Douglas McCarty, PhD– Nationwide Children’s Hospital
Update: Somatic and CNS Gene Delivery for the Treatment of Hunter Syndrome
$62,000 grant (in two instalments) over one year funded January 31, 2016
Status of pre-clinical research program:
- We have completed analysis of enzyme expression levels and correction of lysosomal storage pathology in tissue from five cohorts of MPS II mice treated with the AAV-IDS gene delivery vector. The major conclusions that we’ve reached from the data are that:
- We have determined that a vector with a miniaturized viral promoter controlling the transgene provides more enzyme in the brain and a better therapeutic effect than a mammalian promoter that we used previously. We are planning to use the viral promoter vector for all further development of the gene therapy.
- We have established a minimal effective dose of the gene therapy vector where we see clearance of the lysosomal storage pathology and normalized cognitive behavior at 8 months of age in mice that were treated at 1 month age.
- We have also treated mice with the same vector dose at 3 months of age and 6 months. The treatment was as effective at 3 months as it was a 1 month of age (the normal lifespan of a mouse is around 24 months). The treatment at 6 months cleared the lysosomal storage pathology but was only partially corrective of cognitive behavior when tested at 8 months of age.
- Ongoing experiments and analysis:
- We are maintaining groups of the above treated mice for longevity analysis. The MPS II mouse usually has a lifespan of 15-17 months, so it will be at least another 8 months before these studies are completed. However, we will not wait for the results of this survival study to move ahead with our FDA interactions or the next phase of the program.
- We have treated 6 month old mice with higher doses of the vector to determine whether the disease can be overcome at later stages, and the extent to which it might be reversible. We will also go on to try this in 9 month old mice.
Upcoming developments for Hunter syndrome gene therapy:
We have used the data above from our pre-clinical studies to put together a grant application for the NIH Create (UH2/UH3) program for translational development, which will be submitted on Feb. 11, 2016. While NIH funding is highly competitive, we believe we have a very strong data package, thanks to generous support from Hunter syndrome families and foundations like the MPS II Research Fund, The Isaac Foundation, and many others over the last 2.5 years. We also have a strong team of clinicians and researchers, and we have had positive feedback from NIH program managers in preliminary discussions of our proposal. If successful, this grant would cover major funding outlays including toxicology testing, IND submission to the FDA, production of clinical grade AAV vector, and the clinical trial itself. We are very hopeful for a positive outcome, which we should find out in October.
We are also planning to use this pre-clinical data package to submit a pre-IND meeting with the FDA in March 2016. Pending their input on our toxicology testing plan and clinical trial plan, we will proceed with production of the AAV vector needed for Tox testing, which we plan to produce in partnership with Bamboo Therapeutics, which now operates the Viral Vector Production facilities formerly of the University of North Carolina. Funds for this production and release testing of the AAV vector product will be our next major need. In the meantime, we will begin putting together the IND package to the FDA.
In summary, we are very enthusiastic about the pace of progress in Hunter gene therapy, which has been much faster than our previous programs, largely because we are able to build on our experience in gene therapy for MPS over the last 18 years. We hope to continue this pace of development to reach our goal of a clinical trial as soon as possible.
Scott McIvor, PhD– University of Minnesota
AAV Mediated IDS Gene Transfer for MPS II
$50,000 grant (in two instalments) over one year funded June 12, 2014
Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is an X-linked recessive inherited disorder caused by absence of iduronate-2-sulfatase (IDS), resulting in systemic accumulation of glycosaminoglycans heparan sulphate and dermatan sulphate. Affected individuals suffer from skeletal abnormalities, organomegaly, lifethreatening obstructive airway disease, and, in the severely enzyme deficient form, neurologic degeneration and death by age 15. While there has been great progress in the treatment of MPS II with the availability of enzyme replacement therapy (ERT; Elaprase), administered enzyme does not cross the blood brain barrier. And while transplantation and engraftment of hematopoietic stem cells has shown efficacy in the treatment of some MPS diseases, allografted MPS II patients have thus far not exhibited improved neurologic outcomes. Affected MPS II individuals thus currently have no clinical options available for neurologic manifestations of the disease. We have been working on adeno-associated virus (AAV) vectors administered directly to the CNS to achieve high levels of enzyme in the treatment of MPS disease, and we have demonstrated high levels of iduronidase after either intracerebroventricular or intrathecal administration of AAV vector in MPS I mice. Here we propose to test several AAV vectors assembled for expression of human IDS in achieving high levels of IDS expression, correction of storage disease, and prevention of neurocognitive decline in MPS II mice as a model for gene therapy of the neurologic manifestations of MPS II. Results from these studies will constitute significant preclinical support for preparation of an IND and initiation of clinical trials for treatment of MPS II neurologic disease by direct AAV mediated gene transfer to the CNS.
