|Other names||IL-1 Trap|
|Drug class||Interleukin 1 receptor inhibitor|
|Main uses||Cryopyrin-associated periodic syndromes; deficiency of interleukin-1 receptor antagonist; recurrent pericarditis|
|Side effects||Pain at the site of injection, respiratory tract infection|
|Chemical and physical data|
|Molar mass||201209.36 g·mol−1|
Rilonacept, sold under the brand name Arcalyst, is a medication used to treat cryopyrin-associated periodic syndromes, including familial cold autoinflammatory syndrome, and Muckle–Wells syndrome; deficiency of interleukin-1 receptor antagonist; and recurrent pericarditis. It is given by injection under the skin.
Common side effects pain at the site of injection and respiratory tract infection. Other side effects may include infections, cancer, and allergic reactions. There are concerns that use in pregnancy could harm the baby. It is an interleukin 1 receptor inhibitor.
Rilonacept was approved for medical use in the United States in 2008. While it was approved in Europe in 2009, this approval was withdrawn in 2012. In the United States, four vials of 220 mg cost about 21,000 USD as of 2021.
Rilonacept is a dimeric fusion protein consisting of the ligand-binding domains of the extracellular portions of the human interleukin-1 receptor component (IL-1R1) and IL-1 receptor accessory protein (IL-1RAcP) linked in-line to the fragment-crystallizable portion (Fc region) of human IgG1 that binds and neutralizes IL-1.
Rilonacept was given an orphan drug designation by the U.S. Food and Drug Administration (FDA).  Rilonacept is the first drug approved by the FDA to treat recurrent pericarditis. On May 8, 2012 an FDA Advisory Panel voted 11–0 against the approval of rilonacept for the treatment of gout, stating that the benefits did not outweigh the risks associated with the drug.
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