How does ustekinumab inhibit the activity of interleukins IL-12 and IL-23?

Ustekinumab binds specifically to the shared p40 protein subunit of IL-12 and IL-23, preventing p40 from binding to the IL-12Rβ1 receptor protein on immune cells and thereby inhibiting both cytokines’ bioactivity; it cannot bind IL-12 or IL-23 already bound to these receptors.