Development of an AAV vector for treatment of inherited retinal dystrophy caused by RPE65 deficiency

Lead Research Organisation: University College London
Department Name: Institute of Ophthalmology

Abstract

Leber congenital amaurosis (LCA) is a severe inherited retinal dystrophy with a population frequency around 1/50,000, characterised by loss of vision in childhood. Approximately 5% of LCA is caused by mutations in the RPE65 gene, which encodes a retinal pigment epithelium (RPE) specific protein essential for recycling of retinoids to the photoreceptor cells. The results of our trial, and 2 similar trials in the US, show for the first time the impact of this novel therapy on a condition that was previously untreatable. Whilst some subjects in all the trials have benefited from this new intervention, the extent of response in human subjects does not match the improvements in mice and dogs with the same genetic defect. Our data indicates that this difference reflects a greater requirement for RPE65 in humans than in rodents and dogs, and this is not fully met with the current version of the vector. The aim of this project is to improve the efficacy of gene therapy for LCA2 by optimising the RPE65 construct through a number of specific modifications. Since we have reached the maximal tolerated vector dose in these subjects, we intend to improve the efficiency of transgene expression levels by optimising the construct through a number of specific patentable modifications. By improving the efficiency of d protein production we aim to achieve a more than 100-fold reduction in the vector dose required for the optimal treatment in animal models of the disease. The RPE65 protein levels obtained from the improved vector will be tested initially in vitro. One or two constructs with a proven ability to drive higher levels of expression in vitro will be used in animal studies, first in mice and subsequently in dogs in order to test whether lower doses of the new vector can achieve equivalent rescue of retinal function and rescue of vision.

Successful completion of this project will enable us to develop a clinical trial of an improved AAV vector for the treatment of LCA2. A more effective construct should enable us to develop a highly effective gene therapy vector that has the potential to be one of the world's first first licenced gene therapy products for clinical application. This would have considerable impact on the quality of life of the patients, with benefits ranging from improved nightvision to improved visual acuity and preservation of vision over time, depending on the condition of the retina at the time of treatment. As the best outcome is expected after treatment early in life, most commonly the end users would be pre-teen LCA2 patients, although ongoing clinical trials have shown that patients up to twenty years of age can benefit from treatment. The young age of the subjects means that a optimally successful treatment outcome could result in years of increased visual acuity and/or a wider visual field, with concomitant improvements in self-sufficiency and potentially other economic benefits. LCA is a relatively rare condition with a population frequency of approximately 1/50,000. In the UK around 5% of all forms of LCA are caused by RPE65 mutations and thus potential end-users for AAV-RPE65 gene therapy. Only patients under the age of 20 are likely to benefit from treatment; however, in this group a near-complete take-up of an established therapy is expected.

Retinal dystrophy is a highly diverse group of disorders that can be caused by mutations in as many as 200 different genes. The core technology used in this application - subretinal injection of AAV vectors carrying a transgene - will be suitable for the development of gene therapy protocols for the majority of retinal dystrophies. Robust proof-of-concept studies have been reported for AAV-mediated gene therapy for ten forms of inherited retinal degeneration, of which we have reported five. The results obtained in this project will also facilitate the progression of these therapies to clinical application.

Technical Summary

Leber congenital amaurosis (LCA) is a severe inherited retinal dystrophy with a population frequency around 1/50000, characterised by loss of vision in the first decade of life. Approximately 5% of LCA cases is caused by mutations in the RPE65 gene, which encodes a retinal pigment epithelium (RPE) specific protein essential for recycling of retinoids to the photoreceptor cells. Three independent clinical trials of AAV2 mediated gene therapy, including one performed by our group, have shown improvements in retinal sensitivity and vision. However, the level of improvement is lower than expected from pre-clinical experiments in rodents and dogs. Our recent data suggest this may be due to a higher need for RPE65 activity in the human eye and we therefore intend to further develop the targeting vector to drive higher transgene expression levels through a variety of patentable modifications.

Planned Impact

Leber congenital amaurosis (LCA) is the leading cause of vision loss in children, typically causing visual impairment within the first decade of life, although LCA type 2, caused by mutations in the RPE65 gene is one of the milder forms of the disease, generally leading to blindness in the second decade. Thus far, no established successful treatments exist for this disease, but on-going clinical trials - including one conducted by our group - for LCA2 have resulted in encouraging, but modest improvements in retinal sensitivity and scotopic vision. However, more substantial improvements in vision have been observed in animal studies and we have recent data to indicate that the level expression of RPE65 in the human retina is higher than in animals. This suggests that after further optimisation of the transfer vector, a more substantial rescue of vision should be feasible. A more effective construct should enable us to develop a highly effective gene therapy vector that has the potential to be one of the world's first first licenced gene therapy products for clinical application. This would have considerable impact on the quality of life of the patients, with benefits ranging from improved nightvision to improved visual acuity and preservation of vision over time, depending on the condition of the retina at the time of treatment. As the best outcome is expected after treatment early in life, most commonly the end users would be pre-teen LCA2 patients, although ongoing clinical trials have shown that patients up to twenty years of age can benefit from treatment. The young age of the subjects means that a optimally successful treatment outcome could result in years of increased visual acuity and/or a wider visual field, with concomitant improvements in self-sufficiency and potentially other economic benefits. LCA is a relatively rare condition with a population frequency of approximately 1/50,000. In the UK around 5% of all forms of LCA are caused by RPE65 mutations and thus potential end-users for AAV-RPE65 gene therapy. Only patients under the age of 20 are likely to benefit from treatment; however, in this group a near-complete take-up of an established therapy is expected.

