Role of IL-23 in the pathogenesis of psoriasis: a novel potential therapeutic target?

The Role of Interleukin 23/17 Axis in Psoriasis Management: A Comprehensive Review of Clinical Trials

Psoriasis pathogenesis is influenced by genetic factors and characterized by a complex interplay between genetic predisposition and various environmental triggers. These triggers set off metabolic processes involving inflammation, cell signaling, immune response dysregulation, and antigen presentation. Several types of innate and adaptive immune cells are involved in psoriasis. Among the cytokine cascade which leads to psoriasis development, the interleukin (IL)-23/Th17 axis, especially IL-17 production, emerges as crucial. Recognizing the pivotal role of this axis has facilitated the development of selective and effective biological drugs, such as anti-IL17 and anti-IL23 monoclonal antibodies. These drugs aim to achieve the complete or near-complete disappearance of psoriatic lesions, as indicated by PASI100 and PASI90 responses, respectively. In this context, the aim of our review was to delve into the functioning of the IL-23/Th17 axis, its dysregulation in psoriasis pathogenesis, and the therapeutic potential of its inhibition. Currently, 4 anti-IL17 (secukinumab, ixekizumab, bimekizumab and brodalumab) and 3 anti-IL23 (guselkumab, risankizumab and tildrakizumab) have been approved. All these drugs showed high levels of effectiveness in both clinical trials and real-life experiences, with an excellent profile in terms of safety. Certainly, furthers studies will allow for better characterization of biologics' profile, in order to administer the right drug for the right patients at the right moment.

Risankizumab: Mechanism of action, clinical and translational science

Risankizumab is a high-affinity neutralizing anti-interleukin (IL)-23 monoclonal antibody marketed in over 40 countries across the globe to treat several inflammatory diseases, such as plaque psoriasis (PsO), psoriatic arthritis (PsA), and Crohn's disease (CD). This paper reviews the regulatory approval, mechanism of action, pharmacokinetics (PKs)/pharmacodynamics, immunogenicity, and clinical efficacy and safety data for risankizumab, focusing on the three main approved indications. Risankizumab binds to the p19 subunit of IL-23 and inhibits IL-23 from interacting with the IL-23 receptor and subsequent signaling. Biomarker data obtained following treatment with risankizumab in multiple indications provided supportive evidence for downstream blockade of IL-23 signaling associated with disease pathology. The PKs of risankizumab is linear and time-independent, consistent with typical IgG1 monoclonal antibodies, across all evaluated indications. Risankizumab exhibited positive exposure-response relationships for efficacy with no apparent exposure-dependent worsening in safety. Immunogenicity to risankizumab had no major clinical consequences for either efficacy or safety. Efficacy and safety of risankizumab have been established in PsO, PsA, and CD in the pivotal clinical trials where superior benefit/risk profiles were demonstrated compared to placebo and/or active comparators. Moreover, safety evaluations in open-label extension studies following long-term treatment with risankizumab showed stable and favorable safety profiles consistent with shorter-term studies. These data formed the foundation for risankizumab's marketing approvals to treat multiple inflammatory diseases across the globe.

Interclass Switch between IL17 and IL23 Inhibitors in Psoriasis: A Real-Life, Long-Term, Single-Center Experience

BACKGROUND

Interleukin 23 (IL-23) inhibitors, such as guselkumab, risankziumab, and tildrakizumab, have proved to be highly effective and safe for psoriasis treatment either in bio-naïve or bio-experienced patients. A substantial proportion of patients show a primary or secondary inefficacy to IL-17 inhibitors and can benefit from an alternative line of treatment, like IL-23 inhibitors. To date, no sufficient data are available on the effectiveness of IL-23 inhibitors after an anti-IL-17 agent.

METHODS

Our study includes 48 patients with moderate to severe psoriasis undergoing a switch from IL-17 to IL-23 inhibitors. This trial is registered with SS_DERMO_20.

RESULTS

The mean PASI (Psoriasis Area Severity Index) decreases from 11.6 to 3.3 at week 16, with responses maintained at weeks 28 and 52 (2 and 1.4, respectively), and a PASI100 achievement in more than 24% of patients at 16 weeks and 61.9 at 48 weeks, with no occurrence of serious adverse events. However, almost one in six patients interrupted the IL-23 inhibitors mainly due to primary ineffectivenss.

CONCLUSIONS

Our data support the evidence that an interclass switch among IL-17 inhibitors is a safe and effective therapeutic option for these patients.

The preclinical discovery and development of deucravacitinib for the treatment of psoriasis

INTRODUCTION

Psoriasis is a chronic inflammatory skin disease that most commonly presents as plaque psoriasis. The understanding of the pivotal pathogenetic role of the IL-23/IL-17 axis has dramatically changed the therapeutic approach to the disease. The identification of intracellular signaling pathways mediating IL-23 activity provided the rationale for targeting TYK2.

AREAS COVERED

This review assesses the underlying rationale that led to development of deucravacitinib, a novel oral TYK2 inhibitor, as a therapeutic option for the treatment of moderate-to-severe psoriasis, primarily focusing on pre-clinical and early phase clinical studies.

EXPERT OPINION

Innovative therapies used in patients with moderate-to-severe psoriasis include biologic agents and small molecules, which are associated with less adverse events than traditional systemic agents. Deucravacitinib, which selectively targets TYK2, has demonstrated to be effective in treating psoriasis, preserving a more favorable safety profile compared to other JAK inhibitors approved for the treatment of other immune diseases that block the ATP-binding site. Because of its oral administration, deucravacitinib represents an intriguing option in the therapeutic armamentarium of psoriasis, though the evaluation of long-term efficacy and safety is necessary to establish its place-in-therapy.

