Jessica H. Bagel

Identification of Niemann-Pick C1 disease biomarkers through sphingolipid profiling

Niemann-Pick type C (NPC)1 is a rare neurodegenerative disease for which treatment options are limited. A major barrier to development of effective treatments has been the lack of validated biomarkers to monitor disease progression or serve as outcome measures in clinical trials. Using targeted metabolomics to exploit the complex lipid storage phenotype that is the hallmark of NPC1 disease, we broadly surveyed Npc1−/− mouse tissues and identified elevated species across multiple sphingolipid classes that increased with disease progression. There was a striking accumulation of sphingoid bases, monohexosylceramides (MCs), and GM2 gangliosides in liver, and sphingoid bases and GM2 and GM3 gangliosides in brain. These lipids were modestly decreased following miglustat treatment, but markedly decreased in response to treatment with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), two drugs that have shown efficacy in NPC1 animal models. Extending these studies to human subjects led to identification of sphingolipid classes that were significantly altered in the plasma of NPC1 patients. Plasma MCs and ceramides were elevated, whereas sphingoid bases were reduced in NPC1 subjects. Intervention with miglustat in NPC1 patients was accompanied by striking alterations in plasma (reductions in GM1 and GM3 gangliosides) and cerebrospinal fluid (CSF) (increased MCs) sphingolipids. Similar alterations were observed in the CSF from the NPC1 feline model following HP-β-CD treatment. Our findings suggest that these lipid biomarkers may prove useful as outcome measures for monitoring efficacy of therapy in clinical trials.

Intrathecal Gene Therapy Corrects CNS Pathology in a Feline Model of Mucopolysaccharidosis I

Enzyme replacement therapy has revolutionized the treatment of the somatic manifestations of lysosomal storage diseases (LSD), although it has been ineffective in treating central nervous system (CNS) manifestations of these disorders. The development of neurotrophic vectors based on novel serotypes of adeno-associated viruses (AAV) such as AAV9 provides a potential platform for stable and efficient delivery of enzymes to the CNS. We evaluated the safety and efficacy of intrathecal delivery of AAV9 expressing α-l-iduronidase (IDUA) in a previously described feline model of mucopolysaccharidosis I (MPS I). A neurological phenotype has not been defined in these animals, so our analysis focused on the biochemical and histological CNS abnormalities characteristic of MPS I. Five MPS I cats were dosed with AAV9 vector at 4-7 months of age and followed for 6 months. Treated animals demonstrated virtually complete correction of biochemical and histological manifestations of the disease throughout the CNS. There was a range of antibody responses against IDUA in this cohort which reduced detectable enzyme without substantially reducing efficacy; there was no evidence of toxicity. This first demonstration of the efficacy of intrathecal gene therapy in a large animal model of a LSD should pave the way for translation into the clinic.

Neonatal Systemic AAV Induces Tolerance to CNS Gene Therapy in MPS i Dogs and Nonhuman Primates

The potential host immune response to a nonself protein poses a fundamental challenge for gene therapies targeting recessive diseases. We demonstrate in both dogs and nonhuman primates that liver-directed gene transfer using an adeno-associated virus (AAV) vector in neonates induces a persistent state of immunological tolerance to the transgene product, substantially improving the efficacy of subsequent vector administration targeting the central nervous system (CNS). We applied this approach to a canine model of mucopolysaccharidosis type I (MPS I), a progressive neuropathic lysosomal storage disease caused by deficient activity of the enzyme α-l-iduronidase (IDUA). MPS I dogs treated systemically in the first week of life with a vector expressing canine IDUA did not develop antibodies against the enzyme and exhibited robust expression in the CNS upon intrathecal AAV delivery at 1 month of age, resulting in complete correction of brain storage lesions. Newborn rhesus monkeys treated systemically with AAV vector expressing human IDUA developed tolerance to the transgene, resulting in high cerebrospinal fluid (CSF) IDUA expression and no antibody induction after subsequent CNS gene therapy. These findings suggest that inducing tolerance to the transgene product during a critical period in immunological development can improve the efficacy and safety of gene therapy.

Adeno-associated virus serotypes 9 and rh10 mediate strong neuronal transduction of the dog brain

Canine models have many advantages for evaluating therapy of human central nervous system (CNS) diseases. In contrast to nonhuman primate models, naturally occurring canine CNS diseases are common. In contrast to murine models, the dog’s lifespan is long, its brain is large and the diseases affecting it commonly have the same molecular, pathological and clinical phenotype as the human diseases. We compared the ability of four intracerebrally injected adeno-associated virus vector (AAV) serotypes to transduce the dog brain with green fluorescent protein as the first step in using these vectors to evaluate both delivery and efficacy in naturally occurring canine homologs of human diseases. Quantitative measures of transduction, maximum diameter and area, identified both AAV2/9 and AAV2/rh10 as significantly more efficient than either AAV2/1 or AAV2/5 at transducing cerebral cortex, caudate nucleus, thalamus and internal capsule. Fluorescence co-labeling with cell-type-specific antibodies demonstrated that AAV2/9 and AAV2/rh10 were capable of primarily transducing neurons, although glial transduction was also identified and found to be more efficient with the AAV2/9 vector. These data are a prerequisite to evaluating the efficacy of recombinant AAV vectors carrying disease-modifying transgenes to treat naturally occurring canine models in preclinical studies of human CNS disease therapy.

