Migalastat hydrochloride, also known as 1-deoxygalactonojirimycin hydrochloride, is a small molecule pharmacological chaperone. It is a synthetic iminosugar analog of galactose, structurally mimicking the terminal galactose residues of glycosphingolipids. Its primary and well-defined application is as an active pharmaceutical ingredient (API) for the treatment of Fabry disease, a rare genetic lysosomal storage disorder caused by deficient activity of the enzyme α-galactosidase A. Migalastat acts as a pharmacological chaperone by selectively and reversibly binding to the active site of specific mutant forms of α-galactosidase A. This binding stabilizes the enzyme's correct folding, facilitating its proper trafficking from the endoplasmic reticulum to the lysosomes, where it can perform its catalytic function in degrading globotriaosylceramide (GL-3). Migalastat HCl is administered orally and is marketed under the brand name Galafold. It represents a targeted, substrate reduction therapy for amenable mutations, offering an alternative to enzyme replacement therapy for eligible Fabry disease patients.