Increased expression of IL‐17A and limited involvement of IL‐23 in patients with palmo‐plantar (PP) pustular psoriasis or PP pustulosis; results from a randomised controlled trial

BACKGROUND: Palmo-plantar pustular psoriasis (PPPP) and palmo-plantar pustulosis (PPP) are chronic skin diseases with significant impact on quality of life. OBJECTIVES: The purpose of this study was to study the efficacy of ustekinumab in PPPP and PPP and gain more knowledge on the pathophysiology and the role of the interleukin-23 (IL-23) signalling pathway in these diseases. METHODS: Thirty-three patients with either PPPP (20) or PPP (13) and seven volunteers with normal palmo-plantar skin were recruited. Patients with PPP or PPPP were randomised (1 : 1) to receive either an anti IL-12/IL-23 antibody (ustekinumab 45 mg) or placebo at day 0 and week 4 with subsequent placebo cross-over to ustekinumab at week 16. The primary endpoint was the proportion of patients randomized to ustekinumab achieving a 50% improvement in the Palmo-Plantar Pustular Area and Severity Index (PPPASI-50) as compared to placebo. Skin biopsies of the palms and soles of normal subjects and patients with PPP or PPPP were performed and analysed by RT-PCR and immunohistochemistry. RESULTS: There was no statistically significant difference in the proportion of patients randomised to ustekinumab as compared to those randomised to placebo achieving PPPASI-50 at week 16 for patients with PPPP (10%, 20%; P = 1.000) or PPP (20%, 37.5%; P = 1.000) respectively. Compared to normal subjects an 89-fold increase in IL-17A expression was found in palms/soles of patients with PPPP (P = 0.006) and a 190-fold increase for patients with PPP (P = 0.051). There were no statistically significant changes in cytokine expression at week 16 in the palms and soles of patients with PPP or PPPP. CONCLUSION: Taken together these results suggest that ustekinumab at a dose of 45 mg has limited efficacy in PPPP and PPP. IL-17A may have a more important role than IL-23 in patients with PPPP and PPP. Conclusions are limited by the small sample size of this study.