Discovery of potent, selective, and orally bioavailable alkynylphenoxyacetic acid CRTH2 (DP2) receptor antagonists for the treatment of allergic inflammatory diseases.

New phenoxyacetic acid antagonists of CRTH2 are described. Following the discovery of a hit compound by a focused screening, high protein binding was identified as its main weakness. Optimization aimed at reducing serum protein binding led to the identification of several compounds that showed not only excellent affinities for the receptor (41 compounds with K(i) < 10 nM) but also excellent potencies in a human whole blood assay (IC(50) < 100 nM; PGD2-induced eosinophil shape change). Additional optimization of the PK characteristics led to the identification of several compounds suitable for in vivo testing. Of these, 19k and 19s were tested in two different pharmacological models (acute FITC-mediated contact hypersensitivity and ovalbumin-induced eosinophilia models) and found to be active after oral dosing (10 and 30 mg/kg).

Discovery of a Novel Series of CRTH2 (DP2) Receptor Antagonists Devoid of Carboxylic Acids.

Antagonism of the CRTH2 receptor represents a very attractive target for a variety of allergic diseases. Most CRTH2 antagonists known to date possess a carboxylic acid moiety, which is essential for binding. However, potential acid metabolites O-acyl glucuronides might be linked to idiosynchratic toxicity in humans. In this communication, we describe a new series of compounds that lack the carboxylic acid moiety. Compounds with high affinity (K i < 10 nM) for the receptor have been identified. Subsequent optimization succeeded in reducing the high metabolic clearance of the first compounds in human and rat liver microsomes. At the same time, inhibition of the CYP isoforms was optimized, giving rise to stable compounds with an acceptable CYP inhibition profile (IC50 CYP2C9 and 2C19 > 1 µM). Taken together, these data show that compounds devoid of carboxylic acid groups could represent an interesting alternative to current CRTH2 antagonists in development.

Optimization of the Central Core of Indolinone-Acetic Acid-Based CRTH2 (DP2) Receptor Antagonists.

New spiroindolinone antagonists of CRTH2 are described. Following identification of insufficient stability in human plasma as an important liability of the lead compounds, replacement of the spirosuccinimide core with a spirohydantoin or spiropyrrolidinone structure has yielded a compound that is fully stable in human plasma and with good potency in a human whole blood assay (IC50 = 69 nM) but shows a much lower oral bioavailability (6-9% in rodents) than the earlier compounds. Successive optimization aimed at restoring an acceptable oral bioavailability has yielded compound (S)-17a, which exhibits both stability in human plasma and a good oral bioavailability in rat (37%) and mouse (39%). This compound is also active in a mouse model of ovalbumin-induced lung inflammation following oral dosing at 30 mg/kg.

Discovery of a novel series of CXCR3 antagonists.

The discovery of a novel series of CXCR3 antagonists is described. Starting from an HTS positive, iterative optimization gave potent compounds (IC(50) 15 nM in a chemotaxis assay). The strategy employed to improve the metabolic stability of these derivatives is described.

Discovery of a new class of potent, selective, and orally bioavailable CRTH2 (DP2) receptor antagonists for the treatment of allergic inflammatory diseases.

A novel chemical class of potent chemoattractant receptor-homologous expressed on Th2 lymphocytes (CRTH2 or DP2) antagonists is reported. An initial and moderately potent spiro-indolinone compound ( 5) was found during a high-throughput screening campaign. Structure-activity relationship (SAR) investigation around the carboxylic acid group revealed that changes in this part of the molecule could lead to a reversal of functional activity, yielding weakly potent agonists. SAR investigation of the succinimide functional group led to the discovery of several single-digit nanomolar antagonists. The potency of these compounds was confirmed in a human eosinophil chemotaxis assay. Moreover, compounds ( R)- 58 and ( R)- 71 were shown to possess pharmacokinetic properties suitable for development as an orally bioavailable drug.