. As of June 30, 2025, the Company had cash, cash equivalents and short-term investments of $307,782. Based on its current operating plan, the Company expects that its cash, cash equivalents and short-term investments will be sufficient to fund its operations and capital expenditure requirements for at least twelve months from the issuance date of these consolidated financial statements.

Recently Issued Accounting Pronouncements

In December 2023, the Financing Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2023-09,Income Taxes (Topic 740): Improvements to Income Tax Disclosures. The amendments require (i) enhanced disclosures in connection with an entity's effective tax rate reconciliation and (ii) income taxes paid disaggregated by jurisdiction. The amendments are effective for annual periods beginning after December 15, 2024. The Company does not expect the adoption of the amendments to have a material impact on its financial statements.

In November 2024, the FASB issued ASU 2024-03,Income Statement-Reporting Comprehensive Income-Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, requiring public entities to disclose additional information about specific expense categories in the notes to the financial statements on an interim and annual basis. ASU 2024-03 is effective for fiscal years beginning after December 15, 2026, and for interim periods beginning after December 15, 2027, with early adoption permitted. The Company is currently evaluating the impact of adopting ASU 2024-03.

2. Fair Value of Financial Assets and Liabilities

Financial assets and liabilities carried at fair value are to be classified and disclosed in one of the following three levels of the fair value hierarchy, of which the first two are considered observable and the last is considered unobservable:

The following tables present information about the Company’s financial instruments measured at fair value on a recurring basis and indicate the level of the fair value hierarchy used to determine such fair values:

During the six months ended June 30, 2025 and the year ended December 31, 2024, there wereno transfers between Level 1, Level 2 and Level 3. The money market funds were valued using quoted prices in active markets, which represent a Level 1 measurement in the fair value hierarchy. The Company’s cash equivalents and short-term investments as of June 30, 2025 and December 31, 2024 included U.S. Treasury notes, which are not traded on a daily basis and, therefore, represent a Level 2 measurement in the fair value hierarchy at each period end.

As of June 30, 2025, the Company considers the unrealized losses in its investment portfolio to be temporary in nature and not due to credit losses. The Company has the ability to hold such investments until recovery of the fair value. The Company utilizes the specific identification method in computing realized gains and losses. The Company

hadno realized gains and losses on its available-for-sale securities for the three and six months ended June 30, 2025 or 2024.

3. Product Revenue, Net

The Company derives substantially all of its product revenue, net from sales of ARCALYST in the United States, which was as follows:

The following table summarizes balances and activity in each of the product revenue allowance and reserve categories for the six months ended June 30, 2025:

Total revenue-related reserves as of June 30, 2025 and December 31, 2024, included in the Company’s consolidated balance sheets, are summarized as follows:

Primarily all of the Company’s trade accounts receivable arise from product revenue in the United States due from the Company’s third party logistics provider.

4. Inventory

Inventory consisted of the following:

As of June 30, 2025, $18,386 of semi-finished goods were associated with the Company’s technology transfer of ARCALYST manufacturing to a new facility, which is pending regulatory approval. The Company believes it is probable that regulatory approval will be obtained, and all such inventory will be available for commercial distribution in the future.

5. Property and Equipment, Net

Property and equipment, net consisted of the following:

Depreciation expense was $13 and $119 during the three months ended June 30, 2025 and 2024, respectively, and $48 and $273 during the six months ended June 30, 2025 and 2024, respectively.

6. Intangible Assets

Intangible assets, net of accumulated amortization as of June 30, 2025 and December 31, 2024 are summarized in the following table.

Amortization expense was $250 during the three months ended June 30, 2025 and 2024 and $500 during the six months ended June 30, 2025 and 2024.

7. Accrued Expenses

Accrued expenses consisted of the following:

8. Share-Based Compensation

As part of the Redomiciliation, Kiniksa International assumed the sponsorship of, and all rights and obligations of Kiniksa Bermuda under Kiniksa Bermuda’s equity compensation plans, which include the 2018 Incentive Award Plan (the “2018 Plan”) and the 2018 Employee Share Purchase Plan (the “2018 ESPP”). Upon the effectiveness of the 2018 Plan, the Company ceased granting awards under its 2015 Equity Incentive Plan (as amended, the “2015 Plan” and together with the 2018 Plan, the “Plans”).

2015 Plan

As of June 30, 2025, there were 1,126,908 Class A ordinary shares reserved for issuance pursuant to outstanding awards under the 2015 Plan that were granted prior to the effectiveness of the 2018 Plan.

2018 Plan

The 2018 Plan provides for the grant of incentive share options, nonqualified share options, share appreciation rights, restricted shares, dividend equivalents, restricted share units (“RSUs”), PSUs (as defined below) and other share- or cash- based awards. Pursuant to the 2018 Plan’s evergreen provision, the number of shares available for future issuance under the 2018 Plan, as of January 1, 2025, increased by 2,900,642 Class A ordinary shares. As of June 30, 2025,6,132,156 shares remained available for future grant under the 2018 Plan.

