April 2014

Molecular pathways: Molecular basis for sensitivity and resistance to JAK inhibitors

Clin Cancer Research doi:10.1158/1078-0432.CCR-13-0279

Janus kinases (JAKs) mediate the regulation of a variety of cytokine signals with alterations in JAK1, JAK2, JAK3 and Tyk2 signalling contributing to many disease states including autoimmune diseases and haematological malignancies. Recently tofacitinib and ruxolitinib have been approved for treatment for rheumatoid arthritis and myelofibrosis respectively. Several JAK2 inhibitors, such as momelotinib and pacritinib, currently in development for myelofibrosis and the JAK1/2 inhibitor baricitinib...

Keywords:

Effects of Janus Kinase Inhibitor tofacitinib on circulating serum amyloid A and interlukin-6 during treatment for rheumatoid arthritis

Clinical and Experimental Immunology doi.10.1111/cei.12234

Tofacitinib is a JAK inhibitor currently approved for the treatment of RA in some parts of the world. In this paper, Migita et al tested the effects of tofacitinib on circulating serum amyloid A (SAA). SAA is a major acute-phase reactant in RA and studies have shown it may be a better marker for the assessment of inflammatory joint disease compared with C-reactive protein. SAA is induced by the binding of IL-6 and the activation of the JAK/STAT pathway, which is inhibited by tofacitinib. Results...

Keywords:

March 2014

Inhibition of TAK1 and/or JAK can rescue impaired chondrogenic differentiation of human mesenchymal stem cells in osteoarthritis-like conditions

Tissue Engineering Part A doi:10/1089/ten.TEA.2013.0553

As it is nonvascularized and noninnervated, articular cartilage has a limited capacity to repair which presents a major clinical problem. In order to circumvent this inability to repair, stem cells can be placed into the joint or stimulated within the bone marrow. However, as the cartilage requiring repair is often in diseased joints, the factors involved in the disease state are potentially non-beneficial to the chondrogenesis of mesenchymal stem cells. In this study van Beuningen et al. invest...

Keywords:

February 2014

Rheumatoid arthritis pathophysiology: update on emerging cytokine and cytokine-associated cell targets

Rheumatology doi:10.1093/rheumatology/ket414

Despite biologic therapies greatly improving the treatment of rheumatoid arthritis, many patients do not respond to current treatments or do not maintain response to these treatments. This review covers the evidence for the newly discovered role of Th17 cells, IL-12 and IL-17 family of cytokines in the pathogenesis of RA as well as the development of new therapies targeting these cytokines. With current biologics targeting cytokines such as TNF, IL-1ß and IL-6, the discovery of the Th17 subset o...

Keywords:

Efficacy of conventional synthetic disease-modifying antirheumatic drugs, glucocorticoids and tofacitinib: a systematic literature review informing the 2013 update of the EULAR recommendations for the management of rheumatoid arthritis

Ann Rheum Dis doi:10.1136/annrheumdis-2013-204588

Systematic literature reviews were undertaken to assess the efficacy of csDMARDs, glucocorticoids and tofacitinib in the treatment of RA. The first two were updates to reviews conducted for the 2010 recommendations while the tofacitinib SLR was a complete review.Two studies identified by the csDMARD SLR, tREACH and TEAR, compared efficacy between MTX mono- and combination therapy (MTX+SSZ+HQ). Both of these studies found there was no benefit to immediate triple therapy.Further studies analysing ...

Keywords:

Safety of synthetic and biological DMARDs: a systematic literature review informing the 2013 update of the EULAR recommendations for the management of rheumatoid arthritis

Ann Rheum Dis doi:10.1136/annrheumdis-2013-204575

Two systematic literature reviews were undertaken to update the safety findings on synthetic and biological DMARDs in order to inform the updates to the EULAR recommendations to the treatment of RA. Of 10,559 articles screened, 49 were included for review covering a diverse range of outcomes. In the main these showed the patients on bDMARDs had a significantly greater risk of serious infections and tuberculosis compared with csDMARDs, while differences in data between studies mean a slight incre...

Keywords:

Effects of tofacitinib on lymphocytes in rheumatoid arthritis: relation to efficacy and infectious adverse events

Rheumatology doi:10.1093/rheumatology/ket466

Due to its function as a JAK1/3 inhibitor, tofacitinib has effects on a wide ranging variety of cells. The authors of this paper have previously reported a suppression in cytokine production by CD4+ T lymphocytes caused by tofacitinib, while others have reported reduced chemokine production from fibroblast-like synoviocytes. The effects of tofacitinib on other cells however remain largely unknown. This study focused on tofacitinib’s effects on CD4+ T lymphocyte proliferation and on subsets of ly...

Keywords:

January 2014

PI3K-δ and PI3K-γ inhibition by IPI-145 abrogates immune responses and suppresses activity in autoimmune and inflammatory disease models

Chemistry and Biology Nov 13 20, 1364-1374

Phosphoinositide-3 kinases (PI3K) are cell signalling proteins that act as a central node for relaying signals from cell surface receptors and downstream mediators. Specifically they phosphorylate phosphatidylinositol to phosphatidylinositol-3,4,5-trisphosphate (PIP3). This acts a docking site for signalling proteins, leading to the activation of downstream effectors such as BTK. Therefore, inhibition of the PI3K-d and PI3K-? isoforms (PI3K-a and PI3K-ß demonstrated embryonic lethality in murine...

Keywords:

Emerging cell and cytokine targets in rheumatoid arthritis

Nat Rev Rheumatol. 2013. doi:10.1038/nrrheum.2013.168

Despite major progress in the treatment of RA over the past decade, sustained clinical remission remains elusive. The identification of new treatment targets is therefore necessary, with much research currently being undertaken in this area. Novel therapeutic approaches currently being investigated include T cell-directed therapies targeting both T cell activation and regulation; and the targeting of pathogenic B cell functions, including the use of depleting and non-depleting B cell-directed an...

Keywords:

Preclinical to Clinical Translation of Tofacitinib, a Janus Kinase Inhibitor, in Rheumatoid Arthritis

J Pharmacol Exp Ther. 2013. DOI:10.1124/jpet.113.209304

Preclinical studies can provide insight into mechanisms of efficacy and optimal dosing regimens. In this study, Dowty et al. compare the pharmacokinetic / pharmacodynamic profiles of tofacitinib in a murine arthritis model and in patients with rheumatoid arthritis from tofacitinib clinical trials. The main driver of efficacy in both preclinical murine arthritis models and clinical RA was found to be inhibition of JAK1 heterodimer signalling, where total drug exposure (Cave) was a predictor of pr...

Keywords: