Sonia Lamontagne

The utilization of recombinant prostanoid receptors to determine the affinities and selectivities of prostaglandins and related analogs

Stable cell lines that individually express the eight known human prostanoid receptors (EP(1), EP(2), EP(3), EP(4), DP, FP, IP and TP) have been established using human embryonic kidney (HEK) 293(EBNA) cells. These recombinant cell lines have been employed in radioligand binding assays to determine the equilibrium inhibitor constants of known prostanoid receptor ligands at these eight receptors. This has allowed, for the first time, an assessment of the affinity and selectivity of several novel compounds at the individual human prostanoid receptors. This information should facilitate interpretation of pharmacological studies that employ these ligands as tools to study human tissues and cell lines and should, therefore, result in a greater understanding of prostanoid receptor biology.

The discovery of odanacatib (MK-0822), a selective inhibitor of cathepsin K.

Odanacatib is a potent, selective, and neutral cathepsin K inhibitor which was developed to address the metabolic liabilities of the Cat K inhibitor L-873724. Substituting P1 and modifying the P2 side chain led to a metabolically robust inhibitor with a long half-life in preclinical species. Odanacatib was more selective in whole cell assays than the published Cat K inhibitors balicatib and relacatib. Evaluation in dermal fibroblast culture showed minimal intracellular collagen accumulation relative to less selective Cat K inhibitors.

Structure-activity relationship of cinnamic acylsulfonamide analogues on the human EP3 prostanoid receptor

Potent and selective antagonists of the human EP3 receptor have been identified. The structure-activity relationship of the chemical series was conducted and we found several analogues displaying sub-nanomolar K(i) values at the EP3 receptor and micromolar activities at the EP1, EP2 and EP4 receptors. The effect of added human serum albumin (HSA) on the binding affinity at the EP3 receptor was also investigated.

Expression of prostaglandin D synthase and the prostaglandin D2 receptors DP and CRTH2 in human nasal mucosa

Abstract Background : Prostaglandin D 2 (PGD 2 ) is released from mast cells during the allergic response. Objective : Since PGD 2 has been shown to induce nasal congestion in humans, we investigated the distribution of hematopoietic prostaglandin D synthase (PGDS) and the two PGD 2 receptors, DP and CRTH2 in human nasal mucosa from healthy subjects and subjects suffering from polyposis, a severe form of chronic rhinosinusitis. Methods : DP mRNA expression was detected by in situ hybridization while PGDS, CRTH2 and various leukocyte markers expression were revealed by immunohistochemistry. Results : In the normal mucosa, PGDS was only detected in few resident mast cells while CRTH2 was undetectable. In contrast, DP receptor mRNA was detected in epithelial goblet cells, serous glands and in the vasculature. In the nasal mucosa of subjects suffering from polyposis: (1) PGDS was detected in mast cells and other large infiltrating inflammatory cells, (2) both DP mRNA and CRTH2 were detected in eosinophils and (3) CRTH2 was detected on a subset of infiltrating T cells. Although DP mRNA could not be detected in the T cells invading the nasal mucosa, it was found to be expressed in the T cells present in the lymph node and the thymus from normal individuals. Conclusion : This study indicates that cells capable of producing PGD 2 are present in the nasal mucosa and that both PGD 2 receptors, DP and CRTH2, might play a role in inflammatory disease of the upper airways.

Localization of phosphodiesterase-4 isoforms in the medulla and nodose ganglion of the squirrel monkey

Pre-clinical and clinical studies are currently underway to evaluate the potential of phosphodiesterase-4 (PDE4) inhibitors for the treatment of chronic obstructive pulmonary disease and other inflammatory conditions of the airways. The most common side effect associated with this class of compounds is emesis. The squirrel monkey provides a model for evaluating the efficacy of PDE4 inhibitors and their emetic potential. The distribution of three PDE4 isoforms (A, C and D) has been investigated in the squirrel monkey medulla and nodose ganglion to determine which isoform(s) could be responsible for the emetic adverse effects. The distribution of PDE4 isoforms was delineated using immunohistochemistry with antibodies specific for PDE4A, PDE4C and PDE4D and by in situ hybridization with isoform-selective riboprobes. PDE4A was present in the medulla where expression was mostly restricted to glial cells and the vasculature. PDE4C was not detected in either the medulla or nodose ganglion. Finally, the PDE4D isoform was localized to neurons in the nodose ganglion and found through many structures of medulla including the area postrema, neurons of the nucleus tractus solitarius and locus coeruleus. These data are consistent with a role for PDE4D in the emetic response.

Structure–Activity Relationship of Biaryl Acylsulfonamide Analogues on the Human EP3 Prostanoid Receptor

Potent and selective ligands for the human EP3 prostanoid receptor are described. Biaryl compounds bearing a tethered ortho substituted acidic moiety were identified as potent EP3 antagonists based on the SAR described herein. The binding affinity of key compounds on all eight human prostanoid receptors is reported.

New class of biphenylene dibenzazocinones as potent ligands for the human EP1 prostanoid receptor

A new class of potent and selective ligands for the human EP1 prostanoid receptor is described. SAR studies reported herein allowed the identification of several potent dibenzazocinones bearing an acylsulfonamide side chain. The binding affinity of these compounds on all eight human prostanoid receptors is reported.

Genetic and Pharmacological Evaluation of Cathepsin S in a Mouse Model of Asthma

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.

The discovery of MK-0674, an orally bioavailable cathepsin K inhibitor

MK-0674 is a potent and selective cathepsin K inhibitor from the same structural class as odanacatib with a comparable inhibitory potency profile against Cat K. It is orally bioavailable and exhibits long half-life in pre-clinical species. In vivo studies using deuterated MK-0674 show stereoselective epimerization of the alcohol stereocenter via an oxidation/reduction cycle. From in vitro incubations, two metabolites could be identified: the hydroxyleucine and the glucuronide conjugate which were confirmed using authentic synthetic standards.

Structure-activity relationship of triaryl propionic acid analogues on the human EP3 prostanoid receptor.

Potent and selective ligands for the human EP3 prostanoid receptor are described. Triaryl compounds bearing an ortho-substituted propionic acid moiety were identified as potent EP3 antagonists based on the SAR described herein. The binding affinities of key compound on all eight human prostanoid receptors is reported.