TYK2 inhibition with deucravacitinib ameliorates erosive oral lichen planus

Erosive oral lichen planus (OLP) is a challenging disease. This T cell driven disorder frequently shows a treatment unresponsive course and strongly limits patients' quality of life. The disease lacks FDA or EMA approved drugs for its treatment and the efficacy of the commonly administered treatments (i.e. topical and systemic steroids, steroid sparing agents) is often only partial. Although the etiopathogenesis of the disease still needs to be fully elucidated, recent advances helped to identify interferon-ɣ (IFN-ɣ) as a pivotal cytokine in OLP pathogenesis, thus making the interference with its signalling a therapeutic target. Janus kinase (JAK) inhibitors therefore gained relevance for their inhibitory effect on IFN-ɣ signalling. While some drugs such as abrocitinib, upadacitinib, tofacitinib directly interfere with IFN-ɣ signalling through blockade of JAK1 and/or JAK2, deucravacitinib, a selective TYK-2 inhibitor indirectly interferes on IFN-ɣ activation through interference with interleukin (IL)-12, a potent promotor for Th1/IFN-ɣ responses. This mechanism of action makes deucravacitinib a candidate drug for the treatment of OLP. Here we provide initial evidence that deucravacitinib 6 mg daily has a beneficial effect in three patients with oral OLP.

Deucravacitinib: The First FDA-Approved Oral TYK2 Inhibitor for Moderate to Severe Plaque Psoriasis

OBJECTIVE

The objective of this study was to review the safety and efficacy of deucravacitinib, a tyrosine kinase 2 (TYK2) inhibitor for moderate to severe plaque psoriasis.

DATA SOURCES

Literature was reviewed from MEDLINE and Clinicaltrials.gov up to December 2022 using the terms "deucravacitinib" and "BMS-986165."

STUDY SELECTION

Relevant articles in English relating to the pharmacodynamics, pharmacokinetics, efficacy, and safety of deucravacitinib were included. A total of 6 trial results were included.

STUDY SELECTION AND DATA EXTRACTION

Deucravacitinib showed clinical efficacy across all the phase II and III clinical trials. Excluding the long-term extension study, there were 2248 subjects across all studies, with 63.2% of patients receiving deucravacitinib 6 mg daily. Of these subjects, the average proportion achieving a PASI 75 (a reduction of greater than 75% in the Psoriasis Area and Severity Index) at week 16 was 65.1%. Patients receiving deucravacitinib 6 mg once daily had a higher rate of achieving both PASI 75 response and a Static Physician's Global Assessment (sPGA) score of 0 or 1, compared with oral apremilast 30 mg twice daily. The safety profile of deucravacitinib includes mild adverse events (AEs), most commonly nasopharyngitis, with serious AEs reported ranging from 1.35% to 9.5%.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON WITH EXISTING MEDICATIONS

While many available therapies for moderate to severe plaque psoriasis rely on an injectable dosage form or extensive monitoring, deucravacitinib can potentially reduce patient medication-related burden. This review summarizes the efficacy and safety of oral deucravacitinib for the treatment of severe plaque psoriasis.

CONCLUSION

Deucravacitinib shows a consistent efficacy and safety profile as the first oral TYK2 inhibitor approved for adult patients with moderate to severe plaque psoriasis who are eligible for systemic therapy or phototherapy treatment.

Deucravacitinib, a selective, allosteric tyrosine kinase 2 inhibitor, in scalp psoriasis: A subset analysis of two phase 3 randomized trials in plaque psoriasis

BACKGROUND

Scalp involvement in plaque psoriasis is challenging to treat.

OBJECTIVE

To evaluate the efficacy and safety of deucravacitinib (DEUC) in scalp psoriasis.

METHODS

POETYK PSO-1 and PSO-2 were global phase 3, 52-week, double-blinded trials in adults with moderate to severe psoriasis. Patients were randomized 1:2:1 to oral placebo, DEUC 6 mg once daily, or apremilast 30 mg twice daily. This pooled secondary analysis evaluated scalp-specific Physician Global Assessment score of 0 or 1 (0/1), ≥90% improvement from baseline in Psoriasis Scalp Severity Index, and change from baseline in Psoriasis Scalp Severity Index. Adverse events were evaluated through week 16.

RESULTS

Overall, 1084 patients with moderate to severe scalp psoriasis at baseline were included. At week 16, response rates were greater with DEUC versus placebo or apremilast for scalp-specific Physician Global Assessment 0/1 (64.0% vs 17.3% vs 37.7%; P < .0001), ≥90% improvement from baseline in Psoriasis Scalp Severity Index (50.6% vs 10.5% vs 26.1%; P < .0001), and change from baseline in Psoriasis Scalp Severity Index. Responses were maintained through 52 weeks with continuous DEUC. Safety was consistent with the entire study population.

LIMITATIONS

Lack of data in milder scalp psoriasis.

CONCLUSION

DEUC was significantly more efficacious than placebo or apremilast in improving moderate to severe scalp psoriasis and was well tolerated.

Associations of genetic variants within TYK2 with pulmonary tuberculosis among Chinese population

BACKGROUND

Pulmonary tuberculosis (PTB) is a common infectious disease caused by mycobacterium tuberculosis (MTB) and the present study aims to explore the associations of genetic variants within tyrosine kinases 2 (TYK2) with PTB incidence.

METHODS

A population-based case control study including 168 smear-positive PTB cases and 251 controls was conducted. Five single nucleotide polymorphisms (SNPs) including rs280520, rs91755, rs2304256, rs12720270, rs280519 located within TYK2 gene were selected and MassARRAY® MALDI-TOF system was employed for genotyping. SPSS 19.0 was adopted for statistical analysis, non-conditional logistic regression was conducted. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were computed to estimate their contributions to PTB incidence.

RESULTS

In the overall study population, rs91755 TT and rs280519 AA genotypes were found to be associated with reduced PTB risk (OR = 0.34, 95% CI: 0.16-0.72; OR = 0.38, 95% CI: 0.18-0.79, respectively). After stratification for sex, we found that among the male population, rs91755TG/TT, rs12720270AG/GG and rs280519AG/AA genotypes were associated with reduced PTB risk (OR = 0.41, 95% CI: 0.21-0.80; OR = 0.44, 95% CI: 0.21-0.94; OR = 0.42, 95% CI: 0.21-0.82, respectively). After stratification for age, we found that among those aged <60 years, rs91755TT and rs280519AA genotype were associated with reduced PTB risk (OR = 0.29, 95% CI: 0.09-0.90; OR = 0.34, 95% CI: 0.11-1.08, respectively); while rs2304256AC/AA genotype was associated with increased PTB risk (OR = 2.68, 95% CI: 1.05-6.85). Haplotype analysis revealed that AGAAG and ATCGA (Combined with rs280520, rs91755, rs2304256, rs12720270 and rs280519) were associated with increased (OR = 1.54, 95% CI: 1.01-2.37) and decreased PTB risk (OR = 0.70, 95% CI: 0.52-0.94), respectively.

CONCLUSIONS

The genetic variants located within TYK2 including rs91755, rs12720270 and rs280519 were found to be associated with modified PTB risk and the SNPs had potential to be the biomarkers to predict PTB incidence risk.

Janus-kinase inhibitors in dermatology: A review of their use in psoriasis, vitiligo, systemic lupus erythematosus, hidradenitis suppurativa, dermatomyositis, lichen planus, lichen planopilaris, sarcoidosis and graft-versus-host disease

Recent studies on molecular pathways have elucidated novel therapeutic approaches in inflammatory and autoimmune skin disorders. Specifically, the dysregulation of the Janus kinase signal transducer and activator of transcription (JAK-STAT) cascade plays a central role in the pathogenesis of many skin conditions. JAK inhibitors, with their ability to selectively target immune responses, are potential treatment options. Using the National Library of Medicine, we provide a comprehensive review of the use of United States Food and Drug Administration (FDA)-approved and emerging JAK or tyrosine kinase 2 (TYK2) inhibitors in a wide range of dermatologic conditions, including psoriasis, vitiligo, systemic lupus erythematosus, hidradenitis suppurativa, dermatomyositis, lichen planus, lichen planopilaris, sarcoidosis and graft-versus-host disease. In patients with psoriasis, oral deucravacitinib (TYK2 inhibitor) has been approved as a once-daily therapy with demonstrated superiority and efficacy over apremilast and placebo and tolerable safety profiles. In patients with vitiligo, topical ruxolitinib (JAK1 inhibitor) is approved as a twice-daily treatment for repigmentation. The efficacy of several other JAK inhibitors has also been demonstrated in several clinical trials and case studies for systemic lupus erythematosus, hidradenitis suppurativa, dermatomyositis, lichen planus, lichen planopilaris, sarcoidosis and graft-versus-host disease. Further investigations with long-term clinical trials are necessary to confirm their utility in treatment and safety for these diseases.