2018 ESPP

In December 2024, the Company’s board of directors approved an increase, as of January 1, 2025, of 90,000 Class A ordinary shares under the 2018 ESPP. As of June 30, 2025,724,213 Class A ordinary shares were available for future issuance under the 2018 ESPP.

Restricted Share Units

The Company grants RSUs with service conditions to eligible employees as part of its equity incentive compensation. Such RSUs vest 25% on each of the first, second, third and fourth anniversaries of the date of grant, subject to continued employment through such dates.

Market and Performance-Based Share Units

In the second quarter of 2024, the Company began periodically granting performance-based restricted share units to certain employees under the 2018 Plan that are earned based upon (i) the achievement of certain specified ARCALYST revenue targets (“Revenue PSUs”) and (ii) the Company’s total shareholder return (“TSR”) relative to the TSR of each member of a specified peer group (“TSR PSUs”). The TSR PSUs and Revenue PSUs are subject to athree-year service period.

In addition, the Company from time-to-time grants performance-based restricted share units to certain eligible employees pursuant to 2018 Plan that are earned based upon certain development and regulatory milestones (“Development PSUs” and, together with the Revenue PSUs and TSR PSUs, “PSUs”). The Company’s currently outstanding Development PSUs are subject to earnout percentages based upon the date of applicable milestone achievement.

Performance Share Options

Beginning in the second quarter of 2025, the Company began granting performance share options (“PSOs”) to certain eligible employees pursuant to the 2018 Plan representing the right to purchase shares of the Company’s Class A ordinary shares. Such PSOs vest, if at all, upon the achievement of certain specified development and regulatory milestones and are subject to earnout percentages based upon the date of applicable milestone achievement.

The following table summarizes RSU and PSU activity for the six months ended June 30, 2025:

The following table summarizes share option and PSO activity for the six months ended June 30, 2025:

As of June 30, 2025, total unrecognized compensation cost related to RSUs, Revenue PSUs, TSR PSUs, and share options was $82,058 which is expected to be recognized over a weighted average remaining period of 2.50 years. As of June 30, 2025, total unrecognized compensation cost related to outstanding Development PSUs and PSOs was $10,874 which will be recognized when the applicable milestones are deemed probable of achievement through the date the awards vests with a cumulative catch-up.

Share-Based Compensation

Share-based compensation expense was classified in the consolidated statements of operations and comprehensive loss as follows:

9. Out-Licensing Agreements

Genentech License Agreement

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

Under the Genentech License Agreement, the Company received an upfront payment of $80,000 for the license. During the year ended December 31, 2023, the Company received cash payments of $20,000 following delivery of certain drug supplies to Genentech and $15,000 following Genentech’s achievement of a development milestone related to a new indication under the Genentech License Agreement. In the fourth quarter of 2023, following the achievement of a development milestone related to a second indication under the Genentech License Agreement, Genentech became obligated to make an additional cash payment of $10,000 which the Company received in the first quarter of 2024. In the second quarter of 2024, the Company received a cash payment of $5,000 following the achievement of a development milestone related to the third indication under the Genentech License Agreement. Under the terms of the Genentech License Agreement, the Company is eligible to receive a total of approximately $600,000 in contingent payments, including specified development, regulatory and sales-based milestones, before fulfilling the Company’s upstream financial obligations, of which approximately $570,000 remained as of June 30, 2025. The Company 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 the Company’s 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.

Pursuant and subject to the terms of the Genentech License Agreement, Genentech has the exclusive worldwide right to conduct development and commercialization activities for Genentech Licensed Products at its sole cost. In 2024, the Company fulfilled its responsibility under the Genentech License Agreement with respect to completing its Phase 2b clinical trial assessing the efficacy, safety and tolerability of vixarelimab in reducing pruritis in prurigo nodularis.

Accounting for the Genentech License Agreement

As of the Genentech Effective Date, the Company identified the following performance obligations in the Genentech License Agreement: (i) the delivery of the exclusive license for vixarelimab; (ii) an initial drug supply delivery; (iii) a drug product resupply delivery; and (iv) completion of the Phase 2b clinical trial for vixarelimab.

The Company determined the transaction price of the Genentech License Agreement consisted of the $80,000 upfront payment and the $20,000 variable consideration related to the delivery of the initial drug supply and drug product resupply which was added to the transaction price in 2022. In 2023 and 2024, the Company added $25,000 and $5,000, respectively, to the transaction price following Genentech’s achievement of development milestones under the Genentech License Agreement.

