title: Preclinical potency and safety studies of an AAV2-mediated gene therapy vector for the treatment of MERTK associated retinitis pigmentosa.
abstract: Abstract Proof of concept for MERTK gene replacement therapy has been demonstrated using different viral vectors in the Royal College of Surgeon (RCS) rat, a well characterized model of recessive retinitis pigmentosa that contains a mutation in the Mertk gene. MERTK plays a key role in renewal of photoreceptor outer segments (OS) by phagocytosis of shed OS tips. Mutations in MERTK cause impaired phagocytic activity and accumulation of OS debris in the interphotoreceptor space that ultimately leads to photoreceptor cell death. In the present study, we conducted a series of preclinical potency and GLP-compliant safety evaluations of an adeno-associated virus type 2 (AAV2) vector expressing human MERTK cDNA driven by the retinal pigment epithelium-specific, VMD2 promoter. We demonstrate the potency of the vector in RCS rats by improved electroretinogram (ERG) responses in treated eyes compared with contralateral untreated controls. Toxicology and biodistribution studies were performed in Sprague-Dawley (SD) rats injected with two different doses of AAV vectors and buffer control. Delivery of vector in SD rats did not result in a change in ERG amplitudes of rod and cone responses relative to balanced salt solution control-injected eyes, indicating that administration of AAV vector did not adversely affect normal retinal function. In vivo fundoscopic analysis and postmortem retinal morphology of the vector-injected eyes were normal compared with controls. Evaluation of blood smears showed the lack of transformed cells in the treated eyes. All injected eyes and day 1 blood samples were positive for vector genomes, and all peripheral tissues were negative. Our results demonstrate the potency and safety of the AAV2-VMD2-hMERTK vector in animal models tested. A GMP vector has been manufactured and is presently in clinical trial.
authors.affiliation: Powell Gene Therapy Center, Department of Pediatrics, University of Florida, Gainesville, FL 32610, USA. conlon@peds.ufl.edu
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Conlon
authors.forename: Wen-Tao
authors.initials: WT
authors.lastname: Deng
authors.forename: Kirsten
authors.initials: K
authors.lastname: Erger
authors.forename: Travis
authors.initials: T
authors.lastname: Cossette
authors.forename: Ji-jing
authors.initials: JJ
authors.lastname: Pang
authors.forename: Renee
authors.initials: R
authors.lastname: Ryals
authors.forename: Nathalie
authors.initials: N
authors.lastname: Clément
authors.forename: Brian
authors.initials: B
authors.lastname: Cleaver
authors.forename: Issam
authors.initials: I
authors.lastname: McDoom
authors.forename: Shannon E
authors.initials: SE
authors.lastname: Boye
authors.forename: Marc C
authors.initials: MC
authors.lastname: Peden
authors.forename: Mark B
authors.initials: MB
authors.lastname: Sherwood
authors.forename: Corinne R
authors.initials: CR
authors.lastname: Abernathy
authors.forename: Fowzan S
authors.initials: FS
authors.lastname: Alkuraya
authors.forename: Sanford L
authors.initials: SL
authors.lastname: Boye
authors.forename: William W
authors.initials: WW
authors.lastname: Hauswirth
mesh_terms: D000818:Animals; D000075002:Bestrophins; D018118:Chloride Channels / Q000235:genetics; D000229:Dependovirus / Q000235:genetics*; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D005136:Eye Proteins / Q000235:genetics; D005260:Female; D015316:Genetic Therapy; D005822:Genetic Vectors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D012160:Retina / Q000473:pathology; D012174:Retinitis Pigmentosa / Q000473:pathology / Q000628:therapy*; D014018:Tissue Distribution; D000076202:c-Mer Tyrosine Kinase
chemical_list: C113133:BEST1 protein, human; D000075002:Bestrophins; D018118:Chloride Channels; D005136:Eye Proteins; D011518:Proto-Oncogene Proteins; C097072:MERTK protein, human; D020794:Receptor Protein-Tyrosine Kinases; D000076202:c-Mer Tyrosine Kinase