Potent and selective antagonist for the human type I interleukin-1 (IL-1) receptor (IC50 values are 8 nM, > 6.7 mM and > 200 mM for human type I, human type II and murine type I IL-1 receptors respectively). Blocks IL-1-induced expression of ICAM-1 and E-selectin in HUVECs and IL-1β induction of IL-8 in human dermal fibroblasts. Reduces IL-1β-induced IL-6 production and exhibits anti-inflammatory activity in vivo. MW (observed): 1895.14.