Immunotargets and Therapy for Prurigo Nodularis

A critical evaluation of nemolizumab for prurigo nodularis

INTRODUCTION

Prurigo nodularis (PN) is a chronic inflammatory skin condition that presents with intensely pruritic, hyperkeratotic nodules. The pathophysiology underlying PN is not entirely clear, making treatment challenging. Patients often require a multimodal approach, although many of the available therapies have low efficacy or adverse effects.

AREAS COVERED

In this review, we discuss the use of nemolizumab for the treatment of PN in adults. Nemolizumab is a biological therapy that reduces type 2 cytokines and the neuroimmune response implicated in the pathophysiology of PN. It also helps maintain skin barrier integrity, which may be damaged during the vicious itch-scratch cycle. Nemolizumab has demonstrated great efficacy in improving itch and clearing lesions in recent clinical trials with respectable tolerance.

EXPERT OPINION

Nemolizumab is a promising drug for PN that seems comparable to the recently approved dupilumab in terms of its therapeutic effect and excellent safety profile, although nemolizumab may work more rapidly on itch. JAK inhibitors are also emerging as competitors of biologics for PN, however, their safety profile in this population may differ. Trials evaluating these drugs are needed to assess which is preferable. Additional data on the durability and longevity of nemolizumab for PN treatment is highly anticipated.

Prurigo Nodularis: Pathogenesis and the Horizon of Potential Therapeutics

Chronic pruritus that lasts for over 6 weeks can present in various forms, like papules, nodules, and plaque types, with prurigo nodularis (PN) being the most prevalent. The pathogenesis of PN involves the dysregulation of immune cell-neural circuits and is associated with peripheral neuropathies, possibly due to chronic scratching. PN is a persistent and challenging condition, involving complex interactions among the skin, immune system, and nervous system. Lesional skin in PN exhibits the infiltration of diverse immune cells like T cells, eosinophils, macrophages, and mast cells, leading to the release of inflammatory cytokines and itch-inducing substances. Activated sensory nerve fibers aggravate pruritus by releasing neurotransmitters, perpetuating a vicious cycle of itching and scratching. Traditional treatments often fail, but recent advancements in understanding the inflammatory and itch transmission mechanisms of PN have paved the way for innovative therapeutic approaches, which are explored in this review.

A critical review of dupilumab for adult patients with prurigo nodularis

INTRODUCTION

Prurigo nodularis (PN) is a chronic inflammatory skin condition that presents with pruritus and hyperkeratotic nodules. These symptoms impact patients' quality of life and mental health. Treating prurigo nodularis is challenging, and many of the available topical and systemic therapies have limited efficacy and a myriad of adverse effects.

AREAS COVERED

In this article, we discuss the use of dupilumab for adult patients with prurigo nodularis. Dupilumab is a biologic that inhibits Th2-mediated inflammation and has been successfully used to treat a variety of dermatologic disorders. Dupilumab has revolutionized the management of PN, with recent clinical trials showing its efficacy in treating both pruritus and prurigo nodules, as well as improving quality of life. It has a favorable safety profile and is well tolerated. Other novel treatments are also currently under investigation for the treatment of PN, with early studies reporting promising results.

EXPERT OPINION

Dupilumab is becoming the drug of choice for the treatment of PN and may also be effective in treating patients with systemic underlying causes of their PN, although more studies are needed to assess this. Trials evaluating the long-term efficacy and durability of dupilumab in PN are also of interest.

Clinical Characteristics and Treatment Outcomes of Prurigo Nodularis: A Retrospective Study

BACKGROUND

Prurigo nodularis (PN) is a complex chronic skin disease characterized by severe pruritic nodules. PN is often associated with mental health disorders and chronic medical comorbidities. Until recently, PN treatment has been challenging and difficult.

OBJECTIVES

This study aims to describe the demographic, clinical characteristics, and comorbidities associated with PN. Also, we aim to describe the effectiveness of systemic therapies, including methotrexate, cyclosporine, and narrow band ultraviolet (NB-UVB) in adult patients with PN.

METHODS

This is a retrospective chart review of adult patients diagnosed with PN at Hamilton Health Science Center and/or McMaster University in Hamilton, Ontario, between 2015 and 2023.

RESULTS

The study included 81 patients (57% female). The mean age was 52.8 years, and the mean age of PN diagnosis was 50 years. Reported symptoms included: itching (100%), dry skin (53%), pain (17%), and burning sensation (5%). Lower and upper extremities were the most common areas involved in 93% and 69%, respectively. Mental health disorders were present in 79% of patients, with depression (58%) and anxiety (52%) being the most common. Atopic dermatitis was the most common skin comorbidity noted. Treatments used included cyclosporine, and NB-UVB, and MTX, which resulted in significant improvement of pruritus in 38%, 35%, and 31% of patients, respectively, at week 16.

