Recent studies provided evidence for a significant role of cathepsin S during extracellular remodeling in atherosclerosis. In this study, we investigated the effect of a specific cathepsin S ...inhibitor on atherosclerotic plaque progression in the brachiocephalic artery. Male and female Apoe-/- mice on a cholate-containing high-fat diet containing or lacking a specific cathepsin S inhibitor were evaluated for the remodeling of atherosclerotic lesions. The in vivo efficacy of the cathepsin S inhibitor was demonstrated by the inhibition of invariant chain processing in spleen. After 8 weeks of diet, brachiocephalic arteries were analyzed for plaque size, collagen, macrophage, and smooth muscle cell content, for elastic lamina breaks, and the number of buried fibrous caps. The size of atherosclerotic plaques in inhibitor-treated mice was reduced by 36% in male and 68% in female mice, and they showed significantly smaller numbers in elastin lamina breaks (60% less in males; 75% less in females), plaque macrophages (47% less in males; 40% less in females), and buried fibrous caps (50% less in males; 86% less in females). In conclusion, the inhibition of cathepsin S showed a strong atheroprotective activity, demonstrating the potential benefits of a small molecule anti-cathepsin therapy.
The recent discovery of an alternative form cyclooxygenase (cyclooxygenase-2, COX-2), which has been proposed to play a significant role in inflammatory conditions, may provide an opportunity to ...develop anti-inflammatory drugs with fewer side effects than existing non-steroidal anti-inflammatory drugs (NSAIDs). We have now identified 6-(2,4-difluorophenyl)-thio-5-methanesulfonamido-1-indanone++ + (20) (L-745,337) as a potent, selective, and orally active COX-2 inhibitor. The structure-activity relationships in this series have been extensively studied. Ortho- and para-substituted 6-phenyl substitutents are optimal for in vitro potency. Replacement of this phenyl ring by a variety of heterocycles gave compounds that were less active. The methanesulfonamido group seems to be the optimal group at the 5-position of the indanone system. Compound 20 has an efficacy profile that is superior or comparable to that of the nonselective COX inhibitor indomethacin in animal models of inflammation, pain, and fever and appears to be nonulcerogenic within the dosage ranges required for functional efficacy. Although 20 and its oxygen linkage analog 2 (flosulide) are equipotent in the in vitro assays, compound 20 is more potent in the rat paw edema assay, has a longer t1/2 in squirrel monkeys, and seems less ulcergenic than 2 in rats.
A weak, UDP-competitive antagonist of the pyrimidinergic receptor P2RY₁₄ with a naphthoic acid core was identified through high-throughput screening. Optimization provided compounds with improved ...potency but poor pharmacokinetics. Acylglucuronidation was determined to be the major route of metabolism. Increasing the electron-withdrawing nature of the substituents markedly reduced glucuronidation and improved the pharmacokinetic profile. Additional optimization led to the identification of compound 38 which is an 8nM UDP-competitive antagonist of P2Y₁₄ with a good pharmacokinetic profile.
Our series of competitive antagonists against the G-protein coupled receptor P2Y₁₄ were found to be highly shifted in the presence of serum (>99% protein bound). A binding assay using 2% human serum ...albumin (HSA) was developed to guide further SAR studies and led to the identification of the zwitterion 2, which is substantially less shifted (18-fold) than our previous lead compound 1 (323-fold). However, as the bioavailability of 2 was low, a library of ester pro-drugs was prepared (7a–7j) and assessed in vitro. The most interesting candidates were then profiled in vivo and led to the identification of the pro-drug 7j, which possesses a substantially improved pharmacokinetic profile.
Cathepsin S (Cat S) is predominantly expressed in antigen-presenting cells and is up-regulated in several preclinical models of antigen-induced inflammation, suggesting a role in the allergic ...response. Prophylactic dosing of an irreversible Cat S inhibitor has been shown to attenuate pulmonary eosinophilia in mice, supporting the hypothesis that Cat S inhibition before the initiation of airway inflammation is beneficial in airway disease. In addition, Cat S has been shown to play a role in more distal events in the allergic response. To determine where Cat S inhibition may affect the allergic response, we used complementary genetic and pharmacological approaches to investigate the role of Cat S in the early and downstream allergic events in a murine model of antigen-induced lung inflammation. Cat S knockout mice did not develop ovalbumin-induced pulmonary inflammation, consistent with a role for Cat S in the development of the allergic response. Alternatively, wild-type mice were treated with a reversible, highly selective Cat S inhibitor in prophylactic and therapeutic dosing paradigms and assessed for changes in airway inflammation. Although both treatment paradigms resulted in potent Cat S inhibition, only prophylactic Cat S inhibitor dosing blocked lung inflammation, consistent with our findings in Cat S knockout mice. The findings indicate that although Cat S is up-regulated in allergic models, it does not appear to play a significant role in the downstream effector inflammatory phase in this model; however, our results demonstrate that Cat S inhibition in a prophylactic paradigm would ameliorate airway inflammation.