Therapeutic potential of a synthetic dual JAK1/TYK2 inhibitor in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic and incurable disease with an increasing incidence rate and low mortality rate. Selectively inhibiting JAK1 and TYK2 has been proposed as a strategy to enhance the efficacy of such inhibitors while minimizing the potential side effects on other JAK isoforms. Our previous studies identified small molecule 18 as a JAK1/TYK2 inhibitor with high selectivity and a new structure. Specifically, the IC50 of 18 at the kinase level reached 39 nM and 21 nM for JAK1 and TYK2, respectively, with 10-fold selectivity over both JAK2 and JAK3. In in vitro studies, 18 dose-dependently inhibited cytokine-induced STAT phosphorylation downstream of the JAK1 and TYK2 signaling pathway. In pharmacokinetic experiments, 18 demonstrated an oral bioavailability of 59.82%, making it a promising candidate for further in vivo studies. Using two mouse models of acute ulcerative colitis (UC) induced by the administration of dextran sulfate sodium (DSS) or oxazolone (OXA), 18 dose-dependently showed a better therapeutic effect than the positive control drug tofacitinib. Additionally, after long-term administration for 32 days, 18 displayed low toxicity to mice and a high safety profile. Taken together, these findings suggest that 18 is a JAK1/TYK2 dual inhibitor with therapeutic effects superior to those of tofacitinib in the treatment of IBD. Moreover, 18 is also a suitable clinical candidate for further investigation in diseases with strong involvement from interferon and/or IL-12/IL-23 in their pathogenesis. This study confirmed the therapeutic effect and long-term safety of inhibiting JAK1 and TYK2 to treat IBD.

Tick-borne flavivirus NS5 antagonizes interferon signaling by inhibiting the catalytic activity of TYK2

The mechanisms utilized by different flaviviruses to evade antiviral functions of interferons are varied and incompletely understood. Using virological approaches, biochemical assays, and mass spectrometry analyses, we report here that the NS5 protein of tick-borne encephalitis virus (TBEV) and Louping Ill virus (LIV), two related tick-borne flaviviruses, antagonize JAK-STAT signaling through interactions with the tyrosine kinase 2 (TYK2). Co-immunoprecipitation (co-IP) experiments, yeast gap-repair assays, computational protein-protein docking and functional studies identify a stretch of 10 residues of the RNA dependent RNA polymerase domain of tick-borne flavivirus NS5, but not mosquito-borne NS5, that is critical for interactions with the TYK2 kinase domain. Additional co-IP assays performed with several TYK2 orthologs reveal that the interaction is conserved across mammalian species. In vitro kinase assays show that TBEV and LIV NS5 reduce the catalytic activity of TYK2. Our results thus illustrate a novel mechanism by which viruses suppress the interferon response.

Deucravacitinib in the treatment of psoriasis

PURPOSE OF THE ARTICLE

Psoriasis is a chronic, immune-mediated, skin disease with a significantly negative impact on patients' quality of life. Moderate-to-severe disease often requires systemic therapies and currently available ones still have numerous disadvantages or limitations. Tyrosine kinase 2 (TYK2) mediates immune signaling of IL-12, IL-23, and type I interferons, without interfering with other critical systemic functions. This article aims to review the current knowledge on deucravacitinib, a new oral drug which selectively inhibits TYK2, granting it a low risk of off-target effects.

MATERIALS AND METHODS

A review of the published literature was conducted using the PubMed database, published abstracts and virtual presentations from scientific meetings, data from industry press releases, and results published on ClinicalTrials.gov regarding the deucravacitinib for the treatment of psoriasis. Manuscripts with trial results, case series, clinical trial data from ClinicalTrials.gov, and articles highlighting expert perspectives on the topic of the article were selected.

RESULTS

Two phase 3, 52-week trials evaluated deucravacitinib 6 mg against placebo and apremilast - POETYK PSO-1 and PSO-2, enrolling 1688 patients with moderate-to-severe psoriasis. At week 16, over 50% of patients treated with deucravacitinib reached PASI75, significantly superior to placebo and apremilast. Symptomatic improvement was also reported, with greater impact on itch. Deucravacitinib was well tolerated and safe. There were no reports of serious infections, thromboembolic events, or laboratory abnormalities. Persistent efficacy and consistent safety profiles were reported for up to 2 years.

CONCLUSIONS

Deucravacitinib has the potential to become a safe, effective, and well-tolerated treatment for patients with moderate-to-severe disease. Future studies will be important to determine the exact role of this drug in the treatment of psoriasis.

Allosteric TYK2 inhibition: redefining autoimmune disease therapy beyond JAK1-3 inhibitors

JAK inhibitors impact multiple cytokine pathways simultaneously, enabling high efficacy in treating complex diseases such as cancers and immune-mediated disorders. However, their broad reach also poses safety concerns, which have fuelled a demand for increasingly selective JAK inhibitors. Deucravacitinib, a first-in-class allosteric TYK2 inhibitor, represents a remarkable advancement in the field. Rather than competing at kinase domain catalytic sites as classical JAK1-3 inhibitors, deucravacitinib targets the regulatory pseudokinase domain of TYK2. It strikingly mirrors the functional effect of an evolutionary conserved naturally occurring TYK2 variant, P1104A, known to protect against multiple autoimmune diseases yet provide sufficient TYK2-mediated cytokine signalling required to prevent immune deficiency. The unprecedentedly high functional selectivity and efficacy-safety profile of deucravacitinib, initially demonstrated in psoriasis, combined with genetic support, and promising outcomes in early SLE clinical trials make this inhibitor ripe for exploration in other autoimmune diseases for which better, safe, and efficacious treatments are urgently needed.

A Novel Homozygous Mutation Causing Complete TYK2 Deficiency, with Severe Respiratory Viral Infections, EBV-Driven Lymphoma, and Jamestown Canyon Viral Encephalitis

Autosomal recessive tyrosine kinase 2 (TYK2) deficiency is characterized by susceptibility to mycobacterial and viral infections. Here, we report a 4-year-old female with severe respiratory viral infections, EBV-driven Burkitt-like lymphoma, and infection with the neurotropic Jamestown Canyon virus. A novel, homozygous c.745C > T (p.R249*) variant was found in TYK2. The deleterious effects of the TYK2 lesion were confirmed by immunoblotting; by evaluating functional responses to IFN-α/β, IL-10, and IL-23; and by assessing its scaffolding effect on the cell surface expression of cytokine receptor subunits. The effects of the mutation could not be pharmacologically circumvented in vitro, suggesting that alternative modalities, such as hematopoietic stem cell transplantation or gene therapy, may be needed. We characterize the first patient from Canada with a novel homozygous mutation in TYK2.

A novel highly selective allosteric inhibitor of tyrosine kinase 2 (TYK2) can block inflammation- and autoimmune-related pathways

BACKGROUND

As a member of the Janus kinase (JAK) family, which includes JAK1, JAK2 and JAK3, tyrosine kinase 2 (TYK2) plays an important role in signal transduction and immune system regulation. Moreover, it is also involved in the development of many types of inflammatory and autoimmune diseases, such as psoriasis and systemic lupus erythematosus (SLE). TYK2 is an attractive therapeutic target, and selective inhibition of TYK2 over other JAK family members is critical for the development of TYK2 small molecule inhibitors. However, targeting the catalytic region of the TYK2 ATP-binding site is a major challenge due to the high structural homology between the catalytic regions of the JAK family proteins.

RESULTS

In this study, we developed a novel small molecule inhibitor (QL-1200186) by targeting the pseudokinase regulatory domain (Janus homology 2, JH2) of the TYK2 protein. The binding sites of QL-1200186 were predicted and screened by molecular docking. The inhibitory effects on IFNα, IL-12 and IL-23 signaling were tested in cell lines, human peripheral blood cells and human whole blood. The pharmacokinetic (PK) and pharmacodynamic properties of QL-1200186 were verified in mice. QL-1200186 showed high affinity for TYK2 JH2 and had no apparent selectivity for the TYK2 and JAK homologous kinase domains; these effects were demonstrated using biochemical binding, signaling pathway transduction (JAK1/2/3) and off-target effect assays. More importantly, we revealed that QL-1200186 was functionally comparable and selectivity superior to two clinical-stage TYK2 inhibitors (BMS-986165 and NDI-034858) in vitro. In the PK studies, QL-1200186 exhibited excellent exposure, high bioavailability and low clearance rates in mice. Oral administration of QL-1200186 dose-dependently inhibited interferon-γ (IFNγ) production after interleukin-12 (IL-12) challenge and significantly ameliorated skin lesions in psoriatic mice.

CONCLUSION

These findings suggest that QL-1200186 is a highly selective and potent inhibitor of TYK2. QL-1200186 could be an appealing clinical drug candidate for the treatment of psoriasis and other autoimmune diseases. Video Abstract.