As noted above, the Company identified four performance obligations in the Genentech License Agreement: (i) the delivery of the exclusive license for vixarelimab; (ii) an initial drug supply delivery; (iii) a drug product resupply delivery; and (iv) completion of the Phase 2b clinical trial for vixarelimab. The selling price of each performance obligation in the Genentech License Agreement was determined based on the Company’s standalone selling price with the objective of determining the price at which it would sell such an item if it were to be sold regularly on a standalone basis. The Company allocated the transaction price to each of thefour performance obligations noted above.

The Company didnot recognize any collaboration revenue under the Genentech License Agreement during the three and six months ended June 30, 2025. The Company recognized $5,156 and $5,261 of collaboration revenue under the Genentech License Agreement during the three and six months ended June 30, 2024, respectively. As a result of the $5,000 development milestone the Company recognized revenue of $4,994 and $4,989 during the three and six months ended June 30, 2024, respectively, related to performance obligations satisfied in prior periods. As of June 30, 2025, the Company has recognized as revenue all of the transaction price associated with the Genentech License Agreement.

Huadong Collaboration Agreements

In February 2022 (the “Effective Date”), the Company entered intotwo collaboration and license agreements (each, a “Huadong Collaboration Agreement” and together, the “Huadong Collaboration Agreements”) with Hangzhou Zhongmei Huadong Pharmaceutical Co., Ltd. (“Huadong”), pursuant to which the Company granted Huadong exclusive rights to develop and commercialize ARCALYST and develop, manufacture and commercialize mavrilimumabin the following countries: People’s Republic of China, Hong Kong SAR, Macao SAR, Taiwan Region, South Korea, Indonesia, Singapore, The Philippines, Thailand, Australia, Bangladesh, Bhutan, Brunei, Burma, Cambodia, India, Laos, Malaysia, Maldives, Mongolia, Nepal, New Zealand, Sri Lanka, and Vietnam (collectively, the “Huadong Territory”). The Company otherwise retained its current rights to ARCALYST and mavrilimumab outside the Huadong Territory.

In April 2025, the Company and Huadong entered into a mutual termination agreement pursuant to which the parties agreed to terminate the mavrilimumab Huadong Collaboration Agreement and release all claims related thereto.

Under the Huadong Collaboration Agreements, the Company received a total upfront cash payment of $22,000, which included $12,000 for the Huadong Territory license of ARCALYST and $10,000 for the Huadong Territory license of mavrilimumab. In 2024, following the achievement of a regulatory milestone under the ARCALYST Huadong Collaboration Agreement, Huadong became obligated to make an additional cash payment of $20,000 to the Company which the Company received in the first quarter of 2025. The Company will be eligible to receive up to approximately $50,000 in contingent sales-based milestone payments for ARCALYST, all of which remain outstanding as of June 30, 2025. Due to its termination, the Company does not expect to receive any future payments under the mavrilimumab Huadong Collaboration Agreement. The Company was previously eligible to receive up to approximately

$576,000 in payments for mavrilimumab, including specified development, regulatory and sales-based milestones. Huadong was also obligated to pay the Company tiered percentage royalties ranging from the mid-teens to low twenties on annual net sales of mavrilimumab in the Huadong Territory. Huadong will also be obligated to pay the Company 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 the Company’s 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.

The Company concluded that the Huadong Collaboration Agreements should not be combined and treated as a single arrangement for accounting purposes as the Huadong Collaboration Agreements were negotiated separately with separate and distinct commercial objectives, the amount of consideration in one Huadong Collaboration Agreement is not dependent on the price or performance of the other Huadong Collaboration Agreement, and the goods and services promised in the Huadong Collaboration Agreements are not a single performance obligation.

Accounting for the Mavrilimumab Huadong Collaboration Agreement

As of the Effective Date, the Company identified the following performance obligations in the mavrilimumab Huadong Collaboration Agreement: delivery of (i) exclusive license for mavrilimumab in the Huadong Territory and (ii) clinical manufacturing supply of certain materials for mavrilimumab products in the Huadong Territory.

The Company determined the transaction price at the inception of the mavrilimumab Huadong Collaboration Agreement which includes $10,000, consisting of the upfront payment. The Company also included an estimate of variable consideration associated with the clinical manufacturing supply of certain materials when those materials were shipped. The Company determined that any variable consideration related to development and regulatory milestones is deemed fully constrained and therefore excluded from the transaction price due to the high degree of uncertainty and risk associated with these potential payments, as the Company determined that it could not assert that it was probable that a significant reversal in the amount of cumulative revenue recognized will not occur. The Company also determined that royalties and sales milestones relate solely to the licenses of intellectual property. Revenue related to these royalties and sales milestones will only be recognized when the associated sales occur, and relevant thresholds are met, under the sales or usage-based royalty exception of Topic 606.

