P460 Evaluation of potential mechanisms underlying the safety observations of filgotinib in clinical studies in rheumatoid arthritis

Abstract Background Inhibitors of the Janus kinase-signal transducers and activators of transcription (JAK-STAT) pathway have demonstrated efficacy in the treatment of rheumatoid arthritis (RA) and inflammatory bowel disease (IBD). Differences in selectivity of JAK inhibitors for JAK1, JAK2, JAK3 and TYK2 may influence their respective safety profiles, and the mechanisms responsible are not currently known. Filgotinib (FIL), a JAK1 inhibitor, did not negatively impact haemoglobin, LDL:HDL ratios or natural killer (NK) cell counts in clinical trials. Here, we compare the in vitro mechanistic profiles of four JAK inhibitors at clinically relevant doses. Methods JAK inhibitors (FIL, FIL metabolite [GS-829845], baricitinib [BARI], tofacitinib [TOFA], and upadacitinib [UPA]) were evaluated in vitro in human-cell-based assays. Growth of erythroid progenitors from human cord blood CD34+ cells was assessed using a HemaTox™ liquid expansion assay, NK cell proliferation was induced by IL-15 and LXR agonist-induced cholesteryl ester transfer protein (CETP) expression was assessed in the hepatic cell line, HepG2. Using assay-generated IC50 values and the reported human plasma concentrations from clinical studies, we calculated the target coverage for each JAK inhibitor at clinically relevant doses. The activity of FIL in humans was based on PK/PD modelling of FIL + GS-829845. Results Inhibition of cellular activity was calculated for each JAK inhibitor based on in vitro dose-response data, human exposure data and modelled PK/PD relationships. At clinically relevant doses, FIL resulted in lower calculated inhibition of NK cell proliferation compared with other JAK inhibitors. FIL 100 mg and 200 mg also reduced CETP expression, whereas other JAK inhibitors had no effect. There was no difference in the effect of FIL vs. other JAK inhibitors on erythroid progenitor cell differentiation or maturation. Conclusion FIL, a JAK1 inhibitor, resulted in less inhibition of NK cell proliferation compared with BARI, TOFA, and UPA. FIL also reduced LXR agonist-induced CETP expression, while the other inhibitors did not alter these levels. These results provide a potential mechanistic link between the observed reduction of CETP concentration following FIL treatment and the previously observed reduction in the LDL:HDL ratio in RA patients.

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POS0224 SELECTIVITY OF CLINICAL JAK INHIBITORS AND THE IMPACT ON NATURAL KILLER (NK) CELL FUNCTIONAL RESPONSES

Annals of the Rheumatic Diseases ◽

10.1136/annrheumdis-2021-eular.2741 ◽

2021 ◽

Vol 80 (Suppl 1) ◽

pp. 331.1-331

Author(s):

P. Gonzalez-Traves ◽

L. Simpson ◽

B. Murray ◽

A. Meng ◽

J. A. Di Paolo ◽

...

Keyword(s):

