IL9 and psoriasis: Ustekinumab (a monoclonal antibody directed against the common p40 subunit of IL-12 and IL-23), guselkumab (the first human antibody against the p40 subunit of the IL-23 receptor), risankizumab (a humanized IgG monoclonal antibody that binds to the p19 subunit of IL-23 and inhibits its interaction with the IL-23 receptor), and tildrakizumab (a humanized IgG1 monoclonal antibody targeting IL-23 p19) are effective IL-23 inhibitors indicated for psoriasis [8,173].