Kiniksa Reports First Quarter 2021 Financial Results and Recent Corporate and Portfolio Activity - ARCALYST (rilonacept) launched as the first and only FDA-approved therapy for recurrent pericarditis - - Mavrilimumab Pha

First Quarter 2021 Financial Results and Recent Corporate and Portfolio Activity

ARCALYST (rilonacept) launched as the first and only FDA-approved therapy for recurrent pericarditis -

Mavrilimumab Phase 2 severe COVID-19 data demonstrated a reduction in mechanical ventilation and death at Day 29; Phase 3 enrollment

- Final KPL-404 Phase 1 data support further development in patients; Phase 2 proof-of-concept trial initiation planned

Cash reserves of approximately $264 million -

- May 4, 2021 - Kiniksa Pharmaceuticals, Ltd. (Nasdaq: KNSA) ("Kiniksa"), a biopharmaceutical company

with a portfolio of assets designed to modulate immunological pathways across a spectrum of diseases, today reported first quarter 2021

financial results and recent corporate and portfolio activity.

"The first quarter was transformational for Kiniksa with the

approval of ARCALYST as the first and only FDA-approved therapy for patients with recurrent pericarditis. We are focused on the launch

of ARCALYST and are confident in our commercialization strategy," said Sanj K. Patel, Chief Executive Officer and Chairman of the

Board of Kiniksa. "Additionally, we are executing across our broader portfolio of immune-modulating assets. We recently reported

positive data for mavrilimumab in severe COVID-19 pneumonia and hyperinflammation and remain engaged with the FDA and other government

agencies to identify pathways for accelerated availability of mavrilimumab as a potential therapeutic option for this patient population.

We also reported positive final Phase 1 data for our potentially best-in-class anti-CD40 program, KPL-404, and plan to initiate a Phase

2 proof-of-concept trial in the second half of 2021."

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

Mavrilimumab (monoclonal antibody inhibitor targeting GM-CSFR )

Vixarelimab (monoclonal antibody inhibitor

of signaling through OSMR )

KPL-404 (monoclonal antibody inhibitor of signaling between CD40

Scientific Conference Presentations

Kiniksa is a biopharmaceutical company focused on discovering, acquiring,

developing and commercializing therapeutic medicines for patients suffering from debilitating diseases with significant unmet medical

need. Kiniksa's portfolio of assets, ARCALYST, mavrilimumab, vixarelimab and KPL-404, are based on strong biologic rationale or

validated mechanisms, target underserved conditions and offer the potential for differentiation. These assets are designed to modulate

immunological pathways across a spectrum of diseases. For more information, please visit www.kiniksa.com.

Important information about ARCALYST Injection

For more information about ARCALYST, talk to your doctor and see

the Product Information.

Mavrilimumab is an investigational fully-human monoclonal

antibody that blocks activity of granulocyte macrophage colony stimulating factor (GM-CSF) by specifically binding to the alpha

subunit of the GM-CSF receptor. Mavrilimumab was dosed in over 550 patients with rheumatoid arthritis through Phase 2b clinical

studies in Europe and achieved prospectively-defined primary endpoints of efficacy and safety. Kiniksa is evaluating

mavrilimumab in GCA, a rare inflammatory disease of medium-to-large arteries. The company's Phase 2 trial in GCA achieved both

the primary and secondary efficacy endpoints with statistical significance. Kiniksa is also evaluating mavrilimumab in severe

COVID-19 pneumonia and hyperinflammation. The FDA granted Orphan Drug designation to mavrilimumab for the treatment of GCA in

Vixarelimab is an investigational fully-human monoclonal antibody that targets oncostatin M 5 receptor beta (OSMR ),

which mediates signaling of interleukin-31 (IL-31) and oncostatin M (OSM), two key cytokines implicated in pruritus, inflammation and

fibrosis. Kiniksa believes vixarelimab to be the only monoclonal antibody in development that targets both pathways simultaneously. Kiniksa's

lead indication for vixarelimab is prurigo nodularis, a chronic inflammatory skin condition characterized by severely pruritic skin nodules.

The FDA granted Breakthrough Therapy designation to vixarelimab for the treatment of pruritus associated with prurigo nodularis in 2020.

KPL-404 is an investigational humanized monoclonal antibody that is designed to inhibit 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 interaction is an attractive approach for multiple autoimmune disease pathologies. Kiniksa owns or controls

the intellectual property related to KPL-404.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning

of the Private Securities Litigation Reform Act of 1995. 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 engaging with the FDA

and other government agencies to identify pathways for the potential accelerated availability of mavrilimumab as a therapeutic option

for severe COVID-19 patients; expected timing of next steps for mavrilimumab, including for giant cell arteritis (GCA), in the second

quarter of 2021; our beliefs about our commercial strategy for ARCALYST; our beliefs about the final data from our Phase 1 clinical trial

of KPL-404 in healthy volunteers ; expected timing and design of clinical trials, including initiating our Phase 2 proof-of-concept trial

of KPL-404 in rheumatoid arthritis in the second half of 2021 and the potential to evaluate KPL-404 across a range of other autoimmune

diseases; our belief that KPL-404 has the potential to address a broad range of autoimmune diseases; our beliefs about the mechanisms

of action of our product candidates and potential impact of their approach, including that vixarelimab is the only monoclonal antibody

in development that targets both interleukin-31 (IL-31) and oncostatin M (OSM) pathways simultaneously and that KPL-404 has the potential

to be a best-in-class monoclonal antibody inhibitor; our belief that all of our product candidates offer the potential for differentiation;

and expectation about our cash reserves funding our current operating plan into 2023.

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; amendments to our clinical trial protocols

initiated by us or required by regulatory authorities; delays or difficulty in completing our clinical trials, including as a result of

the COVID-19 pandemic; potential for changes between final data and any preliminary, interim, top-line or other data from clinical trials

conducted by us or third parties; our inability to replicate in later clinical trials the positive final data 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 or to delay or deny approval of, or emergency use authorization for, any of our product candidates or to require

additional data or trials to support any such approval or authorization; delays, difficulty or inability successfully execute on our commercial

strategy for ARCALYST; our reliance on third parties as the sole source of supply of the drug substance and drug products used in our

products and product candidates and to manufacture our products and product candidates; 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; the impact

of the COVID-19 pandemic and measures taken in response to the pandemic on our business and operations as well as the business and operations

of our manufacturers, CROs upon whom we rely to conduct our clinical trials, and other third parties with whom we conduct business or

otherwise engage, including the FDA and other regulatory authorities; changes in our operating plan and funding requirements; and existing

These and other important factors discussed

under the caption "Risk Factors" in our Annual Report on Form 10-K filed with the Securities and Exchange Commission ("SEC")

on February 25, 2021 and our other reports subsequently filed with the SEC 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. While we may elect to update such forward-looking statements at some point in the future,

we disclaim any obligation to do so, even if subsequent events cause our views to change. 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.

All other trademarks are the property of their respective owners.

Every Second Counts!

Kiniksa Investor and Media Contact

KINIKSA PHARMACEUTICALS, LTD.

CONSOLIDATED STATEMENTS OF OPERATIONS

(In thousands, except share and per share amounts)

KINIKSA PHARMACEUTICALS, LTD.