Psoriasis is an immune-mediated inflammatory skin disease that affects millions worldwide. Studying immune cells involved in psoriasis pathogenesis is essential to identify effective and safe therapeutics for the disease. Using human psoriasis skin, activated macrophages were observed in both lesional and non-lesional skin, but were elevated in lesional skin. Activation of the IL-23/IL-17 pathway is integral to the development of psoriasis. To further characterize the monocyte/macrophage (Mon/Mac) population when the IL-23 pathway is activated, a murine model of intradermal injection of IL-23 was used. Flow cytometry revealed that Mon/Mac cells were the dominant immune population, particularly late in the model, highlighted by strong presence of Ly6C hi MHC II hi cells. The Mon/Mac cells were also shown to have high expression for TNFα but not IL-17A. Prophylactic dosing of a CSF-1R inhibitor to deplete Mon/Mac cells significantly reduced several inflammatory mediators from the skin tissue suggesting a pathogenic role for Mon/Mac. Treatment dosing of the inhibitor produced a less robust effect. Mon/Mac cells were also differentiated by levels of Ki67 and TNFα expression. These data point to an important contribution of Mon/Mac cells in IL-23 related skin inflammation and suggest that these cells are a significant player in the underlying pathophysiology of psoriasis.

Collectively, our studies indicate that a 5 day model of IL-23 psoriasiform dermatitis can be used to assess the pharmacology of novel small molecules/biologics in the treatment of PsO.

Psoriasis vulgaris (PV) results from activation of IL‐23/Th17 immune pathway and is further amplified by cytokines/chemokines from skin cells. Among skin‐derived pro‐inflammatory cytokines, IL‐36 family members are highly upregulated in PV patients and play a critical role in general pustular psoriasis. However, there is limited data showing crosstalk between the IL‐23 and IL‐36 pathways in PV. Herein, potential attenuation of skin inflammation in the IL‐23‐induced mouse model of psoriasiform dermatitis by functional inhibition of IL‐36 receptor (IL‐36R) was interrogated. Anti‐mouse IL‐36R monoclonal antibodies (mAbs) were generated and validated in vitro by inhibiting IL‐36α‐induced secretion of CXCL1 from NIH 3T3 cells. Antibody target engagement was demonstrated by inhibition of CXCL1 production in a novel acute model of IL‐36α systemic injection in mice. In addition, anti‐IL‐36R mAbs inhibited tissue inflammation and inflammatory gene expression in an IL‐36α ear injection model of psoriasiform dermatitis demonstrating engagement of the target in the ear skin. To elucidate the possible role of IL‐36 signalling in IL‐23/Th17 pathway, the ability of anti‐IL‐36R mAbs to inhibit skin inflammation in an IL‐23 ear injection model was assessed. Inhibiting the IL‐36 pathway resulted in significant attenuation of skin thickening and psoriasis‐relevant gene expression. Taken together, these data suggest a role for IL‐36 signalling in the IL‐23/Th17 signalling axis in PV.

Foxp3+ regulatory T cells (Tregs) represent a major fraction of skin resident T cells. Although normally protective, Tregs have been shown to produce pro-inflammatory cytokines in human diseases, including psoriasis. A significant hurdle in the Treg field has been the identification, or development, of model systems to study this Treg plasticity. To overcome this gap, we analyzed skin resident Tregs in a mouse model of IL-23 mediated psoriasiform dermatitis. Our results demonstrate that IL-23 drove the accumulation of Tregs; including a subpopulation that co-expressed RORγt and produced IL-17A. Genesis of this population was attenuated by a RORγt inverse agonist compound and clinically relevant therapeutics. In vitro, IL-23 drove the generation of CD4+Foxp3+RORγt+IL-17A+ cells from Treg cells. Collectively, our data shows that IL-23 drives Treg plasticity by inducing a population of CD4+Foxp3+RORγt+IL-17A+ cells that could play a role in the disease pathogenesis. Through this work, we define an in vitro system and a pre-clinical in vivo mouse model that can be used to further study Treg homeostasis and plasticity in the context of psoriasis.

