HSP90 inhibitor RGRN-305 for oral treatment of plaque type psoriasis: efficacy, safety and biomarker results in an open-label proof-of-concept study

Advances in the structures, mechanisms and targeting of molecular chaperones

Molecular chaperones, a class of complex client regulatory systems, play significant roles in the prevention of protein misfolding and abnormal aggregation, the modulation of protein homeostasis, and the protection of cells from damage under constantly changing environmental conditions. As the understanding of the biological mechanisms of molecular chaperones has increased, their link with the occurrence and progression of disease has suggested that these proteins are promising targets for therapeutic intervention, drawing intensive interest. Here, we review recent advances in determining the structures of molecular chaperones and heat shock protein 90 (HSP90) chaperone system complexes. We also describe the features of molecular chaperones and shed light on the complicated regulatory mechanism that operates through interactions with various co-chaperones in molecular chaperone cycles. In addition, how molecular chaperones affect diseases by regulating pathogenic proteins has been thoroughly analyzed. Furthermore, we focus on molecular chaperones to systematically discuss recent clinical advances and various drug design strategies in the preclinical stage. Recent studies have identified a variety of novel regulatory strategies targeting molecular chaperone systems with compounds that act through different mechanisms from those of traditional inhibitors. Therefore, as more novel design strategies are developed, targeting molecular chaperones will significantly contribute to the discovery of new potential drugs.

An overview of small-molecule agents for the treatment of psoriasis

Psoriasis is a prevalent, chronic inflammatory disease characterized by abnormal skin plaques. To date, physical therapy, topical therapy, systemic therapy and biologic drugs are the most commonly employed strategies for treating psoriasis. Recently, many agents have advanced to clinical trials, and some anti-psoriasis drugs have been approved, including antibody drugs and small-molecule drugs. Many antibody drugs targeting cytokines and receptors, such as interleukin (IL-17 and IL-23) and tumor necrosis factor-α (TNF-α), have been approved for the treatment of psoriasis. And numerous small-molecule agents have displayed promising activities in the treatment of psoriasis. The targets of anti-psoriasis drugs encompass phosphodiesterase IV (PDE4), Janus kinase (JAK), tyrosine kinase (TYK), retinoic acid-related orphan receptors (ROR), vitamin D receptor (VDR), Interleukin (IL), Aryl hydrocarbon receptor (AhR), Interleukin-1 receptor-associated kinase 4 (IRAK), chemoattractant-like receptor 1 (ChemR23), Sphingosine-1-phosphate receptor (S1P), A3 adenosine receptor (A3AR), Heat shock protein 90 (HSP90), The Rho-associated protein kinases (ROCK), The bromodomain and extra-terminal domain (BET), FMS-like tyrosine kinase 3 (FLT3), Tumor Necrosis Factor α Converting Enzyme (TACE), Toll-like receptors (TLR), NF-κB inducing kinase (NIK), DNA topoisomerase I (Topo I), among others. Herein, this review mainly recapitulates the advancements in the structure and enzyme activity of small-molecule anti-psoriasis agents over the last ten years, and their binding modes were also explored. Hopefully, this review will facilitate the development of novel small-molecule agents as potential anti-psoriasis drugs.

The Differential Roles of HSP90 Isoforms in Skin Inflammation: Anti-Inflammatory Potential of TRAP1 Inhibition

