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 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 “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 subsequently liquidated Kiniksa Bermuda in November 2025, completing the Redomiciliation.

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”) 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, GmbH (“Kiniksa Switzerland”), Kiniksa Pharmaceuticals (Germany) GmbH (“Kiniksa Germany”) and Kiniksa Pharmaceuticals (France) SARL (“Kiniksa France”), 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”.

Reclassifications

Certain prior year amounts have been reclassified for consistency with the current year presentation. Thesereclassifications had no effect on the reported results of operations and comprehensive loss or cash flows. A reclassification has been made to Note 9Accrued Expenses for fiscal year ended December 31, 2024, to reclassify the accrued inventory and manufacturing to be a separate line item.

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, uncertain tax positions, 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.

Reporting and Functional Currency

The financial results of the Company’s global activities are reported in United States dollars (“USD”) and its foreign subsidiaries other than Kiniksa UK and Kiniksa Switzerland generally utilize their respective local currency to be their functional currency.

Transactions in other currencies are recorded in the functional currency at the rate of exchange prevailing when the transactions occur. Monetary assets and liabilities denominated in other currencies are re-measured into the functional currency at the rate of exchange in effect at the balance sheet date. Exchange rate gains and losses arising from re-measurement of foreign currency-denominated monetary assets and liabilities are included in income or losses in the period in which they occur.

For the Company’s foreign subsidiaries where the local currency is the functional currency, assets and liabilities denominated in local currencies are translated into USD at end-of-period exchange rates and the resulting translation adjustments are reported as a component of accumulated other comprehensive income (loss) within shareholders’ equity.

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 December 31, 2025, the Company had an accumulated deficit of $462,138. During the year ended December 31, 2025, the Company recorded a net income of $59,005 and provided $137,985 of cash from operating activities. As of December 31, 2025, the Company had cash, cash equivalents and short-term investments of $414,074.

Based on its current operating plan, the Company expects that its cash, cash equivalents and short-term investments combined with cash anticipated to be generated from sales of ARCALYST 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.

2. Summary of Significant Accounting Policies

Cash and Cash Equivalents

The Company classifies deposits in banks, money market funds and cash invested temporarily in various instruments with maturities of three months or less at the time of purchase as cash and cash equivalents. As of December

31, 2025 and 2024 cash and cash equivalents consisted principally of amounts held in money market accounts and cash on deposit at commercial banks.

Short-Term Investments

The Company generally invests its excess cash in money market funds and short-term investments in U.S. Treasury securities. The Company has classified its investments with maturities beyond one year as short-term, based on their highly liquid nature and because such marketable securities represent the investment of cash that is available for current operations. Such investments which are included in short-term investments on the Company’s consolidated balance sheets are considered available-for-sale (“AFS”) debt securities and are reported at fair value with unrealized gains and losses recognized in accumulated other comprehensive income (loss) in shareholders’ equity, net of related tax effects. Realized gains and losses, if any, on short-term investments are included in interest income.

If the AFS debt security’s fair value declines below its amortized cost the Company considers all available evidence to evaluate the extent to which the decline is due to credit-related factors or noncredit-related factors. If the decline is due to noncredit-related factors then no credit loss is recorded and the unrealized loss is recognized in accumulated other comprehensive income (loss) in shareholders’ equity, net of the related tax effects. If the decline is considered to be a credit-related impairment, it is recognized as an allowance on the consolidated balance sheet with a corresponding charge to the consolidated statement of operations and comprehensive income (loss). The credit allowance is limited to the difference between the fair value and the amortized cost basis. No credit-related allowances or impairments have been recognized on the Company’s investments in available-for-sale debt securities.

Concentrations of Credit Risk

Financial instruments that potentially subject the Company to concentrations of credit risk consist principally of cash, cash equivalents and short-term investments. As of December 31, 2025 and 2024, substantially all of the Company’s cash, cash equivalents and short-term investments were held attwo financial institutions. The Company generally maintains balances in various operating accounts at financial institutions that management believes to be of high credit quality, in amounts that may exceed federally insured limits. The Company has not experienced any losses related to its cash, cash equivalents and short-term investments and does not believe that it is subject to unusual credit risk beyond the normal credit risk associated with commercial banking relationships.

The Company is also subject to credit risk from the accounts receivable related to product revenue. The majority of trade accounts receivable are recorded net of allowances for cash discounts associated with prompt payments from customers. All trade accounts receivable arise from product revenue in the United States due from the Company’s third party logistics provider. There were no material write-offs charged against the allowance for the year ended December 31, 2025.

Fair Value Measurements

Certain assets and liabilities of the Company are carried at fair value under GAAP. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. 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 Company’s cash equivalents and short-term investments, consisting of money market accounts and U.S. Treasury securities, are carried at fair value, determined based on Level 1 and 2 inputs in the fair value hierarchy described above (see Note 3). The carrying values of the Company’s prepaid expenses and other current assets, accounts receivable, accounts payable and accrued expenses approximate their fair values due to the short-term nature of these assets and liabilities.

Leases

At the inception of an arrangement, the Company determines whether the arrangement is or contains a “lease” as defined by ASC 842. A lease is an arrangement, or part of an arrangement, that conveys the right to control the use of identified property, plant, or equipment (an identified asset) for a period of time in exchange for consideration. The Company determines if the arrangement conveys the right to control the use of an identified asset for a period of time. It assesses throughout the period of use whether the Company has both of the following (1) the right to obtain substantially all of the economic benefits from use of the identified asset and (2) the right to direct the use of the identified asset. This determination is reassessed if the terms of the arrangement are changed. Leases are classified as operating or finance leases based on the terms of the lease agreement and certain characteristics of the identified asset. Right-of-use (“ROU”) assets and lease liabilities are recognized at lease commencement date based on the present value of the minimum future lease payments.

Leases with a term greater than one year are recognized on the balance sheet as ROU assets with corresponding lease liabilities and, if applicable, long-term lease liabilities. The Company has elected not to recognize leases with a term of one year or less on its balance sheet. The Company recognizes lease expense for these leases on a straight-line basis over the lease term. Operating leases, ROU assets and their corresponding lease liabilities are recorded based on the present value of lease payments over the expected remaining lease term. However, certain adjustments to the ROU assets may be required for items such as incentives received. The interest rate implicit in lease arrangements is typically not readily determinable. As a result, the Company utilizes its incremental borrowing rate, which is the rate incurred to borrow on a collateralized basis over a similar term an amount equal to the lease payments in a similar economic environment.

In accordance with the guidance in ASU 2016-02, components of a lease should be split into three categories: lease components (e.g., land, building, etc.), non-lease components (e.g., common area maintenance, consumables, etc.), and non-components (e.g., property taxes, insurance, etc.); then the fixed and in-substance fixed contract consideration (including any related to non-components) must be allocated based on fair values to the lease components and non-lease components.

The Company has elected to account for the lease and non-lease components of each of its operating leases as a single lease component and allocate all of the arrangement consideration to the lease component only. The lease component results in an operating ROU asset being recorded on the balance sheet and amortized on a straight-line basis as lease expense.

Property and Equipment

Property and equipment are recorded at cost and depreciated over the estimated useful lives of the related assets using the straight-line method. Maintenance and repairs are charged to expense as incurred. When assets are retired or otherwise disposed of, the cost of these assets and related accumulated depreciation or amortization are eliminated from the consolidated balance sheet and any resulting gains or losses are included in the consolidated statement of operations and comprehensive income (loss) in the period of disposal. The expected useful lives of the respective assets are as follows:

Inventory

Inventories are stated at the lower of cost or estimated net realizable value with cost based on the first-in first-out method. The Company classifies inventory as long-term when the inventory is expected to be utilized beyond the Company’s normal operating cycle and includes such amounts in other long-term assets in the Company’s consolidated balance sheets. Prior to the regulatory approval of its drug candidates, the Company incurs expenses for the manufacture of product candidate supplies to support clinical development that could potentially be available to support the commercial launch of those therapeutics. Until the date at which regulatory approval has been received or is otherwise considered probable, the Company records all such costs as research and development expenses. The Company performs an assessment of the recoverability of capitalized inventories during each reporting period and writes down any excess and obsolete inventory to its net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of sales in the Company’s consolidated statements of operations and comprehensive income (loss). The determination of whether inventory costs will be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected by management, additional write-down of inventory may be required.

Finished goods that can be used in either the production of clinical or commercial products is expensed as research and development costs when identified and labeled for use in clinical trials as the products are required to be re-labeled for alternative uses. The finished goods inventory that will ultimately be distributed free of charge under the Company’s patient assistance program are recognized as selling expenses when they are labeled as free goods.

The Company is conducting a technology transfer of ARCALYST drug substance manufacturing from Regeneron Pharmaceuticals, Inc. (“Regeneron”) to Samsung Biologics Co., Ltd. (“Samsung”). Costs associated with the establishment of ARCALYST production at a new manufacturing site that do not meet the criteria for research and development or capitalization into inventory, including raw materials consumed, are included in cost of goods sold in the period incurred. During the years ended December 31, 2025, 2024 and 2023 the Company incurred $11,704, $15,849 and $3,265, respectively, of expense related to the technology transfer of ARCALYST drug substance manufacturing in cost of goods sold.

Revenue Recognition

ASC 606 outlines a five-step process for recognizing revenue from contracts with customers: (i) identify the contract with the customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the separate performance obligations in the contract, and (v) recognize revenue associated with the performance obligations as they are satisfied.

The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. Once a contract is determined to be within the scope of ASC 606, the Company determines the performance obligations that are distinct. The Company recognizes as revenues the amount of the transaction price that is allocated to each respective performance obligation when the performance obligation is satisfied. Generally, the Company’s performance obligations are transferred to customers at a point in time, typically upon delivery of the product to the customer.

ASC 606 requires entities to record a contract asset when a performance obligation has been satisfied or partially satisfied, but the amount of consideration has not yet been received because the receipt of the consideration is conditioned on something other than the passage of time. ASC 606 also requires an entity to present a revenue contract as a contract liability in instances when a customer pays consideration, or an entity has a right to an amount of consideration that is unconditional (e.g. receivable), before the entity transfers a good or service to the customer.

Product Revenue, Net

Following the FDA approval of ARCALYST in March 2021, the Company began generating product revenue from sales of ARCALYST. ARCALYST is sold through a third party logistics provider that distributes primarily through a network of authorized specialty pharmacies and specialty distributors (“customer”), which deliver the medication to patients by mail. The Company’s payment terms are between 30 to 35 days.

Net revenue from product sales is recognized at the transaction price when the specialty pharmacy or specialty distributors obtains control of the Company’s products, which occurs at a point in time, typically upon shipment of the product from the third party logistics provider.

The Company’s net revenues represent total revenues adjusted for discounts and allowances, including estimated cash discounts, chargebacks, rebates, returns, copay assistance, and specialty pharmacy and distributor fees. These adjustments represent variable consideration under ASC 606 and are estimated using the expected value method and are recorded when revenue is recognized on the sale of the product. These adjustments are established by management as its best estimate based on available information and will be adjusted to reflect known changes in the factors that impact such allowances. Adjustments for variable consideration are determined based on the contractual terms with customers, historical trends, communications with customers and the levels of inventory remaining in the distribution channel, as well as expectations about the market for the product and anticipated introduction of competitive products.

Discounts and Allowances

Revenue from product sales is recorded at the transaction price, which includes estimates for discounts and allowances and includes cash discounts, chargebacks, rebates, returns, copay assistance, and specialty pharmacy and distributor fees. These reserves are classified as reductions of accounts receivable (if the amount is payable to the Customer and right of offset exists) or a current liability (if the right of offset does not exist, the amount is payable to a third party, or is related to a future return). These allowances are established by management as its best estimate based on historical experience and data points available and are adjusted to reflect known changes in the factors that impact such reserves. Allowances for customer credits, chargebacks, rebates, data fees for services, returns, and discounts are

established based on contractual terms with customers and analyses of historical usage of these items. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. The nature of the allowances and accruals requiring estimates, and the specific considerations the Company uses in estimating these amounts are as follows:

Government Chargebacks and Rebates

Government and other rebates and chargebacks include amounts payable to payors and healthcare professionals under various programs and by payor and individual payor plans. Rebates and chargebacks are based on contractual arrangements or statutory requirements which may vary by product, payor and individual payor plans. For qualified programs that can purchase products through wholesalers or other distributors at a lower contractual price, the wholesalers or distributors charge back to the Company the difference between their acquisition cost and the lower contractual price.

Rebates and chargebacks are estimated primarily based on product sales, and expected payor mix and discount rates, which require significant estimates and judgment. Additionally, in developing the estimates the Company considers: historical and estimated payor mix; statutory discount requirements and contractual terms; historical claims experience and processing time lags; estimated patient population; known market events or trends; market research; channel inventory data obtained from customers; and other pertinent internal or external information. The Company assesses and updates the estimates every quarter to reflect actual claims and other current information.

Government and other chargebacks are recognized as reduction of revenue upon the sale to the Customers. These items are payable to customers and other rebates that are payable to other third party payors are classified as accrued expense liabilities.

Cash Discounts

The Company estimates cash discounts based on contractual terms and expectations regarding future customer payment patterns.

Specialty Pharmacy & Distributor Fees

Under the inventory management agreements with specialty pharmacies and distributors, the Company pays a fee primarily for compliance with certain contractually determined covenants such as the maintenance of agreed upon inventory levels. These specialty pharmacy and distributor fees are based on a contractually determined fixed percentage of sales.

The Company has contracted with certain specialty pharmacies to obtain transactional data related to the products in order to develop a better understanding of the selling channel as well as patient activity and utilization by the Medicaid program and other government agencies and managed care organizations. The Company pays a variable fee to the specialty pharmacies to provide the data. The Company also pays the specialty pharmacies a fee in exchange for providing distribution and inventory management services, including the provision of inventory management data to the Company. The Company estimates the fee for service accruals and allowances based on sales to each specialty pharmacy and the applicable contracted rate.

Sales Returns

Allowances are made for estimated sales returns by the customers and are recorded in the period the related revenue is recognized. The Company typically permit returns if the product is out of date or damaged during transition to

the common carrier. The Company’s estimates of sales returns are based primarily on the Company’s historical return rate. The Company also takes into consideration known or expected changes in the marketplace specific to ARCALYST.

Shipping and Handling

Shipping and handling activities are considered to be fulfillment activities and not considered to be a separate performance obligation.

Other Incentives

Other incentives include a co-pay assistance program for eligible patients with commercial insurance in the United States. The co-pay assistance programs assist certain commercially insured patients by reducing each participating patient’s financial responsibility for the purchase price, up to a specified dollar amount of assistance.

