JAK inhibitors: treatment efficacy and safety profile in patients with psoriasis

Expression of the JAK/STAT Signaling Pathway in Bullous Pemphigoid and Dermatitis Herpetiformis

A family of eleven proteins comprises the Janus kinases (JAK) and signal transducers and activators of transcription (STAT) signaling pathway, which enables transduction of signal from cytokine receptor to the nucleus and activation of transcription of target genes. Irregular functioning of the cascade may contribute to pathogenesis of autoimmune diseases; however, there are no reports concerning autoimmune bullous diseases yet to be published. The aim of this study was to evaluate the expression of proteins constituting the JAK/STAT signaling pathway in skin lesions and perilesional area in dermatitis herpetiformis (DH) and bullous pemphigoid (BP), as well as in the control group. Skin biopsies were collected from 21 DH patients, from 20 BP patients, and from 10 healthy volunteers. The localization and expression of selected STAT and JAK proteins were examined by immunohistochemistry and immunoblotting. We found significantly higher expression of JAK/STAT proteins in skin lesions in patients with BP and DH, in comparison to perilesional skin and the control group, which may be related to proinflammatory cytokine network and induction of inflammatory infiltrate in tissues. Our findings suggest that differences in the JAK and STAT expression may be related to distinct cytokines activating them and mediating neutrophilic and/or eosinophilic infiltrate.

Dose/Exposure-Response Modeling to Support Dosing Recommendation for Phase III Development of Baricitinib in Patients with Rheumatoid Arthritis

Baricitinib is an oral inhibitor of Janus kinases (JAKs), selective for JAK1 and 2. It demonstrated dose‐dependent efficacy in patients with moderate‐to‐severe rheumatoid arthritis (RA) in a phase IIb study up to 24 weeks. Population pharmacokinetic/pharmacodynamic (PopPK/PD) models were developed to characterize concentration‐time profiles and dose/exposure‐response (D/E‐R) relationships for the key efficacy (proportion of patients achieving American College of Rheumatology 20%, 50%, or 70% response rate) and safety endpoints (incidence of anemia) for the phase IIb study. The modeling suggested that 4 mg q.d. was likely to offer the optimum risk/benefit balance, whereas 2 mg q.d. had the potential for adequate efficacy. In addition, at the same total daily dose, a twice‐daily regimen is not expected to provide an advantage over q.d. dosing for the efficacy or safety endpoints. The model‐based simulations formed the rationale for key aspects of dosing, such as dose levels and dosing frequency for phase III development.

Jak1 Integrates Cytokine Sensing to Regulate Hematopoietic Stem Cell Function and Stress Hematopoiesis

JAK1 is a critical effector of pro-inflammatory cytokine signaling and plays important roles in immune function, while abnormal JAK1 activity has been linked to immunological and neoplastic diseases. Specific functions of JAK1 in the context of hematopoiesis, and specifically within hematopoietic stem cells (HSCs), have not clearly been delineated. Here, we show that conditional Jak1 loss in HSCs reduces their self-renewal and markedly alters lymphoid/myeloid differentiation in vivo. Jak1-deficient HSCs exhibit decreased competitiveness in vivo and are unable to rescue hematopoiesis in the setting of myelosuppression. They exhibit increased quiescence, an inability to enter the cell cycle in response to hematopoietic stress, and a marked reduction in cytokine sensing, including in response to type I interferons and IL-3. Moreover, Jak1 loss is not fully rescued by expression of a constitutively active Jak2 allele. Together, these data highlight an essential role for Jak1 in HSC homeostasis and stress responses.

JAK-inhibitor tofacitinib suppresses interferon alfa production by plasmacytoid dendritic cells and inhibits arthrogenic and antiviral effects of interferon alfa

Tofacitinib is an oral Janus kinase inhibitor that is effective for the treatment of rheumatoid arthritis and shows encouraging therapeutic effects in several other autoimmune diseases. A prominent adverse effect of tofacitinib therapy is the increased risk of viral infections. Despite its advanced stage of clinical development, the modes of action that mediate the beneficial and adverse effects of tofacitinib in autoimmune diseases remain unclear. Interferon alfa (IFNα) produced by plasmacytoid dendritic cells (PDCs) is critically involved in the pathogenesis of many systemic autoimmune diseases and in immunity to viral infections. Using in vitro culture models with human cells, we studied the effects of tofacitinib on PDC survival and IFNα production, and on arthrogenic and antiviral effects of IFNα. Tofacitinib inhibited the expression of antiapoptotic BCL-A1 and BCL-XL in human PDC and induced PDC apoptosis. TLR7 stimulation upregulated the levels of antiapoptotic Bcl-2 family members and prevented the induction of PDC apoptosis by tofacitinib. However, tofacitinib robustly inhibited the production of IFNα by toll like receptor-stimulated PDC. In addition, tofacitinib profoundly suppressed IFNα-induced upregulation of TLR3 on synovial fibroblasts, thereby inhibiting their cytokine and protease production in response to TLR3 ligation. Finally, tofacitinib counteracted the suppressive effects of IFNα on viral replication. Tofacitinib inhibits PDC survival and IFNα production and suppresses arthrogenic and antiviral effects of IFNα signaling. Inhibition of the IFNα pathway at 2 levels may contribute to the beneficial effects of tofacitinib in autoimmune diseases and explain the increased viral infection rates observed during tofacitinib treatment.

