Publication
Liposome-targeted recombinant human acid sphingomyelinase: Production, formulation, and in vitro evaluation
Publisher:
Elsevier BV
Date:
04-2019
DOI:
10.1016/J.EJPB.2019.02.019
Abstract: Niemann-Pick disease type B is a hereditary rare condition caused by deficiency of the acid sphingomyelinase (ASM) that is needed for lysosomal hydrolysis of sphingomyelin to ceramide and phosphocholine. This deficiency leads to a massive accumulation of sphingomyelin in cells throughout the body, predominantly in the liver, spleen and lungs. Currently, there is no effective treatment available. Olipudase alfa (recombinant human acid sphingomyelinase rhASM) is an investigational drug that has shown promising results. However, dose-dependent toxicity was observed in mice upon the intravenous administration of rhASM, potentially due to the systemic release of ceramide upon the extracellular degradation of sphingomyelin by rhASM. Using a nanocarrier to deliver the rhASM to cells could improve the therapeutic window by shielding the rhASM to prevent the off-target degradation of sphingomyelin. For this aim, we recombinantly expressed hASM in human cells and loaded it into different liposomal formulations at a drug-to-lipid ratio of 4% (w/w). Among four formulations, the liposomal rhASM formulation with the composition DPPC:DOPS:BMP:CHOL:DiD (59:20:10:10:1 mol%) was selected because of its superiority concerning the encapsulation efficiency of rhASM (21%) and cellular uptake by fibroblasts and macrophages. The selected liposomal rhASM formulation significantly reduced the accumulated lyso-sphingomyelin in NPD-B fibroblasts by 71%, part of this effect was stimulated by the used lipids, compared to 55% when using the free rhASM enzyme. More importantly, the undesired extracellular degradation of sphingomyelin was reduced when using the selected liposomal rhASM by 61% relative to the free rhASM. The presented in vitro data indicate that the liposomal rhASM is effective and may provide a safer intervention than free rhASM.