Proof-of-concept clinical trial of etokimab shows a key role for IL-33 in atopic dermatitis pathogenesis

Pharmacokinetics and pharmacodynamics of itepekimab in adults with moderate-to-severe atopic dermatitis: Results from two terminated phase II trials

Interleukin-33 (IL-33) is a proinflammatory alarmin cytokine released by damaged epithelial tissue cells that initiates and amplifies both type 1 and type 2 inflammatory cascades. A role for IL-33 in atopic dermatitis (AD; a chronic, relapsing type 2 inflammatory disease of the skin) has been proposed. Itepekimab is a novel human IgG4P monoclonal antibody against IL-33, currently in clinical development for chronic obstructive pulmonary disease (COPD). Two global phase II studies-a dose-ranging itepekimab monotherapy study (NCT03738423) and a proof-of-concept study of itepekimab alone and in combination with dupilumab (NCT03736967)-were conducted in patients with moderate-to-severe AD to assess safety, tolerability, pharmacokinetics, pharmacodynamics, and efficacy; both studies were terminated following an interim analysis of the proof-of-concept study, which failed to demonstrate the efficacy of itepekimab. In these two studies, itepekimab exhibited linear and dose-proportional pharmacokinetics. Pharmacodynamics of total IL-33 indicated that itepekimab saturated binding to the target in serum at 300 mg q2w and q4w doses, and decreased blood eosinophil counts. Concentration-time profiles of itepekimab and total IL-33 were similar for itepekimab with or without dupilumab, and between East Asian and non-East Asian subgroups. Itepekimab was generally well tolerated, both alone and in combination with dupilumab. The lack of clinical efficacy for itepekimab observed in these studies suggests that IL-33 may not be a key pathogenic driver in moderate-to-severe AD.

Targeted therapy for immune mediated skin diseases. What should a dermatologist know?

BACKGROUND

Molecularly targeted therapies, such as monoclonal antibodies (mAbs) and Janus Kinase inhibitors (JAKis), have emerged as essential tools in the treatment of dermatological diseases. These therapies modulate the immune system through specific signaling pathways, providing effective alternatives to traditional systemic immunosuppressive agents. This review aims to provide an updated summary of targeted immune therapies for inflammatory skin diseases, considering their pathophysiology, efficacy, dosage, and safety profiles.

METHODS

The review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines. A systematic search was conducted on PubMed over the past 10 years, focusing on randomized clinical trials, case reports, and case series related to targeted immune therapies in dermatology. Eligibility criteria were applied, and data were extracted from each study, including citation data, study design, and results.

RESULTS

We identified 1360 non-duplicate articles with the initial search strategy. Title and abstract review excluded 1150, while a full-text review excluded an additional 50 articles. The review included 143 studies published between 2012 and 2022, highlighting 39 drugs currently under investigation or in use for managing inflammatory skin diseases.

STUDY LIMITATIONS

The heterogeneity of summarized information limits this review. Some recommendations originated from data from clinical trials, while others relied on retrospective analyses and small case series. Recommendations will likely be updated as new results emerge.

CONCLUSION

Targeted therapies have revolutionized the treatment of chronic skin diseases, offering new options for patients unresponsive to standard treatments. Paradoxical reactions are rarely observed. Further studies are needed to fully understand the mechanisms and nature of these therapies. Overall, targeted immune therapies in dermatology represent a promising development, significantly improving the quality of life for patients with chronic inflammatory skin diseases.

The involvement of keratinocytes in pruritus of chronic inflammatory dermatosis

Frequent itching and incessant scratching are commonly observed in various chronic inflammatory skin conditions, including atopic dermatitis and psoriasis. The persistent and prolonged nature of pruritus can worsen one's quality of life. Keratinocytes (KCs), the predominant cells of the epidermis, have been confirmed to interact with sensory neurons and immune cells and be involved in chronic skin inflammatory diseases associated with pruritus. Initially, KCs and sensory neurons form a unique synapse-like connection within the epidermis, serving as the structural foundation for their interaction. Additionally, several receptors, including toll-like receptors and protease-activated receptor 2, expressed on KCs, become activated in an inflammatory milieu. On the one hand, activated KCs are sources of pro-inflammatory cytokines and neurotrophic factors, such as adenosine triphosphate, thymic stromal lymphopoietin, and nerve growth factor, which directly or indirectly participate in stimulating sensory neurons, thereby contributing to the itch sensations. On the other hand, KCs also function as primary transducers alongside intraepidermal nerve endings, directly initiating pruritic responses. This review summarizes the current literature and highlights the critical role of KCs in the development and persistence of chronic itch in inflammatory skin disorders.

Biologic and small-molecule therapy for treating moderate to severe atopic dermatitis: Mechanistic considerations

Atopic dermatitis (AD) is a complex and heterogeneous skin disease for which achieving complete clinical clearance for most patients has proven challenging through single cytokine inhibition. Current studies integrate biomarkers and evaluate their role in AD, aiming to advance our understanding of the diverse molecular profiles implicated. Although traditionally characterized as a TH2-driven disease, extensive research has recently revealed the involvement of TH1, TH17, and TH22 immune pathways as well as the interplay of pivotal immune molecules, such as OX40, OX40 ligand (OX40L), thymic stromal lymphopoietin, and IL-33. This review explores the mechanistic effects of treatments for AD, focusing on mAbs and Janus kinase inhibitors. It describes how these treatments modulate immune pathways and examines their impact on key inflammatory and barrier biomarkers.

Biologic Therapy in Pediatric Chronic Rhinosinusitis: A Systematic Review

OBJECTIVE

Provide clinicians with current evidence for biologic therapy in children with chronic rhinosinusitis with nasal polyposis (CRSwNP).

DATA SOURCES

PubMed, MEDLINE, Cochrane, and clinical trial registries.

REVIEW METHODS

Key search terms related to biologic therapy in pediatric CRSwNP were identified via a structured query of current medical literature and clinical trial databases.

CONCLUSIONS

There is a dearth of active clinical trials and research studies for biologics targeting pediatric CRSwNP. There is an ongoing compassionate-use clinical trial involving Dupilumab for children with nasal polyps as well as only 1 published work specifically focused on Dupilumab for pediatric CRSwNP in the setting of aspirin-exacerbated respiratory disease.

IMPLICATIONS FOR PRACTICE

For children with atopic dermatitis, asthma, and chronic idiopathic urticaria, biologic therapies such as Omalizumab, Dupilumab, and Mepolizumab have gained Food and Drug Administration approval. The role of biologic therapy in pediatric CRSwNP demonstrates significant promise in the comprehensive management of the unified airway. Additional Phase III trials are necessary to broaden clinical indications for children with comorbid conditions and complex sinonasal disease.

Antibody-based therapeutics for chronic rhinosinusitis with nasal polyps

INTRODUCTION

Chronic rhinosinusitis with nasal polyps (CRSwNP) is a prevalent inflammatory condition with heterogenous underlying endotypes, the most common being type 2 mediated inflammation. Several biologics have been developed to target specific pro-inflammatory cytokines and their receptors with proven efficacy in both quantitative and qualitative outcomes in patients with severe uncontrolled disease. However, there is an ongoing debate on the role of biologics relative to conventional therapies for CRSwNP and their efficacy in patient subgroups with non-polyp type 2 disease.

AREAS COVERED

This review examines the evidence on the efficacy and safety of biologics in CRSwNP, recommendations for their use, and discusses the broader economic factors influencing their application in clinical practice.

EXPERT OPINION

Emerging real-life data demonstrating the variable efficacy of the available biologics for patients with CRSwNP, coupled with the high cost compared to conventional therapies such as surgery, renders biologics to be considered as an add-on therapy in the majority of cases. However, ongoing research into increasing biologic dose intervals and novel therapies targeting alternative pathways may offer a more cost-effective and sustainable option in future.

