pharmacology of robenacoxib: a novel selective inhibitor of cyclooxygenase-2. J. vet. Pharmacol. Therap. 32,[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] This manuscript reports the results of preclinical studies in the rat with robenacoxib, a novel selective cyclooxygenase (COX)-2 inhibitor. Robenacoxib selectively inhibited COX-2 in vitro as evidenced from COX-1:COX-2 IC 50 ratios of 27:1 in purified enzyme preparations and >967:1 in isolated cell assays. Binding to COX-1 was rapid and readily reversible (dissociation t 1 ⁄ 2 << 1 min), whilst COX-2 binding was slowly reversible (t 1 ⁄ 2 = 25 min). In vivo, robenacoxib inhibited PGE 2 production (an index of COX-2 inhibition) in lipopolysaccharide (LPS)-stimulated air pouches (ID 50 0.3 mg ⁄ kg) and for at least 24 h in zymosan-induced inflammatory exudate (at 2 mg ⁄ kg). Robenacoxib was COX-1 sparing, as it inhibited serum TxB 2 synthesis ex vivo (an index of COX-1 inhibition) only at very high doses (100 mg ⁄ kg but not at 2-30 mg ⁄ kg). Robenacoxib inhibited carrageenan-induced paw oedema (ID 50 0.40-0.48 mg ⁄ kg), LPS-induced fever (ID 50 1.1 mg ⁄ kg) and Randall-Selitto pain (10 mg ⁄ kg). Robenacoxib was highly bound to plasma protein (99.9% at 50 ng ⁄ mL in vitro). After intravenous dosing, clearance was 2.4 mL ⁄ min ⁄ kg and volume of distribution at steady-state was 306 mL ⁄ kg. Robenacoxib was preferentially distributed into inflammatory exudate; the AUC for exudate was 2.9 times higher than for blood and the MRT in exudate (15.9 h) was three times longer than in blood (5.3 h). Robenacoxib produced significantly less gastric ulceration and intestinal permeability as compared with the reference nonsteroidal anti-inflammatory drug (NSAID), diclofenac, and did not inhibit PGE 2 or 6-keto PGF 1a concentrations in the stomach and ileum at 30 mg ⁄ kg. Robenacoxib also had no relevant effects on kidney function at 30 mg ⁄ kg. In summary, results of preclinical studies in rats studies suggest that robenacoxib has an attractive pharmacological profile for potential use in the intended target species, cats and dogs.(Paper

1 This manuscript presents the preclinical profile of lumiracoxib, a novel cyclooxygenase-2 (COX-2) selective inhibitor. 2 Lumiracoxib inhibited purified COX-1 and COX-2 with K i values of 3 and 0.06 mM, respectively. In cellular assays, lumiracoxib had an IC 50 of 0.14 mM in COX-2-expressing dermal fibroblasts, but caused no inhibition of COX-1 at concentrations up to 30 mM (HEK 293 cells transfected with human COX-1). 3 In a human whole blood assay, IC 50 values for lumiracoxib were 0.13 mM for COX-2 and 67 mM for COX-1 (COX-1/COX-2 selectivity ratio 515). 4 Lumiracoxib was rapidly absorbed following oral administration in rats with peak plasma levels being reached between 0.5 and 1 h. 5 Ex vivo, lumiracoxib inhibited COX-1-derived thromboxane B 2 (TxB 2 ) generation with an ID 50 of 33 mg kg À1, whereas COX-2-derived production of prostaglandin E 2 (PGE 2 ) in the lipopolysaccharidestimulated rat air pouch was inhibited with an ID 50 value of 0.24 mg kg À1 . 6 Efficacy of lumiracoxib in rat models of hyperalgesia, oedema, pyresis and arthritis was dosedependent and similar to diclofenac. However, consistent with its low COX-1 inhibitory activity, lumiracoxib at a dose of 100 mg kg À1 orally caused no ulcers and was significantly less ulcerogenic than diclofenac (Po0.05). 7 Lumiracoxib is a highly selective COX-2 inhibitor with anti-inflammatory, analgesic and antipyretic activities comparable with diclofenac, the reference NSAID, but with much improved gastrointestinal safety. British Journal of Pharmacology (2005) 144, 538-550. doi:10.1038/sj.bjp.0706078 Published online 17 January 2005 Keywords: Lumiracoxib; COX-2; cyclooxygenase-2 selective inhibitor; preclinical Abbreviations: AUC, area-under-curve of the concentration vs time curve; C max , maximum drug plasma concentration; CFA, complete Freund's adjuvant; 51 Cr-EDTA, chromium-51 labelled EDTA; COX, cyclooxygenase; D 30 , dose at which 30% inhibition was achieved; DMSO, dimethyl sulphoxide; F 0 , fraction of uninhibited enzyme at equilibrium; GI, gastrointestinal; HEK, human embryonic kidney; IL-1, interleukin-1; K i , inhibitor constant; k on , second-order rate constant representing speed at which an inhibitor binds to an enzyme; I, inhibitor concentration; LC/MS/MS, liquid chromatography/mass spectrometry/mass spectrometry; LPS, lipopolysaccharide; NSAID, nonsteroidal anti-inflammatory drug; O 2 , oxygen; PGE 2 , prostaglandin E 2 ; s, arachidonic acid concentration; t 1/2 , half-life; t opt , time to optimal velocity; TxB 2 , thromboxane B 2 ; V 0 , velocity in the absence of inhibitor; V obs , observed velocity in the presence of inhibitor; V opt , highest observed O 2 consumption velocity; V max , Michaelis-Menten constant for the maximal calculated velocity

