Muckle-Wells Syndrome

– ARCALYST® (rilonacept) Q1 2025 net product revenue of $137.8 million, representing 75% year-over-year growth – – ARCALYST 2025 expected net product revenue increased to $590 - $605 million – – KPL-387 Phase 2/3 clinical trial in recurrent pericarditis on track to initiate in mid-2025; Phase 2 data expected in 2H 2026 – – Current operating plan expected to remain cash flow positive on an annual basis – – Conference call and webcast scheduled for 8:30 am ET today – LONDON, April 29, 2025 (GLOBE NEWSWIRE) -- Kiniksa Pharmaceuticals International, plc (Nasdaq: KNSA) (Kiniksa), a biopharmaceutical company developing and commercializing novel therapies for diseases with unmet need, with a focus on cardiovascular indications, today reported first quarter 2025 financial results and recent portfolio execution. “Kiniksa continues to drive strong growth with ARCALYST. In the first quarter of 2025, our robust commercial execution resulted in a meaningful increase in active commercial patients, driven by increases to the prescriber base, longer average total duration of treatment, and changes to Medicare Part D. As a result of strong first quarter performance, we are increasing our expected 2025 ARCALYST net sales to between $590 and $605 million from our previous guidance of between $560 and $580 million,” said Sanj K. Patel, Chairman and Chief Executive Officer of Kiniksa. “Also, we are excited about the potential of KPL-387 to be an additional treatment option for patients by enabling dosing with a single monthly subcutaneous injection in a liquid formulation. We remain on track to initiate the KPL-387 Phase 2/3 recurrent pericarditis trial in the middle of this year.” Portfolio Execution ARCALYST (IL-1α and IL-1β cytokine trap) ARCALYST net product revenue was $137.8 million for the first quarter of 2025. Since launch, more than 3,150 prescribers have written ARCALYST prescriptions for recurrent pericarditis. As of the end of the first quarter of 2025, average total duration of ARCALYST therapy in recurrent pericarditis increased to approximately 30 months, compared to approximately 27 months as of the end of the fourth quarter of 2024. KPL-387 (monoclonal antibody IL-1 receptor antagonist) Pharmacokinetic data from the single ascending dose portion of the Phase 1 study support the development plan for KPL-387; Kiniksa plans to initiate a Phase 2/3 clinical trial in mid-2025. The trial will evaluate KPL-387 in recurrent pericarditis, with a target profile of monthly subcutaneous (SC) dosing in a liquid formulation. The company expects data from the Phase 2 portion of the trial in the second half of 2026. KPL-1161 (Fc-modified monoclonal antibody IL-1 receptor antagonist) Kiniksa is conducting Investigational New Drug (IND)-enabling development activities with a target profile of quarterly SC dosing. Financial Results Total revenue for the first quarter of 2025 was $137.8 million, compared to $79.9 million for the first quarter of 2024. Kiniksa did not record any license and collaboration revenue for the first quarter of 2025, compared to $1.0 million for the first quarter of 2024. Total operating expenses for the first quarter of 2025 were $124.5 million, compared to $96.4 million for the first quarter of 2024. Total operating expenses for the first quarter of 2025 included $43.8 million in collaboration expenses, which are driven by ARCALYST collaboration profitability, compared to $20.8 million for the first quarter of 2024. Total operating expenses for the first quarter of 2025, included $7.7 million in non-cash, share-based compensation expense, compared to $7.2 million for the first quarter of 2024. Net income for the first quarter of 2025 was $8.5 million, compared to a net loss of $17.7 million for the first quarter of 2024. As of March 31, 2025, Kiniksa had $268.3 million of cash, cash equivalents, and short-term investments and no debt. Kiniksa did not record any license and collaboration revenue for the first quarter of 2025, compared to $1.0 million for the first quarter of 2024. Total operating expenses for the first quarter of 2025 included $43.8 million in collaboration expenses, which are driven by ARCALYST collaboration profitability, compared to $20.8 million for the first quarter of 2024. Total operating expenses for the first quarter of 2025, included $7.7 million in non-cash, share-based compensation expense, compared to $7.2 million for the first quarter of 2024. Financial Guidance Kiniksa expects 2025 ARCALYST net product revenue of between $590 million and $605 million, compared to prior guidance of between $560 million and $580 million. Kiniksa expects its current operating plan to remain cash flow positive on an annual basis. Kiniksa continues to monitor potential implications of tariffs on pharmaceuticals imported into the United States. ARCALYST is currently manufactured in the United States by Regeneron Pharmaceuticals. Kiniksa has been in the process of transferring drug substance manufacturing to Samsung Biologics in South Korea and believes any future impact to ARCALYST gross margin would be immaterial, limited only to the cost of drug substance imported into the United States. ARCALYST is currently manufactured in the United States by Regeneron Pharmaceuticals. Kiniksa has been in the process of transferring drug substance manufacturing to Samsung Biologics in South Korea and believes any future impact to ARCALYST gross margin would be immaterial, limited only to the cost of drug