Establishment of innovative and proprietary methods for the manufacturing and quality control testing of a clinical grade gene therapy vector for the treatment of patients affected with a pigmented retinopathy secondary to a mutation in the pde6ß gene – PDE6-ß

The proposed methodology relies on the development and validation of an optimized and efficient manufacturing process of the AAV2/5.RK.pde6ß vector. Particularly, this process relies on an innovative purification technology using highly resolutive, monolithic ion exchange chromatographic matrix. In the same time, specific quality control assays will be developped, demonstrating the vector safety and potency, allowing its administration into humans. Particularly, an in vitro assay, confirming the pde6ß expression under the control of the Rhodopsin Kinase promoter (RK) and the enzymatic activity after gene transfer will be developped.
Furthermore, in order to confirm the therapeutic effect and its safety, the « drug-candidate » viral vector will be injected subretinally into naturally pde6ß-deficient dogs. Two months after subretinal administration, the morphology and the function of the retina will be evaluated for each treated dog, as well as an eventual immune response induced by the gene transfer ; precisely, over a 6 months period of time, the treated retina function will be assessed by electroretinography ; fundoscopy and optical coherence Tomography will be performed to assess the retina morphology. Humoral immune response against the vector itself and the gene produc twill be evaluated using an ELISA assay performed on serum samples regularly retrieved from treated dogs. Neutralizing antibodies against the vector will also be evaluated in the serum sample using an anti-AAV5 neutralizing antibody assay.

The main expected output of this project is the availability of a robust and efficient production process for the AAV2/5.RK.pde6ß vector, complying with the pharmaceutical requirements (GMP). The ability to produce such a gene therapy vector enlarge the field of potential indications to many other retinal diseases affecting photoreceptors : Stargardt disease, Retinitis Pigmentosa caused by mutation in the rpgrip1 gene, Achromatopsia type II…
The launching of a spin-off company is also planned to exploit the results of this projects. This company will carry on the clinical development, and hopefully the marketing, of the drug candidates produced using the technology developped through this program.

«rAAV5.Rk.PDE6ß targets the market of monogenic hereditary retinal dystrophies caused by PDE6ß gene deficiencies. These deficiencies are parts of the autosomal recessive Retinitis Pigmentosa (arRP) diseases. arRP are characterized by progressive bilateral degeneration of the rod and cone photoreceptors that leads to night blindness and progressive visual field defects; and there is currently no efficient treatment for these diseases. Retinal dystrophies caused by PDE6ß gene deficiencies counts for 5% of the total arRP representing about 3.500 people and forty or so newly patients every year in the EU. Establishing the efficacy of GMP rAAV5.Rk.PDE6ß vector in human would pave the way for numbers of new gene therapy products targeting gene deficiencies in photoreceptors.«

An article was published in july 2012 demonstrating for the first time that an AAV-mediated gene therapy strategy efficiently restores the visual function in a large animal model (the pde6ß-deficient dogs) of retinal dystrophy affecting photoreceptors.
(Restoration of Vision in the pde6ß-deficient Dog, a Large Animal Model of Rod-cone Dystrophy. Petit L et al., Mol Ther 2012).

Our lab has recently demonstrated (manuscript in preparation) for the first time that a retinal genetic disease affecting rods could benefit from gene therapy.
The current application is centered towards the translational development of a clinical grade viral gene therapy product that would become an innovative drug candidate to treat a retinal genetic disease (PDE6ß deficiency) resulting, so far, in incurable blindness in young patients.
Our 70-people laboratory, UMR649 located at the University Hospital of Nantes is a unique gene therapy organization in the country since we combine: (i) an INSERM research group; (ii) a development team and, (iii) a manufacturing and quality control lab. This expertise relies on several core facilities that we have built on site over the past 10 years, which include: (i) a research vector core, (ii) an EMA-compliant pathology core, (iii) a BL2/BL3 large animal facility for preclinical and regulatory toxicology studies and, (iv) a GMP-compliant vector core for the manufacture and control of clinical grade vectors.
For the following reasons, we believe that UMR649 and its partner INSERM-Transfert are the most competitive in the country to support the current project presented herein: (i) we have recently completed the full translational program for the treatment of RPE65-deficient blind patients including the proof-of-concept, the GMP-compliant manufacturing of the viral vector and its quality control, the regulatory toxicology study, the clinical design and the submission of the full IND to the French regulatory agency AFSSaPS with the first RPE65-deficient patients expected to be enrolled in Sept 2011, (ii) we recently demonstrated for the first time that in a PDE6ß-deficient dog, vision can be rescued (cf paragraph 2.3) (manuscript in preparation), therefore providing the proof-of-concept, (iii) the therapeutic product is now identified and the therapeutic dose is determined.
The present grant application is critical in the translational path to patients and beyond to the market since it will support an innovative and proprietary development of GMP-compliant processes as well as the quality control testing of the therapeutic product to move forward: (i) to the clinic – in collaboration with Christian Hamel, MD, PhD, director of the team "Genetics and therapy of retinal and optic nerve
blindness" in the “Institut des Neurosciences de Montpellier”, and director of the center of reference for the inherited sensory diseases – and, (ii) to exploit it through the launching of a spin-off company.