The circadian immune system

The immune system is highly time-of-day dependent. Pioneering studies in the 1960s were the first to identify immune responses to be under a circadian control. Only in the last decade, however, have the molecular factors governing circadian immune rhythms been identified. These studies have revealed a highly complex picture of the interconnectivity of rhythmicity within immune cells with that of their environment. Here, we provide a global overview of the circadian immune system, focusing on recent advances in the rapidly expanding field of circadian immunology.

Orchestrated Cytokines Mediated by Biologics in Psoriasis and Its Mechanisms of Action

Psoriasis is an autoimmune disease mediated by disturbed T cells and other immune cells, and is defined by deep-red, well-demarcated skin lesions. Due to its varied etiologies and indefinite standard pathogenesis, it is challenging to consider the right treatment exclusively for each psoriasis patient; thus, researchers yearn to seek even more precise treatments other than topical treatment and systemic therapy. Using biologics to target specific immune components, such as upregulated cytokines secreted by activated immune cells, is the most advanced therapy for psoriasis to date. By inhibiting the appropriate pro-inflammatory cytokines, cellular signaling can be altered and, thus, can inhibit further downstream inflammatory pathways. Herein, the roles of cytokines with their mechanisms of action in progressing psoriasis and how the usage of biologics alleviates cellular inflammation are discussed. In addition, other potential pro-inflammatory cytokines, with their mechanism of action, are presented herein. The authors hope that this gathered information may benefit future research in expanding the discovery of targeted psoriasis therapy.

Curcumin and ustekinumab cotherapy alleviates induced psoriasis in rats through their antioxidant, anti-inflammatory, and antiproliferative effects

INTRODUCTION

Psoriasis is a chronic multifactorial inflammatory disease that affects 3% of people worldwide. Ustekinumab is a selective anti-IL-12/23 biologic that alleviates psoriasis, and curcumin is a natural, effective dietary turmeric extract applied to treat numerous diseases through its antioxidant and anti-inflammatory effects.

OBJECTIVE

The current study evaluated the therapeutic effects of curcumin and ustekinumab cotherapy (CUC) on imiquimod (IQ)-induced psoriasis in a rat model.

MATERIALS AND METHODS

Twenty rats were divided into four groups, G1 (control group), G2 (IQ-treated group), G3 (IQ + ustekinumab), and G4 (IQ + CUC). Clinical, histopathological (HP), immunohistochemical (IHC), antioxidant, and biochemical investigations evaluated the efficacy of these drugs for treating IQ induced-psoriasis.

RESULTS

Rats of G2 exhibited clinical signs of psoriatic skin lesions (erythema, scaling, and skin thickening) with epidermal changes (acanthosis and parakeratosis). Additionally, the biochemical analysis revealed significant (p < 0.05) reductions in the levels of antioxidant biomarkers (SOD, GPx, and CAT) with significant (p < 0.05) elevations in psoriasis-related cytokines (TNF-α, IL-17A, IL-12P40, and IL-23). In contrast, CUC alleviated the psoriatic changes in G4 better than ustekinumab monotherapy in G3.

CONCLUSIONS

Ustekinumab inhibits the inflammatory cytokines IL-12P40 and IL-23, while curcumin has antioxidant effects (increasing SOD, GPx, and CAT levels) with anti-inflammatory effects (decreasing the proinflammatory cytokine TNF-α and IL-17). Therefore, CUC could be an excellent cost-effective regimen that can improve the treatment of psoriasis by the synergistic effects of CUC.HighlightsIQ-induces psoriasis by elevating TNF-α, IL-17A, IL-12, and IL-23 and decreasing GPx, SOD, and CATUstekinumab exhibits anti-inflammatory effects by inhibiting IL-12 and IL-23Curcumin inhibits TNF-α and IL-17A, and increases GPx, SOD, and CAT levelsCUC mitigates psoriasis by synergistic antioxidant and anti-inflammatory effectsCUC inhibits TNF-α, IL-17A, IL-12, and IL-23 and increases GPx, SOD, and CAT levels.

A Review of the Efficacy and Safety for Biologic Agents Targeting IL-23 in Treating Psoriasis With the Focus on Tildrakizumab

Psoriasis is a chronic and debilitating inflammatory immune-mediated skin disorder. Several cytokines including interleukin (IL)-23 were demonstrated to play a central role in the pathogenesis of this disease. Treatment options for psoriasis range from topical to systemic modalities, depending on the extent, anatomical locations involved and functional impairment level. Targeting cytokines or their cognate receptors that are involved in disease pathogenesis such as IL-12/23 (i.e., targeting the IL-12p40 subunit shared by these cytokines), IL-17A, IL-17F, IL-17RA, and TNF-α using biologic agents emerged in recent years as a highly effective therapeutic option for patients with moderate-to-severe disease. This review provides an overview of the important role of IL-23 signaling in the pathogenesis of psoriasis. We describe in detail the available IL-23 inhibitors for chronic plaque psoriasis. The efficacy, pharmacokinetic properties, and the safety profile of one of the most recent IL-23 biologic agents (tildrakizumab) are evaluated and reviewed in depth.

Rosmarinic acid protects mice from imiquimod induced psoriasis-like skin lesions by inhibiting the IL-23/Th17 axis via regulating Jak2/Stat3 signaling pathway

IL-23/Th17 (IL-17) axis plays a critical role in psoriasis. Rosmarinic acid (RA) was proved the inhibitory effect of T cell infiltration in the skin. However, whether and how RA has beneficial effects on psoriasis did not really know yet. So lipopolysaccharide (LPS)-induced abnormal proliferation Hacat cell line and Imiquimod (IMQ)-induced psoriasis-like mouse dermatitis were used to assess the pharmacological effects and mechanisms of RA by Psoriasis Area Severity Index (PASI) score, histopathology, flow cytometry, reverse transcription-polymerase chain reaction (RT-PCR) and western blotting. The results showed that RA inhibited LPS-induced aberrant expression of Hacat cell line, and significantly alleviated IMQ-induced skin inflammation. Although RA had no obviously effect on the ratio of epidermal Langerhans cell (LC) and LC migration from the skin to the skin draining lymph nodes, RA inhibited the expression of IL-23 in skin lesions, as well as reduced the differentiation of Th17 cells and producing of IL-17A by down regulating the transcriptor factor RORγt and JAK2/Stat3 signal pathway, comparing to IMQ treated group. The findings suggest that RA inhibits psoriasis-like skin inflammation in vivo and in vitro by reducing the expression of IL-23, inhibiting Th17 dominated inflammation and down regulating the Jak2/Stat3 signal pathway.