The Relationship between COVID-19 Severity in Children and Immunoregulatory Gene Polymorphism

Coronavirus disease (COVID-19) and its outcomes remain one of the most challenging problems today. COVID-19 in children could be asymptomatic, but can result in a fatal outcome; therefore, predictions of the disease severity are important. The goal was to investigate the human genetic factors that could be associated with COVID-19 severity in children. Single-nucleotide polymorphisms of the following genes were studied: ACE2 (rs2074192), IFNAR2 (rs2236757), TYK2 (rs2304256), OAS1 (rs10774671), OAS3 (rs10735079), CD40 (rs4813003), FCGR2A (rs1801274) and CASP3 (rs113420705). In the case-control study were 30 children with mild or moderate course of the disease; 30 with severe COVID-19 symptoms and multisystem inflammatory syndrome in children (MIS-C) and 15 who were healthy, and who did not have SARS-CoV-2 (PCR negative, Ig G negative). The study revealed that ACE2 rs2074192 (allele T), IFNAR2 rs2236757 (allele A), OAS1 rs10774671 (allele A), CD40 rs4813003 (allele C), CASP3 rs113420705 (allele C) and male sex contribute to severe COVID-19 course and MIS-C in 85.6% of cases. The World Health Organization reported that new SARS-CoV-2 variants may cause previously unseen symptoms in children. Although the study has limitations due to cohort size, the findings can help provide a better understanding of SARS-CoV-2 infection and proactive pediatric patient management.

Deucravacitinib, a tyrosine kinase 2 pseudokinase inhibitor, protects human EndoC-βH1 β-cells against proinflammatory insults

Introduction

Type 1 diabetes is characterized by pancreatic islet inflammation and autoimmune-driven pancreatic β-cell destruction. Interferon-α (IFNα) is a key player in early human type 1 diabetes pathogenesis. IFNα activates the tyrosine kinase 2 (TYK2)-signal transducer and activator of transcription (STAT) pathway, leading to inflammation, HLA class I overexpression, endoplasmic reticulum (ER) stress, and β-cell apoptosis (in synergy with IL-1β). As TYK2 inhibition has raised as a potential therapeutic target for the prevention or treatment of type 1 diabetes, we investigated whether the selective TYK2 inhibitor deucravacitinib could protect β-cells from the effects of IFNα and other proinflammatory cytokines (i.e., IFNγ and IL-1β).

Methods

All experiments were performed in the human EndoC-βH1 β-cell line. HLA class I expression, inflammation, and ER stress were evaluated by real-time PCR, immunoblotting, and/or immunofluorescence. Apoptosis was assessed by the DNA-binding dyes Hoechst 33342 and propidium iodide or caspase 3/7 activity. The promoter activity was assessed by luciferase assay.

Results

Deucravacitinib prevented IFNα effects, such as STAT1 and STAT2 activation and MHC class I hyperexpression, in a dose-dependent manner without affecting β-cell survival and function. A comparison between deucravacitinib and two Janus kinase inhibitors, ruxolitinib and baricitinib, showed that deucravacitinib blocked IFNα- but not IFNγ-induced signaling pathway. Deucravacitinib protected β-cells from the effects of two different combinations of cytokines: IFNα + IL-1β and IFNγ + IL-1β. Moreover, this TYK2 inhibitor could partially reduce apoptosis and inflammation in cells pre-treated with IFNα + IL-1β or IFNγ + IL-1β.

Discussion

Our findings suggest that, by protecting β-cells against the deleterious effects of proinflammatory cytokines without affecting β-cell function and survival, deucravacitinib could be repurposed for the prevention or treatment of early type 1 diabetes.

Deucravacitinib: a novel TYK2 inhibitor for the treatment of moderate-to-severe psoriasis

Background

Deucravacitinib is a first-in-class tyrosine kinase 2 (TYK2) inhibitor recently approved for the treatment of adults with moderate-to-severe plaque psoriasis.

Objective

To discuss the mechanism of action, efficacy, safety, and real-world applications of deucravacitinib for the treatment of psoriasis.

Methods

Literature on the mechanism of action of deucravacitinib is reviewed. The pivotal clinical studies and long-term extension studies for deucravacitinib are also examined.

Results

Deucravacitinib is a novel oral TYK2 inhibitor that binds to the regulatory domain of TYK2, a Janus kinase. By inhibiting TYK2, deucravacitinib interferes with signaling of IL-23, IL-12, and type I interferons, cytokines believed to play important roles in psoriasis pathogenesis. Nearly 60% of patients achieve PASI 75 at 16 weeks of treatment; efficacy improves over 24 weeks and is maintained through 2 years of continuous treatment. In a head-to-head comparison, deucravacitinib efficacy was superior to apremilast, an older yet commonly used oral PDE4 inhibitor approved for the treatment of psoriasis. Of note, patients with moderate-to-severe plaque psoriasis with concomitant involvement of the scalp, nails, and/or palms/soles demonstrated good improvement in these high impact areas. Deucravacitinib has an acceptable safety profile and is generally well-tolerated. Small increases in reactivation of herpesvirus infections, including herpes simplex outbreaks, have been reported. Tuberculosis evaluation, but no other blood tests, is recommended prior to initiation of deucravacitinib. Monitoring of triglyceride levels should be conducted for high-risk patients according to local guidelines.

Conclusion

Deucravacitinib is an effective, safe, and well-tolerated novel oral medication for adults with moderate-to-severe plaque psoriasis.

Synthetic Heterodimers of Type III Interferon Receptors Require TYK2 for STAT Activation

Type III interferons (IFN-λ) are central to host defense against viral infection of epithelial barrier surfaces. IFN-λ binding to its receptor induces a JAK-STAT cascade through kinases Janus-associated kinase 1 (JAK1) and tyrosine kinase 2 (TYK2), which are associated on either subunit of the heterodimeric type III IFN receptor. Recent studies have shown that TYK2 is not necessary for IFN-λ to signal, in contrast to IFN-α, which uses the same JAK-STAT pathway activated by the type I IFN receptor. The mechanism for this differential TYK2 requirement is unknown. Our study uses synthetic IFN receptors in TYK2-deficient U2OS epithelial cells to define the processes in type I and III IFN signaling that require TYK2. We find that TYK2 deficiency reduces signaling equally from heterodimers of either type I or III IFN receptor intracellular domains. In contrast, JAK1-associated homodimers of IFNAR2 or IFNLR1 are both fully signaling competent even in the absence of TYK2. These results suggest that heterodimerization of the type III IFN receptor is insufficient to confer TYK2-independent signaling. Thus, we propose that noncanonical receptor complexes may participate in endogenous type III IFN signaling to confer TYK2-independent signaling downstream of IFN-λ stimulation.

Janus kinase inhibitors in systemic lupus erythematosus: implications for tyrosine kinase 2 inhibition

Aberrant activation of the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathway is common in systemic lupus erythematosus (SLE), conferring immune-mediated properties in target tissues. Multiple cytokines activate different combinations of JAKs and STATs to alter the cell fate of target tissue and induce end-organ damage. Thus, the simultaneous blockade of several different cytokines by small molecules acting downstream intracellular signalling has gained traction. JAK inhibitors have been approved for the treatment of several rheumatic diseases, yet hitherto not for SLE. Nevertheless, JAK inhibitors including tofacitinib, baricitinib, and deucravacitinib have shown merit as treatments for SLE. Tofacitinib, a JAK1/3 inhibitor, reduced cholesterol levels, improved vascular function, and decreased the type I interferon signature in SLE patients. Baricitinib, a JAK1/2 inhibitor, demonstrated significant improvements in lupus rashes and arthritis in a phase 2 and a phase 3 randomised controlled trial, but the results were not replicated in another phase 3 trial. Deucravacitinib, a selective tyrosine kinase 2 (TYK2) inhibitor, yielded greater response rates than placebo in a phase 2 trial of SLE and will be investigated in larger phase 3 trials. TYK2 is activated in response to cytokines actively involved in lupus pathogenesis; this review highlights the potential of targeting TYK2 as a promising therapy for SLE.

Revisiting the interleukin 17 family of cytokines in psoriasis: pathogenesis and potential targets for innovative therapies

Psoriasis is a common chronic inflammatory skin disease, associated with substantial comorbidity. TH17 lymphocytes, differentiating under the influence of dendritic cell-derived IL-23, and mediating their effects via IL-17A, are believed to be central effector cells in psoriasis. This concept is underlined by the unprecedented efficacy of therapeutics targeting this pathogenetic axis. In recent years, numerous observations made it necessary to revisit and refine this simple "linear" pathogenetic model. It became evident that IL-23 independent cells exist that produce IL-17A, that IL-17 homologues may exhibit synergistic biological effects, and that the blockade of IL-17A alone is clinically less effective compared to the inhibition of several IL-17 homologues. In this review, we will summarize the current knowledge around IL-17A and its five currently known homologues, namely IL-17B, IL-17C, IL-17D, IL-17E (also known as IL-25) and IL-17F, in relation to skin inflammation in general and psoriasis in particular. We will also re-visit the above-mentioned observations and integrate them into a more comprehensive pathogenetic model. This may help to appreciate current as well as developing anti-psoriatic therapies and to prioritize the selection of future drugs' mode(s) of action.

Deucravacitinib, a selective tyrosine kinase 2 inhibitor, for the treatment of moderate-to-severe plaque psoriasis

INTRODUCTION

Protein kinases play a crucial role in intracellular signaling pathways that lead to inflammation and cell proliferation. New understandings of the involvement of these metabolic pathways in the pathogenesis of psoriasis allowed the development of a new class of drugs. Unlike biologics, these compounds work by blocking intracellular targets involved in the immune response.