Small molecule therapy for managing moderate to severe psoriatic arthritis

INTRODUCTION

The majority of psoriatic arthritis (PsA) patients experience a good clinical response to conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) and biologic therapies (bDMARDs). However, treatment failure with these drugs can represent a relevant clinical problem. Moreover, in daily clinical practice, the appropriate identification of patients eligible for these agents can be conditioned by numerous aspects, mainly represented by comorbidities, such as history of malignancies, chronic and recurrent infectious diseases. Areas covered: We searched in the PUBMED database and review published data on the efficacy and safety profile of the small molecules, inhibitor of phosphodiesterase 4, apremilast, and of JAK/STAT pathways, tofacitinib, in PsA. Moreover, we report data on the other JAK inhibitor, baricitinib, and the A(3) adenosine receptors agonist, CF101, emerging by studies conducted in psoriasis patients. Expert opinion: In Psoriatic Arthritis, apremilast appears promising for PsA and recent studies have shown a good efficacy and an acceptable safety profile. Data on tofacitinib in PsA are limited. Studies on the small molecules, baricitinib and CF101 are still incomplete and limited to trials conducted in Rheumatoid Arthritis and in psoriasis. Further studies on small molecules and on their underlining mechanisms are advocated in PsA.

Moderate to severe psoriasis treatment challenges through the era of biological drugs

Biological therapy has revolutionized moderate to severe psoriasis treatment. However, despite being more effective than conventional systemic treatments, some patients do not respond or lose response to biotechnological treatments or develop drug-antibodies, interfering with its safety and efficacy. There are also clinical forms of the disease and patient profiles for which is pending further scientific evidence for more sustained therapeutic interventions. The continuous and more detailed knowledge of psoriasis pathophysiology has allowed identifying new therapeutic targets, which is expected to help overcome the challenges of individualized psoriasis treatment.

JAK inhibitor has the amelioration effect in lupus-prone mice: the involvement of IFN signature gene downregulation

Background

We previously reported that JAK–STAT-pathway mediated regulation of IFN-regulatory factor genes could play an important role in SLE pathogenesis. Here, we evaluated the efficacy of the JAK inhibitor tofacitinib (TOFA) for controlling IFN signalling via the JAK–STAT pathway and as a therapeutic for SLE.

Results

We treated NZB/NZW F1 mice with TOFA and assessed alterations in their disease, pathological, and immunological conditions. Gene-expression results obtained from CD4⁺ T cells (SLE mice) and CD3⁺ T cells (human SLE patients) were measured by DNA microarray and qRT-PCR. TOFA treatment resulted in reduced levels of anti-dsDNA antibodies, decreased proteinuria, and amelioration of nephritis as compared with those observed in control animals. Moreover, we observed the rebalance in the populations of naïve CD4⁺ T cells and effector/memory cells in TOFA-treated mice; however, treatment with a combination of TOFA and dexamethasone (DEXA) elicited a stronger inhibitory effect toward the effector/memory cells than did TOFA or DEXA monotherapy. We also detected decreased expression of several IFN-signature genes Ifit3 and Isg15 in CD4⁺ from SLE-prone mice following TOFA and DEXA treatment, and IFIT3 in CD3⁺ T cells from human patients following immunosuppressant therapy including steroid, respectively.

Conclusion

Modulation of type I IFN signalling via JAK–STAT inhibition may exert a beneficial effect in SLE patients, and our results suggest that TOFA could be utilised for the development of new SLE-specific therapeutic strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0225-9) contains supplementary material, which is available to authorized users.