IL-23/Th17 Axis: A Potential Therapeutic Target of Psoriasis

Psoriasis is an immune-mediated skin disease that leads to the initiation of abnormal production of inflammatory mediators and keratinocytes hyper-proliferation. Th-1 cell expressing cytokines such as IL-1β and TNF-α have been the important hallmarks in the management of psoriasis. However, investigations carried out in the previous few years underline the involvement of another subset of T helper cells, i.e. Th-17 in psoriasis exacerbation, and hence become the point of focus now. The immunopathogenesis of Th-17 is the result of the IL-23/Th-17 axis. It involves the release of IL-17 and IL-22 in response to the activated NF-kβ dependent activation of IL-23. The function of human Th-17 cells as well as the crucial role of IL-23/Th-17 axis in the exacerbation of psoriasis and treatment have been well explored. Therefore, considering IL-23/Th17 axis as a pertinent therapeutic target in immune driven disorders, extensive investigations are now highlighting the utility of biopharmaceuticals and/or biological agents acting on these targets. Here, we review the IL-23/Th-17 axis based therapeutic targets, different types of active moieties based on their source of availability and most useful USFDA approved Mabs targeting the IL-23/Th17 axis in psoriasis for a better understanding of the future possibilities in this area.

Interleukin-17 and Interleukin-23: A Narrative Review of Mechanisms of Action in Psoriasis and Associated Comorbidities

Psoriasis is an immune-mediated inflammatory skin disease associated with numerous inflammatory comorbidities, including increased cardiovascular risk. The interleukin (IL)-23/IL-17 axis plays a central role in the immunopathogenesis of psoriasis and related comorbidities by acting to stimulate keratinocyte hyperproliferation and feed-forwarding circuits of perpetual T cell-mediated inflammation. IL-17 plays an important role in the downstream portion of the psoriatic inflammatory cascade. This review discusses the distinct mechanisms of action of IL-17 and IL-23 in the immunopathogenesis of psoriasis and related comorbidities plus the significant therapeutic benefits of selectively inhibiting these cytokines in patients with moderate to severe plaque psoriasis.

Dysregulation of the gut-brain-skin axis and key overlapping inflammatory and immune mechanisms of psoriasis and depression

The occurrence, progression and recurrence of psoriasis are thought to be related to mood and psychological disorders such as depression. Psoriasis can lead to depression, and depression, in turn, exacerbates psoriasis. No specific mechanism can explain the association between psoriasis and depression. The gut-brain-skin axis has been used to explain correlations among the gut microbiota, emotional states and systemic and skin inflammation, and this axis may be associated with overlapping mechanisms between psoriasis and depression. Therefore, in the context of the gut-brain-skin axis, we systematically summarized and comparatively analysed the inflammatory and immune mechanisms of psoriasis and depression and illustrated the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and the gut microbiota. This review provides a theoretical basis and new targets for the treatment of psoriasis and depression.

A non-clinical comparative study of IL-23 antibodies in psoriasis

Four antibodies that inhibit interleukin (IL)-23 are approved for the treatment of moderate-to-severe plaque psoriasis. Here, we present non-clinical data comparing ustekinumab, guselkumab, tildrakizumab and risankizumab with regard to thermostability, IL-23 binding affinity, inhibitory-binding mode, in vitro potency and in vivo efficacy. Risankizumab and guselkumab exhibited 5-fold higher affinity for IL-23 and showed more potent inhibition of IL-23 signaling than ustekinumab and tildrakizumab. Risankizumab and guselkumab completely blocked the binding of IL-23 to IL-23Rα as expected, whereas tildrakizumab did not. In vitro, risankizumab and guselkumab blocked the terminal differentiation of TH17 cells in a similar manner, while tildrakizumab had minimal impact on TH17 differentiation. In a human IL-23-induced ear-swelling mouse model, risankizumab and guselkumab were more effective than ustekinumab and tildrakizumab at reducing IL-17, IL-22, and keratinocyte gene expression. Our results indicate that the four clinically approved antibodies targeting IL-23 differ in affinity and binding epitope. These attributes contribute to differences in in vitro potency, receptor interaction inhibition mode and in vivo efficacy in preclinical studies as described in this report, and similarly may affect the clinical performance of these drugs.

Interleukin-17A affects extracellular vesicles release and cargo in human keratinocytes

Psoriasis is a chronic inflammatory systemic disease caused by deregulation of the interleukin-23/-17 axis that allows the activation of Th17 lymphocytes and the reprogramming of keratinocytes proliferative response, thereby inducing the secretion of cyto-/chemokines and antimicrobial peptides. Beside cell-to-cell contacts and release of cytokines, hormones and second messengers, cells communicate each other through the release of extracellular vesicles containing DNA, RNA, microRNAs and proteins. It has been reported the alteration of extracellular vesicles trafficking in several diseases, but there is scarce evidence of the involvement of extracellular vesicles trafficking in the pathogenesis of psoriasis. The main goal of the study was to characterize the release, the cargo content and the capacity to transfer bioactive molecules of extracellular vesicles produced by keratinocytes following recombinant IL-17A treatment if compared to untreated keratinocytes. A combined approach of standard ultracentrifugation, RNA isolation and real-time RT-PCR techniques was used to characterize extracellular vesicles cargo. Flow cytometry was used to quantitatively and qualitatively analyse extracellular vesicles and to evaluate cell-to-cell extracellular vesicles transfer. We report that the treatment of human keratinocytes with IL-17A significantly modifies the extracellular vesicles cargo and release. Vesicles from IL-17A-treated cells display a specific pattern of mRNA which is undid by IL-17A neutralization. Extracellular vesicles are taken up by acceptor cells irrespective of their content but only those derived from IL-17A-treated cells enable recipient cells to express psoriasis-associated mRNA. The results imply a role of extracellular vesicles in amplifying the pro-inflammatory cascade induced in keratinocyte by pro-psoriatic cytokines.

