PGA-Protein conjugation of Velaglucerase as novel methodology for increasing the efficiency and efficacy of Gaucher Disease treatment by ERT

Abstract

Enzyme Replacement Therapy (ERT) has revolutionised patient management in Lysosome Storage Disorders (LSD). Gaucher Disease (GD), a disorder caused by mutations in the GBA gene, which encodes for the enzyme Glucocerebrosidase, is the most prevalent LSD. Administration of functional Glucocerebrosidase to GD patients results in a notorious reversion of the visceral manifestations of the disease. Nonetheless, there are important shortcomings in ERT as the inability to cross the Blood-Brain Barrier (BBB), making it ineffective to treat the neurologic manifestations that GD may involve, and poor stability and enzyme activity loss during transportation throughout the bloodstream. Protein encapsulation has been widely studied in order to overcome the challenges of protein therapeutics in terms of effective and efficient delivery in the site of action. Encapsulation can protect proteins from degradation or inactivation, can carry out a specific delivery and ensure a controlled and sustained release in target. However, the encapsulation process usually has harmful effect in protein stability and/or activity. Herein we suggest a method for protein modification and coating in Velaglucerase, a recombinant version of Glucocerebrosidase used in GD treatment, in order to overcome the main challenges of ERT. Polymer Masked-Unmasked Protein Therapy (PUMPT) is based on protein conjugation with a biodegradable poly-L-glutamic acid (PGA) polymer that mask protein activity during transportation along the bloodstream, protecting it from harsh environmental conditions. Conjugates stay coated in non-reductive environments such as the bloodstream and are released into highly reductive ones, such as the lysosomes. The results indicate that Velaglucerase-PGA conjugates successfully reach the lysosome and are able to partially restore Glucocerebrosidase activity in GBA knockout cells, in a similar manner to unconjugated Velaglucerase. Nonetheless, conjugates are much more stable in blood plasma than the unconjugated protein, which rapidly loses its activity. This successful protein conjugation method allow the introduction of surface modifications without modifying the protein itself and thus interfering in its activity, keeping a door opened to specific targeting and BBB crossing.