Collaboration Expenses

Collaboration expenses consist of Regeneron’s share of the profit related to ARCALYST sales under the license agreement (the “Regeneron Agreement”) with Regeneron (see Note 13) and the cost of products sold under collaboration agreements. 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.

License and Collaboration Revenue

License and collaboration revenue includes amounts recognized related to upfront payments, royalty revenue, milestone payments and products sold under collaboration agreements.

The Company analyzes its collaboration arrangements to assess whether such arrangements involve joint operating activities performed by parties that are both active participants in the activities and exposed to significant risks and rewards dependent on the commercial success of such activities and therefore within the scope of ASC Topic 808, Collaborative Arrangements (“Topic 808”). This assessment is performed throughout the life of the arrangement based on changes in the responsibilities of all parties in the arrangement. For collaboration arrangements within the scope of Topic 808 that contain multiple elements, the Company first determines which elements of the collaboration are deemed to be within the scope of Topic 808 and which elements of the collaboration are more reflective of a vendor-customer relationship and therefore within the scope of Topic 606.

For elements of collaboration arrangements that are accounted for pursuant to ASC 606, the Company identifies the performance obligations and allocates the total consideration the Company expects to receive on a relative standalone selling price basis to each performance obligation. Variable consideration such as performance-based milestones will be included in the total consideration if the Company expects to receive such consideration and if it is probable that the inclusion of the variable consideration will not result in a significant reversal in the cumulative amount of revenue recognized under the arrangement. The Company’s estimate of the total consideration the Company expects to receive under each collaboration arrangement is updated for each reporting period, and any adjustments to revenue are recorded on a cumulative catch-up basis. The Company excludes sales-based royalty and milestone payments from the total consideration the Company expects to receive until the underlying sales occur because the license to the Company’s intellectual property is deemed to be the predominant item to which the royalties or milestones relate as it is the primary driver of value in the Company’s collaboration arrangements.

Key assumptions to determine the standalone selling price may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates and probabilities of technical and regulatory success.

The Company recognize revenue associated with each performance obligation as the control over the promised goods or services transfer to the Company’s collaboration partner which occurs either at a point in time or over time. If control transfers over time, revenue is recognized by using a method of measuring progress that best depicts the transfer of goods or services. The Company evaluates the measure of progress and related inputs each reporting period and any resulting adjustments to revenue are recorded on a cumulative catch-up basis.

Consideration received that does not meet the requirements to satisfy ASC 808 or ASC 606 revenue recognition criteria is recorded as deferred revenue in the accompanying consolidated balance sheets, classified as either short-term (less than 12 months) or long-term (more than 12 months) deferred revenue based on the Company’s best estimate of when such revenue will be recognized.

Intangible Assets

Upon FDA approval and commercial launch of ARCALYST in March 2021, the Company capitalized the$20,000 milestone payment to Regeneron for a specified regulatory milestone as a finite-lived intangible asset (see Note 13). The intangible asset is amortized on a straight-line basis over the life of the underlying intellectual property of 20 years. Amortization expense is recorded as cost of goods sold in the Company’s consolidated statement of operations and comprehensive income (loss).

Impairment of Long-Lived Assets

The Company assesses the impairment of long-lived assets, including intangible assets and property and equipment, whenever events or changes in business circumstances indicate that the carrying amounts of the assets may not be fully recoverable. When such events occur, the Company determines whether there has been an impairment in value by comparing the asset’s carrying value with the anticipated undiscounted net cash flows of the asset. If an impairment in value exists, the asset is written down to its estimated fair value. The Company hasnot recognized any impairment losses through December 31, 2025 and there have been no events that triggered an impairment analysis.

Research and Development Costs

Research and development costs are expensed as incurred. Research and development expenses consist of costs incurred to discover, research and develop drug candidates, including personnel expenses, share-based compensation expense, allocated facility-related and depreciation expenses, third party license fees and external costs of outside vendors engaged to conduct preclinical and clinical development activities and clinical trials as well as to manufacture clinical trial materials. Non-refundable prepayments determined to be used within one year for goods or services that will be used or rendered for future research and development activities are recorded as prepaid expenses. Non-refundable prepayments or minimum balance requirements associated with clinical trials determined to not be used within one year are classified as other long-term assets. Such amounts are recognized as an expense as the goods are delivered or the related services are performed, or until it is no longer expected that the goods will be delivered, or the services rendered. Milestone and other payments made to third parties with respect to in-process research and development, in accordance with the Company’s license, acquisition and other similar agreements are expensed when determined to be probable and estimable.

Research Contract Costs

The Company has entered into various research and development-related contracts with companies both inside and outside of the United States. The related costs are recorded as research and development expenses as incurred. The Company records accruals for estimated ongoing research and development costs. When billing terms under these contracts do not coincide with the timing of when the work is performed, the Company is required to make estimates of outstanding obligations to those third parties as of the end of the reporting period. Any accrual estimates are based on a

number of factors, including the Company’s assessment of the progress towards completion of the research and development activities, invoicing to date under the contracts, communication from the research institution or other companies of any actual costs incurred during the period that have not yet been invoiced, and the costs included in the contracts. Significant judgments and estimates are made in determining the accrued balances at the end of any reporting period. Actual results could differ materially from the Company’s estimates.

Patent Costs

The Company charges patent-related costs in connection with filing and prosecuting patent applications to operations as incurred as their realization is uncertain. These costs are classified as selling, general and administrative expenses.

Selling, General and Administrative Expense

Selling, general and administrative expenses consist primarily of salaries and benefits, including share based compensation expense for personnel in selling, marketing, medical, executive, business development, finance, human resources, legal and support personnel functions. Selling, general and administrative expenses also include external commercialization, marketing, and professional fees for legal, patent, and accounting services.

Advertising costs are expensed as incurred. For the years ended December 31, 2025, 2024 and 2023, advertising costs totaled $12,061, $11,433 and $9,066, respectively.

Share-Based Compensation

The Company measures all share-based awards granted to employees and directors based on their fair value on the date of grant. The Company issues share-based awards with both service-based, performance-based and market-based vesting conditions. The Company recognizes compensation expense for awards with service and market conditions on a straight-line basis over the requisite service period. For awards that contain performance conditions, the Company determines the appropriate amount to expense based on the anticipated achievement of performance targets, which requires judgment, including forecasting the achievement of future specified targets. At the date performance conditions are determined to be probable of achievement, the Company records a cumulative expense catch-up, with remaining expense amortized over the remaining service period. Throughout the performance period, the Company re-assesses the estimated performance and updates the number of performance-based awards that the Company believes will ultimately vest.

For share-based awards granted to consultants and non-employees, compensation expense is recognized over the vesting period of the awards, which is generally the period during which services are rendered by such consultants and non-employees until completed.

The Company classifies share-based compensation expense in its consolidated statements of operations and comprehensive income (loss) in the same manner in which the award recipient’s payroll costs are classified or in which the award recipient’s service payments are classified.

The fair value of each option grant is estimated on the date of grant using the Black-Scholes option-pricing model, which requires inputs based on certain subjective assumptions, including the expected share price volatility, the expected term of the award, the risk-free interest rate, and expected dividends (see Note 11). Prior to May 2018, the Company was a private company and, accordingly, lacked company-specific historical and implied volatility information for its shares. Therefore, it estimated its expected share price volatility based on the historical volatility of the Company and historical volatility of publicly traded peer companies until such time as it had adequate historical data regarding the volatility of its own traded share price. The expected term of the Company’s options has been determined utilizing the

“simplified” method for awards that qualify as “plain-vanilla” options. The expected term of options granted to non-employees is equal to the contractual term of the option award. The risk-free interest rate is determined by reference to the United States Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is based on the fact that the Company has never paid cash dividends on ordinary shares and does not expect to pay any cash dividends in the foreseeable future.