CONCLUSIONS

PN is associated with increased risk of mental health disorders and other medical comorbidities. Cyclosporine, methotrexate, and NB-UVB therapy may be effective treatment options, however clinicians must consider the potential short- and long-term adverse effects of these treatments.

Chronic Prurigo Including Prurigo Nodularis: New Insights and Treatments

Chronic prurigo (CPG) is a neuroinflammatory, fibrotic dermatosis that is defined by the presence of chronic pruritus (itch lasting longer than 6 weeks), scratch-associated pruriginous skin lesions and history of repeated scratching. Patients with CPG experience a significant psychological burden and a notable impairment in their quality of life. Chronic prurigo of nodular type (CNPG; synonym: prurigo nodularis) represents the most common subtype of CPG. As CNPG is representative for all CPG subtypes, we refer in this review to both CNPG and CPG. We provide an overview of the clinical characteristics and assessment of CPG, the burden of disease and the underlying pathophysiology including associated therapeutic targets. The information provided results from a PubMed search for the latest publications and a database search for current clinical trials (ClinicalTrials.gov, EU Clinical Trials Register [European Medicines Agency]; using the following terms or combinations of terms: 'chronic prurigo', 'prurigo', 'prurigo nodularis', 'pathophysiology', 'therapy', 'biologics', 'treatment'). Dupilumab is the first authorized systemic therapy by the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA) for CNPG to date. Topical and systemic agents that are currently under investigation in clinical randomized, placebo-controlled phase II and III trials such as biologics (e.g., nemolizumab, vixarelimab/KPL-716, barzolvolimab/CDX-0159), small molecules (ruxolitinib cream, povorcitinib/INCB054707, abrocitinib) and the opioid modulator nalbuphine are highlighted. In the last past 15 years, several milestones have been reached regarding the disease understanding of CPG such as first transcriptomic analysis, first terminology, first guideline, and first therapy approval in 2022, which contributed to improved medical care of affected patients. The broad range of identified targets, current case observations and initiated trials offers the possibility of more drug approvals in the near future.

A case-control study addressing the population of epidermal and dermal inflammatory infiltrate including neural milieu in primary prurigo nodularis using S-100 and toluidine blue stain and its therapeutic implications

BACKGROUND

The pathogenesis of prurigo nodularis (PN) is considered to be multifactorial, with numerous cells and cytokines confabulating to produce an aberrant immune response.

METHODS

A cross-sectional observational study was done in cases of untreated primary prurigo nodularis cases with histopathological assessment in 49 cases from lesional and nonlesional skin with assessment of epidermal and dermal changes, dermal infiltrate, S-100 and toluidine blue staining to assess the expression of nerve and mast cells.

RESULTS

The most common histological changes seen in lesional skin were hyperkeratosis (98%), irregular hyperplasia (69.4%), hypergranulosis (69.4%), subepidermal clefting (6%), vertical collagen bundles (51.0%), and dermal fibrosis (48.9%). Chronic inflammatory infiltrate was seen in all cases (100%) predominantly of lymphocytes (100%) followed by eosinophils (18.4%), plasma cells (8.2%), and neutrophils (2.0%). There was a marked increase in the expression of S-100 (6.92 ± 3.40 vs. 3.94 ± 2.15, P < 0.001) and toluidine blue (4.99 ± 4.47 vs. 1.22 ± 1.28, P < 0.001) in the lesional skin as compared to the nonlesional skin.

CONCLUSION

We can infer that the epidermal and dermal pathology in PN is related to the infiltrate of lymphocytes, mast cells, and neural hyperplasia which perpetuate the pathogenesis by triggering the itch-inflammation cycle. Thus, apart from immunosuppressive agents that target lymphocytes and their cytokines, therapy targeted at mast cells and neural proliferation may be needed to treat prurigo nodularis.

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.

Single-cell RNA sequencing defines disease-specific differences between chronic nodular prurigo and atopic dermatitis

BACKGROUND

Chronic nodular prurigo (CNPG) is an inflammatory skin disease that is maintained by a chronic itch-scratch cycle likely rooted in neuroimmunological dysregulation. This condition may be associated with atopy in some patients, and there are now promising therapeutic results from blocking type 2 cytokines such as IL-4, IL-13, and IL-31.

OBJECTIVES

This study aimed to improve the understanding of pathomechanisms underlying CNPG as well as molecular relationships between CNPG and atopic dermatitis (AD).