The Company recognized revenue for the license performance obligations at a point in time, that is upon transfer of the license to Huadong. As control of the license was transferred on the Effective Date and Huadong could begin to use and benefit from the license, the Company recognized$10,000 of collaboration revenue during the year ended December 31, 2022 under the mavrilimumab Huadong Collaboration Agreement. Upon the termination of the mavrilimumab Huadong Collaboration Agreement in April 2025, the Company will not recognize any additional revenue from this agreement.

Accounting for the ARCALYST Huadong Collaboration Agreement

As of the Effective Date, the Company identifiedone performance obligation in the ARCALYST Huadong Collaboration Agreement: the exclusive license for ARCALYST and clinical and commercial manufacturing obligations for ARCALYST products in the Huadong Territory. Huadong cannot exploit the value of the exclusive license for ARCALYST products in the Huadong Territory without receipt of supply as the exclusive license for ARCALYST products in the Huadong Territory does not convey to Huadong the right to manufacture and therefore the Company has combined the exclusive license for ARCALYST products in the Huadong Territory and the manufacturing obligations intoone performance obligation.

The Company determined the transaction price at the inception of the ARCALYST Huadong Collaboration Agreement, which includes $12,000, consisting of the upfront payment. In 2024, the Company added $20,000 to the transaction price following the achievement of a regulatory milestone. The Company also includes an estimate of

variable consideration associated with the clinical and commercial manufacturing supply of certain materials when those materials are shipped. The Company determined that any variable consideration related to development and regulatory milestones, sales milestones and royalties are deemed fully constrained and therefore excluded from the transaction price due to the high degree of uncertainty and risk associated with these potential payments, as the Company determined that it could not assert that it was probable that a significant reversal in the amount of cumulative revenue recognized will not occur. Royalties and sales milestones will be recognized as the Company delivers the commercial manufactured product to Huadong. Any changes in estimates may result in a cumulative catch-up based on the number of units of manufactured product delivered.

The Company recognizes revenue for the single performance obligation in the ARCALYST Huadong Collaboration Agreement consisting ofthe exclusive license for ARCALYST and clinical and commercial manufacturing obligations for ARCALYST products in the Huadong Territory at a point in time, upon which control of materials are transferred to Huadong for each delivery of the associated materials. The Company currently expects to recognize the revenue over the life of the agreement. This estimate considers the timing of development and commercial activities under the ARCALYST Huadong Collaboration Agreement and may be reduced or increased based on changes in the various activities.

The Company didnot recognize any revenue under the ARCALYST Huadong Collaboration Agreement during the three and six months ended June 30, 2025. The Company recognized $189 of the upfront payment in collaboration revenue during the six months ended June 30, 2024, under the ARCALYST Huadong Collaboration Agreement related to materials delivered. The Company didnot recognize any revenue under the ARCALYST Huadong Collaboration Agreement during the three months ended June 30, 2024. As of June 30, 2025, $31,811 of the transaction price is recorded in non-current deferred revenue, based upon timing of anticipated future shipments.

The following table summarizes the Company’s contract liabilities in connection with license and collaboration agreements for the six months ended June 30, 2025:** **

10. License and Acquisition Agreements

Biogen Asset Purchase Agreement

In September 2016, the Company entered into an asset purchase agreement (the “Biogen Agreement”) with Biogen MA Inc. (“Biogen”) to acquire all of Biogen’s right, title and interest in and to certain assets used in or relating to vixarelimab and other antibodies covered by certain patent rights, including patents and other intellectual property rights, clinical data, know-how, and clinical drug supply. In addition, Biogen granted the Company a non-exclusive, sublicensable, worldwide license to certain background patent rights related to the vixarelimab program. The Company is obligated to use commercially reasonable efforts to develop and commercialize such acquired products.

Under the Biogen Agreement, the Company is obligated to make payments to Biogen of up to $179,000 upon the achievement of specified clinical and regulatory milestones in multiple indications in various territories, of which $165,000 remains as of June 30, 2025. Additionally, the Company could be obligated to make up to an aggregate of $150,000 of payments upon the achievement of specified annual net sales milestones and to pay tiered royalties on escalating tiers of annual net sales of licensed products starting in the high single-digit percentages and ending below the teens.

The Company also agreed to pay certain obligations under third party contracts retained by Biogen that relate to the vixarelimab program. Under these retained contracts, the Company paid a one-time upfront sublicense fee and is

obligated to pay insignificant annual maintenance fees as well as clinical and regulatory milestone payments of up to an aggregate of $1,575.

The Biogen Agreement will terminate upon the expiration of all payment obligations with respect to the last product in all countries in the territory. The Company has the right to terminate the agreement with 90 days’ prior written notice. Both parties may terminate by mutual written consent or in the event of material breach of the agreement by the other party that remains uncured for 90 days (or 30 days for payment-related breaches).