Evaluation of AAV-mediated Gene Therapy for Central Nervous System Disease in Canine Mucopolysaccharidosis VII

Mucopolysaccharidosis VII (MPS VII) is a lysosomal storage disease arising from mutations in β-d-glucuronidase (GUSB), which results in glycosaminoglycan (GAG) accumulation and a variety of clinical manifestations including neurological disease. Herein, MPS VII dogs were injected intravenously (i.v.) and/or intrathecally (i.t.) via the cisterna magna with AAV9 or AAVrh10 vectors carrying the canine GUSB cDNA. Although i.v. injection alone at 3 days of age resulted in normal cerebrospinal fluid (CSF) GUSB activity, brain tissue homogenates had only ~1 to 6% normal GUSB activity and continued to have elevated GAG storage. In contrast, i.t. injection at 3 weeks of age resulted in CSF GUSB activity 44-fold normal while brain tissue homogenates had >100% normal GUSB activity and reduced GAGs compared with untreated dogs. Markers for secondary storage and inflammation were eliminated in i.t.-treated dogs and reduced in i.v.-treated dogs compared with untreated dogs. Given that i.t.-treated dogs expressed higher levels of GUSB in the CNS tissues compared to those treated i.v., we conclude that i.t. injection of AAV9 or AAVrh10 vectors is more effective than i.v. injection alone in the large animal model of MPS VII.

Liver-directed gene therapy corrects cardiovascular lesions in feline mucopolysaccharidosis type I.

Significance Treatment of the lysosomal storage disease mucopolysaccharidosis type I (MPS I) is currently based on hematopoietic stem cell transplantation (HSCT) or weekly infusions of the deficient enzyme. To circumvent the morbidity and mortality associated with HSCT and the economic and quality of life costs of lifelong enzyme replacement therapy, we tested liver-directed gene therapy as a means of achieving endogenous enzyme expression in a feline model of MPS I. We found that hepatic gene transfer not only generated therapeutic levels of circulating enzyme, but in most cases also resulted in complete resolution of storage lesions in the cardiac valves, a tissue that is refractory to currently available therapies and responsible for much of the residual morbidity and mortality in treated patients. Patients with mucopolysaccharidosis type I (MPS I), a genetic deficiency of the lysosomal enzyme α-l-iduronidase (IDUA), exhibit accumulation of glycosaminoglycans in tissues, with resulting diverse clinical manifestations including neurological, ocular, skeletal, and cardiac disease. MPS I is currently treated with hematopoietic stem cell transplantation or weekly enzyme infusions, but these therapies have significant drawbacks for patient safety and quality of life and do not effectively address some of the most critical clinical sequelae, such as life-threatening cardiac valve involvement. Using the naturally occurring feline model of MPS I, we tested liver-directed gene therapy as a means of achieving long-term systemic IDUA reconstitution. We treated four MPS I cats at 3–5 mo of age with an adeno-associated virus serotype 8 vector expressing feline IDUA from a liver-specific promoter. We observed sustained serum enzyme activity for 6 mo at ∼30% of normal levels in one animal, and in excess of normal levels in three animals. Remarkably, treated animals not only demonstrated reductions in glycosaminoglycan storage in most tissues, but most also exhibited complete resolution of aortic valve lesions, an effect that has not been previously observed in this animal model or in MPS I patients treated with current therapies. These data point to clinically meaningful benefits of the robust enzyme expression achieved with hepatic gene transfer that extend beyond the economic and quality of life advantages over lifelong enzyme infusions.

Cholesterol homeostatic responses provide biomarkers for monitoring treatment for the neurodegenerative disease Niemann–Pick C1 (NPC1)

Niemann-Pick C1 (NPC1) disease is a rare, neurodegenerative lysosomal cholesterol storage disorder, typified by progressive cognitive and motor function impairment. Affected individuals usually succumb to the disease in adolescence. 2-Hydroxypropyl-β-cyclodextrin (HP-β-CD) has emerged as a promising intervention that reduces lipid storage and prolongs survival in NPC1 disease animal models. A barrier to the development of HP-β-CD and other treatments for NPC disease has been the lack of validated biochemical measures to evaluate efficacy. Here we explored whether cholesterol homeostatic responses resulting from HP-β-CD-mediated redistribution of sequestered lysosomal cholesterol could provide biomarkers to monitor treatment. Upon direct CNS delivery of HP-β-CD, we found increases in plasma 24(S)-HC in two independent NPC1 disease animal models, findings that were confirmed in human NPC1 subjects receiving HP-β-CD. Since circulating 24(S)-HC is almost exclusively CNS-derived, the increase in plasma 24(S)-HC provides a peripheral, non-invasive measure of the CNS effect of HP-β-CD. Our findings suggest that plasma 24(S)-HC, along with the other cholesterol-derived markers examined in this study, can serve as biomarkers that will accelerate development of therapeutics for NPC1 disease.