METHODS

We profiled skin lesions from patients with CNPG in comparison with AD and healthy control individuals using single-cell RNA sequencing combined with T-cell receptor sequencing.

RESULTS

We found type 2 immune skewing in both CNPG and AD, as evidenced by CD4+ helper T cells expressing IL13. However, only AD harbored an additional, oligoclonally expanded CD8A+IL9R+IL13+ cytotoxic T-cell population, and immune activation pathways were highly upregulated in AD, but less so in CNPG. Conversely, CNPG showed signatures of extracellular matrix organization, collagen synthesis, and fibrosis, including a unique population of CXCL14-IL24+ secretory papillary fibroblasts. Besides known itch mediators such as IL31 and oncostatin M, we also detected increased levels of neuromedin B in fibroblasts of CNPG lesions compared with AD and HC, with neuromedin B receptors detectable on some nerve endings.

CONCLUSIONS

These data show that CNPG does not harbor the strong disease-specific immune activation pathways that are typically found in AD but is rather characterized by upregulated stromal remodeling mechanisms that might have a direct impact on itch fibers.

Dupilumab Therapy of Prurigo Nodularis: A Single-Center, Real-Life Observational Study

Prurigo nodularis (PN) is a chronic inflammatory skin disease characterized by severe itching accompanied by multiple nodules throughout the body. There is currently no effective drug-targeted treatment for PN. Dupilumab is a fully human monoclonal antibody which can suppress the Th2 inflammatory reaction. We aimed to assess the efficacy and safety of dupilumab in PN. There were 29 PN patients who received dupilumab treatment for four months. Serum total immunoglobulin E (Ig E), eosinophil counts, dermatology life quality index (DLQI), and numeric rating scale (NRS) were assessed on patients before and after treatment. We count the vaccination of novel coronavirus pneumonia (COVID-19) in patients and the impact on PN and treatment measures after vaccination. Plotting was performed using GraphPad Prism8, and the statistical analysis was performed using PASW Statistics18. The eosinophil counts in patients higher decreased to normal, and the Ig E levels gradually decreased and tended to normal levels after receiving dupilumab injection. The average DLQI score at the baseline was 23.93 ± 0.66 and decreased to 11.66 ± 0.55 ( $P<0.01$ ) and 1.83 ± 0.22 ( $P<0.01$ ) at 1-month and 6-monthfollow-up of treatment, respectively. The average NRS score at the baseline was 9.79 ± 0.08 and decreased to 3.52 ± 0.23 ( $P<0.01$ ) and 0.31 ± 0.15 ( $P<0.01$ ) at the 1-month and 6-monthfollow-up of treatment, respectively. Our study shows that dupilumab has achieved good efficacy in PN with few adverse reactions and high safety. We can recommend that patients follow the advice of specialists to be vaccinated and under the condition of stable disease, separated from dupilumab treatment for one week.

How to get rid of itching

Itch is an unpleasant sensation arising from a variety of dermatologic, neuropathic, systemic, and psychogenic etiologies. Various itch pathways are implicated according to the underlying etiology. A variety of pruritogens, or itch mediators, as well as receptors have been identified and provide potential therapeutic targets. Recent research has primarily focused on targeting inflammatory cytokines and Janus kinase signaling, protease-activated receptors, substance P and neurokinin, transient receptor potential-vanilloid ion channels, Mas-related G-protein-coupled receptors (MRGPRX2 and MRGPRX4), the endogenous opioid and cannabinoid balance, and phosphodiesterase 4. Periostin, a newly identified pruritogen, should be further explored with clinical trials. Drugs targeting neural sensitization including the gabergic system and P2X3 are other potential drugs for chronic itch. There is a need for more targeted therapies to improve clinical outcomes and reduce side effects.

Circulating plasma IL-13 and periostin are dysregulated type 2 inflammatory biomarkers in prurigo nodularis: A cluster analysis

Importance

Prurigo nodularis (PN) is a chronic heterogeneous inflammatory skin disease.

Objective

To elucidate which components of type 2 inflammation are dysregulated systemically in PN.

Design

Whole blood was obtained from PN patients with uncontrolled disease and control patients without pruritus. Plasma was assayed for IL-4, IL-5, IL-13, IgE, and periostin. ANOVA was utilized to compare PN and control patients and multiple-hypothesis adjusted p-value was calculated with the significance threshold at 0.05. Clustering was performed using K-means clustering.

Participants

PN patients (n = 29) and controls (n = 18) from Johns Hopkins Dermatology had similar age sex, and race distributions.

