Long-term pharmacologically regulated expression of erythropoietin in primates following AAV-mediated gene transfer.
ABSTRACT Gene therapy is a potential route for the delivery of secreted therapeutic proteins, but pharmacologic control of expression will generally be required for optimal safety and efficacy. Previous attempts to achieve regulated expression in large animal models have been thwarted by transient expression or immune responses to regulatory proteins. We evaluated the ability of the dimerizer-regulated gene expression system to achieve controlled, long-term production of erythropoietin (Epo) following intramuscular administration of adeno-associated virus (AAV) vectors to 16 primates. All animals showed dose-responsive and completely reversible elevation of Epo and hematocrit in response to the dimerizer rapamycin, or analogs with reduced immunosuppressive activity, administered intravenously or orally. Animals that received optimized dual vectors showed persistent regulated expression for the duration of the study, with no apparent immune response to Epo or the regulatory proteins. Similar results were obtained with single vectors incorporating both the Epo and regulatory genes, including those packaged into serotype 1 AAV vectors to allow use of lower viral doses. For the longest-studied animal, regulated expression has persisted for more than 6 years and 26 induction cycles. These data indicate that one-time or infrequent gene transfer followed by dimerizer regulation is a promising approach for delivery of therapeutic proteins.
Article: Increased erythropoiesis in mice injected with submicrogram quantities of pseudouridine-containing mRNA encoding erythropoietin.[show abstract] [hide abstract]
ABSTRACT: Advances in the optimization of in vitro-transcribed mRNA are bringing mRNA-mediated therapy closer to reality. In cultured cells, we recently achieved high levels of translation with high-performance liquid chromatography (HPLC)-purified, in vitro-transcribed mRNAs containing the modified nucleoside pseudouridine. Importantly, pseudouridine rendered the mRNA non-immunogenic. Here, using erythropoietin (EPO)-encoding mRNA complexed with TransIT-mRNA, we evaluated this new generation of mRNA in vivo. A single injection of 100 ng (0.005 mg/kg) mRNA elevated serum EPO levels in mice significantly by 6 hours and levels were maintained for 4 days. In comparison, mRNA containing uridine produced 10-100-fold lower levels of EPO lasting only 1 day. EPO translated from pseudouridine-mRNA was functional and caused a significant increase of both reticulocyte counts and hematocrits. As little as 10 ng mRNA doubled reticulocyte numbers. Weekly injection of 100 ng of EPO mRNA was sufficient to increase the hematocrit from 43 to 57%, which was maintained with continued treatment. Even when a large amount of pseudouridine-mRNA was injected, no inflammatory cytokines were detectable in plasma. Using macaques, we could also detect significantly-increased serum EPO levels following intraperitoneal injection of rhesus EPO mRNA. These results demonstrate that HPLC-purified, pseudouridine-containing mRNAs encoding therapeutic proteins have great potential for clinical applications.Molecular Therapy 02/2012; 20(5):948-53. · 6.87 Impact Factor
Article: Exon skipping and duchenne muscular dystrophy therapy: selection of the most active U1 snRNA antisense able to induce dystrophin exon 51 skipping.[show abstract] [hide abstract]
ABSTRACT: One promising approach for the gene therapy of Duchenne muscular dystrophy (DMD) is exon skipping. When thinking of possible intervention on human, it is very crucial to identify the most appropriate antisense sequences able to provide the highest possible skipping efficiency. In this article, we compared the exon 51 skipping activity of 10 different antisense molecules, raised against splice junctions and/or exonic splicing enhancers (ESEs), expressed as part of the U1 small nuclear RNA (snRNA). The effectiveness of each construct was tested in human DMD myoblasts carrying the deletion of exons 48-50, which can be treated with skipping of exon 51. Our results show that the highest skipping activity and dystrophin rescue is achieved upon expression of a U1 snRNA-derived antisense molecule targeting exon 51 splice sites in combination with an internal exon sequence. The efficacy of this molecule was further proven on an exon 45-50 deletion background, utilizing patient's fibroblasts transdifferentiated into myoblasts. In this system, we showed that the selected antisense was able to produce 50% skipping of exon 51.Molecular Therapy 09/2010; 18(9):1675-82. · 6.87 Impact Factor
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ABSTRACT: Adenovirus (Ad) based gene transfer vectors continue to be the platform of choice for an increasing number of clinical trials worldwide. In fact, within the last five years, the number of clinical trials that utilize Ad based vectors has doubled, indicating growing enthusiasm for the numerous positive characteristics of this gene transfer platform. For example, Ad vectors can be easily and relatively inexpensively produced to high titers in a cGMP compliant manner, can be stably stored and transported, and have a broad applicability for a wide range of clinical conditions, including both gene therapy and vaccine applications. Ad vector based gene transfer will become more useful as strategies to counteract innate and/or pre-existing adaptive immune responses to Ads are developed and confirmed to be efficacious. The approaches attempting to overcome these limitations can be divided into two broad categories: pre-emptive immune modulation of the host, and selective modification of the Ad vector itself. The first category of methods includes the use of immunosuppressive drugs or specific compounds to block important immune pathways, which are known to be induced by Ads. The second category comprises several innovative strategies inclusive of: (1) Ad-capsid-display of specific inhibitors or ligands; (2) covalent modifications of the entire Ad vector capsid moiety; (3) the use of tissue specific promoters and local administration routes; (4) the use of genome modified Ads; and (5) the development of chimeric or alternative serotype Ads. This review article will focus on both the promise and the limitations of each of these immune evasion strategies, and in the process delineate future directions in developing safer and more efficacious Ad-based gene transfer strategies.Viruses 09/2010; 2(9):2013-36. · 1.50 Impact Factor