The fair value of each restricted share unit award is based on the closing price of the Company’s Class A ordinary shares on the date of grant, with the exception of PSUs with market conditions, which are measured using the Monte Carlo valuation model. The Monte-Carlo valuation model requires the use of assumptions, including but not limited to the expected volatility, correlation coefficients, risk free rate, expected dividend yield and expected term.

Comprehensive Income (Loss)

Comprehensive income (loss) includes net income (loss) as well as other changes in shareholders’ equity that result from transactions and economic events other than those with shareholders. For the years ended December 31, 2025, 2024 and 2023 the Company’s other comprehensive income (loss) was comprised of unrealized gain (loss) on short-term investments and currency translation adjustments, net of tax.

Net Income (Loss) per Share

Basic net income (loss) per share attributable to ordinary shareholders is computed by dividing the net income (loss) attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding for the period. Diluted net income (loss) attributable to ordinary shareholders is computed by adjusting net income (loss) attributable to ordinary shareholders to reallocate undistributed earnings based on the potential impact of dilutive securities. Diluted net income (loss) per share attributable to ordinary shareholders is computed based on the treasury method by dividing the diluted net income (loss) attributable to ordinary shareholders by the weighted average number of ordinary shares outstanding for the period, including potential dilutive ordinary shares. For purpose of this calculation, outstanding share options, unvested restricted share units and unvested performance-based share units for which the market or performance condition has been met as of the date of determination, are considered potential dilutive ordinary shares.

In periods in which the Company reports a net loss attributable to ordinary shareholders, diluted net loss per share attributable to ordinary shareholders is the same as basic net loss per share attributable to ordinary shareholders, since dilutive ordinary shares are not assumed to have been issued if their effect is anti-dilutive. The Company reported a net loss attributable to ordinary shareholders for the year ended December 31, 2024.

The Company accounts for income taxes using the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been recognized in the consolidated financial statements or in the Company’s tax returns. Deferred tax assets and liabilities are determined based on the difference between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. Changes in deferred tax assets and liabilities are recorded in the (provision) benefit for income taxes. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent it believes, based upon the weighting of the positive and negative available evidence, that it is more likely than not that all or a portion of the deferred tax assets will not be realized, a valuation allowance is established through a charge to income tax expense. Potential for recovery of deferred tax assets is evaluated by estimating the future taxable profits expected, cumulative recent earnings and considering prudent and feasible tax planning strategies.

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 United Kingdom. Under the previous laws of Bermuda, tax on a company’s income is assessed at azero percent tax rate. As a result, the Company has not recorded any income tax benefits from its losses incurred in Bermuda during the reporting periods in which it 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 United Kingdom 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 for the period of time prior to its liquidation in November 2025. The Company’s wholly owned subsidiary Kiniksa UK, and Kiniksa UK’s wholly owned subsidiaries, Kiniksa Switzerland, Kiniksa Germany, and Kiniksa France are subject to taxation in their respective countries. Certain of the Company’s subsidiaries operate under cost plus intercompany arrangements.

The Company accounts for uncertainty in income taxes recognized in the consolidated financial statements by applying a two-step process to determine the amount of tax benefit to be recognized. First, the tax position must be evaluated to determine the likelihood that it will be sustained upon external examination by the taxing authorities. If the tax position is deemed more-likely-than-not to be sustained, the tax position is then assessed to determine the amount of benefit to recognize in the consolidated financial statements. The amount of the benefit that may be recognized is the largest amount that has a greater than 50% likelihood of being realized upon ultimate settlement. The provision for income taxes includes the effects of any resulting tax reserves, or unrecognized tax benefits, that are considered appropriate as well as the related net interest and penalties.

Recently Issued Accounting Pronouncements

In November 2024, the FASB issued Accounting Standards Update (“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 on its consolidated financial statements.

In September 2025, the FASB issued ASU 2025-06,Intangibles—Goodwill and Other—Internal-Use Software (Subtopic 350-40): Targeted Improvements to the Accounting for Internal-Use Software. ASU 2025-06 modernizes and simplifies the accounting for software development costs by establishing a single capitalization framework for all internally developed or acquired software, regardless of whether the software is intended for internal use, to be sold, or to be used in delivering products and services. The new guidance retains the concept of project stages but eliminates the historical distinction between internal-use software and software to be sold or marketed. ASU 2025-06 is effective for fiscal years beginning after December 15, 2027, including interim periods within those fiscal years, with early adoption permitted. The guidance is required to be applied prospectively, with optional retrospective or modified retrospective transition methods. The Company is currently evaluating the impact of ASU 2025-06 on its consolidated financial statements.

Recently adopted accounting pronouncements

In December 2023, the FASB issued 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 Company prospectively adopted ASU 2023-09 during the year ended December 31, 2025. See Note 14Income Taxes in the accompanying notes to the consolidated financial statements for further detail.

3. Fair Value of Financial Assets and Liabilities

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 years ended December 31, 2025 and 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 December 31, 2025 and 2024 included United States Treasury securities, which are not traded on a daily basis and, therefore, represent a Level 2 measurement in the fair value hierarchy at each period end.

The contractual maturities of short-term investments were as follows:

The following tables summarize short-term investments:

As of December 31, 2025 and 2024 the Company considers the unrealized losses in their 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 their available-for-sale securities for the years ended December 31, 2025 or 2024.

4. Product Revenue, Net

ARCALYST

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

The following tables summarizes balances and activity in each of the product revenue allowance and reserve categories for the years ended December 31, 2025 and 2024:

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

pl

5. Inventory

Inventory consisted of the following:

As of December 31, 2025, $20,883 of semi-finished goods were associated with the Company’s technology transfer of ARCALYST drug substance 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.

6. Property and Equipment, Net

Property and equipment, net consisted of the following:

Depreciation expense for the years ended December 31, 2025, 2024 and 2023 was $196, $448 and $1,109, respectively.

7. Leases

The Company leases office, laboratory space and vehicles under operating leases. In May 2023, the Company entered into a lease amendment to extend the term of the Lexington, Massachusetts headquarters lease byforty-eight months to August 31, 2028. The Company accounted for the lease amendment as a modification and recorded increases in the right-of-use-assets and lease liability of $8,515.

The components of lease cost for the year ended December 31, 2025, 2024 and 2023 are as follows:

Variable lease costs primarily related to operating expense, taxes and insurance associated with the Company’s operating leases. As these costs are generally variable in nature, they are not included in the measurement of the operating lease asset and related lease liability.

Maturities of operating leases liabilities were as follows:

8. Intangible Assets

Intangible assets, net of accumulated amortization, impairment charges and adjustments are summarized in the following table.

As of December 31, 2025 future amortization of intangible assets are as follows:

** 9. Accrued Expenses**

Accrued expenses consisted of the following:

10. Ordinary Shares

The rights of the holders of the Company’s Class A ordinary shares, Class B ordinary shares, Class A1 ordinary shares and Class B1 ordinary shares are identical, except with respect to voting, transferability and conversion, as described below. The Company has authorized 200,000,000 shares, at a nominal value of $0.000273235 as of December 31, 2025 and 2024.