AREAS COVERED

Deucravacitinib is an oral small molecule inhibitor of TYK2 that binds the pseudokinase domain and locks the kinase in an inactive state by an allosteric mechanism, arresting TYK2- mediated signaling cascades and disabling the upregulation of proinflammatory genes implicated in psoriasis. The authors present the results of phase I - III clinical trials of deucravacitinib for the treatment of psoriasis.

EXPERT OPINION

At week 16 about 56% of patients treated with deucravacitinib achieved PASI75. No serious infections were reported, nor were thromboembolic events or laboratory abnormalities. Efficacy was reported to be persistent and safety profiles were shown to be consistent for up to 2 years. Deucravacitinib can potentially become a safe, effective, well-tolerated treatment for patients suffering from moderate-to-severe disease. Future studies and real-life experiences will be important to determine the exact role of this drug in the treatment of psoriasis.

Recent developments for new investigational JAK inhibitors in psoriatic arthritis

INTRODUCTION

Psoriatic arthritis (PsA) is a chronic inflammatory disease affecting about one-third of subjects with psoriasis. Several treatment modalities targeting Janus Kinase pathways and intracellular inflammatory cascade are now available and under clinical investigation to treat this disease.

AREAS COVERED

This review describes ongoing and recently completed phase 2 and 3 Randomized Clinical Trials (RCTs) evaluating the efficacy and safety of approved JAK (Tofacitinib and Upadacitinib) and investigational JAK inhibitors (JAK1 inhibitors: Filgotinib and Ivarmacitinib (SHR0302); TYK2 inhibitors: Brepocitinib (PF-06700841) Deucravacitinib (BMS-986165), and NDI-034858) in PsA through February 2023.

EXPERT OPINION

Current standard of care has significantly improved the quality of life in PsA. Recently approved JAK inhibitors for PsA have addressed many of the unmet needs of PsA, particularly of those with severe phenotypes. Preliminary results from several RCTs have reported good and fast efficacy and an acceptable safety profile of investigational JAK inhibitors in PsA. Additional clinical trials and long-term outcome data on these agents are necessary for increasing available therapeutic options for PsA.

TYK2 single-nucleotide variants associated with the severity of COVID-19 disease

Coronavirus disease 2019 (COVID-19) is a lethal disease caused by the coronavirus SARS-CoV-2, which can result in a broad clinical spectrum of respiratory symptoms. While many clinical risk factors such as concomitant chronic diseases play roles in the pathophysiology of COVID-19, genetic predisposition factors have not been widely studied. The aim of this study was, therefore, to evaluate the relationship between some singlenucleotide polymorphisms (SNPs) of the human genes TYK2 and ACE2 and the severity of SARS-CoV-2 infection. Genomic DNA was isolated from 200 SARS-CoV-2-infected individuals with severe (n = 100) or mild (n = 100) disease. Owing to the importance of ACE2 and TYK2 genes in regulating the immune response to SARS-CoV-2 infection, TYK2 gene SNPs, i.e. rs2304255, rs2304256, rs12720270, and rs12720354 and ACE2 rs382746 variants, were genotyped in the samples. To confirm the results, the expression of different TYK2 genotypes was investigated using real-time PCR. The presence of the nucleotide T at the locus rs2304255 was shown to be a risk factor linked to disease severity (OR [95% CI] = 3.2485 [2.1554-4.8961]). Similarly, the presence of A at the locus rs12720354 increased the risk of severity (OR [95% CI]) = 3.9721 [2.6075-6.0509]). In contrast, the presence of A at the loci rs2304256 and rs12720270 was observed to reduce the severity risk (OR [95% CI] = 0.2495 [0.1642-0.3793] and 0.1668 [0.1083-0.2569], respectively). Real-time PCR results also demonstrated that the expression level of TYK2 in samples with the TT genotype of rs2304255 and the AA genotype of rs12720354 and in samples with the GG genotype of rs12720207 was significantly lower than in those with other genotypes. The results of this study suggest that TYK2 SNPs might be utilized to identify individuals who are at risk for severe COVID-19, in order to better manage their health care. It is predicted that the presence of some alleles (T in rs2304255, A in rs12720354, and G in rs12720207) of TYK2 can affect COVID-19 severity by reducing TYK2 expression and thereby affecting the regulatory role of TYK2 in the immune response.

Design, synthesis and biological evaluation of novel N-(methyl-d3) pyridazine-3-carboxamide derivatives as TYK2 inhibitors

As a mediator of pro-inflammatory cytokines, TYK2 is an attractive target to treat autoimmunity diseases. Herein, we reported the design, synthesis, and structure-activity relationships (SARs) of N-(methyl-d₃) pyridazine-3-carboxamide derivatives as TYK2 inhibitors. Among them, compound 24 exhibited acceptable inhibition activity against STAT3 phosphorylation. Furthermore, 24 showed satisfactory selectivities toward other members of JAK family and performed a good stability profile in liver microsomal assay. Pharmacokinetics (PK) study indicated that compound 24 has reasonable PK exposures. In anti-CD40-induced colitis models, compound 24 was orally highly effective with no significant hERG and CYP isozymes inhibition. These results indicated that compound 24 was worthy of further investigation for the development of anti-autoimmunity diseases agents.

Mendelian randomization and clinical trial evidence supports TYK2 inhibition as a therapeutic target for autoimmune diseases

BACKGROUND

To explore the associations of genetically proxied TYK2 inhibition with a wide range of disease outcomes and biomarkers to identify therapeutic repurposing opportunities, adverse effects, and biomarkers of efficacy.

METHODS

The loss-of-function missense variant rs34536443 in TYK2 gene was used as a genetic instrument to proxy the effect of TYK2 inhibition. A phenome-wide Mendelian randomization (MR) study was conducted to explore the associations of genetically-proxied TYK2 inhibition with 1473 disease outcomes in UK Biobank (N = 339,197). Identified associations were examined for replication in FinnGen (N = 260,405). We further performed tissue-specific gene expression MR, colocalization analyses, and MR with 247 blood biomarkers. A systematic review of randomized controlled trials (RCTs) on TYK2 inhibitor was performed to complement the genetic evidence.

FINDINGS

PheWAS-MR found that genetically-proxied TYK2 inhibition was associated with lower risk of a wide range of autoimmune diseases. The associations with hypothyroidism and psoriasis were confirmed in MR analysis of tissue-specific TYK2 gene expression and the associations with systemic lupus erythematosus, psoriasis, and rheumatoid arthritis were observed in colocalization analysis. There were nominal associations of genetically-proxied TYK2 inhibition with increased risk of prostate and breast cancer but not in tissue-specific expression MR or colocalization analyses. Thirty-seven blood biomarkers were associated with the TYK2 loss-of-function mutation. Evidence from RCTs confirmed the effectiveness of TYK2 inhibitors on plaque psoriasis and reported several adverse effects.

INTERPRETATION

This study supports TYK2 inhibitor as a potential treatment for psoriasis and several other autoimmune diseases. Increased pharmacovigilance is warranted in relation to the potential adverse effects.

FUNDING

None.

Novel Therapies in Plaque Psoriasis: A Review of Tyrosine Kinase 2 Inhibitors

Plaque psoriasis is a systemic immune-mediated disease driven by interleukin-17 producing cells under the regulation of interleukin-23. Interleukin-23 signaling is mediated by the intracellular kinase tyrosine kinase 2, a Janus kinase family member. Tyrosine kinase 2 is a potential target for oral small-molecule therapies to treat psoriasis and psoriatic arthritis. A number of tyrosine kinase 2 inhibitors are in development or approved for the treatment of psoriasis or psoriatic arthritis. Deucravacitinib, an oral, selective, allosteric tyrosine kinase 2 inhibitor, is approved by the US Food and Drug Administration as a first-in-class treatment for adults with moderate-to-severe plaque psoriasis who are candidates for systemic therapy or phototherapy, and is approved by Pharmaceuticals and Medical Devices Agency (PDMA) in Japan for patients with plaque psoriasis, generalized pustular psoriasis, and erythrodermic psoriasis who have had an inadequate response to conventional therapies. Deucravacitinib selectively binds to the unique tyrosine kinase 2 regulatory pseudokinase domain in an allosteric fashion, preventing a conformational change in the catalytic domain required for ATP substrate binding, thus effectively locking tyrosine kinase 2 in an inactive state. Two other tyrosine kinase 2 inhibitors in later stage clinical development, brepocitinib (PF-06700841) and ropsacitinib (PF-06826647), are orthosteric inhibitors that target the highly conserved catalytic domain. This selective allosteric tyrosine kinase 2 inhibition may explain the improved safety profile of deucravacitinib versus orthosteric Janus kinase and tyrosine kinase 2 inhibitors. Two phase 3 psoriasis trials demonstrated deucravacitinib was efficacious and not associated with safety concerns characteristic of Janus kinase inhibitors, hence the new class designation (TYK2 inhibitor) by health authorities in the USA and Japan. Allosteric tyrosine kinase 2 inhibitors represent a promising new class of molecules for the treatment of psoriasis and psoriatic arthritis, and longer-term trials will establish their place in therapy.