substance imported into the United States. Conference Call Information Kiniksa will host a conference call and webcast at 8:30 a.m. Eastern Time on Tuesday, April 29, 2025, to discuss first quarter 2025 financial results and recent portfolio execution. Individuals interested in participating in the call via telephone may register here. Upon registration, all telephone participants will receive a confirmation email detailing how to join the conference call, including the dial-in number along with a unique passcode and registrant ID that can be used to access the call. To access the webcast, please visit the Investors and Media section of Kiniksa’s website. A replay of the event will also be available on Kiniksa’s website within approximately 48 hours after the event. About Kiniksa Kiniksa is a biopharmaceutical company dedicated to improving the lives of patients suffering from debilitating diseases by discovering, acquiring, developing, and commercializing novel therapies for diseases with unmet need, with a focus on cardiovascular indications. Kiniksa’s portfolio of assets is based on strong biologic rationale or validated mechanisms and offers the potential for differentiation. For more information, please visit www.kiniksa.com. About ARCALYST ARCALYST is a weekly, subcutaneously injected recombinant dimeric fusion protein that blocks interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β) signaling. ARCALYST was discovered by Regeneron Pharmaceuticals, Inc. (Regeneron) and is approved by the U.S. Food and Drug Administration (FDA) for recurrent pericarditis, cryopyrin-associated periodic syndromes (CAPS), including Familial Cold Autoinflammatory Syndrome and Muckle-Wells Syndrome, and deficiency of IL-1 receptor antagonist (DIRA). The FDA granted Breakthrough Therapy designation to ARCALYST for the treatment of recurrent pericarditis in 2019 and Orphan Drug exclusivity to ARCALYST in 2021 for the treatment of recurrent pericarditis and reduction in risk of recurrence in adults and pediatric patients 12 years and older. The European Commission granted Orphan Drug Designation to ARCALYST for the treatment of idiopathic pericarditis in 2021. IMPORTANT SAFETY INFORMATION ABOUT ARCALYST ARCALYST may affect your immune system and can lower the ability of your immune system to fight infections. Serious infections, including life-threatening infections and death, have happened in patients taking ARCALYST. If you have any signs of an infection, call your doctor right away. Treatment with ARCALYST should be stopped if you get a serious infection. You should not begin treatment with ARCALYST if you have an infection or have infections that keep coming back (chronic infection). While taking ARCALYST, do not take other medicines that block interleukin-1, such as Kineret® (anakinra), or medicines that block tumor necrosis factor, such as Enbrel® (etanercept), Humira® (adalimumab), or Remicade® (infliximab), as this may increase your risk of getting a serious infection. Talk with your doctor about your vaccine history. Ask your doctor whether you should receive any vaccines before you begin treatment with ARCALYST. Medicines that affect the immune system may increase the risk of getting cancer. Stop taking ARCALYST and call your doctor or get emergency care right away if you have any symptoms of an allergic reaction. Your doctor will do blood tests to check for changes in your blood cholesterol and triglycerides. Common side effects include injection-site reactions (which may include pain, redness, swelling, itching, bruising, lumps, inflammation, skin rash, blisters, warmth, and bleeding at the injection site), upper respiratory tract infections, joint and muscle aches, rash, ear infection, sore throat, and runny nose. For more information about ARCALYST, talk to your doctor and see the Product Information. About KPL-387 KPL-387 is an independently developed, investigational, fully human immunoglobulin G2 (IgG2) monoclonal antibody that binds human interleukin-1 receptor 1 (IL-1R1), inhibiting the signaling of the cytokines IL-1α and IL-1β. Kiniksa believes KPL-387 could expand the treatment options for recurrent pericarditis patients by enabling dosing with a single monthly SC injection in a liquid formulation. About KPL-1161 KPL-1161 is an independently developed, investigational, Fc-modified IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β, with a target profile of quarterly SC dosing. Kiniksa is currently engaging in IND-enabling development activities for KPL-1161. Forward-Looking Statements This press release contains forward-looking statements. In some cases, you can identify forward looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions, although not all forward-looking statements contain these identifying words. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, statements regarding: our expectation that ARCALYST 2025 net product revenue will be between $590 million and $605 million; our plan to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025, with Phase 2 data expected in the second half of 2026, and that we remain on track to meeting such plan; our expectation that our current operating plan will remain cash flow positive on an annual basis; our target profile of monthly dosing via a single subcutaneous injection in a liquid formulation for KPL-387; the expected impact of tariff policy on our gross margins; our target profile of quarterly dosing for KPL-1161; our beliefs about the mechanisms of our assets and potential impact of their approach; and our belief that our portfolio of assets offers the potential for differentiation. