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Introduction: This post hoc analysis evaluated influenza adverse events (AEs) across rheumatoid arthritis (RA), ulcerative colitis (UC), and psoriatic arthritis (PsA) tofacitinib clinical programs. Methods: Available data from phase 1, randomized phase 2/3/3b/4 clinical trials (completed by 2018), and long-term extension (LTE) studies (up to May 2019) in patients with RA, UC, and PsA were included [randomized or Overall (phase 1-3b/4 and LTE studies) tofacitinib cohorts]. Incidence rates (IRs; events per 100 patient-years) of combined influenza AEs (seasons 2004/2005 to 2018/2019) were analyzed, including by tofacitinib dose [5 or 10 mg twice daily (BID)] and age (< 65 versus >= 65 years). Logistic regression models evaluated risk factors for influenza AEs in the RA Overall tofacitinib cohort. Results: In randomized cohorts, combined influenza AE IRs were generally similar across tofacitinib, adalimumab, methotrexate, and placebo groups, across indications. Among Overall tofacitinib cohorts, combined influenza AE IRs with tofacitinib 5/10 mg BID, respectively, were higher in the UC (3.66/5.09) versus RA (2.38/2.19) and PsA (1.74/1.29) cohorts. IRs were generally similar across tofacitinib dose and age groups. Most influenza AEs were nonserious and did not require changes to tofacitinib treatment. Significant risk factors for influenza AEs in patients with RA were geographic region, baseline oral corticosteroid and methotrexate use, and tofacitinib dose. Conclusions: In the RA, UC, and PsA clinical programs, combined influenza AE IRs were highest in UC, while in each indication they were generally similar across tofacitinib, placebo, and comparator groups. Influenza AEs were predominantly nonserious and not associated with changes to tofacitinib treatment.

Purpose; The aim of this study was to characterize clinical effects and biomarkers in three patients with chronic mucocutaneous candidiasis (CMC) caused by gain-of-function (GOF) mutations in the STAT1 gene during treatment with Janus kinase (JAK) inhibitors. Methods: Mass cytometry (CyTOF) was used to characterize mononuclear leukocyte populations and Olink assay to quantify 265 plasma proteins. Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) was used to quantify the reactivity against Candida albicans. Results: Overall, JAK inhibitors improved clinical symptoms of CMC, but caused side effects in two patients. Absolute numbers of neutrophils, T cells, B cells, and NK cells were sustained during baricitinib treatment. Detailed analysis of cellular subsets, using CyTOF, revealed increased expression of CD45, CD52, and CD99 in NK cells, reflecting a more functional phenotype. Conversely, monocytes and eosinophils downregulated CD16, consistent with reduced inflammation. Moreover, T and B cells showed increased expression of activation markers during treatment. In one patient with a remarkable clinical effect of baricitinib treatment, the immune response to C. albicans increased after 7 weeks of treatment. Alterations in plasma biomarkers involved downregulation of cellular markers CXCL10, annexin A1, granzyme B, granzyme H, and oncostatin M, whereas FGF21 was the only upregulated marker after 7 weeks. After 3 months, IFN-gamma and CXCL10 were downregulated. Conclusions: The clinical effect of JAK inhibitor treatment of CMC is promising. Several biological variables were altered during baricitinib treatment demonstrating that lymphocytes, NK cells, monocytes, and eosinophils were affected. In parallel, cellular reactivity against C. albicans was enhanced.

Hyperactive mutation V617F in the JAK2 regulatory pseudokinase domain (JH2) is prevalent in patients with myeloproliferative neoplasms. Here, we identified novel small molecules that target JH2 of JAK2 V617F and characterized binding via biochemical and structural approaches. Screening of 107,600 small molecules resulted in identification of 55 binders to the ATP-binding pocket of recombinant JAK2 JH2 V617F protein at a low hit rate of 0.05%, which indicates unique structural characteristics of the JAK2 JH2 ATP-binding pocket. Selected hits and structural analogs were further assessed for binding to JH2 and JH1 (kinase) domains of JAK family members (JAK1-3, TYK2) and for effects on MPN model cell viability. Crystal structures were determined with JAK2 JH2 wild-type and V617F. The JH2-selective binders were identified in diaminotriazole, diaminotriazine, and phenylpyrazolo-pyrimidone chemical entities, but they showed low-affinity, and no inhibition of MPN cells was detected, while compounds binding to both JAK2 JH1 and JH2 domains inhibited MPN cell viability. X-ray crystal structures of protein-ligand complexes indicated generally similar binding modes between the ligands and V617F or wild-type JAK2. Ligands of JAK2 JH2 V617F are applicable as probes in JAK-STAT research, and SAR optimization combined with structural insights may yield higher-affinity inhibitors with biological activity.

Background:Administration of Janus kinase (JAK) inhibitors and biological disease-modifying antirheumatic drugs has dramatically improved even the clinical outcomes in patients with rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX). Dysregulation of JAK-STAT pathways via overproduction of cytokines, such as interleukin-6, is involved in the pathogenesis of RA. Filgotinib is a selective JAK1 inhibitor pending approval for use in RA. By inhibition of the JAK-STAT pathway, filgotinib is effective in suppressing disease activity and preventing the progression of joint destruction. Similarly, interleukin-6 inhibitors such as tocilizumab also inhibit the JAK-STAT pathways by inhibition of interleukin-6 signaling. We present the protocol for a study that will evaluate whether the effectiveness of filgotinib monotherapy is non-inferior to that of tocilizumab monotherapy in RA patients with an inadequate response to MTX. Methods:This study is an interventional, multicenter, randomized, open-label, parallel-group, and non-inferiority clinical trial with a 52-week follow-up. Study participants will be 400 RA patients with at least moderate disease activity during treatment with MTX. Participants will be randomized in a 1:1 ratio to administer filgotinib monotherapy or subcutaneous tocilizumab monotherapy switched from MTX. We will evaluate disease activity by measuring clinical disease activity indices and by using musculoskeletal ultrasound (MSUS). The primary endpoint is the proportion of patients who achieve an American College of Rheumatology 50 response at week 12. Secondary endpoints are changes from baseline in the MSUS scores. We will also comprehensively analyze serum levels of multiple biomarkers, such as cytokines and chemokines. Discussion:The study results are expected to show the non-inferiority of the effectiveness of filgotinib monotherapy to that of tocilizumab monotherapy in RA patients with inadequate response to MTX. The strength of, Trials, 24(1), art. no. 161; 2023