Polymorphisms in ACE1, TMPRSS2, IFIH1, IFNAR2, and TYK2 Genes Are Associated with Worse Clinical Outcomes in COVID-19

Although advanced age, male sex, and some comorbidities impact the clinical course of COVID-19, these factors only partially explain the inter-individual variability in disease severity. Some studies have shown that genetic polymorphisms contribute to COVID-19 severity; however, the results are inconclusive. Thus, we investigated the association between polymorphisms in ACE1, ACE2, DPP9, IFIH1, IFNAR2, IFNL4, TLR3, TMPRSS2, and TYK2 and the clinical course of COVID-19. A total of 694 patients with COVID-19 were categorized as: (1) ward inpatients (moderate symptoms) or patients admitted at the intensive care unit (ICU; severe symptoms); and (2) survivors or non-survivors. In females, the rs1990760/IFIH1 T/T genotype was associated with risk of ICU admission and death. Moreover, the rs1799752/ACE1 Ins and rs12329760/TMPRSS2 T alleles were associated with risk of ICU admission. In non-white patients, the rs2236757/IFNAR2 A/A genotype was associated with risk of ICU admission, while the rs1799752/ACE1 Ins/Ins genotype, rs2236757/IFNAR2 A/A genotype, and rs12329760/TMPRSS2 T allele were associated with risk of death. Moreover, some of the analyzed polymorphisms interact in the risk of worse COVID-19 outcomes. In conclusion, this study shows an association of rs1799752/ACE1, rs1990760/IFIH1, rs2236757/IFNAR2, rs12329760/TMPRSS2, and rs2304256/TYK2 polymorphisms with worse COVID-19 outcomes, especially among female and non-white patients.

TYK2 in Immune Responses and Treatment of Psoriasis

Tyrosine kinase 2 (TYK2), a key part of the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway, plays an integral role in the differentiation and immune responses of intrinsic immune cells and regulates the mediation of cytokines. TYK2 leads to inflammatory cascade responses in the pathogenesis of immune-mediated inflammatory diseases (IMIDs), especially psoriasis. Small-molecule TYK2 inhibitors are considered to be an effective strategy for modulating psoriasis. Here, we attempt to review the pro-inflammatory mechanisms of the JAK-STAT signaling pathway, the regulatory roles of TYK2 in the pathogenesis of psoriasis, and provide updates on ongoing and recently completed trials of TYK2 inhibitors.

Identification and characterization of TYK2 pseudokinase domain stabilizers that allosterically inhibit TYK2 signaling

Kinase inhibition continues to be a major focus of pharmaceutical research and discovery due to the central role of these proteins in the regulation of cellular processes. One family of kinases of pharmacological interest, due to its role in activation of immunostimulatory pathways, is the Janus kinase family. Small molecule inhibitors targeting the individual kinase proteins within this family have long been sought-after therapies. High sequence and structural similarity of the family members makes selective inhibitors difficult to identify but critical because of their inter-related multiple cellular regulatory pathways. Herein, we describe the identification of inhibitors of the important Janus kinase, TYK2, a regulator of type I interferon response. In addition, the biochemical and structural confirmation of the direct interaction of these small molecules with the TYK2 pseudokinase domain is described and a potential mechanism of allosteric regulation of TYK2 activity through stabilization of the pseudokinase domain is proposed.

Deucravacitinib in Moderate to Severe Psoriasis: Clinical and Quality-of-Life Outcomes in a Phase 2 Trial

Introduction

Deucravacitinib is an oral, selective tyrosine kinase 2 inhibitor that demonstrated therapeutic benefit in a Phase 2 clinical trial of adults with moderate to severe plaque psoriasis. This analysis was designed to evaluate the effect of deucravacitinib on additional clinical and quality-of-life (QoL) outcomes and assess the relationship between these outcomes in adults with psoriasis.

Methods

Post-hoc analysis of a 12-week Phase 2 trial was conducted for the three most efficacious dosage groups (3 mg twice daily, 6 mg twice daily, 12 mg once daily) and placebo. Investigator assessments for efficacy included Psoriasis Area and Severity Index (PASI), body surface area (BSA) involvement, and static Physician's Global Assessment; QoL was assessed using the Dermatology Life Quality Index (DLQI). Treatment responses and their associations were evaluated over time.

Results

Deucravacitinib elicited improvement versus placebo as early as Week 4 for most efficacy measures (including changes in absolute PASI and BSA), with efficacy trends observed from Week 2 to Week 12. Improvements in QoL, assessed by achievement of a DLQI overall score of 0/1 (no effect at all on patient’s life), followed a pattern similar to deucravacitinib-related clinical outcomes over 12 weeks. Overall, patients with greater improvements in psoriasis-related clinical signs and symptoms also reported greater improvement in QoL. However, complete skin clearance was not required for achieving DLQI 0/1.

Conclusion

Deucravacitinib treatment produced early response and similar trends in improvements across multiple efficacy assessments and QoL in moderate to severe plaque psoriasis. Deucravacitinib has the potential to become a promising new oral therapy for this condition.

Trial Registration

ClinicalTrials.gov identifier; NCT02931838.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13555-021-00649-y.

Psoriasis is a skin disease that affects up to 2% of the population. In psoriasis, red, scaly lesions develop on the skin driven by an aberrant immune response. Psoriasis impacts not only physical and mental health but also quality of life (QoL). Deucravacitinib is being investigated as a treatment for psoriasis. We performed a Phase 2 dose-ranging, placebo-controlled, 12-week study of deucravacitinib in adults with moderate to severe psoriasis. Patients in the USA, Australia, Canada, Germany, Japan, Latvia, Mexico, and Poland participated. The study showed that oral treatment with deucravacitinib was effective using a disease severity score (percentage of patients with ≥ 75% reduction from baseline in Psoriasis Area and Severity Index score) at Week 12—placebo 7% and deucravacitinib 67%–75% for the three highest dosages—and was generally well tolerated. We further analyzed the association between efficacy and a QoL measure, the Dermatology Life Quality Index (DLQI), in patients who received placebo or the most effective dosages of deucravacitinib (≥ 3 mg twice daily). Deucravacitinib was effective at the three dosage levels tested. Skin improvement occurred early during treatment and was mirrored by improvements in DLQI score during the 12 weeks of treatment. Although some patients did not have complete clearance of their psoriasis, a large percentage of those patients still achieved considerable improvement in QoL as measured by achieving a DLQI score of 0/1 (i.e., no effect at all on the patient’s QoL).

Selectivity Profile of the Tyrosine Kinase 2 Inhibitor Deucravacitinib Compared with Janus Kinase 1/2/3 Inhibitors

INTRODUCTION

Deucravacitinib, a novel, oral, selective inhibitor of tyrosine kinase 2 (TYK2) signaling, acts via an allosteric mechanism by binding to the enzyme's regulatory domain instead of the catalytic domain. This unique binding provides high functional selectivity for TYK2 versus the closely related Janus kinases (JAKs) 1/2/3. Deucravacitinib was efficacious in phase 2 and 3 psoriasis trials, without clinical or laboratory parameters indicative of JAK 1/2/3 inhibition being observed. This analysis compared the kinase specificities of deucravacitinib versus JAK 1/2/3 inhibitors at therapeutic exposures.

METHODS

Signaling via JAK 1/3, JAK 2/2, and TYK2/JAK 2 dimers was measured in in vitro whole blood assays. Concentrations providing half-maximal inhibition (IC₅₀) in these assays were determined for deucravacitinib and the JAK 1/2/3 inhibitors tofacitinib, upadacitinib, and baricitinib. Newly derived whole blood IC₅₀ values were plotted against available pharmacokinetic profiles using doses evaluated in phase 2/3 trials. Simulated average daily inhibition and durations over which concentrations exceeded IC₅₀ were evaluated.

RESULTS

At clinically relevant exposures, projected steady-state deucravacitinib plasma concentrations were higher than TYK2 IC₅₀ for approximately 9-18 h. Maximal plasma concentrations (C_max) of deucravacitinib were 8- to 17-fold lower than JAK 1/3 IC₅₀ and > 48- to > 102-fold lower than JAK 2/2 IC₅₀. Simulated daily average TYK2 inhibition by deucravacitinib ranged from 50% to 69%. Simulations indicated that tofacitinib, upadacitinib, and baricitinib at steady state exhibited varying degrees of JAK 1/3 (daily average inhibition, 70-94%) and JAK 2/2 (23%-67%) inhibition at therapeutic concentrations, with C_max values 17- to 33-fold lower than their TYK2 IC₅₀ levels.

CONCLUSION

At clinically relevant doses and exposures, deucravacitinib demonstrates highly selective inhibition of TYK2 and not JAK 1/2/3. Tofacitinib, upadacitinib, and baricitinib variably inhibit JAK 1/2/3 but not TYK2. These results indicate that deucravacitinib is a distinct class of kinase inhibitor compared with JAK 1/2/3 inhibitors.

