Is the growth pace for ARCALYST the same in first recurrence and 2+ recurrence patient populations, and does market research suggest changes to the 20:80 ratio?

The percentage of ARCALYST prescriptions for first recurrence patients has grown to around 20%, which is viewed as a positive shift in treatment paradigm. While the future evolution of this ratio is to be seen, physicians are becoming more comfortable prescribing earlier, especially for high-risk first recurrence patients who could benefit within ARCALYST's broad label. “It's around 20% of all ARCALYST prescriptions that seem to be in the first recurrence group at this stage. So we view that as a positive change as we've evolved the treatment paradigm and as physicians get more and more comfortable both with prescribing ARCALYST but also seeing the effect of having their patients on ARCALYST.”

What is the extent of recent FDA interactions for KPL-387/KPL-1161, and are there differences in persistence rates between first recurrence and 2+ recurrence patient populations?

Kiniksa values FDA interactions and has laid out a comprehensive development program for KPL-387, with FDA affirming the Phase II trial's pivotal potential for U.S. registration. KPL-1161 is still preclinical. Regarding persistence, no meaningful differences have been observed between first recurrence and 2+ recurrence patients, as both groups generally suffer from chronic multiyear disease, and physicians are shifting to long-term management with IL-1 inhibition. “The communications that we've had have affirmed, if you will, our belief that the Phase II trial would be sufficient and pivotal for registration in the U.S.”

How is the enrollment curve for KPL-387's Phase III portion, and are there differences in enrolled patient types compared to RHAPSODY?

The KPL-387 study is global, enrolling patients in the U.S. and globally, where ARCALYST is not yet available. The design is straightforward, focusing on recurrent pericarditis patients. Guidance on Phase III initiation has not yet been provided, but the drug is anticipated to reach patients in 2028-2029. The study design is similar to RHAPSODY. “It's important to realize that this is a global study as well. So it's enrolling patients not only in the United States, but also globally. And at this point in time, ARCALYST is available in recurrent pericarditis only in the United States.”

KNSA

Kiniksa Pharmaceuticals (KNSA) Q4 FY25 earnings call: guidance and Q&A

Earnings call· Dec 2025 (Q4 FY25)· Health Care· Feb 24, 2026

Source: earnings call transcript

Executive summary

Kiniksa Pharmaceuticals Q4 FY25 — ARCALYST Drives Strong Revenue Growth and Profitability, Pipeline Advances

Kiniksa Pharmaceuticals delivered robust Q4 and full-year 2025 results, driven by strong ARCALYST revenue growth and expanding adoption in recurrent pericarditis. The company achieved profitability and significant cash generation, enabling continued investment in its commercial infrastructure and advancing its clinical pipeline with KPL-387 and KPL-1161. Management is focused on unlocking the next phase of ARCALYST growth through increased physician awareness and digital marketing, while also preparing for future market expansion with its pipeline assets.

Highlights

ARCALYST product revenue grew 65% year-over-year to $202.1 million in Q4 FY25 and 62% to $677.6 million for the full year 2025.
Net income was $14.2 million in Q4 FY25, compared to a net loss of $8.9 million in Q4 FY24, and $59 million for full year 2025.
ARCALYST collaboration profit grew 83% to $140 million in Q4 FY25 and 96% to $459 million for the full year 2025.
Ended FY25 with a strong cash position of $414.1 million, representing $170.4 million of net cash generation for the year.
KPL-387 Phase II portion of the clinical trial is on track for data readout in H2 2026, and KPL-1161 is expected to be in clinic by end of 2026.

Concerns

Q1 2026 is expected to face seasonal headwinds in the specialty drug sector associated with payer plan changes and co-pay resets.

Guidance & targets

Category	Target	Timeline	Confidence
ARCALYST Net Revenue	$900 million - $920 million high materiality	Full Year 2026 · FY26	High
KPL-387 Phase II Data Readout	Second half of 2026 high materiality	H2 2026 · FY26	High
KPL-1161 Clinic Entry	By the end of 2026 medium materiality	End of 2026 · FY26	High
KPL-387 Launch Timeline	2028-2029 time frame high materiality	2028-2029 · FY28-FY29	Medium

Segment performance

Segment	Revenue	YoY	QoQ	Margin
ARCALYST ARCALYST continues to drive significant revenue growth and profitability, fueled by expanding adoption in recurrent pericarditis. The product has established strong commercial fundamentals, with increasing penetration into the target market and growing utilization earlier in the disease course. The 2025 ACC concise clinical guidance further supports its use as a second-line treatment. Product Revenue Q4 FY25: $202.1 millionProduct Revenue Growth YoY Q4 FY25: 65%Product Revenue Full Year FY25: $677.6 millionProduct Revenue Growth YoY Full Year FY25: 62%Collaboration Profit Q4 FY25: $140 millionCollaboration Profit Growth YoY Q4 FY25: 83%Collaboration Profit Full Year FY25: $459 millionCollaboration Profit Growth YoY Full Year FY25: 96%Total Prescribers: >4,150Repeat Prescribers (2+ patients): >1,200 (29% of total)Penetration into 2+ Recurrence Target Market: ~18% (up from 15% mid-2025 and 13% end-2024)Prescriptions for First Recurrence Patients: ~20% of total ARCALYST prescriptionsAverage Total Duration of Therapy: Approaching 3 yearsPayer Approval Rates: RobustPatient Adherence: Strong	—	—	—	—

