Kiniksa Pharmaceuticals International (NASDAQ:KNSA) reported fourth-quarter and full-year 2025 results highlighting continued growth for ARCALYST in recurrent pericarditis, a return to profitability, and progress across its clinical pipeline, including its ongoing KPL-387 program and plans to enter the clinic with KPL-1161.
ARCALYST revenue growth and 2026 guidance
CEO Sanj K. Patel said ARCALYST revenue continued to grow as interleukin-1 (IL-1) alpha and beta inhibition expands across the recurrent pericarditis population. Patel said the company has delivered ARCALYST to “thousands of patients” since its 2021 launch, contributing to what he described as a shift in the treatment paradigm.
Moat reiterated Kiniksa’s previously announced 2026 net revenue guidance of $900 million to $920 million. He also noted that the specialty drug sector typically faces seasonal headwinds in the first quarter tied to payer plan changes and co-pay resets. Moat added that first-quarter 2025 benefited from a “one-time bolus” of patients transitioning to commercial therapy associated with Medicare Part D changes under the Inflation Reduction Act.
Commercial execution and prescribing trends
Management attributed ARCALYST’s growth primarily to expanding adoption of IL-1 pathway inhibition as a second-line treatment immediately after failure of NSAIDs and colchicine. Moat pointed to the publication of the 2025 ACC Concise Clinical Guidance, which he said recommends IL-1 pathway inhibition as a second-line approach following failure of NSAIDs and colchicine in recurrent pericarditis patients.
Kiniksa outlined several commercial priorities for 2026, including physician education and marketing initiatives designed to broaden awareness and support earlier use in the disease course. Moat said the company plans to:
- Drive physician awareness of the 2025 ACC guidance
- Advance digital marketing to encourage patients to discuss ARCALYST with physicians
- Use AI and machine learning to target physicians “at the right point in time”
- Explore ways to expand the impact of pericardial disease centers, where prescription growth has outpaced other sites
By the end of 2025, more than 4,150 prescribers had written an ARCALYST prescription, Moat said. Of those, roughly 29% (more than 1,200) had prescribed ARCALYST for two or more recurrent pericarditis patients. Moat also highlighted commercial fundamentals including an average total duration of therapy “approaching three years,” robust payer approval rates, and strong patient adherence.
On market penetration, Moat said penetration in the two-plus recurrence target market rose to approximately 18% at the end of 2025, compared with about 15% mid-year and 13% at the end of 2024. In response to an analyst question, Patel said the company has not commented on peak penetration, while Moat characterized the opportunity as “relatively nascent.” He cited an estimated population of about 14,000 patients with two or more recurrences at the end of 2025, and a larger group of roughly 26,000 patients per year experiencing a first recurrence.
Moat said approximately 20% of ARCALYST prescriptions are written after a first recurrence, reflecting increased use earlier in the disease course. Asked whether the 20/80 split might change, Moat said first-recurrence use has grown over time as physicians become more comfortable with ARCALYST and see long-term patient outcomes, but added that how it evolves “is to be seen.”
On persistence, Moat said the company has not observed “anything meaningfully different” between first-recurrence and two-plus recurrence patients, and emphasized that physicians are increasingly recognizing recurrent pericarditis as a chronic multi-year disease and treating throughout the duration of disease with IL-1 alpha and beta inhibition rather than short-term approaches.
Pipeline updates: KPL-387 and KPL-1161
Patel said Kiniksa initiated its planned phase II/III clinical trial for KPL-387 in recurrent pericarditis in mid-2025 and is continuing to enroll and dose patients in the phase II portion. He said the company remains on track to report phase II data in the second half of 2026. Patel said KPL-387 could potentially expand market penetration by enabling monthly dosing with an auto-injector.
