IL-23 skin and joint profiling in psoriatic arthritis: novel perspectives in understanding clinical responses to IL-23 inhibitors.

OBJECTIVES: To determine the relationship between synovial versus skin transcriptional/histological profiles in patients with active psoriatic arthritis (PsA) and explore mechanistic links between diseased tissue pathology and clinical outcomes. METHODS: Twenty-seven active PsA patients were enrolled in an observational/open-label study and underwent biopsies of synovium and paired lesional/non-lesional skin before starting anti-tumour necrosis factor (TNF) (if biologic-naïve) or ustekinumab (if anti-TNF inadequate responders). Molecular analysis of 80-inflammation-related genes and protein levels for interleukin (IL)-23p40/IL-23p19/IL-23R were assessed by real-time-PCR and immunohistochemistry, respectively. RESULTS: At baseline, all patients had persistent active disease as per inclusion criteria. At primary end-point (16-weeks post-treatment), skin responses favoured ustekinumab, while joint responses favoured anti-TNF therapies. Principal component analysis revealed distinct clustering of synovial tissue gene expression away from the matched skin. While IL12B, IL23A and IL23R were homogeneously expressed in lesional skin, their expression was extremely heterogeneous in paired synovial tissues. Here, IL-23 transcriptomic/protein expression was strongly linked to patients with high-grade synovitis who, however, were not distinguishable by conventional clinimetric measures. CONCLUSIONS: PsA synovial tissue shows a heterogeneous IL-23 axis profile when compared with matched skin. Synovial molecular pathology may help to identify among clinically indistinguishable patients those with a greater probability of responding to IL-23 inhibitors.

Targeted therapies: what they teach us about the pathogenesis of psoriasis and psoriatic arthritis.

INTRODUCTION: Biologic therapy has revolutionized treatment pathways in psoriatic joint and skin disease. It has also provided a useful tool with which pathological pathways of this condition may be explored. Areas covered: This review presents data on the clinical and biological effects of targeted therapy in psoriatic arthritis and psoriasis. Therapeutic agents covered include inhibitors of TNFα, inhibitors of the IL-23/IL-17 axis and inhibitors of intracellular small molecules involved in the transduction of the inflammatory signal. Trial data on clinical and imaging efficacy is reviewed in parallel with studies on biological effects at tissue level. Pathological insights gained from the use of these treatments are explored. Expert commentary: A close relationship exists between specific pathological types and clinical manifestations of psoriatic disease, including responses to treatment. Studying these relationships is likely to improve understanding of disease and enable rational selection of specific treatments for patients with specific pathotypes.