Cell Proliferation ◽

Nk Cells ◽

Nk Cell ◽

Janus Kinase ◽

Population Pharmacokinetic ◽

Pharmacokinetic Data ◽

Jak Inhibitors ◽

Functional Responses ◽

The Impact

Background:Janus kinase (JAK) inhibitors (JAKinibs) show similar efficacy in rheumatoid arthritis (RA). However, in vitro studies have shown differences in JAK selectivity profiles for baricitinib (BARI), tofacitinib (TOFA), upadacitinib (UPA) and filgotinib (FIL).1,2 These lead to distinct pharmacologic profiles in cellular signaling assays that may impact clinical efficacy or safety1. NK cells are innate lymphocytes important in anti-pathogen responses and immune surveillance, which function via production of cytokines and cell killing3. NK cell proliferation and IFNγ production are JAK-dependent pathways and may be modulated by JAKinibs. Clinical findings show transient decreases in NK cell numbers in patients treated with JAKinibs, but the link to safety is unclear4Objectives:To extend upon findings in proximal cell signaling assays, we compared the selectivity and potency of clinical JAKinibs on NK cell function by assessing proliferation mediated by IL-15 (JAK1/3) and IFN-γ production driven by IL-12 (JAK2/TYK2)+IL-18.Methods:NK cells were isolated from healthy donor PBMC, incubated in vitro with 8 concentrations of each evaluated JAKinib (TOFA, BARI, FIL, FIL metabolite, UPA) and stimulated with IL-15 for proliferation or IL-12/18 for IFNγ production. Proliferation was assessed by Cell Trace dye dilution after 6 days and IFNγ production by intracellular flow cytometry 4hrs post-stimulation. Half maximal inhibitory concentration (IC50) values were calculated for CD56bright, CD56dim, and total NK cells. Steady-state pharmacologic profile over a clinical dosing interval was modeled using concentration-time profiles from JAKinib population pharmacokinetic data in RA subjects under the therapeutic dose5-7. For each JAKinib, the time above IC50 and average daily inhibition of IFNγ or proliferation were calculated for each NK cell population in each donor.Results:Cellular assays in purified NK cells showed dose-dependent inhibition of IL-15-induced proliferation by all JAKinibs with TOFA showing the highest average inhibition and time above IC50 (35-60% inhibition for 8-15 hrs; TOFA>UPA>BARI≈FIL). The differences between JAKinibs are in line with differences in pSTAT inhibition downstream of IL-151. Interestingly, IL-12/18-induced production of IFNγ, which is mediated via JAK2/TYK2 (IL-12) and non-JAK dependent pathways (IL-18), showed weaker inhibition for all compounds. Moreover, all JAKinibs showed <25% average inhibition of IFNγ production over 24hrs and did not show any time above IC50 for IFNγ production or pSTAT4 inhibition at clinical doses. CD56dim and CD56bright sub-populations of NK cells are proposed to have distinct functions and unique expression of surface receptors. Analysis of the IC50 for pSTAT4 and IFNγ production showed ~2-10-fold weaker inhibition by JAKinibs in CD56bright NK cells, suggesting less dependence on JAK-dependent signals in CD56bright NK cells than CD56dim NK cells.Conclusion:NK cell proliferation depends on JAK1 and JAK3-mediated signaling and is differentially inhibited at clinical doses of distinct JAKinibs. In contrast, functional responses downstream of JAK2/TYK2-dependent IL-12/18 were not substantially inhibited by any of the JAKinibs studied. Inhibition of functional and proliferative responses in purified NK cells aligned well with proximal pSTAT inhibition. JAKinib modulation of NK cell proliferation, but not response to IL-12, reflects unique pharmacologic profiles of the drugs studied and could be one component underlying clinical safety observations, including increased risk of viral infections or malignancy4.References:[1]Traves PG et al. Ann Rheum Dis 2021 (in press)[2]McInnes IB, et al. Arthritis Res Ther 2019;21:183.[3]Cooper MA, Fehniger TA, Caligiuri MA. Trends Immunol 2001 Nov;22(11):633-40.[4]Winthrop KL. Nat Rev Rheumatol 2017; 13(4):234-243[5]Zhang X, et al. CPT Pharmacometrics Syst Pharmacol 2017;6(12):804-13.[6]CDER. Application Number: 203214Orig1s000. NDA 203214: Tofacitinib.[7]Klunder B et al. Clin Pharmacokinet 2019;58(8):1045-58.Disclosure of Interests:Paqui Gonzalez-Traves Shareholder of: Gilead Sciences, Employee of: Gilead Sciences, Laura Simpson Shareholder of: Gilead Sciences, Employee of: Gilead Sciences, Bernard Murray Shareholder of: Gilead Sciences, Employee of: Gilead Sciences, Amy Meng Shareholder of: Gilead Sciences, Employee of: Gilead Sciences, Julie A. Di Paolo Shareholder of: Gilead Sciences, Employee of: Gilead Sciences, Ethan Grant Shareholder of: Gilead Sciences, Employee of: Gilead Sciences, Gundula Min-Oo Shareholder of: Gilead Sciences, Employee of: Gilead Sciences

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Janus kinase inhibitors for the treatment of rheumatoid arthritis

Journal of Korean Medical Association ◽

10.5124/jkma.2021.64.2.105 ◽

2021 ◽

Vol 64 (2) ◽

pp. 105-108

Author(s):

Sun Hee Jang ◽

Ji Hyeon Ju

Keyword(s):

