RILONACEPT IS A DIMERIC FUSION PROTEIN CONSISTING OF THE LIGAND-BINDING DOMAINS OF THE EXTRACELLULAR PORTIONS OF THE HUMAN INTERLEUKIN-1 RECEPTOR COMPONENT (IL-1RI) AND IL-1 RECEPTOR ACCESSORY PROTEIN (IL-1RACP) LINKED IN-LINE TO THE FC PORTION OF HUMAN IGG1.
CAPS REFER 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 AUTO-INFLAMMATORY 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 IN THE NLRP-3 GENE WHICH ENCODES THE PROTEIN CRYOPYRIN, AN IMPORTANT COMPONENT OF THE INFLAMMASOME. CRYOPYRIN REGULATES THE PROTEASE CASPASE-1 AND CONTROLS THE ACTIVATION OF INTERLEUKIN-1 BETA (IL-1B). MUTATIONS IN NLRP-3 RESULT IN AN OVERACTIVE INFLAMMASOME RESULTING IN EXCESSIVE RELEASE OF ACTIVATED IL-1B THAT DRIVES INFLAMMATION.
RILONACEPT BLOCKS IL-1B SIGNALING BY ACTING AS A SOLUBLE DECOY RECEPTOR THAT BINDS IL-1B AND PREVENTS ITS INTERACTION WITH CELL SURFACE RECEPTORS. RILONACEPT ALSO BINDS IL-1A AND IL-1 RECEPTOR ANTAGONIST (IL-1RA) WITH REDUCED AFFINITY.