1 for adults with plaque psoriasis after failure of topical symptomatic treatments and puva therapy several systemic immunosuppressive agents are acceptable for severe disease methotrexate then ciclosporin and possible a tnf alpha antagonist etanercept etc 2 ustekinumab is an inhibitor of interleukins 12 and 23 which are believed to be implicated in the onset of psoriasis it is authorized in the european union for patients who fail to respond to conventional systemic treatments 3 in one trial with a low level of evidence single blind 2 subcutaneous injections of ustekinumab at an interval of 4 weeks appeared to be statistically more effective than twice weekly subcutaneous injections of etanercept for 12 weeks more patients achieved a 75 reduction in the score most widely used to evaluate the extent and intensity of plaque psoriasis lesions pasi score about 71 versus 57 the results beyond this period have not been reported 4 two randomised double blind placebo controlled trials in a total of 1996 patients showed that at least two thirds of patients treated with ustekinumab achieved at least a 75 reduction in their pasi score versus fewer than 4 with placebo 5 in animal studies interleukin 12 and 23 inhibitors cause cancer there is therefore a high risk of cancer developing during prolonged treatment with ustekinumab 6 the main adverse effects identified in clinical trials include infections injection site reactions psychological disorders and development of anti ustekinumab antibodies 7 there is insufficient follow up to evaluate the cardiac risks associated with ustekinumab 8 as maintenance therapy ustekinumab is administered as one subcutaneous injection every 12 weeks this practical advantage compared to tnf alpha antagonists must be weighed against the risks inherent in prolonged immunosuppression 9 in summary for symptomatic relief of patients whose psoriasis poses major problems despite treatment with methotrexate or ciclosporin in the absence of a better alternative it is better to use a tnf alpha antagonist and to avoid exposing patients to the risks associated with ustekinumab particularly its carcinogenic risk.