Introduction: This post hoc analysis evaluated influenza adverse events (AEs) across rheumatoid arthritis (RA), ulcerative colitis (UC), and psoriatic arthritis (PsA) tofacitinib clinical programs. Methods: Available data from phase 1, randomized phase 2/3/3b/4 clinical trials (completed by 2018), and long-term extension (LTE) studies (up to May 2019) in patients with RA, UC, and PsA were included [randomized or Overall (phase 1-3b/4 and LTE studies) tofacitinib cohorts]. Incidence rates (IRs; events per 100 patient-years) of combined influenza AEs (seasons 2004/2005 to 2018/2019) were analyzed, including by tofacitinib dose [5 or 10 mg twice daily (BID)] and age (< 65 versus >= 65 years). Logistic regression models evaluated risk factors for influenza AEs in the RA Overall tofacitinib cohort. Results: In randomized cohorts, combined influenza AE IRs were generally similar across tofacitinib, adalimumab, methotrexate, and placebo groups, across indications. Among Overall tofacitinib cohorts, combined influenza AE IRs with tofacitinib 5/10 mg BID, respectively, were higher in the UC (3.66/5.09) versus RA (2.38/2.19) and PsA (1.74/1.29) cohorts. IRs were generally similar across tofacitinib dose and age groups. Most influenza AEs were nonserious and did not require changes to tofacitinib treatment. Significant risk factors for influenza AEs in patients with RA were geographic region, baseline oral corticosteroid and methotrexate use, and tofacitinib dose. Conclusions: In the RA, UC, and PsA clinical programs, combined influenza AE IRs were highest in UC, while in each indication they were generally similar across tofacitinib, placebo, and comparator groups. Influenza AEs were predominantly nonserious and not associated with changes to tofacitinib treatment.

Purpose; The aim of this study was to characterize clinical effects and biomarkers in three patients with chronic mucocutaneous candidiasis (CMC) caused by gain-of-function (GOF) mutations in the STAT1 gene during treatment with Janus kinase (JAK) inhibitors. Methods: Mass cytometry (CyTOF) was used to characterize mononuclear leukocyte populations and Olink assay to quantify 265 plasma proteins. Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) was used to quantify the reactivity against Candida albicans. Results: Overall, JAK inhibitors improved clinical symptoms of CMC, but caused side effects in two patients. Absolute numbers of neutrophils, T cells, B cells, and NK cells were sustained during baricitinib treatment. Detailed analysis of cellular subsets, using CyTOF, revealed increased expression of CD45, CD52, and CD99 in NK cells, reflecting a more functional phenotype. Conversely, monocytes and eosinophils downregulated CD16, consistent with reduced inflammation. Moreover, T and B cells showed increased expression of activation markers during treatment. In one patient with a remarkable clinical effect of baricitinib treatment, the immune response to C. albicans increased after 7 weeks of treatment. Alterations in plasma biomarkers involved downregulation of cellular markers CXCL10, annexin A1, granzyme B, granzyme H, and oncostatin M, whereas FGF21 was the only upregulated marker after 7 weeks. After 3 months, IFN-gamma and CXCL10 were downregulated. Conclusions: The clinical effect of JAK inhibitor treatment of CMC is promising. Several biological variables were altered during baricitinib treatment demonstrating that lymphocytes, NK cells, monocytes, and eosinophils were affected. In parallel, cellular reactivity against C. albicans was enhanced.

Purpose; The aim of this study was to characterize clinical effects and biomarkers in three patients with chronic mucocutaneous candidiasis (CMC) caused by gain-of-function (GOF) mutations in the STAT1 gene during treatment with Janus kinase (JAK) inhibitors. Methods: Mass cytometry (CyTOF) was used to characterize mononuclear leukocyte populations and Olink assay to quantify 265 plasma proteins. Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) was used to quantify the reactivity against Candida albicans. Results: Overall, JAK inhibitors improved clinical symptoms of CMC, but caused side effects in two patients. Absolute numbers of neutrophils, T cells, B cells, and NK cells were sustained during baricitinib treatment. Detailed analysis of cellular subsets, using CyTOF, revealed increased expression of CD45, CD52, and CD99 in NK cells, reflecting a more functional phenotype. Conversely, monocytes and eosinophils downregulated CD16, consistent with reduced inflammation. Moreover, T and B cells showed increased expression of activation markers during treatment. In one patient with a remarkable clinical effect of baricitinib treatment, the immune response to C. albicans increased after 7 weeks of treatment. Alterations in plasma biomarkers involved downregulation of cellular markers CXCL10, annexin A1, granzyme B, granzyme H, and oncostatin M, whereas FGF21 was the only upregulated marker after 7 weeks. After 3 months, IFN-gamma and CXCL10 were downregulated. Conclusions: The clinical effect of JAK inhibitor treatment of CMC is promising. Several biological variables were altered during baricitinib treatment demonstrating that lymphocytes, NK cells, monocytes, and eosinophils were affected. In parallel, cellular reactivity against C. albicans was enhanced.

Introduction: This post hoc analysis evaluated influenza adverse events (AEs) across rheumatoid arthritis (RA), ulcerative colitis (UC), and psoriatic arthritis (PsA) tofacitinib clinical programs. Methods: Available data from phase 1, randomized phase 2/3/3b/4 clinical trials (completed by 2018), and long-term extension (LTE) studies (up to May 2019) in patients with RA, UC, and PsA were included [randomized or Overall (phase 1-3b/4 and LTE studies) tofacitinib cohorts]. Incidence rates (IRs; events per 100 patient-years) of combined influenza AEs (seasons 2004/2005 to 2018/2019) were analyzed, including by tofacitinib dose [5 or 10 mg twice daily (BID)] and age (< 65 versus >= 65 years). Logistic regression models evaluated risk factors for influenza AEs in the RA Overall tofacitinib cohort. Results: In randomized cohorts, combined influenza AE IRs were generally similar across tofacitinib, adalimumab, methotrexate, and placebo groups, across indications. Among Overall tofacitinib cohorts, combined influenza AE IRs with tofacitinib 5/10 mg BID, respectively, were higher in the UC (3.66/5.09) versus RA (2.38/2.19) and PsA (1.74/1.29) cohorts. IRs were generally similar across tofacitinib dose and age groups. Most influenza AEs were nonserious and did not require changes to tofacitinib treatment. Significant risk factors for influenza AEs in patients with RA were geographic region, baseline oral corticosteroid and methotrexate use, and tofacitinib dose. Conclusions: In the RA, UC, and PsA clinical programs, combined influenza AE IRs were highest in UC, while in each indication they were generally similar across tofacitinib, placebo, and comparator groups. Influenza AEs were predominantly nonserious and not associated with changes to tofacitinib treatment.