Interleukin antagonists for atopic dermatitis: a new era of therapy

INTRODUCTION

Over the last decade, increasing understanding of the immunopathogenesis of atopic dermatitis (AD) enabled the recognition of multiple therapeutic targets and subsequently the development of novel, highly effective systemic treatments, including interleukin (IL)-antagonists. To date, the IL-4Ra-inhibitor dupilumab and the IL-13 inhibitor tralokinumab have gained regulatory approval in Europe for the treatment of moderate-to-severe AD, while more than 70 new therapeutics are currently in development.

AREAS COVERED

In this review, we address the role of ILs in the pathogenesis of AD and provide an overview of the novel and investigational IL-antagonists, as regards their efficacy and safety on moderate-to-severe AD.

EXPERT OPINION

Current data have established IL-4 and IL-13 inhibitors as effective and safe for the treatment of moderate-to-severe AD, as regards the rapid control of flares as well as the long-term remission of the disease. Data regarding the efficacy and safety of other IL-inhibitors, including those targeting IL-31, IL-22, IL-33, IL-36 and IL-18, are accumulating. There is still an unmet need for real-world-evidence studies and head-to-head studies for both currently available and future agents in AD treatment. Establishing predictive biomarkers of treatment response in a disorder of such considerable heterogenicity might help physicians pursue a patient-tailored therapeutic response.

(S)-(-)-blebbistatin O-benzoate has the potential to improve atopic dermatitis symptoms in NC/Nga mice by upregulating epidermal barrier function and inhibiting type 2 alarmin cytokine induction

Atopic dermatitis is a multi-pathogenic disease characterized by chronic skin inflammation and barrier dysfunction. Therefore, improving the skin's ability to form an epidermal barrier and suppressing the production of cytokines that induce type 2 inflammatory responses are important for controlling atopic dermatitis symptoms. (-)-Blebbistatin, a non-muscle myosin II inhibitor, has been suggested to improve pulmonary endothelial barrier function and control inflammation by suppressing immune cell migration; however, its efficacy in atopic dermatitis is unknown. In this study, we investigated whether (S)-(-)-blebbistatin O-benzoate, a derivative of (-)-blebbistatin, improves dermatitis symptoms in a mite antigen-induced atopic dermatitis model using NC/Nga mice. The efficacy of the compound was confirmed using dermatitis scores, ear thickness measurements, serum IgE levels, histological analysis of lesions, and filaggrin expression analysis, which is important for barrier function. (S)-(-)-Blebbistatin O-benzoate treatment significantly reduced the dermatitis score and serum IgE levels compared to those in the vehicle group (p < 0.05). Furthermore, the histological analysis revealed enhanced filaggrin production and a decreased number of mast cells (p < 0.05), indicating that (S)-(-)-blebbistatin O-benzoate improved atopic dermatitis symptoms in a pathological model. In vitro analysis using cultured keratinocytes revealed increased expression of filaggrin, loricrin, involucrin, and ceramide production pathway-related genes, suggesting that (S)-(-)-blebbistatin O-benzoate promotes epidermal barrier formation. Furthermore, the effect of (S)-(-)-blebbistatin O-benzoate on type 2 alarmin cytokines, which are secreted from epidermal cells upon scratching or allergen stimulation and are involved in the pathogenesis of atopic dermatitis, was evaluated using antigens derived from mite feces. The results showed that (S)-(-)-blebbistatin O-benzoate inhibited the upregulation of these cytokines. Based on the above, (S)-(-)-blebbistatin O-benzoate has the potential to be developed as an atopic dermatitis treatment option that controls dermatitis symptoms by suppressing inflammation and improving barrier function by acting on multiple aspects of the pathogenesis of atopic dermatitis.

Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics of PF-06817024 in Healthy Participants, Participants with Chronic Rhinosinusitis with Nasal Polyps, and Participants with Atopic Dermatitis: A Phase 1, Randomized, Double-Blind, Placebo-Controlled Study

PF-06817024 is a high affinity, humanized antibody that binds interleukin-33, a proinflammatory type 2 cytokine, and thereby has the potential to inhibit downstream type 2 inflammation. This Phase 1, randomized, placebo-controlled study was conducted in 3 parts to evaluate the safety, tolerability, pharmacokinetics (PK), immunogenicity, and pharmacodynamics of escalating single and limited repeat PF-06817024 doses in healthy participants (Part 1), a single dose of PF-06817024 in participants with chronic rhinosinusitis with nasal polyps (Part 2), and repeat doses of PF-06817024 in participants with moderate to severe atopic dermatitis (atoptic dermatitis; Part 3). PF-06817024 was generally well tolerated in all participant populations. Most participants experienced a treatment-emergent adverse event (healthy participants, 78.4% and 100%; participants with chronic rhinosinusitis with nasal polyps, 90.9% and 88.9%; and participants with atoptic dermatitis, 60.0% and 62.5% in the PF-06817024 and placebo groups, respectively). No substantial deviations from dose proportionality were observed for single intravenous doses of 10-1000 mg, indicating linear PK in healthy participants. Mean terminal half-life ranged from 83 to 94 days after single intravenous administration in healthy participants and was similar to that observed after administration in the studied patient populations. Incidences of antidrug antibodies in the studied populations were 10.8%, 9.1%, and 5.0% for healthy participants, participants with chronic rhinosinusitis with nasal polyps, and participants with atoptic dermatitis, respectively. In addition, dose-dependent increases were observed in total serum interleukin-33 levels of treated participants, indicating target engagement. Overall, the PK and safety profile of PF-06817024 supports further investigation of the drug as a potential treatment for allergic diseases.

Emerging drugs for the treatment of atopic dermatitis: a focus on phase 2 and phase 3 trials

INTRODUCTION

Atopic dermatitis (AD) is an inflammatory skin condition that affects millions of pediatric and adult patients with well-studied impact on morbidity and quality of life. Management occurs in a stepwise fashion beginning with preventative measures before immunomodulators are introduced. However, challenges remain in treatment of moderate-to-severe atopic dermatitis that is refractory to first- and second-line treatments and there are only few topical anti-inflammatory options, especially for pediatric patients.

AREAS COVERED

New medications are required to address these gaps as lesions may persist despite treatment or patients may discontinue treatment due to actual or anticipated adverse effects of mainstay medications. Emerging research into the pathophysiology of AD and the immune system at large has provided opportunities for novel interventions aimed at stopping AD mechanisms at new checkpoints. Clinical trials for 36 agents currently in phase 2 or phase 3 are evaluated with particular focus on the studies for, B244, CBP-201, tapinarof, lebrikizumab, nemolizumab, amlitelimab, and rocatinlimab as they explore novel pathways and have some of the most promising results.

EXPERT OPINION

These clinical trials contribute to the evolution of AD treatment toward greater precision based on salient pathways with a particular focus on moderate-to-severe AD to enhance efficacy and minimize adverse effects.

ILC2s: Unraveling the innate immune orchestrators in allergic inflammation

The prevalence rate of allergic diseases including asthma, atopic rhinitis (AR) and atopic dermatitis (AD) has been significantly increasing in recent decades due to environmental changes and social developments. With the study of innate lymphoid cells, the crucial role played by type 2 innate lymphoid cells (ILC2s) have been progressively unveiled in allergic diseases. ILC2s, which are a subset of innate lymphocytes initiate allergic responses. They respond swiftly during the onset of allergic reactions and produce type 2 cytokines, working in conjunction with T helper type 2 (Th2) cells to induce and sustain type 2 immune responses. The role of ILC2s represents an intriguing frontier in immunology; however, the intricate immune mechanisms of ILC2s in allergic responses remain relatively poorly understood. To gain a comphrehensive understanding of the research progress of ILC2, we summarize recent advances in ILC2s biology in pathologic allergic inflammation to inspire novel approaches for managing allergic diseases.