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including without limitation, the following: delays or difficulty in enrollment of patients in, and activation or continuation of sites for, our clinical trials; delays or difficulty in completing our clinical trials as originally designed; potential for changes between final data and any preliminary, interim, top-line or other data from clinical trials; our inability to replicate results from our earlier clinical trials or studies; impact of additional data from us or other companies, including the potential for our data to produce negative, inconclusive or commercially uncompetitive results; potential undesirable side effects caused by our products and product candidates; our inability to demonstrate safety and efficacy to the satisfaction of applicable regulatory authorities; potential for applicable regulatory authorities to not accept our filings, delay or deny approval of any of our product candidates or require additional data or trials to support approval; our reliance on third parties as the sole source of supply of the drug substance and drug product used in our products and product candidates; raw material, important ancillary product and drug substance and/or drug product shortages; our reliance on third parties to conduct research, clinical trials, and/or certain regulatory activities for our product candidates; complications in coordinating requirements, regulations and guidelines of regulatory authorities across jurisdictions for our clinical trials; business development activities and their impact on our financial performance and strategy; changes in our operating plan, business development strategy or funding requirements; existing or new competition; and the impact of global economic policy, including any uncertainty in national and international markets. These and other important factors discussed in our filings with the U.S. Securities and Exchange Commission, including under the caption “Risk Factors” contained therein, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. Except as required by law, we disclaim any intention or obligation to update or revise any forward-looking statements. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. ARCALYST® is a registered trademark of Regeneron Pharmaceuticals, Inc. Every Second Counts! ® Kiniksa Investor Contact Jonathan Kirshenbaum (781) 829-3949 jkirshenbaum@kiniksa.com Kiniksa Media Contact Tyler Gagnon (781) 431-9100 tgagnon@kiniksa.com

– ARCALYST® (rilonacept) Q4 2024 and full year 2024 net product revenue of $122.5 million and $417.0 million, respectively –– ARCALYST 2025 net product revenue expected to be $560 - $580 million –– KPL-387 Phase 2/3 clinical trial in recurrent pericarditis expected to initiate in mid-2025; Phase 2 data expected in 2H 2026 –– Abiprubart development in Sjögren’s Disease to be discontinued –– Current operating plan expected to remain cash flow positive on an annual basis –– Conference call and webcast scheduled for 8:30 am ET today – LONDON, Feb. 25, 2025 (GLOBE NEWSWIRE) -- Kiniksa Pharmaceuticals International, plc (Nasdaq: KNSA) (Kiniksa), a biopharmaceutical company developing and commercializing novel therapies for diseases with unmet need, with a focus on cardiovascular indications, today reported fourth quarter and full year 2024 financial results and recent portfolio execution. “Strong commercial execution in 2024 resulted in 79% year-over-year ARCALYST sales growth to $417.0 million. We believe substantial opportunity remains for ARCALYST, and expect 2025 sales of between $560 and $580 million,” said Sanj K. Patel, Chairman and Chief Executive Officer of Kiniksa. “Today, we are excited to announce the development program for KPL-387, which we believe could expand the treatment options for recurrent pericarditis patients by enabling a single monthly subcutaneous injection in a liquid formulation. We have interacted with the FDA and plan to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025. In line with our prioritization of cardiovascular indications, we plan to discontinue the development of abiprubart in Sjögren’s Disease. On behalf of our entire organization, I would like to thank the patients, caregivers, and investigators who contributed to our study.” Corporate Update Kiniksa continues to focus development on diseases with unmet need, prioritizing cardiovascular indications. Kiniksa announced today the development of KPL-387 in recurrent pericarditis, with a target profile of monthly subcutaneous (SC) dosing. KPL-387 is a fully human immunoglobulin G2 (IgG2) monoclonal antibody that binds human interleukin-1 receptor 1 (IL-1R1), inhibiting the signaling of the cytokines interleukin-1α (IL-1α) and interleukin-1β (IL-1β). Kiniksa announced today that it is advancing KPL-1161 towards clinical development with a target profile of quarterly SC dosing. KPL-1161 is an Fc-modified IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β. Kiniksa announced today that it plans to discontinue abiprubart development in Sjögren’s Disease. The company will explore strategic alternatives for the asset. Kiniksa announced today that it has exercised its right to terminate its exclusive license agreement for mavrilimumab with MedImmune. Kiniksa announced today the development of KPL-387 in recurrent pericarditis, with a target profile of monthly