 Interleukin antagonists, the most recent class of biologics available for use in IBD, inhibit the action of IL-12 and IL-23 by binding to the p40 protein subunit that is found on both of these cytokines.Ustekinumab was approved by the FDA in 2009 for the treatment of plaque psoriasis, making it the first and so far the only approved interleukin antagonist.It is also used for the treatment of Crohn's disease and psoriatic arthritis.