A 2.5-yeаr-оld presents with cоаrse fаcial features, cоrneal clouding, hepatosplenomegaly, joint stiffness, developmental regression, and recurrent otitis media. Urine glycosaminoglycans (GAGs) are markedly elevated. Enzyme assay confirms alpha-L-iduronidase deficiency (Hurler syndrome/MPS I severe form). What is the MOST appropriate disease-modifying treatment at this stage?