Afegostat, aslo known as Isofagomine, and AT2101, was an experimental drug for the treatment of certain forms of Gaucher's disease. Isofagomine (IFG) is an acid β-glucosidase (GCase) active site inhibitor that acts as a pharmacological chaperone. FG inhibits GCase with K(i) ~30 nM for wild-type and mutant enzymes (N370S and V394L). Administration of IFG (30 mg/kg/day) to the mice homozygous for GCase mutations (V394L, D409H, or D409V) led to increased GCase activity in visceral tissues and brain extracts.