The four Janus kinase (JAK) proteins and seven signal transducer and activator of transcription (STAT) transcription factors mediate intracellular signal transduction downstream of cytokine receptors, which are implicated in the pathology of autoimmune, allergic and inflammatory diseases. Development of targeted small-molecule therapies such as JAK inhibitors, which have varied selective inhibitory profiles, has enabled a paradigm shift in the treatment of diverse disorders. JAK inhibitors suppress intracellular signalling mediated by multiple cytokines involved in the pathological processes of rheumatoid arthritis and many other immune and inflammatory diseases, and therefore have the capacity to target multiple aspects of those diseases. In addition to rheumatoid arthritis, JAK inhibition has potential for treatment of autoimmune diseases including systemic lupus erythematosus, spondyloarthritis, inflammatory bowel disease and alopecia areata, in which stimulation of innate immunity activates adaptive immunity, leading to generation of autoreactive T cells and activation and differentiation of B cells. JAK inhibitors are also effective in the treatment of allergic disorders, such as atopic dermatitis, and can even be used for the COVID-19-related cytokine storm. Mechanism-based treatments targeting JAK–STAT pathways have the potential to provide positive outcomes by minimizing the use of glucocorticoids and/or non-specific immunosuppressants in the treatment of systemic immune-mediated inflammatory diseases.

ObjectiveTo evaluate the long-term safety profile for upadacitinib across rheumatoid arthritis (RA), psoriatic arthritis (PsA), ankylosing spondylitis (AS) and atopic dermatitis (AD).MethodsSafety data from clinical trials of upadacitinib 15 mg and upadacitinib 30 mg (AD only) for treating RA, PsA, AS and AD as of 30 June 2021 were analysed; some RA and PsA studies included adalimumab and methotrexate as active comparators. Treatment-emergent adverse events (TEAEs) were presented by disease as exposure-adjusted event rates per 100 patient years (E/100 PY).ResultsThe analysis included 6991 patients (RA, n=3209; PsA, n=907; AS, n=182; AD, n=2693) who received at least one dose of upadacitinib, representing 15 425 PY of exposure (maximum duration 2.75–5.45 years) across diseases. Rates (E/100 PY) of any TEAE (205.5–278.1) and TEAE leading to discontinuation (4.5–5.4) were similar across diseases; serious TEAEs were numerically higher in patients with RA and PsA. Rates of herpes zoster (1.6–3.6), non-melanoma skin cancer (0–0.8) and elevations in creatine phosphokinase levels (4.4–7.9) were higher with upadacitinib than with active comparators in the RA and PsA populations. Deaths (0–0.8), serious infections (0–3.9), major adverse cardiovascular events (0–0.4), venous thromboembolism (<0.1–0.4) and malignancies (0.3–1.4) were observed, with rates generally lowest in AS and AD. Increased rates of acne were observed in patients with AD only.ConclusionsFindings from this analysis demonstrate that upadacitinib is generally well tolerated with observed differences in safety profiles likely reflective of varying patient characteristics across RA, PsA, AS and AD populations.Trial registration numbersNCT02675426,NCT02706951,NCT02706847,NCT02629159,NCT02706873,NCT03086343,NCT03104374,NCT03104400,NCT03178487,NCT03569293,NCT03568318andNCT03607422.

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Objective. This study was undertaken to identify characteristics of follicular regulatory T (Tfr) cells and elucidate the mechanisms by which follicular helper T (Tfh) cells convert to Tfr cells. We probed the phenotype of T helper cells in patients with systemic lupus erythematosus (SLE) and underlying transcriptional regulation using cytokine-induced STAT family factors. Methods. Peripheral blood mononuclear cells from 41 patients with SLE and 26 healthy donors were used to sort out the memory Tfh cell subset, and Tfh cells were cultured under various conditions. The phenotype of T helper cells and underlying mechanisms of transcriptional regulation were probed using flow cytometry and quantitative polymerase chain reaction analyses. These analyses evaluated the expression of characteristic markers and phosphorylation of STATs. Chromatin immunoprecipitation was used to evaluate histone modifications. Results. In patients with SLE, the proportion of CD4+CXCR5+FoxP3-PD-1 high Tfh cells was increased (P < 0.01), whereas the proportion of CD4+CXCR5+CD45RA-FoxP3 high activated Tfr cells was decreased (P < 0.05). Serum interleukin-2 (IL-2) levels were also reduced in patients with SLE. IL-2 induced conversion of memory Tfh cells to functional Tfr cells, which was characterized by CXCR5+Bcl-6+FoxP3 high pSTAT3+pSTAT5+ cells. The loci of FOXP3 and BCL6 at STAT binding sites were marked by bivalent histone modifications. Following IL-2 stimulation, STAT3 and STAT5 selectively bound to FOXP3 and BCL6 gene loci accompanied by suppression of H3K27me3. Finally, IL-2 stimulation suppressed the generation of CD38+CD27 high plasmablasts in Tfh and B cell coculture assays ex vivo. Conclusion. Impaired function of Tfr cells might be attributed to defective IL-2 production. Exogenous IL-2 restores the function of Tfr cells through the conversion of Tfh cells to Tfr cells in patients with SLE. Thus, restoring balance between Tfh and Tfr cells may provide new therapeutic approaches in SLE.

Rheumatoid arthritis is an autoimmune inflammatory disease primarily characterized by synovitis which is accompanied by extra-articular organ involvement, such as interstitial pneumonia, in addition to clinical symptoms including pain, swelling, stiffness of multiple joints, fever, and malaise. Joint destruction progresses soon after the onset, and once the affected joints are deformed, the development of irreversible physical dysfunction is noted. Thus, proper diagnosis and treatment are required from the early stages of the disease. Although palliative therapy with glucocorticoids and antiinflammatory drugs had been used, disease-modifying antirheumatic drugs (DMARDs) are currently used to suppress immune abnormalities and to control disease activity. DMARDs are classified into different groups, such as conventional synthetic DMARD, targeted synthetic DMARD, and biologic DMARD. The appropriate use of these drugs has allowed remission to be the therapeutic goal in all patients. By maintaining remission, these drugs have also been shown to prevent the progression of joint destruction and physical dysfunction over a long period. The advent of molecular-targeted therapies has allowed for the use of treatments based on pathological mechanisms, and such therapeutic strategies have also been applied to the treatment of various autoimmune inflammatory diseases. In the future, safer and more effective treatments, therapeutic strategies aimed at drug holidays or cure, and the introduction of precision medicine are expected.