Vol. 13 Supplement 1
Brain Targeting in MPS-IIIA
Nicolina Cristina Sorrentino, PhD, Alessandro Fraldi, PhD
Mucopolysaccharidosis type IIIA (MPS-IIIA) is a childhood metabolic neuropathology caused by the inherited deficiency of the lysosomal enzyme sulfamidase and is characterized by the accumulation of undegraded glycosaminoglycans in the lysosomes of cells and tissues of affected patients. MPS-IIIA represents one of the most common forms of lysosomal storage disorders (LSDs) and to date there is no cure. Since neurodegeneration is the most relevant pathological feature in MPS-IIIA patients, the treatment of the central nervous system (CNS) lesions represents the goal of any effective therapy for this devastating disorder. During the last years many advances have been made in developing and testing new therapies for brain involvement in MPS-IIIA. These studies have been possible because of the availability of mouse and dog models that recapitulate the MPS-IIIA neuropathological features. Some of these approaches are based on direct CNS administration routes through which the therapeutic molecules access the CNS via the parenchyma (intracerebral injections) or via the cerebrospinal fluid (intraventricular/intrathecal injections). These approaches are highly invasive and poorly suited for clinical use. Minimally invasive approaches are based on systemic injections into the blood stream of therapeutics capable of crossing the blood-brain barrier (BBB). This review will present the background of the clinic and pathology aspects of MPS-IIIA and will describe the current MPS-IIIA preclinical and clinical studies focusing on how a systemic therapeutic strategy based on crossing the BBB has been successfully used to treat CNS pathology and behavioral abnormalities in a mouse model of MPS-IIIA. Future clinical applications of this approach to MPS-IIIA patients will be also discussed together with the possibility of using similar strategies in other LSDs with neurological involvement.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):630-638
Key words: MPS-IIIA; Sulfamidase; Lysosomal storage disorders, BBB; CNS therapy
Combination Therapies for Lysosomal Storage Diseases: A Complex Answer to a Simple Problem
Shannon L Macauley, PhD
Lysosomal storage diseases (LSDs) are a group of 40-50 rare monogenic disorders that result in disrupted lysosomal function and subsequent lysosomal pathology. Depending on the protein or enzyme deficiency associated with each disease, LSDs affect an array of organ systems and elicit a complex set of secondary disease mechanisms that make many of these disorders difficult to fully treat. The etiology of most LSDs is known and the innate biology of lysosomal enzymes favors therapeutic intervention, yet most attempts at treating LSDs with enzyme replacement strategies fall short of being curative. Even with the advent of more sophisticated approaches, like substrate reduction therapy, pharmacologic chaperones, gene therapy or stem cell therapy, comprehensive treatments for LSDs have yet to be achieved. Given the limitations with individual therapies, recent research has focused on using a combination approach to treat LSDs. By coupling protein-, cell-, and gene- based therapies with small molecule drugs, researchers have found greater success in eradicating the clinical features of disease. This review seeks to discuss the positive and negatives of singular therapies used to treat LSDs, and discuss how, in combination, studies have demonstrated a more holistic benefit on pathological and functional parameters. By optimizing routes of delivery, therapeutic timing, and targeting secondary disease mechanisms, combination therapy represents the future for LSD treatment.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):639-648
Key words: Lysosomal storage diseases, Combination therapy, Gene therapy, Enzyme replacement
Prevention is the Best Therapy: The Geneticist’s Approach
Gheona Altarescu, MD
During the last two decades prenatal genetic screening and diagnosis has become the cornerstone of medical care for family planning to prevent genetic disease.
Carrier screening programs for genetic disorders that are prevalent in various populations identify couples and pregnancies at risk of having an affected child. These couples can proceed with a choice of invasive prenatal diagnosis tests of the fetus (chorionic villous sampling and amniocentesis), or non-invasive prenatal testing of free fetal DNA circulation in the maternal blood which has emerged within the last few years and is currently available for fetal sexing for X Linked disorders. Despite the advances in prenatal diagnosis, couples found to have a fetus affected with a genetic disorder may need to face the dilemma of pregnancy termination.
Preimplantation genetic diagnosis (PGD) is an alternative to preempt risk of having a child affected with a life-altering genetic disorder. This technique allows biopsy and genetic diagnosis of embryos obtained from in vitro fertilization by analysis of the genetic material from one or a few embryonic cells. Only unaffected embryos are returned to the mother to establish the pregnancy.
