interleukin 23 is thought to be critical to the pathogenesis of psoriasis we compared risankizumab bi 655066 a humanized igg1 monoclonal antibody that inhibits interleukin 23 by specifically targeting the p19 subunit and thus prevents interleukin 23 signaling and ustekinumab an interleukin 12 and interleukin 23 inhibitor in patients with moderate to severe plaque psoriasis we randomly assigned a total of 166 patients to receive subcutaneous injections of risankizumab a single 18 mg dose at week 0 or 90 mg or 180 mg doses at weeks 0 4 and 16 or ustekinumab 45 or 90 mg according to body weight at weeks 0 4 and 16 the primary end point was a 90 or greater reduction from baseline in the psoriasis area and severity index pasi score at week 12 at week 12 the percentage of patients with a 90 or greater reduction in the pasi score was 77 64 of 83 patients for risankizumab 90 mg and 180 mg groups pooled as compared with 40 16 of 40 patients for ustekinumab p 0 001 the percentage of patients with a 100 reduction in the pasi score was 45 in the pooled 90 mg and 180 mg risankizumab groups as compared with 18 in the ustekinumab group efficacy was generally maintained up to 20 weeks after the final dose of 90 or 180 mg of risankizumab in the 18 mg and 90 mg risankizumab groups and the ustekinumab group 5 patients 12 6 patients 15 and 3 patients 8 respectively had serious adverse events including two basal cell carcinomas and one major cardiovascular adverse event there were no serious adverse events in the 180 mg risankizumab group in this phase 2 trial selective blockade of interleukin 23 with risankizumab was associated with clinical responses superior to those associated with ustekinumab this trial was not large enough or of long enough duration to draw conclusions about safety funded by boehringer ingelheim clinicaltrials gov number nct02054481.