The present invention provides an effective and less invasive approach for direct delivery of therapeutic agents to the central nervous system (CNS). In some embodiments, the present invention provides methods including a step of administering intrathecally to a subject suffering from or susceptible to a lysosomal storage disease associated with reduced level or activity of a lysosomal enzyme, a composition comprising a replacement enzyme for the lysosomal enzyme.

The present invention is related to a method for purifying heparan-N-sulfatase from a heparan-N-sulfatase-containing solution including at least one impurity, the method comprising performing multi-mode chromatography (MMC) to obtain an eluate; and performing caprylate precipitation to obtain a supernatant.

The method according to the present invention is capable of very efficiently removing HCP (host cell proteins) and of greatly improving the purity and stability of purified heparan-N-sulfatase.