TYK2 in Cancer Metastases: Genomic and Proteomic Discovery

Simple Summary

Cancer deaths are predominantly due to metastases rather than the primary tumors, and thus there is an urgent need for the discovery of more effective drug therapies for metastatic cancer. Recent genomics, transcriptomics, and proteomics studies have identified tyrosine kinase 2 (TYK2) as an oncogene that is frequently mutated or overexpressed in many types of cancer and metastases. A member of the Janus kinase (JAK) family, TYK2 mediates the signals of numerous cytokines involved in immune and inflammatory signaling. In cancer cells, activation of TYK2 can lead to decreased cell death as well as increased cell growth and invasion. Multiple drugs that specifically block TYK2 or JAKs are currently FDA-approved or in clinical trials. In this review, we provide an overview of the screening, molecular, and animal studies that have characterized the role of TYK2 in cancer and metastases, and the potential of TYK2 inhibitors as effective cancer therapies.

Abstract

Advances in genomic analysis and proteomic tools have rapidly expanded identification of biomarkers and molecular targets important to cancer development and metastasis. On an individual basis, personalized medicine approaches allow better characterization of tumors and patient prognosis, leading to more targeted treatments by detection of specific gene mutations, overexpression, or activity. Genomic and proteomic screens by our lab and others have revealed tyrosine kinase 2 (TYK2) as an oncogene promoting progression and metastases of many types of carcinomas, sarcomas, and hematologic cancers. TYK2 is a Janus kinase (JAK) that acts as an intermediary between cytokine receptors and STAT transcription factors. TYK2 signals to stimulate proliferation and metastasis while inhibiting apoptosis of cancer cells. This review focuses on the growing evidence from genomic and proteomic screens, as well as molecular studies that link TYK2 to cancer prevalence, prognosis, and metastasis. In addition, pharmacological inhibition of TYK2 is currently used clinically for autoimmune diseases, and now provides promising treatment modalities as effective therapeutic agents against multiple types of cancer.

Hypotheses and facts for genetic factors related to severe COVID-19

Genome-wide association analysis allows the identification of potential candidate genes involved in the development of severe coronavirus disease 2019 (COVID-19). Hence, it seems that genetics matters here, as well. Nevertheless, the virus's nature, including its RNA structure, determines the rate of mutations leading to new viral strains with all epidemiological and clinical consequences. Given these observations, we herein comment on the current hypotheses about the possible role of the genes in association with COVID-19 severity. We discuss some of the major candidate genes that have been identified as potential genetic factors associated with the COVID-19 severity and infection susceptibility: HLA, ABO, ACE2, TLR7, ApoE, TYK2, OAS, DPP9, IFNAR2, CCR2, etc. Further study of genes and genetic variants will be of great benefit for the prevention and assessment of the individual risk and disease severity in different populations. These scientific data will serve as a basis for the development of clinically applicable diagnostic and prognostic tests for patients at high risk of COVID-19.

TYK2 as a therapeutic target in the treatment of autoimmune and inflammatory diseases

JAKs are intracellular protein tyrosine kinases that, through activation of STATs, are responsible for signal transduction pathways that regulate cellular responses to numerous cytokines, growth factors and hormones in many different cells. JAK-STAT signaling plays a key role in regulating immune function, and cytokines - such as IL-23, IL-12 and type I interferons - are central to the pathogenesis of autoimmune diseases, including psoriasis, inflammatory bowel disease and systemic lupus erythematosus. Here the authors review the evidence for targeting TYK2 as a more specific approach to treating these conditions. TYK2 inhibitors are clinically effective in autoimmune and inflammatory diseases and may avoid some of the complications reported with nonselective JAK inhibitors.

From Science to Success? Targeting Tyrosine Kinase 2 in Spondyloarthritis and Related Chronic Inflammatory Diseases

Spondyloarthritis (SpA) is a family of inflammatory arthritic diseases, which includes the prototypes of psoriatic arthritis and ankylosing spondylitis. SpA is commonly associated with systemic inflammatory diseases, such as psoriasis and inflammatory bowel disease. Immunological studies, murine models and the genetics of SpA all indicate a pathogenic role for the IL-23/IL-17 axis. Therapeutics targeting the IL-23/IL-17 pathway are successful at providing symptomatic relief, but may not provide complete protection against progression of arthritis. Thus there is still tremendous interest in the discovery of novel therapeutic targets for SpA. Tyrosine kinase 2 (TYK2) is a member of the Janus kinases, which mediate intracellular signaling of cytokines via signal transducer and activator of transcription (STAT) activation. TYK2 plays a crucial role in mediating IL-23 receptor signaling and STAT3 activation. A plethora of natural mutations in and around TYK2 have provided a wealth of data to associate this kinase with autoimmune/autoinflammatory diseases in humans. Induced and natural mutations in murine Tyk2 largely support human data; however, key inter-species differences exist, which means extrapolation of data from murine models to humans needs to be done with caution. Despite these reservations, novel selective TYK2 inhibitors are now proving successful in advanced clinical trials of inflammatory diseases. In this review, we will discuss TYK2 from basic biology to therapeutic targeting, with an emphasis on studies in SpA. Seminal studies uncovering the basic science of TYK2 have provided sound foundations for targeting it in SpA and related inflammatory diseases. TYK2 inhibitors may well be the next blockbuster therapeutic for SpA.

Tyrosine kinase 2 and Janus kinase‒signal transducer and activator of transcription signaling and inhibition in plaque psoriasis

Plaque psoriasis is a common, chronic, systemic, immune-mediated inflammatory disease. The Janus kinase-signal transducer and activator of transcription pathway plays a major role in intracellular cytokine signaling in inflammatory processes involved in psoriasis. Although Janus kinase (JAK) 1-3 inhibitors have demonstrated efficacy in patients with moderate-to-severe psoriasis, safety concerns persist and no JAK inhibitor has received regulatory approval to treat psoriasis. Thus, an opportunity exists for novel oral therapies that are safe and efficacious in psoriasis. Tyrosine kinase 2 (TYK2) is a member of the JAK family of kinases and regulates signaling and functional responses downstream of the interleukin 12, interleukin 23, and type I interferon receptors. Deucravacitinib, which is an oral, selective inhibitor that binds to the regulatory domain of TYK2, and brepocitinib (PF-06700841) and PF-06826647, which are topical and oral TYK2 inhibitors, respectively, that bind to the active (adenosine triphosphate-binding) site in the catalytic domain, are in development for psoriasis. Selective, allosteric inhibition of TYK2 signaling may reduce the potential for toxicities associated with pan-JAK inhibitors. This article reviews Janus kinase-signal transducer and activator of transcription and TYK2 signaling and the efficacy and safety of JAK inhibitors in psoriasis to date, focusing specifically on TYK2 inhibitors.

A Missense Mutation rs781536408 (c.2395G>A) of TYK2 Affects Splicing and Causes Skipping of Exon18 in vivo

TYK2 variants can impact disease onset or progression. In our previous study, we identified abnormal splicing that happened near rs781536408 in the TYK2 gene. The purpose of this research was to examine the effect of the mutation on alternative splicing in vivo and in vitro. Whole exome sequencing was performed to identify the mutations followed by bidirectional Sanger sequencing. Then the minigene analysis was carried out based on HeLa and HEK293T cell lines. The results showed that rs781536408 (c.2395G>A, p.G799R) was homozygous in the patient, but heterozygous in parents. PCR amplification confirmed the abnormal splicing in the somatic cells of the patients, but not in the parents. Sanger sequencing results showed that there was a skipping of exon18 near the mutation. For minigene analysis, there was no difference between the wild-type and the mutant type in the two minigene construction strategies, indicating that mutation c.2395G>A had no effect on splicing in vitro. Combining the results of in vivo, we speculated that the effect of the mutation on splicing was not absolute, but rather in degree.

TYK2 is a prognostic biomarker and associated with immune infiltration in the lung adenocarcinoma microenvironment

BACKGROUND

Lung adenocarcinoma (LUAD) remains a major disease with high morbidity and mortality. The Janus kinases (JAKs) play a significant part in cellular biological process, inflammation and immunity. The role of JAK family in LUAD is still ambiguous.

METHODS

Various bioinformatics web portals were applied to explore the prognostic value of JAK family and their correlation with immune infiltration in LUAD.

RESULTS

JAK1/2 was downregulated, whereas JAK3/TYK2 was upregulated in patients with LUAD compared with the healthy controls in subgroup analyses based on gender, age, smoking habits, cancer stage, TP53 mutation status, and nodal metastasis status. Drug sensitivity indicated that low expression of JAK3 and TYK2 were resistant to most of the small molecules or drugs. High TYK2 expression was associated with favorable overall survival and relapse free survival in LUAD. Moreover, univariate and multivariate analysis revealed that clinical stage, lymphatic node metastasis and TYK2 expression were the independent factors affecting the prognosis of LUAD patients. TYK2 expression in LUAD patients was positively associated with the abundance of immune cells (B cells, CD8+ T cells, CD4+ T cells, neutrophils, and dendritic cells) and immune biomarker sets. Moreover, TYK2 was mainly involved in RNA binding, transcriptional mis-regulation in cancer and cell cycles. We also identified several TYK2-associated miRNA or transcription factor targets in LUAD.

CONCLUSION

Our results indicated that TYK2 was a biomarker and associated with prognosis and immune infiltration in LUAD, laying a foundation for further study about the role of TYK2 in the carcinogenesis and progression of LUAD.

