Azaxanthene based selective glucocorticoid receptor modulators: design, synthesis, and pharmacological evaluation of (S)-4-(5-(1-((1,3,4-thiadiazol-2-yl)amino)-2-methyl-1-oxopropan-2-yl)-5H-chromeno[2,3-b]pyridin-2-yl)-2-fluoro-N,N-dimethylbenzamide (BMS-776532) and its methylene homologue (BMS-791826)

Structurally novel 5H-chromeno[2,3-b]pyridine (azaxanthene) selective Glucocorticoid Receptor (GR) modulators have been identified. A screening paradigm utilizing cellular assays of GR-mediated transrepression of proinflammatory transcription factors and transactivation of GR-dependent genes combined with three physiologically relevant assays of cytokine induction in human whole blood has allowed for the identification of high affinity, selective GR ligands that display a broad range of pharmacological profiles. Agonist efficacy in reporter assays can be tuned by halogenation of a pendent phenyl ring and correlates well with efficacy for cytokine inhibition in human whole blood. A hypothetical binding mode is proposed, invoking an expanded ligand binding pocket resembling that of arylpyrazole-bound GR structures. Two compounds of close structural similarity (35 and 37; BMS-776532 and BMS-791826, respectively) have been found to maintain distinct and consistent levels of partial agonist efficacy across several assays, displaying anti-inflammatory activity comparable to that of prednisolone 2 in suppressing cytokine production in whole blood and in rodent models of acute and chronic inflammation.