The Company and Biogen have amended the Biogen Agreement twice following its initial effective date. The first amendment, in July 2017, clarified the scope of the antibodies subject to the Biogen Agreement. The second amendment, effective in August 2022, was entered into in connection with the Genentech License Agreement, and amended certain defined terms, including “Net Sales,” “Indication,” “Product,” “Combination Product” and “Valid Claim.” In addition, the tiered royalty rates to be paid by the Company to Biogen increased by an amount equal to less thanone percent. Upon the termination or expiration of the Genentech License Agreement all terms of the Biogen Agreement will revert to the version of such terms in effect as of immediately prior to the effective date of the Genentech License Agreement.

During the three and six months ended June 30, 2025, the Company recorded expenses of $30 and $44, respectively, related to milestone payments and the annual maintenance fee in connection with the Biogen Agreement. During the three and six months ended June 30, 2024, the Company recorded expenses of $11 and $72, respectively, related to a milestone and the annual maintenance fee in connection with the Biogen Agreement.

Beth Israel Deaconess Medical Center License Agreement

In 2019, the Company 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 the Company’s acquisition of Primatope, the Company acquired the rights to an exclusive license to certain intellectual property rights controlled by Beth Israel Deaconess Medical Center, Inc. (“BIDMC”) to make, use, develop and commercialize abiprubart (the “BIDMC Agreement”). Under the BIDMC Agreement, the Company is solely responsible for all development, regulatory and commercial activities and costs. The Company is also responsible for costs related to filing, prosecuting and maintaining the licensed patent rights. Under the BIDMC Agreement, the Company is obligated to pay an insignificant annual maintenance fee as well as clinical and regulatory milestone payments of up to an aggregate of $1,200 to BIDMC. The Company is also obligated to pay a low single-digit royalty on annual net sales of products licensed under the agreement.

During the three and six months ended June 30, 2025, the Company didnot record any expenses in connection with the BIDMC Agreement. During the three and six months ended June 30, 2024 the Company recorded expenses of$8 and$35, respectively, in connection with the BIDMC Agreement.

Regeneron License Agreement

In September 2017, the Company entered into a license agreement (the “Regeneron Agreement”) with Regeneron Pharmaceuticals, Inc. (“Regeneron”), pursuant to which the Company has been 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, the Company’s pivotal Phase 3 clinical trial of ARCALYST, Regeneron transferred the biologics license application (“BLA”) for ARCALYST to the Company. 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, the Company assumed the sales and distribution of ARCALYST for Cryopyrin-Associated Periodic Syndromes and Deficiency of Interleukin-1 Receptor Antagonist in the United States.

The Company evenly splits 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) the Company’s cost of goods sold for product used, sold or otherwise distributed for patient use by the Company; (ii) customary commercialization expenses, including the cost of the Company’s field force, and (iii) the Company’s 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 the Company 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. The Company also evenly splits with Regeneron any proceeds received by the Company 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. For the three and six months ended June 30, 2025, the Company recognized $52,389 and $96,164 respectively, of expenses related to the profit sharing agreement presented within collaboration expenses. For the three and six months ended June 30, 2024, the Company recognized $29,943 and $50,066 respectively, of expenses related to the profit sharing agreement presented within collaboration expenses.

The Company has a supply agreement with Regeneron pursuant to which the Company may order both clinical and commercial product. The supply agreement terminates upon the termination of the Regeneron Agreement or the date of completion of the transfer of technology related to the manufacture of ARCALYST. During the three and six months ended June 30, 2025 and 2024, the Company didnot incur any research and development expense related to the purchase of drug materials under the supply agreement. As of June 30, 2025 and December 31, 2024, the Company recorded inventory of $24,906 and $21,246 respectively, related to the purchase of commercial product under the supply agreement. As of June 30, 2025, the Company had non-cancelable purchase commitments under the supply agreement (see Note 13).

The Regeneron Agreement will expire when the Company is no longer developing or commercializing any licensed product under the Regeneron Agreement. Either party may terminate the agreement upon the other party’s insolvency or bankruptcy or for material breach of the agreement by the other party that remains uncured for 90 days (or 30 days for payment related breaches). Regeneron has the right to terminate the agreement if the Company suspends its development or commercialization activities for a consecutive 12 month period or does not grant a sublicense to a third party to perform such activities, or if the Company challenges any of the licensed patent rights. The Company may terminate the agreement at any time withone year’s written notice. The Company may also terminate the agreement with three months’ written notice if the licensed product is determined to have certain safety concerns.

