Kiniksa Announces New Data from Phase 2 Trial of Mavrilimumab in Giant Cell Arteritis to be Presented at Late-Breaking Abstracts Session of American College of Rheumatology Convergence 2020 - Mavrilimumab reduced time-to

Kiniksa Announces New Data from Phase 2 Trial of Mavrilimumab in Giant Cell Arteritis to be Presented at Late-Breaking Abstracts Session

of American College of Rheumatology Convergence 2020

BERMUDA - October 26, 2020 -

Kiniksa Pharmaceuticals, Ltd. (Nasdaq: KNSA) ("Kiniksa"), a biopharmaceutical company with a pipeline

of assets designed to modulate immunological pathways across a spectrum of diseases, today announced that new data from

the global Phase 2 clinical trial of mavrilimumab in giant cell arteritis (GCA) will be presented at the late-breaking abstracts

session during the American College of Rheumatology (ACR) Convergence 2020. Mavrilimumab is an investigational fully-human monoclonal

antibody that targets granulocyte macrophage colony stimulating factor receptor alpha (GM-CSFR ). Both the primary and secondary

efficacy endpoints achieved statistical significance, and there was a consistent trend of efficacy across the new onset and relapsing/refractory

"There is a significant unmet need for safe and effective

giant cell arteritis therapies. We believe mavrilimumab, with its upstream inhibition of two immune pathways implicated in giant

cell arteritis, has the potential to provide differentiation from current standard of care therapies by addressing the underlying

pathophysiology of the disease," said John F. Paolini, MD, PhD, Chief Medical Officer of Kiniksa. "In the Phase

2 giant cell arteritis trial, mavrilimumab was superior to placebo on the primary and secondary efficacy endpoints of time-to-flare

and sustained remission at Week 26. These data further underscore the potential for mavrilimumab to offer a differentiated treatment option for patients with both relapsing/refractory

disease as well as new onset disease."

Dr. Maria Cid1, a co-principal investigator

for the global Phase 2 trial, will deliver a virtual presentation entitled Mavrilimumab (anti GM-CSF receptor monoclonal

antibody) Reduces Time to Flare and Increases Sustained Remission in a Phase 2 Trial of Patients with Giant Cell Arteritis

at the late-breaking abstracts session (L06 - L11) on Monday, November 9, 2020 at 11:30 a.m. Eastern Time. Dr. Sebastian

Unizony2 is a co-principal investigator.

The Phase 2 trial randomized 70 patients 3:2 to mavrilimumab

150 mg (N=42) or placebo (N=28) biweekly injected subcutaneously, co-administered with a protocol-defined 26-week oral corticosteroid

taper. Patients were stratified by new onset (n=35) or relapsing/refractory (n=35) disease.

The primary efficacy endpoint of time-to-first adjudicated GCA

flare by Week 26 in all treated patients was statistically significant (Hazard Ratio = 0.38, p=0.0263).

The secondary efficacy endpoint of sustained remission at Week

26 in all treated patients was also statistically significant.

While the study was not powered for disease cohorts, there was

a consistent trend of efficacy across the new onset and relapsing/refractory cohorts.

Relapsing/Refractory Cohort

Mavrilimumab was well-tolerated; there were no drug-related

serious adverse events, and the rates of drug-related treatment-emergent adverse events between mavrilimumab recipients and placebo

recipients were similar.

The 12-week washout safety follow-up period is ongoing, and

additional analyses of this Phase 2 trial are planned. Next steps for the development program in GCA will be further informed by

anticipated discussions with the U.S. Food and Drug Administration (FDA).

The abstract is available through the ACR website.

Table 1 as submitted to ACR by the authors for publication and

as referenced in the abstract follows below. The table was inadvertently omitted during the online posting of the abstract.

Table 1: Efficacy at Week 26.

[1] Kaplan-Meier method used to estimate the survival functions

for each treatment arm.

[2] Calculated based on a Cox proportional-hazards

model with treatment as covariate and stratified by randomization strata.

[3] Comparison of KPL-301 and placebo with respect to time to

flare calculated by using a log-rank test and stratified by randomization strata.

[4] Kaplan-Meier Survival Estimates with standard error and

95% CI for each arm.

[5] Two-sided p-value and 95% CI for the difference in sustained

remission between two arms using normal approximation. Placebo arm is the reference.

[6] Calculated based on a Cox proportional-hazards

model with treatment as covariate.

[7] Comparison of KPL-301 and placebo with respect to time to

flare calculated by using a log-rank test.

[8] Subgroup analyses were not powered for significance; nominal

The FDA recently granted Orphan Drug designation to mavrilimumab

for the treatment of GCA.

Kiniksa intends to make the presentation available through

the Science section of its website after the ACR embargo lifts.

Kiniksa is also evaluating mavrilimumab in severe COVID-19 pneumonia

and hyperinflammation and is enrolling the Phase 2 portion of a global, randomized, double-blind, placebo-controlled adaptive design

Phase 2/3 clinical trial. Additionally, the company expects to announce data from a randomized, double-blind, placebo-controlled

investigator-initiated study in the U.S. in the fourth quarter of 2020.

1 Hospital Cl nic, University of Barcelona, Institut

d'Investigacions Biom diques August Pi i Sunyer (IDIBAPS); 2 Massachusetts General Hospital,

About the Global Phase 2 Clinical Trial of Mavrilimumab in

The randomized, double-blind, placebo-controlled, global Phase

2 clinical trial of mavrilimumab in GCA consists of a 6-week screening period, a 26-week double-blind placebo-controlled treatment

period, and a 12-week washout safety follow-up period. Patients age 50 to 85 years with active GCA, confirmed by temporal artery

biopsy and/or imaging, with erythrocyte sedimentation rate (ESR) 30 mm/hour or C-reactive protein (CRP) 1 mg/dL, and

symptoms of GCA within 6 weeks from randomization, were included. All patients were required to have achieved corticosteroid-induced

remission (resolution of symptoms, ESR < 20 mm/hour, CRP < 1 mg/dL) prior to randomization.

About Giant Cell Arteritis

Giant cell arteritis is a

rare chronic inflammatory disease of medium-to-large arteries. Cranial giant cell arteritis typically presents with headache and

jaw claudication as well as constitutional symptoms of fever and fatigue. Acute events can include permanent vision loss from

diminished blood flow to the eye. The large vessel form of giant cell arteritis affects the branches of the aorta supplying the

trunk and limbs. There is currently one FDA-approved treatment for giant cell arteritis as an adjunct to a corticosteroid taper.

Mavrilimumab is an investigational

fully-human monoclonal antibody that targets GM-CSFR . 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's lead indication for mavrilimumab is GCA, a rare inflammatory disease of medium-to-large arteries. Kiniksa is also

evaluating mavrilimumab in COVID-19 pneumonia and hyperinflammation. The FDA granted Orphan Drug designation to mavrilimumab for

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 product candidates, rilonacept, mavrilimumab, vixarelimab and KPL-404,

are based on strong biologic rationale or validated mechanisms, target underserved conditions and offer the potential for differentiation.

These pipeline assets are designed to modulate immunological pathways across a spectrum of diseases. For more information, please

visit www.kiniksa.com.

Forward-Looking Statements

The information contained in 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: mavrilimumab's potential to offer a treatment option for