East Indian Sandalwood Oil (EISO) Alleviates Inflammatory and Proliferative Pathologies of Psoriasis

Psoriasis, a chronic inflammatory skin disease marked by hyper proliferation and aberrant differentiation of keratinocytes, affects 2–3% of the world’s population. Research into the pathogenesis of psoriasis has been hampered by the lack of models that accurately reflect the biology of the psoriatic phenotype. We have previously reported that East Indian Sandalwood oil (EISO) has significant anti-inflammatory properties in skin models and hypothesized that EISO might provide therapeutic benefit to psoriasis patients due to its anti-inflammatory and anti-proliferative properties. Here we present interim results from an on-going proof-of-concept Phase 2 clinical trial in which topically applied EISO is demonstrating to be well tolerated and helpful in alleviating mild to moderate psoriasis symptoms. This led us to evaluate the ability of EISO to affect the psoriatic phenotype using MatTek Corporation reconstituted organotypic psoriatic and normal human skin models. EISO had no impact on the phenotype of the normal skin tissue model, however, EISO treatment of the psoriasis tissue model reverted psoriatic pathology as demonstrated by histologic characterization and expression of keratinocyte proliferation markers, Ki67 and psoriasin. These phenotypic affects correlated with suppressed production of ENA-78, IL-6, IL-8, MCP-1, GM-CSF, and IL-1β. Demonstration of the ability of EISO to abrogate these psoriasis symptoms in well-characterized in vitro psoriatic tissue models, supports the hypothesis that the clinically observed symptom alleviation is due to suppression of intrinsic tissue inflammation reactions in afflicted lesions. This study presents a systematic approach to further study the underlying mechanisms that cause psoriasis, and presents data supporting the potential of EISO as a new ethnobotanical therapeutic concept to help direct and accelerate the development of more effective therapies.

Tofacitinib for the treatment of psoriasis

INTRODUCTION

The identification of a number of psoriasis-susceptibility genes and a better understanding of the pathogenesis of the intracellular metabolic pathways, have generated new perspectives on psoriasis treatment, in particular new compounds that inhibit certain intracellular proteins involved in the immune response. In contrast to biologic agents, these compounds block intracellular targets such as transcriptional factors or enzymes.

AREAS COVERED

Tofacitinib is a small molecule that acts as a reversible, competitive inhibitor of ATP in the ATP binding site of JAK proteins, determining their inactivation, thus prevents the downstream activation of the STAT proteins, which are then unable to up-regulate the pro-inflammatory genes implicated in psoriasis. The authors present an overview of Phases I - III clinical trials of tofacitinib for psoriasis based on peer-reviewed literature.

EXPERT OPINION

In clinical practice, it is important to assess the response of psoriasis to tofacitinib and identify possible clinical, genetic, and immune biomarkers to predict the response. Comorbidities associated with psoriasis, in particular metabolic syndrome and obesity, are also an important aspect of using tofacitinib in clinical practice. There are some evidences that a drug such as tofacitinib could be used to improve not only psoriasis, but also some of its important comorbidities.

Janus kinase (JAK) inhibitors for the treatment of skin and hair disorders: a review of literature

Janus kinase family (JAKs) has recently attracted the attention of many researchers, and several JAK inhibitor drugs have been developed targeting different members of the JAK family. Tofacitinib and ruxolitinib are US FDA approved drugs in this family for rheumatoid arthritis and myeloproliferative diseases, respectively. Dysregulation of JAK/STAT pathway is also involved in many skin diseases, specifically inflammatory disorders. The JAK/STAT signaling pathway and its involvement in skin diseases are overviewed in this study. We also review clinical studies of JAK inhibitors in field of dermatology, including psoriasis, atopic dermatitis, alopecia areata and vitiligo. Although the available evidence shows promising results, it is still too early to draw a firm conclusion about the place of these drugs in dermatological treatment.

Oral ruxolitinib induces hair regrowth in patients with moderate-to-severe alopecia areata

BACKGROUND. Alopecia areata (AA) is a common autoimmune disease with a lifetime risk of 1.7%; there are no FDA-approved treatments for AA. We previously identified a dominant IFN-γ transcriptional signature in cytotoxic T lymphocytes (CTLs) in human and mouse AA skin and showed that treatment with JAK inhibitors induced durable hair regrowth in mice by targeting this pathway. Here, we investigated the use of the oral JAK1/2 inhibitor ruxolitinib in the treatment of patients with moderate-to-severe AA. METHODS. We initiated an open-label clinical trial of 12 patients with moderate-to-severe AA, using oral ruxolitinib, 20 mg twice per day, for 3-6 months of treatment followed by 3 months follow-up off drug. The primary endpoint was the proportion of subjects with 50% or greater hair regrowth from baseline to end of treatment. RESULTS. Nine of twelve patients (75%) demonstrated a remarkable response to treatment, with average hair regrowth of 92% at the end of treatment. Safety parameters remained largely within normal limits, and no serious adverse effects were reported. Gene expression profiling revealed treatment-related downregulation of inflammatory markers, including signatures for CTLs and IFN response genes and upregulation of hair-specific markers. CONCLUSION. In this pilot study, 9 of 12 patients (75%) treated with ruxolitinib showed significant scalp hair regrowth and improvement of AA. Larger randomized controlled trials are needed to further assess the safety and efficacy of ruxolitinib in the treatment of AA. TRIAL REGISTRATION. Clinicaltrials.gov NCT01950780. FUNDING. Locks of Love Foundation, the Alopecia Areata Initiative, NIH/National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), and the Irving Institute for Clinical and Translational Research/Columbia University Medical Center Clinical and Translational Science Award (CUMC CTSA).