subcutaneous (SC) dosing. KPL-387 is a fully human immunoglobulin G2 (IgG2) monoclonal antibody that binds human interleukin-1 receptor 1 (IL-1R1), inhibiting the signaling of the cytokines interleukin-1α (IL-1α) and interleukin-1β (IL-1β). Kiniksa announced today that it is advancing KPL-1161 towards clinical development with a target profile of quarterly SC dosing. KPL-1161 is an Fc-modified IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β. Kiniksa announced today that it plans to discontinue abiprubart development in Sjögren’s Disease. The company will explore strategic alternatives for the asset. Kiniksa announced today that it has exercised its right to terminate its exclusive license agreement for mavrilimumab with MedImmune. Portfolio Execution ARCALYST (IL-1α and IL-1β cytokine trap) ARCALYST net product revenue was $122.5 million and $417.0 million for the fourth quarter and full year 2024, respectively. Since launch, more than 2,850 prescribers have written ARCALYST prescriptions for recurrent pericarditis. As of the end of the fourth quarter of 2024, average total duration of ARCALYST therapy in recurrent pericarditis was approximately 27 months. As of the end of the fourth quarter of 2024, approximately 13% of the target 14,000 multiple-recurrence patients were actively on ARCALYST treatment. KPL-387 (monoclonal antibody IL-1 receptor antagonist) Kiniksa is conducting a single ascending dose (SAD) and multiple ascending dose Phase 1 clinical trial of KPL-387 in healthy volunteers. Topline data from the SAD portion of the Phase 1 trial support potential monthly SC dosing in recurrent pericarditis. Kiniksa has interacted with the U.S. Food and Drug Administration (FDA) and expects to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025, with Phase 2 data expected in the second half of 2026. Topline data from the SAD portion of the Phase 1 trial support potential monthly SC dosing in recurrent pericarditis. KPL-1161 (Fc-modified monoclonal antibody IL-1 receptor antagonist) Kiniksa is conducting Investigational New Drug (IND)-enabling development activities with a target profile of quarterly SC dosing. Financial Results Total revenue for the fourth quarter of 2024 was $122.5 million, compared to $83.4 million for the fourth quarter of 2023. Total revenue for the full year 2024 was $423.2 million, compared to $270.3 million for the full year 2023. Total revenue for the fourth quarter of 2024 did not include any license and collaboration revenue, compared to $12.2 million for the fourth quarter of 2023. Total revenue for the full year 2024 included $6.2 million in license and collaboration revenue, compared to $37.1 million for the full year 2023. Total operating expenses for the fourth quarter of 2024 were $141.8 million, compared to $83.3 million for the fourth quarter of 2023. Total operating expenses for the full year 2024 were $468.9 million, compared to $295.5 million for the full year 2023. Total operating expenses for the fourth quarter of 2024 included $48.2 million in collaboration expenses, which are driven by ARCALYST collaboration profitability, compared to $16.9 million for the fourth quarter of 2023. Total operating expenses for the full year 2024 included $128.3 million in collaboration expenses, compared to $56.5 million for the full year 2023. Total operating expenses for the fourth quarter of 2024 included $8.3 million in non-cash, share-based compensation expense, compared to $7.8 million for the fourth quarter of 2023. Total operating expenses for the full year 2024 included $30.7 million in non-cash, share-based compensation expense, compared to $27.1 million for the full year 2023. Net loss for the fourth quarter of 2024 was $8.9 million, compared to a net income of $25.2 million for the fourth quarter of 2023. Net loss for the full year 2024 was $43.2 million, compared to net income of $14.1 million for the full year 2023. Net loss for the fourth quarter of 2024 included a tax benefit of $8.1 million, compared to a tax benefit of $22.8 million for the fourth quarter of 2023, both primarily due to the treatment of non-cash deferred tax assets. Net loss for the full year 2024 included a tax expense of $7.0 million, compared to a tax benefit of $30.7 million for the full year 2023, both primarily due to the treatment of non-cash deferred tax assets. As of December 31, 2024, Kiniksa had $243.6 million of cash, cash equivalents, and short-term investments and no debt, compared to $206.4 million as of December 31, 2023. Total revenue for the fourth quarter of 2024 did not include any license and collaboration revenue, compared to $12.2 million for the fourth quarter of 2023. Total revenue for the full year 2024 included $6.2 million in license and collaboration revenue, compared to $37.1 million for the full year 2023. Total operating expenses for the fourth quarter of 2024 included $48.2 million in collaboration expenses, which are driven by ARCALYST collaboration profitability, compared to $16.9 million for the fourth quarter of 2023. Total operating expenses for the full year 2024 included $128.3 million in collaboration expenses, compared to $56.5 million for the full year 2023. Total operating expenses for the fourth quarter of 2024 included $8.3 million in non-cash, share-based compensation expense, compared to $7.8 million for the fourth quarter of 2023. Total operating expenses for the full year 2024 included $30.7 million in non-cash, share-based compensation expense, compared to $27.1 