We present our experience using PGD for four Lysosomal storage disorders: Tay Sachs, Gaucher type 1, Hunter and Fabry disease with some of the couples being carriers of more than one genetic disorder. PGD is applicable to most disorders for which the gene and the familial mutation are known and should be presented to couples as an alternative to invasive prenatal testing.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):649-654
Key words: Prenatal genetics test, Preimplantation genetic diagnosis, Prevention genetic diseases
Juvenile NCL (CLN3 Disease): Emerging Disease-Modifying Therapeutic Strategies
Erika F. Augustine, MD, MS, Jonathan W. Mink, MD, PhD
Juvenile Neuronal Ceroid Lipofuscinosis is a lysosomal storage disease characterized pathologically by intracellular accumulation of autofluorescent storage material and neurodegeneration. Caused by mutations in the CLN3 gene on chromosome 16p12, the precise functions of the encoded protein remain unclear. Yet, recent preclinical discovery has established new therapeutic targets in development, including immunosuppressants, anti-inflammatories, and gene replacement therapies. Development of robust clinical trial endpoints appropriate for this poly-symptomatic disease, clinical trial design optimized for small samples, and adequate and efficient participant recruitment are challenges that lay ahead.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):655-662
Key words: Neuronal ceroid lipofuscinosis, JNCL, Batten Disease, CLN3, Neurodegenerative disease, Lysosomal storage disease, Mycophenolate, GAD antibody, Flupirtine
The GM1 and GM2 Gangliosidoses: Natural History and Progress toward Therapy
Debra S. Regier, MD, PhD, Richard L. Proia, PhD, Alessandra D’Azzo, PhD, Cynthia J. Tifft, MD, PhD
The gangliosidoses are lysosomal storage disorders caused by accumulation of GM1 or GM2 gangliosides. GM1 gangliosidosis has both central nervous system and systemic findings; while, GM2 gangliosidosis is restricted primarily to the central nervous system. Both disorders have autosomal recessive modes of inheritance and a continuum of clinical presentations from a severe infantile form to a milder, chronic adult form. Both are devastating diseases without cure or specific treatment however, with the use of supportive aggressive medical management, the lifespan and quality of life has been extended for both diseases. Naturally occurring and engineered animal models that mimic the human diseases have enhanced our understanding of the pathogenesis of disease progression. Some models have shown significant improvement in symptoms and lifespan with enzyme replacement, substrate reduction, and anti-inflammatory treatments alone or in combination. More recently gene therapy has shown impressive results in large and small animal models. Treatment with FDA-approved glucose analogs to reduce the amount of ganglioside substrate is used as off-label treatments for some patients. Therapies also under clinical development include small molecule chaperones and gene therapy.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):663-673
Key words: GM1 gangliosidosis, GM2 gangliosidosis, Tay Sachs disease, Animal models, Treatments
Types A and B Niemann-Pick Disease
Edward H. Schuchman, PhD, Melissa P. Wasserstein, MD
Two distinct metabolic abnormalities are included under the eponym Niemann-Pick disease (NPD). The first is due to the deficient activity of the enzyme acid sphingomyelinase (ASM). Patients with ASM deficiency are classified as having types A and B Niemann-Pick disease (NPD). Type A NPD patients exhibit hepatosplenomegaly, frequent pulmonary infections, and profound central nervous system involvement in infancy. They rarely survive beyond two years of age. Type B patients also have hepatosplenomegaly and progressive alterations of their lungs, but there are usually no central nervous system signs. The age of onset and rate of disease progression varies greatly among type B patients, and they frequently live into adulthood. Recently, patients with phenotypes intermediate between types A and B NPD also have been identified. These individuals represent the expected continuum caused by inheriting different mutations in the ASM gene (SMPD1). Patients in the second category are designated as having type C NPD. Impaired intracellular trafficking of cholesterol causes type C NPD, and two distinct gene defects have been found. In this chapter only types A and B NPD will be discussed.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):674-681
Key words: Niemann-Pick, Acid Sphingomyelinase, Sphingomyelin, Mouse Model, Enzyme Replacement Therapy
CLN2 Disease (Classic Late Infantile Neuronal Ceroid Lipofuscinosis)
Alfried Kohlschütter, MD, Angela Schulz, MD