Retinal dystrophy is a highly diverse group of disorders that can be caused by mutations in as many as 200 different genes. The core technology used in this application - subretinal injection of AAV vectors carrying a transgene - will be suitable for the development of gene therapy protocols for the majority of retinal dystrophies. Robust proof-of-concept studies have been reported for AAV-mediated gene therapy for ten forms of inherited retinal degeneration, of which we have reported five. The results obtained in this project will also facilitate the progression of these therapies to clinical application.
 
Description BRC Theme
Amount £794,946 (GBP)
Funding ID BRC3_002 
Organisation National Institute for Health Research 
Sector Public
Country United Kingdom
Start 04/2017 
End 03/2022
 
Description Equipment grant (retinal imaging)
Amount £737,000 (GBP)
Funding ID 099173/Z/12/Z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2012 
End 10/2017
 
Description Project Grant (CNGB3)
Amount £2,152,639 (GBP)
Funding ID MR/K025589/1 
Organisation Medical Research Council (MRC) 
Sector Public
Country United Kingdom
Start 11/2013 
End 06/2019
 
Description Public Engagement
Amount £30,000 (GBP)
Funding ID 100847/Z/13/Z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 11/2013 
End 10/2016
 
Description Riken Institute, Kobe, Japan 
Organisation RIKEN
Country Japan 
Sector Public 
PI Contribution We trained Japanese group in cell transplantation to retina
Collaborator Contribution Partly funded a collaborative exchange that enabled us to learn latest stem cell differentiation protocols from leading group.
Impact Resulted in an award being made by the Royal Society in recognition of the collaboration and to support a 3 month visit by one of the post doctoral researchers working on the project
Start Year 2008
 
Description University of Michigan 
Organisation Michigan State University
Department College of Veterinary Medicine
Country United States 
Sector Academic/University 
PI Contribution We provide gene therapy vectors
Collaborator Contribution The partners test our gene therapy vectors in their dog models of inherited retinal disease
Impact publications and data for clinical trials regulatory submissions
Start Year 2006
 
Title Optimised gene therapy vector for RPE65 deficiency 
Description Optimised AAV vector for treatment of LCA2 
IP Reference WO2016128722 
Protection Patent application published
Year Protection Granted 2015
Licensed Yes
Impact Paper published in Gene Therapy (Georgiadis et al 2016)
 
Company Name Athena Vision Ltd 
Description Ocular gene therapy company 
Year Established 2015 
Impact Has raised substantial funding and will develop a programme of clinical trials with 2 new multi-centre US/UK trials of ocular gene therapy over the next 3 years. Has secured GMP facility for manufacturing for viral vectors.
Website http://www.athena-vision.com
 
Description AMD Day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact This free one-day event organised by Prof. Ali's team provided an opportunity for people with Age-Related Macular Degeneration (AMD) to hear first-hand about the progress being made in world-leading research into gene and stem cell therapies as well as devices for AMD. Over 60 clinicians (including consultants), researchers, students and members of charitable organisations who fund research attended the day to assist and learn from the event, with many of Prof. Ali's group also giving talks or presenting posters.

189 people attended and the audience largely consisted of patients and their relatives/friends/carers who were mostly from the UK, particularly the Greater London area, but also from Brussels, Antwerp, Barcelona and Texas.

The day began with a series of short talks, which generated numerous questions and discussions. The afternoon session was an exhibition of posters, stalls and information from relevant charities and demonstrations by our event partner, the Macular Society. This offered the opportunity for guests to speak to researchers and clinicians one on one and to provide valuable feedback, through interactive posters, on our event/engagement activities and research focus. The charities provided advice on the the support available and to demonstrate new visual aids available to them.

Pre and post event questionnaires were completed by the attendees to help us ensure that their needs were met and how to make improvements for future events. There was a 70% return on questionnaires and the key findings were:

- 97% of the attendees felt the event met or exceed their expectations
- The majority of attendees felt the event had increased their knowledge about AMD
- The results of the 'Where do you think their needs to be more focus and support for people with AMD?' poster demo
Year(s) Of Engagement Activity 2014
URL http://www.ucl.ac.uk/ioo/genetics/gene-and-cell-therapy/amd-day-2014
 
Description BRPS AGM 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact British Retinitis Pigmentosa Society AGM

circulated research findings to patients
Year(s) Of Engagement Activity 2008,2009,2010,2011,2012
 
Description Departmental website 
Form Of Engagement Activity A magazine, newsletter or online publication
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Regular updates to departmental website giving an over view of work being conducted.

Attracted research funds from a donor
Year(s) Of Engagement Activity 2008,2009,2010,2011,2012
 
Description FBI AGM 
Form Of Engagement Activity A formal working group, expert panel or dialogue
Part Of Official Scheme? No
Type Of Presentation Keynote/Invited Speaker
Geographic Reach International
Primary Audience Participants in your research and patient groups
Results and Impact AGM Fighting Blindness, Ireland

research circulated to patients
Year(s) Of Engagement Activity 2009,2010,2011,2012
 
Description Retina Patient Day 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Participants in your research and patient groups
Results and Impact We organised a day for patients with retinal disorders to hear about our my groups gene and cell therapy research.
350 patients and their families attended. We presented 50 posters and gave 8 short talks.

Increased interest in our website updates and increased donations.
Year(s) Of Engagement Activity 2012