Potent and selective human P2X7 antagonist (KB values are 5 - 7 and > 10,000 nM at hP2X7 and rP2X7 respectively) that is completely without effect at all other P2X subtypes. Inhibits BzATP-mediated calcium influx and inhibits ATP-mediated IL-1β release in vitro (KB values are 15 and 92 nM respectively).