Rheumatoid Arthritis ◽

Kinase Inhibitors ◽

Interleukin 1 ◽

Janus Kinase ◽

Jak Inhibitor ◽

Jak Inhibitors ◽

Biologic Dmards ◽

Signal Transducers ◽

Refractory Rheumatoid Arthritis ◽

Stat Signaling

Rheumatoid arthritis is a chronic inflammatory destructive disorder that affects the joints, muscles, and tendons accompanying various extra-articular manifestations. Traditional disease-modifying anti-rheumatic drugs (DMARDs) represent the basic treatment for rheumatoid arthritis. Over the last 20 years, biologic DMARDs (tumor necrosis factor inhibitors, interleukin-1 inhibitors, interleukin-6 inhibitors, T cell inhibitors, and B cell inhibitors) have been widely used as a novel class of DMARDs that have efficacy and efficiency. Discovery of the underlying pathogenesis of autoimmune disease enables us to develop new target therapies such as a Janus kinase (JAK) inhibitor. Activated JAK is known to activate signal transducers as well as activators of transcription (STAT) signaling. A JAK inhibitor is a type of medication that functions by inhibiting the JAK-STAT signaling pathway. In addition, it is easy to take a JAK inhibitor orally. In Korea, several JAK inhibitors have been approved. This review describes the types of JAK inhibitors, recommended doses, side effects, and updated European Alliance of Associations for Rheumatology guidelines. Clinicians should more often consider JAK inhibitors in the treatment of refractory rheumatoid arthritis in current rheumatology clinics

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More Unnecessary Imaginary Worlds - Part 1: The Institute for Clinical and Economic Review’s Evidence Report on Janus Kinase (JAK) Inhibitors in Rheumatoid Arthritis

INNOVATIONS in pharmacy ◽

10.24926/iip.v11i1.2402 ◽

2020 ◽

Vol 11 (1) ◽

pp. 2

Author(s):

Paul Langley

Keyword(s):

Quality Of Life ◽

Rheumatoid Arthritis ◽

Incremental Cost ◽

Measurement Theory ◽

Janus Kinase ◽

Measurement Means ◽

Normal Science ◽

Jak Inhibitor ◽

Jak Inhibitors

Previous commentaries in the Formulary Evaluation section of INNOVATIONS in Pharmacy have pointed to the lack of credibility in modeled claims for cost-effectiveness and associated recommendations for pricing by the Institute for Clinical and Economic Review (ICER). The principal objection to ICER reports has been that their modeled claims fail the standards of normal science: they are best seen as pseudoscience. The purpose of this latest commentary is to consider the recently released ICER evidence report for Janus Kinase (JAK) Inhibitors. As ICER continues, in the case of JAK Inhibitors, to apply its modeled cost utility framework with consequent recommendations for pricing adjustments, these recommendations also lack credibility. In contrast with previous ICER evidence reports, the present report adopts only a 12-month timeframe, one due, in large part, to ICER being unable to justify assumptions to drive its construction of imaginary worlds beyond 12 months. This commentary emphasizes again, why the ICER methodology fails to meet the standards of normal science. Claims made by ICER for the competing JAK Inhibitor therapies lack credibility, are impossible to evaluate, let alone replicate across treatment settings. Even so, it is important to examine a number of key elements in the ICER invention of the 12-month JAK Inhibitor imaginary world. While this does not imply any degree of acceptance of the ICER methodology, one element that merits particular attention is the failure of the ICER modeling to meet logically defensible measurement standards in its application of generic health related quality of life (HRQoL) ordinal metrics to create its QALY claims. The failure to meet the required standards of fundamental measurement means that the cost-per-QALY claims are invalid. This raises the issue of the application of Rasch Measurement Theory (RMT) in instrument development and the potential role of patient centric outcome (PCO) instruments that represent the patient voice in value claims. The case made here is that the ICER approach should be abandoned as an unnecessary distraction. If we are to meet standards for the discovery of new facts in therapy response then our focus must be on proposing credible, evaluable and replicable claims within disease states. Instruments, such as the Rheumatoid Arthritis Quality of Life (RAQoL) questionnaire that build on the common construct that QoL is the extent to which human needs are fulfilled should be the basis for value claims. HRQoL Instruments that are clinically focused and reflect the value calculus of providers and not patients in measuring response by symptoms and activity limitations are irrelevant. This puts to one side the belief that incremental cost-per-QALY models, the construction of imaginary worlds are, in any sense, a ‘gold standard’; a meme embraced by the health technology assessment profession. Claims for incremental cost per QALY outcomes and recommendations for pricing and access driven by willingness to pay thresholds are irrelevant to formulary decisions. Article Type: Commentary