Potential Aspects of the Use of Cytokines in Atopic Dermatitis

Atopic dermatitis (AD) is an abnormal inflammatory response in the skin to food, environmental IgE, or non-IgE allergens. This disease belongs to a group of inflammatory diseases that affect both children and adults. In highly developed countries, AD is diagnosed twice as often in children than in adults, which may possibly be connected to increased urbanization. The immune system's pathomechanisms of AD involve humoral mechanisms with IgE, cellular T lymphocytes, dendritic cells occurring in the dermis, Langerhans cells occurring in the epidermis, and other cells infiltrating the site of inflammation (eosinophils, macrophages, mast cells, neutrophils, and basophils). Cytokines are small proteins that affect the interaction and communication between cells. This review characterizes cytokines and potential aspects of the treatment of atopic dermatitis, as well as new strategies that are currently being developed, including targeting cytokines and their receptors.

IL-33 Induces Cellular and Exosomal miR-146a Expression as a Feedback Inhibitor of Mast Cell Function

IL-33 is an inflammatory cytokine that promotes allergic disease by activating group 2 innate lymphoid cells, Th2 cells, and mast cells. IL-33 is increased in asthmatics, and its blockade suppresses asthma-like inflammation in mouse models. Homeostatic control of IL-33 signaling is poorly understood. Because the IL-33 receptor, ST2, acts via cascades used by the TLR family, similar feedback mechanisms may exist. MicroRNA (miR)-146a is induced by LPS-mediated TLR4 signaling and serves as a feedback inhibitor. Therefore, we explored whether miR-146a has a role in IL-33 signaling. IL-33 induced cellular and exosomal miR-146a expression in mouse bone marrow-derived mast cells (BMMCs). BMMCs transfected with a miR-146a antagonist or derived from miR-146a knockout mice showed enhanced cytokine expression in response to IL-33, suggesting that miR-146a is a negative regulator of IL-33-ST2 signaling. In vivo, miR-146a expression in plasma exosomes was elevated after i.p. injection of IL-33 in wild-type but not mast cell-deficient KitW-sh/W-sh mice. Finally, KitW-sh/W-sh mice acutely reconstituted with miR-146a knockout BMMCs prior to IL-33 challenge had elevated plasma IL-6 levels compared with littermates receiving wild-type BMMCs. These results support the hypothesis that miR-146a is a feedback regulator of IL-33-mediated mast cell functions associated with allergic disease.

Interplay of cytokines in the pathophysiology of atopic dermatitis: insights from Murin models and human

The pathogenesis of atopic dermatitis (AD) is understood to be crucially influenced by three main factors: dysregulation of the immune response, barrier dysfunction, and pruritus. In the lesional skin of AD, various innate immune cells, including Th2 cells, type 2 innate lymphoid cells (ILC2s), and basophils, produce Th2 cytokines [interleukin (IL)-4, IL-5, IL-13, IL-31]. Alarmins such as TSLP, IL-25, and IL-33 are also produced by epidermal keratinocytes, amplifying type 2 inflammation. In the chronic phase, not only Th2 cells but also Th22 and Th17 cells increase in number, leading to suppression of filaggrin expression by IL-4, IL-13, and IL-22, which further deteriorates the epidermal barrier function. Dupilumab, which targets IL-4 and IL-13, has shown efficacy in treating moderate to severe AD. Nemolizumab, targeting IL-31RA, effectively reduces pruritus in AD patients. In addition, clinical trials with fezakinumab, targeting IL-22, have demonstrated promising results, particularly in severe AD cases. Conversely, in murine models of AD, several cytokines, initially regarded as promising therapeutic targets, have not demonstrated sufficient efficacy in clinical trials. IL-33 has been identified as a potent activator of immune cells, exacerbating AD in murine models and correlating with disease severity in human patients. However, treatments targeting IL-33 have not shown sufficient efficacy in clinical trials. Similarly, thymic stromal lymphopoietin (TSLP), integral to type 2 immune responses, induces dermatitis in animal models and is elevated in human AD, yet clinical treatments like tezepelumab exhibit limited efficacy. Therapies targeting IL-1α, IL-5, and IL-17 also failed to achieve sufficient efficacy in clinical trials. It has become clear that for treating AD, IL-4, IL-13, and IL-31 are relevant therapeutic targets during the acute phase, while IL-22 emerges as a target in more severe cases. This delineation underscores the necessity of considering distinct pathophysiological aspects and therapeutic targets in AD between mouse models and humans. Consequently, this review delineates the distinct roles of cytokines in the pathogenesis of AD, juxtaposing their significance in human AD from clinical trials against insights gleaned from AD mouse models. This approach will improve our understanding of interspecies variation and facilitate a deeper insight into the pathogenesis of AD in humans.

Unraveling Atopic Dermatitis: Insights into Pathophysiology, Therapeutic Advances, and Future Perspectives

Atopic dermatitis (AD) is an inflammatory skin condition that frequently develops before the onset of allergic rhinitis or asthma. More than 10% of children are affected by this serious skin condition, which is painful for the sufferers. Recent research has connected the environment, genetics, the skin barrier, drugs, psychological factors, and the immune system to the onset and severity of AD. The causes and consequences of AD and its cellular and molecular origins are reviewed in this paper. The exploration of interleukins and their influence on the immunological pathway in AD has been facilitated by using relevant biomarkers in clinical trials. This approach enables the identification of novel therapeutic modalities, fostering the potential for targeted translational research within the realm of personalized medicine. This review focuses on AD's pathophysiology and the ever-changing therapeutic landscape. Beyond the plethora of biologic medications in various stages of approval or development, a range of non-biologic targeted therapies, specifically small molecules, have emerged. These include Janus kinase (JAK) inhibitors like Baricitinib, Upadacitinib, and Abrocitinib, thus expanding the spectrum of therapeutic options. This review also addresses the latest clinical efficacy data and elucidates the scientific rationale behind each targeted treatment for atopic dermatitis.

Inserting "OFF-to-ON" BODIPY Tags into Cytokines: A Fluorogenic Interleukin IL-33 for Real-Time Imaging of Immune Cells

The essential functions that cytokine/immune cell interactions play in tissue homeostasis and during disease have prompted the molecular design of targeted fluorophores to monitor their activity in real time. Whereas activatable probes for imaging immune-related enzymes are common, many immunological functions are mediated by binding events between cytokines and their cognate receptors that are hard to monitor by live-cell imaging. A prime example is interleukin-33 (IL-33), a key cytokine in innate and adaptive immunity, whose interaction with the ST2 cell-surface receptor results in downstream signaling and activation of NF-κB and AP-1 pathways. In the present work, we have designed a chemical platform to site-specifically introduce OFF-to-ON BODIPY fluorophores into full cytokine proteins and generate the first nativelike fluorescent analogues of IL-33. Among different incorporation strategies, chemical aminoacylation followed by bioorthogonal derivatization led to the best labeling results. Importantly, the BODIPY-labeled IL-33 derivatives-unlike IL-33-GFP constructs-exhibited ST2-specific binding and downstream bioactivity profiles comparable to those of the wild-type interleukin. Real-time fluorescence microscopy assays under no wash conditions confirmed the internalization of IL-33 through ST2 receptors and its intracellular trafficking through the endosomal pathway. We envision that the modularity and versatility of our BODIPY labeling platform will facilitate the synthesis of minimally tagged fluorogenic cytokines as the next generation of imaging reagents for real-time visualization of signaling events in live immune cells.

The MRGPR family of receptors in immunity

The discovery of Mas-related G protein-coupled receptors (Mrgprs) has opened a compelling chapter in our understanding of immunity and sensory biology. This family of receptors, with their unique expression and diverse ligands, has emerged as key players in inflammatory states and hold the potential to alleviate human diseases. This review will focus on the members of this receptor family expressed on immune cells and how they govern immune and neuro-immune pathways underlying various physiological and pathological states. Immune cell-specific Mrgprs have been shown to control a variety of manifestations, including adverse drug reactions, inflammatory conditions, bacterial immunity, and the sensing of environmental exposures like allergens and irritants.