million for the full year 2023. Net loss for the fourth quarter of 2024 included a tax benefit of $8.1 million, compared to a tax benefit of $22.8 million for the fourth quarter of 2023, both primarily due to the treatment of non-cash deferred tax assets. Net loss for the full year 2024 included a tax expense of $7.0 million, compared to a tax benefit of $30.7 million for the full year 2023, both primarily due to the treatment of non-cash deferred tax assets. Financial Guidance Kiniksa expects 2025 ARCALYST net product revenue of between $560 million and $580 million. Kiniksa expects its current operating plan to remain cash flow positive on an annual basis. Conference Call Information Kiniksa will host a conference call and webcast at 8:30 a.m. Eastern Time on Tuesday, February 25, 2025, to discuss fourth quarter and full year 2024 financial results and to provide a corporate update. Individuals interested in participating in the call via telephone may register here. Upon registration, all telephone participants will receive a confirmation email detailing how to join the conference call, including the dial-in number along with a unique passcode and registrant ID that can be used to access the call. To access the webcast, please visit the Investors and Media section of Kiniksa’s website. A replay of the event will also be available on Kiniksa’s website within approximately 48 hours after the event. About KiniksaKiniksa is a biopharmaceutical company dedicated to improving the lives of patients suffering from debilitating diseases by discovering, acquiring, developing, and commercializing novel therapies for diseases with unmet need, with a focus on cardiovascular indications. Kiniksa’s portfolio of assets is based on strong biologic rationale or validated mechanisms and offers the potential for differentiation. For more information, please visit www.kiniksa.com. About ARCALYSTARCALYST is a weekly, subcutaneously injected recombinant dimeric fusion protein that blocks interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β) signaling. ARCALYST was discovered by Regeneron Pharmaceuticals, Inc. (Regeneron) and is approved by the U.S. Food and Drug Administration (FDA) for the treatment of recurrent pericarditis (RP) and reduction in risk of recurrence in adults and children 12 years and older. ARCALYST is also approved by the FDA for the treatment of Cryopyrin-Associated Periodic Syndromes (CAPS), including Familial Cold Autoinflammatory Syndrome (FCAS) and Muckle-Wells Syndrome (MWS) in adults and children 12 years and older, and the maintenance of remission of Deficiency of Interleukin-1 Receptor Antagonist (DIRA) in adults and pediatric patients weighing 10 kg or more. The FDA granted Orphan Drug Exclusivity to ARCALYST upon its approval for recurrent pericarditis in 2021. The European Commission granted Orphan Drug Designation to ARCALYST for the treatment of idiopathic pericarditis in 2021. IMPORTANT SAFETY INFORMATION ABOUT ARCALYST ARCALYST may affect your immune system and can lower the ability of your immune system to fight infections. Serious infections, including life-threatening infections and death, have happened in patients taking ARCALYST. If you have any signs of an infection, call your doctor right away. Treatment with ARCALYST should be stopped if you get a serious infection. You should not begin treatment with ARCALYST if you have an infection or have infections that keep coming back (chronic infection). While taking ARCALYST, do not take other medicines that block interleukin-1, such as Kineret® (anakinra), or medicines that block tumor necrosis factor, such as Enbrel® (etanercept), Humira® (adalimumab), or Remicade® (infliximab), as this may increase your risk of getting a serious infection. Talk with your doctor about your vaccine history. Ask your doctor whether you should receive any vaccines before you begin treatment with ARCALYST. Medicines that affect the immune system may increase the risk of getting cancer. Stop taking ARCALYST and call your doctor or get emergency care right away if you have any symptoms of an allergic reaction. Your doctor will do blood tests to check for changes in your blood cholesterol and triglycerides. Common side effects include injection-site reactions (which may include pain, redness, swelling, itching, bruising, lumps, inflammation, skin rash, blisters, warmth, and bleeding at the injection site), upper respiratory tract infections, joint and muscle aches, rash, ear infection, sore throat, and runny nose. For more information about ARCALYST, talk to your doctor and see the Product Information. About KPL-387KPL-387 is an independently developed, investigational, fully human IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β. Kiniksa believes KPL-387 could expand the treatment options for recurrent pericarditis patients by enabling dosing with a single monthly SC injection in a liquid formulation. About KPL-1161KPL-1161 is an independently developed, investigational, Fc-modified IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β, with a target profile of quarterly SC dosing. Kiniksa is currently engaging in IND-enabling development activities for KPL-1161. About AbiprubartAbiprubart is an investigational humanized monoclonal antibody that binds to CD40 and is designed to inhibit the CD40-CD154 (CD40 ligand) interaction, a key T-cell co-stimulatory signal critical for B-cell maturation and immunoglobulin class switching and Type 1 immune responses. Kiniksa believes disrupting the CD40-CD154 co-stimulatory interaction is an attractive approach to addressing multiple autoimmune disease pathologies. Forward-Looking Statements This press release contains forward-looking statements. In some cases, you can identify forward looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions, although not all forward-looking statements contain these identifying words. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, statements regarding: our belief that substantial opportunity remains for ARCALYST and our expectation that ARCALYST 2025 net product revenue will be between $560 million and $580 million; our plan to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025, with Phase 2 data expected in the second half of 2026; our plan to discontinue abiprubart development in Sjögren’s Disease and explore strategic alternatives for the asset; our expectation that our current operating plan will remain cash flow positive on an annual basis; our plan to focus development on diseases with unmet need, prioritizing cardiovascular indications; our belief that KPL-387 could expand the treatment options for recurrent pericarditis patients by enabling a single monthly SC injection in a liquid formulation; our target profile of monthly and quarterly dosing for KPL-387 and KPL-1161, respectively; our beliefs about the mechanisms of our assets and potential impact of their approach; and our belief that our portfolio of assets offers the potential for differentiation. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including without limitation, the following: delays or difficulty in enrollment of patients in, and activation or continuation of sites for, our clinical trials; delays or difficulty in completing our clinical trials as originally designed; potential for changes between final data and any preliminary, interim, top-line or other data from clinical trials; our inability to replicate results from our earlier clinical trials or studies; impact of additional data from us or other companies, including the potential for our data to produce negative, inconclusive or commercially uncompetitive results; potential undesirable side effects caused by our products and product candidates; our inability to demonstrate safety and efficacy to the satisfaction of applicable regulatory authorities; potential for applicable regulatory authorities to not accept our filings, delay or deny approval of any of our product candidates or require additional data or trials to support approval; our reliance on third parties as the sole source of supply of the drug substance and drug product used in our products and product candidates; raw material, important ancillary product and drug substance and/or drug product shortages; our reliance on third parties to conduct research, clinical trials, and/or certain regulatory activities for our product candidates; complications in coordinating requirements, regulations and guidelines of regulatory authorities across jurisdictions for our clinical trials; business development activities and their impact on our financial performance and strategy; changes in our operating plan, business development strategy or funding requirements; and existing or new competition. These and other important factors discussed in our filings with the U.S. Securities and Exchange Commission, including under the caption “Risk Factors” contained therein, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. Except as required by law, we disclaim any intention or obligation to update or revise any forward-looking statements. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. ARCALYST® is a registered trademark of Regeneron Pharmaceuticals, Inc. Every Second Counts! ® Kiniksa Investor ContactJonathan Kirshenbaum(781) 829-3949jkirshenbaum@kiniksa.com Kiniksa Media ContactTyler Gagnon (781) 431-9100tgagnon@kiniksa.com

– Kiniksa plans to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025 – – KPL-387 Phase 1 single ascending dose data support potential monthly dosing – – Kiniksa continues to focus development on diseases with unmet need, prioritizing cardiovascular indications – – Kiniksa to discontinue abiprubart development in Sjögren’s Disease – LONDON, Feb. 25, 2025 (GLOBE NEWSWIRE) -- Kiniksa Pharmaceuticals International, plc (Nasdaq: KNSA) (Kiniksa), a biopharmaceutical company developing and commercializing novel therapies for diseases with unmet need, with a focus on cardiovascular indications, today announced the development program for KPL-387 in recurrent pericarditis and provided an update on its corporate strategy. KPL-387 is an independently developed monoclonal antibody that binds human interleukin-1 receptor 1 (IL-1R1), inhibiting the signaling activity of the cytokines interleukin-1α (IL-1α) and interleukin-1β (IL-1β). “Through the successful development and commercialization of ARCALYST, Kiniksa has helped thousands of patients suffering from recurrent pericarditis. Since the launch in 2021, we have generated over $800 million in product revenue and have become cash flow positive on an annual basis. We plan to further increase our penetration into the recurrent pericarditis population with ARCALYST,” said Sanj K. Patel, Chairman and Chief Executive Officer of Kiniksa. “We also continue to focus development on novel therapies for diseases with unmet need, prioritizing cardiovascular indications. Today, we are excited to extend our leadership in the recurrent pericarditis market through the development