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Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation and the destruction of bone and cartilage in affected joints. One of the unmet medical needs in the treatment of RA is to effectively prevent the structural destruction of joints, especially bone, which progresses because of resistance to conventional drugs that mainly have anti-inflammatory effects, and directly leads to a decline in the QOL of patients. We previously developed a novel and orally available type II kinase inhibitor of colony-stimulating factor-1 receptor (CSF1R), JTE-952. CSF1R is specifically expressed by monocytic-lineage cells, including bone-resorbing osteoclasts, and is important for promoting the differentiation and proliferation of osteoclasts. In the present study, we investigated the therapeutic effect of JTE-952 on methotrexate (MTX)-refractory joint destruction in a clinically established adjuvant-induced arthritis rat model. JTE-952 did not suppress paw swelling under inflammatory conditions, but it inhibited the destruction of joint structural components including bone and cartilage in the inflamed joints. In addition, decreased range of joint motion and mechanical hyperalgesia after disease onset were suppressed by JTE-952. These results suggest that JTE-952 is expected to prevent the progression of the structural destruction of joints and its associated effects on joint motion and pain by inhibiting CSF1/CSF1R signaling in RA pathology, which is resistant to conventional disease-modifying anti-rheumatic drugs such as MTX.

Colony stimulating factor 1 (CSF1) receptor (CSF1R) is a receptor protein-tyrosine kinase specifically expressed in monocyte-lineage cells, such as monocytes and macrophages. In this study, we characterized the pharmacological properties of an azetidine compound, JTE-952 ((2S)-3-{[2-({3-[4-(4-cyclopropylbenzyloxy)-3-methoxyphenyl]azetidine-1-yl}carbonyl)pyridin-4-yl]methoxy}propane-1,2-diol), which is a novel CSF1R tyrosine kinase inhibitor. JTE-952 potently inhibited human CSF1R kinase activity, with a half maximal inhibitory concentration of 11.1 nmol/L, and inhibited the phosphorylation of CSF1R in human macrophages and the CSF1-induced proliferation of human macrophages. It also inhibited human tropomyosin-related kinase A activity, but only at concentrations 200-fold higher than that required to inhibit the activity of CSF1R in inducing the proliferation of human macrophages. JTE-952 displayed no marked inhibitory activity against other kinases. JTE-952 potently inhibited lipopolysaccharide-induced proinflammatory cytokine production by human macrophages and in whole blood. JTE-952 (≥3 mg/kg given orally) also significantly attenuated the CSF1-induced priming of lipopolysaccharide-induced tumor necrosis factor-alpha production in mice and arthritis severity in a mouse model of collagen-induced arthritis. Taken together, these results indicate that JTE-952 is an orally available compound with potent and specific inhibitory activity against CSF1R, both in vitro and in vivo. JTE-952 is a potentially clinically useful agent for various human inflammatory diseases, including rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by synovial inflammation and structural destruction of the joints. Bone damage occurs in an early stage after onset and osteoclast activation plays a substantial role in its progression. Colony stimulating factor 1 receptor (CSF1R) is a receptor protein tyrosine kinase specifically expressed in monocytic-lineage cells such as macrophages and osteoclasts. Here, we investigated the effect of JTE-952, a novel CSF1R tyrosine kinase inhibitor, on osteoclast formation in vitro and on bone destruction in a mouse model of collagen-induced arthritis. JTE-952 completely inhibited osteoclast differentiation from human monocytes, with an IC 50 of 2.8 nmol/L, and reduced osteoclast formation from the synovial cells of RA patients. Detectable levels of colony stimulating factor 1 (CSF1), a ligand of CSF1R, were observed in the synovial tissues of the arthritis model, similar to those observed in the pathology of human RA. JTE-952 significantly suppressed increases in the bone destruction score, the number of tartrate-resistant-acid-phosphatase-positive cells, and the severity of arthritis in the model mice. We also examined the efficacy of JTE-952 combined with methotrexate. This combination therapy more effectively reduced the severity of bone destruction and arthritis than monotherapy with either agent alone. In summary, JTE-952 potently inhibited human osteoclast formation in vitro and suppressed bone destruction in an experimental arthritis model, especially when combined with methotrexate. These results indicate that JTE-952 should strongly inhibit bone destruction and joint inflammation in RA patients and effectively prevent the progression of the structural destruction of joints.

