Kiniksa Raises ARCALYST Guidance to $995M as KPL-387 Advances into Pivotal Phase 3 for Recurrent Pericarditis
Key Insights
ARCALYST (rilonacept) generated $243.6 million in Q2 2026 net product revenue, representing approximately 55% year-over-year growth, prompting Kiniksa to raise full-year 2026 guidance to $980–$995 million.
KPL-387 (search) Phase 2 data showed rapid and sustained reductions in pain and inflammation with once-monthly 300 mg subcutaneous dosing, with median time to treatment response of 4.0 days.
The pivotal Phase 3 PASTORALE trial for KPL-387 (search) is now enrolling and dosing patients, with potential commercialization expected in the 2028/2029 timeframe.
Kiniksa Pharmaceuticals reported second quarter 2026 financial results marked by robust commercial growth for ARCALYST and the advancement of its next-generation IL-1 pathway inhibitor KPL-387 (search) into a pivotal Phase 3 trial, the company announced on July 28, 2026.
ARCALYST (rilonacept) net product revenue reached $243.6 million for the second quarter, reflecting approximately 55% year-over-year growth compared to $156.8 million in the same period of 2025. In response, Kiniksa raised its full-year 2026 ARCALYST net sales guidance to between $980 million and $995 million, up from the prior range of $930 million to $945 million.
"In the second quarter, Kiniksa continued to drive growth in new and repeat prescribers of ARCALYST in recurrent pericarditis (search), which led to a meaningful increase in patients on therapy," said Sanj K. Patel, Chairman and Chief Executive Officer of Kiniksa.
ARCALYST Commercial Momentum
As of the end of the second quarter of 2026, approximately 21% of the estimated 14,000 multiple-recurrence patients were actively on ARCALYST treatment. Since launch, more than 5,000 prescribers have written ARCALYST prescriptions for recurrent pericarditis (search). The average total duration of ARCALYST therapy in recurrent pericarditis was approximately 3 years, consistent with the median duration of the disease.
ARCALYST is a weekly, subcutaneously injected recombinant dimeric fusion protein that blocks interleukin-1 alpha (IL-1α) and interleukin-1 beta (IL-1β (search)) signaling. The FDA granted Breakthrough Therapy designation to ARCALYST for recurrent pericarditis (search) in 2019 and Orphan Drug exclusivity in 2021.
KPL-387 (search) Phase 2 Data and Phase 3 Initiation
Kiniksa announced data from an interval analysis of the ongoing KPL-387 (search) Phase 2/3 trial in recurrent pericarditis (search). KPL-387 is an investigational, fully human immunoglobulin G2 (IgG2) monoclonal antibody that binds human interleukin-1 receptor 1 (IL-1R1 (search)), inhibiting signaling of both IL-1α and IL-1β (search).
Participants in the KPL-387 (search) 300 mg subcutaneous monthly dose group experienced rapid and sustained reductions in pain and inflammation. The median time to treatment response — defined as pain response (NRS score ≤2 on the 11-point daily pericarditis pain scale) and at least one CRP level ≤0.5 mg/dL within 7 days before or after pain response — was 4.0 days (95% CI: 3.0, 6.0). Median time to pain response was 4.0 days (95% CI: 3.0, 6.0), and median time to CRP normalization (CRP ≤0.5 mg/dL) was 8.0 days (95% CI: 7.0, 9.0).
Efficacy was durable throughout the monthly dosing interval, and KPL-387 (search) was generally well-tolerated, consistent with the known safety profile of IL-1 pathway inhibition.
Based on these results, Kiniksa is now enrolling and dosing patients in PASTORALE, the pivotal Phase 3 portion of the trial. PASTORALE is an event-driven, double-blind, placebo-controlled, randomized withdrawal study enrolling up to approximately 85 participants with recurrent pericarditis (search). The trial evaluates KPL-387 (search) 300 mg administered subcutaneously once-monthly in a liquid formulation, with the primary endpoint being time to first adjudicated pericarditis recurrence during the randomized withdrawal period.
"We are excited to advance KPL-387 (search) with its target product profile of once-monthly subcutaneous dosing in a liquid formulation. We expect to bring this potential additional treatment option to patients in the 2028/2029 timeframe," said Patel.
The FDA granted Orphan Drug Designation to KPL-387 (search) for the treatment of pericarditis in October 2025.
KPL-1161 (search): Targeting Quarterly Dosing
Kiniksa also provided an update on KPL-1161 (search), an independently developed, investigational, Fc-modified IgG2 monoclonal antibody that binds IL-1R1 (search). The company is targeting a profile of quarterly subcutaneous dosing and expects to initiate a Phase 1 first-in-human clinical trial by the end of 2026.
Financial Position
Total revenue for the second quarter of 2026 was $243.6 million, compared to $156.8 million for the second quarter of 2025. Net income was $25.4 million, or $0.30 per diluted share, compared to $17.8 million, or $0.23 per diluted share, in the prior-year period.
Research and development expenses increased to $40.9 million from $18.8 million in the second quarter of 2025, primarily driven by increased KPL-387 (search) clinical and manufacturing activity as well as preclinical development investment. Selling, general, and administrative expenses rose to $63.9 million from $46.9 million, reflecting investment in ARCALYST commercialization.
As of June 30, 2026, Kiniksa held $525.9 million in cash, cash equivalents, and short-term investments with no debt. The company expects its current operating plan to remain cash flow positive on an annual basis.