Eosinophils-from cradle to grave: An EAACI task force paper on new molecular insights and clinical functions of eosinophils and the clinical effects of targeted eosinophil depletion

Over the past years, eosinophils have become a focus of scientific interest, especially in the context of their recently uncovered functions (e.g. antiviral, anti-inflammatory, regulatory). These versatile cells display both beneficial and detrimental activities under various physiological and pathological conditions. Eosinophils are involved in the pathogenesis of many diseases which can be classified into primary (clonal) and secondary (reactive) disorders and idiopathic (hyper)eosinophilic syndromes. Depending on the biological specimen, the eosinophil count in different body compartments may serve as a biomarker reflecting the underlying pathophysiology and/or activity of distinct diseases and as a therapy-driving (predictive) and monitoring tool. Personalized selection of an appropriate therapeutic strategy directly or indirectly targeting the increased number and/or activity of eosinophils should be based on the understanding of eosinophil homeostasis including their interactions with other immune and non-immune cells within different body compartments. Hence, restoring as well as maintaining homeostasis within an individual's eosinophil pool is a goal of both specific and non-specific eosinophil-targeting therapies. Despite the overall favourable safety profile of the currently available anti-eosinophil biologics, the effect of eosinophil depletion should be monitored from the perspective of possible unwanted consequences.

Strategies targeting IL-33/ST2 axis in the treatment of allergic diseases

Interleukin-33 (IL-33) and its receptor Serum Stimulation-2 (ST2, also called Il1rl1) are members of the IL-1 superfamily that plays a crucial role in allergic diseases. The interaction of IL-33 and ST2 mainly activates NF-κB signaling and MAPK signaling via the MyD88/IRAK/TRAF6 module, resulting in the production and secretion of pro-inflammatory cytokines. The IL-33/ST2 axis participates in the pathogenesis of allergic diseases, and therefore serves as a promising strategy for allergy treatment. In recent years, strategies blocking IL-33/ST2 through targeting regulation of IL-33 and ST2 or targeting the molecules involved in the signal transduction have been extensively studied mostly in animal models. These studies provide various potential therapeutic agents other than antibodies, such as small molecules, nucleic acids and traditional Chinese medicines. Herein, we reviewed potential targets and agents targeting IL-33/ST2 axis in the treatment of allergic diseases, providing directions for further investigations on treatments for IL-33 induced allergic diseases.

Synergism between IL-33 and MRGPRX2/FcεRI Is Primarily Due to the Complementation of Signaling Modules, and Only Modestly Supplemented by Prolonged Activation of Selected Kinases

Skin mast cells (MCs) express high levels of MRGPRX2, FcεRI, and ST2, and vigorously respond to their ligands when triggered individually. IL-33/ST2 also potently synergizes with other receptors, but the molecular underpinnings are poorly understood. Human skin-derived MCs were stimulated via different receptors individually or jointly in the presence/absence of selective inhibitors. TNF was quantified by ELISA. Signaling cascades were studied by immunoblot. TNF was stimulated by FcεRI ≈ ST2 > MRGPRX2. Surprisingly, neither FcεRI nor MRGPRX2 stimulation elicited NF-κB activation (IκB degradation, p65 phosphorylation) in stark contrast to IL-33. Accordingly, TNF production did not depend on NF-κB in FcεRI- or MRGPRX2-stimulated MCs, but did well so downstream of ST2. Conversely, ERK1/2 and PI3K were the crucial modules upon FcεRI/MRGPRX2 stimulation, while p38 was key to the IL-33-elicited route. The different signaling prerequisites were mirrored by their activation patterns with potent pERK/pAKT after FcεRI/MRGPRX2, but preferential induction of pp38/NF-κB downstream of ST2. FcεRI/MRGPRX2 strongly synergized with IL-33, and some synergy was still observed upon inhibition of each module (ERK1/2, JNK, p38, PI3K, NF-κB). IL-33's contribution to synergism was owed to p38 > JNK > NF-κB, while the partner receptor contributed through ERK > PI3K ≈ JNK. Concurrent IL-33 led to slightly prolonged pERK (downstream of MRGPRX2) or pAKT (activated by FcεRI), while the IL-33-elicited modules (pp38/NF-κB) remained unaffected by co-stimulation of FcεRI/MRGPRX2. Collectively, the strong synergistic activity of IL-33 primarily results from the complementation of highly distinct modules following co-activation of the partner receptor rather than by altered signal strength of the same modules.

The epithelial barrier: The gateway to allergic, autoimmune, and metabolic diseases and chronic neuropsychiatric conditions

Since the 1960 s, our health has been compromised by exposure to over 350,000 newly introduced toxic substances, contributing to the current pandemic in allergic, autoimmune and metabolic diseases. The "Epithelial Barrier Theory" postulates that these diseases are exacerbated by persistent periepithelial inflammation (epithelitis) triggered by exposure to a wide range of epithelial barrier-damaging substances as well as genetic susceptibility. The epithelial barrier serves as the body's primary physical, chemical, and immunological barrier against external stimuli. A leaky epithelial barrier facilitates the translocation of the microbiome from the surface of the afflicted tissues to interepithelial and even deeper subepithelial locations. In turn, opportunistic bacterial colonization, microbiota dysbiosis, local inflammation and impaired tissue regeneration and remodelling follow. Migration of inflammatory cells to susceptible tissues contributes to damage and inflammation, initiating and aggravating many chronic inflammatory diseases. The objective of this review is to highlight and evaluate recent studies on epithelial physiology and its role in the pathogenesis of chronic diseases in light of the epithelial barrier theory.

Mechanistic Insights into Eosinophilic Esophagitis: Therapies Targeting Pathophysiological Mechanisms

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease characterized by eosinophilic infiltration of the esophagus. It arises from a complex interplay of genetic predisposition (susceptibility loci), environmental triggers (allergens and dietary antigens), and a dysregulated immune response, mainly mediated by type 2 T helper cell (Th2)-released cytokines, such as interleukin (IL)-4, IL-5, and IL-13. These cytokines control eosinophil recruitment and activation as well as tissue remodeling, contributing to the characteristic features of EoE. The pathogenesis of EoE includes epithelial barrier dysfunction, mast cell activation, eosinophil degranulation, and fibrosis. Epithelial barrier dysfunction allows allergen penetration and promotes immune cell infiltration, thereby perpetuating the inflammatory response. Mast cells release proinflammatory mediators and promote eosinophil recruitment and the release of cytotoxic proteins and cytokines, causing tissue damage and remodeling. Prolonged inflammation can lead to fibrosis, resulting in long-term complications such as strictures and dysmotility. Current treatment options for EoE are limited and mainly focus on dietary changes, proton-pump inhibitors, and topical corticosteroids. Novel therapies targeting key inflammatory pathways, such as monoclonal antibodies against IL-4, IL-5, and IL-13, are emerging in clinical trials. A deeper understanding of the complex pathogenetic mechanisms behind EoE will contribute to the development of more effective and personalized therapeutic strategies.

IL-33 priming and antigenic stimulation synergistically promote the transcription of proinflammatory cytokine and chemokine genes in human skin mast cells

BACKGROUND

Antigenic stimulation through cross-linking the IgE receptor and epithelial cell-derived cytokine IL-33 are potent stimuli of mast cell (MC) activation. Moreover, IL-33 primes a variety of cell types, including MCs to respond more vigorously to external stimuli. However, target genes induced by the combined IL-33 priming and antigenic stimulation have not been investigated in human skin mast cells (HSMCs) in a genome-wide manner. Furthermore, epigenetic changes induced by the combined IL-33 priming and antigenic stimulation have not been evaluated.