Brian Bigger, PhD– University of Manchester
Evaluating stem cell gene therapy for treating the brain in Mucopolysaccharidosis II
$50,000 grant (in two instalments) over one year funded June 12, 2014
Mucopolysaccharidoses (MPS) are inherited diseases caused by the lack of an enzyme that breaks down complex sugars. Hunter (MPSII) affects children and in severe form results in progressive mental decline, behavioural difficulties, and a shortened lifespan due to storage of complex sugars in the brain. No treatments are effective for the brain, therefore Hunter represents an urgent unmet clinical need.
The main hurdle to therapy development has been the ability to deliver enough replacement enzyme across the blood-brain barrier (BBB). MPSIH (Hurler’s) can be treated by a bone marrow transplant where some of the transplanted cells are able to traffic across the BBB and produce enzyme which can be taken up by other cells reducing storage of complex sugars, neuroinflammation and brain degeneration. Unfortunately this approach does not work for Hunter.
Our aim is to increase the amount of enzyme produced by stem cells after transplant using gene therapy in a mouse model of MPSII. A clinical trial using this strategy to treat a similar neurodegenerative disease is underway in Italy and once we have demonstrated preclinical proof, we plan to take this therapy into the clinic. We believe that this research fulfils The Isaac Foundation’s remit since it is focused on treating MPS diseases.
Douglas McCarty, PhD– Nationwide Children’s Hospital
Somatic and CNS Gene Delivery for the Treatment of Hunter Syndrome
$110,000 grant over 2 years ($55,000 each year) funded September 22, 2013
The objective of this project is to develop gene therapy for the combined treatment of both the neurologic and somatic pathology of MPS II by systemic gene delivery. This approach takes advantage of the vast expanse of vasculature serving critical organs and tissues, particularly the brain, and the recently recognized ability of some serotypes of adeno-associated virus (AAV) to cross the blood-brain-barrier. Due to the relatively small size of the human IDS gene, we will utilize self-complementary AAV constructs, which essentially contain both strands of the DNA double helix rather than a single strand as in conventional AAV vectors. Packaged in an AAV serotype 9 capsid, these vectors can restore deficient genes in somatic tissues including liver, skeletal muscle, and heart, and have the ability to cross the blood-brain barrier for CNS delivery. Part of this objective will include the comparison of two different transcriptional promoters to control expression of the IDS gene: the ubiquitously active mouse U1a promoter, which has been effective for CNS expression and improvement of cognitive function in the MPS IIIA mouse model; and a miniaturized promoter derived from cytomegalovirus, with potentially higher activity in muscle and heart tissues. Similar AAV9 vector constructs are under development for a wide variety of somatic and CNS diseases, with a strong record of safety and efficacy in pre-clinical models which will provide further support for the direct translation of this project into a workable gene therapy treatment.
Emyr Lloyd-Evans, MD, PhD– University of Cardiff
Utilising Neuronal Stem Cell Models to Develop Small Molecule Therapies for MPS II
$50,000 grant funded March 17, 2011
We are aiming to develop a cellular model of Hunter Syndrome brain (MPSII). To do this we will take stem cells from the MPSII mouse model and using careful conditions will change these cells into neurons. This cellular model will help in studying the brain pathology of MPSII but can also be used to test the effects of therapy on the MPSII brain. We will study both these aspects. We are particularly interested in looking at the effects of a novel chemical compound we have isolated from Malaysian plants. In some preliminary experiments, we found that one of these compounds is capable of reducing storage in MPSII human skin cells but not in cells from other lysosomal diseases. We aim to fully study the effects of this compound on MPSII neuronal stem cells. Finally we are interested in using neuronal stem cells to study the order in which disease events happen in MPSII. We have done this before in Niemann-Pick C1 disease5, where we identified defects in lysosomal calcium homeostasis as an early disease event and a therapeutic intervention point that enhances NPC1 mouse function. Such a study in MPSII will determine the mechanisms leading to cellular pathogenesis and identify novel therapeutic intervention points. This proposal is in line with the Canadian MPS Society’s remit and this RFA as the main aims are to develop cellular tools for the MPS community, study novel therapies for MPSII and determine the cellular pathogenic events that occur in the MPSII brain.
