Psoriatic arthritis (PsA) is a chronic inflammatory seronegative 
spondyloarthritis associated with psoriasis. While TNF-α inhibitors have 
revolutionized the treatment of rheumatic diseases, including PsA, not all 
patients respond to these agents while others are unsuitable or intolerant to 
them. Thus, there is a need for additional treatment modalities with a novel 
mechanism of action. In the past years, the IL-23/Th17 axis has emerged as an 
important mechanism in the pathogenesis of PsA. Ustekinumab, a fully human IgG1κ 
monoclonal antibody that targets the common subunit p40 of IL-12 and IL-23, has 
been shown in clinical trials, to be well-tolerated and effective in patients 
with active PsA. It improved signs and symptoms of PsA, inhibited radiographic 
progression and was effective in dactylitis, enthesitis, and skin disease, with 
a safety profile consistent with the one observed in patients with psoriasis. 
Moreover, it was to be effective in anti-TNF-α experienced patients, definitely 
fulfilling an unmet need in the management of PsA.