This document describes a new potential treatment for Late Infantile Batten Disease (LINCL) using enzyme replacement therapy. The researchers developed a method to deliver the missing enzyme, tripeptidyl peptidase 1 (TPP1), from the bloodstream into the brain by combining it with a special peptide. When tested in a mouse model of LINCL, a single intravenous treatment with TPP1 and the peptide significantly increased TPP1 activity in the brain and extended the lifespan of the mice, providing support for further study of this delivery method as a possible non-invasive therapy for LINCL.