of KPL-387. We believe KPL-387 could expand the treatment options for recurrent pericarditis patients by providing a single monthly subcutaneous injection in a liquid formulation.” “KPL-387 could provide a meaningful addition to the therapeutic options available to patients suffering from recurrent pericarditis. Data generated from the single ascending dose portion of the ongoing Phase 1 study support our belief that KPL-387 could enable dosing with a single monthly subcutaneous injection in a liquid formulation,” said John F. Paolini, M.D., Ph.D., FACC, Chief Medical Officer of Kiniksa. “We have interacted with the FDA, and we plan to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025, with Phase 2 data expected in the second half of 2026.” Corporate Update Kiniksa continues to focus development on diseases with unmet need, prioritizing cardiovascular indications. Kiniksa is developing KPL-387, a fully human immunoglobulin G2 (IgG2) monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β, in recurrent pericarditis with a target profile of monthly subcutaneous (SC) dosing. Kiniksa is conducting a single ascending dose (SAD) and multiple ascending dose Phase 1 clinical trial of KPL-387 in healthy volunteers. Topline data from the SAD portion of the Phase 1 trial of KPL-387 support potential monthly SC dosing in recurrent pericarditis. Kiniksa has interacted with the U.S. Food and Drug Administration (FDA) and expects to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025, with Phase 2 data expected in the second half of 2026. Kiniksa is advancing KPL-1161, an Fc-modified IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β, towards clinical development with a target profile of quarterly SC dosing. Kiniksa plans to discontinue the development of abiprubart in Sjögren’s Disease. The company will explore strategic alternatives for the asset. Kiniksa has exercised its right to terminate its exclusive license agreement for mavrilimumab with MedImmune. Kiniksa is conducting a single ascending dose (SAD) and multiple ascending dose Phase 1 clinical trial of KPL-387 in healthy volunteers. Topline data from the SAD portion of the Phase 1 trial of KPL-387 support potential monthly SC dosing in recurrent pericarditis. Kiniksa has interacted with the U.S. Food and Drug Administration (FDA) and expects to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025, with Phase 2 data expected in the second half of 2026. Topline data from the SAD portion of the Phase 1 trial of KPL-387 support potential monthly SC dosing in recurrent pericarditis. About KiniksaKiniksa is a biopharmaceutical company dedicated to improving the lives of patients suffering from debilitating diseases by discovering, acquiring, developing, and commercializing novel therapies for diseases with unmet need, with a focus on cardiovascular indications. Kiniksa’s portfolio of assets is based on strong biologic rationale or validated mechanisms and offers the potential for differentiation. For more information, please visit www.kiniksa.com. About ARCALYSTARCALYST® (rilonacept) is a weekly, subcutaneously injected recombinant dimeric fusion protein that blocks interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β) signaling. ARCALYST was discovered by Regeneron Pharmaceuticals, Inc. (Regeneron) and is approved by the U.S. Food and Drug Administration (FDA) for the treatment of recurrent pericarditis (RP) and reduction in risk of recurrence in adults and children 12 years and older. ARCALYST is also approved by the FDA for the treatment of Cryopyrin-Associated Periodic Syndromes (CAPS), including Familial Cold Autoinflammatory Syndrome (FCAS) and Muckle-Wells Syndrome (MWS) in adults and children 12 years and older, and the maintenance of remission of Deficiency of Interleukin-1 Receptor Antagonist (DIRA) in adults and pediatric patients weighing 10 kg or more. The FDA granted Orphan Drug Exclusivity to ARCALYST upon its approval for recurrent pericarditis in 2021. The European Commission granted Orphan Drug Designation to ARCALYST for the treatment of idiopathic pericarditis in 2021. IMPORTANT SAFETY INFORMATION ABOUT ARCALYST ARCALYST may affect your immune system and can lower the ability of your immune system to fight infections. Serious infections, including life-threatening infections and death, have happened in patients taking ARCALYST. If you have any signs of an infection, call your doctor right away. Treatment with ARCALYST should be stopped if you get a serious infection. You should not begin treatment with ARCALYST if you have an infection or have infections that keep coming back (chronic infection). While taking ARCALYST, do not take other medicines that block interleukin-1, such as Kineret® (anakinra), or medicines that block tumor necrosis factor, such as Enbrel® (etanercept), Humira® (adalimumab), or Remicade® (infliximab), as this may increase your risk of getting a serious infection. Talk with your doctor about your vaccine history. Ask your doctor whether you should receive any vaccines before you begin treatment with ARCALYST. Medicines that affect the immune system may increase the risk of getting cancer. Stop taking ARCALYST and call your doctor or get emergency care right away if you have any symptoms of an allergic reaction. Your doctor will do blood tests to check for changes in your blood cholesterol and triglycerides. Common side effects include injection-site reactions (which may include pain, redness, swelling, itching, bruising, lumps, inflammation, skin