HSP90, a molecular chaperone, has been identified as a drug target in inflammatory skin diseases. However, 4 different HSP90 isoforms (HSP90α, HSP90β, GRP94, and TRAP1) exist. Therefore, this study aimed to evaluate the functional role of the HSP90 isoforms in skin inflammation. Selective knockdown of the HSP90 isoforms revealed different inflammatory effects in stimulated keratinocytes. TRAP1 knockdown significantly downregulated the expression of the measured inflammatory genes (IL1B, IL6, IL17C, IL23A, IL19, IL36G, CXCL8, CCL5, CCL17, CCL20). Selective and combined knockdown of HSP90α and HSP90β showed a trend toward increased inflammatory activity. Selective GRP94 knockdown and combined knockdown of the organelle-specific isoforms (GRP94 + TRAP1) or all 4 isoforms resulted in inconsistent effects. In addition, a selective TRAP1 inhibitor (gamitrinib) suppressed the inflammatory gene expression in keratinocytes and fibroblasts (IL17C, IL23A, IL36G) and in hidradenitis suppurativa skin cultured ex vivo (IL1B, IL6, CXCL8, IL17A, IL36G). In conclusion, selective and simultaneous knockdown of the HSP90 isoforms mediated different inflammatory effects, revealing that the HSP90 isoforms have distinct roles in skin inflammation. In addition, we discovered that inhibition of TRAP1 exerted consistent anti-inflammatory effects, suggesting that TRAP1 inhibitors may represent a topical therapeutic strategy for inflammatory skin diseases.

Innovative Approaches to Psoriasis: Small Molecules Targeting Key Signaling Pathways

BACKGROUND

Psoriasis (Pso) is a chronic, immune-mediated dermatological condition characterized by dysregulated inflammatory responses and the hyperproliferation of keratinocytes. Biologics, which target specific cytokines such as IL-17 and IL-23, have revolutionized the management by addressing key drivers of its pathophysiology. Despite their efficacy, biologics are not without limitations, including the need for intermittent administration and ongoing monitoring. In contrast, small molecules offer a promising alternative by selectively inhibiting key signaling pathways that modulate pro-inflammatory cytokines involved in the inflammatory cascade.

METHODS AND RESULTS

This review suggests a new therapeutic strategy for Pso treatment, emphasizing the intricate relationships between small molecules and important signaling pathways involved in the pathophysiology of skin conditions. Improving treatment outcomes and reducing the side effects associated with conventional medicines, this review aims to better understand how tailored small-molecule inhibitors might efficiently control these pathways. This creative approach promotes the creation of individualized treatment plans that can greatly enhance the quality of life of patients with Psoby utilizing the knowledge gathered from recent developments in signaling pathway research.

CONCLUSION

This review delves into the molecular mechanisms underlying Pso and explores how small molecules can be harnessed to enhance treatment outcomes, presenting a new paradigm for managing this chronic skin disorder.

HSP90 Complex From OLP Lesion Induces T-Cell Polarization via Activation of Dendritic Cells

OBJECTIVES

To investigate the effects of the heat shock protein 90 (HSP90) complex from oral lichen planus (OLP) lesion tissues on dendritic cell (DC) activation and the polarization of naïve T cells.

METHODS

Expression of HSP90 in OLP lesions and healthy control (HC) mucosa was evaluated by single-cell RNA sequence, IHC, qRT-PCR, and immunoblotting. HSP90 complex was extracted by immunoprecipitation from oral mucosa as the agonist of DCs. Expression of IFN-α and MHC was detected by flow cytometry. After cocultured with pre-stimulated DCs, polarization of naïve T cells was investigated by cytokine analysis.

RESULTS

HSP90 was significantly higher in the lamina propria of OLP lesion and closely related to lymphocyte infiltration. HSP90 complex of OLP lesion activated DCs via TLR9 and increased their IFN-α secretion and MHC II expression. Pre-stimulated DCs increased the proportion of Th17 cells.

CONCLUSIONS

HSP90 complex isolated from OLP lesion activated TLR9/IFN-α of DCs and further promoted the polarization of naïve T cells toward Th17 immunity.