Neonatal tolerance induction enables accurate evaluation of gene therapy for MPS I in a canine model.

High fidelity animal models of human disease are essential for preclinical evaluation of novel gene and protein therapeutics. However, these studies can be complicated by exaggerated immune responses against the human transgene. Here we demonstrate that dogs with a genetic deficiency of the enzyme α-l-iduronidase (IDUA), a model of the lysosomal storage disease mucopolysaccharidosis type I (MPS I), can be rendered immunologically tolerant to human IDUA through neonatal exposure to the enzyme. Using MPS I dogs tolerized to human IDUA as neonates, we evaluated intrathecal delivery of an adeno-associated virus serotype 9 vector expressing human IDUA as a therapy for the central nervous system manifestations of MPS I. These studies established the efficacy of the human vector in the canine model, and allowed for estimation of the minimum effective dose, providing key information for the design of first-in-human trials. This approach can facilitate evaluation of human therapeutics in relevant animal models, and may also have clinical applications for the prevention of immune responses to gene and protein replacement therapies.

Clinical Improvement of Alpha-mannosidosis Cat Following a Single Cisterna Magna Infusion of AAV1.

Lysosomal storage diseases (LSDs) are debilitating neurometabolic disorders for most of which long-term effective therapies have not been developed. Gene therapy is a potential treatment but a critical barrier to treating the brain is the need for global correction. We tested the efficacy of cisterna magna infusion of adeno-associated virus type 1 (AAV1) expressing feline alpha-mannosidase gene in the postsymptomatic alpha-mannosidosis (AMD) cat, a homologue of the human disease. Lysosomal alpha-mannosidase (MANB) activity in the cerebrospinal fluid (CSF) and serum were increased above the control values in untreated AMD cats. Clinical neurological signs were delayed in onset and reduced in severity. The lifespan of the treated cats was significantly extended. Postmortem histopathology showed resolution of lysosomal storage lesions throughout the brain. MANB activity in brain tissue was significantly above the levels of untreated tissues. The results demonstrate that a single cisterna magna injection of AAV1 into the CSF can mediate widespread neuronal transduction of the brain and meaningful clinical improvement. Thus, cisterna magna gene delivery by AAV1 appears to be a viable strategy for treatment of the whole brain in AMD and should be applicable to many of the neurotropic LSDs as well as other neurogenetic disorders.

Cerebrospinal Fluid Calbindin D Concentration as a Biomarker of Cerebellar Disease Progression in Niemann-Pick Type C1 Disease.

Niemann-Pick type C (NPC) 1 disease is a rare, inherited, neurodegenerative disease. Clear evidence of the therapeutic efficacy of 2-hydroxypropyl-β-cyclodextrin (HPβCD) in animal models resulted in the initiation of a phase I/IIa clinical trial in 2013 and a phase IIb/III trial in 2015. With clinical trials ongoing, validation of a biomarker to track disease progression and serve as a supporting outcome measure of therapeutic efficacy has become compulsory. In this study, we evaluated calcium-binding protein calbindin D-28K (calbindin) concentrations in the cerebrospinal fluid (CSF) as a biomarker of NPC1 disease. In the naturally occurring feline model, CSF calbindin was significantly elevated at 3 weeks of age, prior to the onset of cerebellar dysfunction, and steadily increased to >10-fold over normal at end-stage disease. Biweekly intrathecal administration of HPβCD initiated prior to the onset of neurologic dysfunction completely normalized CSF calbindin in NPC1 cats at all time points analyzed when followed up to 78 weeks of age. Initiation of HPβCD after the onset of clinical signs (16 weeks of age) resulted in a delayed reduction of calbindin levels in the CSF. Evaluation of CSF from patients with NPC1 revealed that calbindin concentrations were significantly elevated compared with CSF samples collected from unaffected patients. Off-label treatment of patients with NPC1 with miglustat, an inhibitor of glycosphingolipid biosynthesis, significantly decreased CSF calbindin compared with pretreatment concentrations. These data suggest that the CSF calbindin concentration is a sensitive biomarker of NPC1 disease that could be instrumental as an outcome measure of therapeutic efficacy in ongoing clinical trials.