Trends in nanotechnology-based delivery systems for dermal targeting of drugs: an enticing approach to offset psoriasis

INTRODUCTION

Psoriasis is identified as an inflammatory, chronic, auto-immune disease requiring long-term treatment, imposing an unnecessary burden on the patient. A significant impediment for the treatment of dermatological disorders via transdermal route is the inability of drug molecules to cross the stratum corneum (SC), as the larger size of drug molecules inhibits them to pervade into the skin, thus hampering their absorption. Some drugs exhibit systemic side-effects, which curbs patient compliance, resulting in treatment discontinuation.

AREAS COVERED

This review aims to describe the detailed study such as demographic status, molecular factors of psoriasis, treatment with emerging combination therapy and role of nanotechnology tools in the treatment of psoriasis.

EXPERT OPINION

To overcome problems related to the conventional drug delivery system, several nanotechnology-based formulations have been devised to enhance bioavailability, drug permeation and accumulation in the skin. Nano-formulations provide better permeation, targeted delivery and enhanced efficacy, thus gaining enormous popularity for cutaneous disorders. This pervasive review provides an overview of the pathophysiology of the disease, its molecular targets and the available herbal, synthetic and combination treatment modalities. The review also systematizes recent works utilizing nano-carriers to improve the treatment denouement of psoriasis.

Dendritic cells: The driver of psoriasis

Psoriasis is a chronic skin inflammatory disorder, the immune mechanism of which has been profoundly elucidated in the past few years. The dominance of the interleukin (IL)-23/IL-17 axis is a significant breakthrough in the understanding of the pathogenesis of psoriasis, and treatment targeting IL-23 and IL-17 has successfully benefited patients with the disease. The skin contains a complex network of dendritic cells (DC) mainly composed of epidermal Langerhans cells, bone marrow-derived dermal conventional DC, plasmacytoid DC and inflammatory DC. As the prominent cellular source of α-interferon, tumor necrosis factor-α, IL-12 and IL-23, DC play a pivotal role in psoriasis. Thus, targeting pathogenic DC subsets is a valid strategy for alleviating and preventing psoriasis and other DC-derived diseases. In this review, we survey the known role of DC in this disease.

Selective Interleukin-23 p19 Inhibition: Another Game Changer in Psoriasis? Focus on Risankizumab

The history of psoriasis treatment has been marked by several milestones. Corticosteroids, cyclosporine, tumor necrosis factor alpha (TNF-α) inhibitors and, more recently, interleukin (IL)-17A inhibitors have revolutionized the treatment of psoriasis, each in its own way and time. The IL-23/IL-17 axis is currently considered to be crucial in the pathogenesis of psoriasis and selective IL-23p19 inhibition may bring several advantages with respect to IL-12/23p40 inhibition, or distal blockade of IL-17A or its receptor. In fact, IL-12 axis inhibition does not appear to be essential in psoriasis and IL-12 inhibition may even have a negative effect in the treatment of psoriasis and have potential risks in tumor immune surveillance and in host defense against intracellular pathogens. On the other hand, contrary to IL-17 inhibition, IL-23p19 blockade does not increase the risk of candida infection, nor is it associated with inflammatory bowel disease worsening. Several IL-23p19 inhibitors are currently being developed for the treatment of psoriasis, such as tildrakizumab, guselkumab, and risankizumab. Although clinical data on risankizumab is still scarce, it has shown characteristics that signify a major advance in the treatment of this disease, offering comparable or higher efficacy than IL-17 inhibitors, without the safety concerns of this therapeutic class, combined with the excellent dosing regimen of ustekinumab. Currently, only phase II trial data is available; thus, the results of the large phase III trials will be essential to establish the efficacy and safety profile of risankizumab and its value in the biological armamentarium for the treatment of psoriatic patients.

Spotlight on risankizumab and its potential in the treatment of plaque psoriasis: evidence to date

Psoriasis is a common chronic immune-mediated skin disease, with systemic involvement and significant impact in patients’ quality of life. Several highly specific treatments have been developed over the years, such as tumor necrosis factor-α inhibitors, a nonselective IL-23 inhibitor (ustekinumab), and most recently IL-17 inhibitors. Risankizumab is a monoclonal antibody which targets IL-23p19 without binding IL-12. This novel therapeutic approach is expected to have advantages over the recently approved anti-IL-17 agents, such as the avoidance of Candida infections and neutropenia. In addition, unlike ustekinumab, the selective inhibition of IL-23 may preserve IL-12-dependent functions such as protection against infections and tumor immune surveillance. Risankizumab showed an excellent efficacy when compared to placebo and ustekinumab, with higher Psoriasis Area Severity Index (PASI) 75, PASI 90, and PASI 100 rates, along with a convenient every 12-week maintenance dosing regimen. Overall, risankizumab was well tolerated and the most common adverse event was upper respiratory tract infection. In the near future, further data will be available not only in psoriasis but also in Crohn’s disease and psoriatic arthritis fields. Head-to-head trials comparing risankizumab with other IL-23 inhibitors and with IL-17 inhibitors will be crucial to reveal the role of risankizumab in the treatment of psoriasis.