The heat shock protein 90 inhibitor RGRN-305 attenuates SARS-CoV-2 spike protein-induced inflammation in vitro but lacks effectiveness as COVID-19 treatment in mice

The inhibition of heat shock protein 90 (HSP90), a molecular chaperone, has been proposed to be a potential novel treatment strategy for Coronavirus disease 2019 (COVID-19). In contrast to other studies, our data demonstrated that RGRN-305, a HSP90 inhibitor, exacerbated the cytopathic effect and did not reduce the viral shedding in VeroE6-hTMPRSS2 cells infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Likewise in a murine model of SARS-CoV-2, transgenic mice treated orally with RGRN-305 exhibited reduced survival by the end of the experiment (day 12) as 14% (1/7) survived compared to 63% (5/8) of those treated with drug-vehicle. Animal weight was not reduced by the RGRN-305 treatment. Interestingly, we demonstrated that inhibition of HSP90 by RGRN-305 significantly dampened the inflammatory response induced by SARS-CoV-2 spike protein in human macrophage-like cells (U937) and human lung epithelial cells (A549). Measured by quantitative real-time PCR, the mRNA expression of the proinflammatory cytokines TNF, IL1B and IL6 were significantly reduced. Together, these data suggest that HSP90 inhibition by RGRN-305 exacerbates the SARS-CoV-2 infection in vitro and reduces the survival of mice infected with SARS-CoV-2, but exhibits strong anti-inflammatory properties. This data shows that while RGRN-305 may be helpful in a 'cytokine storm', it has no beneficial impact on viral replication or survival in animals as a monotherapy. Further animal studies with HSP90 inhibitors in combination with an anti-viral drug may provide additional insights into its utility in viral infections and whether HSP90 inhibition may continue to be a potential treatment strategy for COVID-19 disease.

Research hotspots and trends in biological agents for psoriasis: Visualization and bibliometric analysis

Psoriasis is a global health concern, and biological therapies have proven to be highly effective in treating psoriatic patients in many countries. We performed a bibliometric analysis of current research on biological agents for the treatments of psoriasis, investigating research patterns and public interest in this area. We conducted a thorough review of articles on biological agents for psoriasis in the Web of Science Core Collection spanning from 2000 to 2022. Our study involved examining the distribution of these articles based on publication year, affiliations, countries, authors, and journals. To visualize this data effectively, we employed bibliometric tools like CiteSpace and the R package bibliometrix. Our analysis encompassed 8,047 publications. The number of papers published sharply increased from 2009, either reaching its peak in 2022 or not yet reaching it. The United States (n = 2,292), Kristian Reich (n = 166), and British Journal of Dermatology (n = 368) emerged as the top countries, author, and journal, respectively, in terms of publication productivity. The burst references predominantly focused on evaluating the safety and efficacy of biological treatments. The keyword citation network identified 11 clusters, with research themes revolving around "double blind", "efficacy", "therapy", "safety", and "psoriatic arthritis" were the research focuses. Additionally, potential future research areas such as "multicenter," "drug survival," and "severity" were emphasized. This study sheds light on the evolving research landscape and public interest in biological agents for psoriasis. The results suggest rapid expansion in this field, with the United States at the forefront. Enhanced international collaboration is recommended, and forthcoming research endeavors may concentrate on predicting treatment outcomes and adverse effects. Researching new biological agents, broadening the indications for biological agent treatment, and creating personalized treatment plans may pave the way for further research.

New and Emerging Oral/Topical Small-Molecule Treatments for Psoriasis

The introduction of biologic therapies has led to dramatic improvements in the management of moderate-to-severe psoriasis. Even though the efficacy and safety of the newer biologic agents are difficult to match, oral administration is considered an important advantage by many patients. Current research is focused on the development of oral therapies with improved efficacy and safety compared with available alternatives, as exemplified by deucravacitinib, the first oral allosteric Tyk2 inhibitor approved for the treatment of moderate to severe psoriasis in adults. Recent advances in our knowledge of psoriasis pathogenesis have also led to the development of targeted topical molecules, mostly focused on intracellular signaling pathways such as AhR, PDE-4, and Jak-STAT. Tapinarof (an AhR modulator) and roflumilast (a PDE-4 inhibitor) have exhibited favorable efficacy and safety outcomes and have been approved by the FDA for the topical treatment of plaque psoriasis. This revision focuses on the most recent oral and topical therapies available for psoriasis, especially those that are currently under evaluation and development for the treatment of psoriasis.