RESULTS

We found that IL-33 priming of HSMCs enhanced their capacity to promote transcriptional synergy of the IL1B and CXCL8 genes by 16- and 3-fold, respectively, in response to combined IL-33 and antigen stimulation compared to without IL-33 priming. We identified the target genes in IL-33-primed HSMCs in response to the combined IL-33 and antigenic stimulation using RNA sequencing (RNA-seq). We found that the majority of genes synergistically upregulated in the IL-33-primed HSMCs in response to the combined IL-33 and antigenic stimulation were predominantly proinflammatory cytokine and chemokine genes. Moreover, the combined IL-33 priming and antigenic stimulation increase chromatin accessibility in the synergy target genes but not synergistically. Transcription factor binding motif analysis revealed more binding sites for NF-κB, AP-1, GABPA, and RAP1 in the induced or increased chromatin accessible regions of the synergy target genes.

CONCLUSIONS

Our study demonstrates that IL-33 priming greatly potentiates MCs' ability to transcribe proinflammatory cytokine and chemokine genes in response to antigenic stimulation, shining light on how epithelial cell-derived cytokine IL-33 can cause exacerbation of skin MC-mediated allergic inflammation.

Atopic dermatitis: a brief review of recent advances in its management

Atopic dermatitis (AD) is a common inflammatory skin disorder characterized by recurrent eczematous lesions and intense itching. The disorder affects people of all ages and ethnicities, has a substantial psychosocial impact on patients and relatives, and is the leading cause of the global burden of skin diseases. Atopic dermatitis is associated with an increased risk of multiple comorbidities, including food allergies, asthma, allergic rhinitis, and mental health disorders. The pathophysiology is complex and involves a strong genetic predisposition, epidermal dysfunction, and T-cell-driven inflammation. Although type-2 mechanisms are dominant, there is increasing evidence that the disorder involves multiple immune pathways. Until recently, the management of AD rested mainly on the judicious use of emollients, topical steroids, and topical calcineurin inhibitors in the majority of patients, and systemic immunosuppressants were advocated in severely diseased patients. However, in the last few years, new therapeutic strategies have been designed and developed to target the various steps in the chain of molecular events that lead to the AD phenotype. This review highlights the recent advancements in the management of AD.

Clinical trials of antibody drugs in the treatments of atopic dermatitis

Atopic dermatitis (AD) is one of the most common, relapsing, chronic inflammatory skin disease, being regarded as a global health issue. Recent studies have shown that Th2 cell-mediated type 2 immunity plays a central role in AD. The type 2 inflammatory cytokines such as IL-4, IL-13, IL-22, IL-31, IL-17 and IL-5 mediate the pathogenesis of AD. A variety of antibody drugs targeting these cytokines have been developed to treat AD in clinics. Notably, several antibody drugs have exhibited high efficacy in treating atopic dermatitis in previous studies, demonstrating that they could be therapeutic methods for AD patients. Herein, we reviewed the clinical trials of antibody drugs in the treatment of AD, which provides a useful guideline for clinicians to treat patients with AD in clinics.

Type 2 chronic inflammatory diseases: targets, therapies and unmet needs

Over the past two decades, significant progress in understanding of the pathogenesis of type 2 chronic inflammatory diseases has enabled the identification of compounds for more than 20 novel targets, which are approved or at various stages of development, finally facilitating a more targeted approach for the treatment of these disorders. Most of these newly identified pathogenic drivers of type 2 inflammation and their corresponding treatments are related to mast cells, eosinophils, T cells, B cells, epithelial cells and sensory nerves. Epithelial barrier defects and dysbiotic microbiomes represent exciting future drug targets for chronic type 2 inflammatory conditions. Here, we review common targets, current treatments and emerging therapies for the treatment of five major type 2 chronic inflammatory diseases - atopic dermatitis, chronic prurigo, chronic urticaria, asthma and chronic rhinosinusitis with nasal polyps - with a high need for targeted therapies. Unmet needs and future directions in the field are discussed.

Repressive Control of Keratinocyte Cytoplasmic Inflammatory Signaling

The overactivity of keratinocyte cytoplasmic signaling contributes to several cutaneous inflammatory and immune pathologies. An important emerging complement to proteins responsible for this overactivity is signal repression brought about by several proteins and protein complexes with the native role of limiting inflammation. The signaling repression by these proteins distinguishes them from transmembrane receptors, kinases, and inflammasomes, which drive inflammation. For these proteins, defects or deficiencies, whether naturally arising or in experimentally engineered skin inflammation models, have clearly linked them to maintaining keratinocytes in a non-activated state or returning cells to a post-inflamed state after a signaling event. Thus, together, these proteins help to resolve acute inflammatory responses or limit the development of chronic cutaneous inflammatory disease. We present here an integrated set of demonstrated or potentially inflammation-repressive proteins or protein complexes (linear ubiquitin chain assembly complex [LUBAC], cylindromatosis lysine 63 deubiquitinase [CYLD], tumor necrosis factor alpha-induced protein 3-interacting protein 1 [TNIP1], A20, and OTULIN) for a comprehensive view of cytoplasmic signaling highlighting protein players repressing inflammation as the needed counterpoints to signal activators and amplifiers. Ebb and flow of players on both sides of this inflammation equation would be of physiological advantage to allow acute response to damage or pathogens and yet guard against chronic inflammatory disease. Further investigation of the players responsible for repressing cytoplasmic signaling would be foundational to developing new chemical-entity pharmacologics to stabilize or enhance their function when clinical intervention is needed to restore balance.

Challenges and Future Trends in Atopic Dermatitis

Atopic dermatitis represents a complex and multidimensional interaction that represents potential fields of preventive and therapeutic management. In addition to the treatment armamentarium available for atopic dermatitis, novel drugs targeting significant molecular pathways in atopic dermatitis biologics and small molecules are also being developed given the condition's complex pathophysiology. While most of the patients are expecting better efficacy and long-term control, the response to these drugs would still depend on numerous factors such as complex genotype, diverse environmental triggers and microbiome-derived signals, and, most importantly, dynamic immune responses. This review article highlights the challenges and the recently developed pharmacological agents in atopic dermatitis based on the molecular pathogenesis of this condition, creating a specific therapeutic approach toward a more personalized medicine.

Microbiota and IL-33/31 Axis Linkage: Implications and Therapeutic Perspectives in Atopic Dermatitis and Psoriasis

Microbiome dysbiosis and cytokine alternations are key features of atopic dermatitis (AD) and psoriasis (PsO), two of the most prevalent and burdensome pruritic skin conditions worldwide. Interleukin (IL)-33 and IL-31 have been recognized to be major players who act synergistically in the pathogenesis and maintenance of different chronic inflammatory conditions and pruritic skin disorders, including AD and PsO, and their potential role as therapeutic targets is being thoroughly investigated. The bidirectional interplay between dysbiosis and immunological changes has been extensively studied, but there is still debate regarding which of these two factors is the actual causative culprit behind the aetiopathological process that ultimately leads to AD and PsO. We conducted a literature review on the Pubmed database assessing articles of immunology, dermatology, microbiology and allergology with the aim to strengthen the hypothesis that dysbiosis is at the origin of the IL-33/IL-31 dysregulation that contributes to the pathogenesis of AD and PsO. Finally, we discussed the therapeutic options currently in development for the treatment of these skin conditions targeting IL-31, IL-33 and/or the microbiome.