Targeting the IL-23/IL-17 Pathway in Psoriasis: the Search for the Good, the Bad and the Ugly

New promising treatments have been developed for psoriasis that target different parts of the interleukin (IL)-23/IL-17 pathway. This approach is believed to be more disease specific, and sparing the T helper 1 pathway might prevent serious long-term adverse events. Moreover, superior Psoriasis Area and Severity Index improvements are observed, which has redefined treatment goals in psoriasis. The new molecules can be divided into different categories, according to the target: blocking agents can target the upstream cytokine IL-23 or the downstream IL-17. In the latter, a variety of targets exist, such as the ligands IL-17A and IL-17F, or a combination thereof, or a subunit of the receptor, IL-17RA. Each target seems to have its own set of advantages and pitfalls, which will impact the treatment decision in clinical practice. In this review, we summarize the current knowledge on the different inhibitors of the IL-23/IL-17 pathway. Furthermore, we briefly discuss the role of IL-17 in other diseases and comorbidities. Finally, we discuss how comprehensive knowledge is needed for the prescribing physician in order to make the most appropriate therapeutic choice for each individual patient.

Guselkumab for the Treatment of Psoriasis

Psoriasis is a common, chronic, immune-mediated, inflammatory skin disease with systemic involvement and significant impact on patients' quality of life. Several biologic treatments have been developed in recent decades, such as tumor necrosis factor (TNF)-α inhibitors, a non-selective interleukin (IL)-23 inhibitor (ustekinumab, which also inhibits IL-12), and-most recently-IL-17 inhibitors. Guselkumab is a novel biological therapy that selectively targets IL-23 and is the first-in-class selective IL-23 inhibitor approved to treat moderate-to-severe plaque psoriasis. These inhibitors are expected to have some advantages over the highly effective IL-17 inhibitors, as they do not worsen inflammatory bowel disease and are not involved in the development of candida infections. Additionally, selective inhibition of IL-23 may have additional benefits over ustekinumab as the IL-12-dependent cascades remain functional. These benefits include a decrease in IL-17A-producing T cells in the skin and the promotion of an anti-inflammatory effect through production of interferon-γ and IL-10. In terms of efficacy, guselkumab showed promising results in the treatment of psoriasis and psoriatic arthritis, although it did not show significant clinical improvement in rheumatoid arthritis. Studies in other inflammatory diseases and Crohn's disease are expected to begin soon. Overall, guselkumab was well tolerated; the most common adverse event was nasopharyngitis. Head-to-head studies comparing IL-23 inhibitors with agents in different classes, namely IL-17 inhibitors, will be crucial to establish the true role of these agents in psoriasis treatment.

Tildrakizumab for the treatment of psoriasis

Psoriasis is a chronic skin disorder driven by IL-23 and the downstream T-helper cell 17 (Th17) pathway. Tildrakizumab is a humanized monoclonal antibody selectively targeting the p19 subunit of IL-23, a key cytokine for Th17 cells. Here, we provide an overview of IL-23 in the context of psoriasis pathogenesis and review the results of the Phase I, II and III clinical trials for tildrakizumab in patients with moderate-to-severe chronic plaque psoriasis in order to assess its efficacy, safety and clinical usefulness. In all clinical trials, tildrakizumab demonstrated significant clinical improvement and a favorable safety profile. In Phase III trials, 75% of tildrakizumab-treated patients reached a Psoriasis Area and Severity Index 75 at week 28 demonstrating superior efficacy as compared with etanercept treatment. The tildrakizumab-induced reduction in skin inflammation proves the important pathogenic role of IL-23 in psoriasis and further supports the utility of drugs targeting the IL-23/Th17 pathway. Targeting IL-23p19 with tildrakizumab augments the therapeutic repertoire for patients with moderate-to-severe chronic plaque psoriasis.

Ichthyosis molecular fingerprinting shows profound TH17 skewing and a unique barrier genomic signature

BACKGROUND

Ichthyoses are a group of rare skin disorders lacking effective treatments. Although genetic mutations are progressively delineated, comprehensive molecular phenotyping of ichthyotic skin could suggest much-needed pathogenesis-based therapy.

OBJECTIVE

We sought to profile the molecular fingerprint of the most common orphan ichthyoses.

METHODS

Gene, protein, and serum studies were performed on skin and blood samples from 29 patients (congenital ichthyosiform erythroderma, n = 9; lamellar ichthyosis, n = 8; epidermolytic ichthyosis, n = 8; and Netherton syndrome, n = 4), as well as age-matched healthy control subjects (n = 14), patients with psoriasis (n = 30), and patients with atopic dermatitis (AD; n = 16).

RESULTS

Using criteria of a fold change of greater than 2 and a false discovery rate of less than 0.05, 132 differentially expressed genes were shared commonly among all ichthyoses, including many IL-17 and TNF-α-coregulated genes, which are considered hallmarks of psoriasis (defensin beta 4A, kynureninase, and vanin 3). Although striking upregulation of TH17 pathway genes (IL17F and IL36B/G) resembling that seen in patients with psoriasis was common to all patients with ichthyoses in a severity-related manner, patients with Netherton syndrome showed the greatest T-cell activation (inducible costimulator [ICOS]) and a broader immune phenotype with T_H1/IFN-γ, OASL, and T_H2/IL-4 receptor/IL-5 skewing, although less than seen in patients with AD (all P < .05). Ichthyoses lacked the epidermal differentiation and tight junction alterations of patients with AD (loricrin, filaggrin, and claudin 1) but showed characteristic alterations in lipid metabolism genes (ELOVL fatty acid elongase 3 and galanin), with parallel reductions in extracellular lipids and corneocyte compaction in all ichthyoses except epidermolytic ichthyosis, suggesting phenotypic variations. Transepidermal water loss, a functional barrier measure, significantly correlated with IL-17-regulated gene expression (IL17F and IL36A/IL36B/IL36G).

CONCLUSION

Similar to patients with AD and psoriasis, in whom cytokine dysregulation and barrier impairment orchestrate disease phenotypes, psoriasis-like immune dysregulation and lipid alterations characterize the ichthyoses. These data support the testing of IL-17/IL-36-targeted therapeutics for patients with ichthyosis similar to those used in patients with psoriasis.

