The development of gene therapy for Niemann-Pick type C disease

Niemann-Pick type C disease (NPC) is a devastating and ultimately fatal genetic disorder that profoundly affects the brain and other organs of the body. A diagnosis is usually made in infancy/childhood where approximately half of the patients have liver abnormalities. Ten per cent of these patients will die from liver failure before six months of age. The symptoms of NPC patients that survive infancy are dominated by progressive degeneration of the brain with debilitating consequences and subsequent death, usually in the second decade of life. The genetic defect causing NPC in the vast majority of cases is caused by mutations in a gene called NPC1. This causes an accumulation of a number of complex substances such as cholesterol in cells of the body resulting in the symptoms seen the brain and visceral organs. Currently, there are no major specific disease modifying treatments for NPC patients and the need to develop effective life-saving therapies is overwhelming. Gene therapy involves the delivery of a functional copy of a gene into a cell in order to compensate for a defective version. In most cases, the genes are delivered into cells using viral vectors. These vectors are based on viruses that have been stripped of their harmful components, rendered safe and used as a vehicle to efficiently deliver therapeutic genes to cells of the body. Using this approach, gene therapy has demonstrated life-saving and life-changing results in clinical trials. The objective of this project is to develop gene therapy for treating NPC. We have made a viral vector that can efficiently deliver a therapeutic version of the NPC1 gene into cells. We propose using this vector in a pre-clinical proof-of-concept gene therapy study to rescue a mouse model of NPC that recapitulates the symptoms seen in human patients. The aims of this research project are: (1) To deliver the viral vector carrying the therapeutic NPC1 gene directly into the brain of new-born NPC mice to assess, using a range of analyses, whether this ameliorates of prevents the symptoms in the brain. Our preliminary data shows that this has significant therapeutic affect but requires further investigation; (2) To deliver the viral vector intravenously into the bloodstream of new-born NPC mice and assess the therapeutic affect. This viral vector is known to deliver genes to visceral organs and also cross into the brain following intravenous injection. This approach offers potential treatment for both the brain and visceral organs symptoms such as in the liver; (3) To simultaneously deliver the viral vector both directly to the brain and also intravenously to effectively increase the systemic dose and assess the therapeutic efficacy; (4) To deliver the viral vector using the most therapeutically efficacious route of administration (identified in aims 1, 2 and 3) to progressively older mice and assess the therapeutic effect. The purpose of this is to gauge how the gene therapy may perform in more symptomatic mice. This would mimic the potential clinical situation where diagnosis of NPC may be delayed and patients have developed symptoms. It is our hope that this study will provide proof-of-concept data supporting the clinical application of gene therapy as an effective treatment for NPC patients.

NPC is a prematurely fatal autosomal recessive metabolic disorder. A diagnosis is usually made in infancy with approximately half the patients having increased liver bile acid levels. 10% of these patients will die of liver failure within six months of life and those that survive infancy will face progressive neurodegeneration leading to cerebellar ataxia, dysphagia, dementia and death usually in the second decade of life. Most NPC cases are caused by mutations in the NPC1 gene that encodes a late-endosome/lysosome transmembrane protein. The exact role of NPC1 is unknown although it probably has a role in trafficking of cholesterol and sphingolipids as these lipids accumulate in lysosomes of NPC patients and mice. There is currently no major specific disease modifying therapy for patients with NPC and there is an overwhelming need to develop more effective treatments. This project aims to conduct a proof-of-concept pre-clinical study to evaluate the efficacy of AAV9-mediated gene therapy to rescue a mouse model of NPC from neurological and visceral symptoms. We have constructed an AAV9 vector that carries the full-length therapeutic version of the NPC1 gene (AAV9-NPC1). Our preliminary data shows that intracerebroventricular injection of AAV9-NPC1 to newborn NPC1 mice provides significant therapeutic benefit and improves the weight and behaviour compared to uninjected NPC mice. However, more studies are required and our main objectives are to conduct survival, behavioural, biochemical, histological, neuropathology and imaging assessments to ascertain whether: (i) intracerebroventricular; (ii) intravenous or; (iii) a combination of intracerebroventricular and intravenous routes of administration prevent neurological and visceral symptoms and rescue the NPC mice from premature death. Finally, (iv) we will use the most therapeutically efficacious route of administration to treat progressively older and symptomatic NPC mice to evaluate the effect of age on outcome.

Who will benefit from this research?
Our proposal will have broad-ranging impact on several groups. These include: academics (Academic Impact) and healthcare professionals associated with NPC research and treatment, respectively. Ultimately, this research is aimed at impact to the individual NPC patients but also the family members upon whom there is a significant emotional and financial burden (Economic/Societal Impact). The data produced from this proposal would be used to create interaction with clinicians and the growing number of pharmaceutical companies (e.g. GSK, Pfizer, Genzyme and others) concerned with the development of gene therapy for metabolic disorders.

How will they benefit from this research?
Academics/clinicians will gain an insight into whether AAV-mediated gene therapy can ameliorate or prevent the symptoms of the NPC mouse and extend the lifespan. This may also serve as a model to other neurodegenerative diseases similar to NPC involving defective membrane-bound proteins. This pre-clinical study will provide data for engagement with regulatory bodies, relevant pharmaceutical companies and downstream translation to the clinic for direct patient benefit. In addition, we will transfer technical and managerial skills to a new generation of research scientists, either directly (to postdoctoral RAs) or indirectly (to undergraduate or Ph.D. students involved in our research). This will also help to develop an international skill base through the subsequent mobility of these new scientists. Former Ph.D. students and postdoctoral scientists have had positive career trajectories by training in our labs and are now in posts at many other Universities (e.g. Cardiff University, University College Dublin, Dalhousie University and UCL) or industry/healthcare (e.g. Plasticell, National Health Service). Studies from FMP's laboratory led to the development of miglustat that is EMEA (2002) and FDA (2003) approved for treating Gaucher disease and EMA approved (2009) for use in NPC patients. Pre-clinical testing of an AAV vector by SNW's lab contributed to a recent successful clinical trial for haemophilia B. Furthermore, an application to the EMA sponsored by the UK Gauchers Association for orphan designation has been granted for work conducted by AAR and SNW on AAV-mediated gene therapy for neuronopathic Gaucher disease funded by a previous MRC grant (G1000709).

What will be done to ensure that they have the opportunity to benefit from this research?
In the short term (1-3 years), our research will benefit research scientists and clinicians via the presentation of new research findings at lectures in the UK and internationally to scientific and lay audiences, by publishing in internationally-recognised scientific journals, and by engaging with national/international press, television and radio. The past impact of our work on gene therapy, neurodegenerative disorders and NPC is evidenced by the large number of invited lectures that the AAR, FMP and SNW have given and publication of findings in high impact factor journals freely accessible through open access agreements. All applicants are actively involved in public engagement and activities involving patient/family associations. To ensure our findings reach a clinical audience, we are collaborating with Professor Gissen who is directly involved in the care of paediatric NPC patients and the implementation of clinical trials at Great Ormond Street Hospital and the associated UCL Institute for Child Health. AAR's location at UCL allows development of findings and realisation of impact via: i) UCL Advances - a Centre for Entrepreneurship and Business Interactions; ii) UCL Business PLC - a dedicated technology transfer company; iii) UCL Consultants Ltd that facilitates consultancy contracts; iv) UCL Partners - one of five accredited academic health science systems in the UK translating cutting-edge research and innovation into measurable health gains for patients.