Pustular psoriasis: Molecular pathways and effects of spesolimab in generalized pustular psoriasis

Successful treatment of recalcitrant generalized pustular psoriasis of pregnancy with spesolimab

Generalized pustular psoriasis (GPP) in pregnancy can lead to severe complications for both mother and fetus. The treatment of this disease is challenging, especially in recalcitrant and severe cases. Until present, there are no evidence-based guidelines for the treatment of GPP in pregnancy. Spesolimab, a human monoclonal antibody against the IL-36 receptor, has recently attracted attention as a new therapy for GPP flare. This biologic provides rapid and sustained control of symptoms of GPP flare, although its use in pregnant women has not been reported to date. Here, we report a pregnant woman with refractory GPP who did not respond well to systemic steroids. Administration of spesolimab resulted in complete control of the disease and the birth of a healthy baby. Our case demonstrates that IL-36RN inhibitors are a potentially effective and safe treatment option for GPP in pregnancy.

Targeted review of IL36RN mutations in patients with generalised pustular psoriasis

Background

Generalised pustular psoriasis (GPP) is a rare and chronic skin disease historically treated with therapies that were originally intended to treat plaque psoriasis (PsO). However, GPP and plaque PsO have distinct pathogeneses and clinical courses.

Objectives

This study aimed to further characterise the unique genetic background of GPP by summarising evidence on the frequency and type of IL36RN gene mutation, a gene that normally suppresses proinflammatory responses, in patients with GPP compared to patients with GPP and plaque PsO, and patients with plaque PsO only.

Methods and Results

A targeted literature review was conducted to identify studies reporting IL36RN mutations and/or HLA-Cw6 allele frequency in patients with GPP. Meta-analyses showed a significantly higher rate of IL36RN mutations in the GPP-only population compared to the GPP + plaque PsO population (OR 3.51; 95% CI 2.29, 5.38). Monoallelic mutations of IL36RN were found in up to 33.3%, and biallelic mutations in up to 73.2% of patients with GPP (GPP-only and GPP + plaque PsO), in contrast with mono- and biallelic frequencies of only 0%-11.9% and 0%, respectively, in patients with plaque PsO only. Mean age-of-onset ranged from 5.9 to 48.9 years old, with most studies reporting a GPP age-of-onset between 20 and 40 years old. Twenty-one mutations were identified in the biallelic state and three in monoallelic. The most reported mutations were c.115 + 6T > C (p. Arg10ArgfsX1) (18 studies); c.227 C > T (p.Pro76Leu) (10 studies); and c.338 C > T (p.Ser113Leu) (8 studies). Mutations varied depending on geography and ethnicity, with the most frequently reported mutation predominantly reported in East Asian studies and international studies that included Asian patients. Rates of HLA-Cw6, the risk allele most strongly associated with plaque PsO, were 0%-28.6% for patients with GPP, similar to rates in the general population (10.5%-20%).

Conclusion

Considering the differences between GPP and plaque PsO in aetiology and disease symptoms, effective, GPP-specific treatment options are needed, and recent research suggests that blockade of IL-36 signalling may be an effective target for treatment of GPP.

Increased neutrophil-derived IL-17A identified in generalized pustular psoriasis

Generalized pustular psoriasis (GPP) is considered to be a distinct clinical entity from psoriasis vulgaris (PV), with different clinical and histological manifestations. The pathogenesis of GPP has not been thoroughly elucidated, especially in those patients lacking interleukin (IL)36RN. In present study, we performed RNA sequence analysis on skin lesions from 10 GPP patients (4 with and 6 without IL36RN mutation) and 10 PV patients without IL36RN mutation. Compared with PV, significantly overexpressed genes in GPP patients were enriched in IL-17 signalling pathway (MMP1, MMP3, DEFB4A and DEFB4B, etc.) and associated with neutrophil infiltration (MMP1, MMP3, ANXA and SERPINB, etc.). GPP with IL36RN mutations evidenced WNT11 upregulation and IL36RN downregulation in comparison to those GPP without IL36RN mutations. The expression of IL-17A/IL-36 in skin or serum and the origin of IL-17A in skin were also investigated. IL-17A expression in skin was significantly higher in GPP than PV patients, whereas, there were no differences in skin IL-36α/IL-36γ/IL-36RA or serum IL-17A/IL-36α/IL-36γ between GPP than PV. Besides, double immunofluorescence staining of MPO/IL-17A or CD3/IL-17A further confirmed that the majority of IL-17A in GPP skin was derived from neutrophils, but not T cells. These data emphasized the role of neutrophil-derived IL-17A in the pathogenesis of GPP with or without IL36RN mutations. Targeting neutrophil-derived IL-17A might be a promising treatment for GPP.