Purpose; The aim of this study was to characterize clinical effects and biomarkers in three patients with chronic mucocutaneous candidiasis (CMC) caused by gain-of-function (GOF) mutations in the STAT1 gene during treatment with Janus kinase (JAK) inhibitors. Methods: Mass cytometry (CyTOF) was used to characterize mononuclear leukocyte populations and Olink assay to quantify 265 plasma proteins. Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) was used to quantify the reactivity against Candida albicans. Results: Overall, JAK inhibitors improved clinical symptoms of CMC, but caused side effects in two patients. Absolute numbers of neutrophils, T cells, B cells, and NK cells were sustained during baricitinib treatment. Detailed analysis of cellular subsets, using CyTOF, revealed increased expression of CD45, CD52, and CD99 in NK cells, reflecting a more functional phenotype. Conversely, monocytes and eosinophils downregulated CD16, consistent with reduced inflammation. Moreover, T and B cells showed increased expression of activation markers during treatment. In one patient with a remarkable clinical effect of baricitinib treatment, the immune response to C. albicans increased after 7 weeks of treatment. Alterations in plasma biomarkers involved downregulation of cellular markers CXCL10, annexin A1, granzyme B, granzyme H, and oncostatin M, whereas FGF21 was the only upregulated marker after 7 weeks. After 3 months, IFN-gamma and CXCL10 were downregulated. Conclusions: The clinical effect of JAK inhibitor treatment of CMC is promising. Several biological variables were altered during baricitinib treatment demonstrating that lymphocytes, NK cells, monocytes, and eosinophils were affected. In parallel, cellular reactivity against C. albicans was enhanced.

Introduction: This post hoc analysis evaluated influenza adverse events (AEs) across rheumatoid arthritis (RA), ulcerative colitis (UC), and psoriatic arthritis (PsA) tofacitinib clinical programs. Methods: Available data from phase 1, randomized phase 2/3/3b/4 clinical trials (completed by 2018), and long-term extension (LTE) studies (up to May 2019) in patients with RA, UC, and PsA were included [randomized or Overall (phase 1-3b/4 and LTE studies) tofacitinib cohorts]. Incidence rates (IRs; events per 100 patient-years) of combined influenza AEs (seasons 2004/2005 to 2018/2019) were analyzed, including by tofacitinib dose [5 or 10 mg twice daily (BID)] and age (< 65 versus >= 65 years). Logistic regression models evaluated risk factors for influenza AEs in the RA Overall tofacitinib cohort. Results: In randomized cohorts, combined influenza AE IRs were generally similar across tofacitinib, adalimumab, methotrexate, and placebo groups, across indications. Among Overall tofacitinib cohorts, combined influenza AE IRs with tofacitinib 5/10 mg BID, respectively, were higher in the UC (3.66/5.09) versus RA (2.38/2.19) and PsA (1.74/1.29) cohorts. IRs were generally similar across tofacitinib dose and age groups. Most influenza AEs were nonserious and did not require changes to tofacitinib treatment. Significant risk factors for influenza AEs in patients with RA were geographic region, baseline oral corticosteroid and methotrexate use, and tofacitinib dose. Conclusions: In the RA, UC, and PsA clinical programs, combined influenza AE IRs were highest in UC, while in each indication they were generally similar across tofacitinib, placebo, and comparator groups. Influenza AEs were predominantly nonserious and not associated with changes to tofacitinib treatment.

Yari S., Kikuta J., Shigyo H., et al. JAK inhibition ameliorates bone destruction by simultaneously targeting mature osteoclasts and their precursors. Inflammation and Regeneration 43, 18 (2023); https://doi.org/10.1186/s41232-023-00268-4., Background: Rheumatoid arthritis (RA) is characterized by chronic inflammation and resultant cartilage/bone destruction because of aberrantly activated osteoclasts. Recently, novel treatments with several Janus kinase (JAK) inhibitors have been shown to successfully ameliorate arthritis-related inflammation and bone erosion, although their mechanisms of action for limiting bone destruction remain unclear. Here, we examined the effects of a JAK inhibitor on mature osteoclasts and their precursors by intravital multiphoton imaging. Methods: Inflammatory bone destruction was induced by local injection of lipopolysaccharides into transgenic mice carrying reporters for mature osteoclasts or their precursors. Mice were treated with the JAK inhibitor, ABT-317, which selectively inhibits the activation of JAK1, and then subjected to intravital imaging with multiphoton microscopy. We also used RNA sequencing (RNA-Seq) analysis to investigate the molecular mechanism underlying the effects of the JAK inhibitor on osteoclasts. Results: The JAK inhibitor, ABT-317, suppressed bone resorption by blocking the function of mature osteoclasts and by targeting the migratory behaviors of osteoclast precursors to the bone surface. Further exhaustive RNA-Seq analysis demonstrated that Ccr1 expression on osteoclast precursors was suppressed in the JAK inhibitor-treated mice; the CCR1 antagonist, J-113863, altered the migratory behaviors of osteoclast precursors, which led to the inhibition of bone destruction under inflammatory conditions. Conclusions: This is the first study to determine the pharmacological actions by which a JAK inhibitor blocks bone destruction under inflammatory conditions; this inhibition is beneficial because of its dual effects on both mature osteoclasts and immature osteoclast precursors.

Background:Administration of Janus kinase (JAK) inhibitors and biological disease-modifying antirheumatic drugs has dramatically improved even the clinical outcomes in patients with rheumatoid arthritis (RA) and an inadequate response to methotrexate (MTX). Dysregulation of JAK-STAT pathways via overproduction of cytokines, such as interleukin-6, is involved in the pathogenesis of RA. Filgotinib is a selective JAK1 inhibitor pending approval for use in RA. By inhibition of the JAK-STAT pathway, filgotinib is effective in suppressing disease activity and preventing the progression of joint destruction. Similarly, interleukin-6 inhibitors such as tocilizumab also inhibit the JAK-STAT pathways by inhibition of interleukin-6 signaling. We present the protocol for a study that will evaluate whether the effectiveness of filgotinib monotherapy is non-inferior to that of tocilizumab monotherapy in RA patients with an inadequate response to MTX. Methods:This study is an interventional, multicenter, randomized, open-label, parallel-group, and non-inferiority clinical trial with a 52-week follow-up. Study participants will be 400 RA patients with at least moderate disease activity during treatment with MTX. Participants will be randomized in a 1:1 ratio to administer filgotinib monotherapy or subcutaneous tocilizumab monotherapy switched from MTX. We will evaluate disease activity by measuring clinical disease activity indices and by using musculoskeletal ultrasound (MSUS). The primary endpoint is the proportion of patients who achieve an American College of Rheumatology 50 response at week 12. Secondary endpoints are changes from baseline in the MSUS scores. We will also comprehensively analyze serum levels of multiple biomarkers, such as cytokines and chemokines. Discussion:The study results are expected to show the non-inferiority of the effectiveness of filgotinib monotherapy to that of tocilizumab monotherapy in RA patients with inadequate response to MTX. The strength of, Trials, 24(1), art. no. 161; 2023