HSP90, a Common Therapeutic Target for Suppressing Skin Injury Caused by Exposure to Chemically Diverse Classes of Blistering Agents

Vesicants such as arsenicals and mustards produce highly painful cutaneous inflammatory and blistering responses, hence developed as chemical weapons during World War I/II. Here, using lewisite and sulfur mustard surrogates, namely phenylarsine oxide (PAO) and 2-chloroethyl ethyl sulfide (CEES), respectively, we defined a common underlying mechanism of toxic action by these two distinct classes of vesicants. Murine skin exposure to these chemicals causes tissue destruction characterized by increase in skin bifold thickness, Draize score, infiltration of inflammatory cells, and apoptosis of epidermal and dermal cells. RNA sequencing analysis identified ∼346 inflammatory genes that were commonly altered by both PAO and CEES, along with the identification of cytokine signaling activation as the top canonical pathway. Activation of several proinflammatory genes and pathways is associated with phosphorylation-dependent activation of heat shock protein 90α (p-HSP90α). Topical treatment with known HSP90 inhibitors SNX-5422 and IPI-504 post PAO or CEES skin challenge significantly attenuated skin damage including reduction in overall skin injury and clinical scores. In addition, highly upregulated inflammatory genes Saa3, Cxcl1, Ccl7, IL-6, Nlrp3, Csf3, Chil3, etc. by both PAO and CEES were significantly diminished by treatment with HSP90 inhibitors. These drugs not only reduced PAO- or CEES-induced p-HSP90α expression but also its client proteins NLRP3 and pP38 and the expression of their target inflammatory genes. Our data confirm a critical role of HSP90 as a shared underlying molecular target of toxicity by these two distinct vesicants and provide an effective and novel medical countermeasure to suppress vesicant-induced skin injury. SIGNIFICANCE STATEMENT: Development of effective and novel mechanism-based antidotes that can simultaneously block cutaneous toxic manifestations of distinct vesicants is important and urgently needed. Due to difficulties in determining the exact nature of onsite chemical exposure, a potent drug that can suppress widespread cutaneous damage may find great utility. Thus, this study identified HSP90 as a common molecular regulator of cutaneous inflammation and injury by two distinct warfare vesicants, arsenicals and mustards, and HSP90 inhibitors afford significant protection against skin damage.

Heat shock protein 90 inhibition attenuates inflammation in models of atopic dermatitis: a novel mechanism of action

Background

Heat shock protein 90 (HSP90) is an important chaperone supporting the function of many proinflammatory client proteins. Recent studies indicate HSP90 inhibition may be a novel mechanism of action for inflammatory skin diseases; however, this has not been explored in atopic dermatitis (AD).

Objectives

Our study aimed to investigate HSP90 as a novel target to treat AD.

Methods

Experimental models of AD were used including primary human keratinocytes stimulated with cytokines (TNF/IFNγ or TNF/IL-4) and a mouse model established by MC903 applications.

Results

In primary human keratinocytes using RT-qPCR, the HSP90 inhibitor RGRN-305 strongly suppressed the gene expression of Th1- (TNF, IL1B, IL6) and Th2-associated (CCL17, CCL22, TSLP) cytokines and chemokines related to AD. We next demonstrated that topical and oral RGRN-305 robustly suppressed MC903-induced AD-like inflammation in mice by reducing clinical signs of dermatitis (oedema and erythema) and immune cell infiltration into the skin (T cells, neutrophils, mast cells). Interestingly, topical RGRN-305 exhibited similar or slightly inferior efficacy but less weight loss compared with topical dexamethasone. Furthermore, RNA sequencing of skin biopsies revealed that RGRN-305 attenuated MC903-induced transcriptome alterations, suppressing genes implicated in inflammation including AD-associated cytokines (Il1b, Il4, Il6, Il13), which was confirmed by RT-qPCR. Lastly, we discovered using Western blot that RGRN-305 disrupted JAK-STAT signaling by suppressing the activity of STAT3 and STAT6 in primary human keratinocytes, which was consistent with enrichment analyses from the mouse model.

