Chronic Prurigo: Similar Clinical Profile and Burden Across Clinical Phenotypes

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.

Validation of a scoring algorithm for the clinician-reported outcome tool 'prurigo activity and severity (PAS)' based on clinical studies of dupilumab in adults with prurigo Nodularis

BACKGROUND

Prurigo nodularis (PN) also known as chronic prurigo, is a chronic inflammatory skin disease characterized by intensely itchy nodules/lesions which occur due to intensive scratching. PN management is, in part, based on clinician evaluations of PN lesions, which can be supported by clinician-reported outcomes (ClinRO) such as the Prurigo Activity and Severity (PAS) instrument. A 5-item version of PAS was included in recent phase-3 dupilumab PN trials (PRIME [NCT04183335]/PRIME2 [NCT04202679]). The PAS score was derived using the unweighted sum of 3-items of the 5-item PAS (range, 0-11; higher score indicates worse activity and severity): Item 2 (number of lesions), Item 5a (percentage of lesions with excoriations/crusts) and Item 5b (percentage of healed lesions) for use in clinical practice and for communication of treatment benefit to physicians.

OBJECTIVES

To evaluate the measurement properties of PAS score and derive within-patient (responder definition) and between-group improvement thresholds for interpreting changes in PAS score in patients with PN.

METHODS

The data source was the pooled treatment group, intention-to-treat (ITT) data from the phase-3 PRIME (NCT04183335) and PRIME2 (NCT04202679) studies evaluating the efficacy of dupilumab in adult patients with PN with ≥20 nodules and severe itch uncontrolled with topical therapies. PAS score reliability, validity and sensitivity to change were evaluated, and anchor- and distribution-based methods were applied to derive meaningful change thresholds.

RESULTS

The pooled ITT population included 311 patients (mean age 49.5 years, 65.3% female). Adequate to good psychometric properties were demonstrated for PAS score. The within-patient meaningful improvement threshold was estimated as 3.0 points (absolute change) and 37% (per cent change). A 1.7-point (absolute change) and 20% (per cent change) improvement were estimated to reflect a between-group meaningful change in PAS score.

CONCLUSIONS

PAS score is a simple, clinically relevant indicator of PN lesion activity and severity supported by suitable psychometric performance.

Classification of psychodermatological disorders: Proposal of a new international classification

INTRODUCTION

Several classifications of psychodermatology disorders have been proposed, with most of them based on two to four main disorder category groups. However, there is, to date, no classification that has resulted from a consensus established by psychodermatology experts. The DSM-5-TR (Diagnostic and statistical manual of mental disorders (5th ed.), Text Revision) and the ICD-11 (International classification of diseases (11th revision)) also do not provide a systematized approach of psychodermatology disorders. Taking into consideration that classifications are a key pillar for a comprehensive approach to the pathologies of each branch of medicine, the proposal of a classification in psychodermatology appeared as a central need for the recognition of psychodermatological disorders, in an attempt to improve their recognition and, in that sense, to find a common language for the development of this subspecialty that crosses dermatology and psychiatry.

METHODS

Previously published classifications in psychodermatology were critically reviewed and discussed by expert opinion from an international multidisciplinary panel of 16 experts in psychodermatology and a new classification system is proposed, considering classical concepts in general dermatology and psychopathology.

RESULTS

Two main categories of disorders are presented (a main group related to primary mental health disorders and another main group related to primary skin disorders), which are subsequently subdivided into subgroups considering pathophysiological and phenomenological similarities, including key aspects of dermatological examination, namely the presence of visible skin lesions (primary and secondary skin lesions) and psychopathological correlates.

CONCLUSION

This new classification aims to unify previous classifications, systematize the disorders that belong to psychodermatology and highlight their tenuous boundaries, to improve their management. It has been built and approved by the Psychodermatology Task Force of the European Academy of Dermatology and Venereology (EADV), the European Society for Dermatology and Psychiatry (ESDaP) and the Association for Psychoneurocutaneous Medicine of North America (APMNA).

Mast cell silencing: A novel therapeutic approach for urticaria and other mast cell-mediated diseases

Chronic urticaria (CU) is a mast cell (MC)-dependent disease with limited therapeutic options. Current management strategies are directed at inhibiting IgE-mediated activation of MCs and antagonizing effects of released mediators. Due to the complexity and heterogeneity of CU and other MC diseases and mechanisms of MC activation-including multiple activating receptors and ligands, diverse signaling pathways, and a menagerie of mediators-strategies of MC depletion or MC silencing (i.e., inhibition of MC activation via binding of inhibitory receptors) have been developed to overcome limitations of singularly targeted agents. MC silencers, such as agonist monoclonal antibodies that engage inhibitory receptors (e.g., sialic acid-binding immunoglobulin-like lectin8 -[Siglec-8] [lirentelimab/AK002], Siglec-6 [AK006], and CD200R [LY3454738]), have reached preclinical and clinical stages of development. In this review, we (1) describe the role of MCs in the pathogenesis of CU, highlighting similarities with other MC diseases in disease mechanisms and response to treatment; (2) explore current therapeutic strategies, categorized by nonspecific immunosuppression, targeted inhibition of MC activation or mediators, and targeted modulation of MC activity; and (3) introduce the concept of MC silencing as an emerging strategy that could selectively block activation of MCs without eliciting or exacerbating on- or off-target, immunosuppressive adverse effects.