Purpose; The aim of this study was to characterize clinical effects and biomarkers in three patients with chronic mucocutaneous candidiasis (CMC) caused by gain-of-function (GOF) mutations in the STAT1 gene during treatment with Janus kinase (JAK) inhibitors. Methods: Mass cytometry (CyTOF) was used to characterize mononuclear leukocyte populations and Olink assay to quantify 265 plasma proteins. Flow-cytometric Assay for Specific Cell-mediated Immune-response in Activated whole blood (FASCIA) was used to quantify the reactivity against Candida albicans. Results: Overall, JAK inhibitors improved clinical symptoms of CMC, but caused side effects in two patients. Absolute numbers of neutrophils, T cells, B cells, and NK cells were sustained during baricitinib treatment. Detailed analysis of cellular subsets, using CyTOF, revealed increased expression of CD45, CD52, and CD99 in NK cells, reflecting a more functional phenotype. Conversely, monocytes and eosinophils downregulated CD16, consistent with reduced inflammation. Moreover, T and B cells showed increased expression of activation markers during treatment. In one patient with a remarkable clinical effect of baricitinib treatment, the immune response to C. albicans increased after 7 weeks of treatment. Alterations in plasma biomarkers involved downregulation of cellular markers CXCL10, annexin A1, granzyme B, granzyme H, and oncostatin M, whereas FGF21 was the only upregulated marker after 7 weeks. After 3 months, IFN-gamma and CXCL10 were downregulated. Conclusions: The clinical effect of JAK inhibitor treatment of CMC is promising. Several biological variables were altered during baricitinib treatment demonstrating that lymphocytes, NK cells, monocytes, and eosinophils were affected. In parallel, cellular reactivity against C. albicans was enhanced.

Introduction: This post hoc analysis evaluated influenza adverse events (AEs) across rheumatoid arthritis (RA), ulcerative colitis (UC), and psoriatic arthritis (PsA) tofacitinib clinical programs. Methods: Available data from phase 1, randomized phase 2/3/3b/4 clinical trials (completed by 2018), and long-term extension (LTE) studies (up to May 2019) in patients with RA, UC, and PsA were included [randomized or Overall (phase 1-3b/4 and LTE studies) tofacitinib cohorts]. Incidence rates (IRs; events per 100 patient-years) of combined influenza AEs (seasons 2004/2005 to 2018/2019) were analyzed, including by tofacitinib dose [5 or 10 mg twice daily (BID)] and age (< 65 versus >= 65 years). Logistic regression models evaluated risk factors for influenza AEs in the RA Overall tofacitinib cohort. Results: In randomized cohorts, combined influenza AE IRs were generally similar across tofacitinib, adalimumab, methotrexate, and placebo groups, across indications. Among Overall tofacitinib cohorts, combined influenza AE IRs with tofacitinib 5/10 mg BID, respectively, were higher in the UC (3.66/5.09) versus RA (2.38/2.19) and PsA (1.74/1.29) cohorts. IRs were generally similar across tofacitinib dose and age groups. Most influenza AEs were nonserious and did not require changes to tofacitinib treatment. Significant risk factors for influenza AEs in patients with RA were geographic region, baseline oral corticosteroid and methotrexate use, and tofacitinib dose. Conclusions: In the RA, UC, and PsA clinical programs, combined influenza AE IRs were highest in UC, while in each indication they were generally similar across tofacitinib, placebo, and comparator groups. Influenza AEs were predominantly nonserious and not associated with changes to tofacitinib treatment.

Colorectal cancer is a known complication of chronic inflammation of the colon (“colitis-associated colon cancer”). Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract. Patients with IBD are at increased risk of colon cancer compared to the general population. Kinase signaling pathways play critical roles in both the inflammation and regulating cellular processes such as proliferation and survival that contribute to cancer development. Here we review the interplay of kinase signaling pathways (mitogen-activated protein kinases, cyclin-dependent kinases, autophagy-activated kinases, JAK-STAT, and other kinases) and their effects on colitis-associated colon cancer. We also discuss the role of JAK-STAT signaling in the pathogenesis of IBD and the therapeutic landscape of JAK inhibitors for the treatment of IBD.

Rheumatoid arthritis (RA) is a common autoimmune disease. Janus kinase inhibitors (JAKi) have been approved for the treatment of RA; however, the impact of JAKi on immune cells remains inconclusive. This study investigated the response of immune cells to JAKi treatment to identify biomarkers by which to evaluate and predict clinical outcomes. Blood samples were collected from RA patients before and after JAKi treatment for the analysis of immunophenotypes. Our results revealed that JAKi mainly inhibited Fas+ T cell subsets. The percentage changes of Th Fas+ and Naive Th Fas+ cells were positively correlated with the 28-joint Disease Activity Score with erythrocyte sedimentation rate (DAS28-ESR) values. Following treatment, moderate response (MR) RA patients presented a decrease in the number of Naive Th Fas+ cells (p = 0.0001). Initial percentages of 14 T cell and 20 B cell subsets were correlated with percentage changes in DAS28-ESR. Overall, 16 cell subsets presented significant differences between the non-response (NR) and MR groups. Excluding the multicollinearity of the immune cells, we constructed a JAKi treatment response prediction index (JRPI) using 5 subsets of T/B cells, the results of which were strongly correlated with percentage changes in DAS28-ESR (receiver operating characteristic curve of 1). Note that the NR group was clearly distinguished from the MR group (p = 0.0167). In conclusion, the efficacy of JAKi can be attributed mainly to the suppression of Fas+ T cell subsets. A positive correlation was shown between the therapeutic efficacy of JAKi and the percentage changes in both Th Fas+ cells and Naive Th Fas+ cells. Furthermore, the proposed JRPI could potentially be used as an indicator to predict the efficacy of JAKi prior to treatment in RA patients. These findings may contribute to the development of personalized treatment strategies for RA patients using JAKi., Rheumatoid arthritis (RA) is a common autoimmune disease. Janus kinase inhibitors (JAKi) have been approved for the treatment of RA; however, the impact of JAKi on immune cells remains inconclusive. This study investigated the response of immune cells to JAKi treatment to identify biomarkers by which to evaluate and predict clinical outcomes. Blood samples were collected from RA patients before and after JAKi treatment for the analysis of immunophenotypes. Our results revealed that JAKi mainly inhibited Fas+ T cell subsets. The percentage changes of Th Fas+ and Naive Th Fas+ cells were positively correlated with the 28-joint Disease Activity Score with erythrocyte sedimentation rate (DAS28-ESR) values. Following treatment, moderate response (MR) RA patients presented a decrease in the number of Naive Th Fas+ cells (p = 0.0001). Initial percentages of 14 T cell and 20 B cell subsets were correlated with percentage changes in DAS28-ESR. Overall, 16 cell subsets presented significant differences between the non-response (NR) and MR groups. Excluding the multicollinearity of the immune cells, we constructed a JAKi treatment response prediction index (JRPI) using 5 subsets of T/B cells, the results of which were strongly correlated with percentage changes in DAS28-ESR (receiver operating characteristic curve of 1). Note that the NR group was clearly distinguished from the MR group (p = 0.0167). In conclusion, the efficacy of JAKi can be attributed mainly to the suppression of Fas+ T cell subsets. A positive correlation was shown between the therapeutic efficacy of JAKi and the percentage changes in both Th Fas+ cells and Naive Th Fas+ cells. Furthermore, the proposed JRPI could potentially be used as an indicator to predict the efficacy of JAKi prior to treatment in RA patients. These findings may contribute to the development of personalized treatment strategies for RA patients using JAKi.