Cirsiliol targets tyrosine kinase 2 to inhibit esophageal squamous cell carcinoma growth in vitro and in vivo

Background

Esophageal squamous cell carcinoma (ESCC) is an aggressive and lethal cancer with a low 5 year survival rate. Identification of new therapeutic targets and its inhibitors remain essential for ESCC prevention and treatment.

Methods

TYK2 protein levels were checked by immunohistochemistry. The function of TYK2 in cell proliferation was investigated by MTT [(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] and anchorage-independent cell growth. Computer docking, pull-down assay, surface plasmon resonance, and kinase assay were used to confirm the binding and inhibition of TYK2 by cirsiliol. Cell proliferation, western blot and patient-derived xenograft tumor model were used to determine the inhibitory effects and mechanism of cirsiliol in ESCC.

Results

TYK2 was overexpressed and served as an oncogene in ESCC. Cirsiliol could bind with TYK2 and inhibit its activity, thereby decreasing dimer formation and nucleus localization of signal transducer and activator of transcription 3 (STAT3). Cirsiliol could inhibit ESCC growth in vitro and in vivo.

Conclusions

TYK2 is a potential target in ESCC, and cirsiliol could inhibit ESCC by suppression of TYK2.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-021-01903-z.

Molecular cloning and functional characterization of duck TYK2

Tyrosine kinase 2 (TYK2), a member of Janus kinase family, has been identified as a crucial protein in signal transduction initiated by interferons or interleukins in mammals. However, the function of avian TYK2 in innate immune response remains largely unknown. In this study, the full-length duck TYK2 (duTYK2) cDNA was cloned for the first time, which encoded a putative protein of 1187 amino acid residues and showed the high sequence similarity with bald eagle, crested ibis, and white-tailed tropicbird TYK2s. The duTYK2 was widely expressed in all examined tissues of healthy ducks and showed diffuse cytoplasmic localization in duck embryo fibroblasts (DEFs). Overexpression of duTYK2 significantly enhanced ISRE promoter activity and induced the expression of viperin, PKR, 2',5'-OAS, Mx and ZAP in DEFs. The C-terminal kinase domain of duTYK2 is essential for duTYK2-mediated ISRE promoter activation. Furthermore, knockdown of duTYK2 dramatically decreased duck Tembusu virus (DTMUV)-, duck enteritis virus (DEV)-, poly(I:C)- or poly(dA:dT)-induced ISRE promoter activation. Additionally, duTYK2 expression exhibited antiviral activity against DTMUV. These results indicated that duTYK2 played a critical role in duck antiviral innate immunity.

Expression patterns of three JAK-STAT pathway genes in feather follicle development during chicken embryogenesis

The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) (JAK-STAT) pathway is shown to restrain the hair follicles in catagen and telogen and prevent anagen reentry in murine hair follicle cycling. The early roles of JAK-STAT pathway genes in skin development remain uncharacterized in mouse and chicken models. Here, we revealed the expression patterns of three JAK-STAT pathway genes (JAK1, JAK2, and TYK2) in chicken embryonic skin at E6-E10 stages which are key to feather follicle morphogenesis. Multiple sequence alignment of the three genes from chicken and other species all showed a closely related homology with birds like quail and goose. Whole mount in situ hybridization (WISH) revealed weak expression of JAK1, JAK2, and TYK2 in chicken skin at E6 and E7, and followed with the focally restricted signals in the feather follicles of neck and body skin located dorsally at E8 for JAK1, E9 for TYK2 and E10 for JAK2 gene. All three genes displayed stronger expression in feather follicles of neck skin than that of body skin. The expression levels of JAK1 and TYK2 were much stronger than those of JAK2. Quantitative real-time PCR (qRT-PCR) analysis revealed the increased expression tendency for JAK2 both in the neck and body skin from E6 to E10, and the much stronger expression in neck and body skin at later stages (E8-E10) than earlier stages (E6 and E7) for JAK1 and TYK2. Overall, these findings suggest that JAK1 and TYK2, not JAK2 are important to specify the feather follicle primordia, and to arrange the proximal-distal axis of feather follicles, respectively, during the morphogenesis of feather follicles in embryonic chicken skin.

Respirovirus C protein inhibits activation of type I interferon receptor-associated kinases to block JAK-STAT signaling

Respirovirus C protein blocks the type I interferon (IFN)-stimulated activation of the JAK-STAT pathway. It has been reported that C protein inhibits IFN-α-stimulated tyrosine phosphorylation of STATs, but the underlying mechanism is poorly understood. Here, we show that the C protein of Sendai virus (SeV), a member of the Respirovirus genus, binds to the IFN receptor subunit IFN-α/β receptor subunit (IFNAR)2 and inhibits IFN-α-stimulated tyrosine phosphorylation of the upstream receptor-associated kinases, JAK1 and TYK2. Analysis of various SeV C mutant (Cm) proteins demonstrates the importance of the inhibitory effect on receptor-associated kinase phosphorylation for blockade of JAK-STAT signaling. Furthermore, this inhibitory effect and the IFNAR2 binding capacity are observed for all the respirovirus C proteins examined. Our results suggest that respirovirus C protein inhibits activation of the receptor-associated kinases JAK1 and TYK2 possibly through interaction with IFNAR2.

Equid Herpesvirus 1 Targets the Sensitization and Induction Steps To Inhibit the Type I Interferon Response in Equine Endothelial Cells

Equid herpesvirus 1 (EHV-1) is a viral pathogen of horse populations worldwide spread by the respiratory route and is known for causing outbreaks of neurologic syndromes and abortion storms. Previously, we demonstrated that an EHV-1 strain of the neuropathogenic genotype, T953, downregulates the beta interferon (IFN-β) response in vitro in equine endothelial cells (EECs) at 12 h postinfection (hpi). In the present study, we explored the molecular correlates of this inhibition as clues toward an understanding of the mechanism. Data from our study revealed that EHV-1 infection of EECs significantly reduced both Toll-like receptor 3 (TLR3) and TLR4 mRNA expression at 6 hpi and 12 hpi. While EHV-1 was able to significantly reduce IRF9 mRNA at both 6 hpi and 12 hpi, the virus significantly reduced IFN regulatory factor 7 (IRF7) mRNA only at 12 hpi. EHV-1 did not alter the cellular level of Janus-activated kinase 1 (JAK1) at any time point. However, EHV-1 reduced the cellular level of expression of tyrosine kinase 2 (TYK2) at 12 hpi. Downstream of JAK1-TYK2 signaling, EHV-1 blocked the phosphorylation and activation of signal transducer and activator of transcription 2 (STAT2) when coincubated with exogenous IFN, at 12 hpi, although not at 3 or 6 hpi. Immunofluorescence staining revealed that the virus prevented the nuclear translocation of STAT2 molecules, confirming the virus-mediated inhibition of STAT2 activation. The pattern of suppression of phosphorylation of STAT2 by EHV-1 implicated viral late gene expression. These data help illuminate how EHV-1 strategically inhibits the host innate immune defense by limiting steps required for type I IFN sensitization and induction.IMPORTANCE To date, no commercial vaccine label has a claim to be fully protective against the diseases caused by equid herpesvirus 1 (EHV-1), especially the neurologic form. The interferon (IFN) system, of which type I IFN is of great importance, still remains a viable immunotherapeutic option against EHV-1 infection. The type I IFN system has been exploited successfully to treat other viral infections, such as chronic hepatitis B and C in humans. The current state of research on how EHV-1 interferes with the protective effect of type I IFN has indicated transient induction of type I IFN production followed by a rapid shutdown in vitro in equine endothelial cells (EECs). The significance of our study is the identification of certain steps in the type I IFN signaling pathway targeted for inhibition by EHV-1. Understanding this pathogen-host relationship is essential for the long-term goal of developing effective immunotherapy against EHV-1.

TYK2 promotes malignant peripheral nerve sheath tumor progression through inhibition of cell death

Background

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas that arise most commonly in the setting of the Neurofibromatosis Type 1 (NF1) cancer predisposition syndrome. Despite aggressive multimodality therapy, outcomes are dismal and most patients die within 5 years of diagnosis. Prior genomic studies in our laboratory identified tyrosine kinase 2 (TYK2) as a frequently mutated gene in MPNST. Herein, we explored the function of TYK2 in MPNST pathogenesis.

Methods

Immunohistochemistry was utilized to examine expression of TYK2 in MPNSTs and other sarcomas. To establish a role for TYK2 in MPNST pathogenesis, murine and human TYK2 knockdown and knockout cells were established using shRNA and CRISPR/Cas9 systems, respectively.

Results

We have demonstrated that TYK2 was highly expressed in the majority of human MPNSTs examined. Additionally, we demonstrated that knockdown of Tyk2/TYK2 in murine and human MPNST cells significantly increased cell death in vitro. These effects were accompanied by a decrease in the levels of activated Stats and Bcl‐2 as well as an increase in the levels of Cleaved Caspase‐3. In addition, Tyk2‐KD cells demonstrated impaired growth in subcutaneous and metastasis models in vivo.

Conclusion

Taken together, these data illustrate the importance of TYK2 in MPNST pathogenesis and suggest that the TYK2 pathway may be a potential therapeutic target for these deadly cancers.