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Inhibitory Effect of Curcumol on Jak2-STAT Signal Pathway Molecules of Fibroblast-Like Synoviocytes in Patients with Rheumatoid Arthritis

Evidence-based Complementary and Alternative Medicine ◽

10.1155/2012/746426 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 2

Author(s):

Heng Wang ◽

Yongfei Fang ◽

Yong Wang ◽

Zhizhong Wang ◽

Qinghua Zou ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

Cell Proliferation ◽

Dna Binding ◽

Dna Synthesis ◽

Synovial Membrane ◽

Signal Pathway ◽

Janus Kinase ◽

Protein Expressions ◽

Fibroblast Like Synoviocytes

Hyperplasia of synovial membrane in rheumatoid arthritis (RA) is a critical pathological foundation for inducing articular injury. The janus kinase and signal transducer and activator of transcription (Jak-STAT) pathway plays a critical role in synovial membrane proliferation induced by platelet-derived growth factor (PDGF). To explore the anti-cell proliferation mechanism of curcumol, a pure monomer extracted from Chinese medical plantzedoary rhizome, the changes of Jak2-STAT1/3 signal pathway-related molecules in synoviocytes were observedin vitro. In this study, the fibroblast-like synoviocytes (FLS) in patients with RA were collected and cultured. The following parameters were measured: cell proliferation (WST-1 assay), cell cycles (fluorescence-activated cell sorting, FACS), STAT1 and STAT3 activities (electrophoretic mobility shift assay, EMSA), and the protein expressions of phosphorylated Jak2, STAT1, and STAT3 (Western blot). It was shown that curcumol could inhibit the RA-FLS proliferation and DNA synthesis induced by PDGF-BB in a dose-dependent mannerin vitro. The transcription factors activities of STAT1 and STAT3 were obviously elevated after PDGF-BB stimulation (P<0.05). Super-shift experiments identified the STAT1 or STAT3 proteins in the complex. Furthermore, the different concentration curcumol could downregulate the DNA binding activities of STAT1 and STAT3 (P<0.05) and inhibit the phosphorylation of Jak2 while it had no effect on the protein expressions of STAT1 and STAT3. Positive correlations were found between changes of cell proliferation and DNA-binding activities of STAT1 and STAT3, respectively (P<0.01). In conclusion, curcumol might suppress the FLS proliferation and DNA synthesis induced by PDGF-BB through attenuating Jak2 phosphorylation, downregulating STAT1 and STAT3 DNA-binding activities, which could provide theoretical foundation for clinical treatment of RA.

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Topical Tofacitinib: A Janus Kinase Inhibitor for the Treatment of Vitiligo in an Adolescent Patient

Case Reports in Dermatology ◽

10.1159/000513938 ◽

2021 ◽

pp. 190-194

Author(s):

Sineida Berbert Ferreira ◽

Rachel Berbert Ferreira ◽

Afonso Cesar Neves Neto ◽

Silvana Martins Caparroz Assef ◽

Morton Scheinberg

Keyword(s):

Case Report ◽

Skin Disease ◽

Kinase Inhibitor ◽

Effective Therapy ◽

Janus Kinase ◽

Jak Inhibitor ◽

Adolescent Patient ◽

Jak Inhibitors ◽

Janus Kinase Inhibitor ◽

History Of

Vitiligo is an autoimmune skin disease presenting with areas of depigmentation. Recent reports suggest that Janus kinase (JAK) inhibitors may be an effective therapy. In this case report, we show our experience with an adolescent patient with a long history of generalized and refractory vitiligo, for which treatment with topical tofacitinib, a JAK inhibitor, associated with phototherapy for 9 months, resulted in near complete repigmentation.

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THU0206 А VERY EARLY (7-28 DAYS) RESPONSE ON JAK INHIBITOR TOFACITINIB IN PATIENTS WITH ACTIVE RHEUMATOID ARTHRITIS: EFFECT ON PAIN AND CENTRAL SENSITIZATION.