Voting

Each Class A ordinary share entitles the holder toone vote on all matters submitted to the shareholders for a vote. Each Class B ordinary share entitles the holder toten votes on all matters submitted to the shareholders for a vote. The holders of Class A and Class B ordinary shares, voting together as a single class, are entitled to elect the directors of the Company. Holders of Class A1 ordinary shares and Class B1 ordinary shares haveno voting rights.

Dividends

The Company’s ordinary shareholders are entitled to receive dividends, as may be declared by the Company’s board of directors. Through December 31, 2025, no cash dividends have been declared or paid.

Conversion

Each Class B ordinary share automatically converts intoone Class A ordinary share upon certain transfers of such shares by the holder thereof (subject to certain exceptions). Each Class B ordinary share is convertible, at the holder’s election intoone Class A ordinary share orone Class B1 ordinary share. Each Class A1 ordinary share is convertible intoone Class A ordinary share at the holder’s election (subject to certain exceptions). Each Class B1 ordinary share automatically converts intoone Class A ordinary share upon certain transfers of such shares by the holder thereof (subject to certain exceptions). Each Class B1 ordinary share is convertible intoone Class A ordinary share orone Class B ordinary share at the holder’s election (subject to certain exceptions). There are no conversion rights associated with the Class A ordinary shares.

Kiniksa Bermuda Shares

In connection with the Redomiciliation, Kiniksa Bermuda was issued withone ordinary share with a nominal value of £0.01 per share (the “KNSA Bermuda Ordinary Share”) and 50,000 redeemable preference shares with a nominal value of £1.00 per share (the “KNSA Bermuda Preference Shares”) in the capital of Kiniksa International in order to satisfy the initial authorized minimum capital requirements for an English public company which is currently prescribed as GBP£50,000. In the year ended December 31, 2025, (i) the KNSA Bermuda Ordinary Share was gifted to Kiniksa International fornil consideration; and (ii) the KNSA Bermuda Preference Shares were redeemed in order to remove Kiniksa Bermuda as a shareholder of Kiniksa International. The KNSA Bermuda Preference Shares have no rights to vote at any general meeting of Kiniksa International and have no right to receive any dividend. The rights and restrictions attaching to the Existing Preference Shares and KNSA Bermuda Ordinary Share are set out in the articles of association of Kiniksa International. As of December 31, 2025 there areno KNSA Bermuda Ordinary Shares or KNSA Bermuda Preference Shares in issue. In November 2025, Kiniksa Bermuda was liquidated as part of the completion of the Redomiciliation.

11. 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 Plan, the 2015 Plan, and the 2018 ESPP.

2018 Incentive Award Plan

In May 2018, the Company’s board of directors and shareholders approved the 2018 Incentive Award Plan (the “2018 Plan”), which became effective on May 23, 2018. The 2018 Plan provides for the grant of incentive share options, nonqualified share options, share appreciation rights, restricted shares, dividend equivalents, restricted share units and other share- or cash- based awards. Upon the effectiveness of the 2018 Plan, the Company ceased granting awards under its 2015 Equity Incentive Plan (as amended, the “2015 Plan” together with the 2018 Plan, the “Plans”).

A total of 4,466,500 Class A ordinary shares were initially reserved for issuance under the 2018 Plan. The number of Class A ordinary shares that may be issued under the 2018 Plan will automatically increase on each January 1, beginning in 2019 and continuing for each fiscal year until, and including, the fiscal year ending December 31, 2028, equal to the lesser of (1)4% of the Class A ordinary shares outstanding (on an as-converted basis) on the final day of the immediately preceding calendar year and (2) a smaller number of Class A ordinary shares

determined by the Company’s board of directors. As of December 31, 2025,5,621,352 shares remained available for future grant. On January 1, 2026, the Class A ordinary shares issuable pursuant to the 2018 Plan increased by 3,051,742 shares, equal to 4% of the as-converted Class A ordinary shares outstanding on December 31, 2025. The Class A ordinary shares underlying any awards issued under the 2018 Plan or the 2015 Plan that on or after the effective date of the 2018 Plan expire, lapse unexercised or are terminated, exchanged for cash, surrendered, repurchased, canceled without having been fully exercised, or forfeited under the 2018 Plan or the 2015 Plan will be added back to the Class A ordinary shares available for issuance under the 2018 Plan.

2015 Equity Incentive Plan

Until May 23, 2018 (the effective date of the 2018 Plan), the 2015 Plan provided for the Company to grant incentive share options, nonqualified share options, share grants and other share-based awards to employees and non-employees to purchase the Company’s Class A ordinary shares. On the effective date of the 2018 Plan, the Company ceased granting awards under the 2015 Plan. At that time, the 4,691,213 Class A ordinary shares subject to outstanding awards under the 2015 Plan remained reserved for issuance under the plan pursuant to such awards and the 92,170 Class A ordinary shares that had been available for future grant under the 2015 Plan were no longer authorized and reserved for issuance or available for future grant under the 2015 Plan.

As of December 31, 2025, there were 618,561 Class A ordinary shares subject to outstanding awards under the 2015 Plan and reserved for issuance thereunder pursuant to such awards. The 2015 Plan continues to govern the terms and conditions of the outstanding awards granted under it. Class A ordinary shares subject to awards granted under the 2015 Plan that expire, lapse unexercised or are terminated, exchanged for cash, surrendered, repurchased, canceled without having been fully exercised, or forfeited become available for issuance under the 2018 Plan.

The exercise price for share options granted under the 2015 Plan was determined by the Company’s board of directors. All incentive share options granted to any person possessing 10% or less of the total combined voting power of all classes of shares could not have an exercise price of less than 100% of the fair market value of the Class A ordinary shares on the grant date. All incentive share options granted to any person possessing more than 10% of the total combined voting power of all classes of shares could not have an exercise price of less than 110% of the fair market value of the Class A ordinary shares on the grant date. The option term for incentive share options could not be greater than 10 years. Incentive share options granted to persons possessing more than 10% of the total combined voting power of all classes of shares could not have an option term of greater than five years. The vesting period for equity-based awards was determined by the board of directors, which was generally four tosix years. For awards granted to employees and non-employees with four year vesting terms,25% of the option vests on the first anniversary of the grant date and the remaining shares vest equally each month forthree years thereafter. For awards granted to employees withsix year vesting terms,16% of the option vests on the first anniversary of the grant date and the remaining shares vest based on a predetermined vesting schedule forfive years thereafter.

2018 Employee Share Purchase Plan

In May 2018, the Company’s board of directors and shareholders approved the 2018 Employee Share Purchase Plan (the “2018 ESPP”), which became effective on May 23, 2018. A total of 670,000 Class A ordinary shares were initially reserved for issuance under the 2018 ESPP. The number of Class A ordinary shares that may be issued under the 2018 ESPP automatically increases on each January 1, beginning in 2019 and continuing for each fiscal year until, and including, the fiscal year ending December 31, 2028, equal to the lesser of (1)1% of the Class A ordinary shares outstanding (on an as-converted basis) on the final day of the immediately preceding calendar year and (2) a smaller number of Class A ordinary shares determined by the Company’s board of directors, provided that no more than 6,420,000 Class A ordinary shares may be issued under the 2018 ESPP. In December 2025, the Company’s board of directors approved an increase as of January 1, 2026 of 110,000 Class A ordinary shares. As of December 31, 2025,690,063 Class A ordinary shares were available for future issuance under the 2018 ESPP.