MedImmune License Agreement

In December 2017, the Company entered into a license agreement (as amended from time to time, the “MedImmune Agreement”) with MedImmune, Limited (subsequently acquired by AstraZeneca PLC) (“MedImmune”), pursuant to which MedImmune granted the Company an exclusive, sublicensable, worldwide license to certain intellectual property rights to make, use, develop and commercialize mavrilimumab. Under the MedImmune Agreement, the Company also acquired reference rights to relevant manufacturing and regulatory documents and MedImmune’s existing supply of mavrilimumab drug substance and product. The Company was obligated to use commercially reasonable efforts to develop and commercialize the licensed products.

In February 2025, the Company delivered a notice of termination to MedImmune, notifying them of its intent to terminate the MedImmune Agreement, for convenience, effective May 22, 2025. Following such date, the exclusive worldwide sublicense rights to certain intellectual property rights to make, use, develop and commercialize mavrilimumab were returned to MedImmune. The Company didnot record any significant charges related to the termination of the MedImmune Agreement.

During the three and six months ended June 30, 2025 and 2024, the Company didnot record any expenses in connection with milestone payments due under the MedImmune Agreement.

11. Net Income (Loss) per Share

The rights, including the liquidation and dividend rights, of the holders of Class A, Class B, Class A1 and Class B1 ordinary shares are identical, except with respect to voting, transferability and conversion (see Exhibit 4.2 to the Company’s Current Report on Form 8-K12B, filed on June 28, 2024). As the liquidation and dividend rights are identical, losses are allocated on a proportionate basis and the resulting net income (loss) per share attributed to ordinary shareholders will, therefore, be the same for both Class A and Class B ordinary shares on an individual or combined basis.

Basic and diluted net income (loss) attributable to ordinary shareholders was calculated as follows:

The Company’s unvested RSUs and PSUs have been excluded from the computation of basic net loss per share attributable to ordinary shareholders.

For the three and six months ended June 30, 2025 diluted earnings per share includes the assumed exercise of dilutive options, assumed exercise of dilutive PSOs for which the performance condition has been met, and the assumed issuance of ordinary shares for unvested RSUs and PSUs for which the market or performance condition has been met as of the date of determination, using the treasury stock method unless the effect is anti-dilutive. The treasury stock method assumes that proceeds, including cash received from the exercise of employee share options and the average unrecognized compensation expense for unvested share-based compensation awards, would be used to purchase the Company’s ordinary shares at the average market price during the period.

For the three and six months ended June 30, 2024 the Company’s potentially dilutive securities, which include options, unvested RSUs and unvested PSUs, have been excluded from the computation of diluted net loss per share attributable to ordinary shareholders as the effect would be to reduce the earnings per share (“EPS”) attributable to ordinary shareholders. Therefore, the weighted average number of ordinary shares outstanding used to calculate both basic and diluted EPS attributable to ordinary shareholders is the same. The Company excluded the following potential ordinary shares, presented based on amounts outstanding at each period end, from the computation of diluted EPS attributable to ordinary shareholders for the periods indicated because including them would have had an anti-dilutive effect:

PSUs and PSOs that are outstanding and contain performance-based or market-based vesting criteria for which the performance or market conditions have not been met are excluded from the presentation of common stock equivalents outstanding in the table above.

12. Income Taxes

Prior to the Redomiciliation, the Company was incorporated and principally subject to taxation in Bermuda. Following the Redomiciliation, the Company is incorporated and principally subject to taxation in the UK. Under the laws of Bermuda, tax on a company’s income is assessed at azero percent tax rate. As a result, the Company hasnot recorded any income tax benefits from its losses incurred in Bermuda during the reporting periods in which the Company was incorporated there, andno net operating loss carryforwards will be available to the Company for those losses. Following the Redomiciliation, the Company’s income is subject to the enacted UK statutory corporate tax rate and net operating losses incurred have an indefinite carryforward. The Company’s wholly owned United States subsidiaries, Kiniksa US and Primatope, are subject to federal and state income taxes in the United States. The Company’s wholly owned subsidiary Kiniksa Bermuda remains subject to taxation, if any, in Bermuda. The Company’s wholly owned subsidiary Kiniksa UK, and Kiniksa UK’s wholly owned subsidiaries, Kiniksa Germany, Kiniksa France, and Kiniksa Switzerland, are subject to taxation in their respective countries. Certain of the Company’s subsidiaries operate under cost plus arrangements.

The Company’s income tax rate for the three and six months ended June 30, 2025 is attributable to Kiniksa Switzerland’s, Kiniksa UK’s Swiss branch office’s, Kiniksa UK’s and Kiniksa US’s income or loss subject to taxation in each of their respective countries. Income tax provision for the three and six months ended June 30, 2025 was $5,045 and $12,071, respectively. The provision for income taxes is primarily driven by income earned in Switzerland, UK, United States and uncertain tax positions offset in part by tax benefits from Foreign Derived Intangible Income (“FDII”) deduction and United States federal and state research and development credits (“R&D Credits”).