Management of eosinophil-associated inflammatory diseases: the importance of a multidisciplinary approach

Elevated eosinophil counts in blood and tissue are a feature of many pathological processes. Eosinophils can migrate and accumulate in a wide variety of tissues and, by infiltrating a target organ, can mediate the development of several inflammatory diseases. The normalization of eosinophilia is a common biomarker of a treatable trait and can also be used as a prognostic and predictive biomarker since it implies a reduction in type 2 inflammation that contributes to disease pathogenesis. Biological therapies targeting this cell type and its proinflammatory mediators have been shown to be effective in the management of a number of eosinophilic diseases, and for this reason they constitute a potential common strategy in the treatment of patients with various multimorbidities that present with type 2 inflammation. Various biological options are available that could be used to simultaneously treat multiple target organs with a single drug, bearing in mind the need to offer personalized treatments under the umbrella of precision medicine in all patients with eosinophil-associated diseases (EADs). In addition to reviewing these issues, we also discuss a series of perspectives addressing the management of EAD patients from a multidisciplinary approach, with the collaboration of health professionals from different specialties who manage the different multimorbidities that frequently occur in these patients. We examine the basic principles of care that this multidisciplinary approach must cover and present a multidisciplinary expert opinion regarding the ideal management of patients with EADs, from diagnosis to therapeutic approach and follow-up.

ILC2 require cell-intrinsic ST2 signals to promote type 2 immune responses

The initiation of type 2 immune responses at mucosal barriers is regulated by rapidly secreted cytokines called alarmins. The alarmins IL-33, IL-25 and TSLP are mainly secreted by stromal and epithelial cells in tissues and were linked to chronic inflammatory diseases, such as allergic lung inflammation, or to resistance against worm infections. Receptors for alarmins are expressed by a variety of immune cells, including group 2 innate lymphoid cells (ILC2s), an early source of the type 2 cytokines, such as IL-5 and IL-13, which have been linked to atopic diseases and anti-worm immunity as well. However, the precise contribution of the IL-33 receptor signals for ILC2 activation still needs to be completed due to limitations in targeting genes in ILC2. Using the newly established Nmur1 iCre-eGFP mouse model, we obtained specific conditional genetic ablation of the IL-33 receptor subunit ST2 in ILC2s. ST2-deficient ILC2s were unresponsive to IL-33 but not to stimulation with the alarmin IL-25. As a result of defective ST2 signals, ILC2s produced limited amounts of IL-5 and IL-13 and failed to support eosinophil homeostasis. Further, ST2-deficient ILC2s were unable to expand and promote the recruitment of eosinophils during allergic lung inflammation provoked by papain administration. During infection with Nippostrongylus brasiliensis, ILC2-intrinsic ST2 signals were required to mount an effective type 2 immune response against the parasite leading to higher susceptibility against worm infection in conditional knockout mice. Therefore, this study argues for a non-redundant role of cell-intrinsic ST2 signals triggering proper activation of ILC2 for initiation of type 2 immunity.

SUMOylated IL-33 in the nucleus stabilizes the transcription factor IRF1 in hepatocellular carcinoma cells to promote immune escape

Interleukin-33 (IL-33) functions both as a secreted cytokine and as a nuclear factor, with pleiotropic roles in cancer and immunity. Here, we explored its role in hepatocellular carcinoma (HCC) and identified that a posttranslational modification altered its nuclear activity and promoted immune escape for HCC. IL-33 abundance was overall decreased but more frequently localized to the nucleus in patient HCC tissues than in normal liver tissues. In human and mouse HCC cells in culture and in vivo, IL-33 overexpression inhibited proliferation and repressed the abundance of programmed death ligand 1 (PD-L1) at the transcriptional level by promoting the ubiquitin-dependent degradation of interferon regulatory factor 1 (IRF1). However, this interaction was disrupted by SUMOylation of IL-33 at Lys⁵⁴ mediated by the E3 ligase RanBP2. IL-33 SUMOylation correlated with its nuclear localization in HCC cells and tumors. An increase in SUMOylated IL-33 in HCC cells in cocultures and in vivo stabilized IRF1 and increased PD-L1 abundance and chemokine IL-8 secretion, which prevented the activation of cytotoxic T cells and promoted the M2 polarization of macrophages, respectively. Mutating the SUMOylation site in IL-33 reversed these effects and suppressed tumor growth. These findings indicate that SUMOylation of nuclear IL-33 in HCC cells impairs antitumor immunity.

Pruritogenic Mediators and New Antipruritic Drugs in Atopic Dermatitis

Atopic dermatitis (AD) is a common highly pruritic chronic inflammatory skin disorder affecting 5-20% of children worldwide, while the prevalence in adults varies from 7 to 10%. Patients with AD experience intense pruritus that could lead to sleep disturbance and impaired quality of life. Here, we analyze the pathophysiology of itchiness in AD. We extensively review the histamine-dependent and histamine-independent pruritogens. Several receptors, substance P, secreted molecules, chemokines, and cytokines are involved as mediators in chronic itch. We also, summarize the new emerging antipruritic drugs in atopic dermatitis.

IL-33 induces histidine decarboxylase, especially in c-kit+ cells and mast cells, and roles of histamine include negative regulation of IL-33-induced eosinophilia

OBJECTIVE AND METHODS

IL-33 is present in endothelial, epithelial, and fibroblast-like cells and released upon cell injury. IL-33 reportedly induces mast-cell degranulation and is involved in various diseases, including allergic diseases. So, IL-33-related diseases seem to overlap with histamine-related diseases. In addition to the release from mast cells, histamine is newly formed by the induction of histidine decarboxylase (HDC). Some inflammatory and/or hematopoietic cytokines (IL-1, IL-3, etc.) are known to induce HDC, and the histamine produced by HDC induction is released without storage. We examined the involvement of HDC and histamine in the effects of IL-33.

RESULTS

A single intraperitoneal injection of IL-33 into mice induced HDC directly and/or via other cytokines (including IL-5) within a few hours in various tissues, particularly strongly in hematopoietic organs. The major cells exhibiting HDC-induction were mast cells and c-kit⁺ cells in the bone marrow. HDC was also induced in non-mast cells in non-hematopoietic organs. HDC, histamine, and histamine H4 receptors (H4Rs) contributed to the suppression of IL-33-induced eosinophilia.

CONCLUSION

IL-33 directly and indirectly (via IL-5) induces HDC in various cells, particularly potently in c-kit⁺ cells and mature mast cells, and the newly formed histamine contributes to the negative regulation of IL-33-induced eosinophilia via H4Rs.

IRAK4 inhibition dampens pathogenic processes driving inflammatory skin diseases

Innate immunity not only shapes the way epithelial barriers interpret environmental cues but also drives adaptive responses. Therefore, modulators of innate immune responses are expected to have high therapeutic potential across immune-mediated inflammatory diseases. IRAK4 is a kinase that integrates signaling downstream of receptors acting at the interface between innate and adaptive immune responses, such as Toll-like receptors (TLRs), interleukin-1R (IL-1R), and IL-18R. Because effects of IRAK4 inhibition are stimulus, cell type, and species dependent, the evaluation of the therapeutic potential of IRAK4 inhibitors requires a highly translational approach. Here, we profiled a selective IRAK4 inhibitor, GLPG2534, in an extensive panel of models of inflammatory skin diseases, translationally expanding evidence from in vitro to in vivo and from mouse to human. In vitro, IRAK4 inhibition resulted in substantial inhibition of TLR and IL-1 responses in dendritic cells, keratinocytes, granulocytes, and T cells but only weakly affected dermal fibroblast responses. Furthermore, disease activity in murine models of skin inflammation (IL-23-, IL-33-, imiquimod-, and MC903-induced) was markedly dampened by IRAK4 inhibition. Last, inhibiting IRAK4 reversed pathogenic molecular signatures in human lesional psoriasis and atopic dermatitis biopsies. Over the variety of models used, IRAK4 inhibition consistently affected central mediators of psoriasis (IL-17A) and atopic dermatitis (IL-4 and IL-13). Overall, our data highlight IRAK4 as a central player in skin inflammatory processes and demonstrate the potential of IRAK4 inhibition as a therapeutic strategy in chronic inflammatory skin diseases.

