Kiniksa Pharmaceuticals Reports First Quarter 2025 Financial Results and Recent Portfolio Execution - ARCALYST (rilonacept) Q1 2025 net product revenue of $137.8 million, representing 75% year-over-year growth - - ARCALY

Kiniksa Pharmaceuticals

Reports First Quarter 2025 Financial Results and Recent Portfolio Execution

(rilonacept) Q1 2025 net product revenue of $137.8 million, representing 75% year-over-year growth -

2025 expected net product revenue increased to $590 - $605 million -

Phase 2/3 clinical trial in recurrent pericarditis on track to initiate in mid-2025; Phase 2 data expected in 2H 2026 -

operating plan expected to remain cash flow positive on an annual basis -

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

- April 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 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

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

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

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 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

Kiniksa Media Contact

KINIKSA PHARMACEUTICALS, LTD.

CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share amounts)

KINIKSA PHARMACEUTICALS, LTD.

SELECTED CONSOLIDATED BALANCE SHEET DATA