Colorectal cancer is a known complication of chronic inflammation of the colon (“colitis-associated colon cancer”). Inflammatory bowel disease (IBD) is a chronic inflammatory disorder of the gastrointestinal tract. Patients with IBD are at increased risk of colon cancer compared to the general population. Kinase signaling pathways play critical roles in both the inflammation and regulating cellular processes such as proliferation and survival that contribute to cancer development. Here we review the interplay of kinase signaling pathways (mitogen-activated protein kinases, cyclin-dependent kinases, autophagy-activated kinases, JAK-STAT, and other kinases) and their effects on colitis-associated colon cancer. We also discuss the role of JAK-STAT signaling in the pathogenesis of IBD and the therapeutic landscape of JAK inhibitors for the treatment of IBD.

New evidence for the treatment of rheumatoid arthritis (RA) has emerged during the last year. Specifically, updated guidelines on pharmacological and non-pharmacological management of RA have emphasised the necessity of global patient’s care, and have shifted the role of some older drugs, such as glucocorticoids and methotrexate. In addition, the long-term safety of Janus kinase inhibitors was investigated and reinforced. With respect to the coronavirus-19 pandemic, reassuring data on the efficacy and safety of vaccinations in the RA population were acquired, as well as on the potential role of telemedicine in RA management. Machine learning prediction models and biomarkers development have emerged as promising innovations in the area of precision/personalised medicine, appearing to encourage future expansion. In this narrative review, the authors aim to give their specific point of view on the most relevant and potentially impacting novelties published during 2021 and early 2022 in the context of RA management.

Background: Itch, skin pain, and sleep disturbance are burdensome symptoms in atopic dermatitis (AD) that negatively influence a patient’s quality of life (QoL). Objective: To evaluate the impact of baricitinib on patient-reported outcomes (PROs) in adult patients with moderate-to-severe AD, and explore the association between improvement in key signs and symptoms of AD with improvements in QoL and patient’s assessment of disease severity. Methods: Data were analyzed from two phase III monotherapy trials (BREEZE-AD1/BREEZE-AD2) in which patients were randomized 2:1:1:1 to once-daily placebo, baricitinib 1-mg, 2-mg, or 4-mg for 16 weeks and assessed using PRO measures. Results: At week 16, baricitinib 4-mg and 2-mg significantly reduced itch severity (Itch Numeric Rating Scale (NRS) (BREEZE-AD1: percent change from baseline −36.6% and −29.4% vs. placebo (–12.0%), p≤.001 and p≤.05; BREEZE-AD2: −47.2% and −46.9% vs. placebo (–16.6%), p≤.001). Baricitinib significantly reduced SCORing AD (SCORAD) pruritus (4-mg in BREEZE-AD1 and 2-mg in BREEZE-AD2) and Patient Oriented Eczema Measure (POEM) itch (both doses). Improvements in skin pain severity and sleep disturbance were also observed. Improvements in AD symptoms showed higher correlations with patients’ assessment of AD severity and QoL than improvements in skin inflammation. Conclusions: Baricitinib significantly improved symptoms in patients with moderate-to-severe AD. ClinicalTrials.gov identifiers: NCT03334396 (BREEZE-AD1) and NCT03334422 (BREEZE-AD2).

Background: Itch, skin pain, and sleep disturbance are burdensome symptoms in atopic dermatitis (AD) that negatively influence a patient’s quality of life (QoL). Objective: To evaluate the impact of baricitinib on patient-reported outcomes (PROs) in adult patients with moderate-to-severe AD, and explore the association between improvement in key signs and symptoms of AD with improvements in QoL and patient’s assessment of disease severity. Methods: Data were analyzed from two phase III monotherapy trials (BREEZE-AD1/BREEZE-AD2) in which patients were randomized 2:1:1:1 to once-daily placebo, baricitinib 1-mg, 2-mg, or 4-mg for 16 weeks and assessed using PRO measures. Results: At week 16, baricitinib 4-mg and 2-mg significantly reduced itch severity (Itch Numeric Rating Scale (NRS) (BREEZE-AD1: percent change from baseline −36.6% and −29.4% vs. placebo (–12.0%), p≤.001 and p≤.05; BREEZE-AD2: −47.2% and −46.9% vs. placebo (–16.6%), p≤.001). Baricitinib significantly reduced SCORing AD (SCORAD) pruritus (4-mg in BREEZE-AD1 and 2-mg in BREEZE-AD2) and Patient Oriented Eczema Measure (POEM) itch (both doses). Improvements in skin pain severity and sleep disturbance were also observed. Improvements in AD symptoms showed higher correlations with patients’ assessment of AD severity and QoL than improvements in skin inflammation. Conclusions: Baricitinib significantly improved symptoms in patients with moderate-to-severe AD. ClinicalTrials.gov identifiers: NCT03334396 (BREEZE-AD1) and NCT03334422 (BREEZE-AD2).