The pharmacological and pathophysiological characteristics of rat antigen-induced late airway response (LAR) are not yet fully understood. In this study, the pharmacological properties of rat ovalbumin (OVA)-induced LAR and effects of the clinically used anti-asthmatic drugs salbutamol (beta2-agonist), ketotifen (antihistamine), pranlukast (anti-leukotriene C4/D4/E4), and prednisolone (steroid) were examined. In addition, a comparison was made of cell infiltration in bronchoalveolar lavage fluid (BALF) between immediate airway response (IAR) and LAR, and the edematous features of lung during LAR were also examined. Although infiltration of inflammatory cells into BALF was increased in both IAR and LAR, only the increase in eosinophils at 1, 3, and 6 h during LAR were significantly higher than those during IAR. Although beta2-agonist, antihistamine, and anti-leukotriene C4/D4/E4 exhibited no effects on rat LAR, steroid attenuated LAR and decreased eosinophil number in BALF. LAR and the percentage water content were both increased after antigen inhalation, suggesting that LAR is involved in pulmonary edema in rats. In conclusion, antigen-induced LAR was related to pulmonary edema and eosinophil infiltration rather than contraction of airway smooth muscle. This is the first comprehensive study of the profiles of rat antigen-induced LAR, and these analyses of LAR improve understanding of the diverse mechanisms underlying human asthmatic diseases.

The pharmacological profiles of antigen-induced immediate airway response (IAR) in rats are not fully understood. In this study, we established an ovalbumin (OVA)-induced IAR model using noninvasive measurement in rats, and evaluated the effects of commonly used and effective antiasthmatic drugs, i.e. ketotifen (antihistamine), pranlukast (anti-leukotriene C(4)/D(4)/E(4) (LT)), seratrodast (anti-thromboxane A(2) (TXA(2))), salbutamol (beta2-agonist), and prednisolone (steroid). The rat IAR model exhibited an optimal rapid airway response, and salbutamol inhalation completely suppressed the IAR. Ketotifen inhibited only the quick phase (QP; the reaction from 3 to 6 min after challenge), while pranlukast and seratrodast suppressed only the early phase (EP; the reaction from 6 to 30 min after challenge). Prednisolone inhibited both QP and EP. Further, continuous administration of compound 48/80, which depletes connective tissue mast cells (CTMC), partially inhibited QP but not EP. In conclusion, these findings suggest that the pharmacological profiles of noninvasive rat IAR are similar to those of asthmatic patients, and that rat IAR exhibits additional, immunological diverse characteristics, i.e. QP caused by the exocytosis of mediators in CTMCs and EP mediated by LT and TXA(2), which are produced by mucosal mast cells (MMCs) and possibly by other types of cells. This is the first report about the comprehensive pharmacological profiles of rodent IAR model, and these analyses of rat IAR model may help expand our understanding of the diverse mechanisms underlying human asthmatic diseases.

The effects of a newly synthesized compound, 6-acetoamido-1-acetyl-1-indazole (TAS-3-124), on autoimmune diseases were studied. We used animal models of collagen-induced arthritis (CIA) in mice and experimental autoimmune encephalomyelitis (EAE) in rats to evaluate the efficacy of TAS-3-124. TAS-3-124 at doses of 100 and 300 mg/kg p.o. inhibited the development of CIA, decreasing the swelling of fore- and hind-limbs and bone destruction in knee joints. This agent also suppressed the delayed type hypersensitivity reaction (DTH) against type II collagen. These effects were confirmed by histopathological examination and measurement of the expression of mRNA of proinflammatory cytokines in the knee joint. In addition, TAS-3-124 at a dose of 300 mg/kg inhibited the development of EAE and the DTH to myelin basic protein (MBP) in rats. Moreover, TAS-3-124 inhibited the production of proinflammatory cytokines including interleukin (IL)-1beta, tumor necrosis factor (TNF)-alpha and IL-6 but not T cell derived cytokines in mice. These demonstrate the efficacy of TAS-3-124 against experimental autoimmune disease, probably due to the suppression of the production of proinflammatory cytokines in the pathological lesion.