Kiniksa Pharmaceuticals Reports Second Quarter 2025 Financial Results and Recent Portfolio Execution - ARCALYST (rilonacept) Q2 2025 net product revenue of $156.8 million, representing 52% year-over-year growth - - ARCAL

Pharmaceuticals Reports Second Quarter 2025 Financial Results and Recent Portfolio Execution

ARCALYST (rilonacept) Q2 2025 net product revenue of $156.8 million, representing 52% year-over-year growth -

ARCALYST 2025 expected net product revenue increased to $625 - $640 million -

KPL-387 Phase 2/3 clinical trial in recurrent pericarditis initiated; Phase 2 data expected in 2H 2026 -

Cash balance increased by $39.4 million in Q2 2025 to $307.8 million -

Conference call and webcast scheduled for 8:30 am ET today -

July 29, 2025 - 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

second quarter 2025 financial results and recent portfolio execution.

"Our robust commercial performance in the second quarter was

driven by expanding ARCALYST penetration across the recurrent pericarditis population, supported by growth among both new and repeat prescribers.

For 2025, we've raised our ARCALYST net sales guidance to between $625 and $640 million from between $590 and $605 million. This

represents 52% year-over-year growth at the midpoint, highlighting the ongoing strength of the ARCALYST commercialization more than four

years after launch," said Sanj K. Patel, Chairman and Chief Executive Officer of Kiniksa. "In addition, we are excited that

the Phase 2 dose-focusing portion of the pivotal Phase 2/3 clinical trial of KPL-387 in recurrent pericarditis is now recruiting. We expect

data from this part of the study in the second half of 2026 and potential market entry in the 2028/2029 timeframe."

ARCALYST (IL-1 and IL-1 cytokine trap)

KPL-387 (monoclonal antibody IL-1 receptor antagonist)

KPL-1161 (Fc-modified monoclonal antibody IL-1 receptor antagonist)

Conference Call Information

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.

ARCALYST is a weekly, subcutaneously

injected recombinant dimeric fusion protein that blocks interleukin-1 alpha (IL-1 ) and interleukin-1 beta (IL-1 ) 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

For more information

about ARCALYST, talk to your doctor and see the Product Information.

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-1 and IL-1 . 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.

KPL-1161 is an independently

developed, investigational, Fc-modified IgG2 monoclonal antibody that binds IL-1R1, inhibiting the signaling of the cytokines IL-1

and IL-1 , with a target profile of quarterly SC dosing. Kiniksa is currently engaging in IND-enabling development activities for

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 increase to between $625

million and $640 million; our expectation to have data from the Phase 2 dose-focusing portion of our clinical trial of KPL-387 in recurrent

pericarditis in the second half of 2026, and our plan to initiate the pivotal portion of the trial thereafter; our expectation to have

potential market entry of KPL-387 in 2028 or 2029; 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; 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; current and future

healthcare reforms, including those affecting the delivery of or payment for healthcare products and services; 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 & Media Contact

Jonathan Kirshenbaum