Restricted Share Units

RSUs represent the right to receive shares of the Company’s Class A ordinary shares upon vesting of the RSUs. The fair value of each RSU award is based on the closing price of the Company’s Class A ordinary shares on the date of grant.

Starting March 2021, the Company granted RSUs with service conditions (“Time-Based RSUs”) to eligible employees. The Time-Based 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 Shares Units

In the second quarter of 2024, the Company began periodically granting performance-based restricted share units to certain employees under the 2018 Plan. The Company granted awards which are earned based upon the achievement of certain specified ARCALYST revenue targets (“Revenue PSUs”), and awards which are earned based upon the Company’s total shareholder return (“TSR”) relative to the performance of the members of the Nasdaq Biotechnology Index (“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 the 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.

The following table summarizes RSU and PSU activity for the year ended December 31, 2025:

RSUs granted in 2024 and 2023 had weighted average grant date fair values of $22.19 and $15.13, respectively. PSUs granted in 2024 had a weighted average grant date fair value of $22.06. No PSUs were granted in 2023.

The total grant date fair values of RSUs that vested during the years ended December 31, 2025, 2024, and 2023 totaled $12,576, $9,495 and $5,635, respectively. No PSUs vested during the years ended December 31, 2025, 2024 and 2023.

Share Options

The following table summarizes option activity for the year ended December 31, 2025:

The aggregate intrinsic value of share options is calculated as the difference between the exercise price of the share options and the fair value of the Company’s ordinary shares for those share options that had exercise prices lower than the fair value of the Company’s ordinary shares.

The total intrinsic value of options exercised during the years ended December 31, 2025, 2024 and 2023, were $63,241, $19,235 and $2,595, respectively. The tax benefit arising on the exercise of stock options was $16,481 for the year ended December 31, 2025. The weighted-average grant-date fair value per share of share options granted during the years ended December 31, 2025, 2024 and 2023 was $17.61, $14.41 and $9.82, respectively.

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.

No PSOs were exercised during the years ended December 31, 2025, 2024 and 2023. The weighted-average grant-date fair value per share of PSOs granted during the years ended December 31, 2025 was $14.17. No PSOs were granted during the years ended December 31, 2024 and 2023.

Option Valuation

The assumptions that the Company used to determine the grant-date fair value of share options granted to employees and directors from the 2018 Plan during the years ended December 31, 2025, 2024 and 2023 were as follows, presented on a weighted-average basis:

During the years ended December 31, 2025, 2024 and 2023, the Company did not grant share options to non-employees.

As of December 31, 2025, total unrecognized compensation cost related to RSUs, Revenue PSUs, TSR PSUs, and share options was $90,372 which is expected to be recognized over a weighted average remaining period of 2.52 years. As of December 31, 2025, total unrecognized compensation cost related to outstanding Development PSUs and PSOs was $9,576 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 income (loss) as follows:

The tax benefit from share-based compensation recognized during the years ended December 31, 2025, 2024 and 2023, were $9,643, $7,976 and $7,433, respectively.

**12.**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”) following termination of the statutory waiting period under the Hart-Scott Rodino Act.

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 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 2024. In 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 remain as of December 31, 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.

Under the Genentech License Agreement, Genentech has the right to assume manufacturing responsibilities for Genentech Licensed Products.

Absent early termination, the Genentech License Agreement will continue until there are no more royalty or other payment obligations owed to the Company. 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 the Biogen Agreement (as defined below).

The Company concluded that Genentech is a customer in this license agreement, and as such, the Genentech License Agreement falls within the scope of the revenue recognition guidance in ASC 606.

Accounting for Genentech License Agreement

As of the Genentech Effective Date, the Company identified the following material promises 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 also evaluated whether certain options outlined within the Genentech License Agreement represented material rights that would give rise to a performance obligation, including the option to purchase additional drug substance, and concluded that none of the options convey a material right to Genentech and therefore are not considered separate performance obligations within the Genentech License Agreement.

The Company assessed the above promises and determined that the exclusive license for vixarelimab is reflective of a vendor-customer relationship and therefore represents a performance obligation. The exclusive license for vixarelimab is considered functional intellectual property and distinct from other promises under the Genentech License Agreement as Genentech can benefit from the license on its own or together with other readily available resources and the license is separately identifiable from the other promises. The initial drug supply and drug product resupply are considered distinct from the exclusive license for vixarelimab as Genentech can benefit from such supply together with the license transferred by the Company at the inception of the Genentech License Agreement. The completion of the Phase 2b clinical trial is considered distinct from the exclusive license for vixarelimab as Genentech can benefit from the data generated by such trial together with such license. Therefore, each represents a separate performance obligation within a contract with a customer at contract inception.

The Company determined the transaction price at the inception of the Genentech License Agreement which consists of the $80,000 upfront payment. The Company determined that the $20,000 variable consideration related to the delivery of the initial drug supply and drug product resupply was no longer constrained during the fourth quarter of 2022, as the Company determined that it could assert it was not probable that a significant reversal in the amount of cumulative revenue recognized would occur. The Company met the milestone in 2023 and invoiced Genentech for the related $20,000 payment for the delivery of certain drug material. 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. The Company determined that all other variable considerations related to the future development and regulatory milestones, 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 also determined that it could not assert that it was not probable that a significant reversal in the amount of cumulative revenue recognized would occur. The Company also determined that royalties and sales milestones relate solely to the license 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.

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 (“SSP”) 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 recognizedno collaboration revenue during the year ended December 31, 2025. The Company recognized $5,261 and $37,083 of collaboration revenue during the years ended December 31, 2024 and 2023, respectively, under the Genentech License Agreement related to the license, completed portion of the Phase 2b clinical trial for vixarelimab, and materials delivered. As a result of the $5,000 in development milestones achieved by

Genentech, the Company recognized revenue of $4,989, during the year ended December 31, 2024, related to performance obligations satisfied in prior periods. The remaining revenue was recognized as a result of the completed portion of the Phase 2b clinical trial for vixarelimab. The Company completed its obligation for the Phase 2b clinical trial for vixarelimab during the year ended December 31, 2024. As such, the Company has recognized all revenue allocated to the completion of the Phase 2b clinical trial for vixarelimab performance obligation as of the end of the year ended December 31, 2024.

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 mavrilimumab (each, a “Huadong Licensed Product” and together, the “Huadong Licensed Products”)in 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 the Huadong Licensed Products 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. The ARCALYST Huadong Collaboration Agreement remains in effect.

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. The Company will be eligible to receive up to approximately $50,000 in contingent sales-based milestone payments for ARCALYST, all of which remain as of December 31, 2025. Due to its termination, the Company does not expect to receive any future payments under the mavrilimumab Huadong Collaboration Agreement. 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 ARCALYST 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.

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

The Company 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 the Company 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, the Company may terminate the ARCALYST Huadong Collaboration Agreement if Huadong or its affiliates or sublicensees challenges the scope, validity, or enforceability of the Company’s patent rights being licensed to Huadong. If Huadong and its affiliates do not conduct any material development or commercialization activities with respect to ARCALYST in the People’s Republic of China for a continuous period of longer thansix months, then, subject to certain exceptions, the Company 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, with respect to the applicable Huadong Licensed Product in such regions.

