Psoriasis is a chronic immune mediated disease in which the interplay of T cells and keratinocytes seems to play a key role. In this context, the interleukin (IL)-23/IL-17 axis is currently considered to be crucial in the pathogenesis of psoriasis and the selective inhibition of IL-23 may be viewed as an improvement of treatments blocking both IL-23 and IL-12, since its upstream actions. Areas covered: The authors performed a thorough and updated review on guselkumab, a fully human IgG1λ monoclonal antibody that blocks the p19 subunit of IL-23, analyzing efficacy and safety data from phase I, II and III trials. Expert opinion: Guselkumab represents a very promising therapy, providing an alternative mechanism of action with high efficacy and...