Safety and biodistribution of an equine infectious anemia virus-based gene therapy, RetinoStat(®), for age-related macular degeneration.

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.

A stable producer cell line for the manufacture of a lentiviral vector for gene therapy of Parkinson's disease.

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.

Comparison of HIV- and EIAV-based vectors on their efficiency in transducing murine and human hematopoietic repopulating cells.

The use of lentiviral vectors for gene transfer into hematopoietic stem cells has raised considerable interest as these vectors can permanently integrate their genome into quiescent cells. Vectors based on alternative lentiviruses would theoretically be safer than HIV-1-based vectors and could also be used in HIV-positive patients, minimizing the risk of generating replication-competent virus. Here we report the use of third-generation equine infectious anemia virus (EIAV)- and HIV-1-based vectors with minimal viral sequences and absence of accessory proteins. We have compared their efficiency in transducing mouse and human hematopoietic stem cells both in vitro and in vivo to that of a previously documented second-generation HIV-1 vector. The third-generation EIAV- and HIV-based vectors gave comparable levels of transduction and transgene expression in both mouse and human NOD/SCID repopulating cells but were less efficient than the second-generation HIV-1 vector in human HSCs. For the EIAV vector this is possibly a reflection of the lower protein expression levels achieved in human cells, as vector copy number analysis revealed that this vector exhibited a trend to integrate equally efficiently compared to the third-generation HIV-1 vector in both mouse and human HSCs. Interestingly, the presence or absence of Tat in viral preparations did not influence the transduction efficiency of HIV-1 vectors in human HSCs.