Conclusion

HSP90 inhibition by RGRN-305 robustly suppressed inflammation in experimental models mimicking AD, proving that HSP90 inhibition may be a novel mechanism of action in treating AD.

Recent developments of HSP90 inhibitors: an updated patent review (2020-present)

INTRODUCTION

The 90-kDa heat shock protein (HSP90) functions as a molecular chaperone, it assumes a significant role in diseases such as cancer, inflammation, neurodegeneration, and infection. Therefore, the research and development of HSP90 inhibitors have garnered considerable attention.

AREAS COVERED

The primary references source for this review is patents obtained from SciFinder, encompassing patents on HSP90 inhibitors from the period of 2020 to 2023.This review includes a thorough analysis of their structural attributes, pharmacological properties, and potential clinical utilities.

EXPERT OPINION

In the past few years, HSP90 inhibitors targeting ATP binding pocket are still predominate and one of them has been launched, besides, novel drug design strategies like C-terminal targeting, isoform selective inhibiting and bifunctional molecules are booming, aiming to improve the efficacy and safety. With expanded drug types and applications, HSP90 inhibitors may gradually becoming a sagacious option for treating various diseases.

Transcriptomic Analysis of Hidradenitis Suppurativa: A Unique Molecular Signature with Broad Immune Activation

Hidradenitis suppurativa is a chronic inflammatory skin disease with limited treatment options. The poorly understood pathogenesis hinders the development of effective treatments; therefore, a pressing need exists to further elucidate the molecular mechanisms in hidradenitis suppurativa. This study investigated the underlying inflammatory pathways and cell types in hidradenitis suppurativa using transcriptomic approaches with RNA sequencing of lesional and non-lesional skin biopsies from hidradenitis suppurativa, which was jointly analyzed with previously published transcriptomic data from atopic dermatitis and psoriasis patients. The differential expression and pathway enrichment analyses demonstrated the activation of multiple inflammatory processes, including the innate and adaptive immune systems, implicated in the hidradenitis suppurativa pathogenesis. In agreement, hidradenitis suppurativa exhibited a unique and heterogeneous cell type signature involving lymphoid and myeloid cells such as B cells and macrophages. Furthermore, hidradenitis suppurativa displayed increased expression of TH1/2/17 signatures with no predominant TH signatures unlike psoriasis (TH1/17) and atopic dermatitis (TH2). In summary, our study provides molecular insights into the pathomechanisms in hidradenitis suppurativa, revealing a strong and widespread immune activation, which may benefit from treatment strategies offering a broad immunomodulation of various key inflammatory pathways. Our data not only corroborate previously reported findings but also enhance our understanding of the immune dysregulation in hidradenitis suppurativa, uncovering novel and potential therapeutic targets.

Heat shock protein 90 (Hsp90) inhibitor STA-9090 (Ganetespib) ameliorates inflammation in a mouse model of atopic dermatitis

Molecular chaperones belonging to the heat shock protein 90 (Hsp90) family are implicated in inflammatory processes and described as potential novel therapeutic targets in autoimmune/inflammatory skin diseases. While the pathological role of circulating Hsp90 has been recently proposed in patients with atopic dermatitis (AD), a chronic inflammatory skin disease characterized by intense itching and recurrent skin lesions, studies aimed at investigating the role of Hsp90 as a potential target of AD therapy have not yet been conducted. Here, the effects of the Hsp90 blocker STA-9090 (Ganetespib) applied systemically or topically were determined in an experimental mouse model of dinitrochlorobenzene (DNCB)-induced AD. Intraperitoneal administration of STA-9090 ameliorated clinical disease severity, histological epidermal thickness, and dermal leukocyte infiltration in AD mice which was associated with reducing the scratching behavior in DNCB-treated animals. Additionally, topically applied STA-9090 led to lowered disease activity in AD mice, reduced serum levels of IgE, and up-regulated filaggrin expression in lesional skin samples. Our observations suggest that Hsp90 may be a promising therapeutic target in atopic dermatitis and potentially other inflammatory or autoimmune dermatoses.