Neural Regulation of Innate Immunity in Inflammatory Skin Diseases

As the largest barrier organ of the body, the skin is highly innervated by peripheral sensory neurons. The major function of these sensory neurons is to transmit sensations of temperature, pain, and itch to elicit protective responses. Inflammatory skin diseases are triggered by the aberrant activation of immune responses. Recently, increasing evidence has shown that the skin peripheral nervous system also acts as a regulator of immune responses, particularly innate immunity, in various skin inflammatory processes. Meanwhile, immune cells in the skin can express receptors that respond to neuropeptides/neurotransmitters, leading to crosstalk between the immune system and nervous system. Herein, we highlight recent advances of such bidirectional neuroimmune interactions in certain inflammatory skin conditions.

Beyond allergic progression: From molecules to microbes as barrier modulators in the gut-lung axis functionality

The "epithelial barrier hypothesis" states that a barrier dysfunction can result in allergy development due to tolerance breakdown. This barrier alteration may come from the direct contact of epithelial and immune cells with the allergens, and indirectly, through deleterious effects caused by environmental changes triggered by industrialization, pollution, and changes in the lifestyle. Apart from their protective role, epithelial cells can respond to external factors secreting IL-25 IL-33, and TSLP, provoking the activation of ILC2 cells and a Th2-biased response. Several environmental agents that influence epithelial barrier function, such as allergenic proteases, food additives or certain xenobiotics are reviewed in this paper. In addition, dietary factors that influence the allergenic response in a positive or negative way will be also described here. Finally, we discuss how the gut microbiota, its composition, and microbe-derived metabolites, such as short-chain fatty acids, alter not only the gut but also the integrity of distant epithelial barriers, focusing this review on the gut-lung axis.

Immunopathogenesis of Atopic Dermatitis: Focus on Interleukins as Disease Drivers and Therapeutic Targets for Novel Treatments

Atopic dermatitis is a chronic, recurrent inflammatory skin disorder manifesting by eczematous lesions and intense pruritus. Atopic dermatitis develops primarily as a result of an epidermal barrier defect and immunological imbalance. Advances in understanding these pathogenetic hallmarks, and particularly the complex role of interleukins as atopic dermatitis drivers, resulted in achieving significant therapeutic breakthroughs. Novel medications involve monoclonal antibodies specifically blocking the function of selected interleukins and small molecules such as Janus kinase inhibitors limiting downstream signaling to reduce the expression of a wider array of proinflammatory factors. Nevertheless, a subset of patients remains refractory to those treatments, highlighting the complexity of atopic dermatitis immunopathogenesis in different populations. In this review, we address the immunological heterogeneity of atopic dermatitis endotypes and phenotypes and present novel interleukin-oriented therapies for this disease.

Upadacitinib for moderate-to-severe atopic dermatitis, in adults and adolescents 12 years and older: review of international and Japanese populations

INTRODUCTION

Atopic dermatitis is one of the most prevalent chronic skin diseases. Topical therapies continue to be the mainstay of treatment but are limited by noncompliance and side-effects from inappropriate or long-term use. Systemic therapies including cyclosporine and dupilumab have been the treatments of choice for refractory cases. However, outcomes may remain less than satisfactory, and cyclosporine use is further limited by nephrotoxicity.Upadacitinib, an oral Janus kinase inhibitor, is widely used for treating rheumatoid arthritis, psoriatic arthritis, and ankylosing spondylitis and has recently received approval for atopic dermatitis in the United States, Europe, Japan, and other countries. These approvals were based on results from several randomized controlled trials in which upadacitinib demonstrated better and faster response versus placebo or dupilumab.

AREA COVERED

Therapies for atopic dermatitis are reviewed, with emphasis on drug profile, efficacy, and safety profile of upadacitinib for atopic dermatitis. In the review of the clinical trials, special focus is placed on efficacy in the Japanese population.

EXPERT OPINION

Currently, there are several treatment options for atopic dermatitis refractory to topical therapies. However, appropriate utilization of Janus kinase inhibitors in clinical practice remains challenging, especially with regard to proper case selection, optimal timing, and appropriateness of use.

Impact of a Decade of Research Into Atopic Dermatitis

The last decade has seen an unprecedented pace of change, particularly of clinical research in atopic dermatitis (AD). This review summarizes some key discoveries. Over the last 10 years, nearly half of all studies investigated the efficacy and safety of novel therapeutic agents, particularly biologics and small molecules. Clear demonstration of benefit in clinical trials with no significant safety concerns provided strong evidence leading to subsequent Food and Drug Administration approval and routine use of the anti-IL-4 receptor alpha antagonist dupilumab in patients 6 months and older, the selective Janus kinase 1 (JAK1) inhibitors upadacitinib for patients 12 years and older and abrocitinib, the IL-13 antagonist tralokinumab, and the JAK1/2 inhibitor baricitinib for adults 18 years and older. Several other drugs are in the pipeline. Other areas under the spotlight have been trials of skin moisturizers and probiotics in the prevention of AD, investigating the role of filaggrin and skin barrier function and the role of skin and gut microbiome, with Staphylococcus aureus second immunoglobulin-binding protein having been found to uniquely trigger allergic skin responses in AD. Skin microbiome, epidermal metabolites/structural components, and local inflammatory biomarkers are now commonly assessed using genomic and proteomic analysis of tape strips rather than more invasive biopsy to identify factors such as C-C motif chemokine ligand-17 that correlate with disease severity and response to therapy. Overall, the last decade has ushered in a new and exciting era in our understanding, diagnosis, and treatment of this common allergic skin disease.

FRTX-02, a selective and potent inhibitor of DYRK1A, modulates inflammatory pathways in mouse models of psoriasis and atopic dermatitis

Dual-specificity tyrosine phosphorylation-regulated kinase 1 A (DYRK1A) has been proposed as a novel regulator of adaptive immune homeostasis through modulating T cell polarization. Thus, DYRK1A could present a potential target in autoimmune disorders. Here, we identify FRTX-02 as a novel compound exhibiting potent and selective inhibition of DYRK1A. FRTX-02 induced transcriptional activity of the DYRK1A substrate NFAT in T cell lines. Correspondingly, FRTX-02 promoted ex vivo CD4⁺ polarization into anti-inflammatory Tregs and reduced their polarization into pro-inflammatory Th1 or Th17 cells. We show that FRTX-02 could also limit innate immune responses through negative regulation of the MyD88/IRAK4-NF-κB axis in a mast cell line. Finally, in mouse models of psoriasis and atopic dermatitis, both oral and topical formulations of FRTX-02 reduced inflammation and disease biomarkers in a dose-dependent manner. These results support further studies of DYRK1A inhibitors, including FRTX-02, as potential therapies for chronic inflammatory and autoimmune conditions.

T-Cell Mediated Immunity in Merkel Cell Carcinoma

Merkel cell carcinoma (MCC) is a rare and frequently lethal skin cancer with neuroendocrine characteristics. MCC can originate from either the presence of MCC polyomavirus (MCPyV) DNA or chronic ultraviolet (UV) exposure that can cause DNA mutations. MCC is predominant in sun-exposed regions of the body and can metastasize to regional lymph nodes, liver, lungs, bone, and brain. Older, light-skinned individuals with a history of significant sun exposure are at the highest risk. Previous studies have shown that tumors containing a high number of tumor-infiltrating T-cells have favorable survival, even in the absence of MCPyV DNA, suggesting that MCPyV infection enhances T-cell infiltration. However, other factors may also play a role in the host antitumor response. Herein, we review the impact of tumor infiltrating lymphocytes (TILs), mainly the CD4⁺, CD8⁺, and regulatory T-cell (Tregs) responses on the course of MCC, including their role in initiating MCPyV-specific immune responses. Furthermore, potential research avenues related to T-cell biology in MCC, as well as relevant immunotherapies are discussed.