Association between psoriasis and inflammatory bowel disease: a Danish nationwide cohort study

BACKGROUND

Psoriasis, Crohn disease (CD) and ulcerative colitis (UC) are chronic inflammatory disorders with overlapping genetic architecture. However, data on the frequency and risk of CD and UC in psoriasis are scarce and poorly understood.

OBJECTIVES

To investigate the association between CD and UC in patients with psoriasis.

METHODS

All Danish individuals aged ≥ 18 years between 1 January 1997 and 31 December 2012 were linked in nationwide registers. Psoriasis severity was defined in two models: hospital visits and medication. Incidence rates per 10 000 person-years were calculated, and incidence rate ratios (IRRs) were estimated by Poisson regression.

RESULTS

In the total cohort (n = 5 554 100) there were 75 209 incident cases of psoriasis, 11 309 incident cases of CD and 30 310 incident cases of UC, during follow-up. The adjusted IRRs (95% confidence intervals) of CD were 1·28 (1·03-1·59), 2·56 (1·87-3·50), 2·85 (1·72-4·73) and 3·42 (2·36-4·95) in patients with mild psoriasis, severe psoriasis (hospital), severe psoriasis (medication) and psoriatic arthritis, respectively. Similarly, the adjusted IRRs of UC were 1·49 (1·32-1·68), 1·56 (1·22-2·00), 1·96 (1·36-2·83) and 2·43 (1·86-3·17), respectively. The 10-year incidence of CD was 2-5 per 1000 patients and of UC 7-11 per 1000 patients, depending on psoriasis severity and the presence of psoriatic arthritis. Additionally, an increased risk of incident psoriasis was found following CD or UC.

CONCLUSIONS

We observed a psoriasis-associated increased risk of CD and UC, which was higher in severe psoriasis, and an increased risk of psoriasis in patients with inflammatory bowel disease. Increased focus on gastrointestinal symptoms in patients with psoriasis may be warranted.

Fragment-Based Discovery of 6-Arylindazole JAK Inhibitors

Janus kinase (JAK) inhibitors are emerging as novel and efficacious drugs for treating psoriasis and other inflammatory skin disorders, but their full potential is hampered by systemic side effects. To overcome this limitation, we set out to discover soft drug JAK inhibitors for topical use. A fragment screen yielded an indazole hit that was elaborated into a potent JAK inhibitor using structure-based design. Growing the fragment by installing a phenol moiety in the 6-position afforded a greatly improved potency. Fine-tuning the substituents on the phenol and sulfonamide moieties afforded a set of compounds with lead-like properties, but they were found to be phototoxic and unstable in the presence of light.

Hyperactivation of JAK1 tyrosine kinase induces stepwise, progressive pruritic dermatitis

Skin homeostasis is maintained by the continuous proliferation and differentiation of epidermal cells. The skin forms a strong but flexible barrier against microorganisms as well as physical and chemical insults; however, the physiological mechanisms that maintain this barrier are not fully understood. Here, we have described a mutant mouse that spontaneously develops pruritic dermatitis as the result of an initial defect in skin homeostasis that is followed by induction of a Th2-biased immune response. These mice harbor a mutation that results in a single aa substitution in the JAK1 tyrosine kinase that results in hyperactivation, thereby leading to skin serine protease overexpression and disruption of skin barrier function. Accordingly, treatment with an ointment to maintain normal skin barrier function protected mutant mice from dermatitis onset. Pharmacological inhibition of JAK1 also delayed disease onset. Together, these findings indicate that JAK1-mediated signaling cascades in skin regulate the expression of proteases associated with the maintenance of skin barrier function and demonstrate that perturbation of these pathways can lead to the development of spontaneous pruritic dermatitis.