rash, blisters, warmth, and bleeding at the injection site), upper respiratory tract infections, joint and muscle aches, rash, ear infection, sore throat, and runny nose. For more information about ARCALYST, talk to your doctor and see the Product Information. About KPL-387KPL-387 is an independently developed, investigational, fully human IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β. Kiniksa believes KPL-387 could expand the treatment options for recurrent pericarditis patients by enabling dosing with a single monthly SC injection in a liquid formulation. About KPL-1161KPL-1161 is an independently developed, investigational, Fc-modified IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1α and IL-1β, with a target profile of quarterly SC dosing. Kiniksa is currently engaging in IND-enabling development activities for KPL-1161. About AbiprubartAbiprubart is an investigational humanized monoclonal antibody that binds to CD40 and is designed to inhibit the CD40-CD154 (CD40 ligand) interaction, a key T-cell co-stimulatory signal critical for B-cell maturation and immunoglobulin class switching and Type 1 immune responses. Kiniksa believes disrupting the CD40-CD154 co-stimulatory interaction is an attractive approach to addressing multiple autoimmune disease pathologies. Forward-Looking StatementsThis press release contains forward-looking statements. In some cases, you can identify forward- looking statements by terms such as “may,” “will,” “should,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “contemplate,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions, although not all forward-looking statements contain these identifying words. All statements contained in this press release that do not relate to matters of historical fact should be considered forward-looking statements, including without limitation, statements regarding: our plan to initiate a Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis in mid-2025, with Phase 2 data expected in the second half of 2026; our plan to discontinue the development of abiprubart in Sjögren’s Disease and explore strategic alternatives for the asset; our plan to prioritize development in cardiovascular indications; our plan to further increase our penetration into the recurrent pericarditis market with ARCALYST; our belief that KPL-387 could expand the treatment options for recurrent pericarditis patients by providing a single monthly SC injection in a liquid formulation; our target profile of monthly and quarterly SC dosing for KPL-387 and KPL-1161, respectively; our beliefs about the mechanisms of our assets and potential impact of their approach; and our belief that our portfolio of assets offers the potential for differentiation. These forward-looking statements are based on management’s current expectations. These statements are neither promises nor guarantees, but involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements, including without limitation, the following: delays or difficulty in enrollment of patients in, and activation or continuation of sites for, our clinical trials; delays or difficulty in completing our clinical trials as originally designed; potential for changes between final data and any preliminary, interim, top-line or other data from clinical trials; our inability to replicate results from our earlier clinical trials or studies; impact of additional data from us or other companies, including the potential for our data to produce negative, inconclusive or commercially uncompetitive results; potential undesirable side effects caused by our products and product candidates; our inability to demonstrate safety and efficacy to the satisfaction of applicable regulatory authorities; potential for applicable regulatory authorities to not accept our filings, delay or deny approval of any of our product candidates or require additional data or trials to support approval; our reliance on third parties as the sole source of supply of the drug substance and drug product used in our products and product candidates; raw material, important ancillary product and drug substance and/or drug product shortages; our reliance on third parties to conduct research, clinical trials, and/or certain regulatory activities for our product candidates; complications in coordinating requirements, regulations and guidelines of regulatory authorities across jurisdictions for our clinical trials; business development activities and their impact on our financial performance and strategy; changes in our operating plan, business development strategy or funding requirements; and existing or new competition. These and other important factors discussed in our filings with the U.S. Securities and Exchange Commission, including under the caption “Risk Factors” contained therein, could cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. Any such forward-looking statements represent management’s estimates as of the date of this press release. Except as required by law, we disclaim any intention or obligation to update or revise any forward-looking statements. These forward-looking statements should not be relied upon as representing our views as of any date subsequent to the date of this press release. ARCALYST® is a registered trademark of Regeneron Pharmaceuticals, Inc. Every Second Counts!® Kiniksa Investor ContactJonathan Kirshenbaum(781) 829-3949jkirshenbaum@kiniksa.com Kiniksa Media ContactTyler Gagnon (781) 431-9100tgagnon@kiniksa.com