Periostin C-Terminal Is Intrinsically Disordered and Interacts with 143 Proteins in an In Vitro Epidermal Model of Atopic Dermatitis

Human periostin is a 78-91 kDa matricellular protein implicated in extracellular matrix remodeling, tumor development, metastasis, and inflammatory diseases like atopic dermatitis, psoriasis, and asthma. The protein consists of six domains, including an N-terminal Cys-rich CROPT domain, four fasciclin-1 domains, and a C-terminal domain. The exons encoding the C-terminal domain may be alternatively spliced by shuffling four exons, generating ten variants of unknown function. Here, we investigate the structure and interactome of the full-length variant of the C-terminal domain with no exons spliced out. The structural analysis showed that the C-terminal domain lacked a tertiary structure and was intrinsically disordered. In addition, we show that the motif responsible for heparin-binding is in the conserved very C-terminal part of periostin. Pull-down confirmed three known interaction partners and identified an additional 140 proteins, among which nine previously have been implicated in atopic dermatitis. Based on our findings, we suggest that the C-terminal domain of periostin facilitates interactions between connective tissue components in concert with the four fasciclin domains.

A Route for Investigating Psoriasis: From the Perspective of the Pathological Mechanisms and Therapeutic Strategies of Cancer

Psoriasis is an incurable skin disease that develops in about two-thirds of patients before the age of 40 and requires lifelong treatment; its pathological mechanisms have not been fully elucidated. The core pathological process of psoriasis is epidermal thickening caused by the excessive proliferation of epidermal keratinocytes, which is similar to the key feature of cancer; the malignant proliferation of cancer cells causes tumor enlargement, suggesting that there is a certain degree of commonality between psoriasis and cancer. This article reviews the pathological mechanisms that are common to psoriasis and cancer, including the interaction between cell proliferation and an abnormal immune microenvironment, metabolic reprogramming, and epigenetic reprogramming. In addition, there are common therapeutic agents and drug targets between psoriasis and cancer. Thus, psoriasis and cancer share a common pathological mechanisms-drug targets-therapeutic agents framework. On this basis, it is proposed that investigating psoriasis from a cancer perspective is beneficial to enriching the research strategies related to psoriasis.

An Unexpected Finding: Treatment History Associated with the Quality of Life in Chinese Patients with Port-Wine Stains

Background

Port-wine stains (PWS) are predominantly located on the face and neck. Hence, PWS affect not only aesthetic appearance but may also cause psychological distress. However, very few studies have researched on the quality of life (QoL) in Chinese patients with PWS.

Aim

To evaluate QoL in patients with PWS.

Methods and Materials

Skindex-29 and Dermatology Life Quality Index (DLQI) were used to investigate the QoL of the patients with PWS and healthy controls.

Results

In total, 198 adults with PWS and 200 healthy controls were included. The scores of symptomatic, emotional and functional dimensions of Skindex-29 in the observational group were significantly higher as compared with the control group (P<0.05). Female gender, lesion location and the treatment history (such as pulsed dye laser or photodynamic therapy) had a negative impact on the scores (emotional and functional dimensions) of the patients with PWS. The median DLQI score was 3 points in the observational group and 0 points in the control group (P<0.05), and QoL of patients who had a history of previous treatments was diminished.