Oxidative stress in psoriasis and potential therapeutic use of antioxidants

The pathophysiology of psoriasis is complex and dynamic. Recently, the involvement of oxidative stress in the pathogenesis of psoriasis has been proposed. Oxidative stress is an imbalance between oxidants and antioxidants in favor of the oxidants, leading to a disruption of redox signaling and control and/or molecular damage. In this article, the published studies on the role of oxidative stress in psoriasis pathogenesis are reviewed, focusing on the impacts of oxidative stress on dendritic cells, T lymphocytes, and keratinocytes, on angiogenesis and on inflammatory signaling (mitogen-activated protein kinase, nuclear factor-κB, and Janus kinase/signal transducer and activator of transcription). As there is compelling evidence that oxidative stress is involved in the pathogenesis of psoriasis, the possibility of using this information to develop novel strategies for treatment of patients with psoriasis is of considerable interest. In this article, we also review the published studies on treating psoriasis with antioxidants and drugs with antioxidant activity.

Investigation of selective JAK1 inhibitor GSK2586184 for the treatment of psoriasis in a randomized placebo-controlled phase IIa study

BACKGROUND

GSK2586184 is a selective oral Janus kinase (JAK)1 inhibitor being evaluated as a treatment for moderate-to-severe plaque-type psoriasis.

OBJECTIVES

To assess the relationship between dose of GSK2586184 and clinical response, primarily by the Psoriasis Area Severity Index (PASI).

METHODS

Sixty patients with moderate-to-severe plaque psoriasis were randomized to cohort A: 100 mg, 200 mg or 400 mg GSK2586184 twice daily or placebo; and eight were randomized to open-label cohort B, a small exploratory cohort treated with 400 mg GSK2586184 twice daily, to explore differential gene expression.

RESULTS

At week 12, a 75% reduction in PASI (PASI 75) response rates in the intent-to-treat population were 0% in the placebo group compared with 13%, 25% and 57% in the 100 mg, 200 mg and 400 mg GSK2586184 twice-daily groups, respectively. Increases in the proportion of PASI 75 responses were seen across all dose levels by week 4. Improvement in itch and quality of life were observed at all doses relative to placebo with the greatest improvement seen in the 400-mg dose group. Overall, the incidence of adverse events (AEs) was similar across treatment groups, and no relationship between frequency of AE and GSK2586184 dose was identified. Differential gene expression was observed in involved and uninvolved skin at baseline and in involved skin after 2 weeks of treatment with GSK2586184.

CONCLUSIONS

Our study demonstrates that 12 weeks of treatment with GSK2586184 resulted in clinical improvement and was generally well tolerated in patients with moderate-to-severe plaque-type psoriasis.

Translational opportunities for targeting the Th17 axis in acute graft-vs.-host disease

Allogeneic stem cell transplantation (allo-SCT) is a curative therapy for different life-threatening malignant and non-malignant hematologic disorders. Acute graft-vs.-host disease (aGVHD) and particularly gastrointestinal aGVHD remains a major source of morbidity and mortality following allo-SCT, which limits the use of this treatment in a broader spectrum of patients. Better understanding of aGVHD pathophysiology is indispensable to identify new therapeutic targets for aGVHD prevention and therapy. Growing amount of data suggest a role for T helper (Th)17 cells in aGVHD pathophysiology. In this review, we will discuss the current knowledge in this area in animal models and in humans. We will then describe new potential treatments for aGVHD along the Th17 axis.

The anti-apoptotic Bcl-2 family protein A1/Bfl-1 regulates neutrophil survival and homeostasis and is controlled via PI3K and JAK/STAT signaling

Neutrophil granulocytes are innate effector cells of the first line of defense against pyogenic bacteria. Neutrophil lifespan is short, is prolonged by pro-inflammatory stimuli, controls functionality of the cells and can determine tissue damage. Experimental analysis of primary neutrophils is difficult because of their short lifespan and lack of possibilities of genetic manipulation. The Hoxb8 system of neutrophil differentiation from immortalized progenitor cells offers the advantage of unlimited production of neutrophils in vitro as well as easy genetic modification. We here use this system to analyze the role of the poorly characterized anti-apoptotic B-cell lymphoma protein 2 (Bcl-2) family member A1/Bfl-1 (Bcl-2-related protein A1) for survival and homeostasis of neutrophils and of neutrophil progenitors. Low constitutive mRNA and protein expression of A1 was detected, while A1 was transiently upregulated early during differentiation. Pro-inflammatory stimuli caused strong, mainly transcriptional, A1 upregulation, in contrast to posttranscriptional regulation of Mcl-1 (induced myeloid leukemia cell differentiation protein). Inhibitor studies showed that phosphoinositide-3 kinase (PI3K)/Akt and Janus kinase (JAK)/signal transducer and activator of transcription (STAT) is required for A1 expression and survival of progenitors and mature neutrophils. ShRNA-mediated constitutive A1 knockdown (KD) impaired maintenance of progenitors. ShRNA experiments further showed that A1 was required early during neutrophil differentiation as well as in mature neutrophils upon pro-inflammatory stimulation. Our data further indicate differential regulation of the two anti-apoptotic proteins A1 and Mcl-1. Relevant findings were confirmed in primary human neutrophils. Our data indicate that A1, in addition to the well-established Mcl-1, substantially contributes to neutrophil survival and homeostasis. A1 may thus be a promising target for anti-inflammatory therapy.

