October 2020

Tofacitinib and Baricitinib Are Taken up by Different Uptake Mechanisms Determining the Efficacy of Both Drugs in RA

Int. J. Mol. Sci. 2020; 21:6632 DOI: 10.3390/ijms21186632

Amrhein et al examined the different uptake and expulsion mechanisms of BARI and TOF in cellular assays. Different cellular uptake mechanism for BARI and TOF was observed and showed that BARI’s transport was not dependent on organic cation transporters. Results indicated TOF was exported from RASF in a MATE-1 dependent way. TOF might be exported from healthy cells, thereby not inhibiting JAK pathway in these cellsThe interaction of BARI and TOF with OCTs was investigated using quenching experime...

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February 2020

Preferential Inhibition of JAK1 Relative to JAK3 by Upadacitinib: Exposure-Response Analyses of Ex Vivo Data From 2 Phase 1 Clinical Trials and Comparison to Tofacitinib

Pharmacodynamics. 2020

Ex vivo pharmacodynamic assay results demonstrated a greater selectivity of UPA on JAK1 versus JAK3 compared to TOF. This analysis conducted ex vivo stimulation of STAT3 phosphorylation by IL-6 as a measure of JAK1 activity and STAT5 phosphorylation by IL-7 as a measure of JAK1/JAK3 activity. Change in pSTAT3 and pSTAT5 were calculated at 1, 6 and 12 hours following drug administration using samples collected from healthy subjects and subjects with RA, from 2 phase 1 studies. Exposure-response m...

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October 2015

Tofacitinib regulates synovial inflammation in psoriatic arthritis, inhibiting STAT activation and induction of negative feedback inhibition

Annals of the Rheumatic Diseases. 2015 Sep 9. doi:10.1136/annrheumdis-2014-207201

Psoriatic arthritis (PsA) is a chronic inflammatory arthritis associated with psoriasis (Ps) and characterised by synovitis and progressive destruction of articular cartilage and bone. Recently developed agents for PsA target IL12p40, IL-6 and IL-17, several of which signal through the JAK family of receptor-associated tyrosine kinases. Tofacitinib is a drug of the JAK inhibitor class and is currently approved for the treatment of RA in 27 countries. This study evaluated the effect of tofacitini...

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December 2014

The activity of JAK-STAT pathways in rheumatoid arthritis: constitutive activation of STAT3 correlates with interleukin 6 levels

Rheumatology (Oxford). 2014 Nov 17. pii: keu430. [Epub ahead of print]

Non-response, parenteral administration and cost to produce are all aspects associated with the currently available anti-cytokine agents for RA. These related factors mean that alternative drugs are now being developed. Recent developments in therapeutic drugs to treat RA have focused on Janus kinases (JAKs) and signal transducer and activator of transcription (STATs) transcription pathways. Several cytokines that regulate immune responses in RA, such as IFN-g, IL-6 and IL-10, activate JAK-STAT ...

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May 2014

JAK2-STAT3 Blockade by AG490 Suppresses Autoimmune Arthritis in Mice via Reciprocal Regulation of Regulatory T cells and Th17 cells

J Immunol 2014; 192:4417-4424

In this study, Park et al sought to investigate the effects of the JAK2 inhibitor, AG490 in RA. Using murine CIA models, both preventative and therapeutic models were investigated. In the preventative model, CIA mice treated with AG490 showed a significantly lower incidence rate of arthritis and arthritic scores when compared to mice injected with vehicle. In the therapeutic model, as in the preventative, AG490 treated mice exhibited less severe arthritis. Through further experiments, it was dem...

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April 2014

Hypoxia and STAT3 signalling interactions regulate pro-inflammatory pathways in rheumatoid arthritis

. ARD published online first 13 Feb 2014. Doi: 10.1136/annrheumdis-2013-204105

Hypoxia is a key driving force in joint inflammation, however little is known about the effect it can have on JAK/STAT signalling in rheumatoid arthritis. Due to the development of JAK inhibitors as therapeutics it is important to understand any links there may be. Previous studies have shown that HIF1a, a protein associated with hypoxia, facilitates the binding of STAT3 to haptoglobin promoter in HepG2 human hepatoma cells. HIF1a also requires interaction of Notch signalling pathways with STAT3...

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January 2014

STA-21, a promising STAT3 inhibitor that reciprocally regulates Th17 and Treg, inhibits osteoclastgenesis and alleviates autoimmune inflammation

Arthritis and Rheumatism doi: 10.1002/art.38305

STAT3 (signal transducer and activator of transcription 3) is the major transcription factor in the differentiation of Th17 cells, which along with IL-17 are significant in the development of RA. STA-21 is a new small molecule with significant inhibitory effects on STAT3, impeding DNA binding activity, dimerization and STAT3-dependent luciferase activity. While the effect of STA-21 in RA has not been fully determined, it has been hypothesised that STA-21 will suppress arthritis in animal models ...

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October 2013

Inhibition of JAK/STAT signalling pathway in rheumatoid synovial fibroblasts using small molecule compounds

Clin Exp Immunol. 2013 Aug 23. doi: 10.1111/cei.12190

Current JAK inhibitors CP-690,550 and INCB020850 have inhibitory effects on multiple JAK pathways, therefore Migita et al. tested whether selective inhibition of JAK3, using PF-956980, would be enough to ameliorate the rheumatoid inflammatory process. The results indicated that the inhibition of JAK3 alone is does not achieve control of STAT3-dependent signalling, and while it is suggested that the targeting of singular JAK pathways should lead to fewer adverse events, it appears that this appro...

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