CLN2 disease is an inherited metabolic storage disorder caused by the deficiency of the lysosomal enzyme tripeptidyl peptidase 1 (TPP1). The disease affects mainly the brain and the retina and is characterized by progressive dysfunction of the central nervous system, leading to dementia, epilepsy, loss of motor function and blindness. The classical late infantile type begins at around three years of age with epilepsy and/or a standstill of psychomotor development, followed by a rapid loss of all abilities and death in childhood. A late onset form in a small proportion of patients starts at the age of 4 to 10 years, but also leads to severe neurological deterioration. The deficiency of TPP1 causes the lysosomal accumulation of a material called ceroid lipofuscin. The natural substrate of TPP1 is not known, nor is the connection between storage process and neurodegeneration, which is characterized by loss of neurons. Among various experimental approaches to treatment, enzyme replacement therapy (ERT) and gene therapy have developed remarkably. Enzyme delivery through the cerebrospinal fluid led to wide distribution of enzyme activity in the brain and to attenuated neuropathology and disease progression in a TPP1-deficient mouse model as well as in a natural TPP1-deficient dog model. Safety of the intrathecal delivery, pharmacokinetics, and tissue distribution of the administered enzyme studied in non-human primates were encouraging, and a phase I/II clinical trial for intraventricular ERT in CLN2 patients is ongoing. A second approach uses intracerebral injection of viral vectors containing normal coding segments of the CLN2 gene. In a CLN2 mouse model, this procedure resulted in cerebral enzyme expression, reduced brain pathology and increased survival. A small number of patients have been treated the same way using an AAV2-vector for gene transfer to the brain. Although there were no serious adverse events unequivocally attributable to the vector used, there were some serious adverse effects, and a clinical benefit was not clearly evident under the conditions of the experiment. A phase I/phase II study using a AAVrh10 vector is presently recruiting patients.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):682-688
Key words: Degenerative brain disease, Children, Lysosomal disorders, Experimental therapy
Insights into the Pathogenesis and Treatment of Krabbe Disease
Ernesto Roque Bongarzone, PhD, Maria Luisa Escolar, MD, Steven James Gray, PhD, Tal Kafri, PhD, Charles Herman Vite, DVM, PhD, Mark Steven Sands5, PhD
Krabbe disease (globoid cell leukodystrophy, GLD) is an inherited disease caused by a deficiency in the lysosomal enzyme galactocerebrosidase (GALC). The major galactosylated lipid degraded by GALC is galactosylceramide. However, GALC is also responsible for the degradation of galactosylsphingosine (psychosine), a highly cytotoxic glycolipid. It has been hypothesized that GALC-deficiency leads to psychosine accumulation that preferentially kills oligodendrocytes in the central nervous system and Schwann cells in the peripheral nervous system. Krabbe disease has traditionally been considered a white matter disease characterized by the loss and disorganization of myelin, infiltration of multinucleated monocytes/macrophages (globoid cells) and lymphocytes, and dysregulation of pro-inflammatory cytokines and chemokines. However, new studies have revealed unexpected neuronal deficiencies. Infantile Krabbe disease is believed to be the most common and aggressive form. However, juvenile and adult onset forms have been described. Children affected with infantile Krabbe disease present with motor dysfunction, cognitive decline, intractable seizures, and premature death between two to five years of age. Murine, canine, and primate models of GALC deficiency have been described and have played an important role in our understanding of this invariably fatal disease. Although there is no cure for Krabbe disease, hematopoietic stem cell transplantation can slow the progression of disease. Recent pre-clinical data indicate that simulataneously targeting multiple pathogenic mechanisms greatly increases efficacy in the murine model of Krabbe disease. A better understanding of the underlying pathogenesis will identify new therapeutic targets that may further increase efficacy.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):689-696
Key words: Krabbe disease, Globoid cell leukodystrophy, Twitcher mouse, Gene therapy, Bone marrow transplantation, Demyelinating disease
Therapy Development for the Lysosomal Storage Disease Fucosidosis using the Canine Animal Model
Jessica L. Fletcher, BAnVetBioSc (Hons I), PhD, Rosanne M. Taylor, BVSc (Hons I), DipVetClinStud, GradCertEducStud (Higher Education), PhD
Fucosidosis (OMIM 23000) is an inherited neurodegenerative lysosomal storage disease caused by a deficiency of the lysosomal hydrolase α-L-fucosidase due to mutations in the FUCA1 gene. Without enzyme-targeted therapy patients rarely survive beyond the first decade of life, and therapy options other than supportive care are limited. Hematopoietic transplants, first developed in the fucosidosis dog model, are the only treatment option available capable of delaying the disease course. However, due to the risks and exclusion criteria of this treatment additional therapies are required. The development of additional therapies including intravenous and intra-cerebrospinal fluid enzyme replacement therapy and gene therapy, which have been trialed in the canine model, will be discussed.
Ref: Ped. Endocrinol. Rev. 2016;13(Suppl 1):697-706
Key words: Glycoproteinoses, Lysosomal storage disease, Hematopoietic cell transplantation, Enzyme replacement therapy, Canine fucosidosis, Inherited metabolic disease