Arcalyst (rilonacept) is a therapy that the U.S. Food and Drug Administration approved as a treatment for adults and children ages 12 and older with Cryopyrin-Associated Periodic Syndromes, or CAPS. Those syndromes include Familial Cold Autoinflammatory Syndrome (FCAS) and Muckle-Wells Syndrome (MWS).

Regeneron Pharmaceuticals distributes the injected anti-inflammatory drug.

A hallmark of CAPS disorders is inflammation in many parts of the body that causes fever, rash, joint pain, and fatigue.

About half of children with systemic juvenile arthritis share some of the symptoms of CAPS, so Regeneron is looking at whether Arcalyst can treat that disease as well. Systemic juvenile arthritis, or sJA, differs from juvenile arthritis, or JA, in that its inflammation affects the entire body rather than just the joints. Patients with sJA can experience constant joint pain, fever, tiredness, rashes, loss of appetite, and weight loss.

How Arcalyst works

The active substance in Arcalyst is rilonacept, an interleukin (IL) inhibitor. It works by attaching to interleukin-1beta (IL-1β), an immune system protein that causes inflammation.

IL-1β is produced at high levels in CAPS patients, causing excessive inflammation. By attaching to IL-1β, Arcalyst blocks its activity, helping to reduce inflammation and relieve the symptoms of the disease.

Arcalyst in clinical trials for sJA

Research indicating that interleukin (IL)-1 plays a key role in sJA has led to the development of biologic medications like Arcalyst that inhibit the protein.

A Phase 1 clinical trial (NCT01803321) evaluated the safety and effectiveness of two doses as a treatment for CAPS patients ages 4 to 20. The trial consisted of four weeks of either Arcalyst or a placebo, followed by 23 months of Arcalyst.

The conditions of more than half of the Arcalyst-treated patients improved over two years, results showed.

A larger 24-week randomized Phase 2 trial (NCT00534495) tested the safety and effectiveness of Arcayst in 71 children and young adults with sJA. The findings, published in 2014, showed that the drug was effective and that patients tolerated it well.

Other details

The most common side effects are reactions at the injection site, upper respiratory tract infections, sinusitis, and headache.

Arcalyst has yet to be approved for children with systemic juvenile arthritis.

Note: Juvenile Arthritis News is strictly a news and information website about the disease. It does not provide medical advice, diagnosis or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.

Ana holds a PhD in Immunology from the University of Lisbon and worked as a postdoctoral researcher at Instituto de Medicina Molecular (iMM) in Lisbon, Portugal. She graduated with a BSc in Genetics from the University of Newcastle and received a Masters in Biomolecular Archaeology from the University of Manchester, England. After leaving the lab to pursue a career in Science Communication, she served as the Director of Science Communication at iMM.
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Ana holds a PhD in Immunology from the University of Lisbon and worked as a postdoctoral researcher at Instituto de Medicina Molecular (iMM) in Lisbon, Portugal. She graduated with a BSc in Genetics from the University of Newcastle and received a Masters in Biomolecular Archaeology from the University of Manchester, England. After leaving the lab to pursue a career in Science Communication, she served as the Director of Science Communication at iMM.
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