Using the cell-permeable, radioiodinated, irreversible inhibitor BIL-DMK, we probed active cysteine cathepsins in blood. Incubation of the probe in human whole blood followed by separation of white ...blood cells by dextran sedimentation led to the labeling of one major band at 24
kDa. Two-dimensional gel electrophoresis showed that the band resolved in a single protein spot and corresponded to cathepsin S based on its molecular mass, isoelectric point, and Western blot analysis using anti-human cathepsin S antibodies. Cathepsin S activity in human whole blood was dependent on the time of blood collection, suggesting that cathepsin S activity is subject to circadian variations. Separation of white blood cell populations using a magnetic cell sorter and further characterization by FACS (fluorescent-activated cell sorting) analysis demonstrated that the majority of active cathepsin S resided in the monocyte and neutrophil populations, whereas on a cell basis cathepsin S activity in granulocytes is 10-fold lower than that in monocytes. A whole blood cathepsin S assay was developed and used to measure cathepsin S inhibition in both in vitro and ex vivo conditions. To determine the correlation between the in vitro and ex vivo assays, a reversible cathepsin S inhibitor was dosed intravenously to a rhesus monkey. The inhibitor concentration required to inhibit 50% of the cathepsin S activity ex vivo correlated well with the concentration required to inhibit the enzyme in rhesus monkey whole blood in vitro. The results reported here demonstrate the utility of the activity-based probe BIL-DMK for the ex vivo assessment of cathepsin S inhibition.
The Merck Frosst Centre for Therapeutic Research, 16711 Trans Canada Highway, Kirkland, Qué., Canada H9H 3L1.
Highly potent, selective, and bioavailable inhibitors of human, mouse, or rat cathepsin S ...are described. The key structural features combine a sulfonyl moiety attached to a large group in P2 and a small substituent in P3.
Based on our previous study with trifluoroethylamine as a P2–P3 amide isostere of cathepsin K inhibitor, further optimization led to identification of compound
22 (L-873724) as a potent and selective ...non-basic cathepsin K inhibitor.
Based on our previous study with trifluoroethylamine as a P2–P3 amide isostere of cathepsin K inhibitor, further optimization led to identification of compound
22 (L-873724) as a potent and selective non-basic cathepsin K inhibitor. This compound showed excellent pharmacokinetics and efficacy in an ovariectomized (OVX) rhesus monkey model. The volumes of distribution close to unity were consistent with this compound not being lysosomotropic, which is a characteristic of basic cathepsin K inhibitors.
Protein tyrosine phosphatase 1B (PTP1B) has been implicated in the regulation of the insulin signaling pathway and represents an attractive target for the design of inhibitors in the treatment of ...type 2 diabetes and obesity. Inspection of the structure of PTP1B indicates that potent PTP1B inhibitors may be obtained by targeting a secondary aryl phosphate-binding site as well as the catalytic site. We report here the crystal structures of PTP1B in complex with first and second generation aryldifluoromethyl-phosphonic acid inhibitors. While all compounds bind in a previously unexploited binding pocket near the primary binding site, the second generation compounds also reach into the secondary binding site, and exhibit moderate selectivity for PTP1B over the closely related T-cell phosphatase. The molecular basis for the selectivity has been confirmed by single point mutation at position 52, where the two phosphatases differ by a phenylalanine-to-tyrosine switch. These compounds present a novel platform for the development of potent and selective PTP1B inhibitors.
A series of 3-heteroaryloxy-4-phenyl-2-(5H)-furanones were prepared and evaluated for their potency and selectivity as COX-2 inhibitors. This led to the identification of L-778,736 as a potent, ...orally active and selective inhibitor of the COX-2 enzyme.
A series of 3-heteroaryloxy-4-phenyl-2-(5H)-furanones were prepared and evaluated for their potency and selectivity as COX-2 inhibitors. This led to the identification of L-778,763 as a potent, orally active and selective inhibitor of the COX-2 enzyme.