Conclusion

The QoL of patients with PWS is impaired. Patients' QoL is negatively influenced by female gender, lesion location and treatment history. The Skindex-29 scale seems to be more applicable to the study of QoL of patients with PWS.

Emerging Treatments and the Clinical Trial Landscape for Hidradenitis Suppurativa Part I: Topical and Systemic Medical Therapies

Hidradenitis suppurativa (HS) is an oftentimes debilitating condition that presents with painful nodules, abscesses, and sinus tracts. This condition is challenging to treat, in part because the pathogenesis of the condition is incompletely understood but also because there are limited therapeutic options. HS research is undergoing explosive growth with multiple new molecular pathways under study, which will hopefully lead to improved disease control for patients. Part I of this review will provide an overview of the emerging topical and systemic therapies under investigation for HS.

Psoriasis: a focus on upcoming oral formulations

INTRODUCTION

Targeted therapies have greatly improved the quality of life of patients with psoriasis. Despite the extensive list of treatments available, multiple new drugs are being developed, especially oral therapies with potential advantages as regards comfort of administration. However, the efficacy and safety of these new oral therapies need to be improved to match those of novel biologics.

AREAS COVERED

We provide a narrative review of the oral therapies for psoriasis that are currently under development, from Jak inhibitors to oral IL-17 and IL-23 inhibitors, among others. A literature search was performed for articles published from 1 January 2020, to 6 June 2023.

EXPERT OPINION

The approval of deucravacitinib, the first Jak inhibitor for the treatment of moderate-to-severe plaque psoriasis, heralds a bright therapeutic future with multiple new oral formulations. A great number of oral treatments with singular mechanism of action, like A3AR agonists, HSP90 inhibitors, ROCK-2 inhibitors, oral TNF inhibitors, oral IL-23 inhibitors, oral IL-17 inhibitors, PD4 inhibitors (orismilast) and several Tyk2 inhibitors, are currently being evaluated in clinical trials and could be suitable for approval in the future. Growing variation in treatment modes of administration will allow dermatologists to better integrate patient preferences in the therapeutic decision process.

The Current Clinical Trial Landscape for Hidradenitis Suppurativa: A Narrative Review

Hidradenitis suppurativa (HS) is a skin disease resulting from chronic, recurrent inflammation around hair follicles, characterized by proinflammatory cytokines such as IL-1, IL-17, IL-23, and TNF-α. While adalimumab, a TNF-α targeting human IgG monoclonal antibody, is the only approved treatment for HS, there are many other therapies being investigated now targeting other key players in inflammatory pathways such as the cytokines listed above, C5a in the complement pathway, and Janus kinase (JAK). This review discusses current clinical trials for biologics and small molecules, procedures, and wound dressings undergoing study in hidradenitis suppurativa.

Heat shock protein 90 inhibitor RGRN-305 potently attenuates skin inflammation

Introduction

Chronic inflammatory skin diseases may have a profound negative impact on the quality of life. Current treatment options may be inadequate, offering an unsatisfactory response or side effects. Therefore, ongoing efforts exist to identify novel effective and safe treatments. Heat shock protein (HSP) 90 is a chaperone that promotes the activity of a wide range of client proteins including key proinflammatory molecules involved in aberrant inflammation. Recently, a proof-of-concept clinical trial of 13 patients suggested that RGRN-305 (an HSP90 inhibitor) may be an oral treatment for psoriasis. However, HSP90 inhibition may be a novel therapeutic approach extending beyond psoriasis to include multiple immune-mediated inflammatory skin diseases.

Methods

This study aimed to investigate (i) the anti-inflammatory effects and mechanisms of HSP90 inhibition and (ii) the feasibility of topical RGRN-305 administration (new route of administration) in models of inflammation elicited by 12-O-tetradecanoylphorbol-13-acetate (TPA) in primary human keratinocytes and mice (irritative dermatitis murine model).