Spesolimab for the Treatment of Generalized Pustular Psoriasis

Generalized pustular psoriasis (GPP) is a rare but severe skin inflammatory disorder characterized by the eruption of widespread sterile neutrophilic pustules, often accompanied by systemic inflammation. Given its life-threatening potential, GPP requires prompt accurate diagnosis and effective treatment, but its rarity and relapsing-remitting nature pose challenges in performing large-scale randomized controlled clinical trials. Established international guidelines are currently lacking and management guidance often follows that for plaque psoriasis. However, while it can co-exist with plaque psoriasis and has traditionally been classified as a most severe form of psoriasis, GPP is now recognized as a distinct entity, with its own clinicopathological, autoinflammatory, immunologic and genetic features. Research conducted over the past decade revealed that an imbalance of interleukin (IL)-36 signaling favoring the proinflammatory activity is the central driver of the pathogenesis of GPP, thereby laying the groundwork for the development of targeted therapies for the disease. This article reviews the evidence thus far on spesolimab, a selective humanized antibody against the IL-36 receptor that was recently licensed in Europe and the United States for the treatment of GPP flares in adults. In phase II, randomized controlled clinical trials, spesolimab led to rapid and effective skin clearance in patients experiencing a GPP flare and demonstrated superiority to placebo in preventing flares for up to 48 weeks with maintenance treatment, with reassuring safety and tolerability profiles. Spesolimab is considered to be a first-in-class medication establishing itself as the standard of care for the treatment of GPP flares, thus changing the paradigm of the management of GPP to a new era of scientifically- and evidence-based targeted therapy for this distinctive disease.

Spesolimab: a comprehensive review on the anti-IL-36 receptor antibody in dermatology

Interleukin-36 (IL-36) cytokines contribute to the pathogenesis of various inflammatory skin conditions and are potential therapeutic targets. Spesolimab is a monoclonal antibody that inhibits IL-36 signaling recently approved by the Food and Drug Administration for the management of generalized pustular psoriasis flares in adults. Clinical trials are evaluating the efficacy of this monoclonal antibody in a few other dermatological conditions. Here, this review comprehensively summarizes the safety and efficacy of spesolimab treatment in various dermatological conditions.

Cutaneous findings and treatments in deficiency of interleukin-36 receptor antagonist (DITRA): A review of the literature

Deficiency of the interleukin-36 receptor antagonist (DITRA) is a rare autoinflammatory disorder caused by mutations in the IL36RN gene. This mutation leads to a lack of functional interleukin-36 receptor antagonists (IL-36Ra), which results in an overactive immune system and chronic inflammation. Despite its rarity, numerous case series and individual reports in the literature emphasize the importance of recognizing and managing DITRA. Early identification of the cutaneous signs of DITRA is crucial for accurate diagnosis and timely administration of appropriate treatment. This review article provides a comprehensive overview of the current understanding of the cutaneous, non-cutaneous and histopathological manifestations of DITRA, with a focus on reported treatments. The disease typically presents in early childhood, although the age of onset can vary. Patients with DITRA exhibit recurrent episodes of skin inflammation, often with a pustular or pustular psoriasis-like appearance. Additionally, non-cutaneous manifestations are common, with recurrent fevers and elevated acute-phase reactants being the most prevalent. The exact prevalence of DITRA is unknown. Some cases of loss-of-function mutations in the IL36RN gene, considered a hallmark for diagnosis, have been identified in patients with familial generalized pustular psoriasis (GPP). Biological therapies with inhibition of IL-12/23 and IL-17 are promising treatment options; paediatric patients with DITRA have shown complete response with mild relapses. New and emerging biologic therapeutics targeting the IL-36 pathway are also of interest in the management of this rare autoinflammatory disorder.

IL-17A-driven psoriasis is critically dependent on IL-36 signaling

Plaque psoriasis is an autoinflammatory and autoimmune skin disease, affecting 1-3% of the population worldwide. Previously, high levels of IL-36 family cytokines were found in psoriatic skin lesions, thereby contributing to keratinocyte hyperproliferation and infiltration of immune cells such as neutrophils. While treatment with anti-IL36 receptor (IL36R) antibodies was recently approved for generalized pustular psoriasis (GPP), it remains unclear, if targeting the IL36R might also inhibit plaque psoriasis. Here we show that antibody-mediated inhibition of IL36R is sufficient to suppress imiquimod-induced psoriasis-like skin inflammation and represses the disease's development in a model that depends on IL-17A overexpression in the skin. Importantly, treatment with anti-IL36R antibodies inhibited skin inflammation and attenuated psoriasis-associated, systemic inflammation. This is possibly due to a widespread effect of IL36R inhibition, which not only suppresses pro-inflammatory gene expression in keratinocytes, but also the activation of other immune cells such as T-cells or dendritic cells. In conclusion, we propose that inhibition of the IL-36 signaling pathway might constitute an attractive, alternative approach for treating IL-17A-driven psoriasis and psoriasis-linked comorbidities.