Emerging drugs for psoriatic arthritis

INTRODUCTION

The majority of Psoriatic Arthritis patients experience a good clinical response to anti-Tumor Necrosis Factor (TNF)-α therapies. However, treatment failure with anti-TNF-α can represent a relevant clinical problem.

AREAS COVERED

We review the efficacy and safety profile of biological therapies that have been reported from randomized, controlled trials in phase II and phase III available in Pubmed Database for agents targeting IL-12/23p40 antibody (ustekinumab) and IL-17 (secukinumab), inhibitor of phosphodiesterase 4, (apremilast), and of JAK/STAT pathways (tofacitinib) and CTLA4 co-stimulation (abatacept) in Psoriatic Arthritis.

EXPERT OPINION

In Psoriatic Arthritis, main emerging drugs are represented by the fully human monoclonal IL-12/23p40 antibody, ustekinumab, the agent targeting IL-17, secukinumab, and the inhibitor of phosphodiesterase 4, apremilast. Results on T cell co-stimulation inhibition by abatacept are insufficient both in psoriasis and in PsA. In vitro investigations on JAK/STAT pathways in PsA suggest that tofacitinib could represent a further valuable therapeutic option. Emerging biological treatments other than anti-TNF agents, ustekinumab, secukinumab and apremilast appear promising for Psoriatic Arthritis and recent studies have showed a good efficacy and an acceptable safety profile; however, further and long-term studies are advocated.

Profile of tofacitinib citrate and its potential in the treatment of moderate-to-severe chronic plaque psoriasis

The outlook for patients with psoriasis has improved significantly over the last 10 years with the introduction of targeted therapies. Cytokines exert their effects by activating intracellular signaling and transcription pathways, among which there are Janus kinases (JAKs) and signal transducers and activators of transcription (STAT) pathways. JAKs are intracellular second messengers that are crucial for transmitting extracellular cytokine signals to the cell. JAK inhibition interrupts intracellular signaling and can suppress immune cell activation and inflammation in T-cell-mediated disorders, such as psoriasis. Consequently, JAKs are the subject of intensive research activity, since they represent possible therapeutic targets. Tofacitinib is an orally available compound belonging to a novel category of nonbiologic drugs, the "JAK inhibitors", which target JAKs. Recently, oral and topical formulations of tofacitinib have been demonstrated to be safe and effective for the treatment of plaque psoriasis in randomized clinical trials. In particular, a 10 mg bid dose of tofacitinib was shown to be noninferior to etanercept 50 mg subcutaneously twice weekly. Questions remain unresolved regarding the safety risk beyond the 5 mg bid dose. This review, assessing the available scientific literature, focuses on the profile of tofacitinib, as investigational compound in the treatment of plaque psoriasis. An overview of the efficacy and safety data from randomized clinical trials is provided. In addition, the authors highlight future potential applications of tofacitinib in other skin diseases, in particular alopecia areata and vitiligo.

Structure-Based Design and Synthesis of 3-Amino-1,5-dihydro-4H-pyrazolopyridin-4-one Derivatives as Tyrosine Kinase 2 Inhibitors

We report herein the discovery and optimization of 3-amino-1,5-dihydro-4H-pyrazolopyridin-4-one TYK2 inhibitors. High-throughput screening against TYK2 and JAK1-3 provided aminoindazole derivative 1 as a hit compound. Scaffold hopping of the aminoindazole core led to the discovery of 3-amino-1,5-dihydro-4H-pyrazolopyridin-4-one derivative 3 as a novel chemotype of TYK2 inhibitors. Interestingly, initial SAR study suggested that this scaffold could have a vertically flipped binding mode, which prompted us to introduce a substituent at the 7-position as a moiety directed toward the solvent-exposed region. Introduction of a 1-methyl-3-pyrazolyl moiety at the 7-position resulted in a dramatic increase in TYK2 inhibitory activity, and further optimization led to the discovery of 20. Compound 20 inhibited IL-23-induced IL-22 production in a rat PD assay, as well as inhibited IL-23 signaling in human PBMC. Furthermore, 20 showed selectivity for IL-23 signaling inhibition against GM-CSF, demonstrating the unique cytokine selectivity of the novel TYK2 inhibitor.