Phase 2 randomized clinical trial of astegolimab in patients with moderate to severe atopic dermatitis

BACKGROUND

The binding of IL-33 to its receptor ST2 (alias of IL1RL1) leads to the release of inflammatory mediators and may play a role in the pathogenesis of atopic dermatitis. Astegolimab is a fully human, IgG₂ mAb that binds to ST2 and inhibits IL-33 signaling.

OBJECTIVES

This study sought to assess the efficacy, safety, and pharmacokinetics of astegolimab in patients with atopic dermatitis.

METHODS

This was a randomized, placebo-controlled, phase 2 study in which adults with chronic atopic dermatitis were randomized 1:1 to receive astegolimab 490 mg every 4 weeks or placebo, for 16 weeks. The primary outcome was the percentage of change from baseline to week 16 of the Eczema Area and Severity Index score.

RESULTS

A total of 65 patients were enrolled in the study (placebo, n = 32; astegolimab, n = 33). The adjusted mean percentage of change from baseline to week 16 in the Eczema Area and Severity Index score was -51.47% for astegolimab compared with -58.24% for placebo, with a nonsignificant treatment difference of 6.77% (95% CI: -16.57-30.11; P = .5624). No differences were observed between treatment groups for secondary efficacy outcomes and in exploratory biomarkers (blood eosinophils, serum IL-5, serum CCL13). With the use of loading dose, pharmacokinetic exposure was sufficient from week 1. Astegolimab was well-tolerated, with a safety profile consistent with that observed in previous clinical trials.

CONCLUSIONS

In patients with atopic dermatitis, astegolimab did not show a significant difference compared to placebo for the primary or secondary outcomes.

TSLP, IL-33, and IL-25: Not just for allergy and helminth infection

The release of cytokines from epithelial and stromal cells is critical for the initiation and maintenance of tissue immunity. Three such cytokines, thymic stromal lymphopoietin, IL-33, and IL-25, are important regulators of type 2 immune responses triggered by parasitic worms and allergens. In particular, these cytokines activate group 2 innate lymphoid cells, TH2 cells, and myeloid cells, which drive hallmarks of type 2 immunity. However, emerging data indicate that these tissue-associated cytokines are not only involved in canonical type 2 responses but are also important in the context of viral infections, cancer, and even homeostasis. Here, we provide a brief review of the roles of thymic stromal lymphopoietin, IL-33, and IL-25 in diverse immune contexts, while highlighting their relative contributions in tissue-specific responses. We also emphasize a biologically motivated framework for thinking about the integration of multiple immune signals, including the 3 featured in this review.

IL-33 induces thymic involution-associated naive T cell aging and impairs host control of severe infection

Severe infection commonly results in immunosuppression, which leads to impaired pathogen clearance or increased secondary infection in both humans and animals. However, the exact mechanisms remain poorly understood. Here, we demonstrate that IL-33 results in immunosuppression by inducing thymic involution-associated naive T cell dysfunction with aberrant expression of aging-associated genes and impairs host control of infection in mouse disease models of schistosomiasis or sepsis. Furthermore, we illustrate that IL-33 triggers the excessive generation of medullary thymic epithelial cell (mTEC) IV (thymic tuft cells) in a Pou2f3-dependent manner, as a consequence, disturbs mTEC/cortical TEC (cTEC) compartment and causes thymic involution during severe infection. More importantly, IL-33 deficiency, the anti-IL-33 neutralizing antibody treatment, or IL-33 receptor ST2 deficient thymus transplantation rescues T cell immunity to better control infection in mice. Our findings not only uncover a link between severe infection-induced IL-33 and thymic involution-mediated naive T cell aging, but also suggest that targeting IL-33 or ST2 is a promising strategy to rejuvenate T cell immunity to better control severe infection.

Biologics for allergy: therapeutic potential for ocular allergic diseases and adverse effects on the eye

Biologics applying antibodies against IgE, IL-5, IL-5 receptor α, IL-4 receptor α, and IL-13 have dramatically improved recent treatment outcomes in allergic diseases including asthma, rhinitis, and atopic dermatitis. However, these drugs have not been approved for ocular allergic diseases such as allergic conjunctivitis, vernal keratoconjunctivitis, and atopic keratoconjunctivitis. Although the putative mechanisms suggest that these drugs should have beneficial effects in patients with ocular allergies and some studies have reported such beneficial effects, various adverse ocular symptoms have also been observed in clinical trials and off-label use studies. Since ocular allergic diseases have distinct pathogeneses, each biologic drug must be examined regarding specific effects on each ocular allergy. For example, IgE-mediated type 1 hypersensitivity plays a critical role in allergic conjunctivitis. By contrast, T cells and eosinophilic and non-IgE-mediated type 2 inflammation play important roles in vernal keratoconjunctivitis. Allergists must fully understand the effects of each drug on the eye. This review outlines both potential therapeutic and adverse effects of various biologics on allergic diseases of the eye.

A Systematic Review of Atopic Dermatitis: The Intriguing Journey Starting from Physiopathology to Treatment, from Laboratory Bench to Bedside

Atopic dermatitis (AD) is a common chronic inflammatory and immune-mediated skin disease with a complex pathophysiology and still represents a therapeutic challenge, owing to limited responses to available treatments. However, recent advances in the understanding of AD pathophysiology have led to the discovery of several new potential therapeutic targets, and research in the field of new molecules with therapeutic perspectives is boiling, with more than 70 new promising drugs in development. The aim of this systematic review is to provide the state of the art on the current knowledge concerning the pathophysiology of the disease and on novel agents currently being investigated for AD, and to highlight which type of evolution is going to take place in therapeutic approaches of atopic dermatitis in the coming years.

Gastric alarmin release: A warning signal in the development of gastric mucosal diseases

Alarmins exist outside cells and are early warning signals to the immune system; as such, alarmin receptors are widely distributed on various immune cells. Alarmins, proinflammatory molecular patterns associated with tissue damage, are usually released into the extracellular space, where they induce immune responses and participate in the damage and repair processes of mucosal diseases.In the stomach, gastric alarmin release has been shown to be involved in gastric mucosal inflammation, antibacterial defense, adaptive immunity, and wound healing; moreover, this release causes damage and results in the development of gastric mucosal diseases, including various types of gastritis, ulcers, and gastric cancer. Therefore, it is necessary to understand the role of alarmins in gastric mucosal diseases. This review focuses on the contribution of alarmins, including IL33, HMGB1, defensins and cathelicidins, to the gastric mucosal barrier and their role in gastric mucosal diseases. Here, we offer a new perspective on the prevention and treatment of gastric mucosal diseases.

Eosinophilic esophagitis: Immune mechanisms and therapeutic targets

Eosinophilic esophagitis (EoE) is an emerging chronic inflammatory disease of the oesophagus and is clinically characterized by upper gastrointestinal (GI) symptoms including dysphagia and esophageal food impaction. Histopathologic manifestations, which include intraepithelial eosinophilic inflammation and alterations of the esophageal squamous epithelium, such as basal zone hyperplasia (BZH) and dilated intercellular spaces (DIS), are thought to contribute to esophageal dysfunction and disease symptoms. Corroborative clinical and discovery science-based studies have established that EoE is characterized by an underlying allergic inflammatory response, in part, related to the IL-13/CCL26/eosinophil axis driving dysregulation of several key epithelial barrier and proliferative regulatory genes including kallikrein (KLK) serine proteases, calpain 14 (CAPN14) and anoctamin 1 (ANO1). The contribution of these inflammatory and proliferative processes to the clinical and histological manifestations of disease are not fully elucidated. Herein, we discuss the immune molecules and cells that are thought to underlie the clinical and pathologic manifestations of EoE and the emerging therapeutics targeting these processes for the treatment of EoE.