Autoinflammatory Keratinization Diseases-The Concept, Pathophysiology, and Clinical Implications

Recent advances in medical genetics elucidated the background of diseases characterized by superficial dermal and epidermal inflammation with resultant aberrant keratosis. This led to introducing the term autoinflammatory keratinization diseases encompassing entities in which monogenic mutations cause spontaneous activation of the innate immunity and subsequent disruption of the keratinization process. Originally, autoinflammatory keratinization diseases were attributed to pathogenic variants of CARD14 (generalized pustular psoriasis with concomitant psoriasis vulgaris, palmoplantar pustulosis, type V pityriasis rubra pilaris), IL36RN (generalized pustular psoriasis without concomitant psoriasis vulgaris, impetigo herpetiformis, acrodermatitis continua of Hallopeau), NLRP1 (familial forms of keratosis lichenoides chronica), and genes of the mevalonate pathway, i.e., MVK, PMVK, MVD, and FDPS (porokeratosis). Since then, endotypes underlying novel entities matching the concept of autoinflammatory keratinization diseases have been discovered (mutations of JAK1, POMP, and EGFR). This review describes the concept and pathophysiology of autoinflammatory keratinization diseases and outlines the characteristic clinical features of the associated entities. Furthermore, a novel term for NLRP1-associated autoinflammatory disease with epithelial dyskeratosis (NADED) describing the spectrum of autoinflammatory keratinization diseases secondary to NLRP1 mutations is proposed.

In Silico and In Vitro Analysis of IL36RN Alterations Reveals Critical Residues for the Function of the Interleukin-36 Receptor Complex

Generalized pustular psoriasis is a potentially life-threatening skin disease, associated with IL36RN disease alleles. IL36RN encodes the IL-36 receptor antagonist (IL-36Ra), a protein that downregulates the activity of IL-36 cytokines by blocking their receptor (IL-36R). Although generalized pustular psoriasis can be treated with IL-36R inhibitors, the structural underpinnings of the IL-36Ra/IL-36R interaction remain poorly understood. In this study, we sought to address this question by systematically investigating the effects of IL36RN sequence changes. We experimentally characterized the effects of 30 IL36RN variants on protein stability. In parallel, we used a machinelearning tool (Rhapsody) to analyze the IL-36Ra three-dimensional structure and predict the impact of all possible amino acid substitutions. This integrated approach identified 21 amino acids that are essential for IL-36Ra stability. We next investigated the effects of IL36RN changes on IL-36Ra/IL-36R binding and IL-36R signaling. Combining invitro assays and machine learning with a second program (mCSM), we identified 13 amino acids that are critical for IL-36Ra/IL36R engagement. Finally, we experimentally validated three representative predictions, further confirming the reliability of Rhapsody and mCSM. These findings shed light on the structural determinants of IL-36Ra activity, with potential to facilitate the design of new IL-36 inhibitors and aid the interpretation of IL36RN variants in diagnostic settings.

The role of the interleukin-36 axis in generalized pustular psoriasis: a review of the mechanism of action of spesolimab

Generalized pustular psoriasis (GPP) is a rare, chronic, inflammatory skin disorder characterized by recurrent flares associated with skin erythema, desquamation, and widespread superficial sterile pustules, which may be severe ("lakes of pus"). Systemic symptoms are often present, including malaise, fever, and skin pain. In GPP, innate immune responses are driven by abnormal activation of the interleukin (IL)-36-chemokine-neutrophil axis and excessive neutrophil infiltration. This review highlights the IL-36 pathway in the context of the IL-1 superfamily and describes how unopposed IL-36 signaling can lead to the development of GPP. Targeted inhibition of the IL-36 receptor (IL-36R) is an attractive therapeutic strategy in the treatment of GPP, including flare prevention and sustained disease control. Spesolimab is a first-in-class, humanized, monoclonal antibody that binds specifically to the IL-36R and antagonizes IL-36 signaling. Spesolimab was approved by the US Food and Drug Administration in September 2022 to treat GPP flares in adults and was subsequently approved for GPP flare treatment in other countries across the world. Anti-IL-36R therapy, such as spesolimab, can mitigate flares and address flare prevention in GPP, presumably through rebalancing IL-36 signaling and modulating the pro-inflammatory response of the downstream effectors.

Generalized pustular psoriasis: practical recommendations for Spanish primary care and emergency physicians

Generalized pustular psoriasis (GPP) is a rare chronic inflammatory skin disease that can lead to life-threatening complications and require emergency medical treatment. Recurrent GPP flares are characterized by the sudden onset of widespread erythematous skin rash with sterile pustules, at times associated with fever, chills, general malaise, and other systemic inflammatory manifestations. Systemic complications such as cardiorespiratory failure, infections, and sepsis are potentially life-threatening and can result in an emergency department visit and/or hospitalization. Acute GPP episodes can be difficult to recognize and diagnose. The low incidence of the disease, its relapsing nature, the unpredictability of flare onset, and the lack of standardized diagnostic criteria are major obstacles to achieving rapid recognition and diagnosis in both the emergency department and the hospital setting.There is scarce evidence supporting the efficacy and safety of treatments commonly used for GPP; consequently, there is an unmet need for therapies that specifically target the condition. Our aim is to present a multidisciplinary approach to GPP to achieve a rapid diagnosis ensuring that the patient receives the most appropriate treatment for their pathology. The main recommendation for primary care and emergency physicians is to contact a dermatologist immediately for advice or to refer the patient when GPP or a flare is suspected.

