Background and purpose: Rheumatoid arthritis (RA) is a chronic inflammatory disease. Histone deacetylase inhibitors (HDACi), a new class of anti-cancer agents, have recently been reported to exhibit potent anti-inflammatory activities. A proof of concept study was carried out with suberoylanilide hydroxamic acid (SAHA) and MS-275, two HDACi currently undergoing clinical investigations for various oncological indications. Experimental approach: The anti-rheumatic effects of SAHA and MS-275 were assessed in both mouse and rat collagen induced arthritis (CIA) models. Key results: SAHA exhibited moderate prophylactic efficacy. It attenuated paw swelling due to inflammation, decreased bone erosion in both mice and rats and reduced slightly the RA-induced bone resorption in rats. However, SAHA could not inhibit the onset of arthritis. In contrast, MS-275 displayed dramatic anti-rheumatic activities. In prophylactic intervention, high doses of MS-275 prevented bone erosion and markedly delayed the onset of arthritis; at low doses, MS-275 strongly attenuated paw swelling, bone erosion, and bone resorption associated with RA. Furthermore, the therapeutic efficacy of MS-275 was also documented. After the onset of arthritis, it could stop the disease progression and joint destruction.. An anti inflammatory effect of MS-275 was also confirmed through its capacity to decrease serum IL-6 and IL-1b levels in the CIA induced mouse model. The anti-rheumatic activity of MS-275 was also confirmed through histological observation. No synovial hyperplasia, pannus formation, cartilage or bone destruction were observed in the high dose prophylactic intervention in mice. Conclusion and implication: This study strongly supported HDACi as an innovative therapeutic strategy for RA.

The JAKs receive continued interest as therapeutic targets for autoimmune, inflammatory, and oncological diseases. JAKs play critical roles in the development and biology of the hematopoietic system, as evidenced by mouse and human genetics. JAK1 is critical for the signal transduction of many type I and type II inflammatory cytokine receptors. In a search for JAK small molecule inhibitors, GLPG0634 was identified as a lead compound belonging to a novel class of JAK inhibitors. It displayed a JAK1/JAK2 inhibitor profile in biochemical assays, but subsequent studies in cellular and whole blood assays revealed a selectivity of ∼30-fold for JAK1- over JAK2-dependent signaling. GLPG0634 dose-dependently inhibited Th1 and Th2 differentiation and to a lesser extent the differentiation of Th17 cells in vitro. GLPG0634 was well exposed in rodents upon oral dosing, and exposure levels correlated with repression of Mx2 expression in leukocytes. Oral dosing of GLPG0634 in a therapeutic set-up in a collagen-induced arthritis model in rodents resulted in a significant dose-dependent reduction of the disease progression. Paw swelling, bone and cartilage degradation, and levels of inflammatory cytokines were reduced by GLPG0634 treatment. Efficacy of GLPG0634 in the collagen-induced arthritis models was comparable to the results obtained with etanercept. In conclusion, the JAK1 selective inhibitor GLPG0634 is a promising novel therapeutic with potential for oral treatment of rheumatoid arthritis and possibly other immune-inflammatory diseases.

IL-17C is a functionally distinct member of the IL-17 family that was believed to play a role in the pathogenesis of psoriasis. Here we confirmed that IL-17C is involved in psoriasis and explored potential roles for IL-17C in atopic dermatitis (AD). An anti-IL-17C antibody, MOR106, was generated that potently and selectively binds to human and mouse IL-17C, thereby inhibiting the binding of IL-17C to its IL-17RE receptor. The antibody inhibited cutaneous inflammation in an IL-23-induced psoriatic-like skin inflammation model. In lesional skin of patients with AD, IL-17C expression levels were increased and localized to keratinocytes and infiltrating immune cells. To determine the contribution of IL-17C to AD pathogenesis, MOR106 was tested in two distinct in vivo models. In the calcipotriol-induced AD model, ear skin inflammation, TSLP, and IL-33 protein production in ears was suppressed by MOR106. Consistently, in the flaky tail strain mouse model, spontaneous development of AD-like skin inflammation was reduced by MOR106. Moreover, serum IgE levels, number of mast cells in skin and T helper type 2-related cytokines IL-4 and CCL17 in serum were all reduced. Overall, our results indicate that IL-17C is a central mediator of skin inflammation beyond psoriasis and is relevant in particular in AD.

Janus kinases (JAK1, JAK2, JAK3, and TYK2) are involved in the signaling of multiple cytokines important in cellular function. Blockade of the JAK-STAT pathway with a small molecule has been shown to provide therapeutic immunomodulation. Having identified JAK1 as a possible new target for arthritis at Galapagos, the compound library was screened against JAK1, resulting in the identification of a triazolopyridine-based series of inhibitors represented by 3. Optimization within this chemical series led to identification of GLPG0634 (65, filgotinib), a selective JAK1 inhibitor currently in phase 2B development for RA and phase 2A development for Crohn's disease (CD).