Results/Discussion

In primary human keratinocytes stimulated with TPA, a Nanostring® nCounter gene expression assay demonstrated that HSP90 inhibition with RGRN-305 suppressed many proinflammatory genes. Furthermore, when measured by quantitative real-time polymerase chain reaction (RT-qPCR), RGRN-305 significantly reduced the gene expression of TNF, IL1B, IL6 and CXCL8. We next demonstrated that topical RGRN-305 application significantly ameliorated TPA-induced skin inflammation in mice. The increase in ear thickness (a marker of inflammation) was significantly reduced (up to 89% inhibition). In accordance, RT-qPCR of the ear tissue demonstrated that RGRN-305 robustly reduced the gene expression of proinflammatory markers (Tnf, Il1b, Il6, Il17A and Defb4). Moreover, RNA sequencing revealed that RGRN-305 mitigated TPA-induced alterations in gene expression and suppressed genes implicated in inflammation. Lastly, we discovered that the anti-inflammatory effects were mediated, at least partly, by suppressing the activity of NF-κB, ERK1/2, p38 MAPK and c-Jun signaling pathways, which are consistent with previous findings in other experimental models beyond skin inflammation. In summary, HSP90 inhibition robustly suppressed TPA-induced inflammation by targeting key proinflammatory cytokines and signaling pathways. Our findings suggest that HSP90 inhibition may be a novel mechanism of action for treating immune-mediated skin disease beyond psoriasis, and it may be a topical treatment option.

Heat shock proteins: Biological functions, pathological roles, and therapeutic opportunities

The heat shock proteins (HSPs) are ubiquitous and conserved protein families in both prokaryotic and eukaryotic organisms, and they maintain cellular proteostasis and protect cells from stresses. HSP protein families are classified based on their molecular weights, mainly including large HSPs, HSP90, HSP70, HSP60, HSP40, and small HSPs. They function as molecular chaperons in cells and work as an integrated network, participating in the folding of newly synthesized polypeptides, refolding metastable proteins, protein complex assembly, dissociating protein aggregate dissociation, and the degradation of misfolded proteins. In addition to their chaperone functions, they also play important roles in cell signaling transduction, cell cycle, and apoptosis regulation. Therefore, malfunction of HSPs is related with many diseases, including cancers, neurodegeneration, and other diseases. In this review, we describe the current understandings about the molecular mechanisms of the major HSP families including HSP90/HSP70/HSP60/HSP110 and small HSPs, how the HSPs keep the protein proteostasis and response to stresses, and we also discuss their roles in diseases and the recent exploration of HSP related therapy and diagnosis to modulate diseases. These research advances offer new prospects of HSPs as potential targets for therapeutic intervention.

Heat Shock Protein 90 (Hsp90) and Hsp70 as Potential Therapeutic Targets in Autoimmune Skin Diseases

Over a hundred different autoimmune diseases have been described to date, which can affect every organ in the body, including the largest one, the skin. In fact, up to one-fifth of the world's population suffers from chronic, noninfectious inflammatory skin diseases, the development of which is significantly influenced by an autoimmune response. One of the hallmarks of autoimmune diseases is the loss of immune tolerance, which leads to the formation of autoreactive lymphocytes or autoantibodies and, consequently, to chronic inflammation and tissue damage. The treatment of autoimmune skin diseases mainly focuses on immunosuppression (using, e.g., corticosteroids) but almost never leads to the development of permanent mechanisms of immune tolerance. In addition, current therapies and their long-term administration may cause serious adverse effects. Hence, safer and more effective therapies that bring sustained balance between pro- and anti-inflammatory responses are still desired. Both intra- and extracellular heat shock proteins (Hsps), specifically well-characterized inducible Hsp90 and Hsp70 chaperones, have been highlighted as therapeutic targets for autoimmune diseases. This review presents preclinical data on the involvement of Hsp90 and Hsp70 in modulating the immune response, specifically in the context of the treatment of selected autoimmune skin diseases with emphasis on autoimmune bullous skin diseases and psoriasis.