IL-36 cytokines are pro-inflammatory members of the IL-1 family that are upregulated in inflammatory disorders. Specifically, IL-36γ is highly expressed in active psoriatic lesions and can drive pro-inflammatory processes in 3D human skin equivalents supporting a role for this target in skin inflammation. Small molecule antagonists of interleukins have been historically challenging to generate. Nevertheless, we performed a small molecule high-throughput screen to identify IL-36 antagonists using a novel TR-FRET binding assay. Several compounds, including 2-oxypyrimidine containing structural analogs of the marketed endothelin receptor A antagonist Ambrisentan, were identified as hits from the screen. A-552 was identified as a the most potent antagonist of human IL-36γ, but not the closely related family member IL-36α, was capable of attenuating IL-36γ induced responses in mouse and human disease models. Additionally, x-ray crystallography studies identified key amino acid residues in the binding pocket present in human IL-36γ that are absent in human IL-36α. A-552 represents a first-in-class small molecule antagonist of IL-36 signaling that could be used as a chemical tool to further investigate the role of this pathway in inflammatory skin diseases such as psoriasis.

The interleukin (IL)‐23/IL‐17 axis plays a central role in the pathogenesis of psoriasis and is elevated in lesional psoriatic skin. Different murine models have been developed to mimic this pathophysiology each carrying specific merits and limitations. In an attempt to address some of these limitations, B10.RIII mice received a single hydrodynamic injection of IL‐23 minicircles (MC) to induce hepatic transcription and the endogenous production of IL‐23. Plasma and ear IL‐23 levels were dose‐dependently (0.3–3 μg) increased in MC injected mice and were sustained over the 14‐day study duration. Beginning on day 7 post‐injection, mice developed dose‐related ear inflammation, histologically confirmed increases in epidermal and dermal area, as well as enhanced neutrophil and macrophage content. Flow cytometry demonstrated increased levels of granulocytes, T cells and monocytes/macrophages in the ear skin, with T cells identified as the main cellular source of IL‐17A. Evaluation of mRNA and protein showed time‐dependent, increased levels of the IL‐23/IL‐17 pathway and inflammatory/microbial cytokines/chemokines in the ear which differed kinetically from circulating levels. An anti‐IL‐23p40 antibody was assessed following both prophylactic administration and administration once the disease was established. Prophylactic dosing completely prevented the development of the ear phenotype across endpoints. Treatment administration showed a dose‐related response, with a maximum inhibition of 64–94%, depending on endpoint. These data demonstrate that the IL‐23 MC model is a useful approach to study IL‐23/IL‐17‐driven skin inflammation and may facilitate preclinical assessment of novel therapies.

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The objective of this study was to describe adults initiating dupilumab for AD, in terms of sociodemographics, comorbidity burden, AD treatment patterns, and persistence on dupilumab. From Truven US MarketScan data, we identified adults with AD with 1 dupilumab dispensation (Rx) between 28 March 2017 (US market launch) and 31 January 2018 with continuous enrolment during the baseline period (12 months prior to index Rx). Patients were followed from first dupilumab Rx until 31 July 2018 or disenrollment. Kaplan-Meier curves were used to estimate persistence at 6 and 12 months, using a 30-day grace period and assuming 14-day injection frequency. 1,637 adults initiated dupilumab (mean[SD] age 42.2[15.8]; 49.9% women, 94.7% commercially insured) and 53.2% had 1 atopic comorbidity (allergic rhinitis [33.7%] and asthma [26.8%] were most prevalent). AD treatments during baseline included: systemic corticosteroids (71.9%), PDE-4 inhibitors (15.8%), phototherapy (10.1%), immunosuppressants (24.7%; 10.8% cyclosporine), topical corticosteroids (81.1%). Over a mean (SD) follow-up of 287.5 (106.2) days, dupilumab persistence (95% CI) at 6 and 12 months was 92.2% (90.9-93.6%) and 78.5% (75.9-81.1%), respectively. Among patients discontinuing dupilumab, 66.9% reinitiated treatment within a mean of 111.5 (65.5) days. Most dupilumab initiators were persistent at 12 months; among those discontinuing, a majority reinitiated treatment. We conclude that 12month persistence on dupilumab in AD is higher than reported persistence for the most commonly used first-line biologic treatment for psoriasis, adalimumab (53.4% 1). These findings suggest patient satisfaction with dupilumab effectiveness and tolerability. 1