Background Key pathogenic events of psoriasis and atopic eczema (AE) are misguided immune reactions of the skin. IL‐17C is an epithelial‐derived cytokine, whose impact on skin inflammation is unclear. Objective We sought to characterize the role of IL‐17C in human ISD. Methods IL‐17C gene and protein expression was assessed by immunohistochemistry and transcriptome analysis. Primary human keratinocytes were stimulated and expression of cytokines chemokines was determined by qRT‐PCR and luminex assay. Neutrophil migration towards supernatant of stimulated keratinocytes was assessed. IL‐17C was depleted using a new IL‐17C‐specific antibody (MOR106) in murine models of psoriasis (IL‐23 injection model) and AE (MC903 model) as well as in human skin biopsies of psoriasis and AE. Effects on cell influx (mouse models) and gene expression (human explant cultures) were determined. Results Expression of IL‐17C mRNA and protein was elevated in various ISD. We demonstrate that IL‐17C potentiates the expression of innate cytokines, antimicrobial peptides (IL‐36G, S100A7 and HBD2) and chemokines (CXCL8, CXCL10, CCL5 and VEGF) and the autocrine induction of IL‐17C in keratinocytes. Cell‐free supernatant of keratinocytes stimulated with IL‐17C was strongly chemotactic for neutrophils, thus demonstrating a critical role for IL‐17C in immune cell recruitment. IL‐17C depletion significantly reduced cell numbers of T cells, neutrophils and eosinophils in murine models of psoriasis and AE and led to a significant downregulation of inflammatory mediators in human skin biopsies of psoriasis and AE ex vivo. Conclusion IL‐17C amplifies epithelial inflammation in Th2 and Th17 dominated skin inflammation and represents a promising target for the treatment of ISD.

IntroductionDisease severity in collagen-induced arthritis (CIA) is commonly assessed by clinical scoring of paw swelling and histological examination of joints. Although this is an accurate approach, it is also labour-intensive and the application of less invasive and less time-consuming methods is of great interest. However, it is still unclear which of these methods represents the most discriminating measure of disease activity.MethodsWe undertook a comparative analysis in which different measurements of inflammation and tissue damage in CIA were studied on an individual mouse level. We compared the current gold standard methods - clinical scoring and histological examination - with alternative methods based on scoring of X-ray or micro-computed tomography (CT) images and investigated the significance of systemically expressed proteins, involved in CIA pathogenesis, that have potential as biomarkers.ResultsLinear regression analysis revealed a marked association of serum matrix metalloproteinase (MMP)-3 levels with all features of CIA including inflammation, cartilage destruction and bone erosions. This association was improved by combined detection of MMP-3 and anti-collagen IgG2a antibody concentrations. In addition, combined analysis of both X-ray and micro-CT images was found to be predictive for cartilage and bone damage. Most remarkably, validation analysis using an independent data set proved that variations in disease severity, induced by different therapies, could be accurately represented by predicted values based on the proposed parameters.ConclusionsOur analyses revealed that clinical scoring, combined with serum MMP-3, anti-collagen IgG2a measurement and scoring of X-ray and micro-CT images, yields a comprehensive insight into the different aspects of disease activity in CIA.

Bone development is a multistep process that includes patterning of skeletal elements, commitment of hematopoietic and/or mesenchymental cells to chondrogenic and osteogenic lineages, and further differentiation into three specialized cell types: chondrocytes in cartilage and osteoblasts and osteoclasts in bone. Although PRL has a multitude of biological actions in addition to its role in the mammary gland, very little is known about its effect on bone. Mice carrying a germline null mutation for the PRL receptor gene have been produced in our laboratory and used to study the role of PRL in bone formation. In -/- embryos, we observed an alteration in bone development of calvaria. In adults, histomorphometric analysis showed that the absence of PRL receptors leads to a decrease in bone formation rate using double calcein labeling and a reduction of bone mineral density, measured by dual energy x-ray absorptiometry. In addition, serum estradiol, progesterone, testosterone, and PTH levels were analyzed. We also established that osteoblasts, but not osteoclasts, express PRL receptors. This suggests that an effect of PRL on osteoblasts could be required for normal bone formation and maintenance of bone mass. Thus, the PRL receptor knockout mouse model provides a new tool to investigate the involvement of PRL in bone metabolism.

Objective: A disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) is a key enzyme in degradation of cartilage in osteoarthritis (OA). We report the pharmacological characterization of GLPG1972/S201086, a new, potent and selective small-molecule ADAMTS5 inhibitor. Methods: Potency and selectivity of GLPG1972/S201086 for ADAMTS5 were determined using fluorescently-labeled peptide substrates. Inhibitory effects of GLPG1972/S201086 on interleukin-1a-stimulated glycosaminoglycan release in mouse femoral head cartilage explants, and on interleukin-1bstimulated release of an ADAMTS5-derived aggrecan neoepitope (quantified with ELISA) in human articular cartilage explants were determined. In the destabilization of the medial meniscus (DMM) mouse and menisectomized (MNX) rat models, effects of oral GLPG1972/S201086 on relevant OA histological and histomorphometric parameters were evaluated. Results: GLPG1972/S201086 inhibited human and rat ADAMTS5 (IC 50 ± SD: 19 ± 2 nM and <23 ± 1 nM, respectively), with 8-fold selectivity over ADAMTS4, and 60e>5,000-fold selectivity over other related proteases in humans. GLPG1972/S201086 dose-dependently inhibited cytokine-stimulated aggrenolysis in mouse and human cartilage explants (100% at 20 mM and 10 mM, respectively). In DMM mice, GLPG1972/S201086 (30e120 mg/kg b.i.d) vs vehicle reduced femorotibial cartilage proteoglycan loss (23 e37%), cartilage structural damage (23e39%) and subchondral bone sclerosis (21e36%). In MNX rats, GLPG1972/S201086 (10e50 mg/kg b.i.d) vs vehicle reduced cartilage damage (OARSI score reduction, 6 e23%), and decreased proteoglycan loss (~27%) and subchondral bone sclerosis (77e110%). Conclusions: GLPG1972/S201086 is a potent, selective and orally available ADAMTS5 inhibitor, demonstrating significant protective efficacy on both cartilage and subchondral bone in two relevant in vivo preclinical OA models.