The Company concluded that Huadong is a customer in these Huadong Collaboration Agreements, and as such, each Huadong Collaboration Agreement falls within the scope of the revenue recognition guidance in ASC 606. 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 Mavrilimumab Huadong Collaboration Agreement

As of the Effective Date, the Company identified the following material promises 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 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. Due to the termination of the mavrilimumab Huadong Collaboration Agreement in April 2025, the Company will not recognize any additional revenue from that agreement.

Accounting for ARCALYST Huadong Collaboration Agreement

As of the Effective Date, the Company identified the following material promises in the ARCALYST Huadong Collaboration Agreement that were evaluated: delivery of (i) exclusive license for ARCALYST in the Huadong Territory; (ii) clinical manufacturing supply of certain materials for ARCALYST products in the Huadong Territory; and (iii) commercial manufacturing supply of certain material for ARCALYST products in the Huadong Territory.

The Company also evaluated whether certain options outlined within the ARCALYST Huadong Collaboration Agreement represented material rights that would give rise to a performance obligation and concluded that none of the

options convey a material right to Huadong and therefore are not considered separate performance obligations within the ARCALYST Huadong Collaboration Agreement.

The Company assessed the above promises and determined that there isone combined performance obligation for 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.

As noted above, the Company identified a single combined performance obligation in the ARCALYST Huadong Collaboration Agreement consisting of the exclusive license for ARCALYST and clinical and commercial manufacturing obligations for ARCALYST products in the Huadong Territory. The Company recognizes revenue for the combined performance obligation consisting of the 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 hasnot recognized any revenue under the ARCALYST Huadong Collaboration Agreement for the years ended December 31, 2025 and 2023 as there wereno deliveries of materials under the ARCALYST Huadong Collaboration Agreement. The Company recognized $189 of the transaction price in collaboration revenue during the year ended December 31, 2024, under the ARCALYST Huadong Collaboration Agreement related to materials delivered. As of December 31, 2025, $31,811 is recorded in non-current deferred revenue, based upon timing of anticipated future shipments.

The following tables summarizes the Company’s contract assets and contract liabilities in connection with license and collaboration agreements for the years ended December 31, 2025 and 2024:** **

13. 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 to 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.

In exchange for these rights, the Company made an upfront payment to Biogen of $11,500 and a technology transfer payment of $500. The Company accounted for the acquisition of technology as an asset acquisition because it did not meet the definition of a business. The Company recorded the upfront payment and technology transfer payment as research and development expense in the consolidated statement of operations and comprehensive income (loss) because the acquired technology represented in-process research and development and had no alternative future use.

Under the Biogen Agreement, the Company is obligated to make milestone 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 December 31, 2025. Additionally, the Company could be obligated to make up to an aggregate of up to $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 of $150 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).

In July 2017, the Company and Biogen entered into Amendment No. 1 to the Biogen Agreement, which clarified the scope of the antibodies subject to the Biogen Agreement.

In August 2022, the Company entered into Amendment No. 2 to the Biogen Agreement (the “Second Biogen Amendment”). Pursuant to the terms of the Second Biogen Amendment, commencing on the effective date of the Genentech License Agreement, certain defined terms in the Biogen Agreement were amended, 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, the amendments to the terms of the Biogen Agreement, as set forth in the Second Biogen Amendment, will terminate and 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 years ended December 31, 2025, 2024 and 2023, the Company recorded expenses of $44, $144 and $94 respectively, related to a milestone and the annual maintenance fee in connection with the retained contracts.

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 (also known as KPL-404). 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 years ended December 31, 2025, 2024 and 2023, the Company recorded expenses of $14, $10 and $40, respectively in connection with the BIDMC Agreement.

Regeneron License Agreement

In September 2017, the Company entered into the Regeneron Agreement with 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 CAPS and DIRA in the United States.

The Company has made $32,500 in payments under the Regeneron Agreement in connection with upfront fees and achievement of regulatory milestones, including a $20,000 payment in the first quarter of 2021 in connection with the achievement of a regulatory milestone. The Company accounted for the acquisition of technology as an asset acquisition because it did not meet the definition of a business.

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 years ended December 31, 2025, 2024 and 2023, the Company recognized $229,545, $127,375 and $56,524 respectively, of expenses related to the profit sharing agreement presented within collaboration expenses.

Pursuant to the Regeneron Agreement, in September 2017, the parties entered into a clinical supply agreement under which Regeneron agreed to manufacture product solely for the Company’s use in development activities. Pursuant to the Regeneron Agreement, during the year ended December 31, 2021, the Company entered into a commercial supply agreement under which Regeneron agreed to manufacture product for the Company’s use, including for commercial sales. The commercial supply agreement terminates upon the sooner of the termination of the Regeneron Agreement and the date of completion of the transfer of technology related to the manufacture of ARCALYST. During the year ended December 31, 2023, the Company incurred $1,356 of research and development expense related to the purchase of drug materials under the clinical supply agreement. During the years ended December 31, 2025 and 2024, the Company didnot incur any research and development expense related to the purchase of drug materials under the clinical supply agreement. As of December 31, 2025 and 2024, the Company recorded inventory of $29,071 and $21,246 related to the purchase of commercial product under the commercial supply agreement (see Note 5). As of December 31, 2024, the Company had non-cancelable purchase commitments under the commercial supply agreement (see Note 16).

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 years ended December 31, 2025, 2024 and 2023, the Company didnot record expenses in connection with milestone payments due under the MedImmune Agreement.

14. 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 United Kingdom. Under the previous 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 it 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 United Kingdom 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 remained subject to taxation, if any, in Bermuda for the period of time prior to its liquidation in November 2025. The Company’s wholly owned subsidiary Kiniksa UK, and Kiniksa UK’s wholly owned subsidiaries, Kiniksa Switzerland, Kiniksa Germany, and Kiniksa France are subject to taxation in their respective countries. Certain of the Company’s subsidiaries operate under cost plus intercompany arrangements.

The Company has engaged in a series of intra-entity asset transfers and allocations to contribute assets to its wholly owned Switzerland subsidiary and Kiniksa UK’s Swiss branch office. 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 and the Company expects it will not be subject to tax in the UK. 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, KPL-387 and certain preclinical assets. 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. 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.

On July 4, 2025, new United States tax legislation was signed into law (known as the "One Big Beautiful Bill Act" or "OBBBA") which makes permanent many of the tax provisions enacted in 2017 as part of the Tax Cuts and Jobs Act that were set to expire at the end of 2025. In addition, the OBBBA makes changes to certain United States corporate tax provisions, but many are generally not effective until 2026. The Company continues to assess the impact of the tax provisions of the OBBBA on its consolidated financial statements, the Company currently believes that the tax provisions of the legislation are not expected to have a material impact on its operations.

Income (loss) before benefit (provision) for income taxes consisted of the following:

The components of the Company’s income tax benefit (provision) were as follows:

A reconciliation of the statutory income tax rate of the Company’s effective income tax rate for the year ended December 31, 2025, after the adoption of ASU 2023-09 for 2025 is as follows:

A reconciliation of the statutory income tax rate of the Company’s effective income tax rate for the years ended December 31, 2024 and 2023, prior to the adoption of ASU 2023-09 were as follows:

Net deferred tax assets consisted of the following:

As of December 31, 2025 and 2024, the Company had United States federal research and development tax credit carryforwards of approximately $3,224 and $808 available to reduce future tax liabilities, respectively, which begin to expire in 2045. As of December 31, 2025 and 2024, the Company had state research and development tax credit carryforwards of approximately $869 and $184 respectively, available to reduce future tax liabilities, which can be carried forward indefinitely. As of December 31, 2025 and 2024 the Company had foreign net operating loss (NOL) carryforwards of $106,244 and $66,990 respectively, available to reduce future tax liabilities. As of December 31, 2025 and 2024 the Company had UK domestic NOLs of $3,119 and $18,382, respectively. The NOLs may be carried forward and utilized, subject to local limitations.

