Krabbe disease (globoid cell leukodystrophy) is a rare inherited disorder caused by a deficiency in thelysosomal enzyme galactosylceramidase (GALC) leading to destruction of the protective coating (myelin) ofnerve cells in the brain and throughout the nervous system. This fatal neurodegenerative disease affectsabout 1 in 100,000 people in the US. In most cases, Krabbe symptoms develop in infants before 6 months ofage, often leading to death by age 2. Bone marrow transplantation is currently the only approved treatmentoption for Krabbe patients, but only slows disease progression, and only when initiated in pre-symptomaticchildren. More recent preclinical research has focused on gene transfer utilizing adeno-associated virus (AAV)for long term expression of the normal GALC enzyme in the "twitcher" mouse model of Krabbe disease.Although promising, this approach still shows deficiencies in distributing effective therapeutic doses to criticalparts of the brain and nervous system. BioStrategies LC has developed a lectin-based therapeutic deliverymodule (RTB) that enables fused lysosomal enzymes to effectively target the CNS and treat neurologicalsymptoms following weekly ERT infusions, as demonstrated in several lysosomal disease animal models. In this SBIR project, we propose to merge the benefits of AAV-mediated gene transfer technologies thatprovide continuous long-term in vivo enzyme production with those of the RTB delivery technology to ensureeffective treatment of Krabbe's progressive neurodegeneration. Gene expression cassettes fusing GALC withBioStrategies' RTB lectin will be packaged into recombinant adeno-associated virus for production andsubsequent administration to twitcher mice. Impacts on neurological disease progression and lifespan of micereceiving AAV-vectored GALC-RTB fusions will be compared with untreated mice and those administeredAAV-vectored GALC alone. Specific aims of this Phase I feasibility study are 1) to construct GALC-RTB AAVvectors and demonstrate their ability to produce fully functional GALC-RTB fusion product in mammalian cellsand mice; and 2) to compare therapeutic efficacy of AAV-mediated gene transfer of GALC-RTB versus GALCin the Krabbe mouse model as measured by lifespan and imaging of brain and peripheral nerve pathologies. Phase I milestones will show that our lectin fusion, GALC-RTB, can be expressed in the Krabbe twitchermodel via AAV gene transfer and demonstrate targeting of expressed GALC-RTB to hard-to-treat cells of CNSand PNS tissue in twitcher (GALC-/-) mice, enhancing enzyme biodistribution and lifespan. Based on theseproof-of concept results, Phase II studies will assess the effects of dosage levels, timing, and routes of drugadministration on efficacy and safety of long-term treatment aimed at further moving this product to an IND.The long-term goal of this project is to develop and bring this novel "delivery-enhanced" AAV gene therapy toKrabbe patients. The feasibility established here will also support expanding the "RTB lectin-fused" genetherapy treatment to other rare diseases having significant CNS and PNS tissue impairment.
Public Health Relevance Statement: NARRATIVE -
Public Health Relevance:
The family of human metabolic/genetic diseases represented by Krabbe Disease and other rare
lysosomal disorders include some of the most devastating human afflictions known and the most
costly to patients, their families, and the public health system. Although ERT drugs have been
revolutionary in delivering treatments for several of these diseases, they have been prone to
significant drawbacks including their inability to treat symptoms in certain "hard-to-treat" organs
like the brain and skeletal systems and development of immune sensitivity in some patients after
longer periods of treatment. Krabbe, which has significant CNS involvement has been particularly
refractory for development of traditional enzyme replacement therapeutic options. A more recent
approach using new AAV-bases gene transfer technologies to express deficient Krabbe enzyme
has also shown problems in regard to biodistribution though-out the Central and Peripheral
Nervous systems. This project addresses the need for delivering therapeutic enzyme to the
CNS/PNS of affected patients by integrating AAV gene transfer technology with BioStrategies'
lectin-based enzyme delivery technology which has been shown to provide wide and effective
enzyme biodistribution within the brain of other lysosomal disease models. The innovative
integration of two highly promising drug delivery technologies developed in this project would
further the US national goal of reducing the human suffering and costs associated with these
diseases.
Project Terms: <0-11 years old><α-L-Idosiduronase><α-L-Iduronidase><α-L-iduronidase (IDA, IDUA) deficiency> | | 