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.

Nemolizumab efficacy in prurigo nodularis: onset of action on itch and sleep disturbances

BACKGROUND

Patients with prurigo nodularis (PN) have multiple itchy nodules, impaired quality of life and sleep deprivation. Prurigo nodularis patients have a high burden of disease, primarily due to the intensity of the itch. It is reasonable to expect that rapid relief of itch - and associated improvement of sleep - are highly valued clinical outcomes for patients. Nemolizumab is an IL-31A-receptor inhibitor that modulates the neuroimmune response with reported positive efficacy and safety data in a phase 2 study of PN.

OBJECTIVES

To evaluate the onset of action of nemolizumab on itch and sleep disturbances.

METHODS

Post hoc analysis of a phase 2 trial of nemolizumab 0.5 mg/kg SC vs. placebo in patients (n = 70) with moderate-to-severe PN (≥20 nodules) and severe pruritus (NRS ≥ 7). Time to significant reduction was assessed for peak pruritus (PP) and sleep disturbance (SD) using numerical rating scales (NRS), also assessed was scratching time during sleep.

RESULTS

Nemolizumab significantly reduced itch vs. placebo within 48 h (PP NRS -19.5% vs. -5.8%, respectively, P = 0.014). Significant difference between nemolizumab and placebo in reducing itch by ≥4 on PP NRS was achieved at Day 3 (23.5% vs. 0%, P < 0.001). A significant difference in SD NRS was reported by Day 4 (-24.0% vs. -4.3% placebo, P = 0.012). In addition, there was a separation between groups in SD responders (decrease of ≥4 points) in favour of nemolizumab by Day 2 (8.8% vs. 0%, P = 0.037). Sleep continued improving through Week 4, when there was a -56.0% reduction in SD NRS vs. -22.9% placebo (P < 0.001). Actigraphy data showed improvement in scratch/sleep duration for nemolizumab vs. placebo, respectively, by Week 1 (-32.15 vs. +28.15 min/h, P = 0.001).

CONCLUSION

Nemolizumab has a rapid and robust onset of action in PN with itch reduction and improvement of sleep within 48 h.

Unmet Medical Needs in Chronic, Non-communicable Inflammatory Skin Diseases

An estimated 20-25% of the population is affected by chronic, non-communicable inflammatory skin diseases. Chronic skin inflammation has many causes. Among the most frequent chronic inflammatory skin diseases are atopic dermatitis, psoriasis, urticaria, lichen planus, and hidradenitis suppurativa, driven by a complex interplay of genetics and environmental factors. Autoimmunity is another important cause of chronic skin inflammation. The autoimmune response may be mainly T cell driven, such as in alopecia areata or vitiligo, or B cell driven in chronic spontaneous urticaria, pemphigus and pemphigoid diseases. Rare causes of chronic skin inflammation are autoinflammatory diseases, or rheumatic diseases, such as cutaneous lupus erythematosus or dermatomyositis. Whilst we have seen a significant improvement in diagnosis and treatment, several challenges remain. Especially for rarer causes of chronic skin inflammation, early diagnosis is often missed because of low awareness and lack of diagnostics. Systemic immunosuppression is the treatment of choice for almost all of these diseases. Adverse events due to immunosuppression, insufficient therapeutic responses and relapses remain a challenge. For atopic dermatitis and psoriasis, a broad spectrum of innovative treatments has been developed. However, treatment responses cannot be predicted so far. Hence, development of (bio)markers allowing selection of specific medications for individual patients is needed. Given the encouraging developments during the past years, we envision that many of these challenges in the diagnosis and treatment of chronic inflammatory skin diseases will be thoroughly addressed in the future.

The emerging role of the neuroimmune cytokine interleukin-31 in chronic inflammatory skin diseases

Chronic inflammatory skin diseases pose significant challenges for both patients and clinicians worldwide. Atopic dermatitis (AD), the most common of these diseases, affects up to 8% of the adult population depending on geographic location and demographic group, while prurigo nodularis (PN) is a less common disease that causes significant burden. In these inflammatory skin conditions, pruritus is a cardinal symptom. Interleukin 31 (IL-31), described as a neuroimmune modulator, has been shown to have a prominent role in both inflammation and itch. IL-31 acts through a receptor complex consisting of IL-31 receptor α (IL-31RA) and oncostatin M receptor β (OSMRβ). IL-31 is produced by a variety of cells, including type 2 helper T cells, and IL-31 signaling can activate three important pathways: JAK/STAT, P13K/AKT, and ERK/MAPK. IL-31 is elevated in AD and PN, and is thought to induce chemokine genes CCL1, CCL17, and CCL22. The chemokines recruit T cells to affected skin, where more IL-31 is secreted. The IL-31 receptor complex is also abundant in dorsal root ganglia in human tissue, home of primary sensory neurons and the distal source of "itch sensations". IL-31 and its receptor complex have an important role in chronic inflammatory diseases, including AD and PN, and blocking the IL-31/IL-31RA signaling may represent an important new therapeutic approach for these diseases, which continue to have significant unmet medical needs.