As required by ASC 740 management regularly reassesses the 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.

The valuation allowance increased by $9,749 in 2025 primarily as a result of additional net operating losses of Kiniksa Switzerland. The valuation allowance increased by $610,452 in 2024 primarily as a result of the establishment of the valuation allowance for the Kiniksa Switzerland deferred tax assets which primarily consisted of the tax basis in intellectual property transferred from Bermuda and net operating losses.

In the second quarter of 2023, the Company assessed the valuation allowance on its United States deferred tax assets and considered positive evidence, including cumulative United States income in recent years, primarily related to cost plus intercompany arrangements and expectations regarding future profitability. The Company determined it was more likely than not that its United States deferred tax assets are realizable in the future and released the associated valuation allowance as of June 30, 2023.

In the fourth quarter of 2023, the Company assessed the valuation allowance on its Kiniksa UK deferred tax assets and considered positive and negative evidence, including among other things, the impact of future profitability decreasing in the UK as a result of the allocation of ARCALYST to the Swiss branch office. After assessing both the positive and negative evidence, the Company determined it was more likely than not that a portion of the UK deferred tax assets would not be realized in the future and established a partial valuation allowance on those assets during the year ended December 31, 2023. In 2025, the Company reassessed the valuation allowance on its Kiniksa UK deferred tax assets. After assessing both the positive and negative evidence, including but not limited to future profitability in the UK, the Company determined it was more likely than not that all the UK deferred tax assets would be realized in the future, and released the remaining partial valuation allowance on those assets.

The Company recognized a non-cash deferred tax benefit of $33,788 during the year ended December 31, 2023. This benefit primarily resulted from the step up in basis of intangible assets and inventory received in Switzerland associated with the allocation of ARCALYST to the Swiss branch office and the release of the United States valuation allowance. This was partially offset by the establishment of a partial UK valuation allowance. There areno material deferred tax assets in the jurisdictions outside the United States, UK and Switzerland.

Utilization of the United States federal and state NOLs and research and development tax credits may be subject to substantial annual limitation under Section 382 of the Internal Revenue Code of 1986 due to ownership changes that could occur in the future. These ownership changes may limit the amount of carryforwards that can be utilized annually to offset future taxable income. In general, an ownership change, as defined by Section 382, results from transactions increasing the ownership of certain shareholders or public groups in the shares of a corporation by more than 50% over a three-year period.

The Company recognizes the tax benefit from an uncertain tax position only if it is more-likely-than-not that the tax position will be sustained on examination by taxing authorities, based on the technical merits of the position. The tax benefits recognized in the financial statements from such a position are measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. The amount of unrecognized tax benefits is $32,675, $13,390 and $1,794 as of December 31, 2025, 2024 and 2023, respectively. The net change in 2025, 2024 and 2023 relate to tax positions on the Company’s intellectual property transfers.

As of December 31, 2025, the Company had a liability of $32,675 for unrecognized tax benefits of which, $19,214, if recognized, would reduce the effective tax rate. A roll forward of the Company’s uncertainties in its income tax provision liability is presented below:

The Company’s policy is to record interest and penalties related to income taxes as part of its income tax provision. The Company has accrued $1,117 at year end December 31, 2025 and immaterial interest and penalties on the tax positions during the year ended December 31, 2024 and 2023.

The Company files United States federal income tax returns and income tax returns in various state, local and foreign jurisdictions. The Company’s income tax returns are subject to tax examinations for the tax years ended

December 31, 2022 and subsequent years. His Majesty’s Revenue and Customs (“HMRC”) commenced an examination of the Company’s 2023 and 2024 UK corporate income tax returns. At December 31, 2025, the examination is in the preliminary stages. Based upon available information, the Company does not believe that the audit will result in any adjustment that would result in a material change in the Company’s financial position. To the extent the Company has tax attribute carryforwards, the tax years in which the attribute was generated may still be adjusted upon examination by tax authorities to the extent utilized in a future period.

The following table summarizes income taxes paid net of tax refunds:

15. 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 Note 10). 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 income (loss) per share attributable to ordinary shareholders.

Diluted earnings per share includes the assumed exercise of dilutive options and the assumed issuance of 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 stock options and the average unrecognized compensation expense for unvested share-based compensation awards, would be used to purchase the Company’s ordinary stock at the average market price during the period.

For year ended December 31, 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 for the periods indicated as the effect would be to reduce the net loss per share attributable to ordinary shareholders. Therefore, the weighted average number of ordinary shares outstanding used to calculate both basic and diluted net loss per share 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 net income (loss) per share 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.

16. 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 13).

Manufacturing Commitments

The Company entered into supply agreements with Regeneron to provide both clinical supply and commercial product (see Note 13). In May 2023, the Company signed a letter of intent with Samsung related to its technology transfer of the manufacturing process for ARCALYST drug substance. The Company has additionally entered into agreements with several CDMOs to provide the Company with preclinical and clinical trial materials for its non-ARCALYST assets. As of December 31, 2025, the Company had committed to minimum payments under these agreements totaling $175,704, of which $46,924 are 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 year ended December 31, 2025, the Company recorded and paid$2,500 in research and development expenses because of 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 December 31, 2025, the Company estimates the future cash payments under such Performance Cash Awards to be $23,118 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. The Company has not deemed any of the Performance Cash Award development or regulatory milestones as probable as of December 31, 2025, andno expense has been recognized related to such awards.

Indemnification Agreements

In the ordinary course of business, the Company may provide indemnification of varying scope and terms to vendors, lessors, business partners and other parties with respect to certain matters including, but not limited to, losses arising out of breach of such agreements or from intellectual property infringement claims made by third parties. In addition, the Company has entered into indemnification agreements with members of its board of directors, officers and other key personnel that will require the Company, among other things, to indemnify them against certain liabilities that may arise by reason of their status or service as directors, officers or other key personnel. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is, in many cases, unlimited. To date, the Company has not incurred any material costs as a result of such indemnifications. The Company does not believe that the outcome of any claims under indemnification arrangements will 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 December 31, 2025, 2024 or 2023.

Legal Proceedings

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

**17.**Segment Information and Geographic Data

The Company manages its operations as asingle 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 years ended December 31, 2025, 2024 and 2023:

The following table presents total revenue by geographic region of the customer for years ended December 31, 2025, 2024 and 2023:

The following table presents property and equipment, net by geographic region:

18. Benefit Plans

The Company has established a defined-contribution savings plan under Section 401(k) of the Internal Revenue Code. This plan covers substantially all Kiniksa US employees who meet minimum age and service requirements and allows participants to defer a portion of their annual compensation on a pre-tax basis. The Company provides matching contributions of 100% of the first 3% of each participant’s salary contributed, plus 50% for each of the next 2% contributed. Employees are immediately and fully vested in their own contributions and the Company’s match. During the years ended December 31, 2025, 2024 and 2023, the Company contributed $3,544, $2,923 and $2,305 respectively, to the plan.