List of products in the National Drug Code with proprietary name . This medication is used to treat a certain group of inherited disorders called cryopyrin-associated periodic syndromes (CAPS), including familial cold autoinflammatory syndrome and Muckle-Wells syndrome. Rilonacept works by blocking a certain natural protein in your body (interleukin-1) that may worsen the symptoms of CAPS. Rilonacept does not cure CAPS, but it can help lessen the symptoms, including rash, joint pain, fever, and tiredness.