Therapeutic Antibodies in Medicine

Antibody engineering has developed into a wide-reaching field, impacting a multitude of industries, most notably healthcare and diagnostics. The seminal work on developing the first monoclonal antibody four decades ago has witnessed exponential growth in the last 10-15 years, where regulators have approved monoclonal antibodies as therapeutics and for several diagnostic applications, including the remarkable attention it garnered during the pandemic. In recent years, antibodies have become the fastest-growing class of biological drugs approved for the treatment of a wide range of diseases, from cancer to autoimmune conditions. This review discusses the field of therapeutic antibodies as it stands today. It summarizes and outlines the clinical relevance and application of therapeutic antibodies in treating a landscape of diseases in different disciplines of medicine. It discusses the nomenclature, various approaches to antibody therapies, and the evolution of antibody therapeutics. It also discusses the risk profile and adverse immune reactions associated with the antibodies and sheds light on future applications and perspectives in antibody drug discovery.

Three cases of subcorneal pustular dermatosis with immunohistochemical examinations

Subcorneal pustular dermatosis, a rare, benign skin disease, is a type of neutrophilic dermatosis. The authors reported three cases of subcorneal pustular dermatosis. In case 1, a 9-year-old girl developed a skin rash with blisters following a mycoplasma infection and had a flare-up due to a common cold. She was successfully treated with a topical corticosteroid. In case 2, a 70-year-old woman who had been treated for rheumatoid arthritis with adalimumab, salazosulfapyridine, and leflunomide developed 3- to 5-mm pustules on her trunk and thighs 4 days after flu vaccination. The rash disappeared with drug withdrawal and treatment with diaminodiphenyl sulfone. In case 3, an 81-year-old man, who was diagnosed with pyoderma gangrenosum at 61 years old, developed multiple small flaccid pustules on his trunk and extremities due to an infection in the arteriovenous shunt area on the forearm. The pustule disappeared with intravenous antibiotic therapy; however, the pustules subsequently flared up along with ulcers typical of pyoderma gangrenosum. He was given oral prednisolone therapy, which was effective for the small pustules and some ulcers. Immunohistochemical examination of the three cases revealed neutrophilic infiltration in the subcorneal layer of the epidermis. The pustules contained neutrophils as well as some CD68+ and a few CD1a+ cells. The epidermis and dermis were more predominantly infiltrated by CD4+ cells than by CD8+ cells. Positive stainings for interleukin 8, interleukin 36γ, and phospho-extracellular signal-regulated kinases 1 and 2 were observed in the upper layers of the epidermis below the pustules. Although the pathogenesis of subcorneal pustular dermatosis has not been clarified, the current results suggest that a variety of inflammatory cells, including those responsible for both innate and acquired immunity, are involved in the accumulation of neutrophils in subcorneal pustular dermatosis.

Acrodermatitis continua of Hallopeau and generalised pustular psoriasis: Should they be the same or different entities?

Pustular psoriasis is characterised by eruptions of neutrophilic sterile pustules. The European Rare and Severe Psoriasis Expert Network consensus defines pustular psoriasis into three subtypes; generalised pustular psoriasis (GPP), palmoplantar pustulosis and acrodermatitis continua of Hallopeau (ACH). Mixed forms are categorised according to their predominant features. However, the Japanese Dermatological Association includes ACH under the diagnosis of GPP. This article aims to review the similarities and differences between ACH and GPP. Based on our review, interleukin (IL)-36RN mutations, the most frequent genetic findings in pustular psoriasis are found most commonly in GPP, followed by ACH. Genotypes of IL-36RN mutations among GPP patients and ACH patients are different between European and Asian ethnicities. IL-36 signalling pathway is the main mechanism. Metabolic diseases are common comorbidities and joint involvement can occur in 20.5%-36.4% of both conditions. Associated plaque psoriasis is more common in GPP than in ACH. Generally, ACH, even the generalised type, does not have systemic inflammation whereas GPP can occur with or without systemic inflammation. ACH can occur before, simultaneously, or after the development of GPP. However, response to treatment for GPP and ACH even in the same patients appear to be different. ACH seemed to be more recalcitrant to treatment than GPP but severe flare of GPP can lead to morbidity and mortality. Although GPP and ACH share genotypes and pathogenesis, we believe that ACH should be classified separately from GPP, and not under diagnosis of GPP. Future research is warranted to satisfactorily distinguish the two conditions.

