Last reviewed 2026-04-20 · How we verify

Arcalyst (RILONACEPT)

Arcalyst works by binding to Interleukin-1 beta, preventing its interaction with its receptor and reducing inflammation.

Arcalyst (Rilonacept) is a small molecule modality developed by Regeneron Pharmaceuticals, targeting Interleukin-1 beta. It was FDA approved in 2008 for the treatment of Cryopyrin-associated periodic syndrome. Arcalyst works by binding to Interleukin-1 beta, preventing its interaction with its receptor and subsequently reducing inflammation. The commercial status of Arcalyst is patented, and it is owned by Regeneron Pharmaceuticals. Key safety considerations include potential injection site reactions and increased risk of infections.

At a glance

Mechanism of action

Rilonacept is an interleukin-1 alpha (IL-1) and interleukin-1 beta (IL-1) cytokine trap. Rilonacept blocks IL-1 signaling by acting as soluble decoy receptor that binds both IL-1 and IL-1 and prevents its interaction with cell surface receptors. Rilonacept also binds interleukin-1 receptor antagonist (IL-1ra). The equilibrium dissociation constants for rilonacept binding to IL-1, IL-1, and IL-1ra were 1.4 pM, 0.5 pM, and 6.1 pM, respectively.CAPS refers to rare genetic syndromes generally caused by mutations in the NLRP-3 [nucleotide-binding domain, leucine rich family (NLR), pyrin domain containing 3] gene (also known as Cold-Induced Autoinflammatory Syndrome-1 [CIAS1]). CAPS disorders are inherited in an autosomal dominant pattern with male and female offspring equally affected. Features common to all disorders include fever, urticaria-like rash, arthralgia, myalgia, fatigue, and conjunctivitis.In most cases, inflammation in CAPS is associated with mutations

Approved indications

• Cryopyrin associated periodic syndrome

Common side effects

• Injection-site reactions
• Infections
• Nausea
• Diarrhea
• Sinusitis
• Abdominal pain upper
• Cough
• Hypoesthesia
• Stomach discomfort
• Urinary tract infection
• Rash
• Otitis media

Key clinical trials

• Rilonacept in Subjects With Cardiac Sarcoidosis (PHASE2)
• A Safety and Efficacy Study of Mycophenolate Mofetil and Rilonacept in Patients With Alcoholic Hepatitis (PHASE2)
• Study to Assess the Efficacy and Safety of Rilonacept Treatment in Participants With Recurrent Pericarditis (PHASE3)
• A Pilot Study of KPL-914 in Recurrent Pericarditis (PHASE2)
• Inflammation in Chronic Kidney Disease and Cardiovascular Disease - The Role of Genetics and Interleukin-1 Receptor Antagonist (IL-1ra) (PHASE2)
• Cold Contact Urticaria Treatment With Rilonacept (PHASE2)
• IL1-TRAP, Rilonacept, in Systemic Sclerosis (PHASE1,PHASE2)
• Rilonacept for Deficiency of the Interleukin-1 Receptor Antagonist (DIRA) (PHASE2)

Patents

Primary sources

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