Objective. To determine the effects of peptidyl fluoromethyl ketones on the in vitro activity of purified cathepsins B and L, on tissue cysteine proteinase activity, and on cartilage and bone destruction in experimental arthritis.Methods. The effects of the fluoroketones on cathepsins B and L in vitro and the effects of oral administration of fluoroketones on ex vivo cysteine proteinase activity in tissue homogenates were determined by measuring the inhibition of fluorogenic substrate cleavage. To determine the effects on arthritis, animals were injected with adjuvant or type I1 collagen, treated orally with the fluoroketones, and the severity of arthritis was assessed by clinical, histologic, and radiologic methods.Results. All of the fluoroketones tested were potent inhibitors of purified cathepsins B and L activity.Oral administration of the fluoroketones reduced tissue cysteine proteinase activity by up to 77%. In addition,

Joint inflammation initially induced by intraarticular injection of an aqueous suspension of peptidoglycan-polysaccharide (PG-PS) fragments isolated from Streptococcus pyogenes was reactivated by systemic injection of a normally subarthropathic dose of homologous or heterologous cell wall polymers, including muramyl dipeptide and lipopolysaccharide. Reactivation was not correlated with the severity of the initial inflammatory reaction. Results of studies utilizing lZ5I-labeled PG-PS fragments suggested that reactivation was associated with increased localization of PG-PS fragments in the joint following reinjection. These results indicate that the initial injury of the joint by S pyagenes PG-PS fragments increases the susceptibility of the joint to subsequent injury. Furthermore, once the inflammatory reaction is initiated, it can be perpetuated by a variety of ubiquitous cell wall polymers derived from normal flora as well as from pathogenic bacteria.Rats given either a systemic or an intraarticular (IA) injection of an aqueous suspension of peptidoglycan-polysaccharide (PG-PS) fragments isolated from the cell walls of Streptococcus pyogenes develop inflammatory reactions of the synovium and surrounding tissues (1,2). Although initially similar in

LPS and peptidoglycan or covalent peptidoglycan-polysaccharide (PG-PS)' complexes are the major toxic components of bacterial cell walls. Lipid A and PG possess many of the biologic activities that LPS and PG-PS, respectively, have in common, such as pyrogenicity, polyclonal activation of lymphoid cells, complement activation, mitogenicity, macrophage activation, and adjuvanticity (1-3). Both also induce arthritis after injection into laboratory animals. Systemic injection of rats with a sterile, aqueous suspension of PG-PS from the group A streptococcus (PG-APS) induces a chronic erosive relapsing arthritis that has many features of rheumatoid arthritis (4-6). Distinct PG-PS structures from a number of other bacteria, including human indigenous intestinal species, induce arthritis of varying chronicity (7-10) . LPS induces primarily an acute arthritis of relatively short duration after intraarticular (i.a.) injection (7, 11-15), but there have been few reports of its arthropathic activity after systemic administration (16, 17, 17a) .In spite of the shared biologic properties and ubiquitous distribution of LPS and PG-PS, the interaction of their phlogistic activities in an inflammatory process has received little attention. During investigations of mechanisms of recurrent arthritis induced by PG-APS, we noted that a systemic injection of 100 Ag of Salmonella typhimurium LPS induced a transient recurrence of arthritis in rat joints previously inflamed by exposure to PG-APS (7,18) . We now report that the systemic injection of a much lower dose of LPS will induce a recurrence of arthritis injoints inflamed 3 wk previously by the intraarticular injection of PG-APS and describe this reaction in detail . We show that LPS from many bacteria, including Yersinia enterocolitica and Neisseria gonorrhoeae, are active ; that lipid A

The anti-arthritic effects of this specific, receptor tyrosine kinase inhibitor compound appear to be mediated by anti-angiogenic actions. This study represents a new indication for PTK787/ZK222584, namely, rheumatoid arthritis and further supports the belief that angiogenesis inhibition is likely to be beneficial in the therapy of this condition.

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Objective. To apply quantitative analytical methods to the evaluation of radiographic images in experimental arthritis.Methods. Adjuvant was used to induce arthritis in rats. Arthritis progression was followed by conventional methods. In addition, digitized images of radiographs of the calcaneus were examined for changes in the mean and in the distribution pattern of gray values. Periosteal new bone formation was measured as an increase in image area of the calcaneus.Results. Significant changes in the gray value profile and increases in periosteal bone formation occurred in arthritic rats. More extensive changes occurred in Lewis rats than in Sprague-Dawley rats. Analysis of serial radiographs revealed an initial decrease in the density of juxtaarticular bone, followed by progressive increases in gray value variation due to concurrent bone loss and bone formation. Eventually, bone formation in arthritic rats resulted in increased gray values above those in nonarthritic rats.Conclusion. Image analysis represents a sensitive, quantitative method for detecting radiographic changes in experimental arthritis.The adjuvant-and collagen-induced models of chronic arthritis are widely used for studies of the underlying pathophysiology of joint disease and for the evaluation of potential new therapeutic agents. In both models, grossly apparent joint inflammation rapidly