Pathophysiology of generalized pustular psoriasis

Psoriasis is a chronic, immune-mediated skin disease that affects over 3% of adults in the United States. Psoriasis can present in several clinical forms. Of these, generalized pustular psoriasis is an acute, severe form, associated with increased morbidity and mortality. Unlike the more common plaque psoriasis, which is thought to feature dysregulation of the adaptive immune system, generalized pustular psoriasis reflects heightened autoinflammatory responses. Recent advances in genetic and immunological studies highlight a key role of the IL-36 immune axis in the pathogenesis of generalized pustular psoriasis. In this article, we review the psoriatic subtypes and discuss diagnostic criteria of generalized pustular psoriasis, discuss several newly identified genetic variants associated with pustular disease in the skin, and discuss how these mutations shed light on pustular disease mechanisms. Furthermore, we gather insights from recent transcriptomic studies that similarly implicate a pathogenic role of the IL-36 immune axis in generalized pustular psoriasis.

Rapid and sustained improvements in Generalized Pustular Psoriasis Physician Global Assessment scores with spesolimab for treatment of generalized pustular psoriasis flares in the randomized, placebo-controlled Effisayil 1 study

BACKGROUND

Effisayil 1 was a randomized, placebo-controlled study of spesolimab, which is an anti-IL-36 receptor antibody, in patients presenting with a generalized pustular psoriasis flare.

OBJECTIVE

To assess the effects of spesolimab over the 12-week study.

METHODS

The primary endpoint of the study was Generalized Pustular Psoriasis Physician Global Assessment (GPPGA) pustulation subscore of 0 at week 1. Patients (N = 53) were randomized (2:1) to receive a single intravenous dose of 900 mg spesolimab or placebo on day 1. Patients could receive open-label spesolimab for persistent flare symptoms on day 8.

RESULTS

Most patients receiving spesolimab achieved a GPPGA pustulation subscore of 0 (60.0%) and GPPGA total score of 0 or 1 (60.0%) by week 12. In patients randomized to placebo who received open-label spesolimab on day 8, the proportion with GPPGA pustulation subscore of 0 increased from 5.6% at day 8 to 83.3% at week 2. No factors predictive of spesolimab response were identified in patient demographics or clinical characteristics.

LIMITATIONS

The effect of initial randomization was not determined conventionally beyond week 1 due to patients receiving open-label spesolimab.

CONCLUSION

Rapid control of generalized pustular psoriasis flare symptoms with spesolimab was sustained over 12 weeks, further supporting its potential use as a therapeutic option for patients.

Use of Biological Therapies for the Management of Pustular Psoriasis: A New Era?

Generalized pustular psoriasis (GPP) is a severe and rare form of psoriasis, being a potentially life-threatening condition, characterized by recurring episodes or flares of widespread cutaneous erythema with macroscopic sterile pustules. An irregular innate immune response is linked to GPP, which is considered an auto-inflammatory disorder, while innate and adaptive immunopathogenic responses are involved in psoriasis pathogenesis. In consequence, different cytokine cascades have been suggested to be mainly involved in the pathogenesis of each different psoriasis form, with the interleukin (IL)23/IL17 axis implied in plaque psoriasis, and the IL36 pathway in the GPP. As regards GPP treatment, conventional systemic drugs available for plaque psoriasis are usually used as the first-line treatment option. However, contraindications and adverse events often limit the use of these therapies. In this scenario, biologic drugs may represent a promising treatment option. To date, even if 12 different biologics have been approved for plaque psoriasis, none of these is approved for GPP where they are employed off-label. Recently, spesolimab, an anti-IL36 receptor monoclonal antibody, has been recently approved for GPP. The purpose of this article is to assess the current literature about the use of biological therapies for the treatment of GPP to establish the basis for a shared GPP management algorithm.

Genetics of Generalized Pustular Psoriasis: Current Understanding and Implications for Future Therapeutics

Psoriasis is a chronic inflammatory skin disease characterized by the appearance of clearly demarcated erythematous and scaly plaques. It can be divided into various types, including plaque, nail, guttate, inverse, and pustular psoriasis. Plaque psoriasis is the most commonly occurring type, though there is another rare but severe pustular autoinflammatory skin disease called generalized pustular psoriasis (GPP), which manifests with acute episodes of pustulation and systemic symptoms. Though the etiopathogenesis of psoriasis is not yet fully understood, a growing body of literature has demonstrated that both genetic and environmental factors play a role. The discovery of genetic mutations associated with GPP has shed light on our comprehension of the mechanisms of the disease, promoting the development of targeted therapies. This review will summarize genetic determinants as known and provide an update on the current and potential treatments for GPP. The pathogenesis and clinical presentation of the disease are also included for a comprehensive discussion.

Acrodermatitis continua of Hallopeau successfully treated with bimekizumab: A case report

Acrodermatitis continua of Hallopeau is a rare variant of localized pustular psoriasis characterized by the recurrent eruption of sterile pustules involving the distal portions of the fingers and toes that can lead to the destruction of the nail apparatus. Acrodermatitis continua of Hallopeau is a chronic, relapsing condition that is resistant to most topical and systemic psoriasis therapies, making it notoriously difficult to manage. Interleukin-36 and interleukin-17 are thought to play a pivotal role in the pathophysiology of pustular psoriasis, and evidence suggests that interleukin-17 inhibition can be an effective therapy for pustular psoriasis variants, including acrodermatitis continua of Hallopeau. Bimekizumab, a monoclonal antibody that inhibits the interleukin-17 pathway, may be a safe and effective treatment option for patients with acrodermatitis continua of Hallopeau. We present the first documented case of a patient with acrodermatitis continua of Hallopeau of the bilateral thumbnails who experienced an excellent response to bimekizumab treatment.

