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Usher syndrome type 1B is a combined deaf-blindness condition caused by mutations in the MYO7A gene. Loss of functional myosin VIIa in the retinal pigment epithelia (RPE) and/or photoreceptors leads to blindness. We evaluated the impact of subretinally delivered UshStat, a recombinant EIAV-based lentiviral vector expressing human MYO7A, on photoreceptor function in the shaker1 mouse model for Usher type 1B that lacks a functional Myo7A gene. Subretinal injections of EIAV-CMV-GFP, EIAV-RK-GFP (photoreceptor specific), EIAV-CMV-MYO7A (UshStat) or EIAV-CMV-Null (control) vectors were performed in shaker1 mice. GFP and myosin VIIa expression was evaluated histologically. Photoreceptor function in EIAV-CMV-MYO7A treated eyes was determined by evaluating α-transducin translocation in photoreceptors in response to low light intensity levels, and protection from light induced photoreceptor degeneration was measured. The safety and tolerability of subretinally delivered UshStat was evaluated in macaques. Expression of GFP and myosin VIIa was confirmed in the RPE and photoreceptors in shaker1 mice following subretinal delivery of the EIAV-CMV-GFP/MYO7A vectors. The EIAV-CMV-MYO7A vector protected the shaker1 mouse photoreceptors from acute and chronic intensity light damage, indicated by a significant reduction in photoreceptor cell loss, and restoration of the α-transducin translocation threshold in the photoreceptors. Safety studies in the macaques demonstrated that subretinal delivery of UshStat is safe and well-tolerated. Subretinal delivery of EIAV-CMV-MYO7A (UshStat) rescues photoreceptor phenotypes in the shaker1 mouse. In addition, subretinally delivered UshStat is safe and well-tolerated in macaque safety studies These data support the clinical development of UshStat to treat Usher type 1B syndrome. [ABSTRACT FROM AUTHOR]

Purpose: StarGen is an equine infectious anemia virus (EIAV)-based lentiviral vector that expresses the photoreceptor-specific adenosine triphosphate (ATP)-binding cassette transporter (ABCA4) protein that is mutated in Stargardt disease (STGD1), a juvenile macular dystrophy. EIAV vectors are able to efficiently transduce rod and cone photoreceptors in addition to retinal pigment epithelium in the adult macaque and rabbit retina following subretinal delivery. The safety and biodistribution of StarGen following subretinal delivery in macaques and rabbits was assessed., Methods: Regular ophthalmic examinations, IOP measurements, ERG responses, and histopathology were carried out in both species to compare control and vector-treated eyes. Tissue and fluid samples were obtained to evaluate the persistence, biodistribution, and shedding of the vector following subretinal delivery., Results: Ophthalmic examinations revealed a slightly higher level of inflammation in StarGen compared with control treated eyes in both species. However, inflammation was transient and no overt toxicity was observed in StarGen treated eyes and there were no abnormal clinical findings. There was no StarGen-associated rise in IOP or abnormal ERG response in either rabbits or macaques. Histopathologic examination of the eyes did not reveal any detrimental changes resulting from subretinal administration of StarGen. Although antibodies to StarGen vector components were detected in rabbit but not macaque serum, this immunologic response did not result in any long-term toxicity. Biodistribution analysis demonstrated that the StarGen vector was restricted to the ocular compartment., Conclusions: In summary, these studies demonstrate StarGen to be well tolerated and localized following subretinal administration.

RetinoStat(®) is an equine infectious anemia virus-based lentiviral gene therapy vector that expresses the angiostatic proteins endostatin and angiostatin that is delivered via a subretinal injection for the treatment of the wet form of age-related macular degeneration. We initiated 6-month safety and biodistribution studies in two species; rhesus macaques and Dutch belted rabbits. After subretinal administration of RetinoStat the level of human endostatin and angiostatin proteins in the vitreous of treated rabbit eyes peaked at ∼1 month after dosing and remained elevated for the duration of the study. Regular ocular examinations revealed a mild to moderate transient ocular inflammation that resolved within 1 month of dosing in both species. There were no significant long-term changes in the electroretinograms or intraocular pressure measurements in either rabbits or macaques postdosing compared with the baseline reading in RetinoStat-treated eyes. Histological evaluation did not reveal any structural changes in the eye although there was an infiltration of mononuclear cells in the vitreous, retina, and choroid. No antibodies to any of the RetinoStat vector components or the transgenes could be detected in the serum from either species, and biodistribution analysis demonstrated that the RetinoStat vector was maintained within the ocular compartment. In summary, these studies found RetinoStat to be well tolerated, localized, and capable of persistent expression after subretinal delivery.

ProSavin is an equine infectious anemia virus vector-based gene therapy for Parkinson's disease for which inducible HEK293T-based producer cell lines (PCLs) have been developed. These cell lines demonstrate stringent tetracycline-regulated expression of the packaging components and yield titers comparable to the established transient production system. A prerequisite for the use of PCL-derived lentiviral vectors (LVs) in clinical applications is the thorough characterization of both the LV and respective PCL with regard to identity and genetic stability. We describe the detailed characterization of two ProSavin PCLs (PS5.8 and PS46.2) and resultant ProSavin vector. The two cell lines demonstrate stable production of vector over a time period sufficient to allow generation of master and working cell banks, and subsequent large-scale vector production. ProSavin generated from the PCLs performs comparably in vivo to that produced by the standard transient transfection process with respect to transduction efficiency and immunogenicity. The development of ProSavin PCLs, and the detailed characterization described here, will aid the advancement of ProSavin for clinical application.

The attenuated vaccinia virus MVA has been engineered to deliver the tumor antigen 5T4 (MVA-5T4; TroVax), a surface glycoprotein expressed by most solid tumors. MVA-5T4 has been tested in 2 phase I/II and 7 phase II clinical trials in colorectal (4 trials), renal (4 trials), and prostate (1 trial) advanced cancer patients. Data have been collated from all 9 studies and used to investigate the magnitude and kinetics of 5T4-specific antibody responses after vaccination and to identify potential associations between the immune response and patient survival. Antibody responses specific for the 5T4 tumor antigen and the MVA viral vector were quantified in plasma samples taken from cancer patients before and after the treatment with MVA-5T4. Immunologic and survival data were analyzed using proportional hazards regression adjusting for age and gender. Both survival and immunologic response data were available for 189 patients with colorectal (n=73), renal (n=89), and prostate (n=27) cancer. Before the treatment with MVA-5T4, 5T4-specific antibody levels were significantly elevated in cancer patients compared with healthy donors. After MVA-5T4 administration, 5T4-specific antibody responses increased significantly and peaked after 3 to 4 vaccinations. Exploratory analyses showed significant associations between 5T4 antibody responses and overall survival across all 9 trials and in patients with colorectal cancer. The 5T4-specific antibodies were present at higher levels in cancer patients compared with healthy donors and increased significantly after treatment with MVA-5T4. Although the studies were uncontrolled, there were encouraging signs of activity which is associated with the magnitude of 5T4-specific antibody responses.