A randomized, double-blind, placebo-controlled, dose-escalation study of the safety and efficacy of INCB039110, an oral janus kinase 1 inhibitor, in patients with stable, chronic plaque psoriasis

BACKGROUND

Chronic plaque psoriasis is partially mediated by elevation of proinflammatory cytokines, including several within the Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway.

OBJECTIVE

To evaluate the safety and efficacy of the oral selective JAK1 inhibitor INCB039110 in stable, chronic plaque psoriasis.

METHODS

This was a phase 2, randomized, double-blind, placebo-controlled, dose-escalation study of INCB039110 (100 mg once daily, 200 mg once daily, 200 mg twice daily and 600 mg once daily) for 28 days. The primary endpoint was mean percent change from baseline in the static Physician Global Assessment (sPGA) at day 28. The protocol was institutional review board approved.

RESULTS

Of 50 patients, 48 completed the study. At day 28, mean percent reduction from baseline in sPGA was 22.2% for INCB039110 100 mg once daily (p  =  0.270 vs. placebo), 29.4% for 200 mg once daily (p  =  0.118), 35.2% for 200 mg twice daily (p  =  0.053), 42.4% for 600 mg once daily (p  =  0.003) and 12.5% for placebo. Across groups, 11.1% to 45.5% achieved an sPGA score of 1 versus 0% for placebo. INCB039110 was generally well tolerated; the most common treatment-emergent adverse event was nasopharyngitis (18.4%).

CONCLUSION

INCB039110 produced significant improvements in sPGA, demonstrating proof of concept in chronic plaque psoriasis.

Immunological Consequences of JAK Inhibition: Friend or Foe?

Over the last decade, unparalleled advances have been made within the field of 'Philadelphia chromosome'-negative myeloproliferative neoplasms (MPN) regarding both disease pathogenesis and therapeutic targeting. The discovery of deregulated JAK-STAT signalling in MPN led to the rapid development of JAK inhibitor agents, targeting both mutated and wild-type JAK, which have significantly altered the therapeutic paradigm for patients with MPN. Although the largest population treated with these agents incorporates those with myelofibrosis, increasing data supports potential usage in other MPNs such as essential thromocythaemia and polycythaemia vera. Many MPNs are associated with a hyperinflammatory state and deregulation of immune homeostasis. Over the last few years, research has focused on attempting to decipher the complex and context-dependent changes that contribute to this immune deregulation. Moreover, very recent studies have demonstrated significant JAK inhibitor-mediated effects within the T cell, natural killer cell and dendritic cell compartments following exposure to JAK inhibitors. In parallel, case reports of infections occurring following exposure to ruxolitinib, many of which are atypical, have focused research efforts on delineating JAK inhibitor-associated immunological consequences. Within this review article, we will describe what is currently known about MPN-associated immune deregulation and JAK inhibitor-mediated immunomodulation.

Single cell tuning of Myc expression by antigen receptor signal strength and interleukin-2 in T lymphocytes

Myc controls the metabolic reprogramming that supports effector T cell differentiation. The expression of Myc is regulated by the T cell antigen receptor (TCR) and pro-inflammatory cytokines such as interleukin-2 (IL-2). We now show that the TCR is a digital switch for Myc mRNA and protein expression that allows the strength of the antigen stimulus to determine the frequency of T cells that express Myc. IL-2 signalling strength also directs Myc expression but in an analogue process that fine-tunes Myc quantity in individual cells via post-transcriptional control of Myc protein. Fine-tuning Myc matters and is possible as Myc protein has a very short half-life in T cells due to its constant phosphorylation by glycogen synthase kinase 3 (GSK3) and subsequent proteasomal degradation. We show that Myc only accumulates in T cells exhibiting high levels of amino acid uptake allowing T cells to match Myc expression to biosynthetic demands. The combination of digital and analogue processes allows tight control of Myc expression at the population and single cell level during immune responses.

Effect of JAK Inhibitors on Release of CXCL9, CXCL10 and CXCL11 from Human Airway Epithelial Cells

Background

CD8⁺ T-cells are located in the small airways of COPD patients and may contribute to pathophysiology. CD8⁺ cells express the chemokine receptor, CXCR3 that binds CXCL9, CXCL10 and CXCL11, which are elevated in the airways of COPD patients. These chemokines are released from airway epithelial cells via activation of receptor associated Janus kinases (JAK). This study compared the efficacy of two structurally dissimilar pan-JAK inhibitors, PF956980 and PF1367550, and the glucocorticosteroid dexamethasone, in BEAS-2B and human primary airway epithelial cells from COPD patients and control subjects.

