Brain-targeted enzyme-loaded nanoparticles: A breach through the blood-brain barrier for enzyme replacement therapy in Krabbe disease

Lysosomal storage disorders (LSDs) result from an enzyme deficiency within lysosomes. The systemic administration of the missing enzyme, however, is not effective in the case of LSDs with central nervous system (CNS)-involvement. Here, an enzyme delivery system based on the encapsulation of cross-linked enzyme aggregates (CLEAs) into poly-(lactide-co-glycolide) (PLGA) nanoparticles (NPs) functionalized with brain targeting peptides (Ang2, g7 or Tf2) is demonstrated for Krabbe disease, a neurodegenerative LSD caused by galactosylceramidase (GALC) deficiency. We first synthesize and characterize Ang2-, g7- and Tf2-targeted GALC CLEA NPs. We study NP cell trafficking and capability to reinstate enzymatic activity in vitro. Then, we successfully test our formulations in the Twitcher mouse. We report enzymatic activity measurements in the nervous system and in accumulation districts upon intraperitoneal injections, demonstrating activity recovery in the brain up to the unaffected mice level. Together, these results open new therapeutic perspectives for all LSDs with major CNS-involvement.

Bone marrow transplantation increases efficacy of central nervous system-directed enzyme replacement therapy in the murine model of globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD, Krabbe disease), is an autosomal recessive, neurodegenerative disease caused by the deficiency of the lysosomal enzyme galactocerebrosidase (GALC). In the absence of GALC, the toxic metabolite psychosine accumulates in the brain and causes the death of the myelin-producing cells, oligodendrocytes. Currently, the only therapy for GLD is hematopoietic stem cell transplantation using bone marrow (BMT) or umbilical cord blood. However, this is only partially effective. Previous studies have shown that enzyme replacement therapy (ERT) provides some therapeutic benefit in the murine model of GLD, the Twitcher mouse. Experiments have also shown that two disparate therapies can produce synergistic effects when combined. The current study tests the hypothesis that BMT will increase the therapeutic effects of ERT when these two treatments are combined. Twitcher mice were treated with either ERT alone or both ERT and BMT during the first 2-4 days of life. Recombinant enzyme was delivered by intracerebroventricular (ICV) and intrathecal (IT) injections. Twitcher mice receiving ERT had supraphysiological levels of GALC activity in the brain 24h after injection. At 36 days of age, ERT-treated Twitcher mice had reduced psychosine levels, reduced neuroinflammation, improved motor function, and increased lifespan. Twitcher mice receiving both ERT and BMT had significantly increased lifespan, improved motor function, reduced psychosine levels, and reduced neuroinflammation in certain areas of the brain compared to untreated or ERT-treated Twitcher mice. Together, these results indicate that BMT enhances the efficacy of ERT in GLD.

Single‐dose intracerebroventricular administration of galactocerebrosidase improves survival in a mouse model of globoid cell leukodystrophy

Globoid cell leukodystrophy (GLD), also known as Krabbe disease, is a devastating, degenerative neurological disorder. It is inherited as an autosomal recessive trait caused by loss-of-function mutations in the galactocerebrosidase (GALC) gene. Previously, we have shown that peripheral injection of recombinant GALC, administered every other day, results in a substantial improvement in early clinical phenotype in the twitcher mouse model of GLD. While we did detect active enzyme in the brain following peripheral administration, most of the administered enzyme was localized to the periphery. Given the substantial central nervous system (CNS) involvement in this disease, we were interested in determining whether or not a single-dose administration of the recombinant enzyme directly to the CNS, which could potentially be achieved clinically, would result in any substantial improvement. Following intracerebroventricular (i.c.v.) administration of GALC we noted a significant, 16.5%, reduction in the GALC substrate psychosine, the abnormal accumulation of which is believed to play a pivotal role in the CNS pathology observed in this disease. Moreover, recombinant GALC was found not only in periventricular regions but also at sites distant to the injection such as the cerebral cortex and cerebellum. Most importantly, animals receiving a single i.c.v. dose of the enzyme at postnatal day 20 survived up to 51 days, which compares favorably to the control twitcher animals, which normally only live to postnatal day 40/42. These results indicate that even a single i.c.v. administration of the recombinant enzyme can have significant clinical impact and suggests that other lysosomal storage disorders with significant CNS involvement may similarly benefit.