Targeting IL-36 in Inflammatory Skin Diseases

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily of cytokines. IL-36 cytokines are composed of three agonists (IL-36α, IL-36β, and IL-36γ) and two antagonists (IL-36 receptor antagonist [IL36Ra] and IL-38). These work in innate and acquired immunity and are known to contribute to host defense and to the pathogenesis of autoinflammatory diseases, autoimmune diseases, and infectious diseases. In the skin, IL-36α and IL-36γ are mainly expressed by keratinocytes in the epidermis, although they are also produced by dendritic cells, macrophages, endothelial cells, and dermal fibroblasts. IL-36 cytokines participate in the first-line defense of the skin against various exogenous assaults. IL-36 cytokines play significant roles in the host defense system and in the regulation of inflammatory pathways in the skin, collaborating with other cytokines/chemokines and immune-related molecules. Thus, numerous studies have shown IL-36 cytokines to play important roles in the pathogenesis of various skin diseases. In this context, the clinical efficacy and safety profiles of anti-IL-36 agents such as spesolimab and imsidolimab have been evaluated in patients with generalized pustular psoriasis, palmoplantar pustulosis, hidradenitis suppurativa, acne/acneiform eruptions, ichthyoses, and atopic dermatitis. This article comprehensively summarizes the roles played by IL-36 cytokines in the pathogenesis and pathophysiology of various skin diseases and summarizes the current state of research on therapeutic agents that target IL-36 cytokine pathways.

Generalized Pustular Psoriasis: A Review on Clinical Characteristics, Diagnosis, and Treatment

Generalized pustular psoriasis (GPP) is a rare, chronic, and severe inflammatory skin disorder characterized by sudden eruption of sterile pustules, often accompanied by systemic inflammation. GPP flares can be life-threatening if untreated, owing to potential serious complications such as sepsis and cardiovascular failure. Diagnosis and clinical measurement of disease severity in GPP are often difficult. Lack of standardized criteria in the international guidelines and the heterogeneity of cutaneous and extracutaneous symptoms make the diagnosis of GPP difficult. Clinical criteria for description and diagnosis of pustular conditions, including GPP, are variable and there is no specific agreement on commonly sustained concepts. Differentiation of GPP from other similar conditions/diseases is important and requires careful assessments. The evidence that supports current topical or systemic therapies is largely based on case reports and small studies. Some biologic agents that target key cytokines involved in the activation of inflammatory pathways have been used as treatments for GPP. Recently, spesolimab, an IL-36R antagonist, has been approved in the USA and Japan for the treatment of GPP flares in adults, but there are no currently approved treatments for GPP in Europe. The IL-36 pathway has recently emerged as a central axis driving the pathogenic inflammatory mechanisms of GPP. Biologic agents that inhibit the IL-36 pathway have shown efficacy and safety in patients with GPP, addressing a generally considered unmet medical need.

IL-4/IL-13 Inhibitors for Atopic Dermatitis Induce Psoriatic Rash Transcriptionally Close to Pustular Psoriasis

Dupilumab is a therapeutic antibody targeting IL-4 and IL-13 receptor subunit alpha used for the treatment of patients with atopic dermatitis (AD). Cases of psoriasis-like reactions induced under dupilumab treatment (dupilumab-induced psoriatic eruption [DI-Pso]) for AD were recently reported. To understand the pathogenesis of DI-Pso, we performed gene expression profiling studies on skin biopsies of DI-Pso (n = 7) compared with those of plaque psoriasis, AD, and healthy controls (n = 4 each). Differential gene expression was performed using enrichment and Gene Ontology analysis. Gene expression was validated by qPCR, and protein levels were assessed by immunohistochemistry. Transcriptomic and protein analysis of DI-Pso compared with that of healthy controls, plaque psoriasis, and AD skins revealed activation of T helper 17/IL-23 pathways associated with a significant expression of IL-36, surrogate marker of pustular psoriasis. By contrast, T helper 2 representative genes' expression was strongly decreased in DI-Pso across comparison. Matching analysis with public data of pustular psoriasis skin corroborated that DI-Pso and pustular psoriasis upstream regulators overlap, greater than the overlap with plaque psoriasis. Furthermore, DI-Pso showed strongly decreased expression of many barrier skin genes compared with healthy controls, plaque psoriasis, and AD. Our data indicate that the pathogenesis of DI-Pso relied on a shift of skin immune responses from a T helper 2 to an IL-36 and T helper 17 polarization and on intensified skin barrier alterations.