Methods

Cells were stimulated with either IFNγ alone or with TNFα, and release of CXCL9, CXCL10 and CXCL11 measured by ELISA and expression of CXCL9, CXCL10 and CXCL11 by qPCR. Activation of JAK signalling was assessed by STAT1 phosphorylation and DNA binding.

Results

There were no differences in the levels of release of CXCL9, CXCL10 and CXCL11 from primary airway epithelial cells from any of the subjects or following stimulation with either IFNγ alone or with TNFα. Dexamethasone did not inhibit CXCR3 chemokine release from stimulated BEAS-2B or primary airway epithelial cells. However, both JAK inhibitors suppressed this response with PF1367550 being ~50-65-fold more potent than PF956980. The response of cells from COPD patients did not differ from controls with similar responses regardless of whether inhibitors were added prophylactically or concomitant with stimuli. These effects were mediated by JAK inhibition as both compounds suppressed STAT1 phosphorylation and DNA-binding of STAT1 and gene transcription.

Conclusions

These data suggest that the novel JAK inhibitor, PF1367550, is more potent than PF956980 and that JAK pathway inhibition in airway epithelium could provide an alternative anti-inflammatory approach for glucocorticosteroid-resistant diseases including COPD.

Tofacitinib for the treatment of moderate-to-severe psoriasis

Because of the increased knowledge about the underlying cytokine network in psoriasis, selective systemic agents for the treatment of moderate-to-severe psoriasis have been developed during the past decade. The marked upregulation of JAK/STAT pathways in psoriasis and the identification of multiple key mediators in psoriasis pathogenesis that signal through JAK/STAT pathways led to investigation of JAK proteins as potential therapeutic targets for psoriasis treatment. A novel JAK-STAT inhibitor, tofacitinib, has been tested in preclinical studies for the treatment of psoriasis. Considering the satisfactory safety profile and the encouraging efficacy observed in the Phase II and Phase III trials, tofacitinib may represent an important therapeutic to be included into the psoriasis paradigm.

The translational revolution and use of biologics in patients with inflammatory skin diseases

Psoriasis and atopic dermatitis (AD) are common inflammatory skin diseases characterized by immune-mediated inflammation and abnormal keratinocyte differentiation. Although T-cell infiltration characterizes both diseases, T-cell polarization differs. Psoriasis is currently the best model for translational medicine because many targeted therapeutics have been developed and testing of targeted therapeutics has cemented psoriasis as IL-23/TH17 polarized. In patients with AD, although therapeutic development is approximately a decade behind that in patients with psoriasis, there is now active development and testing of targeted therapeutics against various immune axes (TH2, TH22, and IL-23/TH17). These clinical trials and subsequent molecular analyses using human samples will be able to clarify the relative roles of polar cytokines in patients with AD.

Raf-interactome in tuning the complexity and diversity of Raf function

Raf kinases have been intensely studied subsequent to their discovery 30 years ago. The Ras-Raf-mitogen-activated protein kinase/extracellular signal-regulated kinase kinase-extracellular signal-regulated kinase/mitogen-activated protein kinase (Ras-Raf-MEK-ERK/MAPK) signaling pathway is at the heart of the signaling networks that control many fundamental cellular processes and Raf kinases takes centre stage in the MAPK pathway, which is now appreciated to be one of the most common sources of the oncogenic mutations in cancer. The dependency of tumors on this pathway has been clearly demonstrated by targeting its key nodes; however, blockade of the central components of the MAPK pathway may have some unexpected side effects. Over recent years, the Raf-interactome or Raf-interacting proteins have emerged as promising targets for protein-directed cancer therapy. This review focuses on the diversity of Raf-interacting proteins and discusses the mechanisms by which these proteins regulate Raf function, as well as the implications of targeting Raf-interacting proteins in the treatment of human cancer.

[Constipation after delivery: double-blind comparative study of 2 laxative preparations]

The inflammation-mediated comorbidities in myelofibrosis (MF) and related neoplasms (MPNs) likely reflect the concurrent immune deregulation and systemic inflammatory nature of the MPNs, emphasizing the link between chronic systemic inflammation, immune deregulation, and the malignant clone. JAK1-2 inhibitors in MF-patients reduce constitutional symptoms and splenomegaly, but also taget autoimmune and inflammation-mediated comorbidities.