Joseph Muenzer, MD, PhD – University of North Carolina
MPS II AAV Gene Therapy
$50,000 grant funded August 30, 2009
Mucopolysaccharidosis II (Hunter syndrome, MPS II) is caused by the deficiency of the lysosomal enzyme iduronate sulfatase (Id-S). Deficiency of Id-S results in accumulation of dermatan and heparan sulfate, with progressive tissue and organ damage, and in the severe form, premature death. No definitive treatment is available for MPS II patients. IV administration of Elaprase (recombinant Id-S) is available for MPS II patients, but requires ongoing weekly infusions and is not expected to impact the brain disease in the severe form of MPS II. The current focus of my laboratory is to develop gene therapy as a treatment for the central nervous system in patients with Hunter syndrome utilizing a mouse model for MPS II created in the laboratory. Gene therapy is a procedure where genetic material is inserted or delivered into cells to treat a disorder. We are developing a delivery system using a modified adeno-associated virus (AAV) to insert genetic material into cells that will allow production of Id-S and the subsequent correction of storage. Our initial AAV2 gene therapy research has shown complete correction of liver storage and partial correction of brain storage in MPS II mice after IV administration of the AAV2 vector. This research proposal is to study the short-term effectiveness of three different AAV vectors compared to the standard AAV2 when injected directly into the fluid surrounding the brain in MPS II mice. We hypothesize that different AAV forms will enhance enzyme production and thereby improved correction of storage in the brain. The successful completion of these studies will determine which AAV vectors should be tested in long-term (>12 months) studies to determine clinical benefit and to develop preclinical data for human gene therapy clinical trials in MPS II patients.
Lorne Clarke, MD- University of British Columbia
Serum Biomarker for MPS
$40,000 grant funded in March 2008
The mucopolysaccharidoses (MPSs) represent a group of complex progressive multi-system diseases which are caused by metabolic defects in the degradation of glycosaminoglycans (GAGs). The recent introduction of enzyme replacement (ERT) regimes for MPS I and MPS II has brought to light the importance of developing objective methods to evaluate patients. The clinical heterogeneity manifest as variable age of onset as well as variable rates of disease progression, clearly complicate the ability of physicians to accurately prognosticate clinical course for individual patients and leads to significant difficulty in objectively evaluating the effectiveness of treatment regimes. The development of biomarkers that reflect disease severity, disease progression and responsiveness to treatment regimes will be an invaluable tool.
My laboratory has identified a potential serum biomarker for the MPSs and propose in this grant application to develop a sensitive and specific ELISA based assay for this biomarker.
Murray Potter, MD- McMaster University
Brain Targeted MPS II therapy delivered microencapsulated cells
Half of a $40,000 grant, plus a $4,000 summer studentship grant, funded in June 2007
MPS II, or Hunter syndrome, is an inherited disorder affecting males caused by deficiency of the enzyme iduronate sulfatase. This deficiency causes bone abnormalities, organ enlargement, brain deterioration and early death. It is now possible to treat many features of MPS II by weekly injections of a purified form of the missing enzyme (enzyme replacement therapy, ERT). Unfortunately, the brain remains difficult to treat. We are developing a new treatment that targets the brain by modifying the replacement enzyme so that it can better reach the brain. The modification involves adding a targeting signal called “TAT” to the enzyme. TAT has been successfully shown to deliver other proteins and enzymes to the brain in animal experiments.
Instead of directly injecting the modified enzyme, we will transplant cells that can produce the enzyme. Transplantation removes one of the drawbacks of ERT, which is the need for weekly injections. The cells will be placed inside a special microcapsule to protect them from rejection, allowing one transplantation procedure to last for months or years. Microencapsulated cells have already successfully been used in animal experiments, including treatment of MPS II mice.
We feel that this research will bring a treatment for the brain disease in MPS II and related disorders closer to reality. This goal is directly related to one of the underlying purposes of the Canadian MPS Society, that of finding a cure for all MPS.