Scanning the Immunopathogenesis of Psoriasis

Psoriasis is a chronic inflammatory skin disease, the immunologic model of which has been profoundly revised following recent advances in the understanding of its pathophysiology. In the current model, a crosstalk between keratinocytes, neutrophils, mast cells, T cells, and dendritic cells is thought to create inflammatory and pro-proliferative circuits mediated by chemokines and cytokines. Various triggers, including recently identified autoantigens, Toll-like receptor agonists, chemerin, and thymic stromal lymphopoietin may activate the pathogenic cascade resulting in enhanced production of pro-inflammatory and proliferation-inducing mediators such as interleukin (IL)-17, tumor necrosis factor (TNF)-α, IL-23, IL-22, interferon (IFN)-α, and IFN-γ by immune cells. Among these key cytokines lie therapeutic targets for currently approved antipsoriatic therapies. This review aims to provide a comprehensive overview on the immune-mediated mechanisms characterizing the current pathogenic model of psoriasis.

Interleukin-17 alters the biology of many cell types involved in the genesis of psoriasis, systemic inflammation and associated comorbidities

Psoriasis is a chronic, immune-mediated, systemic inflammatory disease that is defined by a characteristic skin reaction produced when elevated levels of inflammatory cytokines such as interleukin (IL)-17 alter the growth and differentiation of skin cells. The pathogenesis of comorbid conditions associated with psoriasis, including psoriatic arthritis, cardiovascular disease, obesity, metabolic syndrome, liver disorders, renal disease and depression, is also largely affected by inflammation. In this review, we examine the effect of IL-17 on the inflammatory pathways in a variety of different cell types, including keratinocytes, as well as epithelial cells of the colon, kidney, gut and liver. Additionally, we investigate the role of IL-17 in mediating the psoriasis-associated comorbidities detailed above.

Moderate to severe psoriasis treatment challenges through the era of biological drugs

Biological therapy has revolutionized moderate to severe psoriasis treatment. However, despite being more effective than conventional systemic treatments, some patients do not respond or lose response to biotechnological treatments or develop drug-antibodies, interfering with its safety and efficacy. There are also clinical forms of the disease and patient profiles for which is pending further scientific evidence for more sustained therapeutic interventions. The continuous and more detailed knowledge of psoriasis pathophysiology has allowed identifying new therapeutic targets, which is expected to help overcome the challenges of individualized psoriasis treatment.

A new therapeutic for the treatment of moderate-to-severe plaque psoriasis: apremilast

Psoriasis is a common, chronic, inflammatory skin disease. Being a life-long condition, a prolonged and safe control of the disease is needed. Current anti-psoriatic treatments show some limits in terms of tolerability and route of administration. Recently, a new oral small molecule, apremilast, has been approved for the treatment of patients with moderate-to-severe plaque psoriasis. Apremilast is a phosphodiesterase 4 (PDE4) inhibitor that regulates the transduction of intracellular signals, including pro-inflammatory and anti-inflammatory pathways. Because of the favorable safety profile and the oral route of administration, apremilast may represent a promising therapeutic target for moderate-to-severe psoriasis. In this review, we report an updated overview about clinical trials testing apremilast in the treatment of psoriasis and seek to provide comprehensive information about this anti-psoriatic drug and a future perspective of the therapeutic algorithm for psoriasis.

Serum amyloid A, an acute phase protein, stimulates proliferative and proinflammatory responses of keratinocytes

OBJECTIVES

Serum amyloid A (SAA), an acute phase protein, is highly expressed in psoriatic lesions but its function is not fully understood. The aim of this study was to explore its role in activation of keratinocytes.

MATERIALS AND METHODS

Real-time PCR and immunofluorescence were performed to examine SAA expression in imiquimod (IMQ)-induced psoriasis-like mice. In vivo function of SAA was examined by treating psoriasis-like mice with SAA neutralising antibody. Cell viability was monitored using the CCK-8 assay. Real-time PCR was performed to determine expression of genes associated with differentiation and inflammation. Ki67⁺ percentage and immunological markers were analysed by flow cytometry. Involvement of formyl peptide receptor-like 1 (FPRL1) in SAA signal transduction was determined by RNA interference. Binding of SAA and FPRL1 was examined by co-immunoprecipitaion. Western blotting was conducted to assess phosphorylation of downstream signalling molecules.

RESULTS

SAA was highly expressed in skin lesions of IMQ-treated psoriasis-like mice and neutralising SAA attenuated epidermal hyperplasia and inflammation. SAA in vitro promoted keratinocyte proliferation and expression of immunological mediators, while inhibiting differentiation. Effects of SAA on keratinocyte proliferation and inflammation were mediated by FPRL1, as well as activation of the PI3K/Akt pathway.

CONCLUSIONS

These observations indicate that SAA/FPRL1 contributed to pathogenesis of psoriasis by promoting keratinocyte proliferation and inflammation, thus providing a potential therapeutic target for disease therapy.

The 'omics' revolution: redefining the understanding and treatment of allergic skin diseases

PURPOSE OF REVIEW

To evaluate how the genomic, transcriptomic, and proteomic profiles of allergic skin diseases, like atopic dermatitis and allergic contact dermatitis, contribute to their understanding and promote their therapeutic development.

RECENT FINDINGS

The '-omics' revolution has facilitated the quantification of inflammatory skin diseases at the molecular level, expanding our understanding of disease pathogenesis. It has also greatly expanded once-limited treatment options and improved the ability to define posttreatment improvements, beyond clinical scores. The findings on the genomic/transcriptomic level are also complemented by proteomic data, contributing to the understanding of the later changes taking place in the final stages of protein formation. Atopic dermatitis is defined as a Th2/Th22 polarized disease with some contributions of Th17 and Th1 pathways. In atopic dermatitis, studies of biologics and small molecules, targeting specific pathways upregulated in atopic dermatitis, seem to provide well tolerated alternatives to conventional immunosuppressive therapies (i.e. corticosteroids and cyclosporine A), particularly for severe patients. Allergic contact dermatitis is defined as having Th1/Th17-centered inflammation, especially with nickel-induced disease, but additional pathways, including Th2 and Th22, are upregulated with other allergens (i.e. fragrance).

