The pursuit of differentiated ligands for the glucocorticoid receptor

Glucocorticoids have a pervasive role in human health and physiology. The endogenous members of this family are involved in a breadth of endocrine functions including metabolism of lipids, carbohydrates and proteins, stress response, fluid and electrolyte balance, as well as maintenance of immunological, renal and skeletal homeostasis. The predominant mode of action of glucocorticoids involves regulation of gene expression via the glucocorticoid receptor (GR). Synthetic glucocorticoids have long been the standard for the treatment of inflammatory and immune disorders, yet the benefits of classic steroids such as dexamethasone and prednisolone are accompanied by well-characterized potentiation of homeostatic endocrine functions, leading to the side effects associated with prolonged treatment. In recent campaigns for safer analogs, compounds have been sought which differentiate functional repression of existing transcription factors such as AP-1 and NFkappaB from GR-mediated transcriptional activation arising from binding at glucocorticoid-receptor response elements (GREs). Such differentiated ligands would provide the desired immunoregulatory actions without the endogenous changes in gene expression associated with undifferentiated steroids. We detail the methods for the evaluation of selective GR modulators and describe the evolution of new compounds where varying degrees of selectivity have been reported.