Chief Medical Officer John Paolini said Kiniksa’s interactions with the FDA have been “very productive” and that the company has discussed the integrated development program for KPL-387, including the ongoing phase II work, the planned phase III trial, and long-term extensions. Paolini said those communications have affirmed Kiniksa’s belief that the phase II trial would be “sufficient and pivotal for registration in the U.S.” He added that Kiniksa continues to look for opportunities to move the program faster.
When asked about phase III timing and enrollment dynamics, Paolini noted the study is global, enrolling both in the U.S. and internationally, and that ARCALYST is available for recurrent pericarditis “only in the United States.” He said the company has not provided guidance on phase III initiation and pointed investors to ClinicalTrials.gov and company updates.
On labeling considerations for KPL-387, Paolini said the company is pursuing a program designed to support a similar indication statement to ARCALYST—treatment of recurrent pericarditis and reduction in risk of recurrence—intended to cover patients regardless of prior line of therapy and number of recurrences, provided they meet diagnostic criteria. He noted that, unlike ARCALYST’s recurrent pericarditis label expansion via an sBLA, KPL-387 would be a full BLA program and therefore includes additional early clinical work and larger long-term extensions to support the safety package. He also said the planned phase III pivotal study “bears a remarkable resemblance” to the RHAPSODY study design.
Moat added that KPL-387 is intended to address patient needs through less frequent dosing, streamlined preparation, and patient-friendly administration, including potential auto-injector use. He cited market research indicating about 75% of recurrent pericarditis patients preferred the KPL-387 target product profile compared with other options shown, and that more than 90% of healthcare professionals were “highly likely” to prescribe KPL-387 for new recurrent pericarditis patients.
Separately, Patel said the company plans to be in the clinic with KPL-1161—an Fc-modified IL-1 alpha and beta inhibitor—by the end of 2026. Paolini noted KPL-1161 remains in preclinical development and the company expects to provide more details as it progresses.
Profitability, expenses, and cash position
CFO Mark Ragosa said Kiniksa advanced its commercial business and clinical portfolio in 2025 while maintaining a strong balance sheet. He reported that operating expenses increased year-over-year in both the fourth quarter and full year, driven by higher cost of goods sold associated with ARCALYST growth, increased collaboration expenses aligned with higher ARCALYST collaboration profit, and higher SG&A as the company invested to support ARCALYST commercialization.
Net income was $14.2 million in the fourth quarter of 2025, compared with a net loss of $8.9 million in the prior-year quarter. For the full year, net income was $59.0 million, compared with a net loss of $43.2 million for 2024.
Ragosa also provided detail on ARCALYST collaboration profit, which he said largely drives total collaboration expenses. ARCALYST collaboration profit increased 83% year-over-year to $140.0 million in the fourth quarter and rose 96% to $459.0 million for the full year 2025.
On liquidity, Ragosa said Kiniksa ended 2025 with $414.1 million in cash, representing $170.4 million of net cash generation for the year. He added that the company expects to remain cash-flow positive annually under its current operating plan.
In closing remarks, Patel said the company remains focused on expanding its IL-1 alpha and beta inhibition franchise through ARCALYST growth and advancement of its pipeline, while also pursuing strategic business development.
About Kiniksa Pharmaceuticals International (NASDAQ:KNSA)
Kiniksa Pharmaceuticals International, Inc is a biopharmaceutical company focused on discovering, acquiring and developing therapeutics for patients suffering from lifethreatening and debilitating immune-mediated diseases. Founded in 2013 and headquartered in Lexington, Massachusetts, Kiniksa applies a patient-centric approach to build a diversified portfolio of marketed medicines and clinical-stage candidates targeting inflammation and immunology. The company’s core mission is to address complex conditions with significant unmet medical needs by advancing both novel and differentiated therapies.
The company’s lead marketed product is Ilaris (canakinumab), an interleukin-1β blocker licensed for the treatment of cryopyrin-associated periodic syndromes, systemic juvenile idiopathic arthritis, adult-onset Still’s disease and Schnitzler syndrome.
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