Although Kiniksa Bermuda hadno corporate income tax, the Company’s income tax rate for the three and six months ended June 30, 2024 was due to Kiniksa Switzerland’s, Kiniksa UK’s Swiss branch office’s, Kiniksa UK’s and Kiniksa US’s income or loss subject to taxation in each of their respective countries. Income tax provision for the three and six months ended June 30, 2024 was $6,212 and $9,640, respectively. The provision for income taxes is primarily driven by income earned in the UK, Switzerland and United States offset in part by tax benefits from FDII deduction and R&D Credits.

Management regularly assesses the need for a valuation allowance on the Company’s deferred income tax assets. Valuation allowances require an assessment of both positive and negative evidence when determining whether it is more likely than not that the Company will be able to recover its deferred tax assets. Such assessment is required on a jurisdiction-by-jurisdiction basis. The ultimate realization of deferred tax assets is dependent upon the generation of future taxable income during the periods in which those temporary differences become deductible.

Since 2021, the Company has engaged in a series of intra-entity asset transfers and allocations to contribute assets to its wholly owned Switzerland subsidiary, UK subsidiary and its UK Swiss branch office.

In January 2021, in connection with its launch readiness activities, Kiniksa Bermuda contributed all of its rights, title and interest in, among other things, certain contracts (including the Regeneron Agreement), intellectual

property rights, product filings and approvals and other information, plans and materials owned or controlled by Kiniksa Bermuda insofar as they related exclusively or primarily to ARCALYST to Kiniksa UK.

In February 2022, Kiniksa Bermuda contributed its exclusive rights to develop and commercialize mavrilimumab in the Huadong Territory to Kiniksa UK. Subsequent to the contribution there was a triggering event in 2024 resulting in decreases to the tax asset balance related to mavrilimumab intangible assets.

In July 2022, Kiniksa Bermuda contributed all of its rights, title and interest in, among other things, certain contracts (including the Biogen Agreement), intellectual property rights, product filings and approvals and other information, plans and materials owned or controlled by Kiniksa Bermuda insofar as they related exclusively or primarily to vixarelimab to Kiniksa UK.

The consolidated Company did not incur tax liabilities on any of these intra-entity transfers since the transferor, Kiniksa Bermuda, is exempt from income tax in Bermuda, its jurisdiction of incorporation. Kiniksa UK accounted for the 2021 and 2022 intra-entity transfers as transfers of assets between related parties and received stepped up tax bases in the contributed intellectual property assets, equal to the fair value of the assets at the time of transfer. The Company recorded UK deferred tax assets as a result of these contributions, which represent the difference between the stepped-up tax bases and the book bases for financial statement purposes. At the time of the 2021 and 2022 transfers of the relevant assets, the Company recorded a valuation allowance on the full amount of the recognized deferred tax assets.

The fair value of the January 2021 transfer of ARCALYST intellectual property assets was determined utilizing forecasted cash flows attributable to commercial operations and estimated probabilities of success of such cash flows, discounted to present value utilizing the discounted cash flow method. The fair values of the transferred mavrilimumab and vixarelimab intellectual property assets were determined utilizing future cash flows related to agreements with third parties for the use of the applicable intellectual property and estimated probabilities of success of such cash flows, discounted to present value utilizing the discounted cash flow method.

In December 2023, Kiniksa UK allocated all of its rights, title and interest in, among other things, certain contracts (including the Regeneron Agreement), intellectual property rights, product filings and approvals and other information, plans and inventory owned or controlled by the Company insofar as they related exclusively or primarily to ARCALYST to Kiniksa UK’s Swiss branch office.

The December 2023 allocation of the assets to the Swiss branch did not result in a taxable disposal for Kiniksa UK as the allocation was to a branch within the entity. The future results of Kiniksa UK’s Swiss branch office are subject to income taxes in Switzerland. Kiniksa UK’s Swiss branch office received a step up in basis resulting in a Swiss deferred tax asset. The fair value of the allocated ARCALYST intellectual property assets was determined utilizing forecasted cash flows attributable to commercial operations and estimated probabilities of success of such cash flows, discounted to present value utilizing the discounted cash flow method. The fair value of the ARCALYST inventory was determined utilizing the average net selling price less estimated costs to sell.

In January 2024, Kiniksa Bermuda transferred to Kiniksa Switzerland all rights, title and interest in, among other things, certain contracts, intellectual property rights, product filings and approvals and other information, plans and materials owned insofar as they related exclusively or primarily to abiprubart, mavrilimumab, KPL-387, KPL-1161 and certain preclinical assets. In June 2024, Kiniksa UK terminated its exclusive rights to develop and commercialize mavrilimumab in the Huadong Territory, with such rights reverting to Kiniksa Switzerland. Thereafter Kiniksa Switzerland held worldwide rights to develop and commercialize mavrilimumab until the MedImmune Agreement was terminated in May 2025. In October 2024, Kiniksa UK contributed all of its rights, title and interest in, among other things, certain contracts (including the Biogen Agreement), intellectual property rights, product filings and approvals and other information, plans and materials owned or controlled by Kiniksa UK insofar as they related exclusively or primarily to vixarelimab to Kiniksa Switzerland.

