Pharmacologyustekinumab is a human monoclonal antibody that binds to and interferes with the proinflammatory cytokines, interleukin (il)-12 and il-23. biological effects of il-12 and il-23 include natural killer (nk) cell activation, cd4+ t-cell differentiation and activation. ustekinumab also interferes with the expression of monocyte chemotactic protein-1 (mcp-1), tumor necrosis factor-alpha (tnf-a), interferon-inducible protein-10 (ip-10), and interleukin-8 (il-8). significant clinical improvement in psoriasis and psoriatic arthritis patients is seen in association with reduction of these proinflammatory signalers.indications-crohn disease: treatment of moderately to severely active crohn disease in adults who have failed or were intolerant to immunomodulatory or corticosteroid therapy, but never failed tumor necrosis factor (tnf) blocker therapy or who have failed or were intolerant to treatment with one or more tnf blockers.-plaque psoriasis.-psoriatic arthritis.