SUMMARY

Supplementing studies of allergic skin diseases with '-omics' approaches are transforming the pathogenic understanding, diagnosis and, perhaps, also the treatment of these diseases.

Palmoplantar pustular psoriasis (PPPP) is characterized by activation of the IL-17A pathway

BACKGROUND

Palmoplantar pustular psoriasis (PPPP) is a variant of psoriasis, which has significant negative impact on quality of life. The cellular and molecular inflammatory pathways involved in PPPP have not been well studied.

OBJECTIVE

Study the expression of cytokines and chemokines involved in the IL-17/IL-23 axis in palmoplantar pustular psoriasis and other difficult to treat psoriasis areas (palms, scalp, elbows and lower legs).

METHODS

Skin biopsies were performed on a total of 80 patients with PPPP, non-pustular palmoplantar psoriasis (NPPPP), or psoriasis located on elbows, knees and scalp as well as 10 healthy subjects. RT-PCR, immunohistochemistry and flow cytometry on cells extracted from skin biopsies were used to compare PPPP to other forms of psoriasis.

RESULTS

There was a significant (p<0.05) increase in the expression of IL-1β, IL-6, LL-37, IL-19, IL-17A, CXCL1 and CXCL2 in PPPP as compared to NPPPP. However, there was no significant difference in expression of IL-23 in PPPP as compared to NPPPP and other forms of psoriasis. The proportion of IL-22⁺ but not IL-17A⁺ mast cells was higher in PPPP as compared to NPPPP (p<0.05).

CONCLUSION

These results suggest that the IL-17A pathway may play a more important role in PPPP than in NPPPP.

An IL-17-dominant immune profile is shared across the major orphan forms of ichthyosis

BACKGROUND

The ichthyoses are rare genetic disorders associated with generalized scaling, erythema, and epidermal barrier impairment. Pathogenesis-based therapy is largely lacking because the underlying molecular basis is poorly understood.

OBJECTIVE

We sought to characterize molecularly cutaneous inflammation and its correlation with clinical and barrier characteristics.

METHODS

We analyzed biopsy specimens from 21 genotyped patients with ichthyosis (congenital ichthyosiform erythroderma, n = 6; lamellar ichthyosis, n = 7; epidermolytic ichthyosis, n = 5; and Netherton syndrome, n = 3) using immunohistochemistry and RT-PCR and compared them with specimens from healthy control subjects, patients with atopic dermatitis (AD), and patients with psoriasis. Clinical measures included the Ichthyosis Area Severity Index (IASI), which integrates erythema (IASI-E) and scaling (IASI-S); transepidermal water loss; and pruritus.

RESULTS

Ichthyosis samples showed increased epidermal hyperplasia (increased thickness and keratin 16 expression) and T-cell and dendritic cell infiltrates. Increases of general inflammatory (IL-2), innate (IL-1β), and some T_H1/interferon (IFN-γ) markers in patients with ichthyosis were comparable with those in patients with psoriasis or AD. TNF-α levels in patients with ichthyosis were increased only in those with Netherton syndrome but were much lower than in patients with psoriasis and those with AD. Expression of T_H2 cytokines (IL-13 and IL-31) was similar to that seen in control subjects. The striking induction of IL-17-related genes or markers synergistically induced by IL-17 and TNF-α (IL-17A/C, IL-19, CXCL1, PI3, CCL20, and IL36G; P < .05) in patients with ichthyosis was similar to that seen in patients with psoriasis. IASI and IASI-E scores strongly correlated with IL-17A (r = 0.74, P < .001) and IL-17/TNF-synergistic/additive gene expression. These markers also significantly correlated with transepidermal water loss, suggesting a link between the barrier defect and inflammation in patients with ichthyosis.

CONCLUSION

Our data associate a shared T_H17/IL-23 immune fingerprint with the major orphan forms of ichthyosis and raise the possibility of IL-17-targeting strategies.

Anti-TNF agents for paediatric psoriasis

BACKGROUND

Psoriasis is a chronic skin disease that may develop at any age. Estimates for the United States and Europe suggest that psoriasis accounts for 4% of skin diseases in children. In most cases, the condition is mild and can be treated with creams. However, a small percentage of children have moderate to severe disease that requires drugs, such as ciclosporin or methotrexate, and some will require injections with newer biological agents, such as anti-TNF (tumour necrosis factor) drugs. Anti-TNF drugs (among them etanercept, infliximab, and adalimumab) are designed to reduce inflammation in the body caused by tumour necrosis factor. Evidence for the safety and efficacy of these biological agents in paediatric psoriasis is lacking.

OBJECTIVES

To assess the efficacy and safety of anti-TNF agents for the treatment of paediatric psoriasis.

SEARCH METHODS

We searched the following databases up to July 2015: the Cochrane Skin Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL; 2015, Issue 6), MEDLINE (from 1946), Embase (from 1974), and LILACS (from 1982). We also searched 13 trials registers and checked the reference lists of included studies and key review articles for further references to relevant randomised controlled trials (RCTs). We handsearched conference proceedings and attempted to contact trial authors and relevant pharmaceutical manufacturers. We searched the US Food and Drug Administration's and European Medicines Agency's adverse effects databases.