Dermatitis herpetiformis (DH) is a rare autoimmune blistering disorder in which patients with celiac disease, a gluten-sensitive enteropathy, present with a severely pruritic papulovesicular eruption over extensor surfaces such as the knees, elbows, lower back, buttocks, and neck. Patients are instructed to adhere to a gluten-free diet for purposes of improving their skin disease and gluten-sensitive enteropathy; this is the only treatment that lowers risk of enteropathy-associated T cell lymphoma. Patients who adhere to a strict gluten-free diet often have remission of their skin disease over months to years. Dapsone is a rapid and extremely effective first-line treatment option and often used while transitioning to a gluten-free diet. Aside from gluten-free diet and dapsone, second-line treatment options include sulfapyridine, sulfasalazine, and colchicine. Some patients have difficulty adhering to a gluten-free diet or develop intolerable side effects to systemic therapies. Furthermore, there is limited data on the use of the second-line treatments. Recent studies have shed light on the role of JAK-STAT-dependent pathways in the pathogenesis of dermatitis herpetiformis. We present a patient treated with tofacitinib, 5mg twice daily, an oral JAK1/3 inhibitor, who demonstrated clinical improvement of DH and control of new lesion development.

Management of rheumatoid arthritis (RA) has evolved over the years as a result of better understanding of the role of different therapeutic strategies, as well as following an increasing availability of new disease-modifying antirheumatic drugs. However, the role of patients in sharing decisions, as well as the rules informing precision medicine or the principles to follow in case of specific comorbidities or extra-articular manifestations are still areas for improvement. Moreover, in 2020, the novel Coronavirus disease-19 outbreak has completely changed many attitudes in terms of assessment and treatment paradigms in most clinical diseases, including RA. In this narrative review, the authors report their specific point of view on the management of RA, based on a critical revision of literature published in 2020, focusing on relevant novelties and future research directions.

Dermatitis herpetiformis (DH) is a rare autoimmune blistering disorder in which patients with celiac disease, a gluten-sensitive enteropathy, present with a severely pruritic papulovesicular eruption over extensor surfaces such as the knees, elbows, lower back, buttocks, and neck. Patients are instructed to adhere to a gluten-free diet for purposes of improving their skin disease and gluten-sensitive enteropathy; this is the only treatment that lowers risk of enteropathy-associated T cell lymphoma. Patients who adhere to a strict gluten-free diet often have remission of their skin disease over months to years. Dapsone is a rapid and extremely effective first-line treatment option and often used while transitioning to a gluten-free diet. Aside from gluten-free diet and dapsone, second-line treatment options include sulfapyridine, sulfasalazine, and colchicine. Some patients have difficulty adhering to a gluten-free diet or develop intolerable side effects to systemic therapies. Furthermore, there is limited data on the use of the second-line treatments. Recent studies have shed light on the role of JAK-STAT-dependent pathways in the pathogenesis of dermatitis herpetiformis. We present a patient treated with tofacitinib, 5mg twice daily, an oral JAK1/3 inhibitor, who demonstrated clinical improvement of DH and control of new lesion development.

Management of rheumatoid arthritis (RA) has evolved over the years as a result of better understanding of the role of different therapeutic strategies, as well as following an increasing availability of new disease-modifying antirheumatic drugs. However, the role of patients in sharing decisions, as well as the rules informing precision medicine or the principles to follow in case of specific comorbidities or extra-articular manifestations are still areas for improvement. Moreover, in 2020, the novel Coronavirus disease-19 outbreak has completely changed many attitudes in terms of assessment and treatment paradigms in most clinical diseases, including RA. In this narrative review, the authors report their specific point of view on the management of RA, based on a critical revision of literature published in 2020, focusing on relevant novelties and future research directions.

Ruxolitinib is an anti-inflammatory drug that inhibits the Janus kinase-signal transducer (JAK-STAT) pathway on the surface of immune cells. The potential targeting of this pathway using JAK inhibitors is a promising approach in patients affected by coronavirus disease 2019 (COVID-19). Ruxolitinib was provided as a compassionate use in patients consecutively admitted to our institution for severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) infection. Inclusion criteria were oxygen saturation less than or equal to 92%, signs of interstitial pneumonia, and no need of mechanical ventilation. Patients received 5 mg b.i.d. of ruxolitinib for 15 days, data were collected at baseline and on days 4, 7, and 15 during treatment. Two main targets were identified, C-reactive protein (CRP) and PaO2/FiO2 ratio. In the 31 patients who received ruxolitinib, symptoms improved (dyspnea scale) on day 7 in 25 of 31 patients (80.6%); CRP decreased progressively from baseline (79.1 ± 73.4 mg/dl) to day 15 (18.6 ± 33.2, p = 0.022). In parallel with CRP, PO2/FiO2 ratio increased progressively during the 3 steps from 183 ± 95 to 361 ± 144 mmHg (p < 0.001). In those patients with a reduction of polymerase chain reaction less than or equal to 80%, delta increase of the PO2/FiO2 ratio was significantly more pronounced (129 ± 118 vs. 45 ± 35 mmHg, p = 0.02). No adverse side effects were recorded during treatment. In patients hospitalized for COVID-19, compassionate-use of ruxolitinib determined a significant reduction of biomarkers of inflammation, which was associated with a more effective ventilation and reduced need for oxygen support. Data on ruxolitinib reinforces the hypothesis that targeting the hyperinflammation state, may be of prognostic benefit in patients with SARS-CoV-2 infection. Study Highlights WHAT IS THE CURRENT KNOWLEDGE ON THE TOPIC? Some

Background and aimsOral systemic pan-Janus kinase [JAK] inhibition is effective for ulcerative colitis [UC] but is limited by toxicities. We describe preclinical to clinical translation of TD-1473-an oral gut-selective pan-JAK inhibitor-from in vitro characterization through a Phase 1b study in patients with UC.MethodsTD-1473 JAK inhibition potency was evaluated in vitro; plasma pharmacokinetics, safety and efficacy were assessed in mice. In a first-time-in-human study, plasma pharmacokinetics and safety were assessed after single and multiple [14 days] ascending doses administered orally to healthy subjects. The Phase 1b study randomized patients with moderately to severely active UC to receive once-daily oral TD-1473 20, 80 or 270 mg, or placebo for 28 days. Plasma and colonic tissue concentrations were measured; safety was assessed; and efficacy was evaluated by UC clinical parameters, disease-surrogate biomarkers, endoscopy, histology and colonic tissue JAK signalling.ResultsTD-1473 exhibited potent pan-JAK inhibitory activity in vitro. Oral TD-1473 administration to mice achieved high, biologically active colonic tissue concentrations with low plasma exposure and decreased oxazolone-induced colitis activity without reducing blood cell counts vs placebo. TD-1473 administration in healthy human subjects and patients with UC yielded low plasma exposure and was generally well tolerated; treatment in patients with UC resulted in biologically active colonic tissue concentrations and descriptive trends toward reduced clinical, endoscopic and histological disease activity vs placebo.ConclusionGut-selective pan-JAK inhibition with TD-1473 administration resulted in high intestinal vs plasma drug exposure, local target engagement, and trends toward reduced UC disease activity. [Clinicaltrials.gov NCT02657122, NCT02818686].