Di (2-ethylhexyl) phthalate Disorders Lipid Metabolism via TYK2/STAT1 and Autophagy in Rats

OBJECTIVE

Previous studies have indicated that the plasticizer di (2-ethylhexyl) phthalate (DEHP) affects lipid accumulation; however, its underlying mechanism remains unclear. We aim to clarify the effect of DEHP on lipid metabolism and the role of TYK2/STAT1 and autophagy.

METHODS

In total, 160 Wistar rats were exposed to DEHP [0, 5, 50, 500 mg/(kg•d)] for 8 weeks. Lipid levels, as well as mRNA and protein levels of TYK2, STAT1, PPARγ, AOX, FAS, LPL, and LC3 were detected.

RESULTS

The results indicate that DEHP exposure may lead to increased weight gain and altered serum lipids. We observed that DEHP exposure affected liver parenchyma and increased the volume or number of fat cells. In adipose tissue, decreased TYK2 and STAT1 promoted the expression of PPARγ and FAS. The mRNA and protein expression of LC3 in 50 and 500 mg/(kg•d) groups was increased significantly. In the liver, TYK2 and STAT1 increased compensatorily; however, the expression of FAS and AOX increased, while LPL expression decreased. Joint exposure to both a high-fat diet and DEHP led to complete disorder of lipid metabolism.

CONCLUSION

It is suggested that DEHP induces lipid metabolism disorder by regulating TYK2/STAT1. Autophagy may play a potential role in this process as well. High-fat diet, in combination with DEHP exposure, may jointly have an effect on lipid metabolism disorder.

Identification of rare coding variants in TYK2 protective for rheumatoid arthritis in the Japanese population and their effects on cytokine signalling

OBJECTIVE

Although genome-wide association studies (GWAS) have identified approximately 100 loci for rheumatoid arthritis (RA), the disease mechanisms are not completely understood. We evaluated the pathogenesis of RA by focusing on rare coding variants.

METHODS

The coding regions of 98 candidate genes identified by GWAS were sequenced in 2294 patients with RA and 4461 controls in Japan. An association analysis was performed using cases and controls for variants, genes and domains of TYK2. Cytokine responses for two associated variants (R231W, rs201917359; and R703W, rs55882956) in TYK2 as well as a previously reported risk variant (P1004A, rs34536443) for multiple autoimmune diseases were evaluated by reporter assays.

RESULTS

A variant in TYK2 (R703W) showed a suggestive association (p=5.47×10^-8, OR=0.48). We observed more accumulation of rare coding variants in controls in TYK2 (p=3.94×10^-12, OR=0.56). The four-point-one, ezrin, radixin, moesin (FERM; 2.14×10^-3, OR=0.66) and pseudokinase domains (1.63×10^-8, OR=0.52) of TYK2 also showed enrichment of variants in controls. R231W in FERM domain especially reduced interleukin (IL)-6 and interferon (IFN)-γ signalling, whereas P1104A in kinase domain reduced IL-12, IL-23 and IFN-α signalling. R703W in pseudokinase domain reduced cytokine signals similarly to P1104A, but the effects were weaker than those of P1104A.

CONCLUSIONS

The FERM and pseudokinase domains in TYK2 were associated with the risk of RA in the Japanese population. Variants in TYK2 had different effects on cytokine signalling, suggesting that the regulation of selective cytokine signalling is a target for RA treatment.

Homozygosity for TYK2 P1104A underlies tuberculosis in about 1% of patients in a cohort of European ancestry

The human genetic basis of tuberculosis (TB) has long remained elusive. We recently reported a high level of enrichment in homozygosity for the common TYK2 P1104A variant in a heterogeneous cohort of patients with TB from non-European countries in which TB is endemic. This variant is homozygous in ∼1/600 Europeans and ∼1/5,000 people from other countries outside East Asia and sub-Saharan Africa. We report a study of this variant in the UK Biobank cohort. The frequency of P1104A homozygotes was much higher in patients with TB (6/620, 1%) than in controls (228/114,473, 0.2%), with an odds ratio (OR) adjusted for ancestry of 5.0 [95% confidence interval (CI): 1.96-10.31, P = 2 × 10-3]. Conversely, we did not observe enrichment for P1104A heterozygosity, or for TYK2 I684S or V362F homozygosity or heterozygosity. Moreover, it is unlikely that more than 10% of controls were infected with Mycobacterium tuberculosis, as 97% were of European genetic ancestry, born between 1939 and 1970, and resided in the United Kingdom. Had all of them been infected, the OR for developing TB upon infection would be higher. These findings suggest that homozygosity for TYK2 P1104A may account for ∼1% of TB cases in Europeans.

The TYK2-P1104A Autoimmune Protective Variant Limits Coordinate Signals Required to Generate Specialized T Cell Subsets

TYK2 is a JAK family member that functions downstream of multiple cytokine receptors. Genome wide association studies have linked a SNP (rs34536443) within TYK2 encoding a Proline to Alanine substitution at amino acid 1104, to protection from multiple autoimmune diseases including systemic lupus erythematosus (SLE) and multiple sclerosis (MS). The protective role of this SNP in autoimmune pathogenesis, however, remains incompletely understood. Here we found that T follicular helper (Tfh) cells, switched memory B cells, and IFNAR signaling were decreased in healthy individuals that expressed the protective variant TYK2 ^A1104 (TYK2 ^P ). To study this variant in vivo, we developed a knock-in murine model of this allele. Murine Tyk2 ^P expressing T cells homozygous for the protective allele, but not cells heterozygous for this change, manifest decreased IL-12 receptor signaling, important for Tfh lineage commitment. Further, homozygous Tyk2 ^P T cells exhibited diminished in vitro Th1 skewing. Surprisingly, despite these signaling changes, in vivo formation of Tfh and GC B cells was unaffected in two models of T cell dependent immune responses and in two alternative SLE models. TYK2 is also activated downstream of IL-23 receptor engagement. Here, we found that Tyk2 ^P expressing T cells had reduced IL-23 dependent signaling as well as a diminished ability to skew toward Th17 in vitro. Consistent with these findings, homozygous, but not heterozygous, Tyk2 ^P mice were fully protected in a murine model of MS. Homozygous Tyk2 ^P mice had fewer infiltrating CD4⁺ T cells within the CNS. Most strikingly, homozygous mice had a decreased proportion of IL-17⁺/IFNγ⁺, double positive, pathogenic CD4⁺ T cells in both the draining lymph nodes (LN) and CNS. Thus, in an autoimmune model, such as EAE, impacted by both altered Th1 and Th17 signaling, the Tyk2 ^P allele can effectively shield animals from disease. Taken together, our findings suggest that TYK2^P diminishes IL-12, IL-23, and IFN I signaling and that its protective effect is most likely manifest in the setting of autoimmune triggers that concurrently dysregulate at least two of these important signaling cascades.

Evidence for association of STAT4 and IL12RB2 variants with Myasthenia gravis susceptibility: What is the effect on gene expression in thymus?

Myasthenia gravis (MG) is an autoimmune disease mediated by the presence of autoantibodies that bind mainly to the acetylcholine receptor (AChR) in the neuromuscular junction. In our case-control association study, we analyzed common variants located in genes of the IL12/STAT4 and IL10/STAT3 signaling pathways. A total of 175 sporadic MG patients of Greek descent, positively detected with anti-AChR autoantibodies and 84 ethnically-matched, healthy volunteers were enrolled in the study. Thymus samples were obtained from 16 non-MG individuals for relative gene expression analysis. The strongest signals of association were observed in the cases of rs6679356 between the late-onset MG patients and controls and rs7574865 between early-onset MG and controls. Our investigation of the correlation between the MG-associated variants and the expression levels of each gene in thymus did not result in significant differences.

Down-regulation of TYK2, CBLB and LMP7 genes expression in relapsing-remitting multiple sclerosis patients treated with interferon-beta

This study aimed to examine the expression of TYK2, CBLB and LMP7 genes at both mRNA and protein levels in relapsing-remitting MS (RRMS) patients in compare with healthy controls. Seventy-eight RRMS patients treated with IFNβ-1a and 79 age- and ethnic-matched healthy subjects were studied. The mRNA expression levels of TYK2, CBLB and LMP7 in PBMCs were quantified by real-time PCR and plasma concentrations of three molecules were measured by ELISA. Results were compared between patients and controls, IFNβ-responders and non-responders. Forty-nine of 78 patients were classified as IFNβ-responders and 29 cases were non-responders. Significantly down-regulated expression of TYK2, CBLB and LMP7 genes was found in the patients group versus controls (P<0.001). Decreased plasma levels of three molecules were observed in patients compared to controls (P<0.001). IFNβ-responders had significantly higher expressions for CBLB (P=0.001) and LMP7 (P=0.02) than non-responders. Also, we observed increased expressions of LMP7 (P=0.39) and CBLB (P=0.02) genes in patients under 30y and increased expression of TYK2 in patients >40years (P=0.002). Our results suggest that expression analysis of TYK2, CBLB and LMP7 genes could be useful for evaluation of T cells immunity and clinical response to IFNβ-therapy in RRMS patients.