SELECTION CRITERIA

All relevant RCTs that evaluated the efficacy and safety of anti-TNF agents for the treatment of chronic plaque psoriasis in individuals less than 18 years of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently checked titles and abstracts and performed data extraction and 'Risk of bias' assessment of the included studies. One review author entered data into Review Manager (RevMan), and a second review author checked the data. We also attempted to obtain unclear data from the trial authors where possible.Our primary outcomes were investigator-assessed number of participants achieving a 75% improvement in Psoriasis Area and Severity Index-75 (PASI 75) compared to baseline, improvement in quality of life using an instrument such as Children's Dermatology Life Quality Index (CDLQI), and adverse effects. Our secondary outcomes included the proportion of participants achieving PASI 50 and the Physician's Global Assessment (PGA).

MAIN RESULTS

We included one study with 211 participants (median age 13 years), in which etanercept (dosage ranged from 0.8 to 50 mg per kilogram of body weight) was compared to placebo. Follow-up was over a 48-week period.At week 12, 57% versus 11% who received etanercept or placebo, respectively, achieved the PASI 75 (risk ratio 4.95, 95% confidence interval (CI) 2.83 to 8.65; high-quality evidence). Absolute risk reduction and the number needed to treat to obtain a benefit with etanercept was 45% (95% CI 33.95 to 56.40) and 2 (95% CI 1.77 to 2.95), respectively.The percentage improvement from baseline of the CDLQI scores at week 12 was better in the etanercept group than the placebo group (52.3% versus 17.5%, respectively (P = 0.0001)). Analysis between the groups showed an effect size that was clinically important (mean difference 2.30, 95% CI 0.85 to 3.75; high-quality evidence). However, means, medians, and minimal important difference results and results of the Pediatric Quality of Life Inventory, Stein Impact on Family Scale, and Harter Self-Perception Profile for Children scores must be interpreted with caution, as they were not prespecified outcomes.Three serious adverse events were reported, but they were resolved without sequelae. Deaths or other events such as malignant tumours, opportunistic infections, tuberculosis, or demyelination were not reported in the included study.Also, 13% of participants in the placebo group and 53% in the etanercept group had a PGA of clear or almost clear (risk ratio 3.96, 95% CI 2.36 to 6.66; high-quality evidence) at week 12.

AUTHORS' CONCLUSIONS

This review found only one RCT evaluating the use of this type of biological therapy. Although the risk of publication bias was high, as we included only one industry-sponsored RCT, the risk of allocation, selection, performance, attrition, and selective reporting biases for all outcomes (except for CDLQI) was low, and no short-term serious adverse events were found.We can conclude, based on this single included study, that etanercept seems to be efficacious and safe (at least in the short term) for the treatment of paediatric psoriasis. However, as the GRADE approach refers not to individual studies but to a body of evidence, we shall wait for the results of the ongoing studies in a future update of this review. In addition, future studies should evaluate quality-of-life endpoints established a priori and standardise primary outcome measures such as PASI 75, and should include the PGA as a secondary endpoint. Also, collating and reporting adverse events uniformly is required to better evaluate safety.

Circadian Gene Clock Regulates Psoriasis-Like Skin Inflammation in Mice

There are several reports suggesting that the pathophysiology of psoriasis may be associated with aberrant circadian rhythms. However, the mechanistic link between psoriasis and the circadian time-keeping system, “the circadian clock,” remains unclear. This study determined whether the core circadian gene, Clock, had a regulatory role in the development of psoriasis. For this purpose, we compared the development of psoriasis-like skin inflammation induced by the Toll-like receptor 7 ligand imiquimod (IMQ) between wild-type mice and mice with a loss-of-function mutation of Clock. We also compared the development of IMQ-induced dermatitis between wild-type mice and mice with a loss-of-function mutation of Period2 (Per2), another key circadian gene that inhibits CLOCK activity. We found that Clock mutation ameliorated IMQ-induced dermatitis, whereas the Per2 mutation exaggerated IMQ-induced dermatitis, when compared with wild-type mice associated with decreased or increased IL-23 receptor (IL-23R) expression in γ/δ⁺ T cells, respectively. In addition, CLOCK directly bound to the promoter of IL-23R in γ/δ⁺ T cells, and IL-23R expression in the mouse skin was under circadian control. These findings suggest that Clock is a novel regulator of psoriasis-like skin inflammation in mice via direct modulation of IL-23R expression in γ/δ⁺ T cells, establishing a mechanistic link between psoriasis and the circadian clock.

Insights into IL-23 biology: From structure to function

Interleukin (IL-)23 is a central cytokine controlling TH17 development. Overshooting IL-23 signaling contribute to autoimmune diseases. Moreover, GWAS studies have identified several SNPs within the IL-23 receptor, which are associated with autoimmune diseases. IL-23 is a member of the IL-12-type cytokine family and consists of IL-23p19 and p40. Within the IL-12 family, IL-12 and IL-23 share the p40 cytokine subunit and the IL-12Rβ1 as one chain of the receptor complex. For signaling, IL-23 triggers heterodimerization of IL-12Rβ1 and the IL-23R. Subsequently, signal transduction pathways including JAK/STAT, MAPK and PI3K are activated. Most studies have investigated the biological relevance of IL-23 in the development of TH17 cells and autoimmunity, whereas less is known about the molecular context of IL-23 biology. Therefore, we focused on IL-23 receptor complex assembly, signal transduction and functional relevance of IL-23R SNPs in the context of IL-23-inhibitory principles.

IL-12 and IL-23 cytokines: from discovery to targeted therapies for immune-mediated inflammatory diseases

The cytokine interleukin-12 (IL-12) was thought to have a central role in T cell-mediated responses in inflammation for more than a decade after it was first identified. Discovery of the cytokine IL-23, which shares a common p40 subunit with IL-12, prompted efforts to clarify the relative contribution of these two cytokines in immune regulation. Ustekinumab, a therapeutic agent targeting both cytokines, was recently approved to treat psoriasis and psoriatic arthritis, and related agents are in clinical testing for a variety of inflammatory disorders. Here we discuss the therapeutic rationale for targeting these cytokines, the unintended consequences for host defense and tumor surveillance and potential ways in which these therapies can be applied to treat additional immune disorders.