Annals of the Rheumatic Diseases ◽

10.1136/annrheumdis-2020-eular.4029 ◽

2020 ◽

Vol 79 (Suppl 1) ◽

pp. 327.3-327

Author(s):

A. Karateev ◽

E. Filatova ◽

E. Pogozheva ◽

V. Amirdzhanova ◽

E. Nasonov ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

Central Sensitization ◽

Early Time ◽

National Registry ◽

Genetically Engineered ◽

Pain Severity ◽

Signal Pathways ◽

Jak Inhibitor ◽

Jak Inhibitors ◽

Biological Drugs

Background:The presence of central sensitization (CS) significantly burdens the course of rheumatoid arthritis (RA). JAK inhibitors block intracellular signal pathways including the ones responsible for synthesis of mediators and cytokines causing pain and CS. The application of JAK inhibitors is supposed to relieve pain and reduce CS severity promptly.Objectives:To evaluate JAK inhibitor effect on pain and signs of CS in patients with active RA 7 and 28 days after the start of therapy.Methods:Study group included 39 patients with RA, their age was 50.9±11.1, 79.5% of women, 89.7% of RF “+”, DAS28 5.8±0.6, receiving DMARDs (methotrexate 82.0% and leflunomide 18.0%), who were administered with tofacitinib 5 mg 2 times a day due to inefficiency or intolerance of genetically engineered biological drugs. There were assessed the pain severity using Brief pain inventory (BPI) questionnaire, the presence of neuropathic pain component (NPC) using PainDETECT questionnaire and signs of CS using Central Sensitisation Inventory (CSI) questionnaire at early time after tofacitinib administration.Results:Patients initially experienced a severe pain – 5.72±2.21 according to the visual analogue scale (VAS), 53.8% had signs of central sensitization (CSI ≥ 40), 17.9% had NPC (PainDETECT ≥18). 7 days after tofacitinib intake there was statistically reliable reduction of pain severity – up to 4.37±2.2 (р=0.01), pain decrease of 29.4±17.9% (BPI), NCP – PainDETECT from 12.9±5.5 to 10.6±5.6 (р=0.047) and CS – CSI from 43.1±12.8 to 35.9±11.2 (р=0.01). The effect had increased after 28 days: pain level (VAS) was 2.84±1.57 (р=0.000), pain decrease of 43.6±29.6% (BPI), PainDETECT 29.8±12.4 (р=0.000), CSI 26.4±13.9 (р=0.000).During this period there were no serious adverse reactions.Conclusion:The application of JAK inhibitor tofacitinib allows to reach a fast analgesic effect, also due to impact on CS and NCP.Source: National Registry patients with RADisclosure of Interests: :Andrey Karateev: None declared, Ekaterina Filatova: None declared, Elena Pogozheva: None declared, Vera Amirdzhanova: None declared, Evgeny Nasonov: None declared, Alexander Lila: None declared, V Mazurov: None declared, N Lapkina: None declared, Galina Lukina Speakers bureau: Novartis, Pfizer, UCB, Abbvie, Biocad, MSD, Roche, Tatiana Salnikova: None declared, Ruzana Samigullina: None declared, Diana Chakieva: None declared, Irina Marusenko: None declared, Olga Semagina: None declared, Marina Semchenkova: None declared

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Risk of infection associated with Janus Kinase (JAK) inhibitors and biological therapies in inflammatory intestinal disease and rheumatoid arthritis. Prevention strategies

Gastroenterología y Hepatología (English Edition) ◽

10.1016/j.gastre.2021.01.003 ◽

2021 ◽

Vol 44 (8) ◽

pp. 587-598

Author(s):

Xavier Calvet ◽

Daniel Carpio ◽

Iago Rodríguez-Lago ◽

Rosario García-Vicuña ◽

Manuel Barreiro-de-Acosta ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

Janus Kinase ◽

Intestinal Disease ◽

Biological Therapies ◽

Risk Of Infection ◽

Prevention Strategies ◽

Jak Inhibitors

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Tofacitinib Suppresses Several JAK-STAT Pathways in Rheumatoid Arthritis In Vivo and Baseline Signaling Profile Associates With Treatment Response

Frontiers in Immunology ◽

10.3389/fimmu.2021.738481 ◽

2021 ◽

Vol 12 ◽

Author(s):