Comparison of the Inflammatory Circuits in Psoriasis Vulgaris, Non‒Pustular Palmoplantar Psoriasis, and Palmoplantar Pustular Psoriasis

Palmoplantar pustular psoriasis (PPPP) and non‒pustular palmoplantar psoriasis (NPPP) are localized, debilitating forms of psoriasis. The inflammatory circuits involved in PPPP and NPPP are not well-understood. To compare the cellular and immunological features that differentiate PPPP and NPPP, skin biopsies were collected from a total of 30 participants with PPPP, NPPP, and psoriasis vulgaris (PV) and from 10 healthy participants. A subset consented to a second biopsy after 3 additional weeks off medication. Histologic staining of lesional and nonlesional skin showed higher neutrophil counts in PPPP than in NPPP and PV and higher CD8⁺ T-cell counts in NPPP. RNA sequencing and transcriptional analysis of skin biopsies showed enhanced IFN-γ pathway activation in NPPP lesions but stronger signatures of IL-17 pathway and neutrophil-related genes (e.g., IL36A) in PPPP lesional skin. Serum analysis on the Olink platform detected higher concentrations of T helper type 1, IFN-γ‒inducible chemokines in NPPP, and higher neutrophil-associated cytokines in PPPP. Taken together, this evidence suggests more pronounced T helper 1‒mediated inflammation in NPPP than in PV and PPPP and stronger neutrophil-associated activity in PPPP than in NPPP and PV. These data support targeting inflammatory pathways associated with neutrophilic inflammation (e.g., IL-36 signaling) for therapeutic development in PPPP.

Spesolimab: First Approval

Spesolimab (spesolimab-sbzo; SPEVIGO^®) is an interleukin (IL)-36 receptor antagonist being developed by Boehringer Ingelheim for the treatment of various immune-mediated disorders. In September 2022, spesolimab was approved in the USA for the treatment of generalized pustular psoriasis (GPP) flares in adults. This article summarizes the milestones in the development of spesolimab leading to this first approval for GPP flares.

Generalized pustular psoriasis is a disease distinct from psoriasis vulgaris: evidence and expert opinion

INTRODUCTION

Generalized pustular psoriasis (GPP) is a rare, severe, clinically heterogeneous disease characterized by flares of widespread, non-infectious, macroscopically visible pustules that occur with or without systemic inflammation, and are associated with significant morbidity and mortality. Historically, GPP has been classified as a variant of psoriasis vulgaris (PV, or plaque psoriasis); however, accumulating evidence indicates that these are distinct conditions, requiring different treatment approaches.

AREAS COVERED

In this perspectives article we review evidence that supports the classification of GPP as distinct from PV.

EXPERT OPINION

The histopathologic and clinical appearance of GPP is distinct from that of PV and fundamental differences exist between the two conditions in terms of genetic causes and expression-related mechanisms of disease development. GPP results from dysregulation of the innate immune system, with disruption of the interleukin (IL)-36 inflammatory pathway, induction of inflammatory keratinocyte responses, and recruitment of neutrophils. PV is driven by the adaptive immune system, with a key role played by IL-17. Considering GPP as a separate disease will enable greater focus on its specific pathogenesis and the needs of patients. Many treatments for PV have insufficient efficacy in GPP and a therapeutic approach developed specifically for GPP might lead to better patient outcomes.

Clinical Characteristics of Patients with Pustular Psoriasis: A Single-Center Retrospective Observational Study

Clinical and epidemiologic data on pustular psoriasis are scarce. To investigate the phenotypes of pustular psoriasis and the patients’ characteristics observed in a real-life retrospective observational study. The number of incident cases of pustular psoriasis registered in the period 2005–2021 was retrieved from the electronic medical records of the University Hospital of Verona. One hundred and forty cases of pustular psoriasis were collected. Ninety-one out of 140 patients (65%) were females, with a median (IQR) age of 57 (43–66) years. According to the ERASPEN classification criteria, 116 patients (83%) had palmoplantar pustulosis (PPP), 13 (9%) generalized pustular psoriasis (GPP), and 11 (8%) acrodermatitis continua of Hallopeau (ACH). Gender distribution and median age were consistent among the three groups. The prevalence of psoriatic arthritis in GPP, ACH, and PPP was 8%, 36%, and 28%, respectively. During the same period, a total of 4718 cases of plaque psoriasis were retrieved, with a 1:34 ratio of pustular over plaque psoriasis. Pustular psoriasis is much rarer than plaque psoriasis, with PPP being the more common subtype.

IL-36 Cytokines: Their Roles in Asthma and Potential as a Therapeutic

Interleukin (IL)-36 cytokines are members of the IL-1 superfamily, which consists of three agonists (IL-36α, IL-36β and IL-36γ) and an IL-36 receptor antagonist (IL-36Ra). IL-36 cytokines are crucial for immune and inflammatory responses. Abnormal levels of IL-36 cytokine expression are involved in the pathogenesis of inflammation, autoimmunity, allergy and cancer. The present study provides a summary of recent reports on IL-36 cytokines that participate in the pathogenesis of inflammatory diseases, and the potential mechanisms underlying their roles in asthma. Abnormal levels of IL-36 cytokines are associated with the pathogenesis of different types of asthma through the regulation of the functions of different types of cells. Considering the important role of IL-36 cytokines in asthma, these may become a potential therapeutic target for asthma treatment. However, existing evidence is insufficient to fully elucidate the specific mechanism underlying the action of IL-36 cytokines during the pathological process of asthma. The possible mechanisms and functions of IL-36 cytokines in different types of asthma require further studies.