La artritis reumatoide (AR) es una enfermedad inflamatoria autoinmune, caracterizada por una destrucción progresiva del tejido óseo y cartilaginoso, causando deformidad y limitación funcional de la articulación. Además de las manifestaciones articulares, puede afectar a otras localizaciones (pulmón, leucocitos, plaquetas,…). Las nuevas líneas terapéuticas (FAME biológicos o inhibidores de Janus Cinasa) se han sumado a los fármacos moduladores de la enfermedad clásicos (FAME clásicos) con el objetivo de mejorar la enfermedad y generar menos efectos adversos. A estas líneas de tratamiento, se unen de forma tradicional los glucocorticoides (GC), que a veces coexisten durante largos periodos de tiempo, con la posibilidad de aparición de efectos adversos. Objetivo: Analizar el uso concomitante de GG en aquellos pacientes con AR que utilizan terapia biológica o inhibidores de JAK para el control de su sintomatología, y estratificar cuáles son los tratamientos biológicos que menos cantidad precisan. Metodología: Se incluyeron 437 pacientes con AR de un total de 1152 historias clínicas de pacientes con enfermedad autoinmune y en tratamiento con terapia biológica. Los recursos informáticos utilizados fueron el sistema Diraya, Microsoft Office Excell 2007 e IBM SPSS Statistics 19. Resultados: Se confirmó una doble positividad (FR/anti-CCP) en los pacientes con AR. Los fármacos biológicos más empleados fueron el etanercept, el adalimumab y el tocilizumab. Casi la mitad de los pacientes tenían prescritos GC, siendo el infliximab el que menos GC necesitaba. El metotrexato fue el FAME clásico más empleado y el que precisa un menor uso conjunto con GC. Considerando la asociación terapia biológica o inhibidores de JAK/GC/sin FAME clásico, los pacientes que empleaban menos GC eran los tratados con el certolizumab y el tocilizumab, a dosis inferiores a la dosis límite que produce efectos secundarios. Sin embargo, el baricitinib y el tofacitinib necesitaban dosis mayores de GC. Conclu, Introduction: Rheumatoid arthritis (RA) is an inflammatory autoimmune disease, characterized by progressive destruction of bone and cartilage tissue, causing deformity and functional limitation of the joint. In addition to joint manifestations, it can affect other locations (lung, leukocytes, platelets,...). New therapeutic agents (biological DMARDs or inhibitors Janus Cinasainhibitors) have been added to the classic disease modulators (classic DMARD) with the aim of improving the disease and generating fewer adverse effects. Moreover, glucocorticoids (GC) are traditionally linked to these treatment lines, which sometimes coexist for long periods of time, with the possibility of the appearance of adverse effects.. Objective: To analyze the concomitant use of GG in those patients with RA who use biological therapy or JAK inhibitors to control their symptoms, and to stratify the biological treatments that require less quantity of GC. Methodology: We included 437 patients with RA from a total of 1152 clinical histories of patients with autoimmune disease and in treatment with biological therapy. The computer resources used were the Diraya system, Microsoft Office Excell 2007 and IBM SPSS Statistics 19. Results: Double positive (FR / anti-CCP) was confirmed in patients with RA. The most commonly used biologic drugs were etanercept, adalimumab and tocilizumab. Almost half of the patients were being treated with GC, with infliximab being the one with the least GC. Methotrexate was the most commonly used classic DMARD and the one requiring less concomitant use with GC. Considering the association biological therapy or JAK / GC inhibitors / without classic DMARD, patients using less GC were those treated with certolizumab and tocilizumab, at doses lower than the limit dose that produces side effects. However, baricitinib and tofacitinib needed higher doses of GC. Conclusion: It is confirmed that a high number of patients need to use GC together with biological therapy, but

Purpose Preclinical evidence suggests the importance of Janus activating kinase (JAK) and TANK-binding kinase 1 (TBK1) in pancreatic ductal adenocarcinoma (PDAC). We evaluated the safety and efficacy of momelotinib (MMB), a JAK1/2 inhibitor with additional activity against TBK1, plus albumin-bound paclitaxel + gemcitabine (nab-P + G), in patients with previously untreated metastatic PDAC. Experimental Design Patients were enrolled into five cohorts of increasing doses of MMB between 100 and 200 mg administered once or twice daily in combination with nab-P + G in 28-day cycles to determine maximum tolerated dose (MTD). Safety, efficacy, pharmacokinetics, and pharmacodynamics were assessed for all patients. Results Twenty-five patients were enrolled. Dose-limiting toxicities of Grade 3 diarrhea occurred in 1 patient each in the 100 and 200 mg MMB once-daily dose groups. MTD was not reached. The 200 mg MMB twice-daily was the maximum administered dose. Objective response rate was 28% (all partial responses), and 13 (52%) patients had a best response of stable disease. The most common adverse events (AEs) were fatigue (80%), nausea (76%), and anemia (68%). Grade 3 or 4 AEs, most commonly neutropenia (32%), were reported by 88% of patients, of which 44% were considered related to MMB. Pharmacokinetic analyses showed MMB concentrations were too low for TBK1 inhibition. Conclusions MMB was safe and well tolerated in combination with nab-P + G. As no OS or PFS benefit vs nab-P + G was apparent in context of suboptimal engagement of the target TBK1, this study does not support further development of MMB as a first-line therapy in pancreatic cancer.

Patients with myeloproliferative neoplasms (MPN) are known to have higher incidence of nonhematological second primary malignancies (SPM) compared to general population. In the MYSEC study on 781 secondary myelofibrosis (SMF) patients, the incidence of SPM after SMF diagnosis resulted 0.98/100 patient-years. When including non-melanoma skin cancers (NMSC), the incidence arose to 1.56/100 patientyears. In SMF, JAK inhibitor treatment was associated only with NMSC occurrence. Then, we merged the MYSEC cohort with a large dataset of PV and ET not evolving into SMF. In this subanalysis, we did not find any correlation between SPM and SMF occurrence. These findings highlight the need of studies aimed at identifying MPN patients at higher risk of SPM.

Introduction: Atopic dermatitis (AD) is the most common cutaneous inflammatory disease in adults and children. In the last few years, the pathogenesis of AD has been profoundly revised, and this has led to the identification of novel druggable targets and the development of new agents targeting specific molecular pathways. Despite the high prevalence of AD in the pediatric population, the clinical development of new treatments, either topical or systemic, has been focused on the adult population in recent years; only a limited number of these new agents have been tested in pediatric cohorts. Areas covered: In this review, we describe the pathogenic model of pediatric AD which shows similarities and substantial differences when compared to adult AD. The identification of therapeutic targets is highlighted, and novel targeted therapies, both topical and systemic, are discussed. Expert opinion: The current therapeutic armamentarium for pediatric AD is very limited, and this represents a critical unmet need. The enhancement of clinical research on pediatric patients is necessary to facilitate an increase in the number of new targeted therapeutic options being available on the market.

JAK1 and JAK3 are recurrently mutated in acute lymphoblastic leukemia. These tyrosine kinases associate with heterodimeric cytokine receptors such as IL-7R or IL-9R, in which JAK1 is appended to the specific chain and JAK3 to the common gamma chain. Here, we studied the role of these receptor complexes in mediating the oncogenic activity of JAK3 mutants. While JAK3(V674A) and the majority of other JAK3 mutants needed to bind to a functional cytokine receptor complex in order to constitutively activate STAT5, JAK3(L857P) was unexpectedly found to not depend on such receptor complexes for its activity, which was induced without receptor or JAK1 co-expression. Introducing a mutation in the FERM domain that abolished JAK-receptor interaction did not affect JAK3(L857P) activity, while it inhibited the other receptor-dependent mutants. The same cytokine receptor independence as for JAK3(L857P) was observed for homologous L(857) mutations of JAK1 and JAK2 and for JAK3(L875H). This different cytokine receptor requirement correlated with different functional properties in vivo and with distinct sensitivity to JAK inhibitors. Transduction of murine hematopoietic cells with JAK3(V674A) led homogenously to lymphoblastic leukemias in BALB/c mice. In contrast, transduction with JAK3(L857P) induced various types of lymphoid and myeloid leukemias. Moreover, Ruxolitinib, which preferentially blocks JAK1 and JAK2, abolished the proliferation of cells transformed by the receptor-dependent JAK3(V674A), yet proved much less potent on cells expressing JAK3(L857P). These particular cells were, in contrast, more sensitive to JAK3-specific inhibitors. Altogether, our results showed that different JAK3 mutations induce constitutive activation through distinct mechanisms, pointing to specific therapeutic perspectives.

Background: Rheumatoid arthritis (RA) is characterized by chronic inflammation and resultant cartilage/bone destruction because of aberrantly activated osteoclasts. Recently, novel treatments with several Janus kinase (JAK) inhibitors have been shown to successfully ameliorate arthritis-related inflammation and bone erosion, although their mechanisms of action for limiting bone destruction remain unclear. Here, we examined the effects of a JAK inhibitor on mature osteoclasts and their precursors by intravital multiphoton imaging. Methods: Inflammatory bone destruction was induced by local injection of lipopolysaccharides into transgenic mice carrying reporters for mature osteoclasts or their precursors. Mice were treated with the JAK inhibitor, ABT-317, which selectively inhibits the activation of JAK1, and then subjected to intravital imaging with multiphoton microscopy. We also used RNA sequencing (RNA-Seq) analysis to investigate the molecular mechanism underlying the effects of the JAK inhibitor on osteoclasts. Results: The JAK inhibitor, ABT-317, suppressed bone resorption by blocking the function of mature osteoclasts and by targeting the migratory behaviors of osteoclast precursors to the bone surface. Further exhaustive RNA-Seq analysis demonstrated that Ccr1 expression on osteoclast precursors was suppressed in the JAK inhibitor-treated mice; the CCR1 antagonist, J-113863, altered the migratory behaviors of osteoclast precursors, which led to the inhibition of bone destruction under inflammatory conditions. Conclusions: This is the first study to determine the pharmacological actions by which a JAK inhibitor blocks bone destruction under inflammatory conditions; this inhibition is beneficial because of its dual effects on both mature osteoclasts and immature osteoclast precursors., Yari S., Kikuta J., Shigyo H., et al. JAK inhibition ameliorates bone destruction by simultaneously targeting mature osteoclasts and their precursors. Inflammation and Regeneration 43, 18 (2023); https://doi.org/10.1186/s41232-023-00268-4.

Yari S., Kikuta J., Shigyo H., et al. JAK inhibition ameliorates bone destruction by simultaneously targeting mature osteoclasts and their precursors. Inflammation and Regeneration 43, 18 (2023); https://doi.org/10.1186/s41232-023-00268-4., Background: Rheumatoid arthritis (RA) is characterized by chronic inflammation and resultant cartilage/bone destruction because of aberrantly activated osteoclasts. Recently, novel treatments with several Janus kinase (JAK) inhibitors have been shown to successfully ameliorate arthritis-related inflammation and bone erosion, although their mechanisms of action for limiting bone destruction remain unclear. Here, we examined the effects of a JAK inhibitor on mature osteoclasts and their precursors by intravital multiphoton imaging. Methods: Inflammatory bone destruction was induced by local injection of lipopolysaccharides into transgenic mice carrying reporters for mature osteoclasts or their precursors. Mice were treated with the JAK inhibitor, ABT-317, which selectively inhibits the activation of JAK1, and then subjected to intravital imaging with multiphoton microscopy. We also used RNA sequencing (RNA-Seq) analysis to investigate the molecular mechanism underlying the effects of the JAK inhibitor on osteoclasts. Results: The JAK inhibitor, ABT-317, suppressed bone resorption by blocking the function of mature osteoclasts and by targeting the migratory behaviors of osteoclast precursors to the bone surface. Further exhaustive RNA-Seq analysis demonstrated that Ccr1 expression on osteoclast precursors was suppressed in the JAK inhibitor-treated mice; the CCR1 antagonist, J-113863, altered the migratory behaviors of osteoclast precursors, which led to the inhibition of bone destruction under inflammatory conditions. Conclusions: This is the first study to determine the pharmacological actions by which a JAK inhibitor blocks bone destruction under inflammatory conditions; this inhibition is beneficial because of its dual effects on both mature osteoclasts and immature osteoclast precursors.