Maaria Palmroth ◽

Krista Kuuliala ◽

Ritva Peltomaa ◽

Anniina Virtanen ◽

Antti Kuuliala ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

T Cells ◽

Treatment Response ◽

Peripheral Blood ◽

Janus Kinase ◽

Cytokine Signaling ◽

Stat3 Phosphorylation ◽

Stat Pathway

ObjectiveCurrent knowledge on the actions of tofacitinib on cytokine signaling pathways in rheumatoid arthritis (RA) is based on in vitro studies. Our study is the first to examine the effects of tofacitinib treatment on Janus kinase (JAK) - signal transducer and activator of transcription (STAT) pathways in vivo in patients with RA.MethodsSixteen patients with active RA, despite treatment with conventional synthetic disease-modifying antirheumatic drugs (csDMARDs), received tofacitinib 5 mg twice daily for three months. Levels of constitutive and cytokine-induced phosphorylated STATs in peripheral blood monocytes, T cells and B cells were measured by flow cytometry at baseline and three-month visits. mRNA expression of JAKs, STATs and suppressors of cytokine signaling (SOCS) were measured from peripheral blood mononuclear cells (PBMCs) by quantitative PCR. Association of baseline signaling profile with treatment response was also investigated.ResultsTofacitinib, in csDMARDs background, decreased median disease activity score (DAS28) from 4.4 to 2.6 (p < 0.001). Tofacitinib treatment significantly decreased cytokine-induced phosphorylation of all JAK-STAT pathways studied. However, the magnitude of the inhibitory effect depended on the cytokine and cell type studied, varying from 10% to 73% inhibition following 3-month treatment with tofacitinib. In general, strongest inhibition by tofacitinib was observed with STAT phosphorylations induced by cytokines signaling through the common-γ-chain cytokine receptor in T cells, while lowest inhibition was demonstrated for IL-10 -induced STAT3 phosphorylation in monocytes. Constitutive STAT1, STAT3, STAT4 and STAT5 phosphorylation in monocytes and/or T cells was also downregulated by tofacitinib. Tofacitinib treatment downregulated the expression of several JAK-STAT pathway components in PBMCs, SOCSs showing the strongest downregulation. Baseline STAT phosphorylation levels in T cells and monocytes and SOCS3 expression in PBMCs correlated with treatment response.ConclusionsTofacitinib suppresses multiple JAK-STAT pathways in cytokine and cell population specific manner in RA patients in vivo. Besides directly inhibiting JAK activation, tofacitinib downregulates the expression of JAK-STAT pathway components. This may modulate the effects of tofacitinib on JAK-STAT pathway activation in vivo and explain some of the differential findings between the current study and previous in vitro studies. Finally, baseline immunological markers associate with the treatment response to tofacitinib.

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Kynurenic Acid in Synovial Fluid and Serum of Patients with Rheumatoid Arthritis, Spondyloarthropathy, and Osteoarthritis

The Journal of Rheumatology ◽

10.3899/jrheum.121035 ◽

2013 ◽

Vol 40 (6) ◽

pp. 903-909 ◽

Cited By ~ 5

Author(s):

Jolanta Parada-Turska ◽

Wojciech Zgrajka ◽

Maria Majdan

Keyword(s):

Rheumatoid Arthritis ◽

Regression Analysis ◽

Synovial Fluid ◽

Blood Cell ◽

Red Blood Cell ◽

High Performance ◽

Kynurenic Acid ◽

Linear Regression Analysis ◽

Cell Counts

Objective.Previously we demonstrated that kynurenic acid (KYNA), an endogenous metabolite of kynurenine, is present in the synovial fluid of patients with rheumatoid arthritis (RA). KYNA inhibits proliferation of synoviocytesin vitro. The goal of our study was to compare KYNA concentrations in synovial fluid and blood of patients with RA, inflammatory spondyloarthropathies (SpA), and osteoarthritis (OA).Methods.Serum and synovial fluid samples were obtained from 189 patients with RA, 56 patients with SpA, and 32 patients with OA. KYNA was separated using a high-performance liquid chromatography system and measured fluorometrically.Results.KYNA concentration in synovial fluid obtained from patients with RA and SpA was significantly lower than that in patients with OA (p < 0.05). The concentration of KYNA in serum of patients with RA, SpA, and OA did not differ among all groups studied. The positive correlation between KYNA content in synovial fluid and serum was found in patients with RA (p < 0.05). Univariate linear regression analysis demonstrated that fibrinogen was significantly associated with KYNA in synovial fluid (p < 0.05), and red blood cell counts, morning stiffness, and pain scores were significantly associated with KYNA level in serum (all p < 0.05). Multivariate regression analysis revealed correlation between the following independent variables: hemoglobin level, hematocrit, red blood cell count in conjunction with age and KYNA content in synovial fluid. A lack of correlation was observed between KYNA content in synovial fluid of patients with RA and other clinical and laboratory measures of disease activity.Conclusion.Our data show a local deficit of KYNA in inflammatory states.

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