Generalized pustular psoriasis: the new era of treatment with IL-36 receptor inhibitors

Generalized pustular psoriasis (GPP) is a rare yet severe variant of psoriasis, characterized by the eruption of superficial sterile pustules that appear suddenly and widely distributed, potentially life-threatening. It more commonly presents through recurrent acute flares triggered by stress, corticosteroid withdrawals, pregnancy, or infections. The pathogenesis of this disease is yet to be fully understood. Nevertheless, studies have suggested an important role of an IL-1 subfamily of cytokines, due to an imbalance of the IL-36 axis favoring of pro-inflammatory activity. The therapeutic intervention for this condition is still a challenge as its rarity and scarce available information contribute to the absence of specific treatment. Current options stand on small, open-label trials or follows standard treatment for plaque psoriasis. Spesolimab and imsidolimab are two IL-36 receptor inhibitors which completed phase 1 and 2 trials with a good efficacy and safety profile in the treatment of this disease, including in the fast control of its acute flares. The most common adverse events reported with spesolimab were mild to moderate infections, and imsidolimab was well tolerated. GPP clinical trials remain to have their small sample size as a major limitation, but IL-36 receptor inhibitors are promising therapeutic options currently under investigation.

The role of IL-36 subfamily in intestinal disease

Interleukin (IL)-36 is a subfamily, of the IL-1 super-family and includes IL-36α, IL-36β, IL-36γ, IL-38 and IL-36Ra. IL-36 cytokines are involved in the pathology of multiple tissues, including skin, lung, oral cavity, intestine, kidneys and joints. Recent studies suggest that IL-36 signaling regulates autoimmune disease in addition to antibacterial and antiviral responses. Most research has focused on IL-36 in skin diseases such as psoriasis, however, studies on intestinal diseases are also underway. This review outlines what is known about the bioactivity of the IL-36 subfamily and its role in the pathogenesis of intestinal diseases such as inflammatory bowel disease, colorectal cancer, gut dysbacteriosis and infection, and proposes that IL-36 may be a target for novel therapeutic strategies to prevent or treat intestinal diseases.

Assessment of the Pharmacokinetics and Safety of Spesolimab, a Humanised Anti-interleukin-36 Receptor Monoclonal Antibody, in Healthy Non-Japanese and Japanese Subjects: Results from Phase I Clinical Studies

BACKGROUND AND OBJECTIVE

The interleukin-36 signalling pathway is associated with pathogenesis of a number of inflammatory diseases. Spesolimab is a selective, humanised, IgG1 antibody that targets the interleukin-36 receptor. We aimed to evaluate the pharmacokinetics, safety and tolerability of single and multiple doses of spesolimab in healthy non-Japanese and Japanese subjects.

METHODS

Five phase I clinical studies (three placebo-controlled dose-escalation, two open-label) were conducted in healthy volunteers; single or multiple doses of spesolimab were administered by intravenous infusion or subcutaneous injection. Plasma samples were collected to investigate the pharmacokinetics of spesolimab and evaluate changes with respect to dose, frequency of dosing, formulation and injection site. Immunogenicity, safety and tolerability were also assessed.

RESULTS

Intravenous spesolimab exhibited target-mediated drug disposition at low doses (0.01-0.3 mg/kg) and linear kinetics at doses ≥ 0.3 mg/kg. Steady state was not attained after the fourth weekly dose because of the long half-life (3-5 weeks). Bioavailability of subcutaneous spesolimab increased with increasing dose over the range of 150-600 mg and was higher when administered to the thigh than to the abdomen. The pharmacokinetic profile was consistent between Japanese and non-Japanese subjects. Positive anti-drug antibody responses occurred during the terminal phase of the spesolimab concentration-time profile in 26.7-33.3% and 16.7-37.5% of subjects receiving intravenous and subcutaneous spesolimab, respectively. The impact of anti-drug antibodies on spesolimab pharmacokinetics was low in healthy volunteers, with the impact on spesolimab plasma concentrations only observed in a few subjects at higher titres (≥ 11,400). No serious adverse events were reported; intravenous doses up to 1200 mg were well tolerated in healthy volunteers.

CONCLUSIONS

The pharmacokinetic profile and safety data obtained from these phase I clinical studies have been used to guide spesolimab dosing in clinical studies of patients with interleukin-36-mediated diseases.

CLINICAL TRIAL REGISTRATION

For Studies 1-5, NCT02525679, NCT02852824, NCT03100903, NCT03123094, NCT03617835.