Results

Single-plex assays of the biomarkers demonstrated elevated circulating plasma IL-13 (0.13 vs. 0.006 pg/mL, p = 0.0008) and periostin (80.3 vs. 60.2 ng/mL, p = 0.012) in PN compared to controls. IL-4 (0.11 vs. 0.02 pg/mL, p = 0.30) and IL-5 (0.75 vs. 0.40 pg/mL, p = 0.10) were not significantly elevated, while IgE approached significance (1202.0 vs. 432.7 ng/mL, p = 0.08). Clustering of PN and control patients together revealed two clusters. Cluster 1 (n = 36) consisted of 18 PN patients and 18 controls. Cluster 2 (n = 11) consisted entirely of PN patients (p < 0.01). Cluster 2 had higher levels of IL-13 (0.33 vs. 0.008 pg/mL, p = 0.0001) and IL-5 (1.22 vs. 0.43 pg/mL, p = 0.03) compared to cluster 1.

Conclusion and relevance

This study demonstrates elevation of IL-13 and periostin in the blood of PN patients, with distinct clusters with varying degrees of type 2 inflammation. Given this heterogeneity, future precision medicine approaches should be explored in the management of PN.

Dermatologic Disease-Directed Targeted Therapy (D3T2): The Application of Biomarker-Based Precision Medicine for the Personalized Treatment of Skin Conditions-Precision Dermatology

Precision dermatology uses individualized dermatologic disease-directed targeted therapy (D³T²) for the management of dermatoses and for the evaluation and therapy of cutaneous malignancies. Personalized/precision strategies are based on biomarkers that are most frequently derived from tissue transcriptomic expression or genomic sequencing or from circulating cytokines. For instance, the pathologic diagnosis of a pigmented lesion and determining the prognosis of a malignant melanocytic neoplasm can be enhanced by genomic/transcriptomic analysis. In addition to biopsy, innovative techniques have been developed for obtaining transcriptomes in skin conditions; as an example, patches can be applied to a psoriasis plaque for a few minutes to capture the epidermis/upper dermis transcriptome. Atopic dermatitis and prurigo nodularis may also be candidate conditions for precision dermatology. Precision dermatology has a role in managing melanoma and nonmelanoma skin cancers and rare cutaneous tumors-such as perivascular epithelioid cell tumor (PEComa)-that can originate in or metastasize to the skin. For instance, advanced/metastatic basal cell carcinomas can be treated with Hedgehog inhibitors (vismodegib and sonidegib) targeting the smoothened (SMO) or patched 1 (PTCH1) gene alterations that are a hallmark of these cancers and activate the Hedgehog pathway. Advanced/metastatic basal and cutaneous squamous cell cancers often have a high tumor mutational burden (which predicts immunotherapy response); immune checkpoint blockade with cemiplimab, a programmed cell death protein 1 (PD1) inhibitor, is now approved for these malignancies. Gene expression profiling of primary cutaneous squamous cell carcinoma can identify those individuals at high risk for subsequent metastases. In the realm of rare neoplasms, PEComas-which can originate in the skin, albeit uncommonly-have tuberous sclerosis complex 1 (TSC1)/tuberous sclerosis complex 2 (TSC2) gene alterations, which activate mammalian target of rapamycin (mTOR) signaling, and can be suppressed by nab-sirolimus, now approved for this condition. In summary, precision dermatologic techniques/strategies are an important emerging approach for evaluation and management of skin disorders and cutaneous neoplasms, and may serve as a paradigm for the application of precision medicine beyond dermatology.

Critical Players and Therapeutic Targets in Chronic Itch

Chronic itch is one of the most prominent clinical characteristics of diverse systematic diseases. It is a devastating sensation in pathological diseases. Despite its importance, there are no FDA-labelled drugs specifically geared toward chronic itch. The associated complex pathogenesis and diverse causes escalate chronic itch to being one of the top challenges in healthcare. Humanized antibodies against IL-13, IL-4, and IL-31 proved effective in treatment of itch-associated atopic dermatitis but remain to be validated in chronic itch. There are still no satisfactory anti-itch therapeutics available toward itch-related neuropeptides including GRP, BNP, SST, CGRP, and SP. The newly identified potential itch targets including OSM, NMB, glutamate, periostin, and Serpin E1 have opened new avenues for therapeutic development. Proof-of-principle studies have been successfully performed on antagonists against these proteins and their receptors in itch treatment in animal models. Their translational interventions in humans need to be evaluated. It is of great importance to summarize and compare the newly emerging knowledge on chronic itch and its pathways to promote the development of novel anti-itch therapeutics. The goal of this review is to analyze the different physiologies and pathophysiologies of itch mediators, whilst assessing their suitability as new targets and discussing future therapeutic development.