The consolidated Company did not incur tax liabilities on any of the January 2024 intra-entity transfers since the transferor, Kiniksa Bermuda, is exempt from income tax in Bermuda. Kiniksa Switzerland accounted for the intra-entity transfers as transfers of assets between related parties and received stepped up tax bases in the contributed intellectual property assets, equal to the fair value of the assets at the time of transfer. In relation to the June 2024 transaction, Kiniksa UK received consideration in exchange for the termination of exclusive rights. Neither Kiniksa UK

nor Kiniksa Switzerland incurred any tax liabilities as a result of the transaction. The consolidated Company did not incur tax liabilities on any of the October 2024 intra-entity transfers since the transferor, Kiniksa UK, is the sole direct shareholder of Kiniksa Switzerland. Kiniksa Switzerland accounted for the intra-entity transfers as transfers of assets between related parties and received stepped up tax bases in the contributed intellectual property assets, equal to the fair value of the assets at the time of transfer.

The fair values of the transferred assets were determined utilizing future cash flows of projected operations and estimated probabilities of success of such cash flows, discounted to present value utilizing the discounted cash flow method. The Company recorded deferred tax assets as a result of these contributions, which represent the difference between the stepped-up tax bases and the book bases for financial statement purposes. The Company maintains a valuation allowance on the full amount of the Kiniksa Switzerland deferred tax assets. There areno material deferred tax assets in the jurisdictions outside the United States, UK and Switzerland.

13. Commitments and Contingencies

License Agreements

The Company has entered into license agreements with various parties under which it is obligated to make contingent and non-contingent payments (see Note 10).

Manufacturing Commitments

The Company has a supply agreement with Regeneron pursuant to which the Company may order both clinical and commercial product (see Note 10). In June 2024, the Company entered into a Master Services Agreement and a Product Specific Agreement with Samsung as part of its technology transfer of the manufacturing process for ARCALYST drug substance. The Company has additionally entered into agreements with several contract development and manufacturing organizations to provide the Company with preclinical and clinical trial materials for its non-ARCALYST assets. As of June 30, 2025, the Company had committed to minimum purchase commitments under all of these agreements totaling $161,555, of which $25,621 is due within one year.

The Company issued termination notices to CDMOs in February 2025 to terminate the clinical supply agreements for the production of abiprubart. During the six months ended June 30, 2025, the Company recorded and paid $2,500 in research and development expenses because of these terminations. During the three months ended June 30, 2025, the Company didnot record any expenses in connection with these terminations. The Company does not expect to incur any additional expenses because of these terminations.

Performance Cash Awards

Beginning in the second quarter of 2025, the Company began granting cash awards (“Performance Cash Awards”) to certain eligible employees pursuant to the 2018 Plan, which were eligible to be received upon the achievement of certain specified development and regulatory milestones and that are subject to earnout percentages based upon the date of applicable milestone achievement. As of June 30, 2025, the Company estimates the future cash payments under such Performance Cash Awards to be $22,309 if the milestones are achieved. The Performance Cash Awards will be recognized when the applicable milestones are deemed probable of achievement with a cumulative catch-up and recognized over the remaining term.

Indemnification Agreements

The Company is not aware of any claims under indemnification arrangements that are expected to have a material effect on its financial position, results of operations or cash flows, and it has not accrued any liabilities related to such obligations in its consolidated financial statements as of June 30, 2025 or December 31, 2024.

Legal Proceedings

The Company is not a party to any material litigation and does not have contingency reserves established for any litigation liabilities.

14. Segment Information and Geographic Data

The Company manages its operations as a single operating segment for the purposes of assessing performance and making operating decisions. The Company’s singular focus is on developing and commercializing novel therapies that target cardiovascular diseases with significant unmet medical need. The Company’s Chief Operating Decision Maker (“CODM”) is the Chief Executive Officer. The Company’s CODM reviews consolidated operating results and decides how to allocate resources based on net income that also is reported on the income statement as consolidated net income. The measure of segment assets is reported on the balance sheet as total consolidated assets. The CODM utilizes net income to make key decisions about how to allocate resources across the Company’s commercial product and development programs.

The following table presents selected financial information with respect to the Company’s single operating segment for the three and six months ended June 30, 2025 and 2024:

The following table presents total revenue by geographic region of the customer for the three and six months ended June 30, 2025 and 2024: