Glucocorticoid resistance inhibitor is an inhibitor of glucocorticoid resistance. It inhibits cell growth of the T cell acute lymphoblastic leukemia (T-ALL) cell line CUTTL1 when used in combination with dexamethasone (EC50 = 28 µM) and is less effective when used alone (EC50 = 294 µM). Glucocorticoid resistance inhibitor (6.25-50 µM) preferentially inhibits growth of CUTTL1 cells expressing high levels of the glucocorticoid receptor over cells expressing low levels. It upregulates the gene expression and protein levels of the glucocorticoid receptor and induces expression of dexamethasone-regulated genes when used in combination with dexamethasone but not when used alone.