KNSA operating KPIs by quarter

KNSA operating KPIs stated on its earnings calls, by fiscal quarter
KPI	This call Dec 2025 Q4 FY25	Mar 2026 Q1 FY26	Jun 2026 Q2 FY26	Change vs prior quarter
Prescribers	4,150+ At the end of 2025, more than 4,150 prescribers had written a prescription for ARCALYST. Source: earnings call transcript	—	5,000+ Approximately 450 additional health care professionals wrote their first ARCALYST prescription in the second quarter, bringing the total prescriber base to more than 5,000 launch to date. Source: earnings call transcript	—
Repeat prescribers	1,200+ Of those, around 29% or more than 1,200 prescribers have written ARCALYST for 2 or more recurrent pericarditis patients. Source: earnings call transcript	~1,320 We also saw growth in the number of health care professionals who became repeat prescribers during Q1, resulting in approximately 1,320 prescribers in total who have now prescribed ARCALYST multiple times. Source: earnings call transcript	—	—

Operating figures the company stated on at least two of the calls shown, checked against each call's transcript. Click a figure to read the sentence. A dash means it was not stated that quarter.

Risks & headwinds

Seasonal headwinds in Q1 Q1 2026

Associated with payer plan changes and co-pay resets

What to watch in Q1 FY26

ARCALYST Q1 Seasonal Headwinds Impact

Next quarter

Current Q1 2026 expected to face seasonal headwinds

Target Quantification of impact on ARCALYST sales

Why it matters

Seasonal headwinds can affect ARCALYST's sales trajectory and overall revenue performance in the short term.

Historically, Q1 faces some seasonal headwinds in the specialty drug sector associated with payer plan changes and co-pay resets.

Find out whether KNSA delivers this. Inve re-checks your case every morning.

Q&A highlights

What is the peak penetration for ARCALYST in the multiple recurrent setting, and how might KPL-387's potential approval affect this?

Management has not commented on peak penetration but believes there is significant growth opportunity for ARCALYST, currently at 18% penetration in the 2+ recurrence market (14,000 patients). The first recurrence market (26,000 patients) represents an even larger opportunity. KPL-387 is designed to expand the market with monthly dosing and auto-injector potential, addressing key patient needs and preferences.

“We announced we're around 18% penetrated into the target population of patients with 2 or more recurrences. That's a 14,000 population at the end of 2025. And that's without taking into account those patients that are earlier on in the disease on their first recurrence, which is a much larger group of patients, around 26,000 patients in any given year.”

asked by Nicholas Lorusso · answered by Ross Moat

2 min read 6 chapters

Detailed narrative

ARCALYST Commercial Performance and Growth Drivers

ARCALYST demonstrated significant commercial success in 2025, with full-year net revenue reaching $677.6 million, a 62% increase over 2024. This growth was primarily driven by expanding adoption of IL-1 alpha and beta inhibition as a second-line treatment for recurrent pericarditis.

The company has established a strong commercial foundation with an average total duration of therapy approaching 3 years, robust payer approval rates, and strong patient adherence. Penetration into the 2-plus recurrence target market increased to approximately 18% by the end of 2025, up from 13% at the end of 2024.

Strategic Investments and Future Growth Initiatives for ARCALYST

Kiniksa has leveraged ARCALYST's profitability to make strategic investments in its commercial infrastructure and digital marketing efforts. In 2026, the focus is on driving further physician awareness of the 2025 ACC concise clinical guidance, which recommends IL-1 pathway inhibition as a second-line approach.

The company is also advancing digital marketing initiatives, utilizing AI and machine learning for physician targeting, and exploring ways to expand the impact of pericardial disease centers, where ARCALYST prescription growth has outpaced other sites.

KPL-387 Development and Market Potential

KPL-387, an internally discovered asset, is currently in the Phase II portion of a Phase II/III clinical trial for recurrent pericarditis, with data expected in the second half of 2026. This asset is designed to address key patient needs with potential monthly dosing via an auto-injector, aiming to expand penetration into the addressable market.

Management believes KPL-387 could extend Kiniksa's leadership in the recurrent pericarditis market, with a target launch timeline in the 2028-2029 timeframe.

KPL-1161 Preclinical Progress

Kiniksa also announced plans to advance KPL-1161, an Fc-modified IL-1 alpha and beta inhibitor, into clinical trials by the end of 2026. This asset represents another internally developed program aimed at further strengthening the company's IL-1 inhibition franchise and addressing unmet patient needs in debilitating diseases.

Financial Strength and Cash Flow Generation

The company reported a strong financial position, ending 2025 with $414.1 million in cash, reflecting $170.4 million of net cash generation for the year. Kiniksa expects to remain cash flow positive on an annual basis under its current operating plan, providing flexibility for R&D investments, advancing its pipeline, and pursuing strategic business development opportunities.

Regulatory Interactions and Clinical Trial Design

Kiniksa has had productive interactions with the FDA regarding KPL-387, affirming that the Phase II trial could be sufficient and pivotal for U.S. registration. The KPL-387 program is designed to support a broad label for recurrent pericarditis, similar to ARCALYST, treating patients regardless of prior therapy or number of recurrences. The company is always looking for opportunities to accelerate development while